The evolutionary history of ACE2 usage within the coronavirus subgenus Sarbecovirus.

Severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) and SARS-CoV-2 are not phylogenetically closely related; however, both use the angiotensin-converting enzyme 2 (ACE2) receptor in humans for cell entry. This is not a universal sarbecovirus trait; for example, many known sarbecoviruses related to SARS-CoV-1 have two deletions in the receptor binding domain of the spike protein that render them incapable of using human ACE2. Here, we report three sequences of a novel sarbecovirus from Rwanda and Uganda that are phylogenetically intermediate to SARS-CoV-1 and SARS-CoV-2 and demonstrate via in vitro studies that they are also unable to utilize human ACE2. Furthermore, we show that the observed pattern of ACE2 usage among sarbecoviruses is best explained by recombination not of SARS-CoV-2, but of SARS-CoV-1 and its relatives. We show that the lineage that includes SARS-CoV-2 is most likely the ancestral ACE2-using lineage, and that recombination with at least one virus from this group conferred ACE2 usage to the lineage including SARS-CoV-1 at some time in the past. We argue that alternative scenarios such as convergent evolution are much less parsimonious; we show that biogeography and patterns of host tropism support the plausibility of a recombination scenario, and we propose a competitive release hypothesis to explain how this recombination event could have occurred and why it is evolutionarily advantageous. The findings provide important insights into the natural history of ACE2 usage for both SARS-CoV-1 and SARS-CoV-2 and a greater understanding of the evolutionary mechanisms that shape zoonotic potential of coronaviruses. This study also underscores the need for increased surveillance for sarbecoviruses in southwestern China, where most ACE2-using viruses have been found to date, as well as other regions such as Africa, where these viruses have only recently been discovered.

The evolutionary history of ACE2 usage within the coronavirus subgenus Sarbecovirus.

SARS-CoV-1 and SARS-CoV-2 are not phylogenetically closely related; however, both use the ACE2 receptor in humans for cell entry. This is not a universal sarbecovirus trait; for example, many known sarbecoviruses related to SARS-CoV-1 have two deletions in the receptor binding domain of the spike protein that render them incapable of using human ACE2. Here, we report three sequences of a novel sarbecovirus from Rwanda and Uganda which are phylogenetically intermediate to SARS-CoV-1 and SARS-CoV-2 and demonstrate via in vitro studies that they are also unable to utilize human ACE2. Furthermore, we show that the observed pattern of ACE2 usage among sarbecoviruses is best explained by recombination not of SARS-CoV-2, but of SARS-CoV-1 and its relatives. We show that the lineage that includes SARS-CoV-2 is most likely the ancestral ACE2-using lineage, and that recombination with at least one virus from this group conferred ACE2 usage to the lineage including SARS-CoV-1 at some time in the past. We argue that alternative scenarios such as convergent evolution are much less parsimonious; we show that biogeography and patterns of host tropism support the plausibility of a recombination scenario; and we propose a competitive release hypothesis to explain how this recombination event could have occurred and why it is evolutionarily advantageous. The findings provide important insights into the natural history of ACE2 usage for both SARS-CoV-1 and SARS-CoV-2, and a greater understanding of the evolutionary mechanisms that shape zoonotic potential of coronaviruses. This study also underscores the need for increased surveillance for sarbecoviruses in southwestern China, where most ACE2-using viruses have been found to date, as well as other regions such as Africa, where these viruses have only recently been discovered.

Understanding the Apgar score.

Apgar scores are determined for every neonate born in a U.S. hospital. Despite the frequency with which the scores are calculated, they are not always accurate. In addition, some individuals attempt to use the scores to substantiate certain claims, such as birth asphyxia. This article discusses some of the common misunderstandings and limitations of the Apgar score and suggests measures for improvement.

Effect of chlorhexidine mouthrinse on cathepsin C activity in human saliva.

UNLABELLED: Chlorhexidine is an active agent commonly used against dental plaque in the mouth apart from fluorides applied to prevent caries. It is contained in toothpastes and mouthrinses. PURPOSE: The aim of the study was to assess the effect of mouthrinses containing chlorhexidine digluconate on the activity of cathepsin C in human saliva. MATERIAL AND METHODS: Material for analyses contained mixed saliva samples collected at rest, directly into test tubes (Z PS type, Medlab) at least 2 hours after meal from 40 subjects (dentistry students; 30 women and 10 men), aged 19-24. Saliva was collected before the preparations were applied after rinsing the mouth with distilled water and following a single use of the preparations according to the producer's instructions, 8 samples for each preparation. RESULTS: The decrease of cathepsin C was observed for each preparation, but was the greatest after mouth rinsing with Kin Gingival (65.08%) and Corsodyl (58.00%). CONCLUSIONS: The current study confirms this assumption by finding a decrease in cathepsin C activity after the use of chlorhexidine mouth rinses.

Comparative analysis of the effect of preparations used in professional fluoride prophylaxis on the chosen parameters of human saliva.

UNLABELLED: Regular supply of fluoride ions to the oral environment is one of the prophylactic actions against dental caries. Fluorides, whose exogenous action combines with saliva properties, condition the anticariogenic effect. Fluoride ions exhibit high chemical activity, can alter the oral environment parameters and inhibit the activity of enzymes. PURPOSE: In the current study, the effect of fluoride preparations used in professional caries prophylaxis on chosen saliva parameters was studied. The levels of pH and fluoride ions, and the activity of cathepsin D in human saliva were determined. MATERIAL AND METHODS: Material for analysis contained resting mixed saliva collected before and 1, 4 and 24 hours after the application of Duraphat, Elmex Gel, Fluor Protector, Fluormex Gel and Fluoro-Gel. RESULTS: The fluoride-containing preparations inhibited the activity of cathepsin D in the way depending on the time that had passed since the application and altered the pH level of human saliva.

Effect of fluoride preparations on the activity of human salivary cathepsin C.

Preparations containing organic and inorganic fluorine compounds are used for oral hygiene. Fluoride ions contained in these preparations display high bioactivity and can alter the environment of the mouth. The aim of the study was to determine the effect of preparations containing aminofluorides, commonly used in oral hygiene, on the activity of salivary cathepsin C (EC 3.4.14.1). The research material included mixed saliva, collected at rest before and after the application of the following preparations: Elmex gelee, Elmex red fluid, Elmex green fluid, Fluormex rinse. The salivary pH, concentration of fluoride ions and activity of cathepsin C were determined. Fluoride preparations inhibit the activity of cathepsin C and cause changes in human salivary pH. Saliva can serve as a diagnostic material in the examination of the environmental exposure to fluorides.