Antigenic heterogeneity of sialodacryoadenitis virus isolates.

Seventeen field isolates of sialodacryoadenitis (SDA) virus had been isolated from the lung of rats with clinical SDA during epizootics of SDA from 1976 to 1978 in the research laboratory. Based on their neutralization patterns against antisera to strains 681, 930-10, Lu-3, Lu-4 and Lu-7, these isolates were divided into 3 antigenic groups. The first group consisted of 8 isolates which were neutralized by 4 out of 5 antisera at high serum dilution. The second group consisted of 6 isolates which were neutralized by only 2 antisera at high serum dilution. The third group exhibited intermediate neutralization pattern and 3 isolates belonged to it. Considering the time course of virus isolation, it was concluded that three antigenically different SDA viruses had been spread irregularly and ocassionally two had been spread simultaneously in an animal house of rats during the several epizootics of SDA.