Resumo

Introduction: The use of non-pathogenic bacteria, such as Lactococcus lactis, constitutes an attractive and safer alternative for plasmid DNA vaccine deliver. In this context, our research group constructed an invasive L. lactis strain (L. lactis FnBPA) as well as a eukaryotic expression plasmid (pValac). It is believed that the use of the L. lactis FnBPA strain, containing the pValac vector for eukaryotic expression of the ESAT-6 antigen of Mycobacterium tuberculosis, could represent a new strategy for controlling Tuberculosis, an infectious disease that affects, in its latent form, 1/3 of the world’s population. Thus, this work aims at constructing a L. lactis FnBPA (pValac:ESAT-6) strain and evaluate the immune response generated by its orally immunization in mice. Methods and Results: For this purpose, the pValac:ESAT-6 was firstly constructed and had its functionality tested by confocal microscopy and flow cytometry. Following, the L. lactis FnBPA (pValac:ESAT-6) strain was also constructed and used for in vivo murine immunization by oral administration, in order to evaluate the profile of the immune response generated. After immunization, the levels of cytokines and immunoglobulins were measured by ELISA. High INF-γ production was observed after immunization with L. lactis FnBPA (pValac:ESAT-6), statistically different from controls, while anti-inflammatory cytokines IL-4 and IL-10 in the stimulated spleen were not detected. Thus, these results show that the use of this strain denotes a Th1 type immune response, required for immunization against M. tuberculosis infection. In order to confirm the cellular immune response obtained, another experiment is in progress. Conclusion: This work constitutes the first step towards validation of the effectiveness of this new DNA vaccine based on genetically modified L. lactis. Financial support: FAPEMIG, Capes and CNPq