γδ T-lymphocytes and anti-heat shock protein reactivity in bovine leukemia virus infected cattle

Bovine leukemia virus (BLV) induces a chronic infection in cattle that may result in persistent lymphocytosis (PL) and, sometimes, enzootic bovine leukosis. The cellular and humoral immune responses of the host following infection have been extensively investigated but little is known about the involvement of γδ T-cells in BLV pathogenesis. The affluence of these cells in cattle, and particularly in the peripheral blood of young ruminants, may suggest a particular role for them in defense mechanisms. In this study we have examined circulating γδ lymphocytes that express workshop clusters 1 (WC1) and 2 (WC2). In healthy cattle the WC1 cell count tends to decrease with age and adult cattle blood has statistically lower numbers (19.0 ± 6.6%) than that of young animals (40.1 ± 7.2%). However, in the blood of BLV-seropositive adult cattle and mainly in BLV + PL + animals the population of WC1 cells is elevated compared with uninfected animals (P < 0.007). Likewise, the WC2 cell count is increased (P < 0.01) in BLV + PL +. Furthermore, we have investigated whether BLV infection up-regulates the expression of heat shock proteins (HSP) which in turn could augment the humoral response. Anti-HSP70 activity was examined in the sera of 34 BLV-infected cattle and 40 healthy controls by ELISA. Significantly higher activities (P < 0.001) were observed in BLV-infected cattle.