Propagation of Fibroma Virus in Tissue Cultures of Cottontail Testes

Abstract

The Shope fibroma virus, represented by the Patuxent strain, which has been maintained continuously in cottontail rabbits, was carried, on 2 separate occasions, through 14 continuous passages in tissue culture of cottontail testes. Cultures were of explants fixed in clots of chicken fibrin. An increase of titer, up to 10-4, was usually demonstrable within individual passages. Attempts to propagate fibroma virus in cultures of domestic rabbit testes, monkey kidney cells, and in human foreskin were unsuccessful. Cottontail testis was grown on coverslips for histological studies. Staining with haematoxylin and eosin revealed the presence of irregularly-shaped, acidophilic, cytoplasmic inclusions, made especially conspicuous by a halo of clear cytoplasm. The inclusions were often associated with large vacuoles, filled with a substance ground glass in appearance and not found in similar preparations of normal tissue or in the absence of inclusions.