Cross-reactive antibodies to BLV and HTLV in bovine and human hosts with retrovirus infection

Sera of 22 cattle naturally infected with bovine leukemia virus (BLV), of 2 calves vaccinated with BLV, and of 22 patients with human T cell leukemia virus type I (HTLV-I) infection were tested to BLV and HTLV-I by enzyme-linked immunosorbent assay (ELISA) and Western blotting (WB). Sera of 22 healthy cattle and from 22 healthy persons, and mouse monoclonal antibody to BLV-gp51, to HTLV-I-p24, or to HTLV-I-p19 were also tested. Sera of virus-infected hosts gave significantly higher ELISA values than sera of healthy donors to both BLV and HTLV-I. The correlation between ELISA values of bovine sera to BLV and those to HTLV-I was r = 0.76, whereas that of human sera was r = 0.35. By WB and competitive WB assays, bovine sera that were ELISA-positive to BLV reacted with one or more of p12, p15, and p24 of BLV, and with only p24 of HTLV-I. Human sera that were ELISA-positive to HTLV-I reacted with p12 and p24 of BLV, and with one or more of p12, p15, p19, and p24 of HTLV-I. These results demonstrate that BLV and HTLV-I are capable of evoking cross-reactive immune response in at least some hosts under natural infection as well as by virus vaccination.