The inventive subject matter relates to an immunogenic composition capable of conferring protection against diarrhea caused by Campylobacter jejuni and a method of inducing an immune response to said composition.
C. jejuni is a leading cause of diarrheal disease worldwide and a documented threat to US military personnel (Taylor, 1992; Tauxe, 1992). The symptoms of campylobacter enteritis include diarrhea, abdominal pain, and fever and often accompanied by vomiting. Stools usually contain mucus, fecal leukocytes, and blood, although watery diarrhea is also observed (Cover and Blaser 1999). However, despite the importance of this organism to human disease, there are no licensed vaccines against C. jejuni.
Because of the medical importance of C. jejuni, considerable research is dedicated toward understanding the pathogen. However, notwithstanding this effort, there is surprisingly little understanding about how C. jejuni causes human disease. The genome of one strain, NCTC 11168 (Parkhill, et al., 2000) revealed several unusual aspects about the biology of C. jejuni. One striking feature is the presence of an unexpectedly high number of genes encoding putative enzymes involved in sugar and/or polysaccharide synthesis (Parkhill et al., 2000). The sequence, and resulting research fostered primarily by the availability of the sequence, has revealed that these genes fall into 4 main functional clusters that underscore the importance of some unusual carbohydrate structure to the biology of C. jejuni. These clusters include Lipooligosaccharide (LOS) synthesis, genetic control of flagellin glycosylation, genetic control of N-linked glycosylation, and the control of the biosynthesis and assembly of capsule.
Vaccine strategies against C. jejuni have been largely limited due to the molecular mimicry between lipooligosaccharide (LOS) cores of many strains of C. jejuni and human gangliosides (Moran, et al., 1996). This mimicry is thought to be a major factor in the strong association of C. jejuni infection with Guillain Barre Syndrome (GBS), a post-infectious polyneuropathy (Allos, 1997). Thus, antibodies generated against LOS cores result in an autoimmune response to human neural tissue. It has been estimated that as many as 1/3000 cases of campylobacter enteritis results in GBS. Therefore, the possibility of developing GBS could be associated with any whole cell vaccine against C. jejuni that includes ganglioside mimicry.
LOS synthesis in Campylobacter is controlled by a number of genes, including genes encoding enzymes involved in biosynthesis of sialic acid for incorporation into LOS. Thus, C. jejuni is one of a limited number of bacteria that can endogenously synthesize sialic acid, a 9 carbon sugar that is found in many mammalian cells. This is consistent with the observed molecular mimicry of LOS and human gangliosides important in GBS (Aspinall et al., 1993, 1994 (a and b); Salloway et al., 1996).
Although glycosylation of proteins was once considered to be a eukaryotic trait, there is an increase awareness of prokaryotic protein glycosylation (Power and Jennings, 2003). The best characterized and most extensively glycosylated bacterial protein is campylobacter flagellin. Flagellin from strain 81-176 is glycosylated at 19 serine or threonine sites by an O-linkage to pseudaminic acid and derivatives of pseudaminic acid (Thibault et al., 2001). Pseudaminic acid is an unusual 9 carbon sugar that resembles sialic acid, but which is highly immunogenic, unlike sialic acid. Moreover, mutants that are unable to glycosylate flagellin cannot assemble a flagellar filament (Goon et al, 2003). Since flagella are indispensable virulence determinants of C. jejuni, glycosylation is therefore also a key virulence determinant.
One of the most unusual aspects of C. jejuni is the presence of a general system for N-linked glycosylation of numerous proteins (Szymanski et al., 1999; reviewed in Szymanski et al., 2003). This system, which includes an oligosaccharide transferase similar to that found in the eukaryote Saccharomyces cerevisiae, attaches a glycan which has recently been shown to be a heptasaccharide composed of one bacillosamine residue (an unusual deoxy sugar), one D-glucose, and five D-GalNAc residues (Young et al., 2002). The glycosylation appears to occur on numerous periplasmic, and perhaps, surface exposed proteins in C. jejuni (Young et al., 2002). The unusual glycan, again, appears to be highly immunogenic and is recognized during human infection (Szymanski et al., 1999, 2003).
An interesting recent revelation regarding the Campylobacter genome sequence was the presence of a complete set of capsule transport genes similar to those seen in type II/III capsule loci in the Enterobactericeae (Parkhill et al., 2000; Karlyshev et al., 2000). Subsequent genetic studies in which site-specific mutations were made in several capsule transport genes indicated that the capsule was the serodeterminant of the Penner serotyping scheme (Karlyshev et al., 2000; Bacon et al., 2001). The Penner scheme (or HS for heat stable) is one of two major serotyping schemes of campylobacters and was originally thought to be based on lipopolysaccharide O side chains (Moran and Penner, 1999).
Currently it is believed that all of the structures previously described as O side chains are, in fact, capsules. The chemical structures of the capsule/O side chains of several Penner serotypes have been determined, and these structures include several unusual sugar structures, as summarized in Table 1. The capsule of the genome strain, NCTC 11168, contains a heptopyranose as a L-gluco conformer, which is the first report of such a structure in nature (St. Michael et al., 2002). The capsule of the type strains HS23 and HS36 contain the same carbohydrates in different ratios, and include a mixture of 4 unusual altro-heptoses (6-deoxy-α-D-altro-heptose, D-glycero-α-D-altro-heptose, 6-deoxy-3-Me-α-D-altro-heptose, and 3-Me-D-glycero-α-D-altro-heptose (Aspinall et al., 1992).
There are several examples of highly effective capsular vaccines. S. pneumoniae has 83 different capsular types, but the current S. pneumoniae vaccine contains a mixture of the 23 most prevalent serotypes in the US and Europe. N. meningiditis has fewer serogroups, thus potentially simplifying vaccine development, and, in fact, serogroups A, B and C are responsible for >90% of cases of meningococcal meningitis (Jennings, 1990). However, the polysaccharide from serotype B is poorly immunogenic in man, likely because it mimics human tissues. Capsular vaccines have also been developed against H. influenzae and Group B Streptococcus.
As previously mentioned, there currently are no licensed vaccines against Campylobacter, due greatly to the molecular mimicry between LOS cores of many strains of C. jejuni and human gangliosides (Moran, et al., 1996). However, vaccine formulations incorporating bacterial capsules have been developed against a number of pathogens. In general, capsule vaccines are immunogenic in humans and non-toxic (Jennings, 1990). One of the general problems associated with capsule vaccines is the poor immunogenicity of all polysaccharides in infants, and the fact that many of the capsular vaccines are directed at diseases that are particular threatening to the pediatric population. Based on murine studies, pure polysaccharide antigens are considered to be T cell independent, and capable of inducing only IgM type responses. Adult humans, in contrast, are able to generate IgG, in addition to IgM and IgA antibodies against polysaccharides. Responses in infants to vaccines against type B H. influenzae (Schneerson et al 1980; Anderson, 1983; Marburg, 1986), group A, B and C Neisseria meningiditis (Jennings and Lugowski, 1981 and 1983; and type 6A Streptococcus pneumoniae (Chu et al., 1983) have all improved following conjugation to proteins.
C. jejuni capsule, as defined in this application, is a generic term for capsular polymers, which are composed of repeating polysaccharide structures. The repeating structures can be homopolymers, defined as a repeating single sugar moiety, or repeating oligosaccharides (i.e. disaccharides or trisaccharides, etc.). A number of species of capsular repeating polysaccharide polymers have been identified. To illustrate the genus of capsular polysaccharide structures, Table 2 lists known capsular polysaccharide structures for Campylobacter strains.
An object of this invention is an anti-C. jejuni immunogenic composition, composed of a capsule polysaccharide polymer, capable of inducing an immune response against important pathogenic strains C. jejuni without concomitantly inducing GBS.
Another object of the invention is an anti-C. jejuni prophylactic formulation with enhanced T-cell dependent immunity to important pathogenic strains of the bacteria by conjugating the capsule of C. jejuni to T-dependent carrier molecules.
Yet, another object of the invention is a method of administering the carrier conjugated or unconjugated anti-C. jejuni capsule polysaccharide composition in order to induce an immune response.
C. jejuni capsular moieties are important in serodetermination. However, despite over 60 Penner serotypes having been identified, most Campylobacter diarrheal disease is caused by C. jejuni from a limited number of serotypes. Because of the importance of capsule structure in serodetermination, it is postulated that they are highly immunogenic structures. Additionally, they are also unlikely to exhibit the unwanted autoimmune induction caused by immuno-mimicry observed by lipooligosaccharides. Therefore, capsules or capsular components would be highly useful in anti-C. jejuni vaccines. C. jejuni capsule are composed of repeating polysaccharide structures. The repeating structures can be homopolymers, defined as a repeating single sugar moiety, or repeating oligosaccharides such as disaccharides or trisaccharides.
The chemical composition of C. jejuni capsules were analyzed by first growing C. jejuni and then isolating and purifying the capsule using water-phenol extraction, ultra-centrifugation and gel permeation chromatography. The specific carbohydrate structures were determined by chemical manipulations in combination with gas-liquid chromatography (GLC), and GLC-mass spectrometry, and fast atom bombardment-mass spectrometry (FAB-MS). Anomeric configuration of the sugars was determined by nuclear magnetic resonance (NMR) spectrometry.
Based on carbohydrate analyses as shown in
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2/7]-6-d-alpha-D-ido-Hep-(1→
or
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2]-L-glycero-alpha-D-ido-Hep-(1→
where P represents O-methyl-phosphoramidate and is present in non-stoichiometric amounts. In some disaccharides, 3-hydroxypropanoyl may also be present.
Therefore, an aspect of this invention is an immunogenic formulation composed of isolated capsular polysaccharide composed of disaccharide repeats, each disaccharide having general formula:
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2/7]-6d-alpha-D-ido-Hep-(1→, or
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2]-L-glycero-alpha-D-ido-Hep-(1→,
where P represents O-methyl-phosphoramidate and is present in non-stoichiometric amounts. Alternatively the formulation can be composed of a capsular polysaccharide containing a mixture of both disaccharide structures. MALDI-TOF-MS analyses revealed that the average molecular weight of the BH0142 CPS analyzed here was approximately 8300 Da.
Similarly, the capsular polysaccharide of strain CG8486 was analyzed and shown to be composed of a similar structure but of a repeating disaccharide illustrate by the formula
→3)-6-deoxy-beta-D-ido-Heptose-(1→4)-beta-D-GlcNAc-(1→.
With O-methyl phosphoramidate units present in non-stoichiometric amounts at the O-2 and/or O-7 positions of 6-deoxy-beta-D-ido-Heptose. MALDI-TOF-MS analyses revealed that the molecular weight of the CG8486 CPS analyzed here was on average between 6400 and 6700 Da.
Since IgG response is often predominantly observed as a T-cell independent immune response. Therefore, children are typically only capable of mounting an IgM response in the face of polysaccharide antigens with adults capable of generating an IgG, IgA and IgM response.
In order to potentially further improve the response to capsule moieties, the immunogenicity of C. jejuni capsule can be conjugated to T-dependent carrier proteins.
Conjugation of C. jejuni strain BH0142 capsular polysaccharide to a carrier protein, such as cross reacting material 197 (CRM197), can be achieved by selectively oxidizing the exocyclic glycero moiety, with periodate, of one or more L-glycero-D-ido-heptose units present in each capsular polysaccharide. Analysis (
The CPS8486-CRM197 glycoconjugates were synthesized by covalent attachment of the CG8486 CPS to CRM197 by reductive amination (
Mice were immunized with 3 doses of either 1, 5 and 25 micrograms of the capsule conjugate from CG8486 subcutaneously at four-week intervals. Blood samples were collected immediately before each vaccination and at 4, 8, 12 and 14 weeks after the third vaccination. The CPS8486 IgG titers were determined by ELISA. Animals receiving PBS showed baseline levels of CPS8486-specific IgG titer (geometric endpoint titer 3.4±0.40). The titers of immunized animals are shown in Table 2. Immunization with 1 μg of CG8486 capsule conjugate vaccine failed to induce CPS8486-specific IgG. In contrast, animals immunized with 5 and 25 μg of vaccine had similar high levels of antigen-specific serum IgG after two doses. Delivery of the third dose of 5 μg of vaccine further enhanced IgG levels, but vaccination with the third dose of 25 μg of vaccine did not. The peak levels of IgG titers in the groups that received 5 μg and 25 μg of the CG8486 capsule conjugate vaccine are significantly higher than those that received either 1 μg of the vaccine or PBS, but are not significantly different than each other. After completion of the immunization series, ≧90% of the animals met the definition of responders in the groups receiving the two higher doses. CPS8486-specific IgG levels remained elevated for at least 14 weeks after the third dose.
To determine the ability of the CG8486 capsule conjugate vaccine to protect against homologous challenge in the mouse intranasal model of infection (
An aspect of this invention is the ability of one or more related isolated disaccharide polymers found in C. jejuni capsules to induce a vigorous and efficacious immune response in humans but not induction of contraindicating Guillain Barre Syndrome. For each vaccine formulation containing capsules from a single or mixtures of C. jejuni strains, a limited amount of experimentation is required to ascertain the optimal effective dose ranges. However, a prophetic method for the induction of anti-C. jejuni medicated diarrheal protective immunity contains the following steps:
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2/7]-6d-alpha-D-ido-Hep-(1→ or
→4)-[P→3]-alpha-D-Gal-(1→3)-[P→2]-L-glycero-alpha-D-ido-Hep-(1,
Similar prophetic method for the induction of anti-C. jejuni medicated diarrheal protective immunity using CPS8486 capsular polysaccharide contains the following steps:
(a) priming is by administration of an immunogenic formulation containing isolated C. jejuni capsular polysaccharide composed of disaccharide repeats with the general formula:
→3)-6-d-β-D-ido-Hep-(1→4)-β-D-GlcNAc-(1→,
with O-methyl phosphoramidate units present in non-stoichiometric amounts at the O-2 and/or O-7 positions of 6-deoxy-beta-D-ido-Heptose.
In a preferred embodiment, the isolated disaccharide is conjugated to a carrier molecule. The immunogenic formulation can be administered orally, nasally, subcutaneously, intradermally, transdermally, transcutaneously intramuscularly, or rectally. Depending on the route of administration, the vaccine formulation can be administered with or without any of a number of adjuvants, including but not limited to LTR 192G, Aluminum hydroxide, RC529E, QS21, E294, oligodeoxynucleotides (ODN), CpG-containing oligodeoxynucleotides, aluminum phosphate, MPL® (GlaxoSmithKline, Middlesex, UK) or combinations of these or other potential adjuvants. The range of a unit dose of immunogen is 0.1 μg to 10 mg of immunogen in a range of buffer solutions.
(b) Subsequent to a priming dose, 1 to 4 boosting doses can also be administered with unit dose range of 0.1 μg to 10 mg of immunogen in a buffered aqueous solution with or without adjuvant.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
This application claims the benefit of Provisional Application Ser. No. 60/962,313, filed Jul. 27, 2007, and is a Continuation-in-Part application of U.S. patent application Ser. No. 11/524,057, filed Sep. 20, 2006, which claims benefit of Provisional Application Ser. No. 60/722,086, filed Sep. 21, 2005 and is related to PCT application PCT/US06/36619, filed Sep. 20, 2006, all of which are incorporated by reference.
Number | Date | Country | |
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60962313 | Jul 2007 | US | |
60722086 | Sep 2005 | US |
Number | Date | Country | |
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Parent | 11524057 | Sep 2006 | US |
Child | 12221150 | US |