Antiviral Effects of Ancient Infections Observed in Human Genome

Traces of ancient infections can be found in the human genome where they may offer protection against modern viruses, according to a study appearing this week in Science. Endogenous retroviruses are abundant components of mammalian genomes and are descended from ancient retroviral germline infections. In several mammals, the envelope proteins encoded by these elements protect against exogenous viruses, though this activity has yet to be confirmed in humans. But a team led by Cornell University researchers has now scanned the human genome and uncovered many envelope-derived sequences with potential antiretroviral activity. They found that one envelope-derived protein called Suppressyn — which is expressed in the developing placenta and is capable of binding to a receptor for a wide number of retroviruses — could restrict infection by extant mammalian type D retroviruses. The team speculates that Suppressyn may have been preserved in the human genome for its ability to shield the early embryo and nascent germline from infection. "The human genome may hold many other retrovirus-derived proteins with protective effects against viral infection," they write.