Primary cytotoxic T-cell responses to bovine respiratory syncytial virus in calves.

Bovine respiratory syncytial virus (RSV) is a major cause of respiratory disease in young calves. Recent studies in calves, in which different T-cell subsets were depleted, have shown that CD8+ T cells play a central role in recovery from RSV infection. The present study demonstrates that RSV-specific, major histocompatibility complex-restricted cytotoxic T cells appear in the peripheral blood of gnotobiotic calves 7-10 days after infection with bovine RSV and were also detected in the lungs 10 days after infection. The cytotoxic T lymphocytes (CTL) recognized antigenically distinct strains of bovine RSV. There was no correlation between either the level of CTL activity in the lung or the development of CTL in the peripheral blood and the extent of pneumonic consolidation. The demonstration of CD8+ CTL in the lungs at a time when bovine RSV has been cleared confirms the importance of these cells in recovery from infection.