Topical application of Escherichia coli particles over-producing pathogen-derived antigens as a simple vaccination modality in compliance with evolutionary medicine

The development of a new generation of vaccines that can be produced rapidly at low costs and mass-administered noninvasively by non-medical personnel is crucial for boosting vaccine coverage in response to an escalation in demand. The demonstration that topical application of bioengineered nonreplicating Escherichia coli particles overproducing pathogen-derived antigens can mobilize the immune repertoire toward beneficial immune protection against relevant pathogens holds promise for enabling mass-immunization without pain, fear and perceivable tissue damage. Moreover, this noninvasive regimen using E. coli epitopes as a natural adjuvant is in compliance with evolutionary medicine.

[Immunitary response in tuberculosis and the role of Mycobacterium tuberculosis secretion antigens in its protection, pathology and diagnosis. Review]

Tuberculosis (TB) is one of the main causes of death by M. tuberculosis infection in humans worldwide and, it is worrying that the number of cases have been increasing in recent years, largely due to HIV infection. Since the diagnostic methods for detecting the disease are not totally effective because of their lack of specificity and sensitivity, efforts are being made to characterize the M. tuberculosis antigens associated with protection and, thereby develop better diagnostic methods. Among the antigens which are secreted by M. tuberculosis--and which have been described as inducers of the secretion of mediators associated with protection--are CPF-10, ESAT-6, 27 kDa and 38 kDa, which induce the production of IFN-gamma; TNF-alpha and nitric oxide. By means of the study of the functions and composition of these antigens, which are mainly secreted by the bacteria, efforts are being made to find more effective methods of diagnosing the disease in its different stages of evolution. The present review aims to describe the antigens which have been reported as being relevant in the case of M. tuberculosis, since they participate in the immune response to infection and therefore, may be important in terms of diagnosis.

Plant-produced hepatitis B core protein chimera carrying anthrax protective antigen domain-4

The hepatitis B core antigen (HBcAg) can generate a strong immune response and is recognized as an effective carrier for foreign epitopes. The domain-4 epitope of the anthrax protective antigen (PA-D4) plays an essential role in generating protective immunity against virulent Bacillus anthracis. Here we report the successful production of a recombinant protein comprised of the antigenic PA-D4 integrated into the c/e1 loop of HBcAg in transgenic low-alkaloid Nicotiana tabacum. Sera of mice injected with the plant-derived purified HB/PA-D4 protein exhibited significant anti-PA- and anti-HBcAg-specific IgG titers; however, formation of virus-like particles (VLP) was not observed. These data support the feasibility of producing complex protein chimeras in plants.

Transcriptional expression of fljB:z66, a flagellin gene located on a novel linear plasmid of Salmonella enterica serovar Typhi under environmental stresses

A previous study identified that z66+ strain of Salmonella enterica serovar Typhi contains two different flagellin genes, the fliC encoding d or j antigen in chromosome and the fljB-like gene encoding z66 antigen in a novel linear plasmid, respectively. The promoter of fljB:z66 is different from that of fliC:d/j and z66+ strain alters flagellin expression in only one orientation, from z66 to d orj antigen, raising the suspicion that z66+ strain is a special biphasic strain. To clarify the expressional characteristics of flagellin genes of z66+ strain, expression patterns of fljB:z66 and fliC were investigated by RT-PCR under a series of environmental stresses during infection, such as acidic stress, osmotic stress, bile acid stress and oxidative stress. Results showed that the expression level of fljB:z66 is over 10-fold higher than the level of fliC in low and middle osmotic conditions before stresses. Only the expressional regulatory tendency of fljB:z66 in response to bile acid stress is similar to that of fliC. Differential expressional patterns between fljB:z66 and fliC of S. enterica serovar Typhi were seen under osmotic stress, bile acid stress and oxidative stress. These results support the hypothesis that the z66+ strain is a special biphasic strain of S. enterica serovar Typhi.

An inverse relation between CagA+ strains of Helicobacter pylori infection and risk of erosive GERD

OBJECTIVE

The aim of this study is investigating the association of Helicobacter pylori (H. pylori) infection and its cytotoxic-associated gene A (cagA) strain with reflux esophagitis.

METHODS

In a case-control setting (May 2005-2006), patients with reflux esophagitis (case group) were compared with age and gender matched people suffering from symptoms of gastroesophageal reflux disease with normal upper gastrointestinal endoscopic findings (control group) in Imam Khomeini Hospital, Tabriz, Iran. The rates of H. pylori and its cagA positive infections were separately compared between the 2 groups and the subgroups with different severity of reflux esophagitis.

RESULTS

Ninety-two and 93 patients were enrolled in the case and the control groups. The rate of H. pylori infection was insignificantly lower in the case group (81.5% versus 87.10%, p=0.29, odd ratio 0.654, 95% Confidence interval [CI] 0.293 to 1.495). The CagA positive infections were found significantly more frequent in the control group (59.1% versus 40.2%, p=0.01, odd ratio 0.465, 95% CI 0.258 to 0.836). There was no significant difference between the severity subgroups of the disease for H. pylori (p=0.30) or cagA positive infection rates (p=0.40).

CONCLUSION

The CagA positive strains might have a protective effect against reflux esophagitis.

Temperature-induced regulation of RpoS by a small RNA in Borrelia burgdorferi

The alternative sigma factor RpoS (sigma38 or sigmaS) plays a central role in the reciprocal regulation of the virulence-associated major outer surface proteins OspC and OspA in Borrelia burgdorferi, the Lyme disease spirochete. Temperature is one of the key environmental signals controlling RpoS, but the molecular mechanism by which the signal is transduced remains unknown. Herein, we identify and describe a small non-coding RNA, DsrABb, that regulates the temperature-induced increase in RpoS. A novel 5' end of the rpoS mRNA was identified and DsrABb has the potential to extensively base-pair with the upstream region of this rpoS transcript. We demonstrate that B. burgdorferi strains lacking DsrABb do not upregulate RpoS and OspC in response to an increase in temperature, but do regulate RpoS and OspC in response to changes in pH and cell density. Analyses of the rpoS and ospC steady-state mRNA levels in the dsrABb mutant indicate that DsrABb regulates RpoS post-transcriptionally. The 5' and 3' ends of DsrABb were mapped, demonstrating that at least four species exist with sizes ranging from 213 to 352 nucleotides. We hypothesize that DsrABb binds to the upstream region of the rpoS mRNA and stimulates translation by releasing the Shine-Dalgarno sequence and start site from a stable secondary structure. Therefore, we postulate that DsrABb is a molecular thermometer regulating RpoS in Borrelia burgdorferi.

Osmotic regulation of expression of two extracellular matrix-binding proteins and a haemolysin of Leptospira interrogans: differential effects on LigA and Sph2 extracellular release

The life cycle of the pathogen Leptospira interrogans involves stages outside and inside the host. Entry of L. interrogans from moist environments into the host is likely to be accompanied by the induction of genes encoding virulence determinants and the concomitant repression of genes encoding products required for survival outside of the host. The expression of the adhesin LigA, the haemolysin Sph2 (Lk73.5) and the outer-membrane lipoprotein LipL36 of pathogenic Leptospira species have been reported to be regulated by mammalian host signals. A previous study demonstrated that raising the osmolarity of the leptospiral growth medium to physiological levels encountered in the host by addition of various salts enhanced the levels of cell-associated LigA and LigB and extracellular LigA. In this study, we systematically examined the effects of osmotic upshift with ionic and non-ionic solutes on expression of the known mammalian host-regulated leptospiral genes. The levels of cell-associated LigA, LigB and Sph2 increased at physiological osmolarity, whereas LipL36 levels decreased, corresponding to changes in specific transcript levels. These changes in expression occurred irrespective of whether sodium chloride or sucrose was used as the solute. The increase of cellular LigA, LigB and Sph2 protein levels occurred within hours of adding sodium chloride. Extracellular Sph2 levels increased when either sodium chloride or sucrose was added to achieve physiological osmolarity. In contrast, enhanced levels of extracellular LigA were observed only with an increase in ionic strength. These results indicate that the mechanisms for release of LigA and Sph2 differ during host infection. Thus, osmolarity not only affects leptospiral gene expression by affecting transcript levels of putative virulence determinants but also affects the release of such proteins into the surroundings.

Expression and immunogenicity analysis of two iron-regulated outer membrane proteins of Vibrio parahaemolyticus

Genes of two iron-regulated outer membrane proteins of Vibrio parahaemolyticus zj2003, a pathogenic strain isolated from large yellow croaker (Pseudosciaena crocea), psuA and pvuA, were cloned and expressed as N-terminal His(6)-tagged proteins in Escherichia coli BL(21)(DE(3)). The recombinant fusion proteins were purified with nickel chelate affinity chromatography. To analyze the immunogenicity of the proteins, groups of large yellow croaker were immunized with the purified recombinant psuA, pvuA or both, by intraperitoneal injection. Antibody response was assessed by enzyme-linked immunosorbent assay. Titers to the recombinant proteins increased from log(2) 3.25 to log(2) 9.80, 4-8 weeks following immunization. The relative percent survival of the groups vaccinated with psuA, pvuA, or a combination of the two, reached 50%, 62.5% and 75%, respectively. Western blot analysis was carried out with the serum from unvaccinated survival fish after infection. Both recombinant proteins were detected, indicating that these two proteins of V. parahaemolyticus zj2003 were immunogenic and could produce synergistic effects during in vivo infection, and they might be considered as important components for developing an aquaculture vaccine against this pathogen.

Variation of the expression of Mycobacterium tuberculosis ppe44 gene among clinical isolates

PPE44 is a member of the Mycobacterium tuberculosis PPE proteins, a polymorphic family of 69 glycine-rich proteins that predictively represent a source of antigenic variation. The genetic diversity of gene ppe44 among clinical isolates has been studied. No genomic polymorphism of ppe44 was found by a PCR-restriction fragment length polymorphism assay using three restriction enzymes. Nucleotide sequencing of gene ppe44 of a number of isolates, selected to represent the major phylogenetic lineages of M. tuberculosis, showed no nucleotide substitution, with the exception of isolates of the Beijing genotype. These findings indicate that gene ppe44 is basically conserved among M. tuberculosis strains. The expression of gene ppe44 was then determined at the transcriptional level by a real-time reverse transcriptase PCR assay. Extremely high quantitative variations in ppe44 expression were found among the isolates; ppe44 expression of the Beijing strains was significantly higher than the non-Beijing strains. To test whether differential expression of gene ppe44 has the potential to provide a dynamic antigen display, antibodies to PPE44 were titered in the sera of M. tuberculosis-infected subjects. Variation of antibody response to PPE44 was found with regard to both antibody titers and the proportion of responding subjects. These results indicate that the differential expression of genes ppe could influence the host's immune responsiveness, thus having implications in the immunopathogenesis of tuberculosis.

Isolation and purification of recombinant outer surface protein C (rOspC) of Borrelia burgdorferi sensu lato

The aim of this work was isolation and purification of the major immunodominant protein, Outer surface protein C (OspC) of three members of the species group Borrelia burgdorferi, the causative agent of Lyme disease. Our aim was to obtain this protein in a quantity and purity sufficient for immunization of experimental animals. For optimalization of protein purification's yield we used immobilized metal ion affinity chromatography (IMAC) under different conditions. The greatest efficiency was achieved by using of HiTrap Chelating Column under native conditions.

Expression and bioactivity analysis of Staphylococcal enterotoxin M and N

Staphylococcal enterotoxins (SEs) are powerful superantigens that stimulate non-specific T-cell proliferation produced by Staphylococcus aureus and draw considerable attention as ideal drugs for cancer therapy. The filtrate of S. aureus culture has been used as ampul named Staphylococcal enterotoxin C injection in clinic for 10 years in China and proved to be effective. The superantigen SEC claimed to be the only active component without certifiable evidences. For further investigations of the active components of this injection and establishment of foundations for the development of novel anti-cancer drugs, in this research we extracted total DNA from S. aureus (FRI 1230), cloned, expressed and purified recombinant proteins of Staphylococcal enterotoxin M and N (rSEM and rSEN). The MTT assay of the purified rSEM and rSEN demonstrated that their abilities of stimulating T cells and inhibiting the proliferation of K562-ADM cells and B16 cells were equivalent to that of purified SEC2 in vitro. These findings suggested that SEC was not the only active component of Staphylococcal enterotoxin C injection and the effective procedure of expression and purification may be useful for mass productions of these therapeutically important proteins.

Expression of Helicobacter pylori virulence factors and associated expression profiles of inflammatory genes in the human gastric mucosa

Helicobacter pylori virulence factors have been suggested to be important in determining the outcome of infection. The H. pylori adhesion protein BabA2 is thought to play a crucial role in bacterial colonization and in induction of severe gastric inflammation, particularly in combination with expression of CagA and VacA. However, the influence of these virulence factors on the pathogenesis of H. pylori infection is still poorly understood. To address this question, the inflammatory gene expression profiles for two groups of patients infected with triple-negative strains (lacking expression of cagA, babA2, and vacAs1 but expressing vacAs2) and triple-positive strains (expressing cagA, vacAs1, and babA2 but lacking expression of vacAs2) were investigated. The gene expression patterns in the antrum gastric mucosa from patients infected with different H. pylori strains were very similar, and no differentially expressed genes could be identified by pairwise comparisons. Our data thus suggest that there is a lack of correlation between the host inflammatory responses in the gastric mucosa and expression of the babA2, cagA, and vacAs1 genes.

Differential B-cell responses are induced by Mycobacterium tuberculosis PE antigens Rv1169c, Rv0978c, and Rv1818c

The multigene PE and PPE family represents about 10% of the genome of Mycobacterium tuberculosis. Here, we report that three members of the PE family, namely, Rv1169c, Rv0978c, and Rv1818c, elicit a strong, but differential, B-cell humoral response among different clinical categories of tuberculosis patients. The study population (n = 211) was comprised of different clinical groups of both adult and child patients: group 1 (n = 94) patients with pulmonary infection, group 2 (n = 30) patients with relapsed infection, group 3 (n = 31) patients with extrapulmonary infections, and clinically healthy donors (n = 56). Among the PE proteins studied, group 1 adult patient sera reacted to Rv1818c and Rv0978c, while Rv1169c elicited immunoreactivity in group 3 children. However, all three PE antigens studied as well as the 19-kDa antigen did not demonstrate humoral reactivity with sera from group 2 patients with relapsed infection. The current study shows that while responsiveness to all three PE antigens is a good marker for M. tuberculosis infection, a strong response to Rv0978c or to Rv1818c by group 1 adult patients with pulmonary infection or largely restricted reactivity to Rv1169c antigen in child patients with extrapulmonary infections offers the possibility of differential utility in the serodiagnosis of tuberculosis.

Uropathogenic Escherichia coli outer membrane antigens expressed during urinary tract infection

Uncomplicated urinary tract infection (UTI) caused by uropathogenic Escherichia coli (UPEC) represents a prevalent and potentially severe infectious disease. In this study, we describe the application of an immunoproteomics approach to vaccine development that has been used successfully to identify vaccine targets in other pathogenic bacteria. Outer membranes were isolated from pyelonephritis strain E. coli CFT073 cultured under conditions that mimic the urinary tract environment, including iron limitation, osmotic stress, human urine, and exposure to uroepithelial cells. To identify antigens that elicit a humoral response during experimental UTI, outer membrane proteins were separated by two-dimensional gel electrophoresis and probed using pooled antisera from 20 CBA/J mice chronically infected with E. coli CFT073. In total, 23 outer membrane antigens, including a novel iron compound receptor, reacted with the antisera and were identified by mass spectrometry. These antigens also included proteins with known roles in UPEC pathogenesis, such as ChuA, IroN, IreA, Iha, IutA, and FliC. These data demonstrate that an antibody response is directed against these virulence-associated factors during UTI. We also show that the genes encoding ChuA, IroN, hypothetical protein c2482, and IutA are significantly more prevalent (P < 0.01) among UPEC strains than among fecal-commensal E. coli isolates. Thus, we suggest that the conserved outer membrane antigens identified in this study could be rational candidates for a UTI vaccine designed to elicit protective immunity against UPEC infection.

Helicobacter pylori infection and chronic immune thrombocytopenic purpura: long-term results of bacterium eradication and association with bacterium virulence profiles

Eradication of Helicobacter pylori may lead to improvement of chronic immune thrombocytopenic purpura (ITP), although its efficacy over time is uncertain. We report the results of H pylori screening and eradication in 75 consecutive adult patients with ITP. We also used molecular methods to investigate lymphocyte clonality and H pylori genotypes in the gastric biopsies from 10 H pylori-positive patients with ITP and 19 H pylori-positive patients without ITP with chronic gastritis. Active H pylori infection was documented in 38 (51%) patients and successfully eradicated in 34 (89%) patients. After a median follow-up of 60 months, a persistent platelet response in 23 (68%) of patients with eradicated infection was observed; 1 relapse occurred. No differences in mucosal B- or T-cell clonalities were observed between patients with ITP and control participants. Of note, the frequency of the H pylori cagA gene (P = .02) and the frequency of concomitant H pylori cagA, vacAs1, and iceA genes (triple-positive strains; P = .015) resulted statistically higher in patients with ITP than in control participants. All asymptomatic H pylori-positive patients with ITP were suffering from chronic gastritis. Our data suggest a sustained platelet recovery in a proportion of patients with ITP by H pylori eradication alone. Overrepresentation of specific H pylori genotypes in ITP suggests a possible role for bacterium-related factors in the disease pathogenesis.

Noncapsulated toxinogenic Bacillus anthracis presents a specific growth and dissemination pattern in naive and protective antigen-immune mice

Bacillus anthracis is a spore-forming bacterium that causes anthrax. B. anthracis has three major virulence factors, namely, lethal toxin, edema toxin, and a poly-gamma-D-glutamic acid capsule. The toxins modulate host immune responses, and the capsule inhibits phagocytosis. With the goal of increasing safety, decreasing security concerns, and taking advantage of mammalian genetic tools and reagents, mouse models of B. anthracis infection have been developed using attenuated bacteria that produce toxins but no capsule. While these models have been useful in studying both toxinogenic infections and antitoxin vaccine efficacy, we questioned whether eliminating the capsule changed bacterial growth and dissemination characteristics. Thus, the progression of infection by toxinogenic noncapsulated B. anthracis was analyzed and compared to that by previously reported nontoxinogenic capsulated bacteria, using in vivo bioluminescence imaging. The influence of immunization with the toxin component protective antigen (PA) on the development of infection was also examined. The toxinogenic noncapsulated bacteria were initially confined to the cutaneous site of infection. Bacteria then progressed to the draining lymph nodes and, finally, late in the infection, to the lungs, kidneys, and frequently the gastrointestinal tract. There was minimal colonization of the spleen. PA immunization reduced bacterial growth from the outset and limited infection to the site of inoculation. These in vivo observations show that dissemination by toxinogenic noncapsulated strains differs markedly from that by nontoxinogenic capsulated strains. Additionally, PA immunization counters bacterial growth and dissemination in vivo from the onset of infection.

Cryo-electron microscopy study of bacteriophage T4 displaying anthrax toxin proteins

The bacteriophage T4 capsid contains two accessory surface proteins, the small outer capsid protein (Soc, 870 copies) and the highly antigenic outer capsid protein (Hoc, 155 copies). As these are dispensable for capsid formation, they can be used for displaying proteins and macromolecular complexes on the T4 capsid surface. Anthrax toxin components were attached to the T4 capsid as a fusion protein of the N-terminal domain of the anthrax lethal factor (LFn) with Soc. The LFn-Soc fusion protein was complexed in vitro with Hoc(-)Soc(-)T4 phage. Subsequently, cleaved anthrax protective antigen heptamers (PA63)(7) were attached to the exposed LFn domains. A cryo-electron microscopy study of the decorated T4 particles shows the complex of PA63 heptamers with LFn-Soc on the phage surface. Although the cryo-electron microscopy reconstruction is unable to differentiate on its own between different proposed models of the anthrax toxin, the density is consistent with a model that had predicted the orientation and position of three LFn molecules bound to one PA63 heptamer.

Regulation of Helicobacter pylori cagA expression in response to salt

Helicobacter pylori infection and a high dietary salt intake are risk factors for the development of gastric adenocarcinoma. In this study, we tested the hypothesis that high salt concentrations might alter gene expression in H. pylori. Transcriptional profiling experiments indicated that the expression of multiple H. pylori genes, including cagA, was regulated in response to the concentrations of sodium chloride present in the bacterial culture medium. Increased expression of cagA in response to high salt conditions was confirmed by the use of transcriptional reporter strains and by immunoblotting. H. pylori CagA is translocated into gastric epithelial cells via a type IV secretion pathway, and on entry into target cells, CagA undergoes tyrosine phosphorylation and causes multiple cellular alterations. Coculture of gastric epithelial cells with H. pylori grown under high salt conditions resulted in increased tyrosine-phosphorylated CagA and increased secretion of interleukin-8 by the epithelial cells compared with coculture of the cells with H. pylori grown under low salt conditions. Up-regulation of H. pylori cagA expression in response to high salt concentrations may be a factor that contributes to the development of gastric adenocarcinoma.

Cloning and expression of protective antigens of Mycobacterium tuberculosis Ag85B and ESAT-6 in Francisella tularensis 15/10

The possibility of expression of genes encoding mycobacterial antigens in Francisella tularensis 15/10 vaccine strain cells has been shown for the first time. To obtain stable and effective expression of mycobacterial antigens in the F. tularensis cells, the plasmid vector pPMC1 and hybrid genes consisting of the leader part FL of the F. tularensis membrane protein FopA and structural moieties of the mature protein Ag85B or the fused protein Ag85B-ESAT-6 were constructed. Recombinant strains F. tularensis RVp17 and RVp18 expressing protective mycobacterial antigens in the fused proteins FL-Ag85B and FL-Ag85B-ESAT-6, respectively, were obtained. Expression of the protective mycobacterial antigens in F. tularensis was analyzed using specific antisera to the recombinant proteins Ag85-(His)6 and ESAT-6-(His)6 isolated from Escherichia coli producer strains created on the basis of the pET23b(+) and pET24b(+) vectors. The expression of heterologous protective antigens in F. tularensis 15/10 is promising for creation of live recombinant anti-tuberculosis vaccines on the basis of the tularemia vaccine strain.

Production of mouse monoclonal antibodies against Helicobacter pylori Lpp20 and mapping the antigenic epitope by phage display library

Lpp20, an outer membrane protein of Helicobacter pylori (H. pylori), has been identified as an immunodominant antigen. To obtain mouse monoclonal antibodies (mAbs) against it and to map its antigenic epitope is potentially to develop a vaccine for prevention and treatment of H. pylori infection. In our study, the Lpp20 gene was obtained from H. pylori genomic DNA by PCR (GenBank accession no. DQ106902), cloned into pGEX-4T-1 vector and expressed in Escherichia coli (E. coli) as a recombinant fusion protein with glutathione-S-transferase (GST), which was purified by GST-affinity chromatography. mAbs were produced by the hybridoma technique using Lpp20-GST as the immunogen. Using mAb as the target molecule and immunoscreening phage-displayed random dodecapeptide library (Ph.D.-12), the positive phage clones were sequenced and analyzed. Phage clones were chosen to immunize mice to evaluate the potential of phagotopes as effective vaccines. One mimotope (SWPLYSDASGLG) showed a good match with the Lpp20 proteins at 114-117aa (DASG) and the serum of mice induced by the phage clone clearly recognized Lpp20 protein. Our work suggests that the antigenic epitope could be mapped through screening the phage-displayed peptide libraries with mAb and a mimotope of Lpp20 providing an alternative approach for the diagnosis and development of a vaccine for H. pylori.

Evaluation of different promoter sequences and antigen sorting signals on the immunogenicity of Bacillus subtilis vaccine vehicles

Recombinant Bacillus subtilis strains, either in the form of spores or vegetative cells, may be employed as safe and low-cost vaccine vehicles. In this study, we studied the role of promoter sequences and antigen-sorting signals on the immunogenicity based on previously constructed B. subtilis episomal expression systems. Mice orally immunized with spores or cells encoding the B subunit of the heat labile toxin (LTB), originally expressed by some enterotoxigenic Escherichia coli (ETEC) strains, under control of the stress-inducible gsiB promoter developed higher anti-LTB serum IgG and fecal IgA responses with regard to vaccine strains transformed with plasmids encoding the antigen under control of IPTG-inducible (Pspac) or constitutive (PlepA) promoters. Moreover, surface expression of the vaccine antigen under the control of the PgsiB promoter enhanced the immunogenicity of vegetative cells, while intracellular accumulation of LTB led to higher antibody responses in mice orally immunized with recombinant B. subtilis spores. Specific anti-LTB antibodies raised in vaccinated mice recognized and neutralized in vitro the native toxin produced by ETEC strains. Nonetheless, only mice orally immunized with recombinant B. subtilis strains, either as vegetative cells or spores, expressing intracellular LTB under the control of the gsiB promoter conferred partial protection to lethal challenges with purified LT. The present report further demonstrates that B. subtilis plasmid-based heterologous protein expression systems are adequate for antigen delivery via the oral route.

[Construction and expression of the prokaryotic expression vector of MTB cfpl0-esat6 fusion gene]

To begin with, we constructed cfp10-esat6 fusion gene and its prokaryotic expression vector and had it express in E. coli. By GeneSOEing techniques, a fusion gene was constructed by splicing cfpl0 gene and esat6 gene, and then was cloned into pGEX-4T-1 plasmid. Secondly, we constructed the prokaryotic expression recombinant plasmid pGcfp10-esat6. After identification with restriction enzyme analysis, PCR and nucleotide sequencing analysis, The E. coli BL21 containing the recombinant plasmid was induced by IPTG (Isopropy-beta-D-thiogalatoside). The fusion protein CFP10-ESAT6 with GST-tag about 42 kDa was expressed and purified with GST-fusion protein purification kit,The expression of cfp10-esat6 fusion gene was subsequently detected by SDS-polyacrylamine gel electrophoresis and Western-blot analysis. The sequence of cfp10 and esat6 in recombinant plasmid was consistent with that of GenBank report. The fusion protein existed in cytoplasm in soluble form and represented about 40% total bacterial protein of E. coil. The fusion protein was purified and the purity reached 90%. Its antigenicity was confirmed by Western-blotting. The prokaryotic expression vector (pGcfp1o-esat6) was constructed successfully, and the fusion protein CFP10-ESAT6 was obtained. This study provided an experimental basis for potential application of the recombinant CFP10-ESAT6 in the diagnosis of tuberculosis.

Assembly of the small outer capsid protein, Soc, on bacteriophage T4: a novel system for high density display of multiple large anthrax toxins and foreign proteins on phage capsid

Bacteriophage T4 capsid is a prolate icosahedron composed of the major capsid protein gp23*, the vertex protein gp24*, and the portal protein gp20. Assembled on its surface are 810 molecules of the non-essential small outer capsid protein, Soc (10 kDa), and 155 molecules of the highly antigenic outer capsid protein, Hoc (39 kDa). In this study Soc, a "triplex" protein that stabilizes T4 capsid, is targeted for molecular engineering of T4 particle surface. Using a defined in vitro assembly system, anthrax toxins, protective antigen, lethal factor and their domains, fused to Soc were efficiently displayed on the capsid. Both the N and C termini of the 80 amino acid Soc polypeptide can be simultaneously used to display antigens. Proteins as large as 93 kDa can be stably anchored on the capsid through Soc-capsid interactions. Using both Soc and Hoc, up to 1662 anthrax toxin molecules are assembled on the phage T4 capsid under controlled conditions. We infer from the binding data that a relatively high affinity capsid binding site is located in the middle of the rod-shaped Soc, with the N and C termini facing the 2- and 3-fold symmetry axes of the capsid, respectively. Soc subunits interact at these interfaces, gluing the adjacent capsid protein hexamers and generating a cage-like outer scaffold. Antigen fusion does interfere with the inter-subunit interactions, but these interactions are not essential for capsid binding and antigen display. These features make the T4-Soc platform the most robust phage display system reported to date. The study offers insights into the architectural design of bacteriophage T4 virion, one of the most stable viruses known, and how its capsid surface can be engineered for novel applications in basic molecular biology and biotechnology.

Sequence and expression of NAPlr is conserved among group A streptococci isolated from patients with acute poststreptococcal glomerulonephritis (APSGN) and non-APSGN

BACKGROUND

The relation of nephritis-associated plasmin receptor (NAPlr) as a nephritogenic antigen in group A streptococci (GAS), to acute poststreptococcal glomerulonephritis (APSGN) and the potential of specific strains to cause APSGN are not fully understood. It would be helpful to determine whether certain GAS strains from APSGN patients specifically express NAPlr and whether strains from non-APSGN patients express lower levels or an altered form of NAPlr.

METHODS

The sequence and levels of expression of NAPlr were assayed for strains of GAS isolated from patients with APSGN, pharyngitis, scarlet fever or toxic shock-like syndrome. Findings were evaluated with respect to naplr gene sequence, expression level of NAPlr, serotype and disease type.

RESULTS

In GAS strains from both APSGN and non-APSGN patients, the naplr gene showed few or no nucleotide alterations, and both types of GAS strains expressed NAPlr in vitro. There were no obvious differences in naplr gene sequence, expression of NAPlr, serotype or disease type between the GAS strains. In addition, groups C and G streptococci also carried a conserved naplr gene and expressed NAPlr in vitro.

CONCLUSIONS

These groups of streptococci that express NAPlr should be associated with APSGN, and this association may be independent of serotype or disease type.

[Optimization of microbial synthesis of recombinant analogs of Treponema pallidum membrane proteins (Tpp17 and Tpp47) and estimation of their immunochemical properties]

Two strains which produce recombinant proteins--analogs of membrane immunodominant epitopes with molecular weights 17 and 47 kDa of Treponema pallidum were constructed on the basis of E. coli recipient BL21 (DE3)-Gold with phage T7RNA-polymerase expression system. The method of mathematical modeling of growth curve was used to determine kinetic parameters which characterized physiological state of the culture producer in the process of fermentation. Results of immunoenzymatic analysis of blood serum samples from patients with syphilis and healthy donors are presented.

Group A streptococcus cell-associated pathogenic proteins as revealed by growth in hyaluronic acid-enriched media

Group A streptococcus (GAS), also know as Streptococcus pyogenes, is a human pathogen and can cause several fatal invasive diseases such as necrotising fasciitis, the so-called flesh-eating disease, and toxic shock syndrome. The destruction of connective tissue and the hyaluronic acid (HA) therein, is a key element of GAS pathogenesis. We therefore propagated GAS in HA-enriched growth media in an attempt to create a simple biological system that could reflect some elements of GAS pathogenesis. Our results show that several recognised virulence factors were up-regulated in HA-enriched media, including the M1 protein, a collagen-like surface protein and the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase, which has been shown to play important roles in streptococcal pathogenesis. Interestingly, two hypothetical proteins of unknown function were also up-regulated and detailed bioinformatics analysis showed that at least one of these hypothetical proteins is likely to be involved in pathogenesis. It was therefore concluded that this simple biological system provided a valuable tool for the identification of potential GAS virulence factors.

[Preparation of E. coli antigens with multi-characters and antibodies in water environment]

In order to establish enzyme-linked immunosorbent assay (ELISA) method to detect E. coli in water environment, E. coli multicharacters antigens in water environment were prepared according to the characters of kinds of E. coli serotypes, including antigen of whole cell, antigen of disrupted whole cell, somatic antigen, flagellar antigen and fimbrial antigen. E. coli polyclonal antibodies were obtained from the New Zealand rabbits immunized with these five antigens, respectively. Antibodies generated in this research are with high titers and good purity, can conjugate with antigens, specifically, stably and strongly. Indirect ELISA shows the titers of antibody of whole cell and antibody of disrupted whole cell are both more than 1 x 10(5), and the antibodies are of good quality. Based on these antibodies, we established indirect ELISA method to detect E. coli in water environment. The result shows that the detection limitation could be 10(4)/L.

Characterization of genetically matched isolates of Campylobacter jejuni reveals that mutations in genes involved in flagellar biosynthesis alter the organism's virulence potential

Phenotypic and genotypic evidence suggests that not all Campylobacter jejuni isolates are pathogenic for humans. We hypothesized that differences in gene content or gene expression alter the degree of pathogenicity of C. jejuni isolates. A C. jejuni isolate (Turkey) recovered from a turkey and a second C. jejuni isolate (CS) recovered from a chicken differed in their degrees of in vitro and in vivo virulence. The C. jejuni Turkey isolate invaded INT 407 human epithelial cells and secreted the Cia (Campylobacter invasion antigen) proteins, while the C. jejuni CS isolate was noninvasive for human epithelial cells and did not secrete the Cia proteins. Newborn piglets inoculated with the C. jejuni Turkey isolate developed more severe clinical signs of campylobacteriosis than piglets inoculated with the C. jejuni CS isolate. Additional work revealed that flagellin was not expressed in the C. jejuni CS isolate. Microarray and real-time reverse transcription-PCR analyses revealed that all flagellar class II genes were significantly downregulated in the C. jejuni CS isolate compared to the C. jejuni Turkey isolate. Finally, nucleotide sequencing of the flgR gene revealed the presence of a single residue that was different in the FlgR proteins of the C. jejuni Turkey and CS isolates. Complementation of the C. jejuni CS isolate with a wild-type copy of the flgR gene restored the isolate's motility. Collectively, these findings support the hypothesis that critical differences in gene content or gene expression can alter the pathogenic potential of C. jejuni isolates.

Comparative analysis of virulence determinants and mass spectral profiles of Finnish and Lithuanian endodontic Enterococcus faecalis isolates

INTRODUCTION

Putative virulence factors of Enterococcus faecalis have been proposed by several workers and, by analogy, these have been linked to strains of endodontic origin. However, their distribution within the cell population is unknown. In the present study, isolates were taken from the dental root canals of two defined human populations, Lithuanian and Finnish, and examined for a range of virulence properties. In addition, surface-associated molecules and intracellular proteins were compared using matrix-assisted laser desorption-ionization/mass spectrometry (MALDI-TOF-MS) and ProteinChip capture/MS (SELDI-TOF-MS), respectively.

METHODS

Twenty-three Lithuanian and 35 Finnish dental root canal isolates were included. The esp, gelE, ace and efaA genes were detected by polymerase chain reaction, and cytolysin and gelatinase phenotypes were determined by hydrolysis of horse blood agar and gelatine agar, respectively. Protein extracts and surface-associated molecules of whole cells were analysed by SELDI-TOF-MS and MALDI-TOF-MS, respectively.

RESULTS

Presence of esp (n = 15), cytolysin (n = 9), ace (n = 55) and efaA (n = 58) was not statistically different in the two samples, whereas gelE and gelatinase production was detected more frequently in the Finnish material (chi-squared, P < 0.01). Analysis of protein profiles by SELDI-TOF-MS showed clustering of cytolysin-producing strains, whereas MALDI-TOF-MS generated profiles that clustered according to the samples' origin and, furthermore, to atypical quinupristin-dalfopristin susceptibility.

CONCLUSION

A high prevalence of virulence factors was demonstrated in both population types. SELDI-TOF-MS and MALDI-TOF-MS proved useful in distinguishing between different E. faecalis phenotypes and they may be useful technologies for elucidating the eco-distribution of E. faecalis in humans.

A plant-produced plague vaccine candidate confers protection to monkeys

Production of vaccine antigens in plants has received considerable attention over the last decade. However, despite many antigens being expressed in plant systems, and promising efficacy data with rodent models, few vaccine candidates have advanced into studies in non-human primates or human clinical trials. Here, we report on the transient expression of the F1 and LcrV antigens of Yersinia pestis in Nicotiana benthamiana. The antigens were expressed as fusions to the thermostable enzyme of Clostridium thermocellum. When administered to Cynomolgus Macaques the purified plant-produced antigens induced serum IgG and IgA responses specific to F1 and LcrV, and conferred complete protection against lethal challenge with Y. pestis. This study clearly demonstrates the efficacy of a plant-produced plague vaccine candidate in a primate model.

Variable expression of immunoreactive surface proteins of Propionibacterium acnes

Despite accumulating data implicating Propionibacterium acnes in a variety of diseases, its precise role in infection remains to be determined. P. acnes antigen-specific CD4(+) T cells are present in early inflamed acne lesions and may be involved in the inflammatory response; however, little is known about the specific antigens involved. In this study, B cell and T cell antigens from P. acnes expression libraries were cloned and evaluated and the four predominant proteins identified were investigated. Two of these antigens share some homology with an M-like protein of Streptococcus equi and have dermatan-sulphate-binding activity (PA-25957 and 5541). The remaining two antigens, PA-21693 and 4687, are similar to the product of the Corynebacterium diphtheriae htaA gene from the hmu ABC transport locus, although only one of these (PA-21693) is encoded within an hmu-like operon and conserved amongst a range of clinical isolates. All four proteins contain an LPXTG motif, although only PA-21693 contains a characteristic sortase-sorting signal. Variation in the expression of PA-4687, 25957 and 5541 is evident amongst clinical isolates and is generated both by frameshifts associated with the putative signal peptide and by variable numbers of repeat regions toward the carboxy-terminus, potentially generating heterogeneity of molecular mass and antigenic variation. In addition, in the case of PA-25957, a frameshift in a C-rich region at the extreme carboxy-terminus eliminates the LPXTG motif in some isolates. For the dermatan-sulphate-binding PA-25957, IgG1 antibody in serum from acne-positive donors was shown to be specific for the amino-terminal region of the protein, which also contains a CD4(+) T cell epitope. In contrast, serum from acne-negative donors shows an IgG2 and IgG3 antibody subclass response to the carboxy-terminal region. These data have implications for the potential role of P. acnes in inflammatory acne and other diseases.

Production profile of the soluble lytic transglycosylase homologue inStaphylococcus aureusduring bacterial proliferation

The immunodominant antigen A, IsaA, of Staphylococcus aureus is considered to be a sequence homologue of gram-negative soluble lytic transglycosylase. Recently, it was reported that IsaA production is probably regulated by the essential two-component regulatory system consisting of YycG and YycF. Therefore, we investigated the isaA expression profile by quantifying its gene products at different stages of bacterial growth. In the culture supernatant, IsaA was detectable in the early exponential growth phase and its concentration constantly increased until the early stationary phase. Cell surface IsaA was mainly found on growing bacteria, and disappeared proportionately with a decline in cell proliferation. On the other hand, the isaA transcript rapidly increased at the beginning of the culture, and then stayed at a constant level until the late exponential growth phase. These findings indicated that isaA gene expression was stimulated during the exponential growth phase and repressed in the stationary phase. Thus, IsaA production was associated with active bacterial growth. Our results support the previous report that isaA expression is regulated by YycF, and also suggest that IsaA is probably involved in bacterial proliferation by residing on the cell wall. We also discuss the possibility that isaA transcription may be controlled by SarA.

Wza: a new structural paradigm for outer membrane secretory proteins?

Gram-negative bacteria need to be able to transport a large variety of macromolecules across their outer membranes. In Escherichia coli, the passage of the group 1 capsular polysaccharide is mediated by an integral outer membrane protein, Wza. The crystal structure of Wza, determined recently, reveals a novel transmembrane alpha-helical barrel and a large central cavity within the core of the vase-shaped protein complex. The structure has similarities with that of the secretin protein, PilQ, which mediates the transition of type IV pili across the outer membrane. We propose that the large internal chamber, which can accommodate the secreted assembled macromolecule, is likely to be a common feature found in other outer membrane proteins involved in secretion processes.

Murine innate immune response to virulent toxigenic and nontoxigenic Bacillus anthracis strains

Effective treatment of anthrax is hampered by our limited understanding of the pathophysiology of Bacillus anthracis infection. We used a genetically complete (pXO1(+) pXO2(+)) virulent B. anthracis strain and four isogenic toxin-null mutants to determine the effects of the anthrax edema toxin (ET; edema factor [EF] plus protective antigen [PA]) and lethal toxin (LT; lethal factor [LF] plus PA) on the host innate response during systemic infection. Using the spleen as an indicator for host response, we found that intravenous inoculation of LT-deficient mutants into C57BL/6 mice significantly increased production of several cytokines over that observed after infection with the parent strain or an EF-deficient mutant. Bacteria producing one or both of the toxins were capable of inducing significant apoptosis of cells present in spleens, whereas apoptosis was greatly reduced in mice infected with nontoxigenic mutants. Mice infected with toxin-producing strains also showed increased splenic neutrophil recruitment compared to mice infected with nontoxigenic strains and neutrophil depletion prior to infection with toxin-producing strains, leading to decreased levels of apoptosis. Together, these studies indicate that anthrax LT suppresses cytokine secretion during infection, but both EF and LF play roles in inducing neutrophil recruitment and enhancing apoptosis. Interestingly, in the absence of LF the effect of EF-induced cell recruitment is further enhanced, perhaps because LF so effectively suppresses the secretion of chemokines.

Characterizing the specific coaggregation between Actinobacillus actinomycetemcomitans serotype c strains and Porphyromonas gingivalis ATCC 33277

A visual coaggregation study showed specific interspecies coaggregation between an Actinobacillus actinomycetemcomitans serotype c strain and Porphyromonas gingivalis strains ATCC 33277 and 381. We mutagenized A. actinomycetemcomitans SUNYaB 67 (serotype c) with transposon IS903phikan and isolated three transposon insertion mutants that had a reduced ability to aggregate with P. gingivalis ATCC 33277. The three transposon insertions in the mutant strains mapped to the genes at ORF12, ORF13 and ORF16 of the gene cluster responsible for producing serotype c-specific polysaccharide antigen (SPA). Western blot analysis with serotype c-specific antibody showed that these strains did not produce the high-molecular-mass smear of SPA. Furthermore, two SPA-deficient mutants and an SPA-producing mutant were constructed. The two SPA-deficient mutants were deficient for ORF12 and ORF14, which are necessary for the synthesis of serotype c-SPA, and the SPA-producing mutant was deficient for ORF17, which is not related to SPA synthesis. The ORF12- and ORF14-deficient mutants showed reduced ability to aggregate with P. gingivalis ATCC 33277, while the ORF17-deficient mutant aggregated with ATCC 33277 to the same extent as wild-type SUNYaB 67. Our findings suggest that serotype c-SPA of A. actinomycetemcomitans mediates coaggregation with P. gingivalis ATCC 33277.

Multiplex-PCR assay for identification of Klebsiella pneumoniae isolates carrying the cps loci for K1 and K2 capsule biosynthesis

Multiplex-PCR assay for identification of Klebsiella pneumoniae isolates carrying gene clusters for biosynthesis of capsular polysaccharide (CPS) types K1 and K2 was developed. Genes wzc and orf10 of the cps cluster were applied as K1 and K2 specific markers respectively. The assay specificity was confirmed using 147 isolates of Klebsiella spp. including 77 K-antigen reference strains. The multiplex-PCR assay was found simple and cost-effective tool for identification of K. pneumoniae clinical isolates of K1 and K2 geno-serotypes.

DNA vaccine using Mycobacterium bovis Ag85B antigen induces partial protection against experimental infection in BALB/c mice

Bovine tuberculosis is a major cause of economic loss in countries where it is endemic, and in some countries, it may be a significant zoonotic disease problem. Therefore, new strategies for vaccine development are required, and among them, genetic immunization has potential value. The main goal of this study was to test the Mycobacterium bovis Ag85B gene as a DNA vaccine following challenge with an M. bovis virulent strain (ATCC 19274). Groups of BALB/c mice (n = 10) were immunized four times intramuscularly with the pCI-Ag85B construct or the pCI vector alone as the control. High titers of total immunoglobulin G (IgG), IgG1, and IgG2a anti-Ag85B were measured in pCI-Ag85B immunized mice when compared to the pCI control group. Regarding cellular immunity, significant levels of gamma interferon (IFN-gamma) (1,100 +/- 157 pg/ml) and tumor necrosis factor alpha (650 +/- 42 pg/ml) but not interleukin-4 were detected in splenocyte culture supernatants of pCI-Ag85B-vaccinated mice following stimulation with recombinant Ag85B. Further, the main source of IFN-gamma is CD8(+) T cells, as demonstrated by intracellular cytokine staining. As far as protection, a significant reduction in bacterial load in spleens (P < 0.05) was detected in pCI-Ag85B-immunized mice compared to the pCI vector control group. The results obtained here suggest that use of the Ag85B DNA vaccine is a promising strategy to control M. bovis infection due to its ability to induce a Th1 type of immune response. However, protective efficacy needs to be improved, since partial protection was achieved in spleens but not in lungs of vaccinated mice.

Cloning, characterization, and expression of Bartonella henselae p26

In order to identify immunoreactive Bartonella henselae proteins, B. henselae antiserum from an experimentally infected cat was used to screen a B. henselae genomic DNA expression library. One immunoreactive phage clone contained a gene (p26) with significant nucleotide identity with orthologs in brucellae, bartonellae, and several plant-associated bacteria. p26 gene sequences from four B. henselae strains, one B. koehlerae strain, and one B. clarridgeiae strain were cloned. Comparative nucleotide sequence analysis showed that p26 is a potential marker for molecular diagnosis of infection, as well as for identification to species level and genotyping of Bartonella sp. isolates. Alignment of the predicted amino acid sequences illustrated conserved putative protein features including a hydrophobic transmembrane region, a peptide cleavage site, and four dominant antigenic sites. Expression of p26 in Escherichia coli produced two proteins (26 and 27.5 kDa), both of which were reactive with feline anti-B. henselae antisera. Furthermore, murine hyperimmune serum raised against either recombinant protein reacted with both proteins. No reactivity to either recombinant protein was detected in nonimmune serum, and reactivity persisted as long as 20 weeks for one cat. The p26 protein product is an immunodominant antigen that is expressed during infection in cats as a preprotein and is subsequently cleaved to form mature P26.

Oral administration of a Salmonella enterica-based vaccine expressing Bacillus anthracis protective antigen confers protection against aerosolized B. anthracis

Bacillus anthracis is the causative agent of anthrax, a disease that affects wildlife, livestock, and humans. Protection against anthrax is primarily afforded by immunity to the B. anthracis protective antigen (PA), particularly PA domains 4 and 1. To further the development of an orally delivered human vaccine for mass vaccination against anthrax, we produced Salmonella enterica serovar Typhimurium expressing full-length PA, PA domains 1 and 4, or PA domain 4 using codon-optimized PA DNA fused to the S. enterica serovar Typhi ClyA and under the control of the ompC promoter. Oral immunization of A/J mice with Salmonella expressing full-length PA protected five of six mice against a challenge with 10(5) CFU of aerosolized B. anthracis STI spores, whereas Salmonella expressing PA domains 1 and 4 provided only 25% protection (two of eight mice), and Salmonella expressing PA domain 4 or a Salmonella-only control afforded no measurable protection. However, a purified recombinant fusion protein of domains 1 and 4 provided 100% protection, and purified recombinant 4 provided protection in three of eight immunized mice. Thus, we demonstrate for the first time the efficacy of an oral S. enterica-based vaccine against aerosolized B. anthracis spores.

[Construction of the recombinant integrating shuttle plasmid with cfpl0-esat6 fusion gene of Mycobacterium tuberculosis and its expression in BCG]

This study was conducted to amplify the cfpl0-esat6 fusion gene by SOE and insert into the integrating shuttle plasmid pMV361 to form the recombinant plasmid. Then another recombinant plasmid was constructed by insertinga-A g signal sequence of BCG. The two recombinant plasmids were introduced into BCG and the induced products from recombinant BCG were analyzed. In conclusion,the successful construction of rBCG expressing the fusion protein CFP10-ESAT6 will be the base of the development of novel Mycobacterium tuberclosis vaccines.

[Influence of cultivation time and composition of growth medium on formation of capsule, quantity and immunological properties of Pasteurella multocida capsular antigen]

Results of study of capsule formation and immunologic properties of capsular antigen of attenuated strain LA-25 of Pasteurella multocida grown on liquid medium from non-food materials and Hottinger's broth depending on cultivation time are presented.

Use of protein microarrays to define the humoral immune response in leprosy patients and identification of disease-state-specific antigenic profiles

Although the global prevalence of leprosy has decreased over the last few decades due to an effective multidrug regimen, large numbers of new cases are still being reported, raising questions as to the ability to identify patients likely to spread disease and the effects of chemotherapy on the overall incidence of leprosy. This can partially be attributed to the lack of diagnostic markers for different clinical states of the disease and the consequent implementation of differential, optimal drug therapeutic strategies. Accordingly, comparative bioinformatics and Mycobacterium leprae protein microarrays were applied to investigate whether leprosy patients with different clinical forms of the disease can be categorized based on differential humoral immune response patterns. Evaluation of sera from 20 clinically diagnosed leprosy patients using native protein and recombinant protein microarrays revealed unique disease-specific, humoral reactivity patterns. Statistical analysis of the serological patterns yielded distinct groups that correlated with phenolic glycolipid I reactivity and clinical diagnosis, thus demonstrating that leprosy patients, including those diagnosed with the paucibacillary, tuberculoid form of disease, can be classified based on humoral reactivity to a subset of M. leprae protein antigens produced in recombinant form.

Mutations in Mycobacterium tuberculosis Rv0444c, the gene encoding anti-SigK, explain high level expression of MPB70 and MPB83 in Mycobacterium bovis

It has recently been advanced that Mycobacterium tuberculosis sigma factor K (SigK) positively regulates expression of the antigenic proteins MPB70 and MPB83. As expression of these proteins differs between M. tuberculosis (low) and Mycobacterium bovis (high), this study set out to determine whether M. bovis lacks a functional SigK repressor (anti-SigK). By comparing genes near sigK in M. tuberculosis H37Rv and M. bovis AF2122/97, we observed that Rv0444c, annotated as unknown function, had variable sequence in M. bovis. Analysis of in vitro mpt70/mpt83 expression and Rv0444c sequencing across M. tuberculosis complex (MTC) members revealed that high-level expression was associated with a mutated Rv0444c. Complementation of M. bovis bacillus Calmette-Guerin Russia, a high producer of MPB70/MPB83, with wild-type Rv0444c resulted in a significant decrease in mpb70/mpb83 expression. Conversely, a M. tuberculosis H37Rv mutant which expressed sigK but not Rv0444c manifested the M. bovis phenotype of high-level MPB70/MPB83 expression. Further support that Rv0444c encodes the anti-SigK was obtained by yeast two-hybrid studies, where the N-terminal region of Rv0444c-encoded protein interacted with SigK. Together these findings indicate that Rv0444c encodes the regulator of SigK (RskA) and mutations in this gene explain high-level MPT70/MPT83 expression by certain MTC members.

Multicomponent anthrax toxin display and delivery using bacteriophage T4

We describe a multicomponent antigen display and delivery system using bacteriophage T4. Two dispensable outer capsid proteins, Hoc (highly antigenic outer capsid protein, 155 copies) and Soc (small outer capsid protein, 810 copies), decorate phage T4 capsid. These proteins bind to the symmetrically localized capsid sites, which appear following prohead assembly and expansion. We hypothesized that multiple antigens fused to Hoc can be displayed on the same capsid and such particles can elicit broad immunological responses. Anthrax toxin proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF), and their functional domains, were fused to Hoc with an N-terminal hexa-histidine tag and the recombinant proteins were over-expressed in E. coli and purified. Using a defined in vitro assembly system, the anthrax-Hoc fusion proteins were efficiently displayed on T4 capsid, either individually or in combinations. All of the 155 Hoc binding sites can be occupied by one antigen, or they can be split among two or more antigens by varying their molar ratio in the binding reaction. Immunization of mice with T4 phage carrying PA, LF, and EF elicited strong antigen-specific antibodies against all antigens as well as lethal toxin neutralization titers. The triple antigen T4 phage elicited stronger PA-specific immune responses than the phage displaying PA alone. These features offer novel avenues to develop customized multicomponent vaccines against anthrax and other pathogenic diseases.

High-resolution characterization of antibody fragment/antigen interactions using Biacore T100

A Biacore T100 optical biosensor was used to characterize the binding kinetics of a panel of antigen binding fragments (Fabs) directed against the PcrV protein from Pseudomonas aeruginosa. PcrV protein forms part of the type III secretion system complex of this opportunistic pathogen. We demonstrate that the biosensor response data for each Fab collected from three different surface densities of the antigen could be fit globally to a simple 1:1 interaction model. Importantly, we found that the Fabs with the slowest dissociation rate provided the best protection in cell cytotoxicity studies. To further characterize the Fab interactions, binding data were automatically acquired at different temperatures and under different buffer conditions. The comprehensive characterization of these Fabs shows how Biacore T100 can be used to complement protein therapeutic discovery programs from basic research to the selection of therapeutic candidates.

The Salmonella enterica serovar Typhi Vi capsule and self-association pili share controls on expression

Salmonella enterica serovar Typhi uses type IVB pili to facilitate eukaryotic cell invasion. Here, we compare environmental and genetic controls on pil operon transcription with those regulating viaB genes required for Vi antigen expression. Transcription of pil occurs only in the late logarithmic and stationary phases of bacterial growth while viaB expression occurs in the logarithmic growth phase. Expression of both viaB and pil was, however, optimal at 100 mM NaCl, and mutations in envZ/ompR, rcsB/rcsC, (but not rcsA), tviA, ihfB or fis affected transcription of both viaB and pil DNA. As both Vi antigen and Type IVB pili facilitate serovar Typhi invasion of human monocytes, an overlap of production controls is logical. It appears that Vi antigen synthesis precedes pilus production.

Expression, limited proteolysis and preliminary crystallographic analysis of IpaD, a component of the Shigella flexneri type III secretion system

IpaD, the putative needle-tip protein of the Shigella flexneri type III secretion system, has been overexpressed and purified. Crystals were grown of the native protein in space group P2(1)2(1)2(1), with unit-cell parameters a = 55.9, b = 100.7, c = 112.0 A, and data were collected to 2.9 A resolution. Analysis of the native Patterson map revealed a peak at 50% of the origin on the Harker section v = 0.5, suggesting twofold non-crystallographic symmetry parallel to the b crystallographic axis. As attempts to derivatize or grow selenomethionine-labelled protein crystals failed, in-drop proteolysis was used to produce new crystal forms. A trace amount of subtilisin Carlsberg was added to IpaD before sparse-matrix screening, resulting in the production of several new crystal forms. This approach produced SeMet-labelled crystals and diffraction data were collected to 3.2 A resolution. The SeMet crystals belong to space group C2, with unit-cell parameters a = 139.4, b = 45.0, c = 99.5 A, beta = 107.9 degrees . An anomalous difference Patterson map revealed peaks on the Harker section v = 0, while the self-rotation function indicates the presence of a twofold noncrystallographic symmetry axis, which is consistent with two molecules per asymmetric unit.

Identification and characterization of an antigen I/II family protein produced by group A Streptococcus

Group A Streptococcus (GAS) is a gram-positive human bacterial pathogen that causes infections ranging in severity from pharyngitis to life-threatening invasive disease, such as necrotizing fasciitis. Serotype M28 strains are consistently isolated from invasive infections, particularly puerperal sepsis, a severe infection that occurs during or after childbirth. We recently sequenced the genome of a serotype M28 GAS strain and discovered a novel 37.4-kb foreign genetic element designated region of difference 2 (RD2). RD2 is similar in gene content and organization to genomic islands found in group B streptococci (GBS), the major cause of neonatal infections. RD2 encodes seven proteins with conventional gram-positive secretion signal sequences, six of which have not been characterized. Herein, we report that one of these six proteins (M28_Spy1325; Spy1325) is a member of the antigen I/II family of cell surface-anchored molecules produced by oral streptococci. PCR and DNA sequence analysis found that Spy1325 is very well conserved in GAS strains of distinct M protein serotypes. As assessed by real-time TaqMan quantitative PCR, the Spy1325 gene was expressed in vitro, and Spy1325 protein was present in culture supernatants and on the GAS cell surface. Western immunoblotting and enzyme-linked immunosorbent assays indicated that Spy1325 was produced by GAS in infected mice and humans. Importantly, the immunization of mice with recombinant Spy1325 fragments conferred protection against GAS-mediated mortality. Similar to other antigen I/II proteins, recombinant Spy1325 bound purified human salivary agglutinin glycoprotein. Spy1325 may represent a shared virulence factor among GAS, GBS, and oral streptococci.

Identification of a novel glycosyltransferase involved in LOS biosynthesis of Moraxella catarrhalis

Moraxella catarrhalis is an important human mucosal pathogen that contributes to otitis media in infants and exacerbates conditions such as chronic obstructive pulmonary disease in the elderly. This study describes the identification of a novel gene, lgt5 that encodes a glycosyltransferase involved in the LOS biosynthesis of M. catarrhalis. Analysis of NMR data of LOS-derived oligosaccharide from a Serotype A lgt5 mutant strain of M. catarrhalis indicate that lgt5 encodes an alpha-(1-->4)-galactosyltransferase.

Vi antigen biosynthesis in Salmonella typhi: characterization of UDP-N-acetylglucosamine C-6 dehydrogenase (TviB) and UDP-N-acetylglucosaminuronic acid C-4 epimerase (TviC)

Vi antigen, the virulence factor of Salmonella typhi, has been used clinically as a molecular vaccine. TviB and TviC are two enzymes involved in the formation of Vi antigen, a linear polymer consisting of alpha-1,4-linked N-acetylgalactosaminuronate. Protein sequence analysis suggests that TviB is a dehydrogenase and TviC is an epimerase. Both enzymes are expected to be NAD(+) dependent. In order to verify their functions, TviB and TviC were cloned, expressed in Escherichia coli, and characterized. The C-terminal His(6)-tagged TviB protein, purified from soluble cell fractions in the presence of 10 mM DTT, shows UDP-N-acetylglucosamine 6-dehydrogenase activity and is capable of catalyzing the conversion of UDP-N-acetylglucosamine (UDP-GlcNAc) to UDP-N-acetylglucosaminuronic acid (UDP-GlcNAcA) with a k(cat) value of 15.5 +/- 1.0 min(-)(1). The K(m) values of TviB for UDP-GlcNAc and NAD(+) are 77 +/- 9 microM and 276 +/- 52 microM, respectively. TviC, purified as C-terminal hexahistidine-tagged protein, shows UDP-GlcNAcA 4-epimerase and UDP-N-acetylgalactosamine (UDP-GalNAc) 4-epimerase activities. The K(m) values of TviC for UDP-GlcNAcA and UDP-N-acetylgalactosaminuronic acid (UDP-GalNAcA) are 20 +/- 1 microM and 42 +/- 2 microM, respectively. The k(cat) value for the conversion of UDP-GlcNAcA to UDP-GalNAcA is 56.8 +/- 0.5 min(-)(1), while that for the reverse reaction is 39.1 +/- 0.6 min(-)(1). These results show that the biosynthesis of Vi antigen is initiated by the TviB-catalyzed oxidation of UDP-GlcNAc to UDP-GalNAc, followed by the TviC-catalyzed epimerization at C-4 to form UDP-GalNAcA, which serves as the building block for the formation of Vi polymer. These results set the stage for future in vitro biosynthesis of Vi antigen. These enzymes may also be drug targets to inhibit Vi antigen production.