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.

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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.

The paper analyses the epidemic pattern of respiratory syncytial virus (RSV) outbreaks in children in Croatia. Over a period of 11 consecutive winter seasons (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) 3,435 inpatients from Zagreb County aged from infancy to 10 years who were hospitalised with acute respiratory tract infections were tested for RSV-infection. RSV was identified in nasopharyngeal secretions of patients by virus isolation in cell culture and by detection of viral antigen with monoclonal antibodies.In the Zagreb area, RSV outbreaks were proven to vary in a two-year cycle, which was repeated every 23-25 months. This biennial cycle comprised one larger and one smaller season. Climate factors correlated significantly with the number of RSV cases identified only in the large seasons, which suggests that the biennial cycle is likely to continue regardless of meteorological conditions. Knowledge of this biennial pattern should be useful in predicting the onset of RSV outbreaks in Croatia, and would facilitate planning for the prevention and control of RSV infections in the region. FindingsRespiratory syncytial virus (RSV) frequently causes acute respiratory tract infections (ARTI) among children. In investigations of the epidemiology of viral respiratory infections in Croatian children over four seasons in the 1980s, RSV was determined to be the agent of 20-34% of inpatient ARTI [1,2]. Our study of RSV-genotypes circulating in Zagreb and Vienna from 1987-1994 showed that they were similar to the pattern of expression of these genotypes globally [3].In temperate climates, RSV infections occur in winter and in the early spring [1,4]. The role of climate in causing this epidemic pattern has not been evaluated in the area including and surrounding Croatia. We set out to examine the timing of RSV epidemics and the relationship of various meteorological factors and the number of RSV infections in children over 11 consecutive years in Zagreb County. The county covers an area of 3,719.355 km 2 , and includes a population of 1,088,841 inhabitants in the northwest part of Croatia.

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.