HLA-restricted CD8+ cytotoxic T lymphocyte, Interferon-γ, and Interleukin-4 responses to respiratory syncytial virus infection in infants and children

CD8(+) cytotoxic T lymphocyte (CTL) activity, interferon (IFN)-gamma, and interleukin (IL)-4 production were evaluated in a blinded manner among respiratory syncytial virus (RSV)-infected newborns and their mothers for 3 epidemic seasons. Most mothers (80%) exhibited RSV-specific CD8(+) CTL activity. Twenty (80%) of the 26 infants exhibited significant RSV-specific CTL activity during or after their first RSV season. CTL frequency increased with RSV infection rate, reaching 75% by the end of the third season. Most infants who shed virus (75%) had a medically attended lower respiratory tract disease (LRD). In the first year, RSV-infected infants (virus culture and antibody increase) were more likely to develop CTL activity (10 of 13) than were uninfected infants (1 of 5; P = .02). Infants with CTL activity in the first year were less likely to have an LRD in the second year. CD8(+) CTL levels correlated positively with IFN-gamma (P < .001) and inversely with IL-4 (P = .03). Contribution of CD8(+) CTL and IFN-<gamma> in the control of RSV disease in infants and children is implicated.