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Infection of human monocyte-derived macrophages by human immunodeficiency virus mediated by cell-to-cell transmission
S St Luce1, E Arts, R Geleziunas
1Lady Davis Institute, Jewish General Hospital, Montreal, Quebec, Canada.
Abstract:
We have infected ten-day-old primary cultures of human monocyte-derived macrophages (MDM) with HIV-1 by cocultivation with chronically infected monocytic cell lines. This work has involved the U-937 monocytoid cell line, chronically infected with the HIV-IIIB strain of HIV-1 (U-937HIV IIIB) as well as a number of cell clones, termed UHC, which were derived from U-937HIV IIIB by limiting dilution. Cell-free virus, derived from each of U-937HIV IIIB cells and the UHC1 clone were noninfectious for MDM, as determined by failure to express viral p24 antigen (Ag). In contrast, viral p24 Ag production was detected in MDM that had been cocultivated with U-937HIV IIB, and with each of three UHC clones that produced infectious virus. Infection, in each case, was confirmed by polymerase chain reaction detection via the amplification of proviral DNA. In contrast, cocultivation with the UHC15.7 clone, which fails to cleave viral gp160 to its gp120 and gp41 products or the UHC8 clone, which lacks functional reverse transcriptase, did not lead to infection of MDM. Pretreatment of MDM for 2 hr with 1 microM AZT completely prevented infection by culture fluids containing HIVada, a macrophage-tropic virus, but did not affect infection mediated by cocultivation. These results suggest that cell-to-cell transmission of HIV-1, among monocyte-derived macrophages, can be mediated by proviral DNA. Moreover, gp120 at the surface of infected cells may play an important role in this process, since cell-to-cell HIV transmission could not be demonstrated with the UHC clone that is defective in cleavage of the viral envelope glycoprotein gp160.
Insights
Cell-to-cell transmission of human immunodeficiency virus type 1 (HIV-1) between macrophages can occur via proviral DNA. This process involves cell surface gp120 and is distinct from cell-free infection pathways.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Human immunodeficiency virus type 1 (HIV-1) infects macrophages, crucial cells in the immune system.
- Understanding HIV-1 transmission mechanisms within macrophages is vital for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate the mechanisms of HIV-1 transmission between primary human monocyte-derived macrophages (MDM).
- To determine the role of cell-free versus cell-to-cell transmission routes.
- To elucidate the contribution of viral proteins and proviral DNA in macrophage infection.
Main Methods:
- Infection of primary human MDM via cocultivation with chronically HIV-1 infected U-937 monocytic cell lines and their clones.
- Detection of viral p24 antigen (Ag) production in infected MDM.
- Confirmation of infection using polymerase chain reaction (PCR) for proviral DNA amplification.
- Assessment of infection using HIV-1 clones with defects in viral protein processing (gp160 cleavage) and reverse transcriptase activity.
- Evaluation of the effect of azidothymidine (AZT) on cell-free and cell-to-cell infection.
Main Results:
- Cocultivation with HIV-1 infected cells, but not cell-free virus, led to productive infection of MDM, confirmed by p24 Ag production and proviral DNA.
- HIV-1 transmission was dependent on viral clones capable of processing gp160 and possessing functional reverse transcriptase.
- Cell-to-cell transmission was not inhibited by AZT, unlike cell-free infection.
- A UHC clone defective in gp160 cleavage to gp120 and gp41 impaired cell-to-cell transmission.
Conclusions:
- Cell-to-cell transmission of HIV-1 among MDM is a significant route of infection, distinct from cell-free virus spread.
- Proviral DNA transfer and cell surface gp120 appear to be critical mediators of this cell-associated transmission.
- These findings highlight the importance of targeting cell-associated HIV-1 reservoirs and transmission pathways.