Genes of SARS-CoV-2 and emerging variants

The pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is distinctly different from outbreaks caused by other coronaviruses: SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV). The differences in the rapid transmission and severity of human coronaviruses are due to the genetic composition of the virus. SARS-CoV-2 contains genes encoding non-structural proteins (NSPs), structural proteins, and accessory proteins. The NSPs are mainly involved in replication of the virus within the host and inhibition of the host defence system. Structural proteins are involved in viral entry and attachment to host cells, preservation of the core virion and elicit the majority of the immune response. The functions of the accessory proteins are largely unknown. Most focus has been given to structural proteins, especially the spike protein as the strongest vaccine candidate. However, the recent emergence of spike variants and their ability to rapidly transmit and escape neutralisation by vaccine-induced antibodies has threatened the global community. Meanwhile, recent studies of accessory proteins reveal their importance in viral pathogenesis. Hence, proper understanding of the functions of all unknown viral proteins is crucial to devise alternate antiviral strategies.