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The unprecedented genetic diversity found at vertebrate MHC (major histocompatibility complex) loci influences susceptibility to most infectious and autoimmune diseases. The evolutionary explanation for how these polymorphisms are maintained has been controversial. One leading explanation, antagonistic coevolution (also known as the Red Queen), postulates a never-ending molecular arms race where pathogens evolve to evade immune recognition by common MHC alleles, which in turn provides a selective advantage to hosts carrying rare MHC alleles. This cyclical process leads to negative frequency-dependent selection and promotes MHC diversity if two conditions are met: (i) pathogen adaptation must produce trade-offs that result in pathogen fitness being higher in familiar (i.e., host MHC genotype adapted to) vs. unfamiliar host MHC genotypes; and (ii) this adaptation must produce correlated patterns of virulence (i.e., disease severity). Here we test these fundamental assumptions using an experimental evolutionary approach (serial passage). We demonstrate rapid adaptation and virulence evolution of a mouse-specific retrovirus to its mammalian host across multiple MHC genotypes. Critically, this adaptive response results in trade-offs (i.e., antagonistic pleiotropy) between host MHC genotypes; both viral fitness and virulence is substantially higher in familiar versus unfamiliar MHC genotypes. These data are unique in experimentally confirming the requisite conditions of the antagonistic coevolution model of MHC evolution and providing quantification of fitness effects for pathogen and host. These data help explain the unprecedented diversity of MHC genes, including how disease-causing alleles are maintained.

Emerging evidence shows correlation between the presence of neutralization antibodies (nAbs) and protective immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently available commercial serology assays lack the ability to specifically identify nAbs. An enzyme-linked immunosorbent assay-based nAb assay (GenScript cPass neutralization antibody assay) has recently received emergency use authorization from the Food and Drug Administration. To evaluate the performance characteristics of this assay and compare and correlate it with the commercial assays that detect SARS-CoV-2-specific immunoglobulin G (IgG). Specimens from SARS-COV-2 infected patients (n = 124), healthy donors obtained prepandemic (n = 100), and patients with non-coronavirus disease 2019 (COVID-19) respiratory infections (n = 92) were analyzed using this assay. Samples with residual volume were also tested on 3 commercial serology platforms (Abbott, Euroimmun, Siemens). Twenty-eight randomly selected specimens from patients with COVID-19 and 10 healthy controls were subjected to a plaque reduction neutralization test. The cPass assay exhibited 96.1% (95% CI, 94.9%-97.3%) sensitivity (at >14 days post-positive PCR), 100% (95% CI, 98.0%-100.0%) specificity, and zero cross-reactivity for the presence of non-COVID-19 respiratory infections. When compared with the plaque reduction assay, 97.4% (95% CI, 96.2%-98.5%) qualitative agreement and a positive correlation (R2 = 0.76) was observed. Comparison of IgG signals from each of the commercial assays with the nAb results from plaque reduction neutralization test/cPass assays displayed greater than 94.7% qualitative agreement and correlations with R2 = 0.43/0.68 (Abbott), R2 = 0.57/0.85 (Euroimmun), and R2 = 0.39/0.63 (Siemens), respectively. The combined data support the use of cPass assay for accurate detection of the nAb response. Positive IgG results from commercial assays associated reasonably with nAbs presence and can serve as a substitute.

Furthermore, in the context of the Affordable Care Act (ACA), a grade A recommendation for preventive services mandates that health plans, both private and public, will provide cov- erage without out-of-pocket expenses or copayments for the patient. Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 re- quirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

The aim of this study was to establish age appropriate reference intervals for calcium (Ca), phosphorus (P) and total protein (UTP) in random urine samples. All analytes were measured using the Roche MODULAR P analyzer and normalized to creatinine (Cr). Our study cohort consisted of 674 boys and 728 girls between 7 and 17 years old (y.o.), which allowed us to determine the central 95% reference intervals with 90% confidence intervals by non-parametric analysis partitioned by both gender and 2-year age intervals for each analyte [i.e. boys in age group 7–9 years (7–9 boys); girls in age group 7–9 years (7–9 girls), etc.]. Results for the upper limits of the central 95% reference interval were: for Ca/Cr, 0.27 (16,17 y.o.) to 0.46 mg/mg (7–9 y.o.) for the girls and 0.26 (16,17 y.o.) to 0.43 mg/mg (7–9 y.o.) for the boys; for P/Cr, 0.85 (16,17 y.o.) to 1.44 mg/mg (7–9 y.o.) for the girls and 0.87 (16,17 y.o.) to 1.68 mg/mg (7–9 y.o.) for the boys; for UTP/Cr, 0.30 (7–9 y.o.) to 0.34 mg/mg (10–12 y.o.) for the girls and 0.19 (16,17, y.o.) to 0.26 mg/mg (13–15 y.o.) for the boys. Upper reference limits decreased with increasing age, and age was a statistically significant variable for all analytes. Eight separate age- and gender-specific reference intervals are proposed per analyte.

The COVID-19 pandemic placed health care personnel (HCP) at risk for stress, anxiety, burnout, and post-traumatic stress disorder (PTSD). To address this, hospitals developed programs to mitigate risk. The objectives of the current study were to measure the availability and use of these programs in a cohort of academic emergency departments (EDs) in the United States early in the pandemic and identify factors associated with program use. Cross-sectional survey of ED HCP in 21 academic EDs in 15 states between June and September 2020. Site investigators provided data on the availability of 28 programs grouped into 9 categories. Individual support programs included: financial, workload mitigation, individual COVID-19 testing, emotional (e.g., mental health hotline), and instrumental (e.g., childcare) Clinical work support programs included: COVID-19 team communication (e.g., debriefing critical incident), patient-family communication facilitation, patient services (e.g., social work, ethics consultation), and system-level exposure reduction. Participants provided corresponding data on whether they used the programs. We used generalized linear mixed models clustered on site to measure the association between demographic and facility characteristics and program use. We received 1,541 survey responses (96% response rate) from emergency physicians or advanced practice providers, nurses, and nonclinical staff. Program availability in each of the 9 categories was high (>95% of hospitals). Program use was variable, with clinical work support programs used more frequently (28-50% of eligible HCP across categories) than individual employee support programs (6-13% of eligible HCP across categories). Fifty-seven percent of respondents reported that the COVID-19 pandemic had affected their stress and anxiety, and 12% were at elevated risk for PTSD. Program use did not significantly differ for HCP who reported symptoms of anxiety and/or stress compared to those who did not. Early in the pandemic, support programs were widely available to ED HCP, but program use was low. Future work will focus on identifying barriers and facilitators to use and specific programs most likely to be effective during periods of highest occupational stress.

Epidemiologic studies combining exposure and outcome data with the collection of biosamples are needed to study gene-environment interactions that might contribute to the etiology of complex diseases such as pediatric Crohn's disease (CD). Nationwide registries, including those in Denmark and other Scandinavian countries, provide efficient and reliable sources of data for epidemiological studies evaluating the environmental determinants of disease. We performed a pilot study to test the feasibility of collecting salivary DNA to augment registry data in established cases of pediatric CD and randomly selected, population-based controls. Cases of CD born after 1995 and residing in the central region of Denmark were identified through the Danish National Patient Registry and confirmed by using standard diagnostic criteria. Age- and gender-matched controls were selected at random through the civil registration system. Cases and controls were contacted by mail and telephone and invited to submit a saliva sample. DNA was extracted and genotyped for six CD-associated single-nucleotide polymorphisms (SNPs). A total of 53 cases of pediatric CD were invited, and 40 contributed a saliva sample (75% response rate). A total of 126 controls were invited, and 54 contributed a saliva sample (44% response rate). As expected, demographic characteristics did not differ between cases and controls. DNA was successfully isolated from 93 of 94 samples. Genotyping was performed with only 2% undetermined genotypes. For five of six SNPs known to be associated with CD, risk allele frequencies were higher in cases than controls. This pilot study strongly supports the feasibility of augmenting traditional epidemiological data from Danish population-based registries with the de novo collection of genetic information from population-based cases and controls. This will facilitate rigorous studies of gene-environment interactions in complex chronic conditions such as CD.