Changes in helper lymphocyte chemokine receptor expression and elevation of IP-10 during acute respiratory syncytial virus infection in infants.

It is known that lymphopenia caused by apoptosis may occur during severe respiratory syncytial virus (RSV) infection. However, further evidence about how T-cell subsets may be affected in infants during severe RSV bronchiolitis is needed to understand the mechanisms through which immunological memory may be altered. There is increasingly convincing evidence that RSV may be associated with the development of atopy and asthma. Surrogates of Th1, Th2 and regulatory T-lymphocyte populations were measured in blood from children with acute RSV bronchiolitis and in convalescence using the cell surface receptors CXCR3, CCR4 and CD25, respectively. Samples were also obtained from healthy age-matched controls. Plasma levels of the chemokines interferon-γ inducible protein-10 (IP-10) and thymus and activation-regulated chemokine (TARC), which are known ligands for CXCR3 and CCR4, were also measured. Free plasma DNA was measured using quantitative PCR. CXCR3-positive cells were significantly decreased during acute infection (p = 0.013), while CCR4 and CD25 T-cell populations were unchanged. Plasma levels of IP-10 were markedly elevated in acute infection (p = 0.001). Convalescent samples were not significantly different to control samples for lymphocyte phenotypes or plasma chemokines. Elevated free plasma DNA was detected during acute infection compared with convalescence and controls. A profound reduction in the Th1, but not Th2, and CD25-positive lymphocyte populations associated with exaggerated IP-10 production occurs in severe RSV bronchiolitis. Free DNA is detectable in plasma. This may allow significant alterations in the generation of T-cell memory.

Peripheral blood lymphopenia and neutrophilia in children with severe respiratory syncytial virus disease.

It is not known why respiratory syncytial virus (RSV) is associated with prolonged sequelae in many children. Measles virus (also a paramyxovirus), acute stress in sepsis, and cardiac bypass all cause lymphopenia. Using a retrospective analysis of records of children in Bristol with RSV infections over 5 years, we found that children with RSV had lower lymphocyte counts than unstressed, stable children prior to cardiac surgery. Children who required intensive care had the lowest lymphocyte counts. Neutrophil counts were raised in RSV-infected children. These data may offer an insight into pathological mechanisms, and suggest new research avenues.