Characterization of the immune response generated by intramuscular administration of nucleocapsid and surface antigens of Hepatitis B

Multiple immunization studies have been carried out in mice and humans evaluating formulations based on the sur- face antigen of Hepatitis B virus (HBV) in combination with different adjuvants. Such studies explore the use of new vaccine candidates for the prevention or therapy of hepatitis B infection. We have previously reported the preclinical and clinical development of a novel nasal formulation containing the surface and nucleocapsid antigens of the HBV. The present work explores the immune response elicited in mice when this formulation was administered adsorbed in alum by intramuscular route. Mice were immunized with different antigenic proportions and the immune response was evaluated by ELISA in order to study the total IgG and the main IgG subclasses in sera. The lymphoproliferation capacity of spleen cells stimulated with each antigen was assayed. The results indicate that the formulation is very immunogenic when administered by intramuscular route, eliciting potent humoral immune responses. We also de- monstrated that the inclusion of the nucleocapsid antigen in the formulation favored a deviation to a Th1 pattern of response, showed at IgG subclasses and lymphoproliferation results. The evaluation of this candidate using the parenteral route suggests the potential reduction of the number of doses and the quantity of antigen per dose with respect to the conventional HBV vaccine. The possible use of this formulation as prophylactic or therapeutic vaccine candidates was also discussed.