Recombinant flagellin A proteins from Borrelia burgdorferi sensu stricto, B-afzelii, and B-garinii in serodiagnosis of Lyme borreliosis

Genes for flagellin A (FlaA) proteins from European borrelial strains of Bo rrelia burgdorferi sensu stricto, B. afzelii, and B. garinii were cloned an d sequenced. An identity of 92 to 93% was observed in the flaA sequences of the different species. Polyhistidine-tagged recombinant FlaA (rFlaA) prote ins were produced in Escherichia coli and used as antigens in Western blott ing (WB) and enzyme-linked immunosorbent assay (ELISA). In immunoglobulin G (IgG) WB, 71% (10 of 14) of the sera from neuroborreliosis and 86% (12 of 14) of those from Lyme arthritis patients reacted with one to three rFlaAs. In IgG ELISA, 74% (14 of 19) and 79% (15 of 19) of patients with neuroborr elosis and arthritis, respectively, were positive. The immunoreactivity in local European patient sera was stronger against rFlaA from B. garinii and B. afzelii than against rFlaA from B. burgdorferi sensu stricto. Neither Ig G nor IgM ELISA was sensitive in the serodiagnosis of erythema migrans. Ser um samples from patients with syphilis and systemic lupus erythematosus sho wed mild cross-reactivity in IgG tests. Sera from Yersinia enterocolitica o r beta-hemolytic Streptococcus infections showed only occasional responses. With IgM ELISA, 58% (11 of 19) and 37% (7 of 19) of patients with neurobor reliosis and arthritis, respectively, were positive. Cross-reactive antibod ies to FlaA, especially in serum samples from patients with rheumatoid fact or positivity and Epstein-Barr virus infection, reduced the specificity of IgM serodiagnosis. Therefore, rFlaA seems to have a limited role for IgM se rodiagnosis, yet rFlaA might be useful in the IgG serodiagnosis of dissemin ated Lyme borreliosis.