The role of mannose binding lectin (MBL) in co-infection of pandemic H1N1 and Streptococcus pneumoniae (168.14)

Abstract

Pandemic H1N1 (pdmH1N1) influenza A virus caused massive outbreak in 2009 and currently circulates in the community worldwide. Recent studies on this pandemic revealed that most of the deaths were resulted from secondary bacterial pneumonia caused by common bacteria found in upper respiratory tract, such as Streptococcus pneumoniae. Previous studies have shown that mannose binding lectin (MBL) exhibits anti-viral and anti-bacterial effects in vitro and in vivo. However, the immunomodulatory role of MBL during pdmH1N1/ S. pneumoniae co-infection has not been reported before. In this study, we aim to compare the severity of pdmH1N1/S. pneumoniae co-infection with pdmH1N1 infection alone, and to elucidate the functional implication of MBL during co-infection. Our in vitro preliminary data showed that recombinant MBL could successfully bind to immobilized pdmH1N1 in a dose-dependent manner. However, recombinant MBL was found to be incapable of binding immobilized S. pneumoniae. WT and MBL KO mice were infected with a sublethal dose of pdmH1N1 and S. pneumoniae. Co-infection resulted in a more severe disease phenotype and mortality in mice. However, no significant difference in weight loss and survival rate was observed between WT mice and MBL KO mice. Taken together, these data suggest that MBL may play a more vital role in modulating the first pdmH1N1 infection before subsequent bacterial infection and may attenuate the severity of the co-infection.