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Volume 8 Supplement 2

Frontiers of Retrovirology 2011

  • Poster presentation
  • Open Access

Cell-to-cell transmission of HIV-1 between CD4+T-cells involves clathrin-mediated endocytosis

  • 1,
  • 1,
  • 2,
  • 1 and
  • 1
Retrovirology20118 (Suppl 2) :P63

  • Published:


  • Reporter Virus
  • Infected Donor
  • Coreceptor Binding
  • Cell Free Infection
  • Endosomal Uptake


HIV-1 infection of CD4+T-cells occurs through cell free infection or through cell-cell contacts. Cell-to-cell transmission is the predominant mode of viral spread in lymphoid tissue and cell culture. Cell free infection of HIV-1 has recently been described to involve clathrin- and dynamin-mediated endosomal uptake of virus. There are also accounts of cell-to-cell transfer of virus involving endosomal uptake, but the precise details of this process remain unclear. Here, we asked what forms of endocytosis might be involved in such cell-to-cell transmission.

Materials and methods

Cells were infected with GFP reporter virus bearing either CXCR4 or CCR5 tropic or the VSV-G envelope. Cell tracker stained target cells were mixed with infected donor cells. Target cells were pretreated with drugs or antibodies to inhibit HIV-1 entry or replication, or were treated to inhibit various forms of endocytosis. Single target cells were then assayed by flow cytometry for the presence of intracellular viral p24 shortly after co-culture, or for expressed GFP at a later time point to allow the distinction between transfer of virus (p24) and transmission of virus (expression of viral GFP).


We found that inhibiting CD4 binding prevented transfer of virus to the target cell and hence transmission of viral genes. In contrast, inhibiting the viral entry cascade downstream of CD4 binding, i.e. coreceptor binding or membrane fusion, had little capacity to prevent transfer of viral p24 to the target cell despite such treatment ultimately preventing the expression of viral genes. The same pattern of results was seen with both R5 and X4 tropic virus. Secondly, inhibition of clathrin-mediated endocytosis and dynamin-mediated endosome scission both prevented transfer and transmission of virus, whilst inhibition of macropinocytosis and caveolae-mediated endocytosis inhibited neither transfer nor transmission of virus.


Collectively, our results show an involvement of clathrin-and dynamin-mediated endocytosis in cell-to-cell transmission of HIV-1 between T-cells and also suggest that events of the viral entry cascade downstream of CD4 binding can occur from within endosomes.

Authors’ Affiliations

McGill University AIDS Centre, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
Institute of Molecular Virology, Ulm University Medical Center, Ulm, 89081, Germany


© Sloan et al; licensee BioMed Central Ltd. 2011

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.