In a letter to the journal, an international team outlines concerns regarding a proposed SARS-CoV-2 phylogenetic network that was suggested by investigators from the UK and Germany in a PNAS paper in April. In particular, the critique notes that the bat virus used to root that proposed phylogenetic tree differs from SARS-CoV-2 at some 1,000 or more sites in the genome, and argues against the notion that the COVID-19 pandemic coronavirus mutated to infect populations outside of Asia. "[W]e must underline that finding different lineages in different countries and regions is expected with any RNA virus experiencing founder effects," they write. "When a viral strain is introduced and spreads in a new population … random mutations can be propagated without them being selected or advantageous, due to founder effects."
University of Minnesota researchers explore SARS-CoV-2 entry into the cell via interactions between the coronavirus spike protein and the human ACE2 receptor. With the help of pseudovirus entry assays, protein interaction experiments, and other approaches, the team compared the ACE2 binding affinity and resulting protease enzyme activity, involving spike protein receptor binding domains from SARS-CoV-2 and from the original SARS coronavirus (SARS-CoV). "To fulfill its function, SARS-CoV-2 binds to its receptor human ACE2 through its receptor-binding domain and is proteolytically activated by human proteases," the authors explain, noting that findings from the current study "identify important cell entry mechanisms of SARS-CoV-2 that potentially contribute to the immune evasion, cell infectivity, and wide spread of the virus."
A team from the University of Pittsburgh, St. Jude Children's Research Hospital, and elsewhere look at the adaptations that help vancomycin-resistant Enterococcus faecium establish bloodstream or gastrointestinal infections using samples collected over a decade from two dozen individuals treated for pediatric hematological malignancies. Based on genome sequences for more than 100 vancomycin-resistant E. faecium isolates from 24 patients receiving chemotherapy or hematopoietic stem cell treatment, the researchers searched for mutations coinciding with gastrointestinal colonization or bloodstream infections. "We identified a mutation conferring bacterial growth in alternative sugars that arose de novo in two different patients and was present in five other patients," they report, noting that these and other findings hint that "targeting carbohydrate availability and bacterial adherence may be worthwhile strategies to limit [vancomycin-resistant E. faecium] proliferation in immunocompromised hosts."