Proliferative and cytotoxic responses to mannoproteins of Candida albicans by peripheral blood lymphocytes of HIV-infected subjects

Abstract

Mucosal candidiasis is one of the first opportunistic diseases in HIV-infected subjects. In order to understand the relationship between this disease and immunodeficiency to chemically defined, immunodominant Candida antigens, a mannoprotein fraction from C. albicans cell wall (GMP) was used to analyse proliferative and non-MHC-restricted cytotoxic responses of peripheral blood mononuclear cells (PBMC) from normal and HIV-infected subjects. In the former, GMP induced extensive blastogenesis, generation of powerful cytotoxicity against a tumour cell line (K562), and production of substantial amounts of interferon-gamma (IFN-γ). Cultured PBMC from HIV-infected subjects manifested an early decreased ability for proliferative as well as differentia live cytotoxic responses to the candidal mannoproteins. This inability became clearly evident in subjects with stage III (CDC) of the disease, was total in CDC stage IV and occurred even in some subjects with a normal number of CD4⁺ cells. Low or absent response to GMP correlated with lack of response to tetanus toxoid. In contrast, both lymphoproliferative and cytotoxic responses to exogeneous IL-2 was highly preserved at all stages of infection. The production of IFN-γ in GMP-stimulated PBMC cultures critically fell to negligible values in most of the subjects in CDC stages II and III. Thus, the lowered or absent cell-mediated immune responses to candidal mannoprotein may be one factor to explain the early, elevated susceptibility of HIV-infected subjects to mucosal candidiasis. This study also shows that our mannoprotein preparation may be used as a probe to detect the overall efficiency of T cell responses in the above subjects.