Interplay between endogenous and exogenous human retroviruses

In humans, retroviruses thrive more as symbionts than as parasites. Apart from the only two modern exogenous human retroviruses (human T-cell lymphotropic and immunodeficiency viruses; HTLV and HIV, respectively), similar to 8% of the human genome is occupied by ancient retroviral DNA [human endogenous retroviruses (HERVs)]. Here, we review the recent discoveries about the interactions between the two groups, the impact of infection by exogenous retroviruses on the expression of HERVs, the effect of HERVs on the pathogenicity of HIV and HTLV and on the severity of the diseases caused by them, and the antiviral protection that HERVs can allegedly provide to the host. Tracing the crosstalk between contemporary retroviruses and their endogenized ancestors will provide better understanding of the retroviral world.

Automated summary

In humans, retroviruses, including human endogenous retroviruses (HERVs) and exogenous retroviruses (HTLV and HIV), play complex roles in symbiosis and disease. This review explores the interactions between these groups, the influence of exogenous retrovirus infection on HERV expression, the impact of HERVs on the pathogenicity of HTLV and HIV, and the potential antiviral protection provided by HERVs.