Passive immunization of mice with monoclonal antibodies raised against tick-borne encephalitis virus

Adult Balb/c mice were passively immunized with monoclonal antibodies (100 mu g/mouse) raised against tick-borne encephalitis (TBE) virus then challenged 24 hours later s.c. with 10 LD sub(50) of TBE virus (Neudorfl isolate). None of the mice showed evidence of premature death although all except one of the monoclonal antibodies tested are capable of enhancing the infectivity of TBE virus in the Fc receptor-bearing mouse macrophage-like cell line P 388 D 1. The ability of monoclonal antibodies to neutralize TBE virus in vitro, and to fix complement was examined, and of these properties only a single monoclonal antibody, which was able to neutralize virus, was also able to protect mice against virus challenge.