There are 27 known copies of enJSRV in the sheep genome, of which five show intact sequences found in all retroviruses. These seem to have been adopted by the sheep genome as enJSRV aids placental development and provides protection against similar retroviruses. In vitro assays have found that enJSRV does this by blocking various stages of the viral replication cycle.
The sheep genome contains 27 copies of enJSRV, five of which possess intact sequences found in all retroviruses. These genes were likely incorporated into the sheep genome to aid placental development and provide protection against similar retroviruses. In vitro studies have demonstrated that enJSRV inhibits various stages of viral replication.