Resolution of experimental and tick-borne Borrelia burgdorferi infection in mice by passive, but not active immunization using recombinant OspC

Vaccination with outer surface protein A (OspA) of Borrelia burgdorferi pre vents subsequent infection and disease in both laboratory animals and human s with high efficacy. OspA-based immunity, however, does not affect establi shed infection due to the loss of OspA expression in the vertebrate host. W e show here that repeated passive transfer of mouse and/or rabbit immune se ra to recombinant GST-OspC fusion protein resulted in a dose-dependent reso lution (1) of fully established arthritis and carditis as well as infection in needle-challenged C.B-17 SCID and (2) of infection in both experimental ly and tick-infected BALB/c mice. Unexpectedly, active immunization of dise ase-susceptible AKR/N mice with GST-OspC only led to prevention but not res olution of disease and infection, in spite of high serum titers of OspC-spe cific Ab and the expression of ospC in tissue-derived spirochetes. The data suggest that the efficacy of OspC antibody-mediated immunity depends on th e immunological history of the recipient and/or environment-dependent regul ation of OspC surface expression by spirochetes in vivo. The results encour age further attempts to develop therapeutic vaccination protocols against L yme disease.