RESISTANCE TO ALPHA BETA INTERFERONS CORRELATES WITH THE EPIZOOTIC AND VIRULENCE POTENTIAL OF VENEZUELAN EQUINE ENCEPHALITIS VIRUSES AND ISDETERMINED BY THE 5' NONCODING REGION AND GLYCOPROTEINS/

We compared the alpha/beta interferon (IFN-alpha/beta) sensitivities o f the TC-83 vaccine strain and 24 enzootic and epizootic Venezuelan eq uine encephalitis (VEE) isolates: The IFN-resistant or -sensitive phen otype correlated well with epizootic or enzootic potential. IFN-alpha/ beta resistance of Trinidad donkey (TRD) virus correlated with virulen ce determinants in the 5' noncoding region and glycoproteins. Infectio n of mice lacking a functional IFN system with the IFN-sensitive TC-83 virus resulted in disease equivalent to that produced by the virulent , IFN-resistant TRD virus, further demonstrating that IFN resistance c ontributes to VEE virus virulence and is a biological marker of epizoo tic potential.