Nonhuman TRIM5 Variants Enhance Recognition of HIV-1-Infected Cells by CD8+ T Cells

Area of Science:

• Immunology
• Virology
• Cellular Biology

Background:

• Tripartite motif-containing protein 5 (TRIM5) is known to restrict human immunodeficiency virus type 1 (HIV-1) infection in a species-specific manner.
• TRIM5 interacts with viral capsids and cellular proteasomes, suggesting a potential role in cellular immunity that has not been previously studied.

Purpose of the Study:

• To investigate if nonhuman TRIM5 orthologs, rhesus TRIM5α (RhT5) and TRIM-cyclophilin A (TCyp), can enhance immune recognition of HIV-1-infected cells by CD8(+) T cells.
• To elucidate the mechanism by which TRIM5 influences CD8(+) T-cell-mediated inhibition of HIV-1.

Main Methods:

• Expression of RhT5 and TCyp in HIV-1-infected cells.
• Assessment of CD8(+) T-cell responses, including CD107a/MIP-1β expression.
• Inhibition of TRIM5 activity using a nonimmunosuppressive analog of cyclosporine (SmBz-CsA).

Main Results:

• Expression of RhT5 and TCyp significantly improved CD8(+) T-cell-mediated inhibition of HIV-1.
• TRIM5 restriction directly correlated with the activation of HIV-1-specific CD8(+) T-cell responses.
• Blocking TRIM5 activity with SmBz-CsA reduced CD107a/MIP-1β expression in CD8(+) T cells, confirming the link between TRIM5 and T-cell activation.
• RhT5 induced stronger CD8(+) T-cell responses, potentially through TRIM5-dependent recruitment of viral capsids to proteasomes for enhanced antigen presentation.

Conclusions:

• Nonhuman TRIM5 variants, particularly RhT5, enhance cellular immunity against HIV-1 by boosting CD8(+) T-cell responses.
• TRIM5 couples innate viral sensing with cellular immune activation, a novel mechanism that could be therapeutically exploited for HIV-1 control.
• TRIM5-mediated enhancement of HLA class I antigen presentation may underlie improved T-cell recognition of infected cells.