Biological activity of a peptidoglycan extracted from Leptospira interrogans: in vitro studies.

Peptidoglycan (PG) has been isolated from some species of spirochaetes, including Leptospira interrogans. Although leptospiral PG has been chemically characterized, no study has been carried out on its potential biological activity. Since PG of Treponema and Borrelia is biologically active both in vivo and in vitro, we investigated the capacity of a leptospiral PG preparation to induce relevant biological effects. PG extracted from L. interrogans strain Teramo was mitogenic at 0.1 microgram ml-1 for human peripheral blood mononuclear cells (PBMC) since it increased the PBMC fraction positive for Ki-67, an antigen expressed by human proliferating cells; at 4 micrograms ml-1, PG was able to induce complement consumption and to stimulate leucocyte phagocytosis and the metabolic burst of resting as well as phagocytosing leucocytes. These findings indicate that Leptospira PG may play a role in modulating the immunocompetent cell functions and suggest that PG can contribute to the host response during Leptospira infection.