Invasion and cytopathic killing of human lymphocytes by spirochetes causing Lyme disease

Lyme disease is a persistent low-density spirochetosis caused by Borrelia burgdorferi sensu lato. Although spirochetes causing Lyme disease are highly immunogenic in experimental models, the onset of specific antibody responses to infection is often delayed or undetectable in some patients. The properties and mechanisms mediating such immune avoidance remain obscure. To examine the nature and consequences of interactions between Lyme disease spirochetes and immune effector cells, we coincubated B. burgdorferi with primary and cultured human leukocytes. We found that B. burgdorferi actively attaches to, invades, and kills human B and T lymphocytes. Significant killing began within 1 hour of mixing. Cytopathic effects varied with respect to host cell lineage and the species, viability, and degree of attenuation of the spirochetes. Both spirochetal virulence and lymphocytic susceptibility could be phenotypically selected, thus indicating that both bacterial and host cell factors contribute to such interactions. These results suggest that invasion and lysis of lymphocytes may constitute previously unrecognized factors in Lyme disease and bacterial pathogenesis.