Bordetella Pertussis Mpla and Riboflavin as Adjuvants for Trivalent Influenza Vaccine

Adjuvanted trivalent influenza vaccines containing 3.75 μg of each antigen strain with alum and riboflavin or Bordetella pertussis MPLA were tested in mice. Immune response was evaluated by haemagglutination inhibition test, ELISA and antibody affinity test. The highest increase in antibody titers was obtained with the formulation containing MPLA. Significant increase in HAI titer was observed when mice received the formulation containing MPLA and alum, with a clear cross reaction between B lineages. Corroborating our previous results with monovalent vaccine, this study confirmed the adjuvant formulations containing MPLA or Riboflavin as promising adjuvants to be evaluated in clinical trials. I.INTRODUCTION Seasonal influenza vaccines are usually composed by antigen, i.e., split virus, in a physiological buffer containing or not conservatives. The use of adjuvanted vaccines with reduced antigen amount in humans have already showed efficacy in a monovalent formulation (Precioso et al, 2011) and could be an important tool for antigensparing, for reducing costs or to increase the immune response to new pandemic strains, taking in account the use of an affordable adjuvant. At the same time, since 2013, WHO has been recommended the use of quadrivalent influenza vaccines containing two strains of type B lineages (Yamagata and Victoria) once both lineages have been co-circulating (WHO). However, this increase in vaccine cost might be a trouble in low income and developing countries either financial and product availability. A formulation that could elicit cross-reacting antibodies to B lineages would be especially useful to solve this situation. In light of these facts and considering previous results for monovalent A/H1N1 vaccine (Quintilio et al, 2016; Precioso et al, 2011), in this paper we describe the effect of MPLA and riboflavin combined to alum as adjuvant as a proof-of-concept for trivalent influenza vaccine. The effect of the formulations on eliciting antibody titers and on cross reactivity between B strains (Yamagata and Victoria) were evaluated in order to elucidate the choice for better candidate vaccine adjuvant. Materials and Methods Animals All animal tests were performed following the guidelines from Instituto Butantan Animal Care and Use Committee (permit CEUA 3096300915). Female BALB/c mice (Mus muscullus) aged 6-8 weeks were provided by Instituto Butantan Animal Facilities. During the experiments they received balanced food and fresh water ad libitum. Guinea pigs (Cavia porcellus) red blood cells suspension at 1 % was provided by Influenza Laboratory. Reagents Riboflavin (Vitamin B2) was purchased from Merck. MPLA