WO2000078787A1

WO2000078787A1 - ISOLATED GENES FROM VIRULENT GROUP B $i(STREPTOCOCCUS AGALACTIAE)

Info

Publication number: WO2000078787A1
Application number: PCT/US2000/017082
Authority: WO
Inventors: Elisabeth Adderson; John Bohnsack
Original assignee: University Of Utah Research Foundation
Priority date: 1999-06-21
Filing date: 2000-06-21
Publication date: 2000-12-28
Also published as: AU5755500A; WO2000078787A9; WO2000078787A8

Abstract

The present invention relates to the identification and prevention of infections by virulent forms of Group B streptococci. Disclosed herein is the identification of two genes, spb1 and spb2, that are specific to virulent type III-3 GBS. Also disclosed herein are diagnostic methods for detecting virulent GBS infections and methods of immunizing a mammal against these bacteria.

Description

ISOLATED GENES FROM VIRULENT GROUP B STREPTOCOCCUS

AGALACTIAE

1. FTFIT) OF THF. T VFNTTON

The present invention relates to genes isolated from Group B streptococci ("GBS"). More specifically, the present invention relates to genes that are specific to virulent forms of GBS and methods of using such genes and their products for the diagnosis and treatment of GBS infections.

2. TFCFTNTC AT. BACK GROT IND Group B streptococci ("GBS") are a common cause of disease in newborns, pregnant women, and other persons. Common manifestations of these infections include bacteremia, pneumonia, meningitis, endocarditis, and osteoarticular infections. C.J. Baker & M.S. Edwards, Group B Streptococcal Infections, in Infectious Disease of the Fetus and Newborn Infant, 980-1054 (J.S. Remington & J.O. Klein, eds., 1995); P. Munoz et al., Arch Int Med 157:213-216 (1997).

Nearly 3 out of every 1 ,000 children born are infected with an invasive form of GBS disease. While GBS disease is of great concern in neonates, GBS is also an important pathogen in the general population, in which the incidence of invasive GBS disease is nearly 8 in 100,000. Of these infections, the mortality rate can be as high as 30%.

During childbirth, GBS can pass from the mother to the newborn. By one estimate, up to 30% of pregnant women carry GBS at least temporarily in the vagina or rectum without symptoms. Infants born to these women become colonized with GBS during delivery. Baker & Edwards, supra. Aspiration of infected amniotic fluid or vaginal secretions allow GBS to gain access to the lungs. Adhesion to, and invasion of, respiratory epithelium and endothelium appear to be critical factors in early onset neonatal infection. Baker & Edwards, supra; C.E. Rubens et al., J InfDis 164:320-330 (1991). Subsequent steps in infection, such as blood stream invasion and the establishment of metastatic local infections have not been clarified. The pathogenesis of neonatal infection occurring after the first week of life is also not well understood.

Gastrointestinal colonization may be more important than a respiratory focus in late onset neonatal disease. Baker & Edwards, supra. Considerable evidence suggests that invasion of brain microvascular endothelial cells by GBS is the initial step in the pathogenesis of meningitis. GBS are able to invade human brain microvascular endothelial cells and type III GBS, which are responsible for the majority of meningitis, accomplish this 2-6 times more efficiently than other serotypes. V. Nizet et al. Infect Immun 65:5074-5081 (1997).

Because GBS is widely distributed among the population and is an important pathogen in newborns, pregnant women are commonly tested for GBS at 26 to 28 weeks of pregnancy. Much of GBS neonatal disease is preventable by administration of prophylactic antibiotics during labor to women who test positive or display known risk factors. However, these antibiotics programs do not prevent all GBS disease. The programs are deficient for a number of reasons. First, the programs can be inefficient. Second, it is difficult to ensure that all healthcare providers and patients comply with the testing and treatment. And finally, if new serotypes or antibiotic resistance emerges, the antibiotic programs may fail altogether. Currently available tests for GBS are inefficient. These tests may provide false negatives. Furthermore, the tests are not specific to virulent strains of GBS. Thus, antibiotic treatment may be given unnecessarily and add to the problem of antibiotic resistance. Although a vaccine would be advantageous, none are yet commercially available.

Traditionally, GBS have been divided into 9 serotypes according to the immunologic reactivity of the polysaccharide capsule. H.M. Blumberg et al., JInfDis 173: 365-373 (1996). Serotype III GBS cause 60-70% of all infections and almost all meningitis. Baker & Edwards, supra. Type III GBS can be subdivided into three groups of related strains based on the analysis of restriction digest patterns (RDPs) produced by digestion of chromosomal DNA with Hind III and S->e8387 I. Y. Nagano et al., J Med Micro 35:297-303 (1991); S. Takahashi et al., JInfDis 177:1116-1119 (1998). Figure 1 illustrates a comparison of Hind III and Sse8387 I RDP typing of 62 type III isolates from Salt Lake City, Utah and Tokyo, Japan. Isolates were classified into types based on the similarity of the restriction digest patterns produced by Hind III or Sse8387 I digestion of chromosomal DNA. The two methods divided the isolates into RDP types containing exactly the same isolates: III-3 contains isolates 1-41, II-2 contains isolates 42-59, and II- 1 contains isolates 60-62.

Over 90% of invasive type III GBS neonatal disease in Tokyo, Japan and in Salt Lake City, Utah is caused by bacteria from one of three RDP types, termed RDP type III- 3, while RDP type III-2 are significantly more likely to be isolated from vagina than from blood or CSF. These results suggest that this genetically-related cluster of type III-3 GBS are more virulent than III-2 strains and could be responsible for the majority of invasive type III disease globally.

From the foregoing, it will be appreciated that it would be a significant advancement in the art to provide one or more markers that are specific to virulent type πi-3 GBS. It would be a further advancement to provide a method to exploit these markers for clinical identification of virulent type III-3 GBS. It would be a further advancement to provide methods for producing vaccines against type III-3 GBS. Such compositions and methods are disclosed herein.

3. BRIEF SUMMARY OF THE T VFNTTON

The present invention relates to markers specific to type III-3 GBS. These markers, the spbl and spb2 gene products (SEQ ID NO: 2 and SEQ ID NO: 4, respectively), are encoded by the spbl (SEQ ID NO: 1) and spb2 (SEQ ID NO: 3) genes. The invention also provides these genes and gene products in substantially purified form. In certain other embodiments, the present invention relates to recombinant vectors which incorporate the spbl gene or other nucleic acid molecules that code for the spbl gene product. The recombinant vector may be a plasmid. In certain embodiments, the recombinant vector is a prokaryotic or eukaryotic expression vector. In certain preferred embodiments, the nucleic acid molecule is operably linked to a heterologous promoter and/or other expression control elements, such as heterologous enhancers and polyadenylation sequences.

In certain other embodiments, the present invention relates to recombinant vectors which incorporate the spb2 gene or other nucleic acid molecules that code for the spb2 gene product. The recombinant vector may be a plasmid. In certain embodiments, the recombinant vector is a prokaryotic or eukaryotic expression vector. In certain preferred embodiments, the nucleic acid molecule is operably linked to a heterologous promoter and/or other expression control elements.

The present invention also provides host cells comprising the spbl and/or spb2 genes. In other embodiments, a host cell of the present invention comprises nucleic acid molecules that code for the spbl and or spb2 gene products. The host cell may be a prokaryotic or eukaryotic host cell. The present invention also relates to diagnostic methods for determining whether a mammal is infected or colonized by virulent GBS. In certain embodiments, a diagnostic method comprises the steps of (1) collecting a bodily fluid or culture from the mammal and (2) analyzing the bodily fluid or culture for the presence of absence of one or more gene products specific to type III-3 GBS, wherein the presence of one or more gene products specific to type III-3 GBS indicates infection or colonization by virulent GBS. The mammal may be a human. Alternatively, the mammal may be a laboratory, domestic, or agricultural animal. The bodily fluid or culture may be any bodily fluid or culture that is typically analyzed for the presence of bacteria. For example, the bodily fluid or culture may be a vaginal or rectovaginal culture. The bodily fluid or culture may also be a throat culture. The bodily fluid or culture may also be an endotracheal tube aspirant, fluid from a brochioaveloar lavage, or tissue from a lung biopsy. In certain embodiments, the bodily fluid or culture is blood, serum, amniotic fluid, cerebrospinal fluid, or joint fluid. Other sources of material will be apparent to those of skill in the art. In certain embodiments, a diagnostic method of the present invention comprises analyzing a sample for the presence or absence of the spbl and/or spb2 gene product(s). In certain embodiments of a diagnostic method of the present invention, the polymerase chain reaction ("PCR") is used to identify the presence or absence of the spbl and/or spb2 gene(s). In certain other embodiments, antibodies are used to identify the presence or absence of the spbl and/or spb2 gene products. The antibodies may be monoclonal or polyclonal antibodies.

The present invention also relates to GBS vaccines. In certain embodiments, the present invention provides vaccines comprising the spbl gene product, i.e., a protein comprising the amino acid sequence of SEQ ID NO: 2. In certain other embodiments, a vaccine comprises the spb2 gene product, i.e., a protein comprising the amino acid sequence of SEQ ID NO: 4. In certain preferred embodiments, a vaccine comprises both the spbl and spb2 gene products. The vaccine may include an adjuvant, such as alum. In certain other embodiments, the spbl and/or spb2 gene(s) may be introduced into a mammal using either naked DNA or other gene therapy techniques to induce an immune response against type III GBS. The present invention further provides methods of immunizing a mammal against

GBS infection. In certain embodiments, such methods comprise administering to the mammal a vaccine comprising an immuno logically effective amount of a recombinantly produced protein comprising the amino acid sequence of SEQ ID NO: 2. In certain other embodiments, a method of the present invention comprises administering to the mammal a vaccine comprising an immunologically effective amount of a recombinantly produced protein comprising the amino acid sequence of SEQ ID NO: 4. The vaccine may also contain a mixture of the spbl and spb2 gene products. Vaccines used in the methods of the present invention may further comprise an adjuvant, such as alum.

These and other features and advantages of the present invention will become more fully apparent from the following detailed description.

4. ST JMM ARY OF THF PR A VvTNGS

Figure 1 illustrates a comparison of Hindlll and S-.e83871 RDP typing of 62 type III GBS isolates from Salt Lake City, Utah and Tokyo, Japan. Isolates were classified into types based on the similarity of the restriction digest patterns produced by Hindlll or &e83871 digestion of chromosomal DNA. The two methods divided isolates into RDP types containing exactly the same isolates: III-3 contains isolates 1 - 41, III-2 contains isolates 42 - 59, and III-l contains isolates 60 - 62.

Figure 2 illustrates a dot blot hybridization of probe 1 with genomic DNA isolated from type III GBS. 10 μg of genomic DNA from each of 62 type III GBS strains was transferred to nylon membrane. Radiolabeled probe 1 hybridized with DNA from all III- 3 strains (rows A - D) including the original type III-3 strain (well El). The probe failed to hybridize with DNA from III-2 strains (FI - F10, Gl - G7) including the original strain used in the subtraction hybridization (well E10) and III-l strains (wells HI - H3). The same pattern of hybridization was observed using clone 3 and 11 probes.

5. DFTATLFD DESCRIPTION OF THF TNVFNTTON

The present invention relates to the identification and prevention of infections by virulent forms of GBS. The present invention also relates to isolated genes specific to type III-3 GBS. These genes, spbl and spb2, encode the spbl and spb2 gene products. The spbl and spb2 genes or other nuclceic acid moleucles coding for the spbl or spb2 gene products may be incorporated into a recombinant vector using methods known in the art. See, e.g., 1-3 J. Sambrook et al., Molecular Cloning: A Laboratory Manual (2d ed. 1989). Recombinant vectors include any genetic element, such as a plasmid, phage, transposon, cosmid, chromosome, virus, etc., that is capable of replication when associated with the proper control elements and that can transfer gene sequences between cells. Thus, the term includes cloning and expression vehicles.

A nucleic acid molecule of the present invention may be operably linked to expression control sequences, such as heterologous promoters. Examples include, but are not limited to, viral promoters such as the SV40 early promoter and the CMV immediate early promoter region, bacterial promoters, mammalian promoters, inducible promoters, synthetic promoters, hybrid promoters, and the like. Other expression control sequences are known in the art and include polyadenylation signals, transcription termination sequences, upstream regulatory domains, origins of replication, internal ribosome entr - sites ("IRES"), and enhancers. These expression control sequences collectively provide for the replication, transcription and translation of a coding sequence in a recipient cell. Not all of these control sequences need always be present in a recombinant vector, so long as the selected coding sequence is capable of being replicated, transcribed and translated in an appropriate host cell.

Recombinant vectors can be constructed to include selectable markers. Suitable markers include genes which confer antibiotic resistance or sensitivity, or impart color, or change the antigenic characteristics when host cells which have been transfected with the recombinant vectors are grown in an appropriate selective medium. Suitable markers are known to those of skill in the art.

The discovery of type III-3 GBS-specific gene products will allow clinicians to diagnose and treat infection and colonization with virulent GBS. For example, hybridization-based assays may be used to determine whether a GBS isolate is type III-3. Figure 2 illustrates the results of hybridization assays with a III-3-specifιc probe. Likewise, PCR may be used to detect the presence or absence of either the spbl gene or the spb2 gene (or both) in samples from patients. PCR methods are described generally in C.R. Newton & A. Graham, PCR (2nd. ed. 1997); PCR: Essential Techniques (J.F. Burke ed., 1996). Patients who are infected with type III-3 GBS may then receive appropriate antibiotic therapy. Antibodies may also be used to detect the presence or absence of the spbl and/or spb2 gene product(s). Methods for preparing both monoclonal and polyclonal antibodies are described in, e.g., E. Harlow & D. Lane, Antibodies: A Laboratory Manual (1988).

The present invention also relates to methods for producing type III-3 GBS vaccines. See generally Vaccine Protocols (A. Robinson, G.H. Farrar & C.N. Wiblin eds. 1996). In certain embodiments, the spbl and/or spb2 gene product(s) may be used to immunize against GBS. These gene products may be produced in large quantities using techniques that are known in the art. For example, the appropriate gene or genes may be linked to a prokaryotic promoter and expressed in bacteria. The gene products may then be purified using conventional techniques and used to vaccinate at-risk individuals. Alternatively, the appropriate gene or genes may be linked to a eukaryotic promoter and enhancer (e.g., yeast, baculovirus, SV40, etc.) and expressed in an appropriate cell type. The gene products may then be purified using conventional techniques.

The spbl and or spb2 gene products, or immunogenic fragments thereof, may stimulate an immune response when administered to a host. Recombinantly produced proteins are especially desirable, as they can be produced in large amounts and purified. Furthermore, recombinantly produced proteins may be engineered to maximize desirable activities and to minimize unwanted effects.

The recombinantly produced spbl and/or spb2 gene products may be used as carrier proteins for a polysaccharide-protein or oligosaccharide-protein conjugate vaccine. See, e.g., R. Schneerson, et al., Infect Immun 60:3528-3532 (1992) (describing a

P/.ew.ϊ.-.coccw-.-pertussis toxin conjugate vaccine). For example, Haemophilus inβuenzae B vaccines have been produced by conjugating a tetanus toxoid; a Corynebacteriaum toxin, CRM₁₉₇ (which is a mutant diptheria toxin); and a Neisseria outer membrane protein. Oligo- and polysaccharides from GBS might be used in a vaccine. Oligosaccharide- and polysaccharide-protein conjugates alter the immunological properties of the polysaccharide or oligosaccharide and may improve the immune response.

An adjuvant may be used to enhance the immune response to a vaccine containing the spbl and/or spb2 gene products. An adjuvant is any substance that enhances the immune response to an antigen. Without being bound by any particular theory, adjuvants may act by retaining the antigen locally near the site of administration to produce a depot effect, facilitating the slow, sustained release of the antigen to cells of the immune system. Adjuvants may also attract cells of the immune system. Aluminum hydroxide and aluminum phosphate (collectively and commonly referred to as "alum") are routinely used as adjuvants in human and veterinary vaccines. Currently, alum is the only adjuvant licensed for human use, although a number of experimental adjuvants are being tested. The spbl and/or spb2 gene(s) may also be introduced into a mammal using either naked DNA or other gene therapy techniques to induce an immune response against virulent GBS.

All publications, patents, and patent applications cited in this application are hereby incorporated by reference. U.S. Patent Application Serial No. 60/140,084 is hereby incorporated by reference in its entirety.

6. EXAMPLES

The following examples are given to illustrate several embodiments which have been made within the scope of the present invention. It is to be understood that these examples are neither comprehensive nor exhaustive of the many types of embodiments which can be prepared in accordance with the present invention.

Example 1 - Isolation of the spbl and spb2 genes Bacterial factors that contribute to the increased virulence of III-3 strains can be identified by characterizing the differences between the genetic composition of III-3 and III-2 strains. Such genetic differences will be found in the bacterial chromosomes since these strains do not contain plasmids. Takahashi et al., supra.

To identify genes present in virulent type III-3 GBS strains and not in the avirulent type III-2 strains, a modification of the technique described by Lisitsyn et al., Science 259:946-951 (1993), was used. High molecular weight genomic DNA from an invasive RDP type III-3 GBS strain (strain 874391) and a colonizing ("avirulent") RDP type III-2 strain (strain 865043) were prepared by cell lysis with mutanolysin and Proteinase K digestion. Y. Nagano et al., supra. For genetic subtraction, genomic DNA from both strains was digested with Taq I. Taq I-digested DNA from the virulent strain was mixed with two complementary oligonucleotides, TaqA (5'-CTAGGTGGA- TCCTTCGGCAAT-3' (SEQ ID NO: 5)) and TaqB (5'-CGATTGCCGA-3' (SEQ ID NO: 6)), heated to 50° C for 5 minutes, then allowed to cool slowly to 16°C in T4 ligase buffer. Oligonucleotides were ligated to the virulent strain DNA by incubation with 20 units of T4 ligase at 16 °C for 12 hours. After ligation, 500 ng of DNA from the virulent strain, with ligated linkers, and 40 μg of DNA from the avirulent strain, without linkers, was mixed together, denatured by heating, and hybridized at 68 °C for 20 hours.

Ten percent of the resulting hybridization mixture was incubated with Taq DNA polymerase and dNTPs to fill in the ends of annealed virulent strain DNA. The hybridized DNA was amplified by Taq DNA polymerase for 10 cycles using the TaqA oligonucleotide as the forward and reverse amplification primer. After amplification, single stranded products remaining after amplification were digested with mung bean nuclease. Twenty percent of the resulting product was then reamplified for 20 cycles. This process of subtraction followed by PCR amplification results in enhanced amplification of DNA segments from the III-3 strains that do not hybridize with DNA segments from the III-2 strains.

A total of four cycles of subtraction and amplification were carried out using successively smaller quantities of 111-3 specific PCR products. Two pairs of oligonucleotides were used for subtraction, which were alternated with successive rounds of subtraction-amplification. The oligos were TaqA (SEQ ID NO: 5) and TaqB (SEQ ID NO: 6) (the first pair) and TaqE (5'-AGGCAACTGTGCTAACCGAGGGAAT-3' (SEQ ID NO: 7)) and TaqF (5'-CGATTCCCTCG-3' (SEQ ID NO: 8)) (the second pair). The final amplification products were ligated into pBS KS+ vector and transformed into competent XLl-Blue strain E. coli. Thirteen clones were randomly selected for analysis. Cross hybridization studies of the 13 inserts revealed that 6 were unique. These probes were used in slot and dot blot experiments to determine whether subtraction was successful and to identify probes hybridizing with all III-3 strains. Each of the 6 unique probes hybridized with the parental III-3 virulent strain, while none of the probes hybridized with the avirulent III-2 strains. Three of the amplified sequence tags (clones 1, 3 and 11) hybridized with genomic DNA from all 62 type III-3 isolates, but did not hybridize with DNA prepared from the III-2 and III-l isolates.

Figure 2 illustrates a dot blot hybridization of type III GBS genomic DNA hybridized with a clone 1 probe. 10 μg of genomic DNA from each of 62 type III GBS strains was transferred to nylon membrane. Radiolabeled clone 1 probe hybridized with DNA from all III-3 strains (rows A-D) including the original type III-3 strain (well E-1). The probe failed to hybridize with DNA from III-2 strains (F1-F10, G1-G7) including the original strain used in the subtraction hybridization (well E10) and III-l strains (wells Hl- H3). The same pattern of hybridiztion was observed using clone 3 and 11 probes. These data demonstrate the feasibility of identifying genes unique to III-3 strains by this method of PCR-based sub tractive hybridization, and further support the validity of the RDP typing for identifying genetically-related type III GBS.

The three GBS type III-3 -specific sequence tags are short (130-360 bp). To obtain additional sequence information, a genomic GBS III-3 library was constructed. High molecular weight GBS genomic DNA was partially digested with Bgl II and cloned into λ FIX II phage vector. Phage were packaged and the library, consisting of 1.7 x 10⁵ recombinant phage containing inserts with a mean size of about 18 kb (totaling approximately 3 x 10⁹ bp), was amplified once. Multiple plaques hybridizing with each of the III-3 GBS-specific probes were purified for further characterization.

Three overlapping genomic clones hybridizing with probe 1 were identified, with approximate sizes of 9, 22, and 23 kb. Since the boundaries of GBS III-3 specific DNA are not known, smaller fragments were subcloned and the DNA was verified present in virulent GBS strains before proceeding with further characterization. The first segment examined is a 6.4 kb Sal 1-Bgl II fragment. This genomic DNA is present in all RDP type III-3 strains and in none of 17 RDP type III-2 strains.

Over 90% of this genomic DNA fragment has been sequenced and found to contain 5 open reading frames ("ORFs"). Three of these are likely to be authentic genes. They feature ATG start sites, are preceded by potential ribosomal binding sites and, in two cases, stop codons are followed by palindromic sequences that may represent transcriptional terminators. They are relatively short, however, and do not show significant homology at the nucleic acid or amino acid level with sequences registered with Genbank or the available bacterial genome databases.

The two other ORFs appear to be more obvious candidates for virulence genes. The spbl gene includes a 1509 bp ORF that is preceded by a potential ribosomal binding site 10 bases upstream from an ATG start codon. The predicted protein (502 amino acids and Mr 53,446) has the characteristics of a cell wall-bound protein. The N-terminus of the predicted protein is a hydrophilic, basic stretch of 6 amino acids followed by a 23 amino acid hydrophobic, proline-rich core, consistent with a signal peptide. The hydrophilic mature protein terminates in a typical LPXTG (SEQ ID NO: 9) domain that immediately precedes a hydrophobic 20 amino acid core and a short, basic hydrophilic terminus.

The nucleotide sequence is not homologous to sequences of other known bacterial genes. The translated amino acid sequence, however, shares segmental homology with a number of characterized proteins, including the fimbrial type 2 protein of Actinomyces naeslundii (27% identity over 350 amino acids) and the fimbrial type 1 protein of Actinomyces viscosus (25% homology over 420 amino acids), the T6 surface protein of S. pyogenes (23% identity over 359 amino acids), and the hsf (21% identity over 260 amino acids ) and HMW1 adhesins (25% identity over 285 amino acids) of Haemophilus inβuenzae. See M.K. Yeung & J.O. Cisar, J Bacteriol 172:242-2468 (1990); O. Schneewind, et al., J Bacteriol 172:3310-3317 (1990); J.W. St. Geme III, et al., J Bacteriol 178:6281-6287 (1996); J.W. St. Geme III, Infect Immun 62: 3881-3889 (1994). The function of the S. pyogenes T6 protein is unknown. Each of the other homologues plays a role in bacterial adhesion and/or invasion. The second ORF, spb2, terminates 37 bp upstream from spbl and is in the same transcriptional orientation. This 1692 bp ORF has a deduced amino acid sequence of 563 residues and Mr 64,492. It shares 50.5% nucleic acid identity and 20.7% amino acid identity with spbl. Conservation is highest in the carboxy-terminal regions, including a shared LPSTGG (SEQ ID NO: 10) motif. In contrast to spbl, spb2 does not have an obvious signal sequence. Its secretion may be mediated by carboxy-terminal recognition sequences or by accessory peptides. T. Michiels, et al., Infect Immun 58:2840-2849 (1990). The deduced amino acid sequence of spb2 is also homologous with S. pyogenes T6 and Actinomyces naeslundii proteins, and to Listeria monocytogenes internalin A (22% identity over 308 amino acids) — again, proteins important in adhesion and invasion. Neither of the predicted gene products has the repetitive structure of previously described GBS surface proteins such as the C and Rib proteins or of L. monocytogenes internalin family members. L.C. Madoff et al., Infect Immun 59:2638-2644 (1991); J. Gaillard, et al., Cell 65: 1127-1141 (1991). Hybridization of the originating strain 874391 genomic DNA with an spbl probe under low stringency conditions identifies a single band in EcoR I, Sal I and Sst I digests (data not shown), suggesting that a single copy of spbl is present in this strain and that spbl is not a member of a significantly homologous "family" of genes.

Example 2 - Adherence and Invasion Assays Using spbl^' Bacteria

Genomic subtraction identified a 1509 bp ORF, spbl, which is present in virulent RDP type III-3 GBS and not in RDP type III-2 strains. The predicted 53 kD protein product has the characteristics of a typical gram positive cell-wall bound protein. The nucleic acid sequence of spbl is not homologous to sequences of other known bacterial genes, however the translated amino acid sequence shares segmental homology with several characterized adhesins, including Actinomyces fimbrial proteins and H. inβuenzae ΗMW1, suggesting that Spbl might contribute to GBS adhesion or invasion. A spbl^' isogenic deletion mutant GBS strain was created by homologous recombination and the ability of the spbl^' mutant to adhere to and invade A549 respiratory epithelial cells was determined. Compared to the wild type strain, the number of spbl^' bacteria adherent to A549 monolayers was reduced by 60.0% (p<0.01) and the number of intracellular invading bacteria was reduced by 53.6% (p<0.01). Without being bound by any particular theory, it appears that Spbl may contribute to the pathogenesis of GBS pneumonia and bacterial entry into the bloodstream.

Claims

CLAIMS:

1. An isolated nucleic acid molecule comprising nucleotides which code for the amino acid sequence of SEQ ID NO: 2.

2. A recombinant vector comprising the nucleic acid molecule of claim 1.

3. The recombinant vector of claim 2, wherein said recombinant vector is a plasmid.

4. The recombinant vector of claim 2, wherein said recombinant vector is a prokaryotic or eukaryotic expression vector.

5. The recombinant vector of claim 2, wherein the nucleic acid molecule is operably linked to a heterologous promoter.

6. A host cell comprising the nucleic acid molecule of claim 1.

7. The host cell of claim 6, wherein the host cell is a eukaryotic host cell.

8. The host cell of claim 6, wherein the host cell is a prokaryotic host cell.

9. An isolated nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO: l.

10. A recombinant vector comprising the nucleic acid molecule of claim 9.

11. The recombinant vector of claim 10, wherein said recombinant vector is a plasmid.

12. The recombinant vector of claim 10, wherein said recombinant vector is a prokaryotic or eukaryotic expression vector.

13. The recombinant vector of claim 10, wherein the nucleic acid molecule is operably linked to a heterologous promoter.

14. A host cell comprising the nucleic acid molecule of claim 9.

15. The host cell of claim 14, wherein the host cell is a eukaryotic host cell.

16. The host cell of claim 14, wherein the host cell is a prokaryotic host cell.

17. An isolated nucleic acid molecule comprising nucleotides which code for the amino acid sequence of SEQ ID NO: 4

18. A recombinant vector comprising the nucleic acid molecule of claim 17.

19. The recombinant vector of claim 18, wherein said recombinant vector is a plasmid.

20. The recombinant vector of claim 18, wherein said recombinant vector is a prokaryotic or eukaryotic expression vector.

21. The recombinant vector of claim 18, wherein the nucleic acid molecule is operably linked to a heterologous promoter.

22. A host cell comprising the nucleic acid molecule of claim 17.

23. The host cell of claim 22, wherein the host cell is a eukaryotic host cell.

24. The host cell of claim 22, wherein the host cell is a prokaryotic host cell.

25. An isolated nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO: 3.

26. A recombinant vector comprising the nucleic acid molecule of claim 25.

27. The recombinant vector of claim 26, wherein said recombinant vector is a plasmid.

28. The recombinant vector of claim 26, wherein said recombinant vector is a prokaryotic or eukaryotic expression vector.

29. The recombinant vector of claim 26, wherein the nucleic acid molecule is operably linked to a heterologous promoter.

30. A host cell comprising the nucleic acid molecule of claim 25.

31. The host cell of claim 30, wherein the host cell is a eukaryotic host cell.

32. The host cell of claim 30, wherein the host cell is a prokaryotic host cell.

33. A method of immunizing a mammal against Group B streptococci infection, said method comprising administering to the mammal a vaccine comprising an immunologically effective amount of a recombinantly produced protein comprising the amino acid sequence of SEQ ID NO: 2.

34. The method of claim 33, wherein the vaccine further comprises an adjuvant.

35. The method of claim 34, wherein the adjuvant comprises alum.

36. The method of claim 33, wherein the vaccine further comprises an immunologically effective amount of a recombinantly produced protein comprising the amino acid sequence of SEQ ID NO: 4.

37. The method of claim 36, wherein the vaccine further comprises an adjuvant.

38. A method of immunizing a mammal against Group B streptococci infection, said method comprising administering to the mammal a vaccine comprising an immunologically effective amount of a recombinantly produced protein comprising the amino acid sequence of SEQ ID NO: 4.

39. The method of claim 38, wherein the vaccine further comprises an adjuvant.

40. The method of claim 39, wherein the adjuvant comprises alum.

41. A diagnostic method for determining whether a mammal is infected or colonized by virulent Group B streptococci (GBS), said method comprising the steps of:

(a) collecting a bodily fluid or culture from the mammal;

(b) analyzing the bodily fluid or culture for the presence or absence of one or more gene products specific to type III-3 GBS; wherein the presence of one or more gene products specific to type III-3 GBS indicates infection or colonization by virulent GBS.

42. The diagnostic method of claim 41, wherein the one or more gene products specific to type III-3 GBS comprise a protein, said protein comprising the amino acid sequence of SEQ ID NO: 2.

43. The diagnostic method of claim 41, wherein the one or more gene products specific to type III-3 GBS comprise a protein, said protein comprising the amino acid sequence of SEQ ID NO: 4.

44. The diagnostic method of claim 41, wherein the one or more gene products specific to type 111-3 GBS comprise a first protein comprising the amino acid sequence of SEQ ID NO: 2 and a second protein comprising the amino acid sequence of SEQ ID NO: 4.

45. The diagnostic method of claim 41, wherein the mammal is a human.

46. The diagnostic method of claim 41, wherein the bodily fluid or culture is a vaginal or rectovaginal culture.

47. The diagnostic method of claim 41, wherein the bodily fluid or culture is a throat culture.

48. The diagnostic method of claim 41, wherein the bodily fluid or culture is blood, serum, amniotic fluid, cerebrospinal fluid, or joint fluid.

49. The diagnostic method of claim 41, wherein the analysis step comprises using polymerase chain reaction (PCR) to identify the presence or absence of one or more gene products specific to type III-3 GBS.

50. The diagnostic method of claim 49, wherein the analysis step comprises using PCR to determine the presence or absence of the spbl gene product.

51. The diagnostic method of claim 49, wherein the analysis step comprises using PCR to determine the presence or absence of the spb2 gene product.

52. The diagnostic method of claim 41, wherein the analysis step comprises using antibodies to identify the presence or absence of one or more gene products specific to type πi-3 GBS.

53. The diagnostic method of claim 52, wherein the antibodies are monoclonal antibodies.

54. The diagnostic method of claim 53, wherein the monoclonal antibodies are specific for the ->pb7 gene product.

55. The diagnostic method of claim 53, wherein the monoclonal antibodies are specific for the spb2 gene product.

56. An isolated and purified protein comprising the amino acid sequence of SEQ ID NO: 2.

57. A vaccine for immunizing a mammalian host against virulent Group B streptococci infection, said vaccine comprising the protein of claim 56.

58. The vaccine of claim 57, further comprising an adjuvant.

59. The vaccine of claim 58, wherein the adjuvant comprises alum.

60. The vaccine of claim 57, wherein the protein is conjugated to a bacterial polysaccharide or oligosaccharide.

61. An isolated and purified protein comprising the amino acid sequence of SEQ ID NO: 4.

62. A vaccine for immunizing a mammalian host against virulent Group B streptococci infection, said vaccine comprising the protein of claim 61.

63. The vaccine of claim 62, further comprising an adjuvant.

64. The vaccine of claim 63, wherein the adjuvant comprises alum.

65. The vaccine of claim 62, further comprising an isolated and purified protein comprising the amino acid sequence of SEQ ID NO: 2.

66. The vaccine of claim 65, further comprising an adjuvant.

67. The vaccine of claim 62, wherein the protein is conjugated to a bacterial polysaccharide or oligosaccharide.