Isolation, preliminary chemical characterization, and biological activity of Borrelia burgdorferi peptidoglycan

Peptidoglycan (PG), an essential cell wall polymer of most bacteria, has been isolated from many species of spirochetes. Our interest in the host response to Borrelia burgdorferi led us to isolate and characterize its PG. Extracted cells were solubilized with warm 1% SDS followed by digestion with proteases. Amino acid analysis of the isolated PG demonstrated the presence of alanine, glycine, glutamic acid, and ornithine as occurs in other spirochetes and bacteria. Intense erythematous reactions were observed after id injection of 10 μg of PG into normal human skin. PG was not mitogenic for human peripheral blood mononuclear cells. Murine splenocytes of certain strains responded to the PG, but only at concentrations of 25 μg/ml or more. PG stimulated macrophages to produce interleukin 1. Sixteen μg of PG injected iv into rabbits produced biphasic fevers. These observations on the in vitro and in vivo activities associated with the cellular components of the B. burgdorferi spirochete give further insight to how a small number of invading organisms can cause a multisystemic disease such as Lyme disease.