CCR5- and CXCR4-tropic HIV-1 are equally cytopathic for their T-cell targets in human lymphoid tissue

Nat Med. 1999 Mar;5(3):344-6. doi: 10.1038/6565.


A rapid decline in T-cell counts and the progression to AIDS is often associated with a switch from CCR5-tropic (R5) HIV-1 to CXCR4-tropic (X4) HIV-1 or R5/X4 HIV-1 variants. Experimental infection with R5 HIV-1 causes less T-cell depletion than infection with X4 or R5/X4 variants in T-cell cultures, in ex vivo infected human lymphoid tissue and in SCID/hu mice, despite similar replication levels. Experimental genetic changes in those sequences in gp120 that transform R5 HIV-1 variants into otherwise isogenic X4 viruses make them highly cytopathic. Thus, it is now believed that R5 variants are less cytopathic for T cells than are X4 variants. However, it is not known why CCR5-mediated HIV-1 infection does not lead to a massive CD4+ T-cell depletion, as occurs in CXCR4-mediated HIV-1 infection. Here we demonstrate that R5 HIV-1 isolates are indeed highly cytopathic, but only for CCR5+/CD4+ T cells. Because these cells constitute only a small fraction of CD4+ T cells, their depletion does not substantially change the total CD4+ T-cell count. These results may explain why the clinical stage of HIV disease correlates with viral tropism.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • CD4-Positive T-Lymphocytes / virology*
  • Cytopathogenic Effect, Viral
  • HIV-1 / isolation & purification
  • HIV-1 / metabolism
  • HIV-1 / physiology*
  • Humans
  • Lymphoid Tissue / cytology
  • Mice
  • Mice, SCID
  • Receptors, CCR5 / metabolism*
  • Receptors, CXCR4 / metabolism*


  • Receptors, CCR5
  • Receptors, CXCR4