Co-infection with opportunistic pathogens promotes human immunodeficiency virus type 1 infection in macrophages

Human immunode®ciency virus type 1 (HIV-1) infection is dependent on susceptible host cells that express both CD4 and chemokine co-receptors. The co-receptor CCR5 is associated with primary infection by macrophage-tropic virus isolates, whereas CXCR4 is commonly associated with T cell ± and dual-tropic viruses. Once infected, lymphocytes and macrophages may replicate HIV-1 or harbor latent virus, depending on environmental factors and cellular activation. Immune activation is often associated with viremia, which is consistent with en-hanced infection and viral replication in activated cells harboring virus. In this regard, op-portunistic infections activate the immune system with the detrimental sequelae of enhanced viral replication and viremia. Under these conditions, viral expansion extends beyond T cells to tissue macrophages, many of which are co-infected with opportunistic pathogens. The opportunistic infections promote macrophage susceptibility to HIV-1 through cytokine mod-ulation and altered chemokine co-receptors, potential targets for intervention. Human immunode®ciency virus type 1 (HIV-1) infection re-quires access to host cells that are susceptible to and capable of replicating the virus. Cellular susceptibility is dependen