Identification of similar epitopes between SARS-CoV-2 and Bacillus Calmette-Guérin: potential for cross-reactive adaptive immunity

Objectives: Bacillus Calmette–Guerin (BCG) vaccination has been implicated in protection against SARS-CoV-2 and as a non-specific immunization method against the virus. We therefore decided to investigate T cell and B cell epitopes within the BCG Pasteur strain proteome for similarity to immunogenic peptides of SARS-CoV-2. Methods: We used a bioinformatic approach and analyzed the BCG-Pasteur proteome to identify similar peptides to established and novel SARS-CoV-2 T cell and B cell epitopes. Results: We found 112 BCG MHC-I restricted T cell epitopes similar to MHC-I restricted T cell SARS-CoV-2 epitopes and 690 BCG B cell epitopes similar to SARS-CoV-2 B cell epitopes. The SARS-CoV-2 T cell epitopes represented 16 SARS-CoV-2 proteins, the SARS-CoV-2 B cell epitopes represented 5 SARS-CoV-2 proteins, including the receptor binding domain of the spike glycoprotein. Conclusion: Altogether our results provide a mechanistic basis for the potential cross-reactive adaptive immunity that may exists between the two microorganisms.