Study of the antigenic and immunogenic properties of neurovaccinia virus TS mutants

The antigenic and immunogenic properties of five ts mutants of neurovaccinia virus with markedly reduced pathogenicity for laboratory animals as compared with "wild" type virus were studied. The antigenic and immunogenic activities of the mutants correlated with their capacity to reproduce in the skin of the inoculated animals. When similar doses of UV-inactivated mutants were used for immunization of rabbits, significant differences (more than 100-fold) in their antigenic activity were found. When rabbits were immunized with active virus, neutralizing antibody in titer of 1:800 protected all the immunized animals against intracerebral challenge with log 4.0 LD50 of neurovaccinia virus. On the other hand, the neutralizing antibody formed in response to inoculation of UV-inactivated virus did not protect the immunized animals in titers exceeding 1:2560. A correlation between the antibody titer for "extracellular" virus and immunity in vaccinated rabbits has been demonstrated.