Abstract • 92

Viral infections have been associated with cellular immune responses and production of Th1 cytokines. Respiratory syncytial virus(RSV), however, induces virus-specific IgE, which might be a consequence of Th2-like activation. To test this hypothesis, we quantified inteferon- γ (IFN- γ) and interleukin-4(IL-4) in the supernatant of peripheral blood mononuclear cells cultured for 48 hours in the presence of phytomaglutin (PHA),from 20 hospitalized infants during an acute lower respiratory infection caused by RSV and 15 healthy control infants from 1 to 26 month of age. In the 20 patients with RSV-infected and 15 control infants, the levels of serum IL-4.IFN-r.IL-4/IFN-r were 105.86±34.33 (ng/l) vs 61.58± 11.04(ng/l) (p<0.01), 1113.50±265.47 (ng/l) vs 261.24±65.16 (ng/l) (p<0.01), 0.42±0.13 vs 0.06±0.02 (p<0.01). IFN-r production was subtotally suppressed, whereas IL-4 production was obviously increased, giving significantly increased IL-4/IFN-r ratio compared with that in controls. These findings suggest a predominant Th-2-like response in RSV-infected infants, which could explain some aspects of the immunopathogenesis of RSV infection.