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Updated: Jul 19, 2026
Pairwise Growth Competition Assay for Determining the Replication Fitness of Human Immunodeficiency Viruses
Published on: May 4, 2015
Inefficient human immunodeficiency virus replication in mobile lymphocytes
Marion Sourisseau1, Nathalie Sol-Foulon, Françoise Porrot
1Groupe Virus et Immunité, URA CNRS 1930, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France.
Insights
Gentle shaking dramatically reduced human immunodeficiency virus (HIV) replication by impairing cell-to-cell spread. This suggests cell-to-cell transfer is the primary mode of HIV propagation in lymphoid organs.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Lymphotropic retroviruses like HIV and HTLV spread via cell-to-cell transfer, forming virological synapses.
- While HIV cell-to-cell transmission is known, its mechanisms are not fully understood.
Purpose of the Study:
- To investigate the role of cell contacts in HIV transmission.
- To develop a method for quantifying cell-to-cell versus free virus transmission.
- To assess the impact of altering cell contact on HIV replication.
Main Methods:
- Cultures of lymphoid cell lines and primary lymphocytes were subjected to continuous gentle shaking.
- An assay was developed using labeled target cells to measure HIV Gag expression via flow cytometry.
- Relative contributions of free and cell-associated virions to HIV propagation were assessed.
Main Results:
- Gentle shaking significantly reduced viral replication in both cell lines and primary lymphocytes.
- Cellular contacts were found to greatly enhance productive viral transfer compared to free virus infection.
- Virus release from donor cells was not affected by shaking, but transfer to recipient cells was impaired.
Conclusions:
- Cell-to-cell transfer is the predominant mode of HIV spread.
- Disrupting cell contacts severely impairs HIV transmission, explaining efficient replication in lymphoid organs.
Abstract:
Cell-to-cell viral transfer facilitates the spread of lymphotropic retroviruses such as human immunodeficiency virus (HIV) and human T-cell leukemia virus (HTLV), likely through the formation of "virological synapses" between donor and target cells. Regarding HIV replication, the importance of cell contacts has been demonstrated, but this phenomenon remains only partly characterized. In order to alter cell-to-cell HIV transmission, we have maintained cultures under continuous gentle shaking and followed viral replication in this experimental system. In lymphoid cell lines, as well as in primary lymphocytes, viral replication was dramatically reduced in shaken cultures. To document this phenomenon, we have developed an assay to assess the relative contributions of free and cell-associated virions in HIV propagation. Acutely infected donor cells were mixed with carboxyfluorescein diacetate succinimidyl ester-labeled lymphocytes as targets, and viral production was followed by measuring HIV Gag expression at different time points by flow cytometry. We report that cellular contacts drastically enhance productive viral transfer compared to what is seen with infection with free virus. Productive cell-to-cell viral transmission required fusogenic viral envelope glycoproteins on donor cells and adequate receptors on targets. Only a few syncytia were observed in this coculture system. Virus release from donor cells was unaffected when cultures were gently shaken, whereas virus transfer to recipient cells was severely impaired. Altogether, these results indicate that cell-to-cell transfer is the predominant mode of HIV spread and help to explain why this virus replicates so efficiently in lymphoid organs.
