Recombinant feline viruses containing the myc gene rapidly produce clonal tumours expressing T-cell antigen receptor gene transcripts.

We, and others, have recently shown that recombinant feline leukaemia viruses (FeLV) containing the myc gene (FeLV-myc) occur in up to 30% of naturally occurring cases of T-cell lymphosarcoma. Investigation of the disease spectrum of two FeLV-myc isolates showed that they induced clonal or oligoclonal T-cell tumours after a short latent period. The phenotypic pattern of the thymic tumours was restricted in that they all expressed the alpha and beta chains of the T-cell antigen receptor and could readily be established in culture in vitro without the addition of exogenous interleukin-2. Although helper FeLV was transmitted from infected cats to uninfected tracer cats, there was no evidence of horizontal transmission of FeLV-myc viruses, suggesting that these viruses arise de novo in individual cases of thymic lymphosarcoma.