COVID-19 has become a global pandemic caused by the novel coronavirus SARS-CoV-2. Understanding the origins of SARS-CoV-2 is critical for deterring future zoonosis, discovering new drugs, and developing a vaccine. We show evidence of strong purifying selection around the receptor binding motif (RBM) in the spike and other genes among bat, pangolin, and human coronaviruses, suggesting similar evolutionary constraints in different host species. We also demonstrate that SARS-CoV-2’s entire RBM was introduced through recombination with coronaviruses from pangolins, possibly a critical step in the evolution of SARS-CoV-2’s ability to infect humans. Similar purifying selection in different host species, together with frequent recombination among coronaviruses, suggests a common evolutionary mechanism that could lead to new emerging human coronaviruses.

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Lack of known mechanisms of protection against Staphylococcus aureus in humans represents an important risk factor for skin infections and bacteremia in patients, intern hindering the development of efficacious vaccines. However, development of effective humoral response may be dampened by converging immune-evasion mechanisms of S. aureus. To develop a promising vaccine against S. aureus, it is pre-requisite to clear understanding of cutaneous, innate and adaptive immune response. The S. aureus dampening the humoral response, T cell help, blocking complement factors, and killing immune players by its toxins are the important factors need to understand clearly. We hypothesized that the master mechanism of S. aureus counteracts may hindering the immune action which may result in failure of target-oriented vaccine development. Developing immunological interventions that can effectively block the S. aureus counteracting mechanisms are the key success for a developing vaccine for the future was warranted.