A poxvirus of primates. II. Immunology.

OrTeCa poxvirus shares antigens with Yaba virus, as evidenced by two-way crossreactions in complement-fixation and neutralization tests. Antibodies produced by vaccinia and monkeypox viruses showed weak complement-fixation reactions with OrTeCa viral antigen, but neutralization reactions were negative and cross protection in vivo was not demonstrated. OrTeCa and Yaba virus antisera both contained complement-fixing and neutralizing antibodies against swinepox virus, but swinepox antiserum had no antibodies to any other poxvirus. Long-lasting immunity to the OrTeCa pox disease was produced in monkeys and man by spontaneous infection or vaccination with OrTeCa poxvirus. Complement-fixing antibody titers could be measured in convalescence, but tended to drop to low levels or disappear thereafter. In contrast, neutralizing antibody titers remained high for 3 years, and monkeys that were challenged with OrTeCa virus were reFractory to a second infection.