Title: The role of mannose-binding lectin in pneumococcal infection
Abstract: The role of mannose-binding lectin (MBL) deficiency (<i>MBL2</i>;<i> XA/O</i> and <i>O/O</i> genotypes) in host defences remains controversial. The surfactant proteins (SP)-A1, -A2 and -D, other collectins whose genes are located near <i>MBL2</i>, are part of the first-line lung defence against infection. We analysed the role of MBL on susceptibility to pneumococcal infection and the existence of linkage disequilibrium (LD) among the four genes. We studied 348 patients with pneumococcal community-acquired pneumonia (P-CAP) and 2,110 controls. A meta-analysis of <i>MBL2</i> genotypes in susceptibility to P-CAP and to invasive pneumococcal disease (IPD) was also performed. The extent of LD of <i>MBL2</i> with <i>SFTPA1</i>, <i>SFTPA2</i> and <i>SFTPD</i> was analysed. <i>MBL2</i> genotypes did not associate with either P-CAP or bacteraemic P-CAP in the case–control study. The MBL-deficient <i>O/O</i> genotype was significantly associated with higher risk of IPD in a meta-analysis, whereas the other MBL-deficient genotype (<i>XA/O</i>) showed a trend towards a protective role. We showed the existence of LD between <i>MBL2</i> and SP genes. The data do not support a role of MBL deficiency on susceptibility to P-CAP or to IPD. LD among <i>MBL2</i> and SP genes must be considered in studies on the role of MBL in infectious diseases.