Background: Critically ill patients with coronavirus disease 2019 (COVID-19) have a profound hypercoagulable state and often develop coagulopathy which leads to organ failure and death. Because of a prolonged activated partial-thromboplastin time (aPTT), a relationship with anti-phospholipid antibodies (aPLs) has been proposed, but results are controversial. Functional assays for aPL (i.e., lupus anticoagulant) can be influenced by concomitant anticoagulation and/or high levels of C reactive protein. The presence of anticardiolipin (aCL), anti-beta2-glycoprotein I (anti-b 2 GPI), and anti-phosphatidylserine/ prothrombin (aPS/PT) antibodies was not investigated systematically. Epitope specificity of anti-b 2 GPI antibodies was not reported. Objective: To evaluate the prevalence and the clinical association of aPL in a large cohort of COVID-19 patients, and to characterize the epitope specificity of anti-b 2 GPI antibodies. Methods: ELISA and chemiluminescence assays were used to test 122 sera of patients suffering from severe COVID-19. Of them, 16 displayed major thrombotic events.

COVID-19 is a new pandemic, caused by Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-Cov2) infection and characterized by a broad spectrum of clinical manifestations. Inflammation and the innate immune system have been recently recognized as pivotal players in the most severe forms, characterized by significantly elevated levels of pro-inflammatory cytokines. In this setting, several studies have also reported the presence of abnormalities in coagulation parameters and platelets count, possibly identifying a subgroup of patients with poor prognosis. Some reports of full-blown thromboembolic events are emerging. Among the possible mechanisms underlying coagulation dysfunction, the so-called "cytokine storm" seems to play a pivotal role. Other candidate factors include virus-specific mechanisms, related to the virus interaction with renin angiotensin system (RAS) and the fibrinolytic pathway, but also comorbidities affecting these patients. Coagulation dysfunction is therefore a candidate risk factor for adverse outcomes in COVID-19 and should be carefully addressed in clinical practice.

A homozygous mutation that gave rise to a stop codon in the WIPF1 gene resulted in WASP protein destabilization and in symptoms resembling those of Wiskott-Aldrich syndrome

We investigated the molecular and cellular basis of severe combined immunodeficiency (SCID) in six patients with otofaciocervical syndrome type 2 who failed to attain T cell reconstitution after allogeneic hematopoietic stem cell transplantation, despite successful engraftment in three of them. We identified rare biallelic PAX1 rare variants in all patients. We demonstrated that these mutant PAX1 proteins have an altered conformation and flexibility of the paired box domain and reduced transcriptional activity. We generated patient-derived induced pluripotent stem cells and differentiated them into thymic epithelial progenitor cells and found that they have an altered transcriptional profile, including for genes involved in the development of the thymus and other tissues derived from pharyngeal pouches. These results identify biallelic, loss-of-function PAX1 mutations as the cause of a syndromic form of SCID due to altered thymus development.

Background. Critically ill patients with coronavirus disease 2019 (COVID-19) have a profound hypercoagulable state and often develop coagulopathy which leads to organ failure and death. Because of a prolonged activated partial-thromboplastin time (aPTT), a relationship with anti-phospholipid antibodies (aPL) has been proposed, but results are controversial. Functional assays for aPL (i.e., lupus anticoagulant) can be influenced by concomitant anticoagulation and/or high levels of C reactive protein. The presence of anti-cardiolipin (aCL), anti-beta2-glycoprotein I (anti-β2GPI) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies was not investigated systematically. Epitope specificity of anti-β2GPI antibodies was not reported. Objective. To evaluate the prevalence and the clinical association of aPL in a large cohort of COVID-19 patients, and to characterize the epitope specificity of anti-β2GPI antibodies. Methods. ELISA and chemiluminescence assays were used to test 122 sera of patients suffering from severe COVID-19. Of them, 16 displayed major thrombotic events. Results. Anti-β2GPI IgG/IgA/IgM were the most frequent in 15.6/6.6/9.0% of patients, while aCL IgG/IgM were detected in 5.7/6.6% by ELISA. Comparable values were found by chemiluminescence. aPS/PT IgG/IgM were detectable in 2.5 and 9.8% by ELISA. No association between thrombosis and aPL was found. Reactivity against domain 1 and 4-5 of β2GPI was limited to 3/58 (5.2%) tested sera for each domain and did not correlate with aCL/anti-β2GPI nor with thrombosis. Conclusions. aPL show a low prevalence in COVID-19 patients and are not associated with major thrombotic events. aPL in COVID-19 patients are mainly directed against β2GPI but display an epitope specificity different from antibodies in antiphospholipid syndrome.

Background: Mutations in Janus kinase 3 (JAK3) are a cause of severe combined immunodeficiency, but hypomorphic JAK3 defects can result in a milder clinical phenotype, with residual development and function of autologous T cells. Maternal T-cell engraftment is a common finding in infants with severe combined immunodeficiency but is not typically observed in patients with residual T-cell development. Objective: We sought to study in detail the molecular, cellular, and humoral immune phenotype and function of 3 patients with hypomorphic JAK3 mutations. Methods: We analyzed the distribution and function of T and B lymphocytes in 3 patients and studied the in vitro and in vivo responses of maternal T lymphocytes in 1 patient with maternal T-cell engraftment and residual production of autologous T lymphocytes. Results: B cells were present in normal numbers but with abnormal distribution of marginal zone–like and memory B cells. B-cell differentiation to plasmablasts in vitro in response to CD40 ligand and IL-21 was abolished. In 2 patients the T-cell repertoire was moderately restricted. Surprisingly, 1 patient showed coexistence of maternal and autologous T lymphocytes. By using an mAb recognizing the maternal noninherited HLA-A2 antigen, we found that autologous cells progressively accumulated in vivo but did not compete with maternal cells in vitro. Conclusion: The study of 3 patients with hypomorphic JAK3 mutations suggests that terminal B-cell maturation/ differentiation requires intact JAK3 function, even if partially functioning T lymphocytes are present. Maternal T-cell engraftment can occur in patients with JAK3 mutations despite the presence of autologous T cells.

Ataxia telangiectasia (AT) and Aicardi–Goutières syndrome (AGS) are inherited disorders of immunity with prevalent neurological phenotype. Available treatments are only partially effective, and the prognosis is poor. Induced pluripotent stem cells (iPSCs) are obtained by reprogramming patient somatic cells, preserving the donor individual genetic heritage and creating patient‐specific disease models, useful to investigate pathogenesis and drug effects and to develop precision therapies. The aim is to investigate the cytotoxicity of a panel of immunomodulators using iPSCs of patients with AT or different forms of AGS (AGS1, AGS2, and AGS7). iPSCs were obtained by reprogramming AT and AGS patients’ cells and, as a control, the BJ normal human fibroblast line, using Sendai virus. Cytotoxic effects of two drugs proposed to treat respectively AT and AGS (dexamethasone and mepacrine) were tested by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay after 72 hours' exposure. Data were obtained also for other immunomodulatory drugs (thioguanine, mercaptopurine, thalidomide, and lenalidomide). Relative expression of genes involved in the tested drug pathways was analyzed. AGS7‐derived iPSCs displayed altered viability when treated with a low dose of mepacrine and higher expression of cyclic guanosine monophosphate–adenosine monophosphate synthase, which is the main target for mepacrine action. AGS7‐derived iPSCs were also more sensitive to thioguanine, while AGS2 and AT iPSCs were less sensitive to this medication than the BJ‐iPSC. All iPSCs were equally sensitive to mercaptopurine and resistant to dexamethasone, thalidomide, and lenalidomide. This work establishes an innovative in vitro model that is useful to investigate the mechanisms of drugs potentially effective in AT and AGS.

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