Patent Grant
6974680
This invention relates to virulence genes and proteins, and their use. More particularly, it relates to genes and proteins/peptides obtained from gram-negative bacteria, and their use in therapy and in screening for drugs.
According to health care experts, infectious diseases caused by microbes are responsible for more deaths worldwide than any other single cause. The current estimate of the annual cost of medical care for treating infectious diseases in the United States alone is about $120 billion. While antibiotic treatment is effective for many microbial infections, antibiotic resistance among pathogenic bacteria is a growing health concern. Indeed, the American Medical Association has concluded that, “the global increase in resistance to antimicrobial drugs, including the emergence of bacterial strains that are resistant to all available antibacterial agents, has created a public health problem of potentially crisis proportions.”
Pseudomonas and Klebsiella are two genuses of gram-negative bacteria that pose a significant health risk to infected host organisms, in part, due to their resistance to many antibiotics. These bacteria are noted for causing life-threatening infections, particularly in the lung. Cancer and burn patients also commonly suffer serious Pseudomonas infections, as do certain other individuals with immune system deficiencies. While Klebsiella sp. is responsible for many types of infections, outside of a medical setting, the most common infection caused by Klebsiella bacteria is pneumonia.
There is a need in the art for new antimicrobial therapeutic strategies.
The present invention is based, in part, on the discovery of 46 genes, when mutated lower the virulence of a gram-negative bacterium, and can be used in new antimicrobial therapeutic strategies. The invention provides attenuated bacterial mutants that are derived from pathogenic strains. These attenuated bacterial stains have a mutation in a VIRX gene identified herein as VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR43, VIR44, VIR45, and VIR46; and show reduced inhibition of Dictyostelium amoeba growth when compared to the growth observed in the presence of an isogenic bacterial strain. The term, “pathogenic,” as used herein, is defined as an agent's ability to cause disease, damage or harm to a host organism. The term, “attenuated,” as used herein, means an organism made less virulent relative to an isogenic pathogenic organism. The term, “mutant,” as used herein, an organism carrying a specific mutation of a gene that is expressed in the organism's phenotype. A mutation may be insertional inactivation or deletion of a gene. It is preferred that the mutation be an insertional inactivation of a gene.
The invention also provides attenuated bacterial mutants that are derived from pathogenic gram-negative bacterial strains. These attenuated gram-negative bacterial strains have a mutation in a VIRX gene identified herein as VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR43, VIR44, VIR45, and VIR46; and show reduced inhibition of Dictyostelium amoeba growth when compared to the growth observed in the presence of an isogenic bacterial strain. A mutation may be insertional inactivation or deletion of a gene. It is preferred that the mutation be an insertional inactivation of a gene. It is also preferred that the attenuated gram-negative bacterial mutant be derived from a Pseudomonas or Klebiella spp. It is more preferred that the attenuated gram-negative bacterial mutant is a strain of P. aeruginosa or K. pneumoniae.
The invention additionally provides for a VIRX gene that may be part of an operon. The term, “operon,” as used herein, is a unit of bacterial gene expression and regulation comprising several genes, usually with complementary functions. Insertion in a gene in an operon typically interferes with the function of this gene and of other genes located downstream or upstream in the operon. The function attributed to a gene refers to its function and/or that of any gene located downstream or upstream in the same operon. Accordingly, the invention also provides for a bacterial strain comprising an operon encoding a gene selected from the group consisting of VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR38, VIR39, VIR40, VIR41, VIR42, VIR44, VIR45, and VIR46, wherein the bacterial strain includes a mutation that reduces expression of the VIRX gene relative to an isogenic bacterial strain lacking the mutation. In one embodiment, the the mutation reduces inhibition of Dictyostelium amoeba growth when compared to the growth of Dictyostelium amoeba in the presence of an isogenic bacterial strain lacking the mutation.
The invention provides for one or more of the following attenuated Pseudomonas mutant strains: MUT1; MUT2; MUT3; MUT4; MUT5; MUT6; MUT7; MUT8; MUT9; MUT10; MUT11; MUT12; MUT13; MUT14; MUT15; MUT16; MUT17; MUT18; and MUT 19. The invention also provides for one or more of the following attenuated Klebsiella mutant strains: MUT20; MUT21; MUT22; MUT23; MUT24; MUT25; MUT26; MUT27; MUT28; MUT29; MUT30; MUT31; MUT32; MUT33; MUT34; MUT35; MUT36; MUT37; MUT38; MUT39; MUT40; MUT41; MUT42; MUT43; MUT44; MUT45; and MUT46.
The invention additionally provides a method for identifying an antimicrobial drug, wherein a candidate composition is contacted with at least one polypeptide encoded by a gene selected from the group consisting of VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR43, VIR44, VIR45 and VIR46. The biological activity of polypeptide in the presence of the candidate composition is compared with the biological activity of the polypeptide in the absence of the candidate composition. Alteration of the biological activity of the polypeptide indicates that the candidate composition is an antimicrobial drug. In some embodiments, the candidate composition contains at least two molecules. The candidate composition can contain at least one molecule less than about 500 Daltons or at least one molecule greater than about 500 Daltons. The candidate composition can be, e.g., an immunoglobulin, polysaccharide, lipid, nucleic acid, or combination thereof.
The invention additionally provides a method for identifying an antimicrobial drug, wherein a candidate composition is contacted with at least one polynucleotide encoded by a gene selected from the group consisting of VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR43, VIR44, VIR45, and VIR46. The expression of the polynucleotide in the presence of the candidate composition is compared with the expression of the polynucleotide in the absence of the candidate composition. Alteration of the expression of the polynucleotide indicates that the candidate composition is an antimicrobial drug. In some embodiments, the candidate composition contains at least two molecules. The candidate composition can contain at least one molecule less than about 500 Daltons or at least one molecule greater than about 500 Daltons. The candidate composition can be a polypeptide, polysaccharide, lipid, nucleic acid, e.g., ribonucleic acid, or combination thereof. In a preferred embodiment, the ribonucleic acid of the candidate composition is a small interfering ribonucleic acid.
The invention additionally provides a method for determining the degree of virulence of a pathogen present in a subject, comprising:
In a preferred embodiment, the subject is a mammal. It is more preferred that the subject is a human.
The invention also provides a method for determining the degree of virulence of a pathogen present in a subject, comprising:
(a) measuring the level of expression of at least one polynucleotide encoded by a gene selected from the group consisting of VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR44, VIR45, and VIR46, in a sample from the first subject; and
(b) comparing the amount of the polynucleotide in the sample of step (a) to the amount of the polynucleotide present in a control sample from a second subject known not to have the presence of the pathogen, wherein an alteration in the expression level of the polypeptide in the first subject as compared to the control sample indicates the degree of virulence of the pathogen.
In a preferred embodiment, the subject is a mammal. It is more preferred that the subject is a human.
The invention additionally provides attenuated bacterial strains that can be used as vaccines and as vectors for foreign antigens and for foreign DNA. These attenuated bacterial strains are useful for the preparation of vaccines effective against diseases associated with the corresponding bacterial strains. In a preferred embodiment, the attenuated bacterial strains are derived from Pseudomonas or Klebsiella spp.
The invention additionally provides attenuated bacterial strains that can be used as vectors for foreign genes cloned from other pathogens that will be expressed into proteins, and will raise protective immune responses against the pathogens from which they are derived. In a preferred embodiment, the attenuated bacterial strains used as the vectors are derived from Pseudomonas or Klebsiella spp.
Unless otherwise defined, 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 invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In the case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description and claims.
The present invention is based, in part, on the discovery of 46 genes when mutated lower the virulence of a gram-negative bacterium. Nineteen of these virulence genes were identified in P. aeruginosa PT894, while the remaining 27 genes were derived from mutagenesis of Klebsiella. These bacterial mutants have attenuated virulence relative to isogenic bacterial strains and are designated “MUTX.” Provided herein are virulence genes affected in each novel, attenuated MUTX strain, as well as the nucleotides and polypeptides encoded thereby. The sequences encoded by the affected genes are collectively referred to as “VIRX nucleic acids” or “VIRX polynucleotides” and the corresponding encoded polypeptides are referred to as “VIRX polypeptides” or “VIRX proteins.” Unless indicated otherwise, “VIRX” is meant to refer to any of the novel sequences disclosed herein.
The peptides and genes of the invention are useful for the preparation of therapeutic agents to treat infection because they attenuate the virulence of the wild-type pathogen. Therapy can be preventative or therapeutic. A subject receiving therapy can be, e.g. a human, a non-human primate (such as an ape, gorilla, or chimpanzee), cow, horse, pig, sheep, dog, cat, or rodent (including mouse or rat).
Genes encoding virulence factors (e.g., pathogens or toxins) to a host organism were identified by comparing the growth of Dictyostelium discoideum, in the presence and absence of test mutants of Pseudomonas and Klebsiella with an identifiable genetic alteration as detailed in Intentional Application PCT/IB02/03277, filed Jun. 7, 2002. Dictyostelium amoebae feed phagocytically upon bacteria such as K. pneumoniae. When Dictyostelium cells are plated with K. pneumoniae bacteria, each amoeba creates a plaque in the bacterial lawn in the region where bacteria have been phagocytosed. Addition of pathogenic bacteria, e.g., P. aeruginosa strain PT894 to the lawn of K. pneumoniae bacteria, inhibits the growth of the amoebae.
Pseudomonas test mutants were made by transposon insertion according to known methods in the art and tested for virulence in a Dictyostelium growth assay (see, PCT/IB02/03277, filed Jun. 7, 2002). Klebsiella mutants were also made by transposon insertion according to known methods in the art and tested for virulence in a Dictyostelium growth assay (see, PCT/IB02/03277, filed Jun. 7, 2002) using the PIIG1a mutant Dictyostelium strain (Cornillon et al., J. Biol. Chem., 275(44): 34287-92, 2000), a strain which was found to be particularly sensitive to virulent bacteria. Specifically, the Klebsiella mutants were obtained by standard bacteria electroporation technique using the plasposon pNKBOR (Genbank accession number: AF310136) and selected on solid LB medium containing 50 μg/ml kanamycin (Rossignol et al., Res. Microbiol., 152(5): 481-5, 2001). Other mutagenesis methods known in the art, e.g., ultraviolet radiation exposure, treatment with intercalating agent or transducing phage, may also be used to generate mutants. Mutations yielding reduced virulence were identified where the growth of the Dictyostelium test host organism exposed to the mutant pathogen was greater than the Dictyostelium test host organism exposed to wild-type pathogen. Specific genetic mutations in pathogens displaying reduced virulence were subsequently identified and characterized by techniques well known in the art. Identification of specific gene mutations in Klebsiella mutants was performed by plasmid rescue and cloning of the genomic DNA at the insertion site mutant using the BglII or ApaI restriction enzyme according to (Rossignol et al., Res. Microbiol., 152(5): 481-5, 2001). Identification of specific gene mutations in Pseudomonas mutants was performed by subcloning the transposon and surrounding bacteria genomic DNA into an acceptor plamid. DNA sequencing was performed on amplified rescued plasmids, in order to identify the insertion site of the transposon. Rat mortality assays such as that described by Join-Lambert et al., Antimicrob. Agents Chemother., 45(2): 571-6, 2001, can be used to corroborate attenuated virulence activity in a mammalian host.
The 19 Pseudomonas attenuated MUTX organisms harboring the VIRX genes are summarized below in Table 1.
The 27 Klebsiella attenuated MUTX organisms harboring the VIRX genes disclosed in the present invention and assigned a new role in virulence are summarized below in Table 2.
A. Attenuated Pseudomonas aeruginosa Mutants
MUT1
A Pseudomonas bacterial mutant (MUT1) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding anthranilate phosphoribosyltransferase (PA0650). This gene encodes the VIR1 nucleic acid (SEQ ID NO:1) shown in Table 3A.
The VIR1 protein (SEQ ID NO:2) encoded by SEQ ID NO:1 is presented using the one-letter amino acid code in Table 3B.
The role of VIR1 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT2
A Pseudomonas bacterial mutant (MUT2) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding the ATP sulfurylase small subunit (CysD; PA4443). This gene encodes the VIR2 nucleic acid (SEQ ID NO:3) shown in Table 4A.
The VIR2 protein (SEQ ID NO:4) encoded by SEQ ID NO:3 is presented using the one-letter amino acid code in Table 4B.
The role of VIR2 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT3
A Pseudomonas bacterial mutant (MUT3) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding CysQ (PA5175). This gene encodes the VIR3 nucleic acid (SEQ ID NO:5) shown in Table 5A.
The VIR3 protein (SEQ ID NO:6) encoded by SEQ ID NO:5 is presented using the one-letter amino acid code in Table 5B.
MUT4
A Pseudomonas bacterial mutant (MUT4) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding D-amino acid dehydrogenase, small subunit (dadA; PA5304). This gene encodes the VIR4 nucleic acid (SEQ ID NO:7) shown in Table 6A.
The VIR4 protein (SEQ ID NO:8) encoded by SEQ ID NO:7 is presented using the one-letter amino acid code in Table 6B.
The role of VIR4 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT5
A Pseudomonas bacterial mutant (MUT5) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding imidazoleglycerol-phosphate synthase, cyclase subunit (hisF; PA5140). This gene encodes the VIR5 nucleic acid (SEQ ID NO:9) shown in Table 7A.
The VIR5 protein (SEQ ID NO:10) encoded by SEQ ID NO:9 is presented using the one-letter amino acid code in Table 7B.
MUT6
A Pseudomonas bacterial mutant (MUT6) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding N-acetyl-γ-glutamyl-phosphate reductase (ArgC; PA0662). This gene encodes the VIR6 nucleic acid (SEQ ID NO:11) shown in Table 8A.
The VIR6 protein (SEQ ID NO:12) encoded by SEQ ID NO:11 is presented using the one-letter amino acid code in Table 8B.
The role of VIR6 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT7
A Pseudomonas bacterial mutant (MUT7) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding dihydrolipoamide acetyltransferase (AceF; PA5016). This gene encodes the VIR7 nucleic acid (SEQ ID NO:13) is shown in Table 9A.
The VIR7 protein (SEQ ID NO: 14) encoded by SEQ ID NO: 13 is presented using the one-letter amino acid code in Table 9B.
MUT8
A Pseudomonas bacterial mutant (MUT8) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding NADH dehydrogenase I chain H (nuoH; PA2643). This gene encodes the VIR8 nucleic acid (SEQ ID NO:15) shown in Table 10A.
The VIR8 protein (SEQ ID NO: 16) encoded by SEQ ID NO:15 is presented using the one-letter amino acid code in Table 10B.
MUT9
A Pseudomonas bacterial mutant (MUT9) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding pyoverdine synthase D (PvdD; PA2399). This gene encodes the VIR9 nucleic acid (SEQ ID NO:17) shown in Table 11A.
The VIR9 protein (SEQ ID NO:18) encoded by SEQ ID NO:17 is presented using the one-letter amino acid code in Table 11B.
MUT10
A Pseudomonas bacterial mutant (MUT10) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding the RND multidrug efflux transporter MexD (mexD; PA4598). This gene encodes the VIR10 nucleic acid (SEQ ID NO:19) shown in Table 12A.
The VIR10 protein (SEQ ID NO:20) encoded by SEQ ID NO: 19 is presented using the one-letter amino acid code in Table 12B.
MUT11
A Pseudomonas bacterial mutant (MUT11) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding PA3721. This gene encodes the VIR11 nucleic acid (SEQ ID NO:21) shown in Table 13A.
The VIR11 protein (SEQ ID NO:22) encoded by SEQ ID NO:21 is presented using the one-letter amino acid code in Table 13B.
MUT12
A Pseudomonas bacterial mutant (MUT12) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding PA0596. This gene encodes the VIR12 nucleic acid (SEQ ID NO:23) shown in Table 14A.
The VIR12 protein (SEQ ID NO:24) encoded by SEQ ID NO:23 is presented using the one-letter amino acid code in Table 14B.
MUT13
A Pseudomonas bacterial mutant (MUT13) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding PA5265. This gene encodes the VIR13 nucleic acid (SEQ ID NO:25) shown in Table 15A.
The VIR13 protein (SEQ ID NO:26) encoded by SEQ ID NO:25 is presented using the one-letter amino acid code in Table 15B.
MUT14
A Pseudomonas bacterial mutant (MUT14) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding pyochelin biosynthetic protein pchC (PA4229). This gene encodes the VIR14 nucleic acid (SEQ ID NO:27) shown in Table 16A.
The VIR14 protein (SEQ ID NO:28) encoded by SEQ ID NO:27 is presented using the one-letter amino acid code in Table 16B.
MUT15
A Pseudomonas bacterial mutant (MUT15) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding dihydroaeruginoic acid synthetase pchE (PA4226). This gene encodes the VIR15 nucleic acid (SEQ ID NO:29) shown in Table 17A.
The VIR15 protein (SEQ ID NO:30) encoded by SEQ ID NO:29 is presented using the one-letter amino acid code in Table 17B.
MUT16
A Pseudomonas bacterial mutant (MUT16) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding pyochelin synthetase pchF (PA4225). This gene encodes the VIR16 nucleic acid (SEQ ID NO:31) shown in Table 18A.
The VIR16 protein (SEQ ID NO:32) encoded by SEQ ID NO:31 is presented using the one-letter amino acid code in Table 18B.
MUT17
A Pseudomonas bacterial mutant (MUT 17) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding putative ATP-binding component of the ABC transporter, pchH (PA4223). This gene encodes the VIR17 nucleic acid (SEQ ID NO:33) shown in Table 19A.
The VIR17 protein (SEQ ID NO:34) encoded by SEQ ID NO:33 is presented using the one-letter amino acid code in Table 19B.
The role of VIR17 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT18
A Pseudomonas bacterial mutant (MUT18) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding the putative ATP-binding component of ABC transporter, pchI (PA4222). This gene encodes the VIR18 nucleic acid (SEQ ID NO:35) shown in Table 20A.
The VIR18 protein (SEQ ID NO:36) encoded by SEQ ID NO:37 is presented using the one-letter amino acid code in Table 20B.
The role of VIR18 in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
MUT19
A Pseudomonas bacterial mutant (MUT19) was made by transposon insertion in a P. aeruginosa wild-type strain PT894. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as a gene cluster encoding the P. aeruginosa serotype 09 putative O-antigen biosynthesis pathway (VIR19). The insertion site nucleic acid sequence identifying the VIR19 gene in MUT19 is shown in Table 21.
The role of this cluster in virulence was confirmed using phage to retransduce this mutation into the wild-type PT894 strain where attenuated virulence was again observed in the Dictyostelium growth assay compared to an isogenic bacterial strain.
B. Attenuated Klebsiella Mutants
MUT20
A Klebsiella bacterial mutant (MUT20) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding a hypothetical transcriptional regulator in met G-dld intergenic region (VIR20). The insertion site nucleic acid sequence identifying the VIR20 gene in MUT20 is shown in Table 22.
MUT21
A Klebsiella bacterial mutant (MUT2 1) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding β-cystathionase (VIR21). The insertion site nucleic acid sequence identifying the VIR21 gene in MUT21 is shown in Table 23.
MUT22
A Klebsiella bacterial mutant (MUT22) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as ribosome binding factor A (VIR22). The insertion site nucleic acid sequence identifying the VIR22 gene in MUT22 is shown in Table 24.
MUT23
A Klebsiella bacterial mutant (MUT23) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding aspartokinase/homoserine dehydrogenase (VIR23). The insertion site nucleic acid sequence identifying the VIR23 gene in MUT23 is shown in Table 25.
MUT24
A Klebsiella bacterial mutant (MUT24) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding cystathione γ-synthetase (VIR24). The insertion site nucleic acid sequence identifying the VIR24 gene in MUT24 is shown in Table 26.
MUT25
A Klebsiella bacterial mutant (MUT25) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding phosphoribosylformylglycinamidine synthase (VIR25). The insertion site nucleic acid sequence identifying the VIR25 gene in MUT25 is shown in Table 27.
MUT26
A Klebsiella bacterial mutant (MUT26) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding homoserine transsuccinylase (VIR26). The insertion site nucleic acid sequence identifying the VIR26 gene in MUT26 is shown in Table 28.
MUT27
A Klebsiella bacterial mutant (MUT27) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding 3′-phosphoadenosine 5′-phosphosulfate reductase (VIR27). The insertion site nucleic acid sequence identifying the VIR27 gene in MUT27 is shown in Table 29.
MUT28
A Klebsiella bacterial mutant (MUT28) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding Sfi protein (VIR28). The insertion site nucleic acid sequence identifying the VIR28 gene in MUT28 is shown in Table 30.
MUT29
A Klebsiella bacterial mutant (MUT29) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding transcriptional activator protein LysR (VIR29). The insertion site nucleic acid sequence identifying the VIR29 gene in MUT29 is shown in Table 31.
MUT30
A Klebsiella bacterial mutant (MUT30) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding TrpD (VIR30). The insertion site nucleic acid sequence identifying the VIR30 gene in MUT30 is shown in Table 32.
MUT31
A Klebsiella bacterial mutant (MUT31) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding N-acetylglucosamine-6-phosphate deacetylase (VIR31). The insertion site nucleic acid sequence identifying the VIR31 gene in MUT31 is shown in Table 33.
MUT32
A Klebsiella bacterial mutant (MUT32) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding WaaQ (VIR32; Regué et al. J. Bacteriol. 183(12): 3564-73, 2001). The insertion site nucleic acid sequence identifying the VIR32 gene in MUT32 is shown in Table 34.
MUT33
A Klebsiella bacterial mutant (MUT33) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding 2-isopropylmalate synthase (VIR33). The insertion site nucleic acid sequence identifying the VIR33 gene in MUT33 is shown in Table 35.
MUT34
A Klebsiella bacterial mutant (MUT34) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding histidinol dehydrogenase (VIR34). The insertion site nucleic acid sequence identifying the VIR34 gene in MUT34 is shown in Table 36.
MUT35
A Klebsiella bacterial mutant (MUT35) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding UDP-galactopyranose mutase (VIR35; Clarke et al., J. Bacteriol., 177: 5411-18, 1995). The insertion site nucleic acid sequence identifying the VIR35 gene in MUT35 is shown in Table 37.
MUT36
A Klebsiella bacterial mutant (MUT36) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding O-antigen export system permease protein rfba (VIR36; Bronner et al., Mol. Microbiol., 14: 505-19, 1994). The insertion site nucleic acid sequence identifying the VIR36 gene in MUT36 is shown in Table 38.
MUT37
A Klebsiella bacterial mutant (MUT37) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding uridyltransferase (VIR37). The insertion site nucleic acid sequence identifying the VIR37 gene in MUT37 is shown in Table 39.
MUT38
A Klebsiella bacterial mutant (MUT3 8) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding pyridoxine phosphate biosynthetic protein PdxJ-PdxA (VIR38). The insertion site nucleic acid sequence identifying the VIR38 gene in MUT38 is shown in Table 40.
MUT39
A Klebsiella bacterial mutant (MUT39) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding triose phosphate isomerase (VIR39). The insertion site nucleic acid sequence identifying the VIR39 gene in MUT39 is shown in Table 41.
MUT40
A Klebsiella bacterial mutant (MUT40) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding aldehyde dehydrogenase (VIR40). The insertion site nucleic acid sequence identifying the VIR40 gene in MUT40 is shown in Table 42.
MUT41
A Klebsiella bacterial mutant (MUT41) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding galacosyl transferase (VIR41; Clarke et al., J. Bacteriol., 177 : 5411-18, 1995). The insertion site nucleic acid sequence identifying the VIR41 gene in MUT41 is shown in Table 43.
MUT42
A Klebsiella bacterial mutant (MUT42) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding siroheme synthetase (VIR42; Kolko et al., J. Bacteriol., 183: 328-35, 2001).
The insertion site nucleic acid sequence identifying the VIR42 gene in MUT42 is shown in Table 44.
MUT43
A Klebsiella bacterial mutant (MUT43) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase (VIR43). The insertion site nucleic acid sequence identifying the VIR43 gene in MUT43 is shown in Table 45.
MUT44
A Klebsiella bacterial mutant (MUT44) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding glucose-6-phosphate isomerase (VIR44). The insertion site nucleic acid sequence identifying the VIR44 gene in MUT44 is shown in Table 46.
MUT45
A Klebsiella bacterial mutant (MUT45) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding DNA methylase (VIR45). The insertion site nucleic acid sequence identifying the VIR45 gene in MUT45 is shown in Table 47.
MUT46
A Klebsiella bacterial mutant (MUT46) was made by transposon insertion in a Klebsiella sp. wild-type strain. In the Dictyostelium growth assay, the mutated microorganism was less virulent compared to an isogenic bacterial strain. The nucleotide sequence immediately following the transposon insertion was cloned and identified as the gene encoding a putative inner membrane protein (VIR46). The insertion site nucleic acid sequence identifying the VIR46 gene in MUT46 is shown in Table 48.
Other Pseudomonas sp. and Klebsiella sp. and many other microbes, including gram-negative bacterial strains, are likely to include virulence genes encoding VIRX-related peptides or proteins having amino acid sequence identity or similarity to those identified herein. Suitable bacterial pathogens may include, but are not limited to, Pneumococci sp., Klebsiella, sp., Pseudomonas , e.g., P. aeruginosa, Salmonella, e.g., Salmonella typhimurium, Legionella, e.g., Legionella pneumophilia, Escherichia, e.g., Escherichia coli, Listeria, e.g., Listeria monocytogenes, Staphylococcus, e.g., Staphylococcus aureus, Streptococci sp., Vibrio, e.g., Vibrio cholerae. Pathogenic mycobacteria of the present invention may include e.g., Mycobacterium tuberculosis. Pathogenic fungi of the present invention may include, e.g., Candida albicans. Pathogenic unicellular eukaryotic organisms of the present invention may include, e.g., Leishmania donovani.
Having identified VIRX genes according to the invention, it is possible to use the gene sequence to search for related genes or peptides in other microorganisms. This may be carried out by searching in existing databases, e.g., EMBL or GenBank. The levels of identity between gene sequences and levels of identity or similarity between, amino acid sequences can be calculated using known methods. In relation to the present invention, publicly available computer based methods for determining identity and similarity include the BLASTP, BLASTN and FASTA (Atschul et al., J. Molec. Biol., 1990; 215:403-410), the BLASTX program available from NCBI, and the Gap program from Genetics Computer Group, Madison Wis.
Preferably, the peptides that may be useful in the various aspects of the invention have greater than a 40% similarity with the peptides identified herein. More preferably, the peptides have greater than 60% sequence similarity. Most preferably, the peptides have greater than 80% sequence similarity, e.g., 95% similarity. With regard to the polynucleotide sequences identified herein, related polynucleotides that may be useful in the various aspects of the invention may have greater than 40% identity with the sequences identified herein. More preferably, the polynucleotide sequences have greater than 60% sequence identity. Most preferably, the polynucleotide sequences have greater than 80% sequence identity, e.g., 95% identity.
In addition to related molecules from other microorganisms, the invention encompasses modifications made to the peptides and polynucleotides identified herein which do not significantly alter the biological function. It will be apparent to the artisan that the degeneracy of the genetic code can result in polynucleotides with minor base changes from those specified herein, but which nevertheless encode the same peptides. Complementary polynucleotides are also within the invention. Conservative replacements at the amino acid level are also envisaged, i.e., different acidic or basic amino acids may be substituted without substantial loss of function.
It is recognized in the art that highly refined mechanisms that regulate transcription have evolved and are present in bacteria. Most bacterial genes are organized into operons, which are groups of genes coding for related proteins. Operons can either be repressed or induced thus regulating those genes. An operon consists of an operator, promoter, regulator, and structural genes. The regulator gene codes for a repressor protein that binds to the operator, obstructing the promoter (thus, transcription) of the structural genes. The regulator does not have to be adjacent to other genes in the operon. If the repressor protein is removed, transcription may occur.
Transposon mutagenesis usually inactivates the gene in which the transposon is inserted, as well as any gene downstream in the same operon. If the VIRX gene is a structural gene in an operon, inactivation of the VIRX gene disrupts the expression of other structural genes in the same operon and positioned downstream of the inactivated VIRX gene. For example, an insertion in pchE gene also inactivates pchF, pchG, pchH, and pchI genes because they all reside within the pchEFGHI operon and are downstream of the inactivated pchE gene. Accordingly, the present invention includes attenuation of virulence due to alteration of a VIRX gene residing in an operon as well as alterations to nucleic acid yielding loss of expression of structural genes located in the same operon and located downstream of the VIRX gene. In one embodiment, the present invention is an alteration inactivating the first gene of an operon carrying a VIRX gene of the invention. The alteration of nucleic acids of VIRX genes and VIRX-containing operons may be insertional inactivation or gene deletion. It is preferred that the alteration of nucleic acids of VIRX genes and VIRX-containing operons be insertional inactivation.
The present invention also provides for a bacterial strain comprising an operon encoding a gene selected from the group consisting of VIR1, VIR2, VIR3, VIR4, VIR5, VIR6, VIR7, VIR8, VIR9, VIR10, VIR11, VIR12, VIR13, VIR14, VIR15, VIR16, VIR17, VIR18, VIR19, VIR20, VIR21, VIR22, VIR23, VIR24, VIR25, VIR26, VIR27, VIR28, VIR29, VIR30, VIR31, VIR32, VIR33, VIR34, VIR35, VIR36, VIR37, VIR38, VIR39, VIR40, VIR41, VIR42, VIR44, VIR45, and VIR46, wherein the bacterial strain includes a mutation that reduces expression of the VIRX gene relative to an isogenic bacterial strain lacking the mutation. In one embodiment, the mutation reduces inhibition of Dictyostelium amoeba growth when compared to the growth of Dictyostelium amoeba in the presence of an isogenic bacterial strain lacking the mutation. In another embodiment, the attenuated bacterial strain has more than one mutation of an operon containing a VIRX gene when compared to an isogenic bacterial strain.
A. Screening
In a separate embodiment, the VIRX genes, or their polynucleotide or polypeptide products disclosed herein is used in screening assays for the identification of potential antimicrobial drugs. Routine screening assays are known to those skilled in the art, and can be adapted using the VIRX products of the invention in the appropriate way. For example, the products of the invention can be used as the target for a potential drug, with the ability of the drug to inactivate or bind to the target indicating its potential antimicrobial activity. In the methods of the present invention, one or more test compounds may be present or produced in the assay mixture. Preferably one compound is present, or produced, in the assay mixture.
B. Character of Antimicrobial Candidate Compositions
VIRX nucleic acids and polypeptides may be used to identify drugs or therapeutics in a candidate composition useful in the prevention or treatment of pathogen-associated disease or infection. A candidate composition can include one or more molecules for analysis in a screening assay and can be a synthetic or semi-synthetic molecules. Such molecules include inorganic as well as organic chemical molecules. The molecules may be less than about 500 Daltons or more than 500 Daltons. The molecules may be naturally occurring. Naturally occurring molecules may include, e.g., saccharides, lipids, peptides, proteins, nucleic acids, or combinations thereof, e.g., aminoglycosides, glycolipids, lipopolysaccharides, or macrolides. Proteins may be immunoglobulins, e.g., polyclonal or monoclonal antibodies. Nucleic acids may be DNA or RNA, e.g., small interfering RNA (siRNA). The precise source of the molecule is not critical to the method of the present invention. The molecule might be derived from e.g., synthetic compounds libraries that are commercially available, e.g., Sigma-Aldrich (Milwaukee, Wis.), or libraries of natural occurring molecules in the form of bacterial, fungal, plant, and animal extracts such as those available from Xenova (Slough, UK). The synthetic (or semi-synthetic) or natural occurring molecules might be modified using standard chemical, physical, or biochemical methods known in the art.
A diagnostic test can assist physicians in determining the type of disease and appropriate associated therapy. As such, a separate embodiment of this invention provides for the use of VIRX genes or their polynucleotides or nucleic acid products as virulence markers for detecting the presence of a pathogen, a pathogen-associated disease, or the virulence of a pathogen. There are many diagnostic assay approaches known to the artisan. Generally, the diagnostic method used would comprise the steps of (a) obtaining a sample from a potentially diseased subject or a diseased subject; (b) measuring the level of at least one polypeptide or polynucleotide virulence marker in the sample; and (c) comparing the amount of the virulence marker in the sample of step (a) to the amount of the virulence marker present in a control sample from a second subject known not to have the presence of the pathogen, where an alteration in the expression level of the virulence marker in the first subject as compared to the control sample indicates the presence of a pathogen, a pathogen-associated disease, or the virulence of a pathogen. Preferably, the subject is a mammal. More preferred is that the subject is a human. The person of skill will recognize that diagnostic tests may be performed in an array-type format wherein, e.g., the presence of two or more VIRX genes or gene products indicate the presence of a pathogen, a pathogen-associated disease, or the virulence of a pathogen.
In another embodiment, the invention provides for the use of the attenuated organisms described herein in vaccine preparation. The preparation of vaccines based on attenuated microorganisms is known to those skilled in the art. Vaccine compositions can be formulated with suitable carriers or adjuvants, e.g., alum, as necessary or desired, to provide effective immunization against infection. The preparation of vaccine formulations will be apparent to the artisan. The attenuated microorganisms may be prepared with a mutation that disrupts the expression of any of the VIRX genes identified herein. The artisan will be aware of methods for disrupting expression of particular VIRX genes. Techniques that may be used include, but are not limited to, insertional inactivation, or gene deletion techniques. Attenuated microorganisms according to the invention may also comprise additional mutations in other genes, for example in a second gene identified herein or in a separate gene required for growth of the microorganism, e.g., an Aro mutation. Attenuated microorganisms may also be used as carrier systems for the delivery of heterologous antigens, therapeutic proteins or nucleic acids (DNA or RNA). In this embodiment, the attenuated microorganisms are used to deliver a heterologous antigen, protein or nucleic acid to a particular site in vivo. Introduction of a heterologous antigen, peptide or nucleic acid into an attenuated microorganism can be carried out by conventional techniques, including the use of recombinant constructs, e.g., vectors, which comprise polynucleotides that express the heterologous antigen or therapeutic protein, and also include suitable promoter sequences. Alternatively, the gene that encodes the heterologous antigen or protein may be incorporated into the genome of the organism and the endogenous promoters used to control expression. In the vaccines of the present invention, the pharmaceutically effective dosage of the mutants of the present invention to be administered may vary depending on the age, weight and sex of the subject, and the mode of administration. The subject can be, e.g., a human, a non-human primate (such as an ape, gorilla, or chimpanzee), cow, horse, pig, sheep, dog, cat, or rodent (including mouse or rat).
As used herein, each of the following terms has the meaning associated with it in this section.
The term “pathogen,” as used herein, is intended to include an agent that causes disease, especially a living microorganism such as a bacterium or fungus. The terms “agent” and “factor” are used interchangeably herein to describe pathogens or toxins useful in the methods of the present invention. Pathogens may include any bacteria, mycobacteria, fungi and unicellular eukaryotic organism, including wild types and mutants thereof, which causes disease or brings about damage or harm to a host organism. Pathogens may also be a poisonous substance, e.g., toxin, which is produced by living cells or organisms and is capable of causing disease when introduced to a host.
The term, “pathogenic,” as used herein, is defined as an agent's ability to cause disease, damage or harm to a host organism.
The term, “attenuated,” as used herein, means an organism made less virulent relative to an isogenic pathogenic organism.
The term, “virulence,” as used herein, is a measure of the degree of pathogenicity of an agent to a host organism. Virulence is usually expressed as the dose of an agent or cell number of a pathogen that will elicit a pathological response in the host organism within a given time period. “Reducing the virulence” as used herein is defined as the ability of a compound to attenuate, diminish, decrease, suppress, or arrest the development of, or the progression of disease, damage or harm to a host organism mediated by a pathogen.
The term, “host organism,” as used herein, is intended to include any living organism. Preferably the host organism is a eukaryote, e.g., vertebrate. More preferably the host organism is a mammal. It is most preferred that the host organism be a human.
The term, “mutant,” as used herein, an organism carrying a specific mutation of a gene that is expressed in the organism's phenotype.
The term, “mutation,” as used herein, is an alteration of one or more nucleic acids of a polynucleotide sequence encoding a gene. A mutation may include the insertion of additional nucleic acids to a polynucleotide sequence encoding a gene, e.g., insertional inactivation of a gene. Alternatively, a mutation may include, but is not limited to, deletion of one or more nulceic acids of a polynucleotide sequence encoding a gene.
The term, “operon,” as used herein, is a unit of bacterial gene expression and regulation comprising several genes usually with complementary functions. Typically an operon includes nucleic acid and control elements in the nucleic acid that may be recognized by regulators of gene products. Insertion in a gene in an operon interferes with the function of this gene and of other genes located downstream or upstream in the operon. It is understood herein that the function attributed to a gene refers to its function and/or that of any gene located downstream or upstream in the same operon.
The term, “pharmaceutically effective dosage,” as used herein, means that amount necessary at least partly to attain the desired effect, or to delay the onset of, inhibit the progression of, or halt altogether, the onset or progression of the particular condition being treated.
The terms “similarity” and “identity” are known in the art. The use of the term “identity” refers to a sequence comparison based on identical matches between correspondingly identical positions in the sequences being compared. The term “similarity” refers to a comparison between amino acid sequences, and takes into account not only identical amino acids in corresponding positions, but also functionally similar amino acids in corresponding positions. Thus similarity between polypeptide sequences indicates functional similarity, in addition to sequence similarity.
From the foregoing detailed description of the specific embodiments of the invention, it should be apparent that bacterial genes have been identified and assigned a new role in virulence. Further, these genes and their products are useful in the identification of antimicrobial agents, the diagnosis of pathogen-associated disease or infection as well as the preparation of vaccines. Although particular embodiments have been disclosed herein in detail, this has been done by way of example for purposes of illustration only, and is not intended to be limiting with respect to the scope of the appended claims that follow. In particular, it is contemplated by the inventor that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims. For instance, the choice of the particular pathogen, or combination of pathogens selected for assay or vaccination, the test conditions used in diagnostic assays utilizing the pathogens of this invention, or the method of mutagenesis used to derive the attenuated mutants is believed to be a matter of routine for a person of ordinary skill in the art with knowledge of the embodiments described herein.
This Example is provided for the purpose of illustration only and the invention should in no way be construed as being limited to these Example, but rather should be construed to encompass any and all variations which become evident as a result of the teaching provided.
The D. discoideum wild-type strain DH1-10 used in these studies is a subclone of DH1 (Cornillon et al., J. Biol. Chem., 275(44):34287-92, 2000). Cells were grown at 21° C. in HL5 medium (14.3 g/l peptone (Oxoid), 7.15 g/l yeast extract, 18 g/l maltose, 0.64 g/l Na2HPO4.2H2O, 0.49 g/l KH2PO4, pH 6.7) (Cornillon et al., J. Cell. Sci., 107 (Pt 10):2691-704, 1994) and subcultured twice a week.
Bacteria were grown overnight at 37° C. on Luria-Bertani (LB) agar. Single colonies were inoculated into 5 ml PB (2% (wt/vol) peptone, 0.3% (wt/vol) MgCl2.6H2O, 1% (wt/vol) K2SO4) (Essar et al., J. Bacteriol., 172(2):884-900,1990) in a 50 ml flask and grown at 37° C. for 8 hr prior to use. The growth of various strains was tested in rich medium (PB) by measuring the optical density (600 nm) of a culture at different times after inoculation and was found to be comparable for all strains used. Under these conditions, similar OD600s were obtained for each strain and the induction of quorum sensing was maximal. Minimal Inhibitory Concentrations (MICs) were determined in Mueller-Hinton broth by the microdilution method (Thornsberry et al., NCCLS, 3: 48-56, 1983). Mutations yielding reduced virulence were identified where the growth of the Dictyostelium test host organism exposed to the mutant pathogen was greater than the Dictyostelium test host organism exposed to wild-type pathogen. Specific genetic mutations in pathogens displaying reduced virulence were identified and characterized by techniques well know in the art.
| Number | Date | Country |
|---|---|---|
| WO 02101081 | Dec 2002 | WO |
| WO 03022881 | Mar 2003 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040122212 A1 | Jun 2004 | US |
