CD8(+) T-Cell Responses to Trypanosoma cruzi Are Highly Focused on Strain-Variant trans-Sialidase Epitopes

CD8(+) T cells are crucial for control of a number of medically important protozoan parasites, including Trypanosoma cruzi, the agent of human Chagas disease. Yet, in contrast to the wealth of information from viral and bacterial infections, little is known about the antigen specificity or the general development of effector and memory T-cell responses in hosts infected with protozoans. In this study we report on a wide-scale screen for the dominant parasite peptides recognized by CD8(+) T cells in T. cruzi–infected mice and humans. This analysis demonstrates that in both hosts the CD8(+) T-cell response is highly focused on epitopes encoded by members of the large trans-sialidase family of genes. Responses to a restricted set of immunodominant peptides were especially pronounced in T. cruzi–infected mice, with more than 30% of the CD8(+) T-cell response at the peak of infection specific for two major groups of trans-sialidase peptides. Experimental models also demonstrated that the dominance patterns vary depending on the infective strain of T. cruzi, suggesting that immune evasion may be occurring at a population rather than single-parasite level

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Parasite Strain–Dependent Dominance Patterns in T. cruzi–Infected Mice

<p>B6 mice were infected with 1,000 Brazil, 1,000 Y, or 10,000 CL strain T. cruzi and stained with TSKB20/K^b (top) or TSKB18/K^b (bottom) tetramers as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0020077#s4" target="_blank">Materials and Methods</a>. Data shown are a combination of two separate experiments with three or four mice per group per experiment.</p

Detection of CD8⁺ T Lymphocytes Recognizing HLA-A2.1–Restricted ts Epitopes in Patients with Chronic Chagas Disease

<p>PBMCs were stained using MHC tetramers specific for the TSA2–38 or TSA2–44 epitopes. The percentage of CD8⁺ T cells staining positive for TSA2–38 is shown for a representative chronic chagasic patient and an uninfected control. Cells shown are lymphocytes gated on CD4^negB220^negCD11b^neg lymphocytes. Five out of eight IFNγ ELISPOT⁺ subjects stained positive with tetramers.</p

Relative Frequencies of Epitope Occurrences in the Genome and CD8⁺ T-Cell Responses

<div><p>(A) Venn diagram representing relative frequencies and overlap of T cells responding to T. cruzi epitopes. The blue shaded circles (left) show the high-abundance overlapping peptides TSKB21 and TSKB20, along with the low-abundance overlapping peptide TSKB260. These peptides are among the most highly represented H-2K^b–binding peptides in the proteome and elicit the strongest CD8⁺ T-cell response following infection with Brazil strain <i>T. cruzi,</i> as shown in (B). The smaller purple shaded circles (right) show the lower-abundance epitopes TSKB18, TSKB74, TSKB80, and TSKB89, which are recognized by T-cell populations that overlap minimally with TSKB20/21/260-specific T cells.</p><p>(B) Relative frequencies of CD8⁺ T cells recognizing the TSKB20 (blue) and TSKB18 (purple) families of peptides in the acute (left) and chronic (right) phase of T. cruzi infection in mice infected with three different strains. While there are strain-dependent differences in the magnitude of the TSKB20-specific T-cell responses, these responses all follow a similar pattern of expansion and contraction during acute infection, which may be explained simply by strain-dependent differences in the rates of parasite replication and/or expression levels of TSKB20. However, T-cell responses to TSKB18 vary remarkably in both their magnitude and kinetics following infection with the various strains. Sustained expansion of TSKB18-specific T cells following infection with CL or Y strains results in different hierarchies of Ag-specific CD8⁺ T cells in chronic infection with the three different strains (right).</p></div

Magnitude, Kinetics, and Cross-Reactivity of CD8⁺ T-Cell Responses to Dominant ts Epitopes

<div><p>(A) SCs from naive or chronically infected (Brazil) B6 mice were stained with TSKB20/K^b-PE tetramers, then anti-CD8 APCs and a Cy5PE exclusion channel consisting of anti-CD4, anti-CD11b, and anti-B220. Cells shown are gated on Cy5PE^neglymphocyte⁺ populations. Numbers represent the percentage of CD8⁺ T cells staining with the TSKB20/K^b tetramer.</p><p>(B) Kinetics of TSKB20 (closed triangles)– and TSKB18 (open triangles)–specific responses during Brazil strain infection of B6 mice. Data are representative of three experiments (<i>n</i> = 5 mice per group).</p><p>(C) SCs from infected mice were stained with anti-CD8–FITC, TSKB20/K^b-PE, anti-CD4/11b/B220 cocktail, and either TSKB18/K^b–APC (top) or TSKB21/K^b–APC (bottom). Left panel shows CD8 versus TSKB20/K^b; middle panel shows CD8 versus TSKB18/K^b or TSKB21/K^b; right panel shows TSKB18/K^b or TSKB21/K^b tetramer staining versus TSKB20/K^b staining, gated on CD8⁺ lymphocytes.</p></div

Functional Responses of Murine CD8⁺ T Cells Directed against Non-ts Epitopes

<div><p>(A) SCs from naive (gray bars) or chronically infected (Brazil strain; black bars) B6 mice were stimulated for 5 h with TSKB20, cruzipain, or GFT peptides plus GolgiPlug as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0020077#s4" target="_blank">Materials and Methods</a>. Data represent the number of CD8⁺ T cells producing IFNγ; error bars represent SD.</p><p>(B) SCs from naive B6 mice were loaded with T. cruzi peptides and labeled with CFSE as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0020077#s4" target="_blank">Materials and Methods</a>. The numbers above the peaks represent the percentage of specific killing of the target cells loaded with the indicated peptide and was calculated as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0020077#s4" target="_blank">Materials and Methods</a>. Data are representative of three experiments.</p></div

The Coronary Artery Disease-Reporting and Data System (CAD-RADS): Prognostic and Clinical Implications Associated With Standardized Coronary Computed Tomography Angiography Reporting.

OBJECTIVES:This study sought to assess clinical outcomes associated with the novel Coronary Artery Disease-Reporting and Data System (CAD-RADS) scores used to standardize coronary computed tomography angiography (CTA) reporting and their potential utility in guiding post-coronary CTA care. BACKGROUND:Clinical decision support is a major focus of health care policies aimed at improving guideline-directed care. Recently, CAD-RADS was developed to standardize coronary CTA reporting and includes clinical recommendations to facilitate patient management after coronary CTA. METHODS:In the multinational CONFIRM (COronary CT Angiography EvaluatioN For Clinical Outcomes: An InteRnational Multicenter) registry, 5,039 patients without known coronary artery disease (CAD) underwent coronary CTA and were stratified by CAD-RADS scores, which rank CAD stenosis severity as 0 (0%), 1 (1% to 24%), 2 (25% to 49%), 3 (50% to 69%), 4A (70% to 99% in 1 to 2 vessels), 4B (70% to 99% in 3 vessels or ≥50% left main), or 5 (100%). Kaplan-Meier and multivariable Cox models were used to estimate all-cause mortality or myocardial infarction (MI). Receiver-operating characteristic (ROC) curves were used to compare CAD-RADS to the Duke CAD Index and traditional CAD classification. Referrals to invasive coronary angiography (ICA) after coronary CTA were also assessed. RESULTS:Cumulative 5-year event-free survival ranged from 95.2% to 69.3% for CAD-RADS 0 to 5 (p &lt; 0.0001). Higher scores were associated with elevations in event risk (hazard ratio: 2.46 to 6.09; p &lt; 0.0001). The ROC curve for prediction of death or MI was 0.7052 for CAD-RADS, which was noninferior to the Duke Index (0.7073; p = 0.893) and traditional CAD classification (0.7095; p = 0.783). ICA rates were 13% for CAD-RADS 0 to 2, 66% for CAD-RADS 3, and 84% for CAD-RADS ≥4A. For CAD-RADS 3, 58% of all catheterizations occurred within the first 30 days of follow-up. In a patient subset with available medication data, 57% of CAD-RADS 3 patients who received 30-day ICA were either asymptomatic or not receiving antianginal therapy at baseline, whereas only 32% had angina and were receiving medical therapy. CONCLUSIONS:CAD-RADS effectively identified patients at risk for adverse events. Frequent ICA use was observed among patients without severe CAD, many of whom were asymptomatic or not taking antianginal drugs. Incorporating CAD-RADS into coronary CTA reports may provide a novel opportunity to promote evidence-based care post-coronary CTA