Passive immunization of hamsters against experimental infection with the Lyme disease spirochete

Hamsters passively immunized with as little as 0.0125 ml of immune rabbit serum (indirect fluorescent-antibody titer, 1:8,192) were protected from challenge with 1,000 50% infective doses of Borrelia burgdorferi. Cross-protection studies with Minnesota and Connecticut isolates of B. burgdorferi indicated no major differences in their capacity to elicit mutually protective antibodies in rabbits.