Expressed in lymphoid tissues; Detected in spleen as well as in B-cell lines, NK cell lines and activated lymphocytes. Variation Gly-112 is associated with low viral loads in untreated HIV patients. The level of circulating virus in the plasma of HIV patients (viral set point) varies among individuals during the nonsymptomatic phase preceding the progression to AIDS. This polymorphism explains 9.6% of the total variation in set point and is associated with the HLA-B*5701 allele, which has the strongest described protective impact on HIV disease progression. However, it is possible that HPC5 polymorphism, and not HLA-B*5701 allele, plays a direct role in the control in viremia in HIV patients. HCP5 is localized within the MHC class I region, but is not structurally related to MHC class I genes. HCP5 is related in sequence to human endogenous retroviruses HERV-L and HERV-16. It has sequence homology with retroviral Pol genes in HERV retroviral element; thus, it is itself a good candidate to interact with HIV-1, possibly through an antisense mechanism against retroviral transcript.