TRIM5α restriction of HIV-1-N74D viruses in lymphocytes is caused by a loss of cyclophilin A protection

The core of HIV-1 viruses bearing the capsid change N74D (HIV-1-N74D) do not bind the human protein cleavage and polyadenylation specificity factor subunit 6 (CPSF6). In addition, HIV-1-N74D viruses have altered patterns of integration site preference in human cell lines. In primary human CD4+ T cells, HIV-1-N74D viruses exhibit infectivity defects when compared to wild type. The reason for this loss of infectivity in primary cells is unknown. We first investigated whether loss of CPSF6 binding accounts for the loss of infectivity. Depletion of CPSF6 in human CD4+ T cells did not affect the early stages of wild-type HIV-1 replication, suggesting that defective infectivity in the case of HIV-1-N74D is not due to the loss of CPSF6 binding. Based on our previous result that cyclophilin A (Cyp A) protected HIV-1 from human tripartite motif-containing protein 5α (TRIM5αhu) restriction in CD4+ T cells, we tested whether TRIM5αhu was involved in the decreased infectivity observed for HIV-1-N74D. Depletion of TRIM5αhu in CD4+ T cells rescued the infectivity of HIV-1-N74D, suggesting that HIV-1-N74D cores interacted with TRIM5αhu. Accordingly, TRIM5αhu binding to HIV-1-N74D cores was increased compared with that of wild-type cores, and consistently, HIV-1-N74D cores lost their ability to bind Cyp A. In conclusion, we showed that the decreased infectivity of HIV-1-N74D in CD4+ T cells is due to a loss of Cyp A protection from TRIM5αhu restriction activity.