IRF2BP2 mutation with autoimmune enteropathy, immune deficiency, and respiratory failure

Case history: We present the case of a 31-year-old Hispanic male with history of recurrent bronchiectasis, invasive aspergillosis, and severe persistent asthma, who is now status post lung transplant for end-stage lung disease. He initially presented at 7 years of age with diarrhea, failure to thrive, and nearly absent immunoglobulin levels (IgG < 33 mg/dL, IgA < 7 mg/dL, IgM = 11 mg/dL, IgE = 4 IU/dL) necessitating IVIG treatment. Small intestinal biopsy showed villous atrophy consistent with autoimmune enteropathy. Sweat chloride was reported as indeterminate (44 me/dL). Initial WBC, platelet, and T- and NK-cell counts were within normal range, and B-cell count and percentage were borderline low. Most recently, he was found to have increased immature B-cell count (CD21low), decreased memory B-cells, and poor pneumococcal vaccine antibody response. Patient has been hospitalized numerous times with increasingly severe bronchiectasis, pneumonitis, and COVID-19 infections twice despite vaccination, leading to respiratory failure and lung transplantation. Family history is negative for immune deficiency and lung diseases. Discussion(s): Of these 3 VUSs (see the table), the one in IRF2BP2 has the most pathogenic potential due to its autosomal dominant inheritance, its location in a conserved domain (Ring), and previous case reports of pathogenic variants at the same or adjacent alleles 1-3. Baxter et al reported a de novo truncating mutation in IRF2BP2 at codon 536 (c.1606CinsTTT), which is similar to our patient's mutation. This patient was noted to have an IPEX-like presentation, with chronic diarrhea, hypogammaglobulinemia, and recurrent infections. Variant Functional Prediction Score for our variant predicts a potentially high damage effect. There are 2 other case reports of heterozygous mutations in loci adjacent to this allele;one (c.1652G>A)2 with a similar clinical phenotype to our patient and the other (C.625-665 del)3 with primarily inflammatory features and few infections. Impact: This case highlights a variant in IRF2BP2 associated with severe hypogammaglobulinemia, recurrent pulmonary infections, and autoimmune enteropathy. [Table presented]Copyright © 2023 Elsevier Inc.

COVID-19-Related Encephalitis in a Child with PIK3CD Defect

Introduction: COVID-19 related encephalitis has been reported in pediatric patients;however, there are no reports in patients with inborn errors of immunity (IEI). Activated PI3K Delta Syndrome (APDS) is a disease of immune dysregulation with immunodeficiency, autoimmunity, and abnormal lymphoproliferation resulting from autosomal dominant gain-offunction variants in PIK3CD or PIK3R1 genes. We investigate a family with APDS, one mother and three children, one of whom developed COVID-19 related encephalitis. Method(s): Patients were consented to an IRB-approved protocol at our institution. Medical records and detailed immunophenotyping were reviewed. Family members were sequenced for IEI with a targeted gene panel. Result(s): The index case is a 10-year-old female with a known pathogenic variant in PIK3CD (c.3061 G > A, p.Glu1021Lys), who contracted SARS-COV-2 despite one COVID-19 vaccination in the series. Her disease course included COVID-related encephalitis with cerebellitis and compression of the pons, resulting in lasting truncal ataxia and cerebellar mutism. At that time, the patient was not on immunoglobulin replacement therapy (IgRT), but was receiving Sirolimus. Besides the index case, 3 family members (2 brothers, 1 mother) also share the same PIK3CD variant with variable clinical and immunological phenotypes. All children exhibited high transitional B-cells, consistent with developmental block to follicular B cell stage. Increased non-class switched IgM+ memory B cells and skewing towards CD21lo B cell subset, which is considered autoreactive-like, was observed in all patients. Of note, the patient had low plasmablasts, but normal immunoglobulins. Of her family members, only one was receiving both sirolimus and IgRT. Conclusion(s): We describe a rare case of COVID-19-related encephalitis in a patient with inborn error of immunity while not on IgRT. This may indicate infection susceptibility because of a lack of sufficient immunity to SARS-CoV-2, unlike the rest of her family with the same PIK3CD variant.Copyright © 2023 Elsevier Inc.

Managing severe warm autoimmune haemolytic anaemia after the SARS-Cov- 2 vaccine with emergency splenectomy and eculizumab

Autoimmune haemolytic anaemia (AIHA) is rare but described after the SARS-CoV- 2 Pfizer-BioNTech vaccine. We present a case of severe refractory warm AIHA after this vaccine, managed with emergency splenectomy and complement inhibition with eculizumab. A male in his teens with a history of liver transplant for biliary atresia (aged 2 years) and AIHA (aged 6 years) presented to his district general hospital with jaundice, dark urine, fatigue and chest discomfort 48 h after the first dose of SARS-CoV- 2 Pfizer-BioNTech vaccine (BNT162b2 mRNA). Investigations revealed haemoglobin (Hb) of 70 g/L and bilirubin of 98 mumol/L, which was treated as AIHA. The patient initially responded to prednisolone (1 mg/kg, 60 mg) but subsequently deteriorated and failed to respond to second-line rituximab (375 mg/m2) and two units of packed red blood cells (PRBC). By day 29 the patient had developed life-threatening anaemia culminating in a Hb of 35 g/L (after transfusion), lactate dehydrogenase (LD) of 1293 units/L and bilirubin of 228 mumol/L. This necessitated an immediate transfer to our tertiary centre for specialist support. Further investigations revealed a haptoglobin <0.1 g/L and direct antiglobulin test (DAT) strongly positive for IgG (4+) and negative for C3d. The peripheral blood film showed severe anaemia, nucleated red cells, anisocytosis and spherocytes with no autoagglutination, schistocytes or platelet clumps. Thrombocytopaenia (platelets 49 +/- 109/L) was present. Differentials were ruled out, such as paroxysmal nocturnal haemoglobinuria and heparin-induced thrombocytopaenia. HIV and hepatitis serology were negative, as were adenovirus, cytomegalovirus and Epstein-Barr virus PCR assays. A CT showed splenomegaly of 15.5 cm. Urinalysis found urobilinogen and bilirubin at high concentrations and negative urinary haemosiderin. Together, the investigations were consistent with warm AIHA. On day 29, four units of PRBC were transfused alongside 100 mg methylprednisolone and 1 g/kg IVIG. On day 30 the patient deteriorated despite the escalated treatment: Hb had only increased to 54 g/L, bilirubin was 200 mumol/L and LD was rising. Considering this life-threatening fulminant haemolysis, an emergency splenectomy was performed. This slowed haemolysis but did not completely ameliorate it: by day 33 the patient had received 15 units of PRBC. Thus, eculizumab, a terminal complement pathway inhibitor, was trialled to arrest intravascular haemolysis, alongside rituximab, repeat IVIG 1 g/kg, prednisolone 40 mg and tacrolimus 2 mg. This showed a favourable response, requiring less frequent transfusions and settling haemolysis. This case highlights the rare complication of warm AIHA with the SARS-CoV- 2 Pfizer-BioNTech vaccine, the use of emergency splenectomy for disease control, and the potential of eculizumab for refractory cases.

Pbmc Immunophenotyping and Plasma Inflammatory Profile of Children with Long Covid

Background: Long COVID can be developed by individuals after an infection with SARS-CoV-2 as described by the WHO. Although this condition is more commonly described in adults, it can occur in children and adolescents with a wide range of estimated prevalence of 1-25%. Little is known about the role of the immune system in long COVID. However, one of the main hypotheses about the underlying mechanism in long COVID is that there is an immune and inflammatory dysregulation that persists after the acute infection. The objective of this study is to compare immune cells populations, and inflammatory biomarkers in paediatric populations with and without long COVID. Method(s): We analyzed 55 blood samples from the pediaCOVID cohort (Hospital Germans Trias i Pujol), which includes more than 130 children diagnosed with long COVID and 23 controls. We measured different immune cell populations using spectral cytometry with a panel of 37 cellular markers, and 42 inflammatory markers using Luminex or ELISA. EdgeR was used for statistical analysis of the spectral data;p-values of inflammatory markers were calculated using the likelihood ratio test and they were corrected for multiple comparisons. Result(s): The study cohort had a median age of 14.3 (IQR, 12.5-15.2) and 69.1% female. Patients had at least 3 symptoms associated with long COVID (median [IQR];10 [7-16]). The most common symptom was asthenia/fatigue (98.2%). Compared to the control cohort, children with long COVID had increased numbers of CD4+CD8+ T cells, IgA+CD21+CD27+ memory B cells, and IgA+CD21-CD27- memory B cells, while CD4+ TEMRA cells (CD45RA+, CCR7-), intermediate monocytes (CD14+, CD16+) and classical monocytes (CD14+, CD16-) were decreased (all p< 0.05;q=n.s.). None of the 42 inflammatory biomarkers showed significant differences between children with and without long COVID. Conclusion(s): The results of this study suggest that specific populations of peripheral blood immune cells might be involved in the mechanisms underlying prolonged COVID in children and adolescents. The increase in both IgA+CD21-CD27- and IgA+CD21+CD27+ memory B cells could be associated with the persistence of viral antigen in the gut and/or gut dysbiosis. Moreover, the decrease in CD4+ TEMRA cells could be related to autoantibodies against G-protein coupled receptors (GPCRs), since this cell population can express GPR56, and autoantibodies against GPCRs were previously reported to be elevated in adults with long COVID.

CD27-IgD- B cells might portray an exhausted B cell phenotype resulting in lack of response to checkpoint inhibitor treatment in NSCLC

Background Checkpoint inhibitor (CI) therapy has revolutionized the therapy landscape of NSCLC. However, why some patients do not respond to CI therapy remains unknown. The correlation between intra-tumoral B cell follicles and response to CI therapy has been established. B cell follicles within the lymph node become more dispersed with age and CD27-IgD- B cells (DNBc) are described to be age-associated. Moreover, DNBc are abundant in chronic infection, elderly, long COVID and auto-immunity and are described to be anergic and exhausted and often lack expression of CD21. DNBc are expanded in NSCLC tumors compared to healthy lung tissue and inversely correlate to switched memory B cells in the tumor. In this study we explored if there is a correlation between this B cell subtype in peripheral blood of NSCLC patients and response to CI therapy. Methods Patients treated with CIs within the Erasmus Medical Center were included in a prospective observational immunomonitoring study. Nineteen NSCLC patients treated with either Pembrolizumab (Pem) or Nivolumab and 5 healthy controls (HC) were selected. Pem was given in 6/11 responding patients (R) and 5/8 non-responding patients (NR). Peripheral blood mononuclear cells (PBMC) were collected before start of treatment and characterized by multicolor flow cytometry. Results HC and R showed a similar pattern in most B cell subsets. NR had significantly lower proportion of B cells within the PBMC fraction than Rand HC (R: 7.14%, NR: 2.91%, HC: 10.60%). In addition, NR had a significantly higher frequency of DNBc than R and HC (R: 9.43%, NR: 23.78%, HC: 7.19%) and there was no correlation between age and DNBc. The frequency of DNBc correlated positively with lack of CD21 expression (r2: 0.83) and expression of Ki67 (r2: 0.54) both in NR, Rand HC. The frequency of Ki67+CD21-DNBc within the B cell fraction was higher in NR than in R and HC (NR: 18.34%, R: 3.51%, HC: 0.67%). Conclusions We are the first to describe that frequencies of DNBc are higher in NR compared to R and HC. Specifically, Ki67+CD21-DNBc are increased in NR and might reflect an anergic, exhausted B cell phenotype. The absence of a correlation between age and DNBc could suggest that the increase in DNBc is induced by the tumor. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure D. Dumoulin: Financial Interests, Personal, Other: Roche, BMS, MSD, AstraZeneca, Novartis. J.G. Aerts: Financial Interests, Personal, Research Grant: Amphera, Roche, Eli Lilly;Financial Interests, Personal, Advisory Board: Amphera, Bristol-Myers Squibb, Eli Lilly, MSD, Roche;Financial Interests, Personal, Ownership Interest: Amphera;Financial Interests, Personal, Other: Takeda. All other authors have declared no conflicts of interest.Copyright © 2023 International Association for the Study of Lung Cancer. Published by Elsevier Inc.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19.

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2-4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells - basophiles and eosinophils - were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory" Tfh1 cell and increased "pro-inflammatory" Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naive" and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24- plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.Copyright © 2022 Saint Petersburg Pasteur Institute. All rights reserved.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2–4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells — basophiles and eosinophils — were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory” Tfh1 cell and increased "pro-inflammatory” Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naïve” and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24– plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.

MANAGEMENT OF AUTOIMMUNE HAEMOLYTIC ANAEMIA DURING PREGNANCY OR POST-PARTUM: AN INTERNATIONAL MULTI-CENTRE EXPERIENCE

Background: Autoimmune haemolytic anaemia (AIHA) during pregnancy is a rare finding, and few is known about maternal and foetal outcomes. AIHA may either develop or relapse during gestation and postpartum or be an issue in a patient on active therapy who becomes pregnant. AIHA management during pregnancy and lactation is not standardized and drug use is often limited by safety concerns. Aims: We studied AIHA impact on pregnancy focusing on disease severity, treatment need and maternal/foetal outcome. Methods: Through a multicentric retrospective cohort study, we identified 38 pregnancies occurred in 28 women from 1997 to 2021 in 10 European centres in Italy, Denmark, France, the Netherlands, USA, and Spain. All included patients had a previous AIHA history or developed/exacerbated AIHA during gestation or postpartum. AIHA was classified according to the direct antiglobulin test. Results: We registered 18 warm AIHA (10 IgG;8 IgG+C3d), 2 cold agglutinin disease, 3 mixed and 5 atypical forms (Table 1). Evans syndrome (i.e., association of AIHA and immune thrombocytopenia or neutropenia) was present in 4. Mean age at AIHA diagnosis was 27 (3-39) and at pregnancy 32 (21-41) years. AIHA diagnosis predated pregnancy in 15 women and had required at least 1 therapy line in all of them, and >2 lines in 12 (rituximab, N=7;cytotoxic immunosuppressants, N=6;splenectomy, N=5). Among these 15 patients, 6 had a relapse during pregnancy, 3 during postpartum and 9 were on active treatment at the time of pregnancy (steroids, N=8;cyclosporine, N=1;azathioprine, N=1;the latter stopped after positive pregnancy test). A patient with a previous AIHA, relapsed as immune thrombocytopenic purpura during pregnancy. Further 8 patients had an AIHA onset during gestation and 2 postpartum. A patient had AIHA onset during the postpartum of the 1st pregnancy and relapsed during the 2nd one. In the 20 women experiencing AIHA during pregnancy/postpartum, median Hb and LDH levels were 6,4 g/dL (3,1 - 8,7) and 588 UI/L (269-1631), respectively. Management consisted in blood transfusions (N=10) and prompt establishment of steroid therapy+/-IVIG (N=20), all with response (complete N=13, partial N=7). After delivery, rituximab was necessary in 4 patients and cyclosporine was added in one. Anti-thrombotic prophylaxis was given in 7 patients. Overall, we registered 10 obstetric complications (10/38, 26%), including 4 early miscarriages, a premature rupture of membranes, a placental detachment, 2 preeclampsia, a postpartum infection and a biliary colic. Apart from the case of biliary colic and one of the two cases of preeclampsia, 8/10 complications occurred during active haemolysis and treatment for AIHA. Nine foetal adverse events (9/38, 24%) were reported: a transitory respiratory distress of the new-born in a mother with active AIHA, 3 cases of foetal growth restriction, a preterm birth, an infant reporting neurologic sequelae, a case of AIHA of the new-born requiring intravenous immunoglobulins, blood transfusions and plasma exchange, and 2 perinatal deaths. The latter both occurred in women on active AIHA therapy and were secondary to a massive placental detachment and a symptomatic SARS-CoV-2 infection. (Figure Presented ) Summary/Conclusion: AIHA developing/reactivating during pregnancy or postpartum is rare (about 5%) but mainly severe requiring steroid therapy and transfusions. Importantly, severe maternal and foetal complications may occur in up to 26% of cases mostly associated with active disease, pinpointing the importance of maintaining a high level of awareness. Passive maternal autoantibodies transfer to the foetus seems a rare event.

IMMUNOMODULATORY EFFECTS of SARS-COV-2 VACCINATION: INCREASE of REGULATORY T CELLS after MRNA VACCINE

Background: Besides the ability to induce antigen-specifc responses, vaccines can be endowed with immunomodulatory properties including the capacity to induce or downregulate regulatory T cells (Treg) that suppress adaptative and autoreactive immune responses (1). Objectives: We asked if an anti-SARS-CoV-2 mRNA vaccine could also induce an accumulation of Treg cells in patients with mixed cryoglobulinemia vasculitis (MCV), who have a defciency of Treg cells (2) and in healthy individuals. We also investigated immunologic variables possibly associated with a low immunogenic-ity of SARS-CoV-2 mRNA vaccine in patients with MCV (3). Methods: We analyzed peripheral blood lymphocyte subpopulations and anti-SARS-CoV-2 serological response in 24 patients with MCV and 9 Healthy donors (HD) before and after 2 weeks after the second dose of the Pfzer/BioNTech vaccine. Results: Among MCV patients we found 15 serological responders and 9 non-responders. All 5 seronegative patients treated recently with rituximab had <5 B cells/μ L, whereas the absolute B cell count was increased in 2 of 4 untreated patients due to monoclonal B cell lymphocytosis, with monoclonal cells representing more than 90% of B cells, associated with non-Hodgkin lymphoma. The percentage of pathologic CD21low B cells was signifcantly increased in seronegative patients. Before receiving the Pfzer/BioNTech vaccine, patients with MCV had a signifcantly reduced frequency of Treg cells among CD4+ T cells compared to HD. After the second dose of the vaccine, there was in MCV patients a signifcant increase in the percent and absolute count of Treg among CD4+ T cells Concerning the pre-vaccination distribution of T cells subpopulations, including the percentages and absolute counts of total CD3+, CD4+, CD8+, HLA-DR+ activated, Treg or CD56+ natural killer T cells, we could not reveal any pattern signifcantly associated with lack of serological response to vaccine. Conclusion: Our fndings show that lack of immunoreactivity in patients with MCV may be associated with expansion of pathologic B cells and that anti-SARS-CoV2 mRNA vaccine may induce an increase of Treg cells.

B CELL CHARACTERISTICS at BASELINE PREDICT HUMORAL RESPONSE UPON SARS-COV-2 VACCINATION among PATIENTS TREATED with RITUXIMAB

Background: Vaccination is considered efficient in controlling infections incl. SARS-CoV-2. Prior studies showed that patients receiving rituximab (RTX) with low B cell counts are at increased infectious risk (1) and risk of inadequate vaccination responses (2, 3). Thus, the ability to further defne and predict vaccination responses in these patients may guide their optimal protection. Objectives: To assess predictive biomarkers of vaccination responses upon SARS-CoV-2 vaccination in RTX treated patients. Methods: B cell characteristics before vaccination were evaluated to predict responses in 15 patients with autoimmune infammatory rheumatic diseases receiving RTX. 11 patients with rheumatoid arthritis on other therapies (RA), 11 kidney transplant recipients (KTR) and 15 healthy volunteers (HC) served as controls. A multidimensional analysis of B cell subsets and a correlation matrix were performed to identify predictive biomarkers. Results: Signifcant differences regarding absolute B cell counts and specifc subset distribution pattern between the groups were validated at baseline. Here, the majority of B cells from vaccination responders of the RTX group (RTX IgG+) comprised naïve and transitional B cells, whereas vaccination non-responders (RTX IgG-) carried preferentially plasmablasts and double negative (CD27-IgD-) B cells (Figure 1). Moreover, there was a positive correlation between neutralizing antibodies and absolute B cell numbers with B cells expressing HLA-DR and CXCR5 (involved in antigen presentation and germinal center formation) as well as an inverse correlation with CD95 expression and CD21low expression (marker for activation and exhaustion) on B cells. Conclusion: Substantial repopulation of naïve B cells upon RTX therapy appears to be essential for an adequate vaccination response requiring germinal center formation. In contrast, expression of exhaustion markers (CD21low, CXCR5-, CD95+) indicate negative predictors of vaccination responses. These results may guide optimized vaccination strategies in RTX treated patients clearly requiring antigen-inexperienced B cells for appropriate protection.

T HELPER CELL SUBSETS AND RELATED TARGET CELLS IN ACUTE COVID-19

Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2–4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells — basophiles and eosinophils — were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased “regulatory” Tfh1 cell and increased “pro-inflammatory” Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of “naïve” and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24– plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.

Positive direct antiglobulin tests in cancer patients hospitalized with COVID-19

Background: A positive direct antiglobulin test (DAT) is frequently observed for patients suffering from COVID-19 but its interpretation in transfusion dependent patients such as patients with solid and haematological malignancies is complex and multi-factorial. Aims: • To identify the incidence of DAT positivity in cancer patients hospitalized with COVID-19. • To explore the significance of DAT positivity in those patients by comparing with the DAT-negative COVID-19 patients (control group). Methods: This was a cross-sectional study done in India where samples were obtained from 88 cancer patients with confirmed COVID- 19. All patients were hospitalized. No patient had received COVID-19 convalescent plasm. IAT was negative in all patients. DAT was performed using column agglutination technology, and samples that were DAT positive were further investigated using monospecific DAT facility. If the strength of DAT was 2+ or above with IgG then the elution was performed with an elution kit. The eluates were then tested with a commercial three-cell panel of RBCs to establish whether the IgG antibodies had any RBC antigen specificity. In case the DAT was positive for C3d, the cold agglutination titre was estimated. A chi-square test was used for discrete variables, and a student t-test or a Wilcoxon-Mann-Whitney test was used with p-values below 0.05 considered as significant. Results: There was no significant difference between the patients with positive DAT and patients with negative DAT (Table 1). DAT was positive in 32 of 88 (36.36%) patients. Of the 32 cases, 28 (87.5%) were positive for IgG only, one (3.13%) was positive for both IgG and complement, and three (9.38%) were positive for C3d.More than 2+ agglutination was seen in 6 (18.8%) patients. Out for those six cases two were positive for C3d only (4+) with a cold agglutination titre of 2048. None of the eluted samples in rest of the four cases with IgG reactivity showed specificity for RBC antigens in the three-cell panel. Total bilirubin and LDH values were not different between two groups which suggest that the anaemia in DAT-positive group was not due to haemolysis rather it could be associated with severity of disease. The increase morality that was observed in DAT-positive group might be explained similarly. Summary/Conclusions: Results of this study show that a high percentage of cancer patients with COVID-19 are DAT positive, but majority of these patients do not have any evidence of haemolysis and do not require more blood transfusion compared to others. The clinical implications of this high DAT positivity in COVID-19 patients need further exploration. (Table Presented).

Comparison of positivity to the direct coombs test in the 2 years before and after patient 1 in Italy at the UOC SIMT-CPE of ASL Rome 1

Background: The Direct Antiglobulin Test (DAT) is performed by testing the patient's red cells with poly or monospecific Anti Human Globulin (AHG) to demonstrate the in vivo link of red blood cells with antibodies and/or complement. The positive result of this test is usually due to the reaction of AHG with autoantibodies, alloantibodies (maternal or post transfusion) reactive against antigens present on the red cells, drugs that fix on the erythrocyte membrane (penicillin) or that alter it (cephalosporins), proteins often associated with hypergammaglobulinemia or I.V. infusion of immunoglobulins, complement fixation on red cells (from allo-autoAb, bacterial infections, drugs). Aims: The objective of this study is to understand if the positive result at DAT, in terms of frequency and specificity, has changed after the Covid 19 pandemic, and investigate the possible causes. Methods: We analysed the positive result of DAT performed on red cells of adult patients admitted to the wards of Asl Rome 1 and the affiliated clinics through the use of polypecific and monospecific sera (IgG, IgM, IgA, C3d, C3c) analysed using the IH 1000 System-Biorad Lab. All examinations performed was divided into two groups: those taken from 20/02/2018 to 20/02/2020 and from 21/02/2020 until 20/02/2022, representing the 2 years anniversary of the discovery of patient 1 in Italy. Results: In the first group of 101 patients who tested positive for DAT, 98% of them had positive results to IgG, while only the remaining 2% had positive results to the C3d isolated or associated with IgG. In the second group of 179 patients the positive results to IgG was 82% and the remaining 18% to C3d in isolation or in combination with IgG and C3c. We can observe how in the second group the overall positive results increased of about 80% and also the relative positive results to the C3d/C3c complement portion. It is also interesting to note that the positive results of only half of the second group (last 14 months in the period 2021-2022) are numerically about 50% higher than the previous year and 20% higher than the entire first group analysed (24 months). Summary/Conclusions: This increase in DAT positive results occurred in the second group, in particular in the last 14 months of the pandemic, could reflect the high levels of circulating immunoglobulins in the subjects analysed due to the endemic circulation of Sars Cov 2 virus and mass vaccination. These, according to our hypothesis, could have contributed to the outcome of positive results through a 'iatrogenic hypergammaglobulinemia' due to the high post vaccination titre and the immune response due to the increased circulation of the virus. It could also be assumed that the percentage of C3d detected 'Berzuini et al, Blood, 2020' is due to alterations of the complement receptors present on the surface of the red blood cells caused by the activation of the complement against the protein N of the nucleocapsid of the virus Sars Cov2 'J.E.Hendrickson and C.A.Tormey, Blood, 2020'.

Could autoimmune hemolytic anaemia be triggered by SARS-COV- 2 vaccine?-case report

Background: Autoimmnue hemolytic anaemia (AIHA) is characterized by the production of autoantibodies against red cells antigens, leading to hemolysis. AIHA can be primary or secondary to rheumatologic and lymphoproliferative diseases, infections, drugs and vaccines. Several immune phenomena were reported after massive SARS-CoV-2 vaccination, including myocarditis, neurological syndormes, immune thrombocytopenia, among others. Aims: We hereby describe an AIHA case possibly related to SARSCoV- 2 vaccination. Methods: Assessment of the clinical evaluation along with the laboratory and immunohematological tests in a symptomatic patient fwe days after receiving the vaccine. Results: A 72-year-old womwn, previously healthy, rceived her first dose of Coronavac (Sinovac, inactivated virus), in January 2021. After 7 days, she was admitted with fatigue and myalgia. Laboratory results revealed haemoglobin 4.9 g/dl, reticulocyte count 31.7%, total bilirubin 9.15 mg/dl, indirect bilirubin 7.88 mg/dl, haptoglobin<6 mg/dl and lactate dehydrogenase 953 U/L. The peripheral blood smear showed spherocytes and polychromasia. The nasopharyngeal PCR test for Covid-19 was negative. Regarding the immunohematological tests, the patient was group O R1K-k+, polyspecific direct antiglobulin test (DAT) was reactive for IgG and C3d, but the monospecific DAT showed only IgG. The eluate was reactive against all test cells. After all adsorptions performed, no alloantibody was detected and the eluate confirmed only the presence of an autoantibody, with no specificity. The patient was successfully managed with steroids, cyclophosphamide and transfusion support (OR1r, K-, antigens S and JKa negative, according with genotyping). No other causes of AIHA were found in the patient's screening and the patient did not have covid prior to vaccination. Summary/Conclusions: In this case, the temporal relationship between the vaccination and the symptoms of AIHA suggests a possible and rare haematological side effect of the vaccine which are able to activate both cellular and humoral immune systems with an important role in the interactions between dendritic cells, B and T cells, and the self-tolerance system. Since there is the increase of the global number of vaccinated people and few of this reports of this phenomenon have described in the literature, we considered it important to disclose this case in our service.

LOSS of TOLERANCE and ANERGY in HUMAN PERIPHERAL B CELLS during SARS-CoV-2 INFECTION

Background: Severe infection with SARS-CoV-2 induces systemic autoreactive antibodies with specificity to Type I IFN, phospholipids, nuclear or tissue specific targets. The wide breadth of targets suggests a system-wide defect in B cell tolerance during viral infection and that the source of autoreactive antibodies is likely a heterogenous subset of B cells. BND cells are mature naïve B cells that do not express IgM but do express IgD and are enriched in autoreactive specificities. BND cells are held in an anergic state in healthy humans as a mechanism of peripheral tolerance, although in vitro evidence suggests anergy can be broken with strong inflammation. We hypothesized that robust inflammation associated with viral infection from SARS-CoV2 may relax peripheral tolerance and promote breakage of BND cell anergy. Methods: Plasma and PBMCs were collected from healthy controls (N=10), subjects immunized with Pfizer BNT162b2-mRNA/Moderna mRNA-1273 (N=10), subjects with mild (N=11) or severe SARS-CoV-2 infection (N=14). BND cells were examined ex vivo for markers of activation by flow cytometry. Phosphorylation of signaling proteins downstream of the BCR were measured in vitro with or without BCR crosslinking. Inflammatory cytokines were measured in plasma by multiplex. For statistical analysis, unpaired t test between populations or paired t test between unstimulated and BCR stimulated conditions were performed. Results: BND cells from severe SARS-CoV-2 infection have lower expression of CD21, associated with loss of anergy, higher expression of activation markers CD68 and CD86 with lower expression of inhibitory receptors CD22 and CD72 when compared to BND cells from other subjects, suggesting a phenotypical breach of anergy. Upon BCR crosslinking, BND cells have higher levels of downstream signaling components of the BCR (pPLCγ2, pBlnk, and pSyk) when compared to healthy controls and immunized subjects, suggesting a functional breach in anergy with infection. Examination of plasma from severe SARS-CoV-2 infection showed higher levels of inflammatory cytokines (IFNγ, TNFα, IL-6 and CRP) where TNFα and CRP correlated with enhanced BCR signaling in BND cells. Conclusion: We demonstrate that SARS-CoV-2 viral infection relaxes peripheral tolerance of BND cells, likely through strong systemic inflammation produced during infection. These autoreactive cells overcome anergy and become activated with increased BCR signaling. Thus BND cells could be a source of autoreactive antibodies during viral infection.

COVID-19 ASSOCIADO COM ANEMIA HEMOLÍTICA AUTOIMUNE POR ANTICORPOS A FRIO: SÉRIE DE 3 CASOS

Introdução: A anemia hemolítica autoimune (AHAI) tem sido associada a muitas patologias conhecidas, incluindo doenças autoimunes, linfoproliferativos e certas doenças infecciosas, principalmente nos casos por anticorpos a frio. Tem surgido alguns relatos de caso de doença por SARS-Cov2 (COVID-19) associado a AHAI;no entanto, essa potencial associação ainda não é clara. Aqui relatamos uma serie 3 casos de Síndrome de aglutininas a frio (CAS), associada a infecção por Covid-19. Relato de caso: Três pacientes, com idades de 53 a 65 anos, sendo 2 homens e 1 mulher, foram admitidos em nosso serviço de fevereiro a maio de 2021, devido a infecção por Covid-19. Dois apresentavam síndrome aguda de angústia respiratória, mas sem necessidade de ventilação mecânica. Todos apresentavam anemia macrocítica, com hemoglobina que variava de 6,5-9,1 g/dL, DHL aumentado (311-679), e 2 com Birrubina indireta aumentada (1,05-2,55). Todos apresentavam teste de antiglobulina direto fortemente positivo as custas de C3d, com amplitude térmica de 24°C, e título a frio de 64-256. Dois pacientes não apresentavam comorbidades, 1 paciente havia sido internado recentemente para correção cirurgica de Doença arterial Cronica. Dois pacinetes fora tranfundidos com CH, entrtanto nenhum tratamento específico para AHAI foi estabelecido. Uma paciente foi transferida e perdeu seguimento e dois pacientes recuperam totalmente do quadro, e mantém-se após 3 e 4 meses de infecção com Hb >12 g/dL, sem necessidade de tratamento. Discussão e conclusão: Doença resultante de infecção por Covid-19 está associada a várias anormalidades hematológicas, incluindo linfopenia, fênomenos trombo-embólicos, trombocitopenia imune, síndrome antifosfolipídeo. Tem surgido alguns relatos de casos no último ano, associando AHAI a infecção por covid-19 e sugerindo que a desregulação imunológica teria como a etiologia subjacente o SARS-CoV-2. Aqui, detalhamos uma série de 3 paciente com infecção sintomática por SARS-CoV-2 que apresentram anemia sintomática de leve a grave e a a investigação foi consistente com anemia hemolítica autoimune por anticorpos a frio secundária à infecção por covid-19 (CAS), diagnóstico raro em nosso meio.

2nd Toronto Complement Conference

The proceedings contain 17 papers. The topics discussed include: a helix-swapped C3d dimer mediated by immune evasion protein Sbi hints at a novel s. aureus complement modulation strategy;the role of factor H in macrophages;an antibody targeting complement factor H causes anti-tumor immunity through B-cell activation;C5aR2 deficiency ameliorates inflammation in antibody transfer experimental epidermolysis Bullosa Acquisita and suggests regulating action on the decisive C5a receptor 1;clinical and biomarker characteristics of patients with C3G enrolled in two phase 2 studies investigating the factor D inhibitor Danicopan;perceiver-based machine learning diagnosis of TMA in renal biopsies;and recurrence of atypical hemolytic uremic syndrome After COVID-19 vaccination.

Hemolysis in COVID 19 Positive Patients: 2 Case Reports

Introduction: The presentation of SARS-CoV-2 (COVID 19) isvaried. Although, respiratory system is predominantly affected, AIHAboth warm and cold antibody types have also been reported in somepatients. We worked up 2 such patients who presented to us withCOVID symptoms along with unexplained hemolysis. The 1st patientpresented with mucormycosis and was on Amphotericin B. Bothpatients had history of blood transfusion. The 2nd patient on examination was found to have generalized lymphadenopathy. Peripheralsmear of 1st patient showed morphological features of hemolysis. Theother patient showed agglutination on peripheral smear that resolvedon preheating of sample before smear formation. On further workup,both showed Direct Agglutination Test (DAT) positivity with presence of autoantibodies as well as alloantibodies.Aims &Objectives: To workup and establish the cause of hemolysisin COVID positive patients.Materials &Methods: Routine complete blood count and peripheralsmear studies were performed for these patients along with relevantbiochemical tests. Samples were subjected to DAT and antibodyscreening. Both 3 cell and 11 cell panel testing was done by gel cardmethod (Bio Rad).Result: DAT was positive in both the cases, with IgG positivity in 1stcase, indicative of warm antibodies. 2nd case showed presence ofmixed antibodies with IgG, IgA, C3d, IgM and C3c positivity. Onextended antibody panel testing, 2-3 + reactivity was seen in bothcases in the whole panel with auto control positivity, indicative ofpresence of both auto and alloantibodies.Conclusions: Although immune mediated hemolysis in COVIDpatients is not uncommon, it should be labelled as the cause only afterall other common causes have been thoroughly looked into and ruledout.