Vaccine development for the prevention of staphylococcal mastitis in dairy cows.

Staphylococci are the most common and costly mammary disease of dairy cattle worldwide. Target of RNAIII Activating Protein (TRAP), a membrane associated 167AA protein, is highly conserved among staphylococci and was shown in Staphylococcus aureus to be involved in bacterial stress response. The aims of this study were to test the safety and efficacy of recombinant TRAP (rTRAP) vaccine in dairy animals. The vaccine was safe as 2-3 subcutaneous injections of rTRAP (54-100 µg) with adjuvant ISA 206 to cows and goats did not lead to any abnormal symptoms of sensitivity to the vaccine. The rTRAP vaccine was immunogenic and caused the induction of a humoral immune response that remained high for at least 160 d post second immunization. The rTRAP vaccine was efficacious; at parturition only 13.5% (5/37) heifers in the immunized group were infected with Staphylococcus chromogenes as compared to 42.9% (18/42) in the non-immunized group. Additionally, when cows were immunized in mid-lactation, the difference between somatic cell count (SCC) in immunized and control animals was profound (45 ± 7 vs. 470 ± 194, respectively). At the same time, the difference in milk yield was also evident (48.3 ± 1.4 L d(-1)vs. 44.3 ± 0.9 L d(-1), respectively). Put together, these studies indicate the value of the rTRAP vaccine in preventing new udder infections by staphylococci, which significantly lead to lowered SCC and some increase in milk yield. TRAP is conserved among all strains and species and is constitutively expressed in any strain of S. aureus or CNS tested so far, including those isolated from cows. TRAP may thus serve as a universal anti-staphylococcus vaccine.

YhgC protects Bacillus anthracis from oxidative stress.

Bacillus anthracis can cause lethal inhalational anthrax and can be used as a bioweapon due to its ability to form spores and to survive under various environmental stress conditions. YhgC in bacilli are structural homologues of TRAP, a protein involved in stress response in staphylococci. To test the role of YhgC in B. anthracis, yhgC gene was deleted in B. anthracis strain Sterne and parent and mutant strains tested. Immunolocalization studies indicated that YhgC is clustered both on the cell surface and within the cytoplasm. Phenotypic analyses indicated that YhgC is an important factor for oxidative stress tolerance and for macrophage infection in vitro. Accordingly, transcriptomics studies indicated that yhgC has a profound effect on genes encoding for stress response regulatory proteins where it negatively regulates the expression of genes encoding for Class I and Class III stress response proteins belonging to the regulons hrcA (hrcA, grpE, dnaK, dnaJ, groEL and groES) and ctsR (ctsR, mcsA, mcsB, clpC/mecB, clpP1). Proteomics studies also indicated that YhgC positively regulates the expression of ClpP-2 and camelysin, which are proteins involved in adaptive responses and pathogenesis in various Gram-positive bacteria. Put together, these results suggest that YhgC is important for the survival of B. anthracis under oxidative stress conditions and thus inhibition of YhgC may compromise the ability of the bacteria to survive within the host.

YhgC protects Bacillus anthracis from oxidative stress.

Bacillus anthracis can cause lethal inhalational anthrax and can be used as a bioweapon due to its ability to form spores and to survive under various environmental stress conditions. YhgC in bacilli are structural homologues of TRAP, a protein involved in stress response in staphylococci. To test the role of YhgC in B. anthracis, yhgC gene was deleted in B. anthracis strain Sterne and parent and mutant strains tested. Immunolocalization studies indicated that YhgC is clustered both on the cell surface and within the cytoplasm. Phenotypic analyses indicated that YhgC is an important factor for oxidative stress tolerance and for macrophage infection in vitro. Accordingly, transcriptomics studies indicated that yhgC has a profound effect on genes encoding for stress response regulatory proteins where it negatively regulates the expression of genes encoding for Class I and Class III stress response proteins belonging to the regulons hrcA (hrcA, grpE, dnaK, dnaJ, groEL and groES) and ctsR (ctsR, mcsA, mcsB, clpC/mecB, clpP1). Proteomics studies also indicated that YhgC positively regulates the expression of ClpP-2 and camelysin, which are proteins involved in adaptive responses and pathogenesis in various Gram-positive bacteria. Put together, these results suggest that YhgC is important for the survival of B. anthracis under oxidative stress conditions and thus inhibition of YhgC may compromise the ability of the bacteria to survive within the host.

OpuC--an ABC transporter that is associated with Staphylococcus aureus pathogenesis.

RIP is a novel antibiotic against staphylococci. It acts at least in part by competing with RNAIII activating protein (RAP) by downregulating TRAP histidine phosphorylation, and by downregulating the expression of the acessory gene regulator (agr). While much is known about the function of the agr as a quorum sensing system that regulates virulence, not much is known about TRAP. TRAP is a 167-kDa protein that is highly conserved among staphylococci and is involved in DNA protection from stress. TRAP is membrane-associated but does not have a transmembrane domain, and thus it may be bound to the membrane through other proteins. To search for these proteins, protein-protein interaction studies were carried out using a bacterial two-hybrid system, and OpuCA was discovered as a TRAP-binding protein. OpuCA is an ATP binding-cytoplasmic (ABC) domain of an OpuC ABC transporter. S. aureus OpuC- mutant strain was constructed and shown to be less tolerant to salt stress, and was defective in choline uptake. OpuC- cells were less pathogenic and showed reduced TRAP phosphorylation and agr activity, did not respond to RAP, and were defective in biofilm formation in vitro and in vivo. These results suggest that OpuC acts as a transporter and also plays a role in S. aureus pathogenesis.

TRAP plays a role in stress response in Staphylococcus aureus.

Staphylococci are common pathogens of implant-related infections. RIP is a heptapeptide (YSPWTNF-NH2 ) that was shown to be very effective in preventing and treating antibiotic-resistant staphylococcal infections, in healing polymicrobial wounds, and in enhancing the effect of commonly used antibiotics. How the peptide negatively affects the survival of the bacteria in the host is not yet known. In staphylococci, RIP was shown to suppress toxin production by inhibiting the expression of agr and production of RNAIII. RIP was also shown to suppress the phosphorylation of TRAP (target of RNAIII-activating peptide), whose function was not clear. Here we show that mutant S. aureus TRAP- cells were more sensitive to oxidative stress and had higher rates of spontaneous and adaptive (agr) mutations. Furthermore, recombinant TRAP protected DNA from oxidative damage caused by hydroxyl radicals. Put together, these results suggest that TRAP is involved in DNA protection from stress. RIP may thus suppress pathogenesis through multiple independent molecular mechanisms involving both suppression of virulence and suppression of stress response.

Population-based molecular epidemiology of leprosy in Cebu, Philippines.

To address the persisting problem of leprosy in Cebu, Philippines, we compiled a database of more than 200 patients who attend an established referral skin clinic. We described the patient characteristics in conventional demographic parameters and also applied multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) and single nucleotide polymorphism (SNP) typing for Mycobacterium leprae in biopsied skin lesion samples. These combined approaches revealed that transmission is ongoing, with the affected including the young Cebuano population under 40 years of age in both crowded cities and rural areas of the island. The emergence of multicase families (MCF) is indicative of infection unconstrained by standard care measures. For the SNPs, we designed a low-cost PCR-restriction fragment length polymorphism typing method. MLVA in M. leprae was highly discriminatory in this population yet could retain broad groups, as defined by the more stable SNPs, implying temporal marker stability suitable for interpreting population structures and evolution. The majority of isolates belong to an Asian lineage (SNP type 1), and the rest belong to a putative postcolonial lineage (SNP type 3). Specific alleles at two VNTR loci, (GGT)5 and 21-3, were highly associated with SNP type 3 in this population. MLVA identified M. leprae genotype associations for patients with known epidemiological links such as in MCFs and in some villages. These methods provide a molecular database and a rational framework for targeted approaches to search and confirm leprosy transmission in various scenarios.

Discovery of a quorum-sensing inhibitor of drug-resistant staphylococcal infections by structure-based virtual screening.

Staphylococci are a major health threat because of increasing resistance to antibiotics. An alternative to antibiotic treatment is preventing virulence by inhibition of bacterial cell-to-cell communication using the quorum-sensing inhibitor RNAIII-inhibiting peptide (RIP). In this work, we identified 2',5-di-O-galloyl-d-hamamelose (hamamelitannin) as a nonpeptide analog of RIP by virtual screening of a RIP-based pharmacophore against a database of commercially available small-molecule compounds. Hamamelitannin is a natural product found in the bark of Hamamelis virginiana (witch hazel), and it has no effect on staphylococcal growth in vitro; but like RIP, it does inhibit the quorum-sensing regulator RNAIII. In a rat graft model, hamamelitannin prevented device-associated infections in vivo, including infections caused by methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis strains. These findings suggest that hamamelitannin may be used as a suppressor to staphylococcal infections.

Transcriptional profiling of target of RNAIII-activating protein, a master regulator of staphylococcal virulence.

Staphylococcus aureus is a gram-positive bacterium that is part of the normal healthy flora but that can become virulent and cause infections by producing biofilms and toxins. The production of virulence factors is regulated by cell-cell communication (quorum sensing) through the histidine phosphorylation of target of RNAIII-activating protein (TRAP), which is a 21-kDa protein that is highly conserved among staphylococci. Using microarray analysis, we show here that the expression and phosphorylation of TRAP upregulate the expression of most, if not all, toxins known to date, as well as their global regulator agr. In addition, we show here that the expression and phosphorylation of TRAP are also necessary for the expression of genes known to be necessary for the survival of the bacteria in a biofilm, like arc, pyr, and ure. TRAP is thus demonstrated to be a master regulator of staphylococcal pathogenesis.

Cis-trans isomerase gene in psychrophilic Pseudomonas syringae is constitutively expressed during growth and under conditions of temperature and solvent stress.

In a recent study, we established that psychrophilic Pseudomonas syringae (Lz4W) requires trans-monounsaturated fatty acid for growth at higher temperatures (Kiran et al. in Extremophiles, 2004). It was also demonstrated that the cti gene was highly conserved and exhibited high sequence identity with cti of other Pseudomonas spp. (Kiran et al. in Extremophiles, 2004). Therefore it would be interesting to understand the expression of the cti gene so as to unravel the molecular basis of adaptation of microorganisms to high temperature. In the present study, the expression of cti was monitored by RT-PCR analysis during different growth stages and under conditions of high temperature and solvent stress in P. syringae. Results indicated that the cti gene is constitutively expressed during different stages of growth and the transcript level is unaltered even under conditions of temperature and solvent stress implying that the observed increase in trans-monounsaturated fatty acids (Kiran et al. in Extremophiles, 2004) is not under transcriptional control. A putative promoter present in the intergenic region of the metH and cti gene has also been characterized. The translation start site ATG, the Shine-Dalgarno sequence AGGA and the transcription start site "C" were also identified. These results provide evidence for the first time that the cti gene is constitutively expressed under normal conditions of growth and under conditions of temperature and solvent stress thus implying that the Cti enzyme is post-transcriptionally regulated.