Specificity of an Interference Among Group A Arboviruses

Studies on a non-interferon-mediated type of interference among the group A arboviruses, eastern equine encephalitis (EEE) virus, and a temperature- sensitive mutant (Ets-4) of EEE, have been extended to include Newcastle disease virus (NDV), vesicular stomatitis virus (VSV), and rabbit pox (RP) virus. In the presence of actinomycin D, Ets-4 virus interfered with the growth of VSV and NDV. The interference observed between NDV or VSV and Ets-4 was reciprocal. VSV did not deter the growth of NDV, but appeared to stimulate its growth slightly. Interference of the growth of VSV by NDV was not observed. The lack of interference between NDV and VSV was reciprocal. The results summarized above demonstrate that interference among group A arboviruses extends to NDV and VSV. With the Ets-4 virus this interference is reciprocal. The stimulatory effect of EEE virus on RP virus early in the infection cycle suggests that both events may represent an early activity manifested by the viral genomes. The mechanism of interference and extent of the observed stimulation remain to be elucidated.