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 pheno‐typic 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.