Cellular and humoral immune responses to buffalopox virus in experimentally infected mice and rabbits

The experiments on protective immunity were conducted in a closely bred population of mice which did not show graft versus host reactions. Simultaneous passive transfer of 0.25 ml rabbit anti-buffalopox virus serum and subsequent challenge with 0.05 ml 10(5) TCID100/ml of buffalopox virus (BPV) showed 57.15 and 47.06% protection with a 1:2 and 1:16 dilutions of buffalopox hyperimmune serum 24 h prior to challenge with BPV showed 87.50 and 75.0% protection, respectively. The passive transfer of normal saline or normal rabbit serum did not protect mice against lethal challenge with BPV. The protection conferred by 5.0 x 10(6) and 15.0 x 10(6) spleen cells obtained from immune donor mice was 37.5, 42.85 and 50.0%, respectively. None of the mice that received spleen cells obtained from donors immunized with normal saline emulsified in Freund's incomplete adjuvant survived lethal challenge with BPV. T- and B-cell levels in the peripheral blood of rabbits during the course of BPV infection revealed transient relative lymphopaenia on the 4th, 5th and 7th days post infection. These values returned to normal on the 14th and 21st days post infection. No marked difference in percentage of B cells or absolute B-cell number between control and infected rabbits was found. This study revealed that both cellular and humoral immunity seem to play a role in recovery from BPV infection in mice and rabbits.