Avaliação de candidatas à vacina contra listeriose em modelo murino

Abstract

L. monocytogenes is the causative agent of human and animal listeriosis, capable of crossing blood-brain and fetoplacental barriers causing serious damage to health. It is a zoonotic disease that results in severe outbreaks of sporadic occurrence worldwide. Little has been developed to fight this infection in humans and animals (mainly ruminants). Vaccination is the best method of combating diseases caused by microorganisms. Controlling vaccines against intracellular pathogens is challenging as it requires the efficient form of memory T cells. Some research has been dedicated to the development of vaccines against L. monocytogenes that use live-attenuated or inactivated organisms, recombinant proteins or peptides always with the objective of facilitating the presentation of antigensFailures in the design of efficient vaccines against listeriosis are often assigned (i) to the possibility of live-attenuated organism to cause disease in some individuals, (ii) to low protection levels achieved by vaccination with inactivated organism and (iii) to the difficulty at finding potent adjuvant inducers of Th1 immune response to enhance the immunogenicity of recombinant proteins or L. monocytogenes antigens. Thus, our studies were focused on the construction of two safe vaccines against listeriosis in the murine model: a developed from by L. monocytogenes inactivated by Gamma irradiation (KLM-γ) associated with alginate-chitosan microcapsules, as adjuvants; a second vaccine controlled by a chimera protein (LM22QR), built from epitopes of L. monocytogenes predicted for murine T cells. The vaccine containing KLM-γ-alginate-chitosan was able to protect mice from bacterial colonization with less liver damage, stimulate cell proliferation and production of cytokines, interferon gamma (IFN-γ) and interleukin 10 (IL-10), and was able to prevent the mortality of animals vaccinated against the lethal bacterial challenge. The recombinant vaccine LM22QR was designed through in silico prediction. Thus, after analyzing the composition and fusion of peptides recognized by the major histocompatibility complex (MHC I and MHC II) of the mouse T cell, a total of 22 L. monocytogenes peptides were selected for the formation of a single protein called LM22QR. A preliminary study using mice vaccinated with the chimera protein LM22QR was associated with Freund's adjuvant (PrQ + FA). In this experiment, it was possible to observe mice vaccinated with PrQ + FA, reducing the bacterial load on the organs and the loss of mortality when challenged by L. monocytogenes. The same was not observed in the group of animals vaccinated with the chimera protein LM22QR alone. New analyzes needed to be performed in the future in order to confirm the real immunogenicity of the chimera protein LM22QR. Finally, the two vaccines developed in this work encourage the development of safe vaccines against listeriosis.