Bioinformatic analysis of B and T cell epitopes from SARS-CoV-2 Spike, Membrane and Nucleocapsid proteins as a strategy to assess possible cross-reactivity between emerging variants, including Omicron, and other human coronaviruses

The COVID-19 pandemic caused by SARS-CoV-2 produced a global health emergency since December 2019, that up to the end of January 2022 had caused the death of more than 5.6 million people worldwide. Despite emergence of new variants of concern, vaccination remains one of the most important tools to control the pandemic. All approved vaccines and most of the vaccine candidates use the spike protein of the virus as a target antigen to induce protective immune responses. Several variants of the virus present key mutations in this protein which render the virus, at different rates, to evade the neutralizing antibody response. Although experimental evidence suggests that cross-reactive responses between coronaviruses are present in the population, it is unknown which potential antigens shared between different coronaviruses could be responsible for these responses. This study provides predictions of new potential B and T cell epitopes within SARS-CoV-2 Spike (S), Membrane (M) and Nucleocapsid (N) proteins together with a review of the reported B epitopes of these proteins. We also analyse amino acid changes present in the epitopes of variants of concern (VOC) and variants being monitored (VBM), and how these might affect the immune response, as these changes may alter the peptides’ immunogenicity index and the antigen presentation by related HLA alleles. Finally, given these observations, we performed an identity analysis between the repertoire of potential epitopes of SARS-CoV-2 and other human coronaviruses to identify which are conserved among them.

The results shown here together with the published experimental evidence, allow us to support the hypothesis that antibody and T cell cross-reactive responses to common coronaviruses epitopes, could contribute to broaden the protective response to SARS-CoV-2 and its variants. This evidence could help not only to understand cross-reactive responses among coronaviruses but also contribute to elucidate their role in immunity to SARS-CoV-2 induced by infection and/or vaccination. Finally, these findings could promote targeted analysis of antigen-specific immune responses and might orient and drive the rational development of new SARS-CoV-2 vaccines including candidates that ideally provide “universal” protection against other coronaviruses relevant to human health.