Interferon gamma Profile in Egyptian Infants with Respiratory Syncytial Virus bronchiolitis

Viral bronchiolitis is one of the leading causes for hospitalization of infants in the world and causes an estimated one million deaths per year worldwide. Respiratory syncytial virus (RSV) is associated with the majority of cases. During the last few years it has become increasingly clear that T cells contribute to the abnormal regulation of the immune response in viral diseases since these cells are potent producers of a large variety of cytokines. It was reported that cord blood interferon gamma (IFN-γ) responses were inversely related to the frequency of viral respiratory infections. To ascertain whether RSV infection promotes a different IFN-γ profile to that induced by other respiratory infections, thirty-two infants with severe bronchiolitis were enrolled in this study. RSV-IgM was detected by immunofluorescent technique in 23/32 patients. Serum IFN-γ levels in RSV + infants were significantly lower than RSV (p < 0.001). In vitro stimulation of peripheral blood cells followed by flow cytometery combined with intracellular cytokine staining revealed that both CD4+ and CD8+ cells contribute in IFN-γ production. The percentage of CD4+ cells producing IFN-γ in RSV + was significantly lower (P < 0.05) than those in RSV , while the difference in % of CD8+ between RSV + and RSV was non significant. Our conclusions are that RSV infection is associated with severe decreased IFN-γ responses. Both CD4+ and CD8+ cells contribute in IFN-γ production during RSV bronchiolitis. RSV infection promotes a different IFN-γ profile from that induced by other respiratory infections.