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Hepatitis E virus (HEV) is classified within the family Hepeviridae, genus Hepevirus. HEV genotype 3 (Gt3) infections are endemic in pigs in Western Europe and in North and South America and cause zoonotic infections in humans. Several serological assays to detect HEV antibodies in pigs have been developed, at first mainly based on HEV genotype 1 (Gt1) antigens. To develop a sensitive HEV Gt3 ELISA, a recombinant baculovirus expression product of HEV Gt3 open reading frame-2 was produced and coated onto polystyrene ELISA plates. After incubation of porcine sera, bound HEV antibodies were detected with anti-porcine anti-IgG and anti-IgM conjugates. For primary estimation of sensitivity and specificity of the assay, sets of sera were used from pigs experimentally infected with HEV Gt3. For further validation of the assay and to set the cutoff value, a batch of 1100 pig sera was used. All pig sera were tested using the developed HEV Gt3 assay and two other serologic assays based on HEV Gt1 antigens. Since there is no gold standard available for HEV antibody testing, further validation and a definite setting of the cutoff of the developed HEV Gt3 assay were performed using a statistical approach based on Bayes' theorem. The developed and validated HEV antibody assay showed effective detection of HEV-specific antibodies. This assay can contribute to an improved detection of HEV antibodies and enable more reliable estimates of the prevalence of HEV Gt3 in swine in different regions.

In the absence of commercial kits for serological studies specifically for hepatitis E virus (HEV) infection of swine, the capsid protein of a swine genotype 3 HEV was expressed using a recombinant baculovirus. This antigen was used in an enzyme-linked immunosorbent assay (ELISA) for detection of anti-HEV antibodies. Estimation of sensitivity and specificity was carried out in comparison with a commercial serological assay using sera from pigs infected experimentally with HEV genotype 3, negative sera from SPF pigs and swine sera collected at slaughterhouses. Since a "gold standard" is not available, a latent-class Bayesian approach for correlated tests was used to estimate the sensitivity and specificity of both tests. External field and experimental data were used to determine the parameters of Beta prior distributions. The estimated mean sensitivity of the commercial test was 0.47 with a 95% credibility interval of 0.39-0.55, whereas the estimated mean sensitivity of the genotype 3-based assay was 0.92 [0.81-0.99]. The estimated specificities were 0.98 [0.93-0.99] and 0.98 [0.95-0.99] for the genotype 3-based test and commercial test, respectively. In conclusion, genotype 3-antigen derived from swine HEV is a better candidate for assessing hepatitis E serology in swine., (2009 Elsevier B.V. All rights reserved.)

In Europe, zoonotic hepatitis E virus ( HEV) genotype 3 strains mainly circulate in humans, swine and wild boar. The aim of this study was to investigate the potential transmission of a wild boar originating HEV strain (Wb HEV) to swine by intravenous or oral inoculation and to study the consequences of infection of a Wb HEV strain, a Wb HEV strain previously passaged in a pig and a swine HEV strain after oral inoculation. Firstly, an intravenous infection was performed for which five piglets were divided into two groups with three pigs inoculated with a Wb HEV field strain and two pigs inoculated with a HEV-negative swine liver homogenate. All pigs were necropsied 8, 9 and 10 days post-inoculation. Secondly, an oral infection of 56 days was performed on 12 piglets divided into four groups inoculated with a Wb HEV strain, a Wb HEV strain previously passaged in swine, a swine HEV strain or a HEV-negative swine liver homogenate. After intravenous inoculation, HEV RNA was detected in serum, bile, liver, spleen, duodenum, jejunum, colon, lung, gastro-hepatic lymph nodes and faeces in all infected piglets. After oral inoculation, HEV RNA was detected in serum, bile, liver, gastro-hepatic lymph nodes and faeces. Most of HEV-inoculated pigs became seropositive at day 15. This study provides experimental evidence of early viral spread throughout the organism after intravenous infection with a Wb HEV strain and supports the notion that such a zoonotic strain could be transmitted via the natural faecal-oral route of infection between wild boar and pigs but also between pigs. [ABSTRACT FROM AUTHOR]