Persistent infection is a rare sequel following infection of pigs with swine vesicular disease virus

Nine isolates from pigs persistently infected with a recent Italian isolate of swine vesicular disease (SVD) virus, ITL/9/93, were collected sequentia lly over 121 days and were characterized antigenically and biochemically. T here was an accumulation of amino acid (aa) substitutions in the capsid pro teins throughout the carrier state that could be correlated with alteration s in antigenicity in virus isolates collected late stage in infection. The aa substitutions detected mainly occurred in VPI and antigenic changes were detected in late isolates both at antigenic site 1, resulting in loss of b inding of Mab 4GO7, and at a closely located site which has not yet been na med, recognized by Mab C29. In further experiments groups of pigs were expo sed to a range of SVD viruses, but no virus was isolated beyond 16 days pos t infection (dpi) nor viral RNA detected beyond 42 dpi. Attempts to transfe r infection to sentinel pigs introduced some time after initial infection o f the original pigs were largely unsuccessful. The carrier state was establ ished in only one out of five experimental infections of pigs with SVD viru s and can therefore be considered a rare sequel to infection with SVD virus and is of limited significance in the epidemiology of the disease.