ABSTRACT
Background: TLR7/8 are immune receptors expressed in megakaryocytes which detects single-stranded RNA viruses such as SARS-CoV- 2. There is increasing evidence that in addition to raised platelet counts, severe infection with SARS-CoV- 2 increases the risk of venous, arterial and microvascular coagulation. Aim(s): To determine if ssRNA viruses are capable of increasing thrombopoeisis through direct interaction with megakaryocytes. Method(s): Cells were incubated with and without Gardiquimod (GDQ), a specific agonist of TLR7/8 in cord blood derived (CBMKs) and mouse bone marrow derived megakaryocytes (mMKs). TLR7/8-/- iPSC derived megakaryocytes (iPSC-MKs) were produced using CRISPR Cas9 editing of iPSCs and forward programming using an doxycyclin inducible cassette. GFP labelled SARS-CoV- 2 virus was incubated with the TLR7/8-/- iPSC- MKs and wild-type iPSC-MKs. Result(s): Incubation with GDQ increased platelet production in CBMKs and mMKs, and increased platelet function. Increased platelet counts were seen in mice treated with GDQ, and mice infected with influenza. Incubation with GDQ induced increased expression of IL1beta in the parental iPSC-MKs, however in the TLR7-/- and TLR7/8-/- MKs, no increased expression was observed. There was a significant increase in platelet production from the parental iPSC-MKs in response to incubation with GDQ, which was not seen in the TLR7-/- and TLR7/8-/- MKs. Incubation of the GFP-labelled SARS-CoV- 2 virus with wild-type MKs did not lead to a significant increase in fluorescence. Only very low level viral sequences were found in the cells post-incubation demonstrating that penetration within the MKs is unlikely to be of significance. Studies are ongoing to ascertain whether SARS-CoV- 2 induces outside in signalling leading to changes in transcription within the MKs (such as elevation of IL1beta). Conclusion(s): TLR7/8 agonists, including ssRNA genome viruses, increase platelet production and functionality from megakaryocytes. SARS-CoV- 2 does not appear to penetrate and significantly replicate within MKs, however incubation with megakaryocytes did show elevated expression of IL1beta. (Figure Presented).
ABSTRACT
Introduction: Efforts to control the COVID-19 pandemic brought sweeping social change, with stay-at-home orders and physical distancing mandates in 43 of 50 states by April 2020. Early on, isolated studies around the world described reduced hospital admissions. Reports from some US hospitals also described declines in catheterization laboratory activations, and acute myocardial infarction (AMI) and stroke admissions. However, there have been few population-based analyses of emergency department (ED) visits to verify these initial reports and describe longer term impacts of the pandemic on care seeking behavior. Hypothesis: We hypothesized that AMI and stroke ED visits in North Carolina (NC) would decrease substantially after a statewide stay-at-home order was announced on March 27, 2020. Methods: We analyzed all ED visits from January 5 to August 28, 2020 using data collected by the NC Disease Event Tracking and Epidemiologic Collection Tool, a syndromic surveillance system that automatically gathers ED data in near-real time for all EDs in NC. Counts of AMI and stroke/transient ischemic attack (TIA) were ascertained using ICD-10-CM diagnosis codes. We compared weekly 2020 ED visit data before and after NC's stay-at-home order, and to 2019 ED visit data. Results: Overall ED volume declined by 44% in the weeks before and after the stay-at-home order(Figure) while the prior year's ED volume stayed steady at ∼100,000 visits per week. From January5 to March 28, there were 593 AMI and 791 stroke/TIA visits per week on average. By April 11, EDvisits reached a nadir at 426 AMI and 543 stroke/TIA visits per week, representing a 28% and 31%decrease, respectively. Since June, AMI and stroke/TIA ED visits have rebounded slightly but haveyet to reach pre-pandemic levels. Conclusions: We observed swift declines in AMI and stroke/TIA ED visits following NC's stay-at-home order. These findings potentially reflect the avoidance of medical care due to fears of COVID-19 exposure and may eventually result in higher associated case fatality.