Comparative pathogenesis of infection of pigs with hepatitis E viruses recovered from a pig and a human

Specific-pathogen-free pigs were inoculated with one of two hepatitis E vir uses (KEV) tone recovered from a pig and the other from a human) to study t he relative pathogenesis of the two viruses in swine. Fifty-four pigs were randomly assigned to three groups. Seventeen pigs in group 1 served as unin oculated controls, 18 pigs in group 2 were intravenously inoculated with th e swine HEV recovered from a pig in the United States, and 19 pigs in group 3 were intravenously inoculated with the US-2 strain of human HEV recovere d from a hepatitis patient in the United States. Two to four pigs from each group were necropsied at 3, 7, 14, 20, 27, or 55 days postinoculation (DPI ). Evidence of clinical disease or elevation of liver enzymes or bilirubin was not found in pigs from any of the three groups. Enlarged hepatic and me senteric lymph nodes were observed in both HEV-inoculated groups. Multifoca l lymphoplasmacytic hepatitis was observed in 9 of 17, 15 of 18, and 16 of 19 pigs in groups 1 to 3, respectively. Focal hepatocellular necrosis was o bserved in 5 of 17, 10 of 18, and 13 of 19 pigs in groups 1 to 3, respectiv ely. Hepatitis lesions were very mild in group 1 pigs, mild to moderate in group 2 pigs, and moderate to severe in group 3 pigs. Hepatic inflammation and hepatocellular necrosis peaked in severity at 20 DPI and were still mod erately severe at 55 DPI in the group inoculated with human HEV. Hepatitis lesions were absent or nearly resolved by 55 DPI in the swine-HEV-inoculate d pigs. All HEV-inoculated pigs seroconverted to anti-HEV immunoglobulin G. HEV RNA was detected by reverse transcriptase FCR in feces, fiver tissue, and bile of pigs in both MEV-inoculated groups from 3 to 27 DPI. Based on e valuation of microscopic lesions, the US-2 strain of human HEV induced more severe and persistent hepatic lesions in pigs than did swine HEV. Pig live rs or cells from the livers of HEV-infected pigs may represent a risk for t ransmission of HEV from pigs to human xenograft recipients. Since HEV was s hed in the feces of infected pigs, exposure to feces from infected pigs rep resents a risk for transmission of HEV, and pigs should be considered a res ervoir for HEV.