Mannoproteins of Cryptococcus neoformans induce proliferative response in human peripheral blood mononuclear cells (PBMC) and enhance HIV-1 replication.

To investigate the possible role of Cryptococcus neoformans var. neoformans in HIV disease progression, and to identify the responsible cryptococcal components, an in vitro cell culture model was set up to study the C. neoformans-induced enhancement of HIV replication in HIV-1-infected PBMC. Similar to whole C. neoformans, cell-wall membrane fraction and mannoproteins induced proliferation of PBMC and enhancement of lymphotropic HIV replication in HIV-infected PBMC, while galactoxylomannan did not. MoAbs capable of interfering with MHC class II-mediated antigen presentation prevented the induction of cell proliferation by whole C. neoformans or cryptococcal mannoproteins. MoAb binding to adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) also inhibited C. neoformans-induced cell proliferation. In addition, anti-MHC class II MoAb inhibited the enhancement of HIV replication by C. neoformans. The results suggest that: (i) C. neoformans may accelerate HIV disease progression by stimulation of HIV replication through MHC class II-mediated antigen presentation; and (ii) cryptococcal mannoprotein may be one of the responsible components. The ability to enhance HIV replication in PBMC in vitro is not unique for C. neoformans. However, this is the first report to study in detail a yeast-induced enhancement of HIV replication in PBMC.