Recombinant BCG as a vaccine platform against COVID-19: construction of polyvalent vaccines for the most important SARS-CoV-2 variants

• Grant number: 21/12711-5
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: August 01, 2022
• End date: July 31, 2024
• Field of knowledge: Biological Sciences - Immunology - Applied Immunology
• Principal Investigator: Luciana Cezar de Cerqueira Leite
• Grantee: Giana Carla Gaboardi
• Host Institution: Instituto Butantan. São Paulo , SP, Brazil
• Associated research grant: 17/24832-6 - Development of Vaccines Based on Recombinant BCG: Tuberculosis, Pertussis, Pneumococcus and Schistosoma, AP.TEM

Abstract

The COVID-19 pandemic is responsible for causing the greatest crisis of the last century. Mass vaccination is considered the most effective option for stopping the virus. The long-term effects of COVID-19 on the immune response are still being studied and will be crucial in determining which vaccine strategy is best suited to maintain long-term immunity. Furthermore, the emergence of variants that carry mutations in certain sites is a concern regarding the loss of effectiveness of current vaccines. Therefore, new vaccines against SARS-CoV-2 that address these changes may represent promising alternatives for the prevention of COVID-19. The BCG (Bacille Calmette-Guerin) vaccine, used for immunization against tuberculosis, has been explored as a platform for the expression of heterologous proteins, including vaccine antigens. Many characteristics of the BCG vaccine, such as the safety, adjuvant properties and activation of trained immunity, together with the fact that it is widely used, may be favorable in a recombinant BCG vaccine against SARS -CoV-2. To date, there are no reports of a recombinant BCG vaccine against SARS-CoV-2. Our laboratory has produced rBCG-RBD and rBCG:LTB-RBD strains, which express the receptor binding domain (RBD) of SARS-CoV-2 with those or without the LTB adjuvant (subunit B of the labile toxin of E. coli) which is currently being tested in animal models. Thus, the purpose of this project is to continue the characterization of these strains and build a polyvalent rBCG strain against the Gama and Delta variants of SARS-CoV-2. Variant mutations will be inserted into the RBD sequence by Overlap Extension PCR. Subsequently, the mutant RBD genes will be cloned and expressed in BCG and once confirmed their expression, the induction of the immune response will be characterized in mice, with the quantification of neutralizing antibodies and the determination of the profile of immune cells and cytokines produced in response to immunization.