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Becicka W, Berreby G, Wang J, Moitra J, Panicker S, Tourdot B, Norris P, Kelly K, Zouo Y, Dumont L, Knight J, Kanthi Y. Abstract 461: Antiphospholipid Antibodies In Covid-19 Convalescent Plasma. Arterioscler Thromb Vasc Biol 2022. [DOI: 10.1161/atvb.42.suppl_1.461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Background:
Although convalescent plasma has historically yielded significant benefits in the treatment of infectious diseases, numerous clinical trials have not shown a consistent benefit in treating either moderately or severely ill COVID-19 patients with plasma from convalescent patients. We previously reported increased levels of antiphospholipid antibodies (aPL) in acutely ill COVID patients, with high aPL titers correlating with more neutrophil extracellular traps (NETs) and poorer patient outcomes. We hypothesized that persistence of potentially deleterious autoantibodies in previously hospitalized, convalescent plasma donors may activate immune cells and add context for the lack of clinical efficacy in COVID.
Methods:
116 samples of convalescent plasma from donors previously hospitalized with COVID were obtained from Vitalant. Antibody titers (IgG, IgM, IgA) of anti-2-glycoprotein 1 (a2GP1) and anti-cardiolipin (aCL) and anti-phosphatidylserine/prothrombin (IgG, IgM) were quantified. NET formation by healthy human neutrophils treated with convalescent plasma was evaluated in vitro.
Results:
High aPL titers >40 U/mL) were observed in 10/116 (8.6%) convalescent samples, and 6/10 were positive for either IgG or IgM aCL. The aPL positivity rate exceeded the expected background population rate of ~3%. Six of 116 convalescent samples increased NET-associated MPO activity in purified, primary neutrophils from healthy donors compared with control plasma (mean increase of 23% +/- 11, p<0.01), where only 2 of these were aPL-positive samples.
Conclusion:
aPL were elevated in a larger proportion of surveyed convalescent plasma samples than reported in the healthy population. aPL positivity did not correlate with purified neutrophil activation, suggesting aPL in donor plasma does not have a direct, activating effect on healthy neutrophils. Considering the complex interactions among circulating blood cells, ongoing experiments are examining the impact of convalescent plasma on platelet and endothelial cell function to further elucidate potential autoantibody-mediated vascular perturbations. The results of these studies will be important in informing the vascular implications and safety of convalescent plasma in COVID.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Yu Zouo
- Univ of Michigan, Ann Arbor, MI
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Becicka W, Garrad E, Berreby G, Wang J, Nghiem K, Ramos-Benitez M, Cowling B, Moitra J, Huffstutler R, Carney K, Ferrante E, Cudrici C, Brofferio A, Tourdot B, Jacobson K, Knight J, Kanthi Y, Boehm M. Abstract 123: Genetic Deficiency Of The Ectoenzyme CD73 Increases Neutrophil Extracellular Trap Formation In Patients With ACDC. Arterioscler Thromb Vasc Biol 2022. [DOI: 10.1161/atvb.42.suppl_1.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Background/Purpose:
CD73 is a ecto-5′-nucleotidase located on the plasma membrane that generates adenosine from AMP in the extracellular space, and functions as a checkpoint against immune and vascular activation. CD73 inhibitors that eliminate this immune checkpoint blockade are being studied in phase 2/3 cancer clinical trials. We recently identified that lack of CD73 promotes vascular thromboinflammation and neutrophil extracellular trap (NET) formation in mice. The role of CD73 in human NETosis, however, remains to be studied. Arterial calcification due to deficiency of CD73 (ACDC) is a rare, autosomal recessive condition (~20 patients globally) that results in occlusive peripheral vascular disease. We hypothesized that the congenital absence of CD73 and its function as an immune checkpoint would heighten innate immune activation in patients with ACDC.
Methods:
To test this hypothesis, six patients with molecularly confirmed ACDC were recruited to the NIH for mechanistic studies. Using purified neutrophils from ACDC patients and healthy controls, spontaneous and LPS-induced NET formation was quantified by both Sytox extracellular DNA (eDNA) labeling and NET-associated MPO activity.
Results:
Absence of surface CD73 was confirmed by flow cytometry. Relative to healthy controls, four of six (4/6) patients with ACDC demonstrated increased ex vivo spontaneous NET formation, but not LPS-triggered NETosis. The four ACDC patients with increased spontaneous NETosis had a mean 1.7-fold increase in Sytox-stained eDNA and 2-fold increase in MPO activity compared with contemporary healthy controls.
Conclusion:
These data reveal marked, spontaneous NETosis in patients deficient in the ectoenzyme CD73. Comparison with LPS-stimulated neutrophils demonstrates near maximal NETosis at baseline in patients with ACDC, consistent with a model where CD73 tonically suppresses neutrophil activation to maintain vascular and immune homeostasis. Ongoing studies are exploring the mechanism of spontaneous NETosis, thrombin formation, and fibrinolysis in patients with ACDC. Taken together, these data will have relevance to patients with ACDC, and inform the thromboinflammatory risk of cancer patients receiving CD73 inhibitors.
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