TRIM5 and AIDS: It is noteworthy that all known human alleles of TRIM5 have a Q at the homologous position, suggesting that human TRIM5 may not pose a critical barrier to transmission of SIVsm into human populations; in this regard, it would be interesting to assess the ability of human TRIM5 variants to restrict divergent primary isolates of SIVsm found in regions of endemic infection among African nonhuman primates and to look for correlations between TRIM5 and susceptibility to HIV-2 in human AIDS cohorts.