Preliminary identification of potential vaccine targets for the COVID-19 coronavirus (SARS-CoV-2) based on SARS-CoV immunological studies

Syed Faraz Ahmed; Ahmed A. Quadeer; Matthew R. McKay

SARS-CoV-2 has been observed to be close to SARS-CoV-much more so than MERS-CoV-based on full-length genome phylogenetic analysis (Lu et al., 2020; Zhou et al., 2020) . We checked whether this is also true at the level of the individual structural proteins (S, E, M, and N). A straightforward reference-sequence-based comparison indeed confirmed this, showing that the M, N, and E proteins of SARS-CoV-2 and SARS-CoV have over 90% genetic similarity, while that of the S protein was notably reduced (but still high) (Figure 1a ). The similarity between SARS-CoV-2 and MERS-CoV, on the other hand, was substantially lower for all proteins ( Figure 1a ); a feature that was also evident from the corresponding phylogenetic trees (Figure 1b) . We note that while the former analysis (Figure 1a) was based on the reference sequence of each coronavirus, it is indeed a good representative of the virus population, since few amino acid mutations have been observed in the corresponding sequence data ( Figure S1 ). It is also noteworthy that while MERS-CoV is the more recent coronavirus to have infected humans, and is comparatively more recurrent (causing outbreaks in 2012, 2015, and 2018) (https://www.who.int/emergencies/mers-cov/en/), SARS-CoV-2 is closer to SARS-CoV, which has not been observed since 2004.