Production of hepatitis E virus-like particles presenting multiple foreign epitopes by co-infection of recombinant baculoviruses.

Ryoichi Shima,Naokazu Takeda,Yoshiharu Matsuura,Toru Okamoto,Chikako Kataoka,Yoshio Mori,Takayuki Abe,Tian Cheng Li,Yutaka Sendai

doi:10.1038/srep21638

Ryoichi Shima, Naokazu Takeda + Show 7 more

Open Access

https://doi.org/10.1038/srep21638

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Abstract

Hepatitis E virus (HEV) causes not only endemics via a fecal-oral route but also sporadic cases via zoonotic transmission or blood transfusion. HEV-like particles (HEV-LP) produced by using a baculovirus expression system are considered a candidate for mucosal vaccines for HEV infection. In this study, we attempted to produce a chimeric HEV-LP presenting various foreign epitopes on its surface. Expression of the recombinant capsid proteins carrying a myc- or FLAG-tag inserted between amino acid residues 488 and 489, which are located in the exterior loop on the protruding domain of the HEV capsid, resulted in the production of recombinant HEV-LP. Although expression of the recombinant capsid protein carrying the HA-tag inserted at the same site failed to produce any particles, co-expression with the myc-tagged capsid protein successfully yielded a chimeric HEV-LP consisting of both recombinant capsid proteins. Immunoprecipitation analyses confirmed that the chimeric particles present these foreign epitopes on the surface. Similar results were obtained for the expression of the recombinant capsid proteins carrying neutralizing epitopes of Japanese encephalitis virus. These results suggest the chimeric HEV-LP system provides a novel vaccine carrier that can accommodate multiple neutralizing epitopes on its surface.

Highlights

System resulted in the formation of self-assembled hepatitis E virus (HEV)-like particles (HEV-LP) and release of a large amount of HEV-like particles (HEV-LP) into the culture supernatants[20,23]
Based on the three-dimensional information of the HEV-LP crystal structure, we selected three insertion sites for the foreign epitopes between amino acid residues 484 and 485, 488 and 489, and 555 and 556, which were located in a large loop within the P domain (Fig. 1B,C)
These sites were likely to have at least two advantages for the insertion of foreign epitopes: first, the inserted epitopes would likely be displayed on the surface of the particle because this region is located in the outermost area of the particle (Fig. 1D); and second, the insertion of foreign epitopes was expected to have a minimal impact on the particle formation because this region is apart from any protein-protein interacting faces for the capsid oligomerization

Summary

Introduction

System resulted in the formation of self-assembled HEV-like particles (HEV-LP) and release of a large amount of HEV-LP into the culture supernatants[20,23]. Oral administration of HEV-LP without adjuvant induced systemic and mucosal immune responses against HEV in mice and protective immunity in monkeys[25] These results indicated that HEV-LP has a high immunogenicity in the absence of adjuvants, suggesting it would be a promising candidate for an effective oral vaccine without the requirement of an adjuvant[25]. We chose the large exterior loop of the P domain of the capsid protein as the insertion site of foreign epitopes, because a previous study on the crystal structure of HEV-LP suggested that this region was permissive for manipulation[19]. Expression of the recombinant HEV capsid proteins carrying a myc-tag or FLAG-tag but not an HA-tag inserted in the exterior loop on the P domain resulted in the production of a large amount of the recombinant HEV-LP that was comparable to the quantity of wild-type HEV-LP. Our novel system for producing chimeric HEV-LP presenting multiple foreign epitopes on the surface might be an ideal platform for a multivalent mucosal vaccine

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Results

Conclusion