Pathogenesis of macrophage tropic HIV-1.
Despite numerous studies on the impact of viral diversity, human immunodeficiency virus type 1 (HIV-1)-specific immune responses and host factors on disease progression, we still do not have a firm understanding of the pathogenesis of HIV-1 infection. Rapid depletion of CD4+ T-lymphocytes has been associated with a switch in viral coreceptor usage from CCR5 to CXCR4 in approximately 40 to 50% of infected individuals. However, the majority of infected individuals who progress to AIDS harbor only CCR5-dependent (R5) viral strains. HIV-1 disease progression is associated with an enhanced tropism of R5 viral strains for cells of the monocyte/macrophage lineage (enhanced M-tropism). However, the underlying molecular mechanisms contributing to enhanced M-tropism by R5 HIV-1 strains, and how HIV-1 variants with enhanced M-tropism cause CD4+ T-cell depletion in vivo are unknown. This review examines the relationship between viral coreceptor usage, M-tropism, and pathogenicity of HIV-1. We highlight evidence supporting the hypothesis that enhanced M-tropism of R5 HIV-1 results from adaptive viral evolution, resulting in HIV-1 variants that have increased ability to utilize relatively low levels of CD4 and CCR5 expressed on macrophages. The evidence also suggests that these late-emerging, R5 viral strains have reduced sensitivity to entry inhibitors, and increased ability to cause CD4+ T-lymphocyte loss. These variants are likely to impact HIV-1 disease progression, particularly in patients who persistently harbor only R5 viral strains.
Gorry
Paul R
PR
Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia. gorry@burnet.edu.au
Churchill
Melissa
M
Crowe
Suzanne M
SM
Cunningham
Anthony L
AL
Gabuzda
Dana
D
D018450:Disease Progression; D015658:HIV Infections / Q000821:virology; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D008264:Macrophages / Q000821:virology*; D015728:Receptors, HIV
D015728:Receptors, HIV