DIFFERENTIAL INFECTION OF CD34(-DERIVED DENDRITIC CELLS AND MONOCYTESWITH LYMPHOCYTE-TROPIC AND MONOCYTE-TROPIC HIV-1 STRAINS() CELL)

Monocytes and dendritic cells are infected by HIV-1 and subsequently p roduce virions that initiate further rounds of infection. Current meth ods for the isolation and study of dendritic tells 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 ei ther dendritic cells or monocytes from fetal liver CD34(+) progenitors . CD34(+) cells were first expanded with the growth factors granulocyt e-macrophage CSF and stem cell factor to generate a population of inte rmediate progenitor cells with a relatively immature phenotype. To ind uce specific differentiation to dendritic cells, the cultures were swi tched to serum-free medium with the growth factors granulocyte-macroph age CSF, stem cell factor, TNF-alpha, and IL-4. The cells became highl y positive for HLA class II Ags and the dendritic cell marker CD1a. Cu lture of the intermediate progenitors in serum-containing medium with macrophage CSF resulted in differentiation to adherent monocytes expre ssing high levels of CD14 with low CD1a expression. The intermediate p rogenitors were permissive for HIV infection by both monocyte- and lym phocyte-tropic strains. In contrast, differentiation to monocytes or d endritic cells resulted in restricted viral tropism. Dendritic cells e fficiently replicated the lymphocyte-tropic virus HIV-1(MN), but not t he monocyte-tropic virus HIV-1(ADA). As expected, monocytes only suppo rted replication of HIV-1(ADA). This two-step culture method allows fo r the production of large numbers of monocytes or dendritic cells from a common precursor pool for studying the development of tropism-assoc iated events.