Avaliação de formulações vacinais no contexto do modelo experimental da doença de Chagas

Abstract

An important neglected tropical condition, the Chagas disease, though endemic to the Americas, has become a global health concern. The challenges in therapeutics highlight the urgency of developing vaccines to control this disease. Preclinical studies have expanded into a range of vaccine platforms and formulations to be tested. The presentation of new formulations using chimeric recombinant antigens of the etiological agent offers a consequent improvement in immunogenicity. In this context, this study focused mainly on the applicability of formulations with chimeric recombinant proteins of the infectious agent of Chagas disease, the protozoan Trypanosoma cruzi, used as antigenic candidates in isolation or in association with immunoadjuvant molecules and the characterization of the humoral immune response in different immunization protocols. For this purpose, the immunoadjuvant capacity of three structural polypeptides of the virus Triatoma virus (VP1+VP2+VP3: VPs) was presented and investigated, as well as vaccine formulations with the antigens with chimeric characteristics (IBMP-8.1, IBMP- 8.2, IBMP-8.3 and IBMP-8.4: IBMPs) in an antigenic mixture (Mix) associated or not with VPs and known adjuvants (Freund's Incomplete Adjuvant - FIA and Aluminum Hydroxide - Alum) through murine humoral immunity at different times during immunization protocols involving two doses (Protocol 1) and three doses (Protocol 2) in animal models. Thus, female Balb/c mice (Mus musculus) were immunized and in Protocol 1 were separated into five groups: Mix, Mix+FIA, Mix+Alum, Mix+VPs and negative control, while in Protocol 2 the groups were: FIA, Alum, Mix, Mix+FIA, Mix+Alum, and negative control. An experimental infection protocol with T. cruzi was also presented. Animals from all protocols had specific murine antibody profiles of the total IgG and its subtypes: IgG1, IgG2a, IgG2b, and IgG3 determined by Enzyme-Linked Immunosorbent Assay (ELISA) from serum samples. The data demonstrate that the VPs were able to induce good levels of total IgG, IgG2a, IgG2b and IgG3 antibodies and no induction of IgG1, thus characterizing the humoral immunostimulatory property of these polypeptides in association with IBMPs antigens in Mix form; they also suggest that Mix directs to a profile of low presence or total absence of IgG1, an interesting possibility for immune responses against intracellular agents. Additionally, they show that aluminum hydroxide presents performance similar at different concentrations and, finally, they offer the development of two immunization protocols in a murine model in the context of Chagas disease, as well as the importance of the booster dose. Moreover, immunized animals recognize the parasite and infected animals recognize the IBMPs proteins. This pioneering work in the panorama of chimeric recombinant antigens of T. cruzi associated with VPs, FIA and the most used adjuvant in vaccines (Alum), presents itself as promising for the development of new immunobiologicals. The findings promoted the optimization of immunization protocols with small amounts of antigens capable of inducing the production of total IgG antibodies and subtypes that persist after booster doses and provided valuable insights to drive the advancement of chimeric vaccines for human infections caused by trypanosomatids, such as Chagas disease.