Expression and Immunological Analysis of the Plasmid-BornemlpGenes ofBorrelia burgdorferiStrain B31

Abstract

A lipoprotein gene family first identified inBorrelia burgdorferistrain 297, designated 2.9LPand recently renamedmlp, was found on circular and linear plasmids in the genome sequence ofB. burgdorferistrain B31-M1. Sequence analyses of the B31mlpgenes and physically linked variant gene families indicated thatmlpgene heterogeneity is unique and unrelated to location or linkage to divergent sequences. Evidence of recombination between B31mlpalleles was also detected. Northern blot analysis of cultured strain B31 indicated that themlpgenes were not expressed at a temperature (23°C) characteristic of that of ticks in the environment. In striking contrast, expression of manymlpgenes increased substantially when strain B31 was shifted to 35°C, a temperature change mimicking that occurring in the natural transmission cycle of the spirochete from tick to mammal. Primer extension analysis of themlpmRNA transcripts suggested that sigma 70-like promoters are involved inmlpexpression during temperature shift conditions. Antibodies were made against strain B31 Mlp proteins within the first 4 weeks after experimental mouse infection. Importantly, Lyme disease patients also had serum antibodies reactive with purified recombinant Mlp proteins from strain B31, a result indicating that humans are exposed to Mlp proteins during infection. Taken together, the data indicate that strain B31mlpgenes encode a diverse array of lipoproteins which may participate in early infection processes in the mammalian host.