Shigeru Numakunai

Protective Immunity Against Bovine Leukaemia Virus (BLV) Induced In Carrier Sheep By Inoculation With A Vaccinia Virus-BLV ENV Recombinant: Association With Cell-Mediated Immunity

The effects of vaccination of sheep with a recombinant vaccinia virus (rVV) expressing the bovine leukaemia virus (BLV) envelope glycoprotein (gp60) were studied by determining BLV titres in peripheral blood leukocytes after vaccination and challenge. The proliferation of BLV was suppressed markedly, not only when rVV was inoculated prior to challenge with BLV, but also when it was inoculated after challenge. These results indicate that vaccination with rVV induces protective immunity that can suppress the growth of BLV in carrier animals. Since rVV induced a strong anti-BLV delayed-type hypersensitivity response without producing detectable levels of binding or neutralizing antibodies, and there was no apparent correlation between the humoral immune response and BLV proliferation, a cell-mediated immune response was assumed to play a major role in protective immunity.

Augmentation of Bovine Leukemia Virus (BLV)‐Specific Lymphocyte Proliferation Responses in Ruminants by Inoculation with BLV env‐Recombinant Vaccinia Virus: Their Role in the Suppression of BLV Replication

Lymphocyte proliferation responses were investigated in sheep and cattle, in which the replication of bovine leukemia virus (BLV) had been known to be suppressed by inoculation with recombinant vaccinia virus (rVV) expressing BLV envelope glycoprotein (gp60). Enhanced lymphocyte proliferation responses were observed in animals inoculated with rVV, regardless of whether they were naive or BLV carriers. These responses were roughly inversely correlated to the growth of BLV in the peripheral blood leukocytes. In contrast, there was no apparent correlation between humoral immune response and BLV growth. Based on these results, it was suggested that rVV rendered its suppressive effect of BLV replication primarily via augmentation of cell‐mediated immunity.