HUMORAL IMMUNE-RESPONSE WITHIN THE LUNG IN HIV-1 INFECTION

In order to study the humoral immune defences in the respiratory tract during HIV-1 infection, we measured the levels, local productions and anti-HIV and antibacterial activities of IgG and IgA in the bronchoal veolar lavage fluid (BALF) and serum of 61 adult patients with severe HIV infection and of 56 HIV- controls. Albumin was used as the serum t ransudation factor. The increase of immunoglobulin levels in the serum of HIV-infected patients was confirmed. The IgG level was also increa sed in epithelial lining fluid (ELF), whereas the total IgA level was unchanged and secretory IgA (SIgA) level was decreased. The ELF/serum immunoglobulin ratios suggested that the IgG present in ELF resulted m ainly from transudation, in contrast to SIgA, which was synthesized lo cally in controls but greatly diminished in HIV-infected patients. IgG to HIV-1 could be detected in BALF of all the patients, but IgA to HI V-1 only in 30% of patients. BAL IgG reacted more consistently and wit h a broader array of HIV-1 antigens than did IgA. BAL IgA, when presen t in samples, reacted primarily with viral envelope antigens. Because IgA specificities to some HIV-1 antigens were detected more intensivel y by BAL than by serum immunoglobulins, we conclude that the mucosal i mmune response is distinct from that in serum. IgG antibody activity t o Streptococcus pneumoniae was decreased in HIV-infected patients' ser a, and IgA antibody activities to S. pneumoniae and to Pseudomonas aer uginosa were decreased in ELF in HIV-infected patients.