PROMOTION OF PHAGOCYTOSIS AND PREVENTION OF PHAGOSOME-LYSOSOME (P-L) FUSION IN HUMAN PERIPHERAL BLOOD MONOCYTES BY SEROTYPE SPECIFIC GLYCOPEPTIDOLIPID (GPL) ANTIGEN OF MYCOBACTERIUM AVIUM COMPLEX (MAC)

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Mycobacterium avium complex (MAC) is one of the most important pathogen coinfected with HIV (AIDS) and a typical intracellular parasite as well as M.tuberculosis. It is also focused that M.avium infection causes immunosuppression especially in the cellular immunity of host animals, and specific serotype-subspecies such as serotype-2, -4 or-8 can be isolated frequently in human infection in AIDS.Furthermore, the prognosis after infection differs by the serotype ; sero-4 shows heavy infection in general, while sero-16 shows rapid improvement. Therefore, we have been interested in the immunomodifying activity of surface glycopeptidolipid (GPL) antigen. However, to date, no information has been available on the virulent factor of MAC related directly with intracellular bacterial killing. Recently, we have tried to test the effect of various GPLs purified from MAC complex on phagocytic processes of human peripferal blood monocytes (PBMC). We have used GPL-coated heat-killed staphylococcal cells to be phagocytosed by PBMC,and P-L fusion was estimated by the acridine orange staining of fused vesicles and bacteria. As the results, serotype-4 GPL showed strong phagocytosis promotion and marked inhibition of P-L fusion, while serotype-16 GPL showed neither promotion of phagocytosis, nor inhibition of P-L fusion in phagocytic cells. Serotype-8 GPL showed stimulation of both phagocytosis and P-L fusion, concomitantly. These effects may be due to unknown interaction between specific carbohydrate chain and organella membranes, and serotype-4 GPL may be one of the possible virulent factors in MAC infection in human phagocytic cells. Comparison with known possible virulent factors such as cord factor, trehalose monomycolate or sulfolipids will be reported.