Utilização da linhagem invasiva Lactococcus lactis FnBPA como veículo para a entrega, via mucosas, do plasmídeo vacinal pValac, codificando o antígeno ESAT-6 de Mycobacterium tuberculosis à camundongos BALB/c e avaliação do perfil imunológico gerado por essa nova formulação vacinal

Abstract

ABSTRACT The use of non-pathogenic bacteria, such as lactic acid bacteria (LAB), constitutes an attractive and safer alternative for plasmid DNA vaccine deliver by oral route. Lactococcus lactis, the model BL, is considered GRAS (Generally Recognized As Safe) and, therefore, has been extensively used for the production and delivery of antigens and cytokines at the mucosal level. Now, L. lactis arises as an attractive alternative for the delivery of plasmid DNA vaccines. Thus, it is believed that the use of the invasive L. lactis FnBPA (Fibronectin Binding Protein A) strain, containing the pValac vector, for eukaryotic expression of the ESAT-6 antigen (6-kDa Early Secreted Antigenic Target) of Mycobacterium tuberculosis, could represent a new strategy for controlling Tuberculosis; an infectious disease that affects, in its latent form, 1/3 of the worlds population. Thus, this study aimed to use L. lactis FnBPA (pValac:ESAT-6) to immunize mice and evaluation of immune response generated by this vaccine strategy. Thus, the strain L. lactis FnBPA (pValac:ESAT-6) was used for conducting an oral experiment immunization in BALB/c mice in order to know the profile of the immune response generated. Thus, following immunization, the levels of cytokines and immunoglobulins were measured by Enzyme-Linked Immunosorbent Assay (ELISA), where was high IFN- production by spleen mice immunizated by the strain L. lactis FnBPA(pValac:ESAT-6), statistically different from controls, denoting a Th1 type immune response, needed for immunization against M. tuberculosis infection. Moreover, it was possible to detect the presence of anti-ESAT-6 sIgA in the extract of colon and faeces of the animals, demonstrating a mucosal immune response after immunization with L. lactis FnBPA (pValac: ESAT-6). Thus, this work constitutes the first step towards validation of this new DNA vaccine based on genetically modified LAB.