Induction of Hepatitis E Virus Anti-ORF3 Antibodies from Systemic Administration of a Muscle-Specific Adeno-Associated Virus (AAV) Vector

Abstract

The hepatitis E virus (HEV) is a major global health problem, leading to large outbreaks in the developing world and chronic infections in the developed world. HEV is a non-enveloped virus, which circulates in the blood in a quasi-enveloped form. The quasi-envelope protects HEV particles from neutralising anti-capsid antibodies in the serum; however, most vaccine approaches are designed to induce an immune response against the HEV capsid. In this study, we explored systemic in vivo administration of a novel synthetic and myotropic Adeno-associated virus vector (AAVMYO3) to express the small HEV phosphoprotein ORF3 (found on quasi-enveloped HEV) in the musculature of mice, resulting in the robust and dose-dependent formation of anti-ORF3 antibodies. Neutralisation assays using the serum of ORF3 AAV-transduced mice showed a modest inhibitory effect on the infection of quasi-enveloped HEV in vitro, comparable to previously characterised anti-ORF3 antibodies used as a control. The novel AAVMYO3 capsid used in this study can serve as a versatile platform for the continued development of vector-based vaccines against HEV and other infectious agents, which could complement traditional vaccines akin to the current positive experience with SARS-CoV-2.

Multi-epitope vaccine design for hepatitis E virus based on protein ORF2 and ORF3

“…Considering the reduction in antibody-mediated neutralization of HEV resulting in antibody evasion by the secreted form of ORF2 (Yin et al, 2018) and the partly protective ORF3 presented on the surface of quasi-enveloped HEV (Takahashi et al, 2008), we first induced ORF3 as an epitopic candidate combined with ORF2 as a multi-peptide vaccine. As previous studies have demonstrated, ORF3 can partially neutralize quasi-enveloped HEV (Ma et al, 2009;Syed et al, 2017;Maurer et al, 2022). The designed vaccine will therefore potentially possess efficacy against both nonenveloped and quasi-enveloped HEV.…”

“…This suggests that the immunized antibodies inhibit the proliferation of the virus and provide protection against infection ( Syed et al, 2017 ). HEV ORF3 equipped with the myotropic adeno-associated virus vector (AAVMYO3) induced dose-dependent ORF3 antibodies in mice and the serum immunized by ORF3 inhibited infection by enveloped HEV in vivo by 50% compared with that of the control ( Maurer et al, 2022 ). Humans infected with HEV via blood transfusion have been reported in many countries ( Takahashi et al, 2010 ).…”

Efficient formation and maintenance of humoral and CD4 T-cell immunity targeting the viral capsid in acute-resolving hepatitis E infection

“…It remains unclear, however, whether quasi-enveloped virions are completely shielded from immune attacks. Indeed, in vitro studies have shown that eHEV can be neutralized by ORF3-specific antibodies, although this process is not very efficient [13,23]. In the macaque model, eHEV neutralization has also been described [7].…”

“…ORF3, which is translated from the same subgenomic RNA as ORF2 mediates the interaction with the endosomal sorting complexes required for transport (ESCRT)-machinery and is critical for HEV progeny budding into multivesicular bodies [12]. It is unclear to what extend this protein is also targeted by the humoral and cellular adaptive immune system, although it constitutes the only potential viral target on the surface of quasi-enveloped viral particles [13].…”

Human pluripotent stem cell-derived hepatocyte-like cells for hepatitis D virus studies

“…The HB2.7 subgenomic fragment encoding the L-/M-/S-HBsAg of HBV genotype D was cloned into a single-stranded AAV vector (pSSV9-AAV-CMV-EYFP- BGHpolyA) 71 . Recombinant AAVs of serotype 6 were produced and iodixanol-purified as described previously 72 . HLCs were transduced with AAVs two days prior to HDV infection (to express NTCP or CD63) or one day after HDV infection (to express HBsAg).…”