ABSTRACT
Background The ChAdOx1 nCoV-19 vaccine has been shown to induce Vaccine-induced Immune Thrombotic Thrombocytopenia (VITT), a syndrome that shares clinical features with heparin-induced thrombocytopenia (HIT). The mechanism of thrombocytopenia and thrombosis in these disorders appears to be related to the development of pathologic anti-PF4/heparin antibodies, some of which could activate complement. Interestingly, we and others have found that complement activation is vital when both pediatric and adult patients have severe respiratory illness from SARS-CoV-2 virus (COVID-19) or in the post-infectious multisystem inflammatory syndrome in children (MIS-C). We hypothesized that patients with severe COVID-19 or MIS-C develop similar anti-PF4/heparin antibodies, which lead to endothelial complement activation that drive the inflammatory responses seen in these diseases. Methods Our cohort included 30 pediatric patients with positive SARS-CoV-2 RT-PCRs: 10 each of severe COVID-19 (“Severe”, MIS-C, and mild/asymptomatic (“Mild”) infection. Using ELISA, we evaluated the levels of antibodies to various platelet-related proteins including PF4, PF4-heparin, and NAP2;in addition, we examined the ability of plasma from each patient to activate complement. The antibody levels were compared to control samples including samples from adult patients with VITT and HIT. Statistical analyses with ANOVA were performed to evaluate differences. Results Patients with MIS-C have a significantly higher anti-PF4 antibody concentration (as measured by mean optical density [OD]) than patients with either mild/asymptomatic disease, or severe COVID-19: Severe 0.5 +/- 0.14;Mild 0.3 +/- 0.12;MIS-C 0.77 +/- 0.35, p=0.003 MIS-C vs. Mild);Similar results were seen for anti-PF4/heparin antibodies: Severe 0.4 +/- 0.14;Mild 0.35 +/- 0.12;MIS-C 0.64 +/- 0.3, p=0.003 MIS-C vs. Mild;p=0.034 MIS-C vs. Severe). These were similar to values obtained for the HIT sample (Figure). Conclusion Patients with MIS-C and severe COVID19 have significant detectable anti-PF4 and PF4/heparin antibodies in contrast to those patients with mild/asymptomatic disease. Our previous studies have shown that patients with MIS-C and COVID-19 have evidence of endovascular complement activation in the form of elevated soluble membrane attack complex (sC5-b9). We have also previously demonstrated that VITT anti-PF4 and anti-PF4/heparin antibodies activate complement and result in endothelial cell activation. These antibodies in pediatric SARS-CoV-2 infection may be involved in the development of more severe disease manifestations. Ongoing investigations will identify if this is due to endothelial complement activation and inflammatory responses that accompany severe disease. This is the first demonstration of the role of anti-PF4 and PF4/heparin antibodies in pediatric SARS-CoV-2. [Formula presented] Disclosures: Bassiri: Guidepoint Global: Consultancy;Kriya Therapeutics: Consultancy, Current holder of individual stocks in a privately-held company. Teachey: Janssen: Consultancy;NeoImmune Tech: Research Funding;Sobi: Consultancy;BEAM Therapeutics: Consultancy, Research Funding. Lambert: ClinGen, ISTH, ASH, GW University: Honoraria;Rigel: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding;Bayer: Consultancy;Dova: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding;Shionogi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees;Argenx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding;Principia: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding;Astra Zeneca: Research Funding;Novartis: Consultancy, Honoraria, Research Funding;Sysmex: Research Funding;PDSA: Research Funding;Octapharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Fundi g.
ABSTRACT
Purpose: Pediatric SARS-CoV-2 infections result in at least three distinct disease manifestations. Most children infected acutely remain asymptomatic or develop only mild symptoms of COVID-19;however, small proportion of acutely infected children, develop progressive respiratory illness, multi-organ involvement, and an associated hyperinflammatory syndrome. These COVID-19 presentations are contrasted by MIS-C, a post-infectious hyperinflammatory condition characterized by fever, shock, and multi-organ dysfunction. We sought to characterize the hyperinflammatory syndromes of SARS-CoV-2 infections, in order to identify biomarkers that may distinguish the hyperinflammation seen in these conditions from that of HLH. Methods:We enrolled children admitted to the Children's Hospital of Philadelphia who had positive SARS-CoV-2 RT-PCR tests or met clinical criteria for MIS-C.We measured plasma levels of 10 cytokines on a MesoScale Discovery platform and correlated these values with available clinical parameters of inflammation. Results: Fifty patients were classified into asymptomatic/mild COVID- 19 (amC19;N = 18), severe COVID-19 (sevC19;N = 11), or MISC (MIS-C;N = 21). Five cytokines (IL-1beta, IL-2, IL-4, IL-12p70 and IL-13) were excluded from further analyses, as their levels were not abnormal. Of the remaining (IL-6, IL-8, IL-10, TNF-alpha and IFNgamma) thatwere often elevated, we found statistically significant elevations in IL-10 in both sevC19 andMIS-C, when compared to amC19 patients. Some patients in each cohort had markedly elevated IFNgamma, but the cohort means were not statistically different. While the maximal C-reactive protein levels were elevated in both sevC19 and MIS-C, these were not statistically different,while maximal ferritin levels differentiated sevC19 from amC19 andMIS-C. Conclusion: While the pathogenesis of pediatric COVID-19 andMIS-C are not fully elucidated, differences between observed biomarkers suggest that the immune pathogenesis of the hyperinflammation in these syndromes is likely to be mechanistically different, although overlap may exist with HLH in some patients.