H2AC20is a core component of nucleosomes and plays a crucial rolein transcriptional regulation, DNA repair, replication, and chromosomalstability.105 Salivary histone H2A interfereswith the access of SARS-CoV-2 to ACE2-expressing host cells in vitro by masking ACE2 and inhibiting viral entry.106 Interestingly, when compared to healthy andnonsevere COVID-19, serum abundance levels of H2AC20 proteins wereupregulated in severe disease (Bi_1, Shen_1).104,107. This evidence concerns the gene ACE2 and COVID-19.