Mucosal control of Streptococcus pneumoniae infections

Abstract

Infections due to Streptococcus pneumoniae are associated with up to a million deaths per year, especially among young children and older adults. Mucosal sites, particularly the nasopharynx and upper and lower respiratory tracts, serve as the initial site of exposure and the subsequent morbidity and morality associated with this invasive bacterial pathogen. Thus, control of the pneumococcus at mucosal sites, where infection begins, is a critical goal in preventing disease. The mechanisms of mucosal control are not well characterized. These host strategies may support both antibody- and complement-dependent bacterial control by phagocytes. Newer data suggest that antibody-independent but CD4+ T cell-dependent processes may play an important role in bacterial clearance at these sites of entry. The bacteria employ a multifaceted range of pathogenic and immune-evasive activities to subvert the host response. Vaccine development should continue to focus on exploiting both the shared and the serotype-specific characteristics and vulnerabilities of the organism to enhance mucosal defense against this common and virulent pathogen.