Sporadic cases of hepatitis E have been reported in developed countries including Japan. The source of HEV in many cases is unknown, although zoonotic transmission has been suggested. In this study, HEV strains detected from wild boars have been characterized by RT-PCR and sequencing and an antibody to HEV has been measured in Japanese wild boars and hunters families. Of the 91-wild boars, 25 strains were seropositive for HEV, and eleven were positive for HEV-RNA. Sequencing analysis showed that HEV detected from wild boars in Aichi belong to genotype IV cluster. These results indicate that HEV is widespread in the wild boar of this area and that wild boar may serve as reservoirs for HEV infection.
We questioned whether there might be certain people who have TRIF that cannot be cut by HCV NS3/4A protease. Although the cleavage motif was invariably SSTPC/SAHLTPSSLE in all the 62 Japanese subjects examined, we found a genetic polymorphism at the polyproline track just upstream of the cleavage motif of TRIF: that is, the repeat number of proline was 8 in majority, but it was 6 or 9 in occasional subjects. Interestingly, the variant type TRIF (with 6 or 9 prolines) was found only in 13% (5/40) of those persistently infected with HCV, whereas it was found in 41% (9/22) of those who were positive for anti-HCV but negative for HCV RNA.