OspA Sequence Comparison and Protection Against Borrelia burgdorferi Infection in Gerbils by Recombinant OspA Protein

Lyme borreliosis is a tick-born disease caused by the spirochete Borr elia burgdorferi. The aim of this research was molecular typing of different strains of B. burgdorferi and protective efficacy of outer surface protein in animal model. Seven strains of B. burgdorferi isolated from skin and CSF of Lyme disease patients were compared using PCR- RFLP as well as DNA and amino acid sequences. The gene coding for Outer Surface Protein A (OspA) was cloned and recombinant protein was expressed. Immunization experiment was conducted on gerbils with purified recombinant OspA protein. The OspA gene sequence of B. afzelii and B. garinii showed 83.76% similarity and calculated amino acid identity of 84 % with each other and 82.5% similarity to B3l strain. OK6 was 100% similar to Pbi, 99.6 % to Ptrob isolate and 88 % to B3 I strain. Cloning and expression of OspA from OK6 strain in E. coli has shown lipoprotein with molecular weight of 32 kDa. Immuno blot of recombinant protein from OK6 with rabbit anti OKI revealed strong reaction with OspA from OK6 strain. Immunization experiment in gerbils with three doses of rOspA protein revealed that all immunized animals either with OspA fusion protein alone or combined with adjuvant were protected against infection with OK1 or OK6 pathogenic strains.