Patent Application
20170021004
All references cited herein are incorporated by reference herein in their entirety.
The present invention relates generally to immunogenic (including immunoprotective) Leptospira spp. proteins, which are capable of eliciting broad protective immune responses in animals, particularly canine animals. The invention further relates to methods of providing animals, especially canine animals in need of protection thereof, with broad protective immune responses against multiple Leptospira spp.
Leptospira are spirochete bacteria classified into saprophytic intermediary or pathogenic species inhabiting soil and fresh water reservoirs, predominately in regions of the world with tropical climates (1). Pathogenic species can be transmitted to wild and domesticated animals and to humans through direct or indirect contact with an abraded epidermal lining. Disease manifests as leptospirosis in susceptible hosts with symptoms ranging from a mild febrile illness to fatal kidney, liver or respiratory failure. Asymptomatic hosts include, mice, rats, raccoons and others and in these animals the bacteria colonize the renal tubules resulting in expulsion of the bacteria back into the environment, in the urine. Pathogenic Leptospira can survive for long periods in water (2, 3), providing an opportunity for the bacteria to infect a new host.
Leptospira resemble the hallmarks of Gram negative bacteria in that they contain an inner membrane, a periplasmic space with peptidoglycan and an outer membrane where the lipopolysaccharide is anchored. However, the bacteria are referred to as “Gram negative-like” because unlike other Gram negative bacteria the peptidoglycan is associated with cytoplasmic membrane (4) and not the outer membrane. The components of the envelope of Leptospira have been extensively characterized in previous studies, including the protein compositions of the cytoplasmic and outer membranes. However, protein transport from the cytoplasm to the extracellular space and therefore secretion systems have not been experimentally characterized in Leptospira.
Leptospira have the ability to rapidly disseminate in targets organs (kidneys and liver) where they are generally observed in the interstitial space (8, 9) but they have also been demonstrated to transiently exist intracellular in macrophages (10-12). During both extracellular and intracellular survival, Leptospira likely utilize various outer membrane and extracellular proteins to remain viable during infection. It follows that numerous studies have focused on identification (13-18) and characterization (19-32) of outer membrane proteins and a few studies have begun to characterize extracellular proteins in Leptospira. Previous studies focusing on Leptospiral extracellular proteins have combined to identify a hemolysin (33), an immunoglobulin-like protein (LigA) (34) and a sphingomyelinase (Sph2) (23). On a global scale, one proteomic study has identified Leptospira interrogans proteins in culture supernatants (35) while another study utilized a bioinformatics approach to identify potential outer membrane and extracellular proteins (15). It has also been demonstrated that culture supernatants of Leptospira contain proteases which can interfere with host complement defense against Leptospira (36), that an extracellular enolase interacts with host plasminogen (37) and that an extracellular collagenase can degrade host collagen (38). Lastly, comparison of the transcriptomes of a Leptospira mutant inactivated in a putative regulatory locus (lb139) versus the parent wild type (wt) strain revealed, amongst others, reduced transcript levels of 20 genes which encoded extracellular proteins, in the mutant strain (39) and this mutant displayed virulence attenuation in hamsters. Combined, these studies implicated extracellular proteins in the Leptospiral infection process.
Current vaccines against Leptospira primarily consist of inactivated bacterin preparations, which induce a largely humoral immune response, and are primarly serovar-specific (“Leptospirosis Fact Sheet,” WHO, Regional Office for South-East Asia, 2009). Further, the Novibac (Merck Animal Health) label claim indicates that there is little if any evidence for cross-protection. The observed lack of cross-protection is not surprising, particularly in view of the significant genetic/genomic differences among, for example, the gene organization in the lipopolysaccharide biosynthetic (rfb) locus (Pena-Moctezuma, A. et al., 2001 FEMS Immunology and Medical Microbiology 31 (2001) 73-81). Leptospira lipopolysaccharides are thus serovar-specific, and as antigenic epitopes, tend to elicit T-cell-independent immune responses. As such, the current strategy for achieving broad protection against different Leptospira serovar(s) has been to include many different inactivated Leptospira serovar(s) in a vaccine formulation. This approach has significant draw backs, including the need to grow multiple different serovars to achieve complete protection and an increasing potential for interference with other Leptospira serovars or other vaccine components.
Accordingly, it would be useful to provide simplified compositions, perhaps containing only one or more conserved immunogenic proteins, for eliciting broad immunoprotective responses against multiple Leptospira serovar(s). It would be further useful to provide Leptospira vaccine compositions that activate both humoral and cellular immune responses, to provide vaccinates with broader and longer lasting protection against subsequent exposure to Leptospira. Until the instant disclosure, methods for providing such protection against multiple Leptospira serovar(s) using one or more conserved immunoprotective proteins was not known.
It is thus an object of this disclosure is to provide a rational, high throughput method for identifying immunoprotective Leptospira spp. proteins, which are broadly protective against at least two virulent serovars of Leptospira. In a particular embodiment, broad protection is provided by cross-serovar conserved surface proteins, which may not be expressed during the normal culture conditions present during typical lepto bacterin vaccine manufacturing. In another particular embodiment, the broad protection includes both a humoral and cellular immune response.
In an embodiment, the method for identifying immunoprotective Leptospira spp. proteins comprises the steps of:
(a) identifying likely membrane-localizing genes, which are conserved between pathogenic Leptospira serovars;
(b) identifying conserved Leptospira membrane proteins that are expressed in vivo or in vivo-like conditions; and
(c) correlating the results of the genetic (a) and protein (b) studies to identify pan-protective Leptospira proteins; thereby identifying the immunoprotective Leptospira spp. proteins, which may be used in formulating broadly immunoprotective Leptospira vaccines.
In an embodiment of the identification method, analyses may be carried out using any of the following or equivalents or superiors thereof: CLC Genomics Workbench and Genostar Suite 4.0 (for assembly annotation); Wallgene gneostar 1.3.1.2 (for comparative genomics); and SignalP, LipoP, SpLip, TMHMM and MCMBB (for prediction of membrane localization).
In a particular embodiment, an overview of the method and results are presented in
In another embodiment of the identification method, outer membrane proteins may be extracted (e.g. by routine triton or proteinase K methods) and then identified by LC-MS-MS. Peptide sequences may then be aligned against any suitable Leptospira (or more general) protein database.
A further object of this disclosure is to provide broadly immunoprotective Leptospira spp. proteins, which are suitable for use in single and multi-valent vaccine formulations.
Another object of this disclosure is to provide immunoprotective compositions comprising the immunoprotective Leptospira spp. proteins.
Yet another object of this disclosure is to provide methods for eliciting safe and protective immune response, in an animal in need thereof, against multiple Leptospira spp., comprising the step of administering at least one immunoprotective Leptospira spp. protein according to the instant disclosure to animals in need of protection against the multiple Leptospira spp.
In an embodiment, the immunoprotective proteins or compositions comprising or consisting essentially of, or consisting of at least one or more immunogenic (including Immunoprotective) Leptospira spp. proteins elicits protection against subsequent experimental or natural challenge by virulent Leptospira canicola, Leptospira grippotyphosa, Leptospira icterohaemorrhagiae, Leptospira pomona Leptospira bratislava and any other Leptospira serovars known now, or future determined, to cause disease or illness in animals, including human animals
In an embodiment, the broadly protective immunogenic composition may comprise, consist essentially of, or consist of at least one live attenuated Leptospira spp., at least one subunit (e.g. a peptide, protein, or immunoprotective portion thereof), at least one bacterin enriched in surface antigens, or any combination of the preceding.
In another embodiment, the immunoprotective proteins are surface antigens that are relatively more highly expressed in vivo, but relatively less expressed in vitro. As used herein, “in vivo” means the Leptospira spp., for example, the pathogenic Leptospira spp., is growing and/or infecting an animal host. As used herein, “in vitro” means the Leptospira spp. is growing in the context of routine culture conditions, for example, those used to manufacture Leptospira spp. for use in bacterin-based vaccines.
Until this disclosure, no one had appreciated this possibility, nor conceived of the disclosed methods for exploiting this phenomenon to generate a broadly effective Leptospira vaccine.
Accordingly, another object of the invention is to provide methods for culturing Leptospira spp. that mimics in vivo conditions. This method may facilitate the identification of broadly immunoprotective Leptospira spp. proteins because it allows relatively higher expression of such proteins relative to when the Leptospira spp. are grown under traditional manufacturing or in vitro conditions.
In a particular embodiment of the in vivo culturing method, Leptospira spp. may be grown in conditions that mimic the in vivo conditions, including relatively higher osmolarity, relatively higher temperature and relatively lower levels of iron (e.g. by chelation). In an embodiment, L. interrogans australis strain 700 may be grown under three conditions: 1) EMJH at 29° C. (in vitro control culture); 2) add to #1 40 μM bipyridil and 120 mM NaCl (in vivo-like conditions); and 3) two or more passages in hamster liver and spleen (actual in vivo conditions).
Surprisingly, when the osmolarity and temperature were raised as disclosed herein, the expression of cross-immunoprotective proteins increased significantly relative to their expression levels in standard culture conditions (see Table 1 below). Development and exploitation of this inventive method has allowed Applicants to produce heretofore unknown vaccine compositions, which are highly safe and effective in eliciting in an animal in need thereof protective immunity against at least two pathogenic Leptospira spp.
Leptospira antigens induced by passage, or increasing osmolarity or iron chelation
Leptospira spp. proteins common to both screens outlined in Examples
These and other embodiments are disclosed or are obvious from and encompassed by, the following Detailed Description.
A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, wherein:
In an embodiment, the method for identifying immunoprotective Leptospira spp. proteins comprises the steps of:
(a) identifying likely membrane-localizing genes, which are conserved between pathogenic Leptospira serovars;
(b) identifying conserved Leptospira membrane proteins that are expressed in vivo or in vivo-like conditions; and
(c) correlating the results of the genetic (a) and protein (b) studies to identify pan-protective Leptospira proteins; thereby identifying the immunoprotective Leptospira spp. proteins, which may be used in formulating broadly immunoprotective Leptospira vaccines.
In an embodiment of the identification method, analyses may be carried out using any of the following or equivalents or superiors thereof: CLC Genomics Workbench and Genostar Suite 4.0 (for assembly annotation); Wallgene Genostar 1.3.1.2 (for comparative genomics); and SignalP, LipoP, SpLip, TMHMM and MCMBB (for prediction of membrane localization).
In a particular embodiment, an overview of the method and results are presented in
In an embodiment, the disclosure provides a composition for providing to an animal in need thereof protective immunity against at least one Leptospira spp., comprising at least one Leptospira polypeptide having at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5% identity to LIC13074p, LIC13050p, LIC13314p, LIC10117p, LIC10879p, LIC10879p, LIC13050p, LIC10411p, LIC13314p, LIC10117p, LIC11088p, LIC11089p, LIC13074p, LIC20229p, LIC11181p, LIC13059p, LIC10959p, LIC11289p, LIC12349p, LIC13250p, LIC20146p, LIC10321p, LIC10662p, LIC11183p, LIC11489p, LIC12258p, LIC12731p, LIC12332p, LIC10793p, LIC11884p, LIC20197p, LIC11224p, LIC11693p, LIC12285p, LIC10672p, LIC10509p, LIC10596p, LIC11028p, LIC11874p, LIC13090p, LIC10318p, LIC10655p, LIC11553p, LIC11637p, LIC12100p, LIC12784p, LIC13002p, LIC13023p, LIC13017p, LIC11711p, LIC10380p, LIC10551p, LIC10740p, LIC11580p, LIC11990p, LIC12339p, LIC12691p, LIC12805p, LIC13195p, LIC13313p, LIC13386p, LIC13491p, LIC20165p, LIC10314p, LIC10326p, LIC10927p, LIC10968p, LIC11003p, LIC12576p, LIC13434p, LIC13071p, LIC11224p, LIC10027p, LIC10474p, LIC10411p, LIC20035p, LIC20197p, LIC11088p, LIC11687p, LIC11711p, LIC10115p, LIC12433p, LIC10868p, LIC10898p, LIC11299p, LIC11693p, LIC12030p, LIC20153p, LIC10672p, LIC11966p, LIC10973p, Lp1118p, MceIIp, Lsa21p or combinations thereof or effective immunological equivalent portions thereof. By “immunological equivalent portions,” it is intended that the portion is capable of eliciting a statistically similar or better safe and effective immune response, relative to the larger polypeptide sequence from which the portion was taken. As such, if a composition comprising LIC13074p protects 80% of vaccinated animals with protection from subsequent virulent challenge, and a given truncation of LIC13074p protects 82% of vaccinated animals, then the truncation is an “immunologically equivalent portion” of LIC
In another embodiment, the composition for providing protective immunity against Leptospira, or diseases caused by Leptospira, comprises at least one Leptospira polypeptide having at least 80% identity to LIC11089p, LIC10973p, LIC10318p, combinations thereof or immunological equivalent portions thereof. In other embodiments, the Leptospira polypeptide has at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identity to LIC11089p, LIC10973p or LIC10318p.
In yet another embodiment, the composition comprises a polypeptide encoded by a nucleic acid sequence having at least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identity to one of the sequences as set forth in any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 or 163.
In another embodiment, the nucleic acid sequence has at least 98% identity to one of the sequences as set forth in any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 or 163.
In another embodiment, the nucleic acid sequence has 100% identity to one of the sequences as set forth in any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 or 163.
In another embodiment, the nucleic acid sequence is as set forth in any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 or 163.
In another aspect, the disclosure provides a method for providing to an animal in need thereof protective immunity against one or more pathogenic or virulent Leptospira spp., comprising administering to an animal a vaccine comprising an immunoprotective effective amount of a Leptospira spp. polypeptide selected from, or having at least 80% identity to, a polypeptide having the sequence set forth in SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162 or 164.
In an embodiment, the method of providing protective immunity comprises the steps of administering to an animal a vaccine comprising an immunoprotective effective amount of a polypeptide selected from, or having at least 80% identity to, a polypeptide having the sequence set forth in SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162 or 164.
In another aspect, the disclosure provides a vector capable of expressing a recombinant DNA, wherein the recombinant DNA is selected from any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 and 163.; or wherein the recombinant DNA is at least 75%, 80%, 85%, 90%, 95% or 98% homologous to the sequences as set forth in any one of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 and 163.
In yet another aspect, the disclosure provided a recombinant DNA vaccine comprising:
(a) a recombinant DNA wherein the recombinant DNA comprises one or more of the sequences as set forth in SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 and 163; and
(b) a vector capable of expressing the recombinant DNA when the recombinant DNA is inserted into the vector, wherein the recombinant DNA is inserted into the vector such that a recombinant protein is expressed when the vector is provided in an appropriate host.
The disclosure also provides a method for producing a vaccine against a Leptospira-related disorder comprising the steps of:
(a) providing a recombinant DNA, wherein the recombinant DNA comprises any one or more of the sequences as set forth in SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161 and 163;
(b) providing a vector capable of expressing the recombinant DNA when the recombinant DNA is inserted into the vector; and
(c) inserting the recombinant DNA into the vector, wherein the recombinant DNA is inserted into the vector such that a recombinant protein is expressed when the vector is provided in an appropriate host, thereby producing the vaccine.
The disclosure further provides a method for producing an immunoprotective peptide for use in a vaccine against a Leptospira-related disorder comprising:
(a) providing a recombinant DNA, wherein the recombinant DNA is selected from:
(b) providing a vector capable of expressing the recombinant DNA when the recombinant DNA is inserted into the vector;
(c) inserting the recombinant DNA into the vector;
(d) providing a bacterial strain;
(e) transforming the vector into the bacterial strain such that a recombinant protein is expressed when the vector is transformed into the bacterial strain; and
(f) harvesting the recombinant protein from the bacterial strain, thereby producing the immunoprotective protein.
In an embodiment of the method, the animal is protected against Leptospira icterohaemorrhagiae, Leptospira canicola, Leptospira grippotyphosa, Leptospira australis, Leptospira bratislava and Leptospira pomona. In an embodiment, the animal may be administered about 1 ml of vaccine. The vaccine may also be administered as two subcutaneous doses, for example, at 21-day intervals. In an example, the animal is a canine, and the vaccine may comprise additional antigens that provide immunity against additional canine pathogens. The additional antigens may be selected from canine parvovirus (CPV), canine parainfluenza virus (CPi2), canine distemper virus (CDV), adenovirus, herpesvirus, rabies, canine coronavirus, and combinations thereof.
In still another aspect, the disclosure provides a T-cell epitope vaccine comprising a recombinant protein, wherein the recombinant protein comprises a T-cell epitope, and wherein the T-cell epitope comprises at least one polypeptide sequence having at least 80% identity to at least one polypeptide having the sequence set forth in SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162 or 164.
In an embodiment of the T-cell epitope vaccine, the polypeptide sequence comprises one or more of the sequences as set forth in SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162 or 164. In a particular embodiment, the vaccine comprises a polypeptide having the sequence as set forth in SEQ ID NO: 2, 4, 6, 8, 10, 42 (LIC11089), 68 (LIC10973) or 122 (LIC10318).
In some embodiments, the polypeptide has the sequence set forth in SEQ 42, 68 or 122.
By “antigen” or “immunogen” means a substance that induces a specific immune response in a host animal. The antigen may comprise a whole organism, killed, attenuated or live; a subunit or portion of an organism; a recombinant vector containing an insert with immunogenic properties; a piece or fragment of DNA capable of inducing an immune response upon presentation to a host animal; a polypeptide, an epitope, a hapten, or any combination thereof. Alternately, the immunogen or antigen may comprise a toxin or antitoxin.
The terms “protein”, “peptide”, “polypeptide” and “polypeptide fragment” are used interchangeably herein to refer to polymers of amino acid residues of any length. The polymer can be linear or branched, it may comprise modified amino acids or amino acid analogs, and it may be interrupted by chemical moieties other than amino acids. The terms also encompass an amino acid polymer that has been modified naturally or by intervention; for example disulfide bond formation, glycosylation, lipidation, acetylation, phosphorylation, or any other manipulation or modification, such as conjugation with a labeling or bioactive component.
The term “immunogenic or antigenic polypeptide” as used herein includes polypeptides that are immunologically active in the sense that once administered to the host, it is able to evoke an immune response of the humoral and/or cellular type directed against the protein. Preferably the protein fragment is such that it has substantially the same immunological activity as the total protein. Thus, a protein fragment according to the invention comprises or consists essentially of or consists of at least one epitope or antigenic determinant. An “immunogenic” protein or polypeptide, as used herein, includes the full-length sequence of the protein, analogs thereof, or immunogenic fragments thereof. By “immunogenic fragment” is meant a fragment of a protein which includes one or more epitopes and thus elicits the immunological response described above. Such fragments can be identified using any number of epitope mapping techniques, well known in the art. See, e.g., Epitope Mapping Protocols in Methods in Molecular Biology, Vol. 66 (Glenn E. Morris, Ed., 1996). For example, linear epitopes may be determined by e.g., concurrently synthesizing large numbers of peptides on solid supports, the peptides corresponding to portions of the protein molecule, and reacting the peptides with antibodies while the peptides are still attached to the supports. Such techniques are known in the art and described in, e.g., U.S. Pat. No. 4,708,871; Geysen et al., 1984; Geysen et al., 1986. Similarly, conformational epitopes are readily identified by determining spatial conformation of amino acids such as by, e.g., x-ray crystallography and 2-dimensional nuclear magnetic resonance. See, e.g., Epitope Mapping Protocols, supra. Methods especially applicable to the proteins of T. parva are fully described in PCT/US2004/022605 incorporated herein by reference in its entirety.
As discussed herein, the invention encompasses active fragments and variants of the antigenic polypeptide. Thus, the term “immunogenic or antigenic polypeptide” further contemplates deletions, additions and substitutions to the sequence, so long as the polypeptide functions to produce an immunological response as defined herein. The term “conservative variation” denotes the replacement of an amino acid residue by another biologically similar residue, or the replacement of a nucleotide in a nucleic acid sequence such that the encoded amino acid residue does not change or is another biologically similar residue. In this regard, particularly preferred substitutions will generally be conservative in nature, i.e., those substitutions that take place within a family of amino acids. For example, amino acids are generally divided into four families: (1) acidic—aspartate and glutamate; (2) basic—lysine, arginine, histidine; (3) non-polar—alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan; and (4) uncharged polar—glycine, asparagine, glutamine, cystine, serine, threonine, tyrosine. Phenylalanine, tryptophan, and tyrosine are sometimes classified as aromatic amino acids. Examples of conservative variations include the substitution of one hydrophobic residue such as isoleucine, valine, leucine or methionine for another hydrophobic residue, or the substitution of one polar residue for another polar residue, such as the substitution of arginine for lysine, glutamic acid for aspartic acid, or glutamine for asparagine, and the like; or a similar conservative replacement of an amino acid with a structurally related amino acid that will not have a major effect on the biological activity. Proteins having substantially the same amino acid sequence as the reference molecule but possessing minor amino acid substitutions that do not substantially affect the immunogenicity of the protein are, therefore, within the definition of the reference polypeptide. All of the polypeptides produced by these modifications are included herein. The term “conservative variation” also includes the use of a substituted amino acid in place of an unsubstituted parent amino acid provided that antibodies raised to the substituted polypeptide also immunoreact with the unsubstituted polypeptide.
The term “epitope” refers to the site on an antigen or hapten to which specific B cells and/or T cells respond. The term is also used interchangeably with “antigenic determinant” or “antigenic determinant site”. Antibodies that recognize the same epitope can be identified in a simple immunoassay showing the ability of one antibody to block the binding of another antibody to a target antigen.
An “immunological response” to a composition or vaccine is the development in the host of a cellular and/or antibody-mediated immune response to a composition or vaccine of interest. Usually, an “immunological response” includes but is not limited to one or more of the following effects: the production of antibodies, B cells, helper T cells, and/or cytotoxic T cells, directed specifically to an antigen or antigens included in the composition or vaccine of interest. Preferably, the host will display either a therapeutic or protective immunological response such that resistance to new infection will be enhanced and/or the clinical severity of the disease reduced. Such protection will be demonstrated by either a reduction or lack of symptoms and/or clinical disease signs normally displayed by an infected host, a quicker recovery time and/or a lowered viral titer in the infected host.
By “animal” is intended mammals, birds, and the like. Animal or host as used herein includes mammals and human. The animal may be selected from the group consisting of equine (e.g., horse), canine (e.g., dogs, wolves, foxes, coyotes, jackals), feline (e.g., lions, tigers, domestic cats, wild cats, other big cats, and other felines including cheetahs and lynx), ovine (e.g., sheep), bovine (e.g., cattle), porcine (e.g., pig), avian (e.g., chicken, duck, goose, turkey, quail, pheasant, parrot, finches, hawk, crow, ostrich, emu and cassowary), primate (e.g., prosimian, tarsier, monkey, gibbon, ape), ferrets, seals, and fish. The term “animal” also includes an individual animal in all stages of development, including newborn, embryonic and fetal stages.
Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The singular terms “a”, “an”, and “the” include plural referents unless context clearly indicates otherwise. Similarly, the word “or” is intended to include “and” unless the context clearly indicate otherwise.
It is noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention.
The invention will now be further described by way of the following non-limiting examples.
Leptospira spp. were subjected to culture conditions that mimic the in vivo conditions, including relatively higher osmolarity, relatively higher temperature and relatively lower levels of iron (e.g. by chelation). Briefly, L. interrogans australis strain 700 was be grown under three conditions: 1) EMJH at 29° C. (in vitro control culture); 2) add to #1 40 μM bipyridil and 120 mM NaCl (in vivo-like conditions); and 3) two or more passages in hamster liver and spleen (actual in vivo conditions).
When the osmolarity and temperature were raised as disclosed herein, the expression of cross-immunoprotective proteins increased significantly relative to their expression levels in standard culture conditions (see Table 1 above). Development and exploitation of this inventive method has allowed Applicants to produce heretofore unknown vaccine compositions, which are highly safe and effective in eliciting in an animal in need thereof protective immunity against at least two pathogenic Leptospira spp.
Leptospira are spirochete bacteria capable of saprophytic and pathogenic lifestyles. These zoonotic bacteria have a worldwide prevalence and pathogenesis manifests in the disease known as leptospirosis. The aim in this study was to gain a global understanding of the composition of the Leptospira exoproteome and to elucidate how these proteins contribute to the saprophytic and pathogenic life cycle of these bacteria. Leptospiral exoproteins were quantified under various in vitro Leptospira culture conditions mimicking infection using normalized spectral index quantitative proteomics. About 208 exoproteins were identified, having equal or higher quantities in culture supernatants when compared to cellular quantities. Culture conditions demonstrated that 52 of these proteins were regulated in response to temperature while 69 were regulated in response to osmotic changes, with the majority displaying lowered abundances. Exoproteins were mainly classified into clusters of orthologous groups encompassing metabolism and energy production, suggesting that exoproteins likely serve essential functions for Leptospira viability. Proteins associated with virulence (factors causing tissue damage and cytotoxicity) were underrepresented.
In accordance, disruption of two exoprotein encoding genes resulted in significant growth defects in vitro, while disruption of six other exoprotein encoding genes neither affected in vitro growth rates nor disease manifestation in the animal infection model. These observations suggest that Leptospira genomes contain exoprotein encoding genes with redundant functions, the majority of which seem to be dedicated to heterotrophic processes with potential secondary functioning in disease pathogenesis.
Leptospira interrogans serovar Manilae strain L495 was culture maintained in EMJH medium (44, 45) at 30° C. Leptospira transposon mutagenesis has previously been described (46-48) and L495 transposon mutants used in this study were obtained from an in house maintained library of mutants. The mutant strains were culture maintained as described above for the parent strain. To perform proteomic analysis on culture supernatants EMJH was constituted with the following modifications. Albumin was omitted from the recipe and Tween 80 and glycerol were added to 0.01% (v/v). A separate batch of modified EMJH was made to contain 120 mM NaCl. Prior to shifting to modified EMJH media, Leptospira were cultured in EMJH at 30° C. to a density of 10̂9 bacteria per ml, and subsequently pelleted via centrifugation at 3,200×g for 15 min, using a swinging bucket rotor. Pelleted bacteria were washed 3 times with modified EMJH using 20 ml of media for each washing step. Bacteria were then resuspended in modified EMJH and enumerated via darkfield microscopy. Bacteria were then diluted in modified EMJH to a concentration of 10̂8 bacteria per ml in a total volume of 100 ml for each condition (for incubation at 30° C., 37° C. and in modified EMJH with 120 mM NaCl at 30° C.), in two biological replicates for each condition. After 18 hours of incubation, bacteria were enumerated via darkfield microscopy to validate bacterial viability.
Leptospira were centrifuged at 3,200×g for 10 minutes and the pelleted bacteria were separated from culture supernatants by siphoning supernatants. The pellets were stored at −20° C. and the culture supernatants were transferred to Vivaspin 20 1,000,000 MWCO PES ultrafiltration devices (Sartorius Stedim Biotech, Goettingen, Germany). The latter step ensured removal of any remaining whole Leptospira cells from the culture supernatants. Subsequent centrifugation was performed according to manufacturer's instructions and all manipulations were carried out at room temperature. The flow-through was then concentrated using Amicon Ultra Centrifugal Filters Ultracel-3K (Merck Millipore Ltd., Cork, Ireland) and subsequently with low volume Amicon Ultra—0.5 ml 3 k (Merck Millipore Ltd.). Each 100 ml culture supernatant was concentrated down to a final volume of 20 μl.
To obtain protein from the pelleted whole Leptospira cells, bacterial pellets were resuspended in the respective modified EMJH media to a final volume of 200 μl and sonicated to lyse the bacteria. Protein concentration was measured via UV spectrometry at 280 nm. Samples were diluted 3:1 in Laemmli (4×) sample loading buffer and equal concentrations of protein were used in SDS PAGE.
Recombinant AAS70781.1 (LIC12209) protein (henceforth referred to as Leptospira Beta Propeller 52 or LbP52) was produced essentially as previously described. Rabbit antisera generated against F1aA-2 (49), GroL (50) and LigA (50) were generously provided by Dr. David Haake. Rabbit antisera against recombinant LbP52 (rLbP52) protein was generated using routine procedures.
To obtain Leptospira positive sera, Hartley male guinea pigs (Charles River Laboratories) were obtained at 6 weeks of age and weighed between 450-500 g. Guinea pigs (N=6) were anaesthetized via intramuscular injection with 40 mg ketamine and 4 mg xylazine (per kg body weight) and blood (˜1 ml) was collected into 10 ml Venosafe Plastic Tubes (Terumo, Guyancourt, France) via cardiac heart puncture. Animals were then maintained under normal care conditions for 7 days and then injected intraperitoneal with 105 L. interrogans strain L495 in 1 ml albumin free EMJH. Blood samples from infected animals were collected by terminal cardiac puncture of anaesthetized animals. Serum was collected by incubation of blood samples in Venosafe Plastic tubes (Terumo) at room temperature for 30 min, followed by centrifugation at 1,500×g for 10 min. The supernatant was collected for use in ELISA and immunoblot experiments. Protocols for animal experiments conformed to the guidelines of the Animal Care and Use Committees of the Institut Pasteur (Paris, France).
SDS-PAGE and protein immunoblots were performed as previously described (32, 51) with the following modifications. The SDS-PAGE and immunoblot experiments were performed using 10 μg of total protein from whole cell lysates and culture supernatants. Antiserum to F1aA-2, GroL, LigA and LbP52 was used at 1:2,000, 1:8,000, 1:750 and 1:1,000, respectively. Guinea pig Leptospira positive and pre-immune sera were used at 1:100 and goat polyclonal secondary antibody to guinea pig IgG-Fc (HRP) (Abcam) and IgM-Fc (HRP) (Acris) were used at a dilution of 1:20,000.
For mass spectrometry experiments, 10 μg of protein was allowed to separate for 10 mm on a 4-12% gradient TGX gel, without the addition of any dyes. Samples were then cored and diced into ˜1 mm sections. Protein samples were analysed on an Ultimate 3000 RSLCnano HPLC (Dionex, Camberley, UK) system run in direct injection mode coupled to a QExactive Orbitrap mass spectrometer (Thermo Electron, Hemel Hempstead, UK). Samples were resolved on a 25 cm by 75 μm inner diameter picotip analytical column (New Objective, Woburn, Mass., USA) which was packed in-house with ProntoSIL 120-3 C18 Ace-EPS phase, 3 μm diameter beads (Bischoff Chromatography, Germany). The system was operated at a flow-rate of 300 nl min−1 and a 120 min gradient was used to separate the peptides. The mass spectrometer was operated in a “Top 10” data dependent acquisition mode. Precursor scans were performed in the orbitrap at a resolving power of 70,000, from which the ten most intense precursor ions were selected by the quadrupole and fragmented by HCD at a normalized collision energy of 28%. The quadrupole isolation window was set at 3 m/z. Charge state+1 ions and undetermined charge state ions were rejected from selection for fragmentation. Dynamic exclusion was enabled for 40 s. Data were converted from .RAW to .MGF using ProteoWizard (52).
Identified proteins and the corresponding relative spectral indices were exported to Microsoft Excel for further analyses. The following comparisons of relative protein abundances were made: supernatant protein at 30° C. versus whole cell protein at 30° C. (S vs P 30° C.), supernatant protein at 37° C. versus whole cell protein at 37° C. (S vs P 37° C.), supernatant protein at 30° C. exposed to 120 mM NaCl versus whole cell protein at 30° C. exposed to 120 mM NaCl (S vs P NaCl), supernatant protein at 37° C. versus supernatant protein at 30° C. (37° C. vs 30° C. S) and supernatant protein at 30° C. exposed to 120 mM NaCl versus supernatant protein at 30° C. (NaCl vs 30° C. S). To be deemed as an actively exported exoprotein, proteins had to be detected in all 6 supernatant samples and must have displayed equal to or higher quantity in the supernatant than whole cell Leptospira (for S vs P 30° C., only). To compare exoprotein quantities in culture supernatants (37° C. vs 30° C. S and NaCl vs 30° C. S), protein spectral abundances were compared and only those exoproteins displaying altered expression of at least 2 fold (average between replicate experiments), were deemed as altered in expression in response to temperature and osmotic shifts (Tables 4 and 5).
The protein products of Leptospira genomes have been automatically classified into clusters of orthologous groups (COG) by the MicroScope platform (53). This data was used to sort the detected exoproteins into COGs and the resulting frequencies were compared to those predicted genome-wide. Statistics was performed assuming a binomial distribution where assignment of exoproteins into a COG would be considered a “success” and absence a “failure”. The percentage of coding sequences classified into a COG (as calculated in MicroScope genome-wide) was used as the probability of observing a “success” and the total number of detected exoproteins (208 which were present in all 6 supernatants and that also displayed equal or higher quantities in the supernatant than cell pellets) was used as the sampling size to generate COG specific binomial probability distributions. A p value of p<0.01 was used as a cut-off for significance. For comparison of temperature and osmotic shift regulated exoproteins, a similar analyses was performed with the following modifications. The COG specific probabilities used were from those calculated for exoproteins (not those that would be observed genome-wide) and the sampling size was adjusted to reflect the number of exoproteins being regulated (51 and 69 for temperature and osmotic shifts, respectively).
Transposon mutagenesis was previously performed in the parental strain (Manilae L495) and insertion sites initially identified via semi-random PCR (46-48). The insertion sites for exoprotein mutants were validated via PCR and the primers, insertion sites and transposon mutants are listed in Table 6.
37° C.
NaCl
Whole cell lysate Leptospira protein comparison
Culture supernatant protein comparison
Exoprotein mutants LIC13006− (lenC−), LIC12208−, LIC13060− (lipL36−), LIC10373−, LIC10898− (lipL48−), LIC11977−, LIC11852−, LIC10713− (lruB−) and Manilae L495 were compared for in vitro growth rates in EMJH media at 30° C. Bacterial growth was measured on a daily basis by measuring optical densities via spectroscopy at 420 nm. Exoproteins that demonstrated similar growth rates to Manilae L495 were used in subsequent virulence measurement experiments in Mongolian gerbils (Janvier). To measure virulence, groups of 4 gerbils were injected intraperitoneal with 10̂4 bacteria per animal. Animals were administered Manilae L495 or mutants LIC13006− (lenC−), LIC12208−, LIC13060− (lipL36−), LIC10373−, LIC10898− (lipL48−) and LIC11977−. Animals were monitored on a daily basis for 23 days and sacrificed when moribund. Protocols for animal experiments conformed to the guidelines of the Animal Care and Use Committees of the Institut Pasteur (Paris, France).
To survey the types of proteins found in culture supernatants, whole cell proteins (WCP) and culture supernatant proteins (CSP) from each culture condition were subjected to SDS-PAGE and immunoblot analyses (
Protein immunoblots using antiserum against the 27.2 kDa periplasmic flagellar protein (F1aA-2) revealed protein bands migrating between 25-35 kDa in WCP but no reactivity with CSP (
The immunoblot experiments described above, demonstrated that CSP preparations and temperature and osmotic shift experiments were performed in a manor acceptable for subsequent quantitative global proteome analyses via mass spectrometry. Thus, WCP and CSP (in replicates) were subjected to LC-orbitrap mass spectrometry for identification of proteins and for relative protein quantification, using label-free normalized quantification of peptide mass spectra. These analyses lead to the detection of 982-1,139 proteins in WCP and 613-766 proteins in CSP (Table 8 and Annex_Table S1 and Annex_Table S2). Other notable differences between the samples included detection of relatively large proteins (300 kDa) in WCP which were absent in CSP, and detection of F1aA-2 and AAS68995.1/LIC10371 proteins in WCP and CSP, respectively, but not vice versa (Table 7). The latter protein consists of multiple repeating beta-propeller domains which we found to also be present in 4 other exoproteins and displayed high abundance in all culture supernatants. Normalized spectral index (SIN) has been described (41) and this method of protein quantification revealed a dynamic range approaching 5 orders of magnitude in protein quantities (Table 7).
cUnique
dAAS69403.1/
dAAS68995.1/
aWhole cell Leptospira,
bCulture supernatants,
cCombined experimental replicates,
dAverage between experiments,
ePeriplasmic localization,
dExtracellular localization
In tandem to protein identification, comparison of individual protein SIN in CSP to WCP enabled assignment of proteins that were likely actively localized extracellular, as opposed to being detected as a result of cell lysis and/or outer membrane release due to experimental manipulation. Specifically, proteins that displayed at least equal or higher abundances in the supernatant compared to whole cells and were detected in all 6 supernatants were considered to be actively transported exoproteins. This approach identified 208 unique exoproteins (Annex_Table S3). It should be highlighted that this assumption was only valid under specified conditions, since culture conditions likely alter protein export (as will be evident later). Thus, relative protein quantification used to generate the list of 208 proteins was from comparison of protein quantities in CSP to WCP at 30° C., only. The relative abundance of these exoproteins in supernatants ranged from equal abundance to only being detected in supernatants (Annex_Table S3 and Table 8).
To further evaluate assignment of exoproteins, corresponding primary sequences were used in bioinformatic analyses to predict N-terminal signal peptides using Phobius (55) and non-classical protein export using SecretomeP 2.0 server (56). Of the 208 proteins deemed to be exported, 46 were calculated to contain an N-terminal signal peptide and 38 were predicted to be exported via a non-classical pathway, defined as a pathway that exports proteins lacking a classical signal peptide (Table S3).
Exoproteins were assigned to clusters of orthologous groups (COGs) based on automatic classification of Leptospira genomes in the MicroScope platform (53). Compared to genome-wide expected frequencies, exoproteins in the COGs; cell motility (N), signal transduction mechanisms (T), replication recombination and repair (L), general function (R), function unknown (S) and unclassified (-) were underrepresented (
In contrast, there was a 2 to 4 fold overrepresentation of exoproteins classified in the COGs; energy production and conversion (C), amino acid transport and metabolism (E), nucleotide transport and metabolism (F), carbohydrate transport and metabolism (G) and lipid transport and metabolism (
Comparison of protein abundance in CSP from Leptospira shifted to 37° C. or to modified EMJH containing 120 mM NaCl to CSP from Leptospira at 30° C. (37° C. vs 30° C. S and NaCl vs 30° C. S, respectively) revealed altered expression of 52 proteins in 37° C. vs 30° C. S and 69 proteins in NaCl vs 30° C. S. Both temperature and osmotic shifts resulted in reduced expression of the majority of exoproteins, 45 of the 52 exoproteins displayed reduced abundance of −2 to −10 fold at 37° C. and 57 of 69 exoproteins displayed reduced quantities of −2 to −20 fold in 120 mM NaCl samples. Six proteins were detected between 2.1 to 6.8 fold higher at 37° C. while 12 proteins displayed 2.2 to 6.9 fold higher abundance at 120 mM NaCl. In the latter case, LigA and LbP52 proteins were observed at 2.9 and 5.5 fold higher abundance, respectively, at 120 mM NaCl consistent with what was observed in immunoblot experiments (
Exoproteins displaying altered expression in response to temperature and osmotic shift were subsequently classified into COGs using the MicroScope (53) platform to determine whether a temperature and/or osmotic shift had an effect(s) on the expression/export of COG specific exoproteins (
These comparisons did not reveal significant differences in frequency distributions with the exception of the COG; translation, ribosomal structure and biogenesis (J) (
Exoproteins with Potential Moonlighting Functions
Moonlighting proteins are a class of proteins where a single polypeptide chain performs more than 1 biochemical function (57). Classification of exoproteins into COGs revealed overrepresentation of proteins involved in nutrient uptake and metabolism with the latter comprising of numerous proteins involved in the glycolytic pathway (
aMoonlighting function in other organisms
bAAS69936.1
bAAS69145.1
bAAS71428.1
bAAS70536.1
bAAS70976.1
aMoonlighting functions were obtained from MoonProt (57)
bProteins were detected in all supernatants but displayed a relative abundance <1, compared to respective abundance in whole Leptospira (WCP)
To begin to characterize exoproteins in the context of pathogenesis, WCP and CSP were used in immunoblot experiments with Leptospira positive guinea pig sera (S+) to observe the antibody response to exoproteins, which would also be suggestive of exoprotein expression during the infection process (
These analyses revealed IgG and IgM reactivity against Leptospira exoproteins in S+ sera (
To further assess the necessity of exoproteins in Leptospira viability in vitro and within the host, select Leptospira mutants which had been inactivated in an exoprotein encoding gene were tested for in vitro growth rates and for disease manifestation in gerbils. Leptospira mutants in exoproteins were tested for in vitro viability and their capacity to establish infection in the gerbil infection model measured as time to death of animals. A, Bacteria were inoculated at 104 per ml in EMJH media, cultured at 30° C. and monitored for growth via measuring optical density at 420 nm. Mutants lruB− and lic11852− displayed delayed in vitro growth rates when compared to wt parental strain, whereas all other tested exoprotein mutants displayed comparable growth rates to wt (not shown). B, Mutants displaying in vitro growth rates comparable to wt were used to challenge gerbils at 104 bacteria per animal for the purpose of testing virulence. The protein product of the gene labelled with the * symbol did not fulfill all criteria used to generate the list of exoproteins presented in Annex_3 Table S3, but was detected in culture supernatants. In vitro growth rates of mutants identified two genes that when inactivated result in significantly reduced in vitro growth; lruB (LIC10713) and O-acetylhomoserine (thiol) lyase (LIC11852) (
The other tested Leptospira mutants (in exoprotein encoding genes) did not display an in vitro growth defect (data not shown) and were subsequently used to infect groups of four gerbils via intraperitoneal injection with 104 bacteria per animal (
Global characterization of Leptospira exoproteins has revealed that the majority of exoproteins contain metabolic and energy generation functions, which are likely essential for survival in the diverse environments encountered by these bacteria. Leptospira interrogans evolved from L. biflexa and has likely retained the majority of these exoprotein encoding genes from the saprophyte (62). Classification of exoproteins into COGs indicated that most exoproteins are involved in nutrient acquisition and metabolism, including amino acid, carbohydrate and lipid uptake. Lipid uptake is essential for Leptospira as beta-oxidation is the primary method of energy generation in these bacteria. Evidence for the latter claim is provided in the culturing medium in which the only source of energy is polysorbate 80; a derivative of polyethoxylated sorbitan and oleic acid. The ability of Leptospira to utilize polysorbate 80 as an energy source is in itself evidence of the plasticity of exoprotein function since polysorbate 80 is a synthetic compound which the bacteria have likely not been exposed to in their evolutionary history. It remains to be elucidated whether Leptospira also utilize beta-oxidation during the infection process and if so, whether there would be implications for tissue tropism.
In addition to their metabolic activities, 19 exoproteins also displayed orthology to moonlighting proteins in other microorganisms. The moonlighting properties of two of these proteins have already been demonstrated in Leptospira (37, 63). One of these proteins, phosphopyruvate hydratase (Eno/LIC11954) has been characterized as an enolase, is detected in culture supernatants and displays plasminogen binding activity (37). The other protein, elongation factor Tu (Tuf/LIC12875) is detected on the surface of Leptospira and displays plasminogen and factor H binding (63). Another potential moonlighting protein, a catalase (KatE/LIC12032), has previously been characterized to be required for Leptospira oxidative stress resistance and virulence (51), but the plasminogen binding capacity of this protein (as demonstrated for Candida albicans catalase (64)) remains to be elucidated in Leptospira. In line with a potential role in host-pathogen interactions, 5 putative Leptospira moonlighting proteins have been shown to be immunoreactive (65); suggestive of their expression during the infection process. An exoprotein (not detected in culture supernatants in the present study) directly associated with pathogenesis has been characterized as a collagenase required for tissue invasiveness and virulence in animals (38) while another protein (Lsa32/LIC11089), detected in culture supernatants in the present study, has been characterized and demonstrates laminin and plasminogen binding capacity (66). Additionally a known Leptospira virulence factor high-temperature protein G (HtpG) (67), was detected at high abundance in all culture supernatants. Inactivation of this gene results in attenuation of pathogenesis whereas the complemented strain, which displays increased htpG transcription, shows increased virulence, manifesting in increased hemorrhage and lesions in organs (67). Moreover, the htpG mutant does not display in vitro growth defects, suggesting the extracellular presence of this protein as the cause for disease pathogenesis in animals, either through unidentified moonlighting properties or host inflammatory response to this protein. Taken together, these observations make a compelling case for exoprotein mediated host-pathogen interactions and disease pathogenesis.
While disease pathogenesis can be associated with exoprotein function, the Leptospira mutants disrupted in exoprotein encoding genes tested in this study displayed similar disease manifestation in animals to that observed for the parent strain. It should be highlighted that one of the inactivated genes encoded LipL48 (LIC10898) which was the second most abundant protein in culture supernatants and was detected at levels 11.3 fold higher than that found within the bacteria. Similarly, another inactivated gene (LIC11977) encoding a cyclic nucleotide binding protein was also detected at high abundance in supernatants and displayed a 5.8 fold higher abundance in culture supernatants relative to that found inside the bacteria. Other notable proteins included the endostatin-like protein LenC which has been shown to bind fibronectin (24) and was unique to the supernatants and a Leptospira antigen LipL36. The other 2 mutants were inactivated in genes annotated as lipoproteins. Our curiosity in these genes (LIC12208 and LIC10373) stemmed from the observation that these exoproteins, amongst 3 others, contained multiple repeating beta-propeller domains, were unique to culture supernatants and displayed increased abundance of 5.5 (LpP52) and 3.5 (AAS71615.1/LIC13066) fold, in culture conditions mimicking physiological NaCl concentration. In contrast to the lack of impact on disease pathogenesis, inactivation of two exoprotein encoding genes, annotated as a lipoprotein (containing an imelysin peptidase domain) (lruB/LIC10713) and an O-acetylhomoserine (thiol) lyase (AAS70438.1/LIC11852), rendered the bacteria with in vitro growth defects. The LruB protein has been associated with uveitis (68-70), indicative of expression during pathogenesis. However, LruB also appears to be essential for Leptospiral viability outside the host, is in the COG class P: Inorganic ion transport and metabolism and structural analysis of imelysine-like proteins implicates a role in iron uptake (71). The other vital exoprotein O-acetylhomoserine (thiol) lyase, is in the COG class E: Amino acid transport and metabolism and likely involved in methionine and cysteine regulation (72). It follows that 43 out of the 208 exoproteins were classified in COG class E implicative of exoprotein function in heterotrophic processes.
Immunization and challenge experiments. Preliminary screening of recombinant putative immunoprotective proteins were performed in a group of 4 week-old Golden Syrian hamsters, 5 to 10 hamsters per group. Hamsters may be immunized twice by subcutaneous injection with recombinant proteins (50 μg) at an interval of three weeks (Day 0 and Day 21). Hamsters receiving only Freund's adjuvant represent the control group. Prior to immunization, the recombinant proteins were mixed with an equal volume of Freund's adjuvant.
Immunized hamsters were challenged intraperitoneally with 10 to 10e3 leptospires/dose, depending on the serovar. For each serovar the smallest dose inducing at least 80 death after day 10 pots challenge have been determined. The animals were monitored twice daily, sacrificed on day 71. The tissues from infected animals were collected aseptically for histopathological analysis and culture.
Recombinant protective antigens (LIC10879, LIC13050, LIC10411, LIC13314, LIC10117, LIC11088, LIC11089, LIC13074, LIC20229, LIC11181, LIC13059, LIC10959, LIC11289, LIC12349, LIC13250, LIC20146, LIC10321, LIC10662, LIC11183, LIC11489, LIC12258, LIC12731, LIC12332, LIC10793, LIC11884, LIC20197, LIC11224, LIC11693, LIC12285, LIC10672, LIC10509, LIC10596, LIC11028, LIC11874, LIC13090, LIC10318, LIC10655, LIC11553, LIC11637, LIC12100, LIC12784, LIC13002, LIC13023, LIC13017, LIC11711, LIC10380, LIC10551, LIC10740, LIC11580, LIC11990, LIC12339, LIC12691, LIC12805, LIC13195, LIC13313, LIC13386, LIC13491, LIC20165, LIC10314, LIC10326, LIC10927, LIC10968, LIC11003, LIC12576, LIC13434, LIC13071, LIC11224, LIC10027, LIC10474, LIC10411, LIC20035, LIC20197, LIC11088, LIC11687, LIC11711, LIC10115, LIC12433, LIC10868, LIC10898, LIC11299, LIC11693, LIC12030, LIC20153, LIC10672, LIC11966, LIC10973, Lp1118, MceII and Lsa21) were analyzed again as discussed above in a group of hamsters (5 to 10 animals per group). Animals immunized with Freund's were deemed negative controls. The protective efficacy of the recombinant antigens in combination (50 μg of each antigen) were assessed in a group of hamsters (5 to 10 hamsters per group).
Hamster Protection.
Groups of 10 animals were immunized twice 14 d apart via the SQ route with 100 μG (or 50 μG*) of E. coli purified recombinant proteins or PBS combined 1:1 with Freund's complete (V1) or incomplete (V2) adjuvant. Hamsters were challenged intraperitoneally 14 d after V2 as indicated and observed daily during 21 d for clinical signs and mortality. As indicated in
BSA—Bovine Serum Albumin; CM—Controlled Method; CMD—Challenge Model Development; DMSO—Dimethyl Sulfoxide; EMJH—Ellinghausen, McCullough, Johnson, and Harris; IO—Industrial Operations; LGM—Leptospira Growth Medium; MR—Manufacturing Record; PoC—Proof of Concept; QC—Quality Control; R&D —Research and Development; SAM—Supplemental Assay Method; USDA—United States Department of Agriculture.
Hamsters.
Golden Syrian hamsters, approximately 3 weeks old upon arrival, were used for the studies. The hamsters were no more than 4 weeks old, after an acclimation period, which was typically 3-5 days. Hamsters were vaccinated at approximately 4 weeks of age, and then boosted with a second vaccination (as needed) at the age of 6 weeks. The hamsters were then challenged at approximately 6 or 8 weeks old, depending on whether a second vaccination was required. During Challenge Model Development (CDM) studies 6-8 weeks was used.
Media.
Three types of media were used: EMJH (Difco); Leptospira Growth Medium (Probumin—Celliance/Millipore); and M26C (Merial recipe)—used by IO. The protocol for the preparation of each media can be found in the corresponding product literature. Leptospira Growth Media and LGM-SemiSolid (LGM) is a diluted form of Probumin, which is a Bovine Serum Albumin (BSA) product provided by Celliance/Millipore. It should also be noted that the concentrations of Tween and BSA within the 10×BSA Supplement M26A vary depending on the serovar being grown. The following are the concentrations of Tween and BSA with in the 10×BSA Supplement used for each of the 4 serovars: 1) L. canicola: Tween—375 g/L, BSA —60 g/L; 2) L. grippo: Tween—125 g/L, BSA—100 g/L; 3) L. ictero: Tween—375 g/L, BSA —60 g/L; and 4) L. pomona: Tween—150 g/L, BSA—100 g/L.
There are also two types of preparations for each of these media—a broth and a semisolid. The semisolid version of these media can be made by adding agar at a final concentration of 1.5 g/L to the basal portions of each of these media before autoclaving and the subsequent addition of the BSA supplement. The storage temperature of each media is 4° C. If media is stored at higher temperatures for extended periods of time a reduced Leptospiral growth rate has been observed. The media used for the propagation of Leptospira should be relatively fresh and an expiration date of 3 months from the time it is made should be adhered to. As each of these media age, it is thought that some of the essential proteins within the media could possibly begin to break down and, thus, lead to a reduced growth rate as well as a diminishment in culture activity or vitality.
Leptospira.
Serovars for these studies include the following: L. ictero—CF1 strain (NVSL ID 11403, Lot 14Feb02); L. canicola—Moulton strain (Prot 02096/11june02); L. pomona—MLS, NVSL No. 11000 (22May09); L. grippo—Oregon Shrew Isolate NVSL No. 11808 (01Apr10); L. copenhageni—Fiocruz L130 strain (6Nov07); L. australis strain 11 500 16700. Leptospira were grown in nonvented 15 and 50 mL Falcon tubes (VWR catalog #21008-929 and 21008-938 respectively), at 30° C., under static (not shaking) conditions, and exposed to as little light as possible. Leptospira in a log state of growth are preferred for most applications rather than Leptospira that are in the lag or stationary phases of growth. Once the quantity of Leptospira reaches 108 organisms per mL determined by Petroff-Hausser enumeration, a media passage is typically performed. During media passage, the growing culture is diluted using fresh media by 1:10 and/or 1:100 depending on the logistics of the study and when the culture will be needed. However, it is important to minimize media passages as this will eventually result in attenuation of virulence. After 9 passages in vitro (media) it is important to perform a series of in vivo passages (hamster passages) in order to restore virulence.
Hamster Passage.
Using a Leptospira culture in the log phase of growth, the quantity/concentration was determined via Petroff-Hausser enumeration. Based on the quantity the culture was diluted using fresh growth media to a concentration of 3,000 organisms per mL which served as the challenge material for the donor/passage hamsters. Five (5) hamsters were administered the following volumes of the challenge material via IP inoculation: Hamster #1-1 mL; Hamster #2-0.75 mL; Hamster #3-0.5 mL; Hamster #4-0.5 mL; Hamster #5-0.25 mL.
When performing this method, if the Leptospira concentration at 3,000 organisms per mL proves to be ineffective at causing timely death, the concentration should be increased to 6,000 org./mL and then 9,000 org./mL if the 6,000 dose is ineffective. The onset of illness/death should occur between 7 and 10 days post-challenge for Lc, Li, Lp, and Lg. The onset of illness/death for L. copenhageni is between 10-14 days post challenge. If the onset of illness/death occurs after 10 days post-challenge, or 14 days for copenhageni, additional hamster passages, and a possible increase in challenge dose, should be performed until the onset of illness/death occurs in this range.
Re-Isolation from Hamster.
Once illness/death occurs the liver and kidney of the infected hamster should be removed, homogenized, and either: diluted in media (or other acceptable diluents that will support Leptospira viability), quantified via Petroff-Hausser enumeration, further diluted (if necessary) to 3000 org./mL, and used to challenge 5 more hamsters as described above; diluted in media and filtered (provided that a sufficient number of Leptospira are observable in the homogenate), as specified below in order to remove as many contaminants from the liver homogenate before further propagation and subsequent storage; or diluted 1:10, 1:100, and 1:1,000 in semi-solid media supplemented with 0.1 g/L 5-Fluorouracil (provided that no Leptospira are observable in the homogenate) and allowed to grow for 7-14 days until Leptospira growth is observed. This method is required for the L. copenhageni serovar as there is typically no observable Leptospira immediately after homogenization of the liver and kidney.
Filtration of Liver and Kidney Homogenate.
After independently homogenizing approximately 1 g of infected liver and/or kidney in 9 mL of growth media, the infected homogenate was further diluted by 1:100 in 30 mL of growth media (0.3 mL of homogenate into 29.7 mL media) and then slowly passed through a series of filters as follows using a 60 ml syringe: 1st—Cheese cloth (syringe not needed); 2nd—5 μm syringe filter (PALL Acrodisc, Versapor Membrane, Non-Pyrogenic, Part #4199); 3rd—1.2 μm syringe filter (PALL Acrodisc, Versapor Membrane, Non-Pyrogenic, Part #4190); 4th—0.45 μm syringe filter (PALL Acrodisc, HT Tuffryn Membrane, Non-Pyrogenic, Part #4184); 5th—0.2 μm syringe filter (PALL Acrodisc, GHP membrane, Part # AP-4564T). After filtration, the filtrate was observed in order to confirm the presence of Leptospira (typically about 1-5 organisms per viewing field at 400× magnification). After Leptospira was confirmed, the filtrate was used to inoculate semisolid media at a 1:10 dilution for temporary storage and the remaining filtrate was incubated until the culture was at the peak of the log phase of growth (106—107 org./mL) at which point the culture was frozen. It is important that at least a 1:100 dilution from the original homogenate be performed as high concentrations of the liver homogenate appear to be toxic or inhibitory to Leptospira growth. To freeze Leptospira, an equal volume (1:1) of fresh growth media containing 5% DMSO was added to a culture at the peak of the log phase of growth, aliquot 1 mL into acceptable vials for liquid nitrogen storage, and immediately store in liquid nitrogen. Applicants experimented with gradual freezing, as well as other cryo-preservatives, and this method has proven superior for all 5 serovars currently under investigation.
Inoculation/Seeding from Frozen.
A 1 mL aliquot was removed, thawed at room temperature, and added 0.5 mL to 9.5 mL of fresh semisolid media. The remaining 0.5 mL was added to 9.5 mL of fresh broth media and incubated. Growth was generally observed in the semisolid culture within 14 days.
Challenge Material Preparation.
Challenge material may be prepared two different ways in, depending on the type of test or study:
Challenge with Culture.
For studies involving the testing of experimental candidates, the challenge material is a broth culture, with minimal media passages, that originates from a bank of frozen seeds in which the virulence and target dose have been previously determined after repeated CMD studies with this material. It is advised once a new bank of seeds is made that at least two CMD studies are completed in order to pinpoint the minimal challenge dose to result in 80-100% mortality for that particular bank of seeds. In the CMD studies, several groups of hamsters should be challenged with varying concentrations of a culture.
Challenge with Liver or Kidney Homogenate.
For studies involving the testing of a manufactured serial's potency, it is specified in the Supplemental Assay Methods, provided by the USDA, that the challenge material be the homogenate of a hamster liver/kidney previously infected with the Leptospira serovar of choice. To do this, Leptospira should be passed through a set of hamsters (as described above) and the liver of the infected hamster homogenized. This homogenate, or a dilution of it, then serves as the challenge material.
Challenge Model Development.
When challenging hamsters for a study evaluating the efficacy of an experimental vaccine candidate or a study testing the potency of a manufactured serial, it is important not to over-challenge the hamster as this might act to overwhelm any potentially protective effects the vaccines might induce. To minimize the possibility of a potential over-challenge it is important to establish a model for each serovar being used in which the minimal concentration that results in 80-100% mortality is determined.
, L. australis and L. canicola. In order to determine the lowest concentration to result in 80-100% mortality, one must challenge several groups, containing 8-10 hamsters, with varying concentrations of Leptospira. Since L. ictero, L. australis and L. canicola tend to be more virulent, the best concentrations to test in an initial CMD study would be as follows: 10 organisms; 100 organisms; 500 organisms and 1,000 organisms. Depending on the results of the initial CMD study, the concentrations could be expanded or tightened in subsequent CMD studies to get a more accurate idea of the best challenge concentration.
L. pomona & L. grippo. Because L. pomona and L. grippo tend to be less virulent, the best concentrations to test in an initial CMD study are as follows: 1. 100 organisms; 2. 1,000 organisms; 3. 5,000 organisms; 4. 10,000 organisms. Again, depending on the results of the initial CMD study, the concentrations could be expanded or tightened to get a more accurate idea of the best challenge concentration.
Having thus described in detail preferred embodiments of the present invention, it is to be understood that the invention defined by the above paragraphs is not to be limited to particular details set forth in the above description as many apparent variations thereof are possible without departing from the spirit or scope of the present invention.
This application claims priority to U.S. Provisional Application Ser. No. 62/118,790, which was filed on 20 Feb. 2015, and is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62118790 | Feb 2015 | US |
