Certain strains of HIV-1 grow well in T cells but poorly in monocytes/macrophages, while others exhibit an opposite tropism. As a model system. I compared the growth of two well-char-acterized HIV-1 strains, WI3 and BaL, in the human T lymphoid
cell
line H9 and primary macrophages prepared from peripheral blood. HIV-1BaL grew very efficiently in primary macrophages but poorly in H9 cells, while HIV-1W13, a derivative of HIV-1IIIB, showed a completely opposite pattern. Fluorescence-activated
cell
sorter analysis indicated that CD4 was not a limiting factor for viral growth in either host cell. The two HIV-1 strains showed an essentially identical pattern of RNA expression in their host cells, suggesting that viral transcription is
regulated
in a
comparable manner. However, there was a significant difference between the two viral strains in the amount of unintegrated HIV-1 DNA observed during a synchronized infection. For example, unintegrated linear DNA was readily observed after
infection
of
H9 cells by HIV-1W13, while HIV-1BaL infection of the same cells did not generate any detectable DNA. These results indicated that viral tropism was primarily determined during the early stages of the virus life cycle; that is, sometime between
binding
of the virus to the cell surface and reverse transcription of the viral genomie RNA.
|