LFA-1 expression on target cells promotes human immunodeficiency virus type 1 infection and transmission

Abstract

While CD4 and the chemokine receptors are the principal receptors for human immunodeficiency virus (HIV), other cellular proteins, such as LFA-1, are also involved in HIV infection. LFA-1 and its ligands, ICAM-1, ICAM-2, and ICAM-3, can be expressed on the cells infected by HIV, as well as on the HIV virions themselves. To examine the role of LFA-1 expressed on target cells in HIV infection, Jurkat-derived Jbeta2.7 T-cell lines that express either wild-type LFA-1, a constitutively active mutant LFA-1, or no LFA-1 were used. The presence of wild-type LFA-1 enhanced the initial processes of HIV infection, as well as the subsequent replication and transmission from cell to cell. In contrast, the constitutively active LFA-1 mutant failed to promote virus replication and spread, even though this mutant could help HIV enter cells and establish the initial infection. This study clearly demonstrates the contribution of LFA-1 in the different stages of HIV infection. Moreover, not only is LFA-1 expression important for initial HIV-cell interaction, subsequent replication, and transmission, but its activity must also be properly regulated.

Figures

FIG. 1

Virus DNA detected in Jβ2.7/mock, Jβ2.7/LFA-1 wt, and Jβ2.7/LFA-1 Δ cells following 18 h of infection with SF33 or IIIB. These viruses were originally produced in Jβ2.7/LFA-1 wt cells. (A) PCR and Southern blotting were performed using HIV-1 Gag or β-actin primers on undiluted cell lysates from an equivalent of 105 cells. Positive controls (+) for both HIV Gag and β-actin were included in each experiment. (B) In a separate experiment, HIV-1 Gag DNA was amplified from diluted lysates of IIIB-infected Jβ2.7 cells. An HIV-1 Gag control (+) from the 8E5 cell line containing a single copy of proviral HIV per cell was also tested in the experiment.

FIG. 2

Virus DNA detected in Jβ2.7/mock, Jβ2.7/LFA-1 wt, and Jβ2.7/LFA-1 Δ cells following 18 h of infection with HIV-1 bearing no ICAMs. This virus was produced by transfecting ICAM-negative 293T cells with an infectious HIV-1 clone, R7-GFP. PCR and Southern blotting were performed with HIV-1 Gag primers on cell lysates from an equivalent of 105 cells. Positive (8E5 cells) and negative controls for HIV Gag were also included in this experiment.

FIG. 3

Virus replication in Jβ2.7 transfectants expressing wild-type, mutant, or no LFA-1. Jβ2.7 cells were infected with SF33 or IIIB, and p24 production in 2 × 106 cells was measured by enzyme-linked immunosorbent assay over time.

FIG. 4

Number of infected cells in Jβ2.7/mock, Jβ2.7/LFA-1 wt, and Jβ2.7/LFA-1 Δ cultures following infection with SF33 or IIIB. Infected cells were detected by intracellular p24 staining and quantitated by flow cytometry.

FIG. 5

Comparison of virus spread to Jβ2.7 target cells expressing wild-type, mutant, or no LFA-1. Each Jβ2.7 cell line was mixed with SF33-infected Jβ2.7/wt cells at a ratio of 100 to 7. Infected cells were detected by intracellular fluorescence staining with an anti-p24 MAb and measured over time by flow cytometry.