The persistent infection of a canine thymus cell line by equine infectious anaemia virus and preliminary data on the production of viral antigens

Equine infectious anaemia virus (EIAV) was adapted to the Cf2Th cell line, a heterologous malignant line from canine thymus. A persistent infection was monitored for 100 serial passages by demonstrating the presence of virus and viral antigens at each 10th passage by electron-microscopy, immunodiffusion and immunofluorescence. Chromosome analysis of EIAV-infected cells indicated they had a karyotype resembling the control cells of similar passage history. Virus-infected cells, grown in roller cultures for 65 days without subculturing, continuously produced viral antigens into supernatant fluids which were harvested every 3–4 days. Antigen peaks were observed at approximately 12-day intervals. Immunoprecipitin lines of identity were demonstrated between ether-extracted antigens from virus-infected canine cell line and known positive EIAV antigen extracted from infected equine spleen and a commercial source. Replication of a non-oncogenic retrovirus (EIAV) resulted in the continuous release of viral antigens from a persistently infected and infinite cell line.