Effect of Immune Activation Induced byCryptosporidium parvumWhole Antigen on In Vitro Human Immunodeficiency Virus Type 1 Infection

Previous epidemiologic investigations have suggested that persons with AIDS who are infected with Cryptosporidium parvum have a shorter survival time than those with other opportunistic infections. In this study, the effect of immune activation by a crude Cryptosporidium whole antigen on human immunodeficiency virus type 1 (HIV-1) infection was evaluated. Peripheral blood mononuclear cells from healthy persons without HIV-1 infection had increased proliferative and cytokine (interleukin-4, interferon-gamma, and tumor necrosis factor [TNF]-alpha) responses to stimulation with the crude Cryptosporidium whole antigen. This stimulation increased HIV-1 p24 antigen production in in vitro infection by>30-fold. A similar increase in p24 production was also seen when stimulation was done after cells were infected with HIV-1. Neutralization of TNF-alpha reduced Cryptosporidium antigen-induced p24 production by >50%. Results of this study suggest that Cryptosporidium-induced immune activation may be a cofactor in regulating HIV-1 production.