Borrelia burgdorferi outer surface protein (osp) B expression independent of ospA.

The outer surface proteins (Osp) A and B are two important lipoproteins of Borrelia burgdorferi, the Lyme disease spirochete. Extensive in vitro studies indicate that ospB shares a common promoter with ospA and thus these two lipoprotein genes are coordinately transcribed. We show here that B. burgdorferi expresses ospB at much higher levels than ospA during experimental murine infection. The ratio of ospA and ospB mRNA transcripts was 3.5:1 in tick-adapted spirochetes while B. burgdorferi matched every ospA mRNA with up to 70 ospB transcripts during murine infection. This was consistent with the analysis of antibody responses to the two lipoproteins, which showed a more frequent OspB response than OspA during chronic murine infection.