Two Strains of Avian Sarcoma Virus Newly Isolated From Chick Fibrosarcomas Induced by Lymphatic Leukemia Virus Subgroup A in Two Lines of Chickens

Abstract

Two strains of avian sarcoma virus, designated S1 and S2, have been newly isolated from avian lymphatic leukemia virus (LLV) subgroup A [LLV(A)]-induced fibrosarcomas in 2 chickens from 2 White Leghorn flocks of lines 151 and BK. Each stock of S1 and S2 contained 2–3×10³ focus-forming units of virus/ml and 10⁶ tissue culture infective dose of LLV(A)/ml. The focus-forming titer of S1 and S2 estimated in chick embryo fibroblast cultures was almost consistent with that estimated by tumor (fibrosarcoma) formation in the chicks. All of the chicks bearing wingweb tumors (fibrosarcomas at the site of inoculation) had macroscopically neoplastic lesions (fibrosarcomas) in a number of visceral organs, such as the lung, liver, and spleen. Each stock of S1 and S2 was cloned by picking a single focus, and each focus was examined for the production of focus-forming virus and LLV. The results suggest that S1 and S2 are heterogenous stocks of sarcoma viruses that are replication-defective to various degrees. The low titer of focus-forming virus in the stocks of S1 and S2 was considered to be due to the small amounts of avian sarcoma virus that could be complemented by LLV.