Stabilized Human TRIM5α Protects Human T Cells From HIV-1 Infection

Rhesus (rh) but not human (hu) TRIM5 alpha potently restricts human immunodeficiency virus (HIV)-1 infection. It is not clear why huTRIM5 alpha fails to effectively block HIV infection, but it is thought to have a lower affinity for the viral core. Using primary human CD4 T cells, we investigated the ability of huTRIM5 alpha, rhTRIM5 alpha, and the huTRIM5 alpha(R323-332) B30.2/SPRY patch-mutant to form cytoplasmic bodies, postulated as key components of the HIV-1 restriction apparatus. Both rhTRIM5 alpha and huTRIM5 alpha(R323-332) formed pronounced cytoplasmic bodies, whereas cytoplasmic bodies in T cells overexpressing huTRIM5 alpha were present but more difficult to detect. As expression of all three TRIM5 alpha orthologs was similar at the RNA level, we next investigated the role of protein stability in conferring TRIM5 alpha-mediated HIV-1 restriction. Both steady-state and pulse-chase experiments revealed that the huTRIM5 alpha protein was much less stable than rhTRIM5 alpha, and this difference correlated with higher self-ubiquitination activity. Using a stabilized form of huTRIM5 alpha in which the steady-state expression level was more similar to rhTRIM5 alpha, we observed comparable HIV-1 restriction activity in multi-round HIV-1 challenge assays. Lastly, primary human CD4 T cells expressing a stabilized huTRIM5 alpha were protected from HIV-1-mediated destruction in vivo, indicating that efforts to stabilize huTRIM5 alpha should have significant long-term therapeutic value.