AN EXPERIMENTAL MUCOSAL VACCINE FOR HEPATITIS E VIRUS

MÜLLER, M. F.; SACUR, J.; VERA, M.D.; MATIAS BRANCHER, J.; ARCE, L.P.; VILLENA, JULIO; VIZOSO PINTO, M.G.

Congreso; LVII Reunion Anual de la Sociedad Argentina de Invesigaciones Biológicas; 2022

SAIB

The Hepatitis E virus (HEV) causes hepatitis; its principal port of entry is the gastrointestinal mucosa. Nowadays, there are novaccines globally available. Our group has been working on a platform to display antigens on the surface of so-called Bacteriumlike-particles (BLP), which are non-live immunomodulatory bacteria with adjuvant and carrier properties. The main target for anHEV vaccine is ORF2, the capsid protein. We cloned ORF2 most immunogenic domain (O2P2) fused to a LysM domain, whichin nature mediates attachment of enzymes to bacterial peptidoglycan, as anchor to expose the antigen on the surface of the BLPs.To evaluate the experimental vaccines, we immunized mice (n=5) as follows: three oral immunizations with a) the chimeric proteinLysM5O2P2, b) the chimeric protein displayed on the surface of BLPs (LysM5O2P2-BLP) or c) BLP. In a second schedule, weadministered the first dose subcutaneously followed by two oral boosting of d) LysM5O2P2 or e) LysM5O2P2-BLP. Theimmunizations were performed every 14 days and blood samples were taken each time. Ten days after the last dose, mice wereeuthanized, and blood and gut fluid were collected to evaluate the humoral response by ELISA. Spleen and Peyer’s patches (PP)were taken to isolate mononuclear cells for an ex vivo stimulation with the capsid antigen, after which, cytokines were measuredby a commercial ELISA on the culture supernatant. Both groups that received oral immunizations produced specific IgG 2 weeksafter the first immunization, but then, the antibodies were no longer detectable. In contrast, the levels of specific anti-HEV IgG inmice receiving one subcutaneous dose followed by oral immunizations increased after each dose. Specific IgA was detectable inevery group, but it was higher in the mice that received oral doses. In every case, the co-administration of the chimeric protein andBLP induced a stronger humoral response. Regarding the cellular response, we measured higher amounts of INF-ɤ, TNF-ɑ, IL-4and IL-17 in the groups that received LysM5O2P2-BLP orally or under the mixed schedule. We conclude that the oral scheduleinduced a known phenomenon called immune tolerance. This was avoided by giving the first immunization subcutaneously.Comparing all groups, the highest humoral response was found in those groups which received LysM5O2P2-BLP under a mixed schedule. The groups that received LysM5O2P2-BLP orally or combining subcutaneous and oral administration reached higherlevels of every cytokine measured in comparison with those that received just LysM5O2P2, proving the adjuvant effect of BLPs.Here with, we present a promising experimental vaccine that stimulates systemic as well as mucosal humoral and cellular responseagainst the main HEV antigen.