A Novel Surface Antigen of Relapsing Fever Spirochetes Can Discriminate between Relapsing Fever and Lyme Borreliosis

In a previous immunoproteome analysis ofBorrelia hermsii , candidate antigens that bound IgM antibodies from mice and patients infected with relapsing fever spirochetes were identified. One candidate that was identified is a hypothetical protein with a molecular mass of 57 kDa that we have designatedBorrelia immunogenic protein A (BipA). This protein was further investigated as a potential diagnostic antigen forB. hermsii given that it is absent from theBorrelia burgdorferi genome. ThebipA locus was amplified and sequenced from 39 isolates ofB. hermsii that had been acquired from western North America.bipA was also expressed as a recombinant fusion protein. Serum samples from mice and patients infected withB. hermsii orB. burgdorferi were used to confirm the immunogenicity of the recombinant protein in patients infected with relapsing fever spirochetes. Lastly,in silico and experimental analysis indicated that BipA is a surface-exposed lipoprotein inB. hermsii . These findings enhance the capabilities of diagnosing infection with relapsing fever spirochetes.