This study thoroughly quantifies the hexa- and heptapeptide sharing of SARS-CoV-2 spike glycoprotein—which is a major antigen of the virus—with mammalian proteomes. A massive peptide commonality is present with humans and mice, i.e., organisms that undergo pathologic consequences following SARS-CoV-2 infection. Instead, no or a lowest number of common peptides are present in mammals that have no major pathologic sequelae once infected by SARS-CoV-2 [10,11,12]. Hence, the data appear to be an indisputable proof in favor of molecular mimicry as a potential mechanism that can contribute to or cause the SARS-CoV-2 associated diseases .
As a second relevant annotation, this study indicates that particular attention has to be dedicated to the choice of the laboratory animals to be used in preclinical studies during the formulation/validation of anti-pathogen vaccines. In the case in object, given the lowest level of sequence similarity of SARS-CoV-2 spike glycoprotein vs. primates proteins, results obtained in studies that use primates as animal models, i.e., rhesus macaque , would be unreliable because of the impossibility of verifying the occurrence of cross-reactivity and related autoimmunity in the absence of shared sequences. In this regards, data illustrated in Fig. 1 explain why, as highlighted by Hogan , “SARS-CoV infection of cynomolgus macaques did not reproduce the severe illness seen in the majority of adult human cases of SARS” . Actually, no clinical signs of disease or marked lung pathology were seen in a study in which both rhesus and cynomolgus macaques were infected with SARS-CoV , and the Authors’ conclusion is that the macaque model is of limited utility in the study of SARS and the evaluation of therapies. Likewise, McAuliffe et al.  described similar findings: “SARS-CoV administered intranasally and intratracheally to rhesus, cynomolgus and African Green monkeys replicated in the respiratory tract but did not induce illness”.
As for domestic animals and cattles, coronaviruses are long known to be enteric pathogens of cats (FeCoV), dogs (CaCoV), cattle (BCoV), and swine (TGEV) . Nonetheless, coronaviruses do not appear to be pathogenic for domestic animals and cattles. Indeed, the scarce or null susceptibility to SARS-CoV-2-induced pathologies is certified by the American Veterinary Medical Association that verbatim declares: “during the first five months of the COVID-19 outbreak (January 1 – June 8, 2020), which includes the first twelve weeks following the March 11 declaration by the WHO of a global pandemic, fewer than 20 pets have tested positive, with confirmation, for SARS-CoV-2 globally. This despite the fact that as of June 8, the number of people confirmed with COVID-19 exceeded 7 million globally and 1.9 million in the United States” (https://www.avma.org/).
In conclusion, in light of the data exposed in Fig. 1 and given the susceptibility parameters such as aging and health status, only aged mice appear to be a correct animal model for testing an anti-SARS-CoV-2 spike glycoprotein vaccine to be used in humans [25, 26].
Finally, this study once more reiterates the concept that only vaccines based on minimal immune determinants unique to pathogens and absent in the human proteome might offer the possibility of safe and efficacious vaccines [16, 27,28,29,30].