SUMMARYAcute RSV infection in infancy may produce some asthma-like symptoms and may be followed by a recurrent wheeze later in childhood. It has been proposed that RSV infection stimulates type-2 cytokine responses, resembling those found in atopy and asthma. Peripheral blood cells were obtained from RSVinfected infants (n 30) and healthy controls (n 10). After in vitro restimulation of the cells, intracellular IL-4 and interferon-gamma (IFN-g) were measured by flow cytometry. The cells from RSV-infected infants produced more IL-4 and less IFN-g than those from healthy controls. IL-4 production was more frequent in CD8 than in CD4 cells, and the bias toward IL-4 production was greatest in infants with mild infections, whereas IFN-g production increased with disease severity. Our conclusions are that RSV infection is associated with IL-4 production in peripheral T cells, and that peripheral blood in infants with severe disease may be depleted of cytokine-producing cells.

SUMMARYThe fusion protein of the respiratory syncytial virus (RSV) binds to the pattern recognition receptors, TLR4 and CD14, and initiates innate immunity response to the virus. The aim of the study was to investigate the expression of TLR4 on peripheral blood lymphocytes and monocytes in peripheral blood of infants in both acute and convalescent phase of RSV bronchiolitis ( n = 26). In addition, TNF-a expression in lipopolysaccharide-stimulated monocytes was also assessed. The results showed TLR4 to be expressed predominantly by monocytes in both sick infants and controls. During the acute phase of infection monocytes up-regulated TLR4 in eight infants, which returned to the levels recorded in controls 4-6 weeks from infection. There was no difference in the percentage of TNF-a secreting monocytes. Of the clinical parameters tested, minimal oxygen saturation was found to correlate negatively with this expression in the group of infants with increased TLR4. Additional studies are under way to correlate this finding with the outcome of the immune response to RSV.

Infection with respiratory syncytial virus (RSV) may induce asthma-like symptoms and RSV-specific IgE in infected infants as a result of Th2-like response to RSV. The effect of RSV infection on the expression of B cell antigens CD21 and CD23, putative participants in Th2 responses, was investigated. Samples from bronchiolitic infants (n = 19) were tested by three-color immunofluorescence flow cytometry during the acute phase of infection and 4-6 weeks later. In 6 of 10 RSV-positive infants, the percentage of CD23+ B cells was higher than in 9 RSV-negative children and in controls. Both CD21+ and CD21- B cells exhibited a higher percentage of CD23. The group with increased expression of CD23 antigen had RSV-specific IgE and IgG4 antibodies. These findings corroborate the hypothesis that RSV could provoke a Th2-type response, but the relationship between CD23 antigen and RSV infection must be determined.