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 presence of 27 copies of enJSRV in the sheep genome, five of which are intact and found in all retroviruses, suggests a role for enJSRV in placental development and protection against similar retroviruses. In vitro studies have shown that enJSRV inhibits various stages of viral replication.