Envolvimento de elementos da resposta imune inata e adquirida na migração celular em camundongos sensibilizados com adjuvantes vacinais isoladamente e/ou associados ao antígeno de Leishmania (Viannia) braziliensis

Abstract

Vaccine adjuvants are substances that increase the immunogenicity of antigens when co-administered, being important for the formation of a strong, durable and faster immune response. In this context, the use of vaccine adjuvants to generate an effective immune response is essential to design/development of vaccines against visceral leishmaniasis. Thus, the objective of this study was to evaluate the immune response induced by different vaccine adjuvants: Saponin (SAP), Incomplete Freund's Adjuvant (IFA) and monophosphoryl lipid A (MPL) after a single dose of these adjuvants inoculated in the skin mice. In addition, we evaluated the specific immune response to vaccine adjuvants alone and their respective compositions: LBSAP (LB+SAP), LBAIF (LB+IFA) and LBMPL (LB+MPL). Animals were inoculated with saline as a control group. The total antigen of L. (V.) braziliensis (LB) was used as vaccine antigen in the formulations with these adjuvants. In relation to the immunological microenvironment induced by vaccine adjuvants exclusively, our main results showed that the three evaluated vaccine adjuvants are able promote recruitment of cells without damaging in local of injection. In addition, induce selective migration of neutrophils, macrophages and lymphocytes were observed. The migration of neutrophils at 12 hours was increased in all groups. However the presence of this population was more evident after sensitization with SAP adjuvant during all kinetics time points. Concerning the cytokines production, it was observed an increased production of IL-2, IL-6 and IL-4, suggesting a mixed response profile in the animals sensitized with saponin. The IFA adjuvant promoted early increased production of IL-4 and IL-10 followed by increase of TNF-, IFN-, IL-6 and IL-17. We have also observed that the MPL adjuvant induced high production of IL-2, TNF-, IFN- IL-6, IL-17 and IL-10. The alteration in the leukocyte flow reflected changes induced by vaccine adjuvants in skin as well as in draining lymph nodes. Regarding the specific immune response induced by the vaccine compositions we observed that the different formulations were powerfully immunogenic, with increased cellular infiltration in the skin that it was not observed when the LB antigen was inoculated alone. In draining lymph nodes, substantial results were observed after in vitro stimulation with L. (L.) infantum antigen. The vaccine formulations LBIFA and LBMPL showed higher ability to increase the capacity of APCs to present antigens for T lymphocytes, since we observed an increase in the frequency of CD11c+CD86+ cells. The vaccine adjuvants SAP and MPL and the vaccine formulations LBSAP, LBIFA and LBMPL were able to activate lymphocytes as demonstrated by increased expression of CD69 and/or CD25. The LBSAP group was an excellent inducer of pro and anti-inflammatory cytokines at 24 h. However, at 48 h, in general, the higher pro-inflammatory cytokines production has been observed in IFA, LBIFA, MPL and LBMPL groups. Thus, our data demonstrate the importance of the se three vaccine adjuvants to stimulate the early events of the innate and acquired immune response at the site of immunization, and the ability of these substances in increasing the immunogenicity of antigens when co-administered. In addition, we emphasize that the vaccine LBSAP and LBMPL vaccine formulations are potential formulations to be tested in other experimental models. Moreover, this study provides relevant information about the elements of the innate and acquired responses induced by vaccine adjuvants. Also, the date obtained in our study could expand the knowledge about the immune response after immunization and contribute to the development of safe, immunogenic and effective vaccines