Human hepatitis E virus (HEV) infections by genotype 3 strains in industrialized countries are hypothesized to be caused by pigs. To examine this hypothesis, the potential health risks of transmission routes should be examined. Possible foodborne transmission was studied by quantifying the presence and infectivity of HEV in commercial porcine livers in The Netherlands. A comparison of four tissue disruption and seven RNA extraction methods revealed that mechanical disruption followed by silica-based RNA extraction gave the highest RNA yields and was therefore employed on commercial porcine livers. Four (6.5%) of 62 porcine livers were HEV RNA positive by reverse transcriptase PCR and Southern blot hybridization. Each positive liver was estimated to contain approximately 65 PCR-detectable units per g. Sequences were obtained for three of four positive livers and classified as HEV genotype 3. Ninety-three percent similarity to Dutch human HEV sequences and 97% similarity to Dutch swine HEV sequences were observed. To determine whether positive livers contained infectious HEV particles, extracts from livers with known HEV RNA sequences were inoculated intravenously in pigs. Two control pigs were included: one was inoculated with a high dose known to result in infection (10(4) PCR-detectable units of HEV RNA), and the other was inoculated with a lower concentration of virus that equaled the concentration of PCR-detectable units in commercial livers ( approximately 20 PCR-detectable units). Infection was observed in the high-dose control, but not in other pigs, suggesting a dose-dependent response in pigs. Hence, the implications of HEV RNA in commercial porcine livers in The Netherlands are unknown. However, HEV RNA is present in commercial porcine livers, and sufficient heating of porcine livers before consumption as precautionary measure is recommended.

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Abstract

Background

Worldwide, hepatitis E virus (HEV) genotype 3 is observed in pigs and transmission to humans is implied. To be able to estimate public health risks from e.g. contact with pigs or consumption of pork products, the transmission routes and dynamics of infection should be identified. Hence, the course of HEV-infection in naturally infected pigs should be studied.

Results

To resemble natural transmission, 24 HEV-susceptible pigs were infected either by one-to-one exposure to intravenously inoculated pigs (C1-pigs; n = 10), by one-to-one exposure to contact-infected pigs (C2-pigs: n = 7; C3-pigs: n = 5) or due to an unknown non-intravenous infection route (one C2-pig and one C3-pig). The course of HEV-infection for contact-infected pigs was characterized by: faecal HEV RNA excretion that started at day 7 (95% confidence interval: 5–10) postexposure and lasted 23 (19–28) days; viremia that started after 13 (8–17) days of faecal HEV RNA excretion and lasted 11 (8–13) days; antibody development that was detected after 13 (10–16) days of faecal HEV RNA excretion. The time until onset of faecal HEV RNA excretion and onset of viremia was significantly shorter for iv-pigs compared to contact-infected pigs, whereas the duration of faecal HEV RNA excretion was significantly longer. At 28 days postinfection HEV RNA was detected less frequently in organs of contact-infected pigs compared to iv-pigs. For contact-infected pigs, HEV RNA was detected in 20 of 39 muscle samples that were proxies for pork at retail and in 4 of 7 urine samples.

Conclusion

The course of infection differed between infection routes, suggesting that contact-infection could be a better model for natural transmission than iv inoculation. Urine and meat were identified as possible HEV-sources for pig-to-pig and pig-to-human HEV transmission.

SUMMARYWe analysed 112 idiopathic inflammatory myopathy (IIM) sera for the presence of anti-Ro, anti-La and anti-histidyl-tRNA synthetase (Jo-1) autoantibodies, and subsequently mapped B cell epitopes on the Ro52 protein recognized by anti-Ro52 þ IIM sera. Sera were characterized by immunoblotting, ELISA and RNA precipitation. Both anti-Ro60 and anti-La activity was found in 4% of IIM sera. Anti-Ro52 antibodies were present in 20% of IIM sera. However, in anti-Jo-1 þ IIM sera (21%), the frequency of the anti-Ro52 antibodies was found to be much higher (58%). No cross-reactivity between anti-Ro52 and anti-Jo-1 antibodies could be detected in these sera. To learn more about the nature of anti-Ro52 antibodies occurring in IIM sera, we analysed the major epitopes of the Ro52 protein targeted by antiRo52 þ IIM sera by immunoprecipitation of in vitro translated Ro52 deletion mutants. The major epitope was mapped in the region bordered by amino acids 126 and 252. This part of the protein includes a long a-helical region which contains two potential coiled-coil domains as well as a leucine zipper motif. Although no difference in Ro52 epitope recognition between anti-Jo-1 þ and anti-Jo-1 ¹ IIM sera could be observed, our results suggest that the autoimmune response against Ro52 and Jo-1 in IIM patients is coupled.

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