Identification of Antigenic Components of Staphylococcus epidermidis Expressed during Human Infection

Abstract

A spectrum of in vivo-expressed Staphylococcus epidermidis antigens was identified by probing a bacteriophage lambda library of S. epidermidis genomic DNA with human serum from infected and uninfected individuals. This analysis resulted in identification of 53 antigen-encoding loci. Six antigenic polypeptides were expressed from these loci and purified. These polypeptides were the propeptide, mature amidase, and repeat sequence domains of the major autolysin AtlE, GehD (lipase), and two members of a conserved family of surface proteins (ScaA [AaE] and ScaB). AtlE, ScaA, and ScaB all exhibit human ligand binding capacity. Screening a bank of human serum samples revealed that there were significant increases in the amounts of reactive immunoglobulin G in infected individuals compared to the amounts in healthy individuals for the repeat sequence and mature amidase domains of AtlE, ScaB, and GehD. Vaccination of mice with recombinant antigens stimulated an immune response which in vitro opsonized S. epidermidis. In this study we identified prospective candidate antigens for prophylaxis or immunotherapy to control disease.

Type I Signal Peptidase and Protein Secretion inStaphylococcus epidermidis

“…We found that arylomycin C 16 inhibited the secretion of four peptidoglycan hydrolases: AtlE, the SsaA-like protein encoded by SERP0318, SERP2263, and IsaA, making this the major type of protein secreted by S. epidermidis. The autolysin-adhesin AtlE is the major autolysin of S. epidermidis, and it has a well-defined role in virulence (22,49,55) and is also thought to play a role in biofilm formation through its hydrophobicity (22) and its ability to bind various plasma and matrix proteins (22,23,43). The SsaA-like protein encoded by SERP0318 has a C-terminal cysteine-and histidine-dependent aminohydrolase/peptidase (CHAP) domain and two N-terminal LysM peptidoglycan binding domains, which are commonly associated with bacterial cell wall degradation.…”

Functional Role of the PE Domain and Immunogenicity of the Mycobacterium tuberculosis Triacylglycerol Hydrolase LipY

“…Overall, LipY appears to be a B-cell target antigen with apparent diagnostic potential. To the best of our knowledge, humoral responses elicited by bacterial lipases are rather unusual, although some recent reports have suggested that lipases may be immunogenic proteins in Staphylococcus infections (8,33). Therefore, LipY may provide an attractive candidate for future vaccine development in the form of recombinant M. bovis BCG expressing it alone or along with other immunodominant antigens.…”

Virulence of Bacteria Colonizing Vascular Bundles in Ischemic Lower Limbs

“…Staphylococcus epidermidis, usually an innocuous commensal micro-organism on human skin, can cause severe infection after penetration of epidermal barriers. For the most part, this organism lacks components that are easily recognized as virulence factors, such as toxins or aggressive degradative exoenzymes [7]. Interestingly, bacterial isolates from the lymphatics did not have the etaA e toxin gene.…”

“…Thus, the question arose how pathogenic these species can become once they penetrate the epidermis and locate in deep tissues. Bacterial pathogenicity is evoked by the presence of multiple virulence factors encoded by groups of genes present in the chromosome and pathogenicity islands that interact in various combinations [7][8][9].…”