Indeed, when substituted into FeLV-A prototype isolate, FeLV-A/61E, the unique LTR and SU gene of FeLV-945 were shown to redirect the outcome of infection from T-cell lymphoma of the thymus occurring after prolonged latency to a relatively rapid induction of multicentric lymphoma of B-cell origin, thus recapitulating the natural disease outcome seen with FeLV-945. The gene discussed is ERVW-1; the disease is infection.