Brain resident memory T cells rapidly expand and initiate neuroinflammatory responses following CNS viral infection.

The contribution of circulating verses tissue resident memory T cells (TRMs) to clinical neuropathology is an enduring question due to a lack of mechanistic insights. The prevailing view is TRMs are protective against pathogens in the brain. However, the extent to which antigen-specific TRMs induce neuropathology upon reactivation is understudied. Using the described phenotype of TRMs, we found that brains of naïve mice harbor populations of CD69+ CD103- T cells. Notably, numbers of CD69+ CD103- TRMs rapidly increase following neurological insults of various origins. This TRM expansion precedes infiltration of virus antigen-specific CD8 T cells and is due to proliferation of T cells within the brain. We next evaluated the capacity of antigen-specific TRMs in the brain to induce significant neuroinflammation post virus clearance, including infiltration of inflammatory myeloid cells, activation of T cells in the brain, microglial activation, and significant blood brain barrier disruption. These neuroinflammatory events were induced by TRMs, as depletion of peripheral T cells or blocking T cell trafficking using FTY720 did not change the neuroinflammatory course. Depletion of all CD8 T cells, however, completely abrogated the neuroinflammatory response. Reactivation of antigen-specific TRMs in the brain also induced profound lymphopenia within the blood compartment. We have therefore determined that antigen-specific TRMs can induce significant neuroinflammation, neuropathology, and peripheral immunosuppression. The use of cognate antigen to reactivate CD8 TRMs enables us to isolate the neuropathologic effects induced by this cell type independently of other branches of immunological memory, differentiating this work from studies employing whole pathogen re-challenge. This study also demonstrates the capacity for CD8 TRMs to contribute to pathology associated with neurodegenerative disorders and long-term complications associated with viral infections. Understanding functions of brain TRMs is crucial in investigating their role in neurodegenerative disorders including MS, CNS cancers, and long-term complications associated with viral infections including COVID-19.

Impact of the April 2020 FDA blood donor eligibility changes on a hospital-based donor center

Background/Case Studies: The COVID-19 pandemic remains a threat to the blood supply due to decreased collections because of lockdowns and physical distancing practices. In April 2020, the U.S. Food and Drug Administration (FDA) changed blood donation eligibility with respect to risks related to blood borne diseases, variant Creutzfeldt-Jakob disease (vCJD) and travel exposures. We examined the impact of these changes on donations at our hospital-based blood center. Study Design/Methods: From implementation of the FDA changes on June 25, 2020 through March 2021, donors were given a voluntary survey to determine whether their eligibility was affected. Specifically, we assessed how many donors would have been previously deferred, but could now donate. Donors could identify which change allowed them to donate: blood borne infection risk, vCJD risk, and/or travel/malaria risk. Donors could also decline to elaborate. The survey was implemented as a quality improvement initiative. We counted how many blood products were collected from these donors and compared deferral rates between July 2019-June 2020 and July 2020-March 2021 by Poisson test (R 4.0.5). Results/Findings: The eligibility changes positively impacted donor acceptance. Overall deferral rate decreased from 293.2 to 224.6 per 1,000 donors between the time periods (see Table). During the survey period, 2569 donors were evaluated;1577 whole blood and 560 platelets were donated. Sixty-nine responses from 55 donors indicated that they became eligible under the new criteria: blood borne infection risk (n=11), vCJD risk (n=26), travel/malaria risk (n=30) and no answer (n = 2). Only one of these donors had a positive infectious disease test (anti-HBc). These donors provided 44 red blood cell units, 40 plasma units and 31 apheresis platelet units. Deferral rates also declined for screening criteria that had not been updated by the FDA. Conclusions: Since June 25, 2020, deferral rates at our blood center have decreased. The FDA eligibility changes had an impact. In total, 55 donors (41 first-time) reported being eligible with the new rules. Their donations helped support our patients during the pandemic. The lower deferral rate overall suggests behavior changes related to the COVID-19 pandemic (lockdowns, business restrictions, and border closures). This may have decreased the number of first-time donors especially, leaving proportionally more returning donors. (Table Presented).

Does a restrictive platelet transfusion strategy affect red blood cell transfusion practice in children?

Background/Case Studies: The coronavirus disease 2019 (COVID-19) pandemic has adversely affected the national blood supply by decreasing blood donations relative to ongoing patient transfusion needs, especially platelet concentrates. Given the decreased availability of platelet units for transfusions, blood banks may be forced on occasion to triage orders by either releasing a decreased quantity of platelets for a single transfusion event or to cancel orders, as appropriate. We investigated whether this restrictive platelet transfusion strategy caused any changes in red blood cell (RBC) transfusion practices. Study Design/Methods: We implemented a starting in early June 2020 and continuing to the present in our pediatric hospital setting. For this study, we compared platelet and red blood cells utilization between September 1, 2019 to June 1, 2020 (PRE) period, and June 1, 2020 to March 1, 2021 (POST) period in relation to the number of times a patient received a blood type and antibody screening test (TS). We also assessed administered 2 to 24 hours following an index platelet transfusion as a surrogate marker for estimating hemostatic efficacy. In addition, average volume of transfused RBCs for each patient during both time intervals were compared. Proportions were compared using z-test and means were compared using t-test (R version 3.6.3). Results/Findings: TS to platelet and TS to RBC transfusion rates were higher in the PRE cohort than the POST cohort (13.79% vs 12.45%, p<0.001 and 23.61% vs 20.61%, p<0.001). In the PRE cohort there were 876 RBC transfusions in the subsequent 24-hour period compared to 698 in the POST cohort. No significant difference was observed in time-to-RBC-transfusions (12.85 h vs 12.35 h, p=0.110). However, the average volume of transfused RBCs that each patient received showed an increase in the POST cohort, compared to the PRE cohort (182 mL vs. 209 mL, p<0.001). Conclusions: For pediatric patients, the restrictive platelet transfusion strategy resulted in lower rates of TS to RBC and TS to platelet transfusion, however, there was an increase in the average volume of RBCs each patient was transfused with. Following a platelet transfusion, there was no statistically significant change in time to RBC transfusions between the two practices. This finding was indicative of the absence of early significant bleeding episodes resulting from a restrictive platelet transfusion strategy.

A Pilot Study to Evaluate the Feasibility of Anti-Fibrinolytic Agents in Reducing Hemorrhagic Complications in Pediatric Patients with Thrombocytopenia

[Formula presented] Background: The risk of bleeding remains high in thrombocytopenic pediatric hematology-oncology patients despite the use of prophylactic platelet transfusions. In one study, WHO grade 2 or higher bleeding occurred in >80% of pediatric subjects receiving hematopoietic stem cell transplantation or chemotherapy despite a platelet transfusion threshold of 10,000/µl. The risk of bleeding is not decreased with higher transfusion thresholds or increased platelet doses. Bleeding episodes are associated with increased mortality rates, greater utilization of resources and increased transfusion requirements. We examined the use of anti-fibrinolytic agents in decreasing bleeding events and platelet transfusions. Methods: We conducted a randomized double-blinded Phase 2 trial of tranexamic acid versus placebo in inpatient pediatric patients undergoing chemotherapy or HSCT expected to have prolonged thrombocytopenia. All patients admitted to the Oncology or HSCT services were screened for eligibility. Patients consenting for enrollment received either tranexamic acid 10m/kg/dose or normal saline every 8 hours while the platelet count as <30,000/ul until discharge or spontaneous platelet recovery (maximum 30 days). We conducted daily hemostatic assessments using the WHO bleeding scale and monitored adverse events and platelet transfusion requirements. Follow-up assessments took place at 7 and 30 days following completion of study medication. Primary aims were to assess safety and feasibility of tranexamic acid in children with hypoproliferative thrombocytopenia. Results: We screened 697 admissions over 11 months, 31 patients were eligible for enrollment. Enrollment was suspended in March 2020 for COVID reasons though screening continued through July 2020. An additional 10 eligible patients were identified in this period. The most common reasons for ineligibility included recent asparaginase administration, predicted inpatient stay <5 days and age ≤ 2 or ≥ 18 years. Eleven patients enrolled and completed all study procedures. There were no missed doses of medication, 88.4% of doses were administered within one hour of prescribed time. Patients remained on study for a mean of 11.1 days. Five patients each met criteria for spontaneous platelet count recovery or discharge, 1 patient received the study medication for 30 days. Bleeding (all grades) occurred on 29.5% of days. Grade 2 or higher bleeding occurred on 4.9% of days and was experienced by 27.3% of patients. The most common sites of bleeding were oral/nasal and cutaneous. Subjects received a median of 2 platelet transfusions per patient. There were no thromboembolic events or serious adverse events. Conclusion: Tranexamic acid is well tolerated can be safely administered to pediatric oncology patients as an adjunct to therapy. We are planning a multi-center randomized controlled trial to assess the efficacy of tranexamic acid in reducing bleeding complications in this population. Disclosures: Triulzi: Fresenius Kabi: Consultancy;Cerus Corp: Research Funding. OffLabel Disclosure: Tranexamic Acid - This medication is being studied as an adjuvant to therapy to prevent bleeding complications and reduce platelet transfusions in pediatric patients with hypoproliferative thrombocytopenia.

Severe COVID-19 in children and young adults in the Washington DC metropolitan region

Background: Children and young adults were initially reported as largely spared from severe complications of SARS-CoV-2 infection, but the impact to this population has been significant. Methods: This observational retrospective cohort study includes 420 symptomatic children and young adults with lab confirmed SARS-CoV-2 infection treated between March 15 and June 16, 2020 at Children's National Hospital in Washington DC. We identified and compared cohorts of non-hospitalized (N=324) and hospitalized (N=96) patients, including non-critically ill (N=64) and critically ill hospitalized (N=32) patients. Clinical and demographic data were extracted from medical records Results: Of 420 SARS-CoV-2-infected symptomatic patients, 23% required hospitalization, of which 67% were non-critically ill and 33% were critically ill. All age groups were represented in the symptomatic cohort, with a median age of 8.6 years. Patients > 15 years of age represented 44% of critical care admissions. Males and females were equally represented in all cohorts. Underlying medical conditions were present in 36%, but more common in hospitalized (59 %) and critically ill (66 %) patients. The most frequent underlying diagnosis overall was asthma (16 %), but also included neurologic (6 %), diabetes (3 %), obesity (3 %), cardiac (3 %), hematologic (3 %) and oncologic (1 %) conditions. The majority (66 %) of SARSCoV- 2 infected patients presented with respiratory symptoms with or without fever. Other symptoms were also present, including diarrhea/vomiting (21 %), myalgia (11 %), chest pain (8 %) and loss of sense of smell or taste (7%). Hospitalized patients required varying levels of respiratory support, including mechanical ventilation, BiPAP, RAM cannula and HFNC. Additional presentations included diabetic hyperglycemia, sickle cell vaso-occlusive crisis, vascular complications, and multisystem inflammation. Treatment included remdesivir, convalescent plasma, tocilizumab and other therapies. Conclusion: Although children/young adults have been less affected than elderly adults, the impact of SARS-CoV2 on this population has been significant in Washington DC and informs other regions anticipating their surge.

SARS CoV-2-associated multisystem inflammatory syndrome of children (MIS-C) in the Washington DC metropolitan region

Background: Background: Multi-system Inflammatory Syndrome of Children (MIS-C) has recently emerged internationally as a serious inflammatory complication of SARS-CoV-2 infection with significant morbidity for the pediatric population. Methods: This observational retrospective cohort study includes 33 children meeting CDC criteria for MIS-C treated between March 15 and June 17, 2020 at Children's National Hospital in Washington DC. Clinical and demographic data were extracted from medical records and are summarized. Results: Of 33 hospitalized MIS-C patients, 42% were critically ill, and 58% were non-critically ill. The median age was 8.9 years (0.7-18.7 years). More males (58 %) than females (43 %) were represented in the MIS-C cohort. The majority (75%) of children had no underlying medical condition. Criteria for incomplete or complete Kawasaki Disease (KD) were present in 39% of patients, while an additional 9% had some features of KD. However the remaining 52% of MIS-C patients presented with other sub-phenotypes including prominent severe abdominal pain and/or nonspecific multiorgan dysfunction. 30% presented with shock requiring volume and/or inotropic support. SARS-CoV-2 antibodies were present in 61% of patients. Virus was detectable by PCR in 36% of patients. At the time of initial evaluation, 39% (13/33) of children had identified cardiac abnormalities including myocardial dysfunction (5/33;15%), coronary ectasia (4/33;12%), coronary aneurysm (3/33;9%), or pericardial effusion 5/33;15%) either alone or in combination. Cytokine profiling identified elevation of several cytokines in this cohort, including IL-6. Treatment has included intravenous immunoglobulin, aspirin, anakinra and other immunomodulatory therapies, with overall rapid response to therapy. No deaths have occurred. Conclusion: The emergence of MIS-C late in the surge of SARS-CoV-2 circulation in the Washington DC metropolitan region has added to the already significant burden of hospitalized and critically ill children in our region. A significant percentage of these children present with cardiac dysfunction and abnormalities, whether or not with KD features at presentation. Detailed characterization of immune responses and long term outcome of these patients is a priority.