Oral vaccination with hepatitis E virus capsid protein and immunobiotic bacterium-like particles induce intestinal and systemic immunity in mice

Abstract

Hepatitis E is the major enterically transmitted viral hepatitis after hepatitis A. There are four known genotypes (GT) of the hepatitis E virus (HEV) affecting human beings. HEV GT1 causes outbreaks of acute hepatitis in developing countries of Africa and Asia, whereas HEV GT3 has been recognized as an emergent pathogen in industrialized countries characterized by zoonotic transmission and the possible development of chronic hepatitis in immunocompromised individuals. The aim of this work was to evaluate if the major antigen of HEV, the ORF2 capsid protein, can be used in combination with immunobiotic bacterium like particles (IBLP) for oral vaccination in a mouse model. We have cloned and expressed the RGS-His5-tagged HEV GT 3 capsid protein (ORF2) in E. coli and purified it by NiNTA under native and denaturing conditions. IBLP were prepared from two immunobiotic Lactobacillus rhamnosus strains by heat and acid treatments. Two different doses of protein were combined with IBLP and orally administered to Balb/c mice. After three oral immunizations separated for 14-day intervals, blood, intestinal fluid, Peyer´s patches and spleen samples were drawn. IgA and IgG specific antibodies were determined by ELISA. Mononuclear cell populations were analyzed by flow cytometry, and the cytokine profiles of isolated cells stimulated with ORF2 were determined by ELISA on the supernatants.Orally administered recombinant ORF2 protein combined with IBLP from two L. rhamnosus strains (CRL1505 and IBL027) induced both antigen specific humoral and cellular immune responses in mice. Interestingly, the adjuvant particles showed different behaviors, being BLP027 more effective inducing specific secretory IgA in the gut lumen. IFN-ɣ, TNF-ɑ and IL-4 were produced by Peyer?s plaques lymphocytes stimulated with the capsid antigen ex vivo suggesting a mixed Th1/Th2-type adaptive immune response in immunized mice.Oral vaccines are attractive because they are not invasive, do not need to be administered by specialized personal and, most important, elicit both systemic and local immune responses at the port of entry of the pathogens. Here we present a promising experimental oral vaccine for HEV genotype 3, which could be further developed for human and/or veterinary use.