Human β-Defensin 2 Is Expressed and Associated with Mycobacterium tuberculosisduring Infection of Human Alveolar Epithelial Cells

ABSTRACTTo determine the role of human β-defensin 2 (HBD-2) in human tuberculosis, we studied the in vitro induction of HBD-2 gene expression by Mycobacterium tuberculosisH37Rv infection in the human lung epithelial cell line A549, in alveolar macrophages (AM), and in blood monocytes (MN) by reverse transcription-PCR. We also studied the induction of HBD-2 gene expression by mannose lipoarabinomannan (manLAM) from M. tuberculosis. Intracellular production of HBD-2 peptide was detected by immunocytochemistry and electron microscopy. Our results demonstrated that there was induction of HBD-2 mRNA in A549 cells after infection with M. tuberculosisat various multiplicities of infection (MOI) and that there was stimulation with manLAM. AM expressed the HBD-2 gene only at a high MOI with M. tuberculosis. MN did not express HBD-2 at any of the experimental M. tuberculosisMOI. Immunostaining revealed the presence of intracellular HBD-2 peptide in A549 cells following infection with M. tuberculosis, and the staining was more intense in areas where there were M. tuberculosisclusters. By using electron microscopy we also demonstrated production of HBD-2 after M. tuberculosisinfection and adherence of HBD-2 to the membranes of M. tuberculosis. Alveolar epithelial cells are among the first cells to encounter M. tuberculosisfollowing aerogenic infection. As HBD-2 has been shown to control growth of M. tuberculosisand has chemotactic activity, our results suggest that HBD-2 induction by M. tuberculosismay have a role in the pathogenesis of human tuberculosis.