Immunisation of pigs with recombinant HEV vaccines does not protect from infection with HEV genotype 3

Hepatitis E virus (HEV) is a major cause of acute viral hepatitis worldwide. Up to now, no approved treatment nor a globally licensed vaccine is available. Several recombinant HEV vaccines have been developed to protect against HEV infection in humans, including the commercially available Hecolin vaccine, which are mainly based on HEV genotype 1. However, the efficacy of these vaccines against other HEV genotypes, especially genotype 3 is unknown. In this study, we evaluated the protective efficacy of Hecolin (R) and a novel genotype 3-based vaccine p239(gt3) against HEV-3 in a pig infection model. Pigs were divided into three groups: one group was vaccinated with Hecolin (R), the second group was vaccinated with p239(gt3), and the control group received no vaccine. All pigs were subsequently challenged with HEV genotype 3 to assess the effectiveness of the vaccines. Although all immunised animals developed a high titer of neutralizing antibodies, the results showed that both vaccine applications could not provide complete protection against HEV (gt3) infection: Two out of four animals of the Hecolin (R) group displayed even virus shedding, and viral RNA could be detected in bile and/or liver of three out of four animals in both vaccination groups. Only one out of four animals in each group was fully protected. Neither Hecolin (R) nor the novel p239(gt3) vaccine provided sufficient protection against genotype 3 infection. While Hecolin (R) only partial protected pigs from HEV shedding, the novel p239(gt3) vaccine was at least able to prevent infected pigs from virus shedding. The results highlight the need for further development of HEV vaccines that exhibit broad protection against multiple HEV genotypes and the use of appropriate animal infection models.