AN EXPERIMENTAL VACCINE FOR HEPATITIS E ADJUVANTATED WITH SAPONINS DERIVED FROM LEAVES FROM THE SOAP TREE QUILLAJA BRASILIENSIS

MÜLLER, MELISA FLORENCIA; WALLACE, FEDERICO; SACUR, JACINTO ALFREDO; VERA, MARÍA DANIELA; MATIAS-BRANCHER, JULIA RAFAELA; VILLENA, JULIO; KITAZAWA, HARUKI; FERREIRA, FERNANDO; OLIVARO, CRISTINA; VIZOSO PINTO, MARÍA GUADALUPE

Londres

Simposio; 2nd International Hepatitis E Symposium; 2023

●Background and aims Hepatitis E is increasingly reported in industrialized countries mainly associated to zoonotic transmission via consumption of meat products derived from contaminated animals. Hepatitis E virus genotype 3 (HEV-3) is the main genotype associated with this transmission. Although swine, the main reservoir, do not suffer from the disease, a veterinary vaccine could help controlling the disease before it reaches human beings. QuilA® is a potent adjuvant used in veterinary vaccines and consists of a mixture of saponins obtained from the barks of the Chilean tree Quillaja Saponaria. The high demand for the pharmaceutical and cosmetic industries and the tree destructive source have posed the trees at risk. We have recently obtained saponins extracts from the leaves and bark of Quillaja brasilensis (an endemic tree from Argentina, Uruguay, Brazil, and Paraguay) and isolated a novel molecule, Qb1, with adjuvant potential. The aim of this study was to evaluate an experimental vaccine consisting of the recombinant protein HEV-3 ORF2 mixed with the extracts and purified saponins of Quillaja brasiliensis. ●MethodsFraction B from leaves or cortex were obtained by fractionation of an aqueous extract on a C18 SPE column. Fraction B3 was further purified by semi-preparative-HPLC on a reverse phase column, affording a novel triterpenic saponin named Qb1. We evaluated if saponin mixtures could activate macrophages in vitro. We determined the production of cytokines involved in the generation of adaptative immunity and regulators of innate immunity pathways (TNF-α, IL-17, IL-6, IL-1α, IL-1β, INF-γ, IL-4, IL-10, TGF-β, IL-27, A20, Bcl-3, SIGIRR, IRAK-M, MKP-1 and Tollip) by qPCR in porcine macrophages (3D4/31) stimulated with 1,6 ug/ml saponin solutions. Then, we administered the recombinant capsid protein ORF2 (20 ug per dose) produced in E. coli mixed with saponins (20 to 50 ug) to BALB/c mice: 1)Fraction B cortex + ORF2; 2)Fraction B leaves + ORF2; 3)Qb1 + ORF2; 4)ORF2 (control withoutadjuvant) and 5)QuilA®QuilA + ORF2. Mice received 2 doses every 4 weeks subcutaneously; blood samples were taken every 2 weeks to follow up specific antibodies by ELISA. ●ResultsAll saponins significantly (p