Differential infection of CD34+ cell-derived dendritic cells and monocytes with lymphocyte-tropic and monocyte-tropic HIV-1 strains

Monocytes and dendritic cells are infected by HIV-1 and subsequently produce virions that initiate further rounds of infection. Current methods for the isolation and study of dendritic cells are hampered by the low frequency of these cells and contamination with other cell types. A two-step culture method was devised to generate large numbers of either dendritic cells or monocytes from fetal liver CD34+ progenitors. CD34+ cells were first expanded with the growth factors granulocyte-macrophage CSF and stem cell factor to generate a population of intermediate progenitor cells with a relatively immature phenotype. To induce specific differentiation to dendritic cells, the cultures were switched to serum-free medium with the growth factors granulocyte-macrophage CSF, stem cell factor, TNF-alpha, and IL-4. The cells became highly positive for HLA class II Ags and the dendritic cell marker CD1a. Culture of the intermediate progenitors in serum-containing medium with macrophage CSF resulted in differentiation to adherent monocytes expressing high levels of CD14 with low CD1a expression. The intermediate progenitors were permissive for HIV infection by both monocyte- and lymphocyte-tropic strains. In contrast, differentiation to monocytes or dendritic cells resulted in restricted viral tropism. Dendritic cells efficiently replicated the lymphocyte-tropic virus HIV-1MN, but not the monocyte-tropic virus HIV-1ADA. As expected, monocytes only supported replication of HIV-1ADA. This two-step culture method allows for the production of large numbers of monocytes or dendritic cells from a common precursor pool for studying the development of tropism-associated events.