Mechanism of Recovery from Systemic Infection with Vaccinia Virus. III. Effects of Antithymocyte Serum

Treatment with rabbit or horse antiserum to murine thymocytes (antithymocyte serum or ATS) potentiated primary systemic infection with vaccinia virus in mice. Formation of serum neutralizing antibody was suppressed and viremia was prolonged by treatment with ATS. This potentiation of vaccinia virus infection by ATS treatment was largely reversed by passive transfer of physiologic amounts of antibody late in the course of infection, at a time when nonimmunosuppressed mice had neutralizing antibody in their sera. The concentration of interferon in serum was not affected by treatment with ATS. These results suggest a critical role for antibody, but not for cellular immunity, in recovery of mice from primary systemic infection with vaccinia virus.