SARS-CoV-2 and SARS-CoV share a common human receptor ACE2. Protein-protein interaction structure modeling indicates that spike-RBD of the two viruses also has similar overall binding conformation and binding free energy to ACE2. In vitro assays using recombinant ACE2 proteins and ACE2 expressing cells confirmed the two coronaviruses' similar binding affinities to ACE2. The above studies provide experimental supporting evidences and possible explanation for the high transmissibility observed in the SARS-CoV-2 outbreak. Potent ACE2-blocking SARS-CoV neutralizing antibodies showed limited cross-binding and neutralizing activities to SARS-CoV-2. ACE2-non-blocking SARS-CoV RBD antibodies, though with weaker neutralizing activities against SARS-CoV, showed positive cross-neutralizing activities to SARS-CoV-2 with an unknown mechanism. These findings suggest a trade-off between the efficacy and spectrum for therapeutic antibodies to different coronaviruses, and hence highlight the possibilities and challenges in developing broadly protecting antibodies and vaccines against SARS-CoV-2 and its future mutants.
Bacterial interactions in the biological network affect the growth of Bifidobacterium. In the present study, five habitats were constructed by changing animals, their health statuses and their diets. In each of these habitats, different networks of Bifidobacterium were outlined through correlation analysis of the 50 most dominant microbes. Thirty-eight bacterial genera directly correlated with the growth of Bifidobacterium, including 23 genera with a positive correlation and 15 genera with a negative correlation. This study presented, to our knowledge, a new biological network of rodent gut Bifidobacterium under various representative habitats. This study shows an in vivo network of Bifidobacterium, thereby contributing to constructing an in vitro network of Bifidobacterium for further studies.
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