SURFACTANT PROTEIN-A PROMOTES ATTACHMENT OF MYCOBACTERIUM-TUBERCULOSIS TO ALVEOLAR MACROPHAGES DURING INFECTION WITH HUMAN-IMMUNODEFICIENCY-VIRUS

The incidence of tuberculosis is increasing on a global scale, in part due to its strong association with human immunodeficiency virus (HIV) infection. Attachment of Mycobacterium tuberculosis to its host cell, the alveolar macrophage (AM), is an important early step in the patho genesis of infection. Bronchoalveolar lavage of HIV-infected individua ls demonstrated the presence of a factor which significantly enhances the attachment of tubercle bacilli to AMs 3-fold relative to a normal control population. This factor is surfactant protein A (SP-A). SP-A l evels are increased in the lungs of HIV-infected individuals. SP-A lev els and attachment of M. tuberculosis to AMs inversely correlate with peripheral blood CD4 lymphocyte counts. Elevated concentrations of SP- A during the progression of HIV infection may represent an important n onimmune risk factor for acquiring tuberculosis, even before significa nt depletion of CD4 lymphocytes in the peripheral blood occurs.