Chymotrypsin and trypsin sensitivities of avian reoviruses.

Experiments were undertaken to examine the chymotrypsin sensitivity and trypsin sensitivity of 13 avian reoviruses, and to determine if there was any correlation with pathogenicity of some chicken reoviruses. A wide variation in the degree of sensitivity of avian reoviruses to chymotrypsin and trypsin was observed. Overall, the infectivity of the 13 avian reoviruses for Vero cells was markedly reduced by treatment with 0.01% chymotrypsin (the lowest concentration tested) while 0.5% trypsin significantly reduced the infectivity of 9 of 13 strains. Comparison of four avian reoviruses, three resistant and one sensitive to trypsin, for pathogenicity in day old chicks following oral inoculation showed the strains that were resistant to trypsin to be more pathogenic. Tenosynovitis and virus persistence in intestines, liver, heart and hock joint tissues occurred only in chickens inoculated with the trypsin resistant strains. It is concluded that the degree of sensitivity to chymotrypsin and trypsin among avian reoviruses is heterogenous. Sensitivity to trypsin influenced the development of tenosynovitis based on microscopic lesions and virus persistence in tissues.