Interference and Neutralization Studies with BRYAN Strain Rous Sarcoma Virus Synthesized in the Absence of Helper Virus

SUMMARY The relationship of RSVβ(O) to other avian tumour viruses was studied by virus interference and serological cross neutralization. Viruses of subgroup B interfere with RSVβ(O) on chicken cells but not on quail cells. Viruses of sub-groups A and C enhance the focus forming efficiency of RSVβ(O). Antisera to RSVβ(O) and avian tumour viruses of sub-group A, B and C do not cross-react, but serological cross-reaction was found between RSVβ(O) and sub-group D. The ability of RSV(O) and L-R cells to stimulate anti-viral antibodies has been investigated. No helper virus in RSVβ(O) stocks was demonstrable by interference assays.