BCG Vaccine Triggers SARS-CoV-2 Specific T-cell Response

Several studies have shown that individuals who have recovered from COVID-19 have SARS-CoV-2 specific T-cell memory and T-cell dysfunction. Hence T-cells play a pivotal role in mounting a robust immune response against COVID-19. Cross-reactive T-cells between human coronaviruses and SARS-CoV-2 have been previously identified. This suggests the possibility of T-cell cross-protection in COVID-19. Many epidemiological studies suggest that the Bacillus Calmette-Guérin (BCG) vaccine could offer protection against COVID-19. Currently, there are more than 15 clinical trials in progress to determine if BCG vaccination can help reduce or prevent the severity of COVID-19 disease.

Researchers from the Monash University and Monash Medical Centre, Australia, investigated whether peptide sensitization using BCG can produce cross-reactive T-cells against COVID-19. The researchers identified 8 BCG-derived peptides in silico. They used in vitro co-culture system and showed that human CD8+ and CD4+ T-cells primed with a BCG-derived peptide developed high reactivity to its corresponding SARS-CoV-2 derived peptide. All 20 individuals primed with BCG-derived peptides developed improved T-cell reactivity to 7 of 8 SARS-CoV-2 derived peptides. The IFN-g and TNF response was mixed. It was also observed that CD8+ T-cells primed with BCG-derived peptides showed an enhanced perforin expression. 

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