Identification of an Immunodominant ABC Transporter in Methicillin-Resistant Staphylococcus aureus Infections

Abstract

Immunoblotting sera from 26 patients with septicemia due to an epidemic strain of methicillin-resistant Staphylococcus aureus (EMRSA-15), 6 of whom died, revealed an immunodominant EMRSA-15 antigen at 61 kDa. There was a statistically significant correlate (P < 0.001) between survival and immunoglobulin G to the 61-kDa band. The antigen was identified by sequencing positive clones obtained by screening a genomic expression library of EMRSA-15 with pooled sera from patients taken after the septicemic episode. Eluted antibody reacted with the 61-kDa antigen on immunoblots. The amino terminus was obtained by searching the S. aureus NCTC 8325 and MRSA strain COL databases, and the whole protein was expressed in Escherichia coli TOP 10F. The derived amino acid sequence showed homology with ABC transporters, with paired Walker A and Walker B motifs and 73% homology to YkpA from Bacillus subtilis. Epitope mapping of the derived amino acid sequence with sera from patients who had recovered from EMRSA-15 septicemia delineated seven epitopes. Three of these epitopes, represented by peptides 1 (KIKVYVGNYDFWYQS), 2 (TVIVVSHDRHFLY NNV), and 3 (TETFLRGFLGRMLFS), were synthesized and used to isolate human recombinant antibodies from a phage antibody display library. Recombinant antibodies against peptides 1 and 2 gave logarithmic reductions in organ colony counts, compared with control groups, in a mouse model of the infection. This study suggests the potential role of an ABC transporter as a target for immunotherapy.

ATP-Binding Cassette Transporters Are Targets for the Development of Antibacterial Vaccines and Therapies

“…Examination of the antibody responses in convalescent-phase sera from individuals that had been infected by vancomycin-resistant Enterococcus faecium led to selection of plasmid DNA clones coding for two amino acid sequences containing ABCs (13). A similar immunoblotting approach with sera from patients with septicemia due to methicillin-resistant S. aureus also resulted in identification of a protein showing homology to ABC transporters (12). In both studies, recombinant antibodies raised against the proteins gave reductions in organ colony counts in mouse models of infection (12,13).…”

Characterization and Evaluation of the Moraxella catarrhalis Oligopeptide Permease A as a Mucosal Vaccine Antigen

“…Immunodominant antigens in bacteria have been considered to have great potential as targets for immunotherapy and have been frequently selected as vaccine antigens (9,46,60). In order to further evaluate OppA as a vaccine antigen, we characterized the immunogenicity of the OppA protein in M. catarrhalis.…”

Protection against heartwater by DNA immunisation with four Ehrlichia ruminantium open reading frames

“…Putative CpG islands with a minimum of 30% GC content were identified in the 1H12 and the WL2AP1 ORFs but not in the WL2HCS1 ORFs. Although none of these putative CpG islands were identical to the CpG motifs previously shown to be stimulatory in sheep [27] and [28], the possibility that these motifs could induce innate immunity cannot be [29]; Enterococcus faecium [30];…”