Association of obesity with venous thromboembolism and myocardial injury in COVID-19.

INTRODUCTION: Although both obesity and coronavirus disease 2019 (COVID-19) independently induce inflammation and thrombosis, the association between obesity class and risk of thrombosis in patients with COVID-19 remains unclear. METHODS: This retrospective cohort study included consecutive patients hospitalized with COVID-19 at a single institution. Patients were categorized based on obesity class. The main outcomes were venous thromboembolism (VTE) and myocardial injury, a marker of microvascular thrombosis in COVID-19. Adjustments were made for sociodemographic variables, cardiovascular disease risk factors and comorbidities. RESULTS: 609 patients with COVID-19 were included. 351 (58%) patients were without obesity, 110 (18%) were patients with class I obesity, 76 (12%) were patients with class II obesity, and 72 (12%) were patients with class III obesity. Patients with class I and III obesity had significantly higher risk-adjusted odds of VTE compared to patients without obesity (OR = 2.54, 95% CI: 1.05-6.14 for class I obesity; and OR = 3.95, 95% CI: 1.40-11.14 for class III obesity). Patients with class III obesity had significantly higher risk-adjusted odds of myocardial injury compared to patients without obesity (OR = 2.15, 95% CI: 1.12-4.12). Both VTE and myocardial injury were significantly associated with greater risk-adjusted odds of mortality. CONCLUSION: This study demonstrates that both macrovascular and microvascular thromboses may contribute to the elevated morbidity and mortality in patients with obesity and COVID-19.

Multimodality Imaging in the Diagnosis of Prosthetic Valve Endocarditis: A Brief Review.

Infective endocarditis is a common and treatable condition that carries a high mortality rate. Currently the workup of infective endocarditis relies on the integration of clinical, microbiological and echocardiographic data through the use of the modified Duke criteria (MDC). However, in cases of prosthetic valve endocarditis (PVE) echocardiography can be normal or non-diagnostic in a high proportion of cases leading to decreased sensitivity for the MDC. Evolving multimodality imaging techniques including leukocyte scintigraphy (white blood cell imaging), 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), multidetector computed tomographic angiography (MDCTA), and cardiac magnetic resonance imaging (CMRI) may each augment the standard workup of PVE and increase diagnostic accuracy. While further studies are necessary to clarify the ideal role for each of these imaging techniques, nevertheless, these modalities hold promise in determining the diagnosis, prognosis, and care of PVE. We start by presenting a clinical vignette, then evidence supporting various modality strategies, balanced by limitations, and review of formal guidelines, when available. The article ends with the authors' summary of future directions and case conclusion.

An assessment of transesophageal echocardiography studies rated as rarely appropriate tests for infective endocarditis at an academic medical center.

PURPOSE: Endocardial involvement documented by echocardiography is a major criterion of the modified Duke criteria (MDC) for infective endocarditis (IE). Though transesophageal echocardiography (TEE) is sensitive in the diagnosis of IE, it can be inappropriately used. METHODS: This retrospective study included all patients who underwent TEE due to bacteremia, fever, and/or endocarditis in a single, tertiary academic medical center in 2013. Data collected from electronic medical charts were as follows: demographics, history, physical examination, blood cultures, and transthoracic (TTE) and TEE findings. Cases were categorized based on appropriate use criteria (AUC) and MDC. An infectious disease (ID) specialist reviewed cases with rarely appropriate TEE use. RESULTS: In the 194 patients included, 147 (75.8%) were rated as appropriate, 36 (18.6%) rarely appropriate, and 11 (5.6%) uncertain. Of the 36 with rarely appropriate TEEs, using MDC 31 (86%) were rejected and 5 (14%) were possible for IE. Retrospective chart review by an ID specialist determined that 10 of these patients warranted TEE due to compelling issues, including immunosuppression or complicated infection. CONCLUSIONS: In this retrospective cohort, almost one fifth of cases were rated as rarely appropriate. However, a review of these cases showed that TEE was often pursued when the clinical situation involved immunosuppression or complex infectious process. There remains room for improvement to our screening process for TEE and a need to implement a nuanced educational plan to better precisely identify appropriate cases for TEE usage.

Interplay between Target Sequences and Repair Pathways Determines Distinct Outcomes of AID-Initiated Lesions.

Activation-induced deaminase (AID) functions by deaminating cytosines and causing U:G mismatches, a rate-limiting step of Ab gene diversification. However, precise mechanisms regulating AID deamination frequency remain incompletely understood. Moreover, it is not known whether different sequence contexts influence the preferential access of mismatch repair or uracil glycosylase (UNG) to AID-initiated U:G mismatches. In this study, we employed two knock-in models to directly compare the mutability of core Sµ and VDJ exon sequences and their ability to regulate AID deamination and subsequent repair process. We find that the switch (S) region is a much more efficient AID deamination target than the V region. Igh locus AID-initiated lesions are processed by error-free and error-prone repair. S region U:G mismatches are preferentially accessed by UNG, leading to more UNG-dependent deletions, enhanced by mismatch repair deficiency. V region mutation hotspots are largely determined by AID deamination. Recurrent and conserved S region motifs potentially function as spacers between AID deamination hotspots. We conclude that the pattern of mutation hotspots and DNA break generation is influenced by sequence-intrinsic properties, which regulate AID deamination and affect the preferential access of downstream repair. Our studies reveal an evolutionarily conserved role for substrate sequences in regulating Ab gene diversity and AID targeting specificity.

Combined deletion of Xrcc4 and Trp53 in mouse germinal center B cells leads to novel B cell lymphomas with clonal heterogeneity.

BACKGROUND: Activated B lymphocytes harbor programmed DNA double-strand breaks (DSBs) initiated by activation-induced deaminase (AID) and repaired by non-homologous end-joining (NHEJ). While it has been proposed that these DSBs during secondary antibody gene diversification are the primary source of chromosomal translocations in germinal center (GC)-derived B cell lymphomas, this point has not been directly addressed due to the lack of proper mouse models. METHODS: In the current study, we establish a unique mouse model by specifically deleting a NHEJ gene, Xrcc4, and a cell cycle checkpoint gene, Trp53, in GC B cells, which results in the spontaneous development of B cell lymphomas that possess features of GC B cells. RESULTS: We show that these NHEJ deficient lymphomas harbor translocations frequently targeting immunoglobulin (Ig) loci. Furthermore, we found that Ig translocations were associated with distinct mechanisms, probably caused by AID- or RAG-induced DSBs. Intriguingly, the AID-associated Ig loci translocations target either c-myc or Pvt-1 locus whereas the partners of RAG-associated Ig translocations scattered randomly in the genome. Lastly, these NHEJ deficient lymphomas harbor complicated genomes including segmental translocations and exhibit a high level of ongoing DNA damage and clonal heterogeneity. CONCLUSIONS: We propose that combined NHEJ and p53 defects may serve as an underlying mechanism for a high level of genomic complexity and clonal heterogeneity in cancers.

AID-initiated DNA lesions are differentially processed in distinct B cell populations.

Activation-induced deaminase (AID) initiates U:G mismatches, causing point mutations or DNA double-stranded breaks at Ig loci. How AID-initiated lesions are prevented from inducing genome-wide damage remains elusive. A differential DNA repair mechanism might protect certain non-Ig loci such as c-myc from AID attack. However, determinants regulating such protective mechanisms are largely unknown. To test whether target DNA sequences modulate protective mechanisms via altering the processing manner of AID-initiated lesions, we established a knock-in model by inserting an Sγ2b region, a bona fide AID target, into the first intron of c-myc. Unexpectedly, we found that the inserted S region did not mutate or enhance c-myc genomic instability, due to error-free repair of AID-initiated lesions, in Ag-stimulated germinal center B cells. In contrast, in vitro cytokine-activated B cells display a much higher level of c-myc genomic instability in an AID- and S region-dependent manner. Furthermore, we observe a comparable frequency of AID deamination events between the c-myc intronic sequence and inserted S region in different B cell populations, demonstrating a similar frequency of AID targeting. Thus, our study reveals a clear difference between germinal center and cytokine-activated B cells in their ability to develop genomic instability, attributable to a differential processing of AID-initiated lesions in distinct B cell populations. We propose that locus-specific regulatory mechanisms (e.g., transcription) appear to not only override the effects of S region sequence on AID targeting frequency but also influence the repair manner of AID-initiated lesions.