Contribution of IL-1 to resistance to Streptococcus pneumoniae infection

The role of IL-1 in susceptibility to Streptococcus pneumoniae infection was studied in mice deficient in genes of the IL-1 family [i.e. IL-1α^-/-, IL-1β^-/-, IL-1α/ β^-/- and IL-1R antagonist (IL-1Ra)^-/- mice] following intra-nasal inoculation. Intra-nasal inoculation of S. pneumoniae of IL-1β^-/- and IL-1α/ β^-/- mice displayed significantly lower survival rates and higher nasopharyngeal and lung bacterial load as compared with control, IL-1α^-/- and IL-1Ra^-/- mice. Treatment of IL-1β^-/- mice with rIL-1β significantly improved their survival. A significant increase in blood neutrophils was found in control, IL-1α^-/- and IL-1Ra^-/- but not in IL-1β^-/- and IL-1α/β^-/- mice. Local infiltrates of neutrophils and relatively preserved organ architecture were observed in the lungs of IL-1α^-/- and control mice. However, S. pneumoniae-infected IL-1β^-/-, IL-1α/β^-/- and IL-1Ra^-/- mice demonstrated diffuse pneumonia and tissue damage. Altogether, all three isoforms contribute to protection against S. pneumoniae; our results point to differential role of IL-1α and IL-1β in the pathogenesis and control of S. pneumoniae infection and suggest that IL-1β has a major role in resistance to primary pneumococcal infection while the role of IL-1α is less important.