Implication of different domains of the Leishmania major metacaspase in cell death and autophagy

International audienceMetacaspases (MCAs) are cysteine peptidases expressed in plants, fungi and protozoa, with a caspase-like histidine-cysteine catalytic dyad, but differing from caspases, for example, in their substrate specificity. The role of MCAs is subject to debate: roles in cell cycle control, in cell death or even in cell survival have been suggested. In this study, using a Leishmania major MCA-deficient strain, we showed that L. major MCA (LmjMCA) not only had a role similar to caspases in cell death but also in autophagy and this through different domains. Upon cell death induction by miltefosine or H2O2, LmjMCA is processed, releasing the catalytic domain, which activated substrates via its catalytic dyad His/Cys and a proline-rich C-terminal domain. The C-terminal domain interacted with proteins, notably proteins involved in stress regulation, such as the MAP kinase LmaMPK7 or programmed cell death like the calpain-like cysteine peptidase. We also showed a new role of LmjMCA in autophagy, acting on or upstream of ATG8, involving Lmjmca gene overexpression and interaction of the C-terminal domain of LmjMCA with itself and other proteins. These results allowed us to propose two models, showing the role of LmjMCA in the cell death and also in the autophagy pathway, implicating different protein domains

Group IIA secreted phospholipase A2 is associated with the pathobiology leading to COVID-19 mortality

There is an urgent need to identify the cellular and molecular mechanisms responsible for severe COVID-19 that results in death. We initially performed both untargeted and targeted lipidomics as well as focused biochemical analyses of 127 plasma samples and found elevated metabolites associated with secreted phospholipase A2 (sPLA2) activity and mitochondrial dysfunction in patients with severe COVID-19. Deceased COVID-19 patients had higher levels of circulating, catalytically active sPLA2 group IIA (sPLA2-IIA), with a median value that was 9.6-fold higher than that for patients with mild disease and 5.0-fold higher than the median value for survivors of severe COVID-19. Elevated sPLA2-IIA levels paralleled several indices of COVID-19 disease severity (e.g., kidney dysfunction, hypoxia, multiple organ dysfunction). A decision tree generated by machine learning identified sPLA2-IIA levels as a central node in the stratification of patients who died from COVID-19. Random forest analysis and least absolute shrinkage and selection operator-based (LASSO-based) regression analysis additionally identified sPLA2-IIA and blood urea nitrogen (BUN) as the key variables among 80 clinical indices in predicting COVID-19 mortality. The combined PLA-BUN index performed significantly better than did either one alone. An independent cohort (n = 154) confirmed higher plasma sPLA2-IIA levels in deceased patients compared with levels in plasma from patients with severe or mild COVID-19, with the PLA-BUN index-based decision tree satisfactorily stratifying patients with mild, severe, or fatal COVID-19. With clinically tested inhibitors available, this study identifies sPLA2-IIA as a therapeutic target to reduce COVID-19 mortality. © 2021, American Society for Clinical Investigation.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

SARS-CoV-2 rapid antigen testing of symptomatic and asymptomatic individuals on the University of Arizona campus

SARS-CoV-2, the cause of COVID19, has caused a pandemic that has infected more than 80 M and killed more than 1.6 M persons worldwide. In the US as of December 2020, it has infected more than 32 M people while causing more than 570,000 deaths. As the pandemic persists, there has been a public demand to reopen schools and university campuses. To consider these demands, it is necessary to rapidly identify those individuals infected with the virus and isolate them so that disease transmission can be stopped. In the present study, we examined the sensitivity of the Quidel Rapid Antigen test for use in screening both symptomatic and asymptomatic individuals at the University of Arizona from June to August 2020. A total of 885 symptomatic and 1551 asymptomatic subjects were assessed by antigen testing and real-time PCR testing. The sensitivity of the test for both symptomatic and asymptomatic persons was between 82 and 90%, with some caveats. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Humoral Immune Response to mRNA COVID-19 Vaccination Among Children 5-11 in a Multisite Prospective Cohort study, September 2021-September 2022

Abstract Background The PROTECT study is a longitudinal cohort study initiated in July 2021 with weekly testing for SARS-CoV-2 in four states: Arizona, Florida, Texas, and Utah. This study aims to examine the protective effect of vaccine-elicited antibody response against post-vaccination SARS-CoV-2 infections. Methods Participants, children aged 5-11, had serum collected 14-59 days after second dose of monovalent Pfizer-BioNTech COVID-19 mRNA vaccine. Vaccine-elicited antibodies were measured by area under the curve (AUC) and endpoint titer by ELISA (RBD and S2) and surrogate neutralization (SN) assays against ancestral (WA1) and Omicron (BA.2). Results Among 79 vaccinated participants, (33 [41.7%] female; median age 8.8 [SD 1.9] years), 48 (60.8%) were from Tucson, Arizona, 64 (81.0%) were non-Hispanic white, 63 (80.8%) attended school in person, 68 (86.1%) did not have any chronic conditions, 56 (72.7%) did not take daily medications; and 47 (59.5%) were infected after vaccination. Uninfected children had higher AUCs after vaccination against WA1 (p = 0.0093) and Omicron (p = 0.018). The geometric mean SN titer above the limit of detection was 346.0 for WA1 and 39.7 for Omicron, an 8.7-fold decrease (p = <0.0001). After adjustment of covariates in the WA1-specific model, we observed a 47% reduction in the odds of a post-vaccination infection for every standard deviation increase of RBD AUC (aOR: 0.53, 95% CI: 0.29, 0.97) and a 69% reduction in the odds of infection for every three-fold increase in RBD end titer, (aOR: 0.31, 95% CI: 0.06, 1.57). Conclusion Children with higher antibody levels experienced lower incidence of post-vaccination SARS-CoV-2 infection