Immune responses to borrelial VlsE IR6 peptide variants

Laboratory confirmation of Lyme borreliosis (LB) relies mainly on the demonstration of anti-borrelial antibodies. In recent studies, a novel VlsE protein IR6 peptide-based assay has been introduced. Our aim was to evaluate the IR6 peptides from three Borrelia burgdorferi sensu lato genospecies in the serodiagnosis of European and North American patients. Five VlsE protein IR6 peptide variants representing sequences from B. burgdorferi sensu stricto, B. garinii, and B. afzelii were used as antigens in both IgG and IgM enzyme-linked immunosorbent assays (ELISA). Serum antibodies of 187 patients at different stages of LB from Europe and the United States were evaluated for serodiagnosis. For comparison samples were tested with one of the commercial IR6 ELISAs. Three B. afzelii IR6 variant peptides revealed antibodies that were concordant with each other. B. burgdorferi sensu stricto peptide antibodies mostly paralleled B. afzelii peptide antibodies, and positive values were also obtained in the majority of European sera. For several sera, B. garinii IR6 peptide antibodies were discordant to B. afzelii peptide antibodies. The commercial IR6 peptide antibody assay (C6 ELISA) results correlated better with B. burgdorferi sensu stricto IR6 than with B. garinii IR6 peptide IgG results, especially in sera from patients with facial palsy. Thus, antibody specificity to IR6 peptides may vary according to the infecting Borrelia species. In some manifestations of the disease, C6 ELISA may not cover all LB cases. Evidently, the methodological aspects in ELISA design for peptide antibody measurements are important as well as the amino acids sequence of the antigen.