Abstract
An unusual strain of Borrelia burgdorferi (DN 127 cl 9-2) that was isolated from an Ixodes pacificus tick did not react with monoclonal antibodies (MAbs) to OspA and OspB surface proteins, which are found in most U.S. strains. The strain exhibited an abundant protein with an apparent molecular weight of 25,000 (25K protein). A MAb, 86 DN-1, that was prepared to the 25K protein was used in studies on the effect of proteases on the intact spirochetes, immune electron microscopy, and Western blot (immunoblot) analyses; the results indicated that the low-molecular-weight protein was an apparent surface protein that was loosely attached to the spirochete. Five tick isolates from California possessed low-molecular-weight proteins in the 20,000- to 25,000-molecular-weight range that reacted with the 86 DN-1 MAb. The 25K protein of DN 127 cl 9-2 was unaffected by prolonged in vitro passage of cultures in BSK II medium, while the low-molecular-weight proteins of the other strains of B. burgdorferi from California either decreased in quantity or became undetectable on long-term in vitro passage.