Antibody prevents the establishment of persistent arenavirus infection in synergy with endogenous T cells.

A cardinal feature of the biology of lymphocytic choriomeningitis virus (LCMV) is its ability to establish persistent infections in mice. Persistence is usually established by infection of the mouse during the in utero or neonatal period. Susceptibility can be extended to the adult by treatment with immunosuppressive agents or by infection with immunosuppressive strains of LCMV. In this study we investigated the capacity of passively acquired anti-LCMV antibodies to prevent the establishment of persistence in both neonatal and adult mice. Suckling BALB/c mouse pups nursed by mothers immunized against LCMV before pregnancy had higher survival rates following infection than controls and withstood challenge doses of up to 400 PFU without becoming persistently infected. To establish that maternal antibody alone and not maternally derived T cells provided this protection, nonimmune mothers were infused with monoclonal anti-LCMV neutralizing antibodies within 24 h after delivering their pups. Pups nursing on these passively immunized mothers were resistant to persistent LCMV infection. The establishment of persistence in adult BALB/c mice by the immunosuppressive, macrophage-tropic LCMV variant, clone 13 was also prevented by prophylactic treatment with anti-LCMV monoclonal antibodies. However, the protection afforded by passively acquired antibody was found to be incomplete if the recipients lacked functional CD8+ T cells. While 65% of neonatal athymic (nu/nu) mice nursed by immune nu/+ dams resisted low-dose viral challenge (25 PFU), the majority of nude pups challenged with high doses of virus (100 PFU) became persistently infected. Also, protection was incomplete in beta2-microglobulin knockout mice, which lack functional CD8+ T cells, suggesting that a cooperative effect was exerted by the combination of neutralizing antibody and endogenous T cells. These results indicate that antibodies provide an effective barrier to the establishment of persistent infections in immunocompetent mice and reaffirm that vaccines which induce strong humoral responses may provide efficient protection against arenavirus infections.