Coronavirus disease 2019 (COVID-19), the novel respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is associated with severe morbidity and mortality. The ...rollout of diagnostic testing in the United States was slow, leading to numerous cases that were not tested for SARS-CoV-2 in February and March 2020 and necessitating the use of serological testing to determine past infections. Here, we evaluated the Abbott SARS-CoV-2 IgG test for detection of anti-SARS-CoV-2 IgG antibodies by testing 3 distinct patient populations. We tested 1,020 serum specimens collected prior to SARS-CoV-2 circulation in the United States and found one false positive, indicating a specificity of 99.90%. We tested 125 patients who tested reverse transcription-PCR (RT-PCR) positive for SARS-CoV-2 for whom 689 excess serum specimens were available and found that sensitivity reached 100% at day 17 after symptom onset and day 13 after PCR positivity. Alternative index value thresholds for positivity resulted in 100% sensitivity and 100% specificity in this cohort. We tested specimens from 4,856 individuals from Boise, ID, collected over 1 week in April 2020 as part of the Crush the Curve initiative and detected 87 positives for a positivity rate of 1.79%. These data demonstrate excellent analytical performance of the Abbott SARS-CoV-2 IgG test as well as the limited circulation of the virus in the western United States. We expect that the availability of high-quality serological testing will be a key tool in the fight against SARS-CoV-2.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of an ongoing pandemic, with increasing deaths worldwide. To date, documentation of the histopathological features in fatal ...cases of the disease caused by SARS-CoV-2 (COVID-19) has been scarce due to sparse autopsy performance and incomplete organ sampling. We aimed to provide a clinicopathological report of severe COVID-19 cases by documenting histopathological changes and evidence of SARS-CoV-2 tissue tropism.
In this case series, patients with a positive antemortem or post-mortem SARS-CoV-2 result were considered eligible for enrolment. Post-mortem examinations were done on 14 people who died with COVID-19 at the King County Medical Examiner's Office (Seattle, WA, USA) and Snohomish County Medical Examiner's Office (Everett, WA, USA) in negative-pressure isolation suites during February and March, 2020. Clinical and laboratory data were reviewed. Tissue examination was done by light microscopy, immunohistochemistry, electron microscopy, and quantitative RT-PCR.
The median age of our cohort was 73·5 years (range 42–84; IQR 67·5–77·25). All patients had clinically significant comorbidities, the most common being hypertension, chronic kidney disease, obstructive sleep apnoea, and metabolic disease including diabetes and obesity. The major pulmonary finding was diffuse alveolar damage in the acute or organising phases, with five patients showing focal pulmonary microthrombi. Coronavirus-like particles were detected in the respiratory system, kidney, and gastrointestinal tract. Lymphocytic myocarditis was observed in one patient with viral RNA detected in the tissue.
The primary pathology observed in our cohort was diffuse alveolar damage, with virus located in the pneumocytes and tracheal epithelium. Microthrombi, where observed, were scarce and endotheliitis was not identified. Although other non-pulmonary organs showed susceptibility to infection, their contribution to the pathogenesis of SARS-CoV-2 infection requires further examination.
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Eukaryotic cells can initiate several distinct programmes of self-destruction, and the nature of the cell death process (non-inflammatory or proinflammatory) instructs responses of neighbouring ...cells, which in turn dictates important systemic physiological outcomes. Pyroptosis, or caspase 1-dependent cell death, is inherently inflammatory, is triggered by various pathological stimuli, such as stroke, heart attack or cancer, and is crucial for controlling microbial infections. Pathogens have evolved mechanisms to inhibit pyroptosis, enhancing their ability to persist and cause disease. Ultimately, there is a competition between host and pathogen to regulate pyroptosis, and the outcome dictates life or death of the host.
Zika virus (ZIKV) can be transmitted sexually between humans. However, it is unknown whether ZIKV replicates in the vagina and impacts the unborn fetus. Here, we establish a mouse model of vaginal ...ZIKV infection and demonstrate that, unlike other routes, ZIKV replicates within the genital mucosa even in wild-type (WT) mice. Mice lacking RNA sensors or transcription factors IRF3 and IRF7 resulted in higher levels of local viral replication. Furthermore, mice lacking the type I interferon (IFN) receptor (IFNAR) became viremic and died of infection after a high-dose vaginal ZIKV challenge. Notably, vaginal infection of pregnant dams during early pregnancy led to fetal growth restriction and infection of the fetal brain in WT mice. This was exacerbated in mice deficient in IFN pathways, leading to abortion. Our study highlights the vaginal tract as a highly susceptible site of ZIKV replication and illustrates the dire disease consequences during pregnancy.
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•Zika virus replicates in the vaginal tract of wild-type virgin and pregnant mice•Innate RNA sensors and type I interferons control vaginal Zika virus replication•Vaginal Zika virus infection in early pregnancy leads to fetal growth restriction•Vaginal Zika virus infection of pregnant dams leads to fetal brain infection
Vaginal mucosa is permissive to the replication of Zika virus, and infection through this route can lead to fetal brain infection even in mice with an intact immune system.
Summary
Salmonella enterica serovar Typhimurium invades host macrophages and induces a unique caspase‐1‐dependent pathway of cell death termed pyroptosis, which is activated during bacterial ...infection in vivo. We demonstrate DNA cleavage during pyroptosis results from caspase‐1‐stimulated nuclease activity. Although poly(ADP‐ribose) polymerase (PARP) activation by fragmented DNA depletes cellular ATP to cause lysis during oncosis, the rapid lysis characteristic of Salmonella‐infected macrophages does not require PARP activity or DNA fragmentation. Membrane pores between 1.1 and 2.4 nm in diameter form during pyroptosis of host cells and cause swelling and osmotic lysis. Pore formation requires host cell actin cytoskeleton rearrangements and caspase‐1 activity, as well as the bacterial type III secretion system (TTSS); however, insertion of functional TTSS translocons into the host membrane is not sufficient to directly evoke pore formation. Concurrent with pore formation, inflammatory cytokines are released from infected macrophages. This mechanism of caspase‐1‐mediated cell death provides additional experimental evidence supporting pyroptosis as a novel pathway of inflammatory programmed cell death.
Caspase-1 cleaves the inactive IL-1β and IL-18 precursors into active inflammatory cytokines. In Salmonella-infected macrophages, caspase-1 also mediates a pathway of proinflammatory programmed cell ...death termed "pyroptosis." We demonstrate active caspase-1 diffusely distributed in the cytoplasm and localized in discrete foci within macrophages responding to either Salmonella infection or intoxication by Bacillus anthracis lethal toxin (LT). Both stimuli triggered caspase-1-dependent lysis in macrophages and dendritic cells. Activation of caspase-1 by LT required binding, uptake, and endosome acidification to mediate translocation of lethal factor (LF) into the host cell cytosol. Catalytically active LF cleaved cytosolic substrates and activated caspase-1 by a mechanism involving proteasome activity and potassium efflux. LT activation of caspase-1 is known to require the inflammasome adapter Nalp1. In contrast, Salmonella infection activated caspase-1 through an independent pathway requiring the inflammasome adapter Ipaf. These distinct mechanisms of caspase-1 activation converged on a common pathway of caspase-1-dependent cell death featuring DNA cleavage, cytokine activation, and, ultimately, cell lysis resulting from the formation of membrane pores between 1.1 and 2.4 nm in diameter and pathological ion fluxes that can be blocked by glycine. These findings demonstrate that distinct activation pathways elicit the conserved cell death effector mechanism of caspase-1-mediated pyroptosis and support the notion that this pathway of proinflammatory programmed cell death is broadly relevant to cell death and inflammation invoked by diverse stimuli.
Background Efforts to minimize COVID-19 exposure during the current SARS-CoV-2 pandemic have led to limitations in access to medical care and testing. The Tasso-SST kit includes all of the components ...necessary for remote, capillary blood self-collection. In this study, we sought to investigate the accuracy and reliability of the Tasso-SST device as a self-collection device for measurement of SARS-CoV-2 IgG antibodies. Methods Capillary blood was obtained via unsupervised and supervised application of the Tasso-SST device, and venous blood was collected by standard venipuncture. Unsupervised self-collected blood samples underwent either extreme summer or winter-simulated shipping conditions prior to testing. Sera obtained by all three methods were tested concurrently using the EuroImmun anti-SARS-CoV-2 S1 IgG assay in a CLIA-certified clinical laboratory. Results Successful Tasso-SST capillary blood collection by unsupervised and supervised administration was completed by 93.4% and 94.5% of participants, respectively. Sera from 56 participants, 55 with documented (PCR+) COVID-19, and 33 healthy controls were then tested for anti-SARS-CoV-2 IgG antibodies. Compared to venous blood results, Tasso-SST-collected (unstressed) and the summer- and winter-stressed blood samples demonstrated Deming regression slopes of 1.00 (95% CI: 0.99-1.02), 1.00 (95% CI: 0.98-1.01), and 0.99 (95% CI: 0.97-1.01), respectively, with an overall accuracy of 98.9%. Conclusions Capillary blood self-collection using the Tasso-SST device had a high success rate. Moreover, excellent concordance was found for anti-SARS-CoV-2 IgG results between Tasso-SST capillary and standard venous blood-derived sera. The Tasso-SST device should enable widespread collection of capillary blood for testing without medical supervision, facilitating epidemiologic studies.
Salmonella enterica are facultatively intracellular pathogens causing diseases with markedly visible signs of inflammation. During infection, Salmonella interacts with various host cell types, often ...resulting in death of those cells. Salmonella induces intestinal epithelial cell death via apoptosis, a cell death programme with a notably non-inflammatory outcome. In contrast, macrophage infection triggers caspase-1-dependent proinflammatory programmed cell death, a recently recognized process termed pyroptosis, which is distinguished from other forms of cellular demise by its unique mechanism, features and inflammatory outcome. Rapid macrophage pyroptosis depends on the Salmonella pathogenicity island-1 type III secretion system (T3SS) and flagella. Salmonella dynamically modulates induction of macrophage pyroptosis, and regulation of T3SS systems permits bacterial replication in specialized intracellular niches within macrophages. However, these infected macrophages later undergo a delayed form of caspase-1-dependent pyroptosis. Caspase-1-deficient mice are more susceptible to a number of bacterial infections, including salmonellosis, and pyroptosis is therefore considered a generalized protective host response to infection. Thus, Salmonella-induced pyroptosis serves as a model to understand a broadly important pathway of proinflammatory programmed host cell death: examining this system affords insight into mechanisms of both beneficial and pathological cell death and strategies employed by pathogens to modulate host responses.
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