Smaller Sized Hepatitis E Virus ORF2 Protein-Chitosan Nanoemulsion Conjugate Elicits Improved Immune Response

Abstract

Comparative evaluation of immunomodulating efficiency of chitosan nanoemulsion and gold nanoparticles as an adjuvant for truncated HEV ORF2 structural proteins (26 kDa or 54 kDa) were analyzed. Hepatitis E virus (HEV) ORF2 structural protein has been reported to be immunogenic in nature. In the present study, we have used truncated forms of structural protein-containing C-terminus neutralization epitope as a vaccine candidate. A high-energy emulsification process synthesized chitosan nanoemulsions. HEV antigens were encapsulated in chitosan nanoemulsion (CNE26, CNE54). Swiss albino mice were immunized with these nanoconjugates, and their potency to stimulate humoral immune response as well as cell-mediated immune response was evaluated. The humoral response in mice immunized with CNE26 nanoconjugates was found to be 2.7 times that of IFA26 immunized group, while larger protein nanoconjugate (CNE54) and gold nanoconjugates displayed immune response comparable to that of IFA26 and IFA54. Furthermore, a slower rate of antibody formation was observed in the case of GNP26 immunized mice as compared to GNP54 ones, emphasizing the effect of the size of nanomaterials/nanoconjugates on the immune response. At the same time, the effect of surface functionalization and inherent immune modulation property of chitosan nanoemulsion was observed for CNE nanoconjugates. Both gold and chitosan nanoconjugates elicited cell-mediated immune response as well in mice. This study suggests that smaller-sized protein antigen-chitosan nanoemulsion conjugate has higher immunological potential and can be a better future vaccine candidate than gold nanoparticles.