Host barriers to SARS-CoV-2 demonstrated by ferrets in a high-exposure domestic setting

Ferrets (Mustela putorius furo) are mustelids of special relevance to laboratory studies of respiratory viruses and have been shown to be susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and onward transmission. Here, we report the results of a natural experiment where 29 ferrets in one home had prolonged, direct contact and constant environmental exposure to two humans with symptomatic disease, one of whom was confirmed positive for SARS-CoV-2. We observed no evidence of SARS-CoV-2 transmission from humans to ferrets based on viral and antibody assays. To better understand this discrepancy in experimental and natural infection in ferrets, we compared SARS-CoV-2 sequences from natural and experimental mustelid infections and identified two surface glycoprotein Spike (S) mutations associated with mustelids. While we found evidence that angiotensin-converting enzyme II provides a weak host barrier, one mutation only seen in ferrets is located in the novel S1/S2 cleavage site and is computationally predicted to decrease furin cleavage efficiency. These data support the idea that host factors interacting with the novel S1/S2 cleavage site may be a barrier in ferret SARS-CoV-2 susceptibility and that domestic ferrets are at low risk of natural infection from currently circulating SARS-CoV-2. We propose two mechanistically grounded hypotheses for mustelid host adaptation of SARS-CoV-2, with possible effects that require additional investigation.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, is a zoonotic member of Coronaviridae that emerged in 2019 as a major viral pandemic (1). As of February 2021, there have been ∼102 million confirmed COVID-19 cases globally and ∼2.2 million deaths (2). SARS-CoV-2 uses angiotensin I converting enzyme-2 (ACE2) as its primary cellular receptor for host entry and infection (3–5). In silico analyses of ACE2 genes in diverse mammalian species show that residues important to viral binding are moderately conserved between humans and several domestic animals, and a broad range of species have been demonstrated to be permissive to infection in vitro and in vivo (6–10).It is not yet known whether natural infection of animals plays a role in public health epidemiology or has the potential to establish endemic reservoirs and threaten wildlife. SARS-CoV-2 has been observed to be capable of natural human-to-animal reverse zoonoses, transmitting from infected individuals into mink (11), dogs (12), and felines (13–15). American mink (Neovison vison) are currently the only species observed to have natural human-to-animal spillover and onward transmission (11). To date, at least 27 mink farms in The Netherlands, Spain, Denmark, and United States have reported outbreaks, including at least one probable case of mink-to-human transmission (16, 17).SARS-CoV-2 has also been shown to productively infect several species, including ferrets and domestic cats, in vivo (9, 10, 18, 19). Ferrets (Mustela putorius furo) are of special relevance to laboratory studies of respiratory viruses like Influenza A virus and recapitulate clinical pathophysiological aspects of human disease. Given their susceptibility to experimental infection and onward transmission via direct and indirect contact, ferrets have been proposed as an animal model to study SARS-CoV-2 transmission. Based on in vivo data, we expect all naïve ferrets in direct contact with an infected ferret will 1) become infected, 2) have measurable viral shedding or RNA via oral swabs up to 19 d postinfection, and 3) seroconvert with measurable antibodies against SARS-CoV-2 receptor binding domain (RBD) (18, 19).In March 2020, during the first wave of the SARS-CoV-2/COVID-19 pandemic in the New England area, we developed a rapid response study to investigate the potential for human-to-animal spillover and onward transmission in domestic, farm, and wildlife species (CoVERS: Coronavirus Epidemiological Response and Surveillance). The goal of CoVERS is to understand whether and how SARS-CoV-2 transmission is occurring at these interfaces, to refine public health guidelines, investigate whether there are additional risks to animal or human health associated with spillover, and evaluate the potential for establishment of endemic reservoirs. In the CoVERS in-home study, participants are sent a “swab and send” kit, which provides materials and instructions to safely take longitudinal nasal and oral samples from their animals, store them in their freezers, and send them back for viral screening. This community science approach allows wide surveillance with no risk of human transmission, as kits are decontaminated and opened in biosafety cabinets. Here, we highlight one enrolled household that created an exceptional natural experiment with direct relevance to our understanding of SARS-CoV-2 reverse zoonosis and animal models of disease.     

New norms for a new generation: cognitive performance in the framingham offspring cohort

A previous publication presented normative data on neuropsychological tests stratified by age, gender, and education based on the Original Cohort of the Framingham Heart Study. Many contemporary investigations include subject samples with higher levels of education, a factor known to affect cognitive performance. Secular change in education prompted the reexamination of norms in the children of the Original Cohort. The study population consisted of 853 men and 988 women from the Offspring Study, free of clinical neurological disease, who underwent a neuropsychological examination, which included tests given to their parents in 1974 to 1976 as well as additional newer tests to provide a more comprehensive battery. The Offspring population overall was more evenly distributed by gender and better educated. Their performance on cognitive tests was superior to that of the Original Cohort. Multivariable analyses revealed that more years of education explained only a part of the cohort differences. These findings suggest that continued surveillance of each generation is necessary to document the impact that unique social and economic variables have on cognitive function. Here, the authors provide updated normative data.     

Variation in125i-insulin absorption and blood glucose concentration

Summary The absorption of monocomponent porcine¹²⁵I-insulin Monotard and Isophane was studied in six insulin dependent diabetic patients over a period of 12 days. The absorption of insulin was measured as the disappearance of radioactivity from sites of injection. The daily¹²⁵I-insulin doses ranged from 20 to 48 IU between patients. The insulin absorbed varied considerably within and between patients. The range of individual daily absorbed insulin varied from 19 to 104 per cent of the¹²⁵I-insulin dose. A significant correlation (p<0.05) was found between insulin absorption and blood glucose concentration. Insulin absorption rates were relatively high before all hypoglycaemic episodes and reactive hyperglycaemia was only observed when relatively low insulin absorption rates followed the hypoglycaemic attack. The results show that lability in some insulin dependent diabetics is explained by variation in insulin absorption.     

Cardiac troponin I elevation in acute pulmonary embolism is associated with right ventricular dysfunction

OBJECTIVES: The purpose of this study was to evaluate the prevalence and diagnostic utility of cardiac troponin I to identify patients with right ventricular (RV) dysfunction in pulmonary embolism. BACKGROUND: Right ventricular overload resulting from elevated pulmonary resistance is a common finding in major pulmonary embolism. However, biochemical markers to assess the degree of RV dysfunction have not been evaluated so far. METHODS: In this prospective, double-blind study we included 36 study patients diagnosed as having acute pulmonary embolism. RESULTS: Among the whole study population, 14 patients (39%) had positive troponin I tests. Ten of 16 patients (62.5%) with RV dilatation had increased serum troponin I levels, while only 4 of 14 patients (28.6%) with elevated troponin I values had a normal RV diameter as assessed by echocardiography, indicating that positive troponin I tests were significantly associated with RV dilatation (p = 0.009). Patients with positive troponin I tests had significantly more segmental defects in ventilation/perfusion lung scans than patients with normal serum troponin I (p = 0.0002). CONCLUSIONS: Our data demonstrate that more than one-third of patients clinically diagnosed as having pulmonary embolism presented with elevated serum troponin I concentrations. Troponin I tests helped to identify patients with RV dilatation who had significantly more segmental defects in lung scans. Thus, troponin I assays are useful to detect minor myocardial damage in pulmonary embolism.     

Mortality and causes of death in Crohn's disease: follow-up of a population-based cohort in Copenhagen County,Denmark

BACKGROUND & AIMS: A population-based cohort comprising 374 patients with Crohn's disease diagnosed in Copenhagen County between 1962 and 1987 was observed until 1997 for mortality and causes of death. METHODS: Observed deaths were compared with expected deaths calculated by using individually computed person-years at risk and 1995 rates for Copenhagen County. Cumulative survival curves were calculated. RESULTS: A total of 84 deaths occurred vs. 67 expected (standardized mortality ratio [SMR], 1.3; 95% confidence interval [CI], 1.01-1.56): 45 women vs. 31.8 expected (SMR, 1.4; 95% CI, 1.03-1.89) and 39 men vs. 35.2 expected (SMR, 1.1; 95% CI, 0.79-1.51). An excess mortality was observed among women observed for 21-25 years after diagnosis. Among women aged <50 years at diagnosis, 25 deaths were observed vs. 7.3 expected (SMR, 3.42; 95% CI, 2.21-5.04). Fourteen (31%) of the observed deaths among women and 8 (21%) among men had a certain or possible connection to Crohn's disease. Among causes of death unrelated to Crohn's disease, an overrepresentation of gastrointestinal diseases, infections, and diseases of the urinary organs was observed. CONCLUSIONS: An increased mortality was observed late in the disease course that was most pronounced among women younger than 50 years at diagnosis and was attributed to death associated with severe Crohn's disease.