Attenuated isolates of avian reoviruses associated viral arthritis/tenosynovitis in poultry are presented, including avian reovims strain 94826 C140 deposited at the ATCC under Patent Designation PTA-126077 and progeny or derivatives thereof and avian reovims strain 96139 C140 deposited at the ATCC under Patent Designation PTA-126078 and progeny or derivatives thereof. Compositions and methods for administering the isolates or compositions as vaccines to control of reovims-induced viral arthritis/tenosynovitis in birds of the order Galliformes are also presented.

Compositions and methods are provided that relate to an attenuated reovirus exhibiting oncolytic activity toward cancer cells while displaying reduced lytic activity toward non-malignant cells. Exemplified is an attenuated human reovirus derived from persistently infected fibrosarcoma cells that lacks wild-type reovirus S1 and S4 genes and consequently lacks a detectable reoviral outer capsid .sigma.1 protein and expresses a mutated reoviral outer capsid .sigma.3 protein.

Compositions and methods are provided that relate to an attenuated reovirus exhibiting oncolytic activity toward cancer cells while displaying reduced lytic activity toward non-malignant cells. Exemplified is an attenuated human reovirus derived from persistently infected fibrosarcoma cells that lacks wild-type reovirus S1 and S4 genes and consequently lacks a detectable reoviral outer capsid .sigma.1 protein and expresses a mutated reoviral outer capsid .sigma.3 protein.