C-terminal invariable domain of VlsE is immunodominant but its antigenicity is scarcely conserved among strains of Lyme disease spirochetes

VlsE, the variable surface antigen of Borrelia burgdorferi, contains two in variable domains located at the amino and carboxyl terminal ends, respectiv ely, and a central variable domain. In this study, both immunogenicity and antigenic conservation of the C-terminal invariable domain were assessed. M ouse antiserum to a 51-mer synthetic peptide (Ct) which reproduced the enti re sequence of the C-terminal invariable domain of VlsE from B. burgdorferi strain B31 was reacted on immunoblots with whole-cell lysates extracted fr om spirochetes of 12 strains from the B. burgdorferi sensu lato species com plex. The antiserum recognized only VlsE from strain B31, indicating that e pitopes of this domain differed among these strains. When Ct was used as en zyme-linked immunosorbent assay (ELISA) antigen, all of the seven monkeys a nd sis mise that were infected with B31 spirochetes produced a strong antib ody response to this peptide, indicating that the CI-terminal invariable do main is immunodominant, None of 12 monkeys and only 11 of 26 mice that nel e infected with strains other than B31 produced a detectable anti-Ct respon se, indicating a limited antigenic conservation. of this domain among these strains. Twenty-six of 33 dogs that were experimentally infected by tick i noculation were positive by the Ct ELISA, while only 5 of 18 serum samples from dogs clinically, diagnosed with Lyme disease contained detectable anti -Ct antibody, Fifty-seven of 64 serum specimens that were collected from Am erican patients with Lyme disease were positive by the Ct ELISA, while only 12 of 21 European samples contained detectable anti-Ct antibody, In contra st, antibody to the mole conserved invariable region IR6 of VlsE was presen t in all of these dog and human serum samples.