Cryptococcus neoformans Coinfection Dampens the TNF-α Response in HIV-1-Infected Human THP-1 Macrophages

Cryptococcus neoformans is a devastating opportunistic fungal pathogen. It mostly impacts people in an immunocompromised state, such as people living with HIV/AIDS and following organ transplantation. Macrophages, in addition to being a major cellular reservoir of HIV-1, represent a unique niche in which both C. neoformans and HIV-1 can coinhabit in the course of natural infection. Here, we report the observation that HIV-1 infection of THP-1 macrophages increases the rate at which they phagocytose C. neoformans cells. We investigated the tumor necrosis factor alpha (TNF-α) signaling and nuclear factor kappa B (NF-κB) activation in human monocyte-derived macrophages infected with HIV-1 alone, as well as those coinfected with HIV-1 and C. neoformans. Our findings showed that while HIV-1 infection alone upregulates TNF-α production and activates NF-κB signaling, C. neoformans coinfection drastically and rapidly dampens this proinflammatory response. These data suggest an antagonism between two important human pathogens during coinfection of macrophages. IMPORTANCE Fungal infections are one of the leading causes of death for people who live with HIV/AIDS. Even though these pathogens are independently well studied, it is still enigmatic how coinfection with HIV-1 and C. neoformans alters gene expression and cellular processes, especially in clinically relevant cell types. Understanding the interplay between these two pathogens is especially critical because C. neoformans mortality largely depends on the host’s immunocompromised state during viral infection. Studying this coinfection is challenging since HIV-1 only infects human cells, and the modified murine HIV-1 virus does not reproduce the clinical landmarks of HIV-1 infection or AIDS in mice. Our observations shed light on how these two pathogens trigger opposing trends in TNF-α and NF-κB signaling in human monocyte-derived macrophages.