HeV sG V

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® 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®, 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® 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® nor the novel p239(gt3) vaccine provided sufficient protection against genotype 3 infection. While Hecolin® 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.

Hepatitis E virus (HEV) is the cause of a liver disease hepatitis E. The translation product of HEV ORF2 has recently been demonstrated as a protein involved in multiple functions besides performing its major role of a viral capsid. As intrinsically disordered regions (IDRs) are linked to various essential roles in the virus’s life cycle, we analyzed the disorder pattern distribution of the retrieved ORF2 protein sequences by employing different online predictors. Our findings might provide some clues on the disorder-based functions of ORF2 protein that possibly help us in understanding its behavior other than as a HEV capsid protein.

The modeled three dimensional (3D) structures of ORF2 showed the predominance of random coils or unstructured regions in addition to major secondary structure components (alpha helix and beta strand). After initial scrutinization, the predictors VLXT and VSL2 predicted ORF2 as a highly disordered protein while the predictors VL3 and DISOPRED3 predicted ORF2 as a moderately disordered protein, thus categorizing HEV-ORF2 into IDP (intrinsically disordered protein) or IDPR (intrinsically disordered protein region) respectively. Thus, our initial predicted disorderness in ORF2 protein 3D structures was in excellent agreement with their predicted disorder distribution patterns (evaluated through different predictors). The abundance of MoRFs (disorder-based protein binding sites) in ORF2 was observed that signified their interaction with binding partners which might further assist in viral infection. As IDPs/IDPRs are targets of regulation, we carried out the phosphorylation analysis to reveal the presence of post-translationally modified sites. Prevalence of several disordered-based phosphorylation sites further signified the involvement of ORF2 in diverse and significant biological processes. Furthermore, ORF2 structure-associated functions revealed its involvement in several crucial functions and biological processes like binding and catalytic activities.

The results predicted ORF2 as a protein with multiple functions besides its role as a capsid protein. Moreover, the occurrence of IDPR/IDP in ORF2 protein suggests that its disordered region might serve as novel drug targets via functioning as potential interacting domains. Our data collectively might provide significant implication in HEV vaccine search as disorderness in viral proteins is related to mechanisms involved in immune evasion.