Abundance of B Cell Receptors Harboring Elongated Polytyrosine and Polyserine Rich Motifs within Their Heavy Chain CDR3 Distinguishes Catastrophic and Antiphospholipid Syndrome

ACKGROUND: Antiphospholipid syndrome (APS) is defined by arterial and/or venous thrombosis and/or pregnancy morbidity along with persistent circulating antiphospholipid antibodies (aPL). Central to APS pathogenesis are B cells that generate autoreactive antibodies, including anticardiolipin antibodies (aCL), and anti-β2-glycoprotein-I antibodies (anti-B2GPI). Several studies have implicated specific germline and/or antigen-driven somatic hypermutations within the complementarity determining regions (CDRs) of pathogenic antibodies in APS, as well as other thrombotic disorders. Nevertheless, the B cell repertoire in thrombotic APS remains poorly characterized. Recently, autoreactive and platelet activating pathogenic antibodies harboring elongated tyrosine rich CDR3 motifs were reported in patients with heparin-induced thrombocytopenia (HIT) (Zhu et.al, Blood 2019, 2020). Whether such antibodies are present in APS and their potential role, if so, has not been determined. APPROACH : We leveraged single cell immunoprofiling to characterize the presence of antibodies harboring elongated tyrosine rich CDR3 motifs in the circulating B cell repertoire obtained from peripheral blood mononuclear cells (PBMC) from patients with thrombotic (n=4) and catastrophic APS (n=3) as well as healthy individuals (n=3). We also correlated the abundance of these antibodies with criteria aPL and inflammatory cytokines in plasma. The modified Ham (mHam) test was used to assess functional complement activation in plasma in plasma from all of the subjects studied (Chaturvedi et al. Blood 2020). RESULTS : B cell clones containing elongated polytyrosine rich CDR3 motifs were most abundant in patients with a diagnosis of catastrophic APS (n=3) , and were markedly elevated in patients with APS (n=4) compared to healthy counterparts (n=3) (Table 1). Elongated polytyrosine rich CDR3 motifs from CAPS patients contained penta-tyrosine (Y5), hexa-tyrosine (Y6), hepta-tyrosine (Y7), and octa-tyrosine (Y8) motifs (table 2) and contained more tyrosine residues than the penta-tyrosines previously reported in HIT. In addition, all of the polytyrosine containing motifs CDR3 motifs were present on the heavy chain and was followed by MDVW motif of IGHJ6. The presence of B cell clones containing elongated polytyrosine rich CDR3 motifs exhibited significant positive correlations with complement activation measured by mHAM test (r=0.728, p=0.0032), criteria aPLs including anticardiolipin antibodies (aCL) and anti-β2-glycoprotein-I antibodies (anti-B2GPI), as well as plasma inflammatory cytokines; TNFα (r=0.901, p=1.5x10 -5), IL-23 (r=0.780, p=0.0016), IL-17C cytokines (r=0.729, p=0.0033), sICAM1 (r=0.740, p=0.0025), sVCAM1 (r=0.764, p=0.0015), (Figure 1). The presence of elongated polytyrosine rich CDR3 motifs was also associated with the increase abundance of polyserine rich CDR3 motifs that were present predominantly in patients with CAPS. CONCLUSION : These preliminary studies provide the first characterization of the prevalence of B cell clones containing elongated polytyrosine rich CDR3 motifs, previously reported in HIT, in the B cell repertoire of APS patients. Notably, the abundance of these B cell clones is markedly elevated in patients with CAPS and is associated with elevated levels of inflammatory cytokines TNFa, IL-23, IL-17C, sICAM1, and sVCAM1. Validation studies in larger cohorts from APS patients and other thrombotic disorders are ongoing. Figure 1 Figure 1. Disclosures Chaturvedi: Alexion: Other: Advisory board member; Dova: Other: Advisory board member; Sanofi Genzyme: Other: Advisory board member; Argenx: Other: Advisory board member; UCB: Other: Advisory board participation. Khorana: Bristol Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Anthos: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Halozyme: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Bayer: Consultancy, Honoraria. McCrae: Sanofi, Novartis, Alexion, and Johnson & Johnson: Consultancy, Honoraria; Dova, Novartis, Rigel, and Sanofi Genzyme: Consultancy.

Fc-Modified Kko: A Novel Therapeutic for Heparin-Induced Thrombocytopenia (HIT), Reversing Both the Thrombocytopenia and Thrombosis

Heparin induced thrombocytopenia (HIT) is an immunogenic prothrombotic disorder caused by antibodies that recognize human platelet factor 4 (PF4) complexed to polyanions. We had previously shown using chimeric constructs of hPF4 and mouse (m) PF4 and chimeras with the related chemokine, neutrophil-activating peptide-2 that there is a single antigenic locus on hPF4 in these complexes to which most HIT antibodies bind. KKO is a mouse monoclonal IgG2b k anti-hPF4/polyanion monoclonal antibody that mimics pathogenic antibodies that induce HIT and provokes thrombosis in a murine model of HIT. We previously established that specific hydrolysis of N-linked glycans in the Fc-region of KKO by endoglycosidase from Streptococcus pyogenes EndoS (Genovis) yields >97% deglycosylation on LC-MS/MS generating DGKKO. This modification has no significant effect on binding to PF4-heparin complexes as shown by ELISA and by dynamic light scattering, but abrogates FcgRIIA-mediated binding and platelet activation, and decreases complement activation as evaluated by flow cytometry. To examine if DGKKO reduces prothrombotic effects, we compared DGKKO with KKO in human microfluidic system lined with human umbilical vein cells (HUVECs) that are then photochemically injured and a murine model involving "HIT mice" (mice that express FcgRIIA and human PF4 and lack mouse PF4). Using the microfluidic system described above and infusing blood from healthy donors with added human PF4 (25 µg/ml) and KKO (50 µg/ml) or HIT IgG from three individuals with SRA-positive HIT (1mg/ml) resulted in increased platelet adherence to the injured endothelium (Figure 1). Addition of DGKKO (50 µg/ml) 15 minutes after addition of HIT antibodies eliminated platelet accumulation (Figure 1). In the HIT murine model, we found that intraperitoneal (IP, 200 µg/mice) or intravenous (IV, 20 µg/mice) DGKKO did not induce thrombocytopenia in HIT mice, but reversed the thrombocytopenia induced by either IP KKO (200 µg/mice) or HIT IgG (1 mg/mice) even when the DGKKO is given 6 hrs after HIT induction (Figure 2A). We used an intravital cremaster laser arteriole injury model in HIT mice to study the efficacy of DGKKO as an antithrombotic agent. We found that unlike KKO that enhances growth of established thrombi in these mice, DGKKO significantly reversed the size of the observed thrombi (Figure 2B). These studies suggest that DGKKO obstructs the HIT antigenic site recognized by HIT antibodies and leads to a reversal of thrombocytopenia and thrombus size. Additional studies are underway to examine if DGKKO can be used as a monotherapy or adjunctive therapy in the murine model of HIT thrombosis. Figure 1 Figure 1. Disclosures Cines: Rigel: Consultancy; Dova: Consultancy; Treeline: Consultancy; Arch Oncol: Consultancy; Jannsen: Consultancy; Taventa: Consultancy; Principia: Other: Data Safety Monitoring Board.

Case Report: Oral Cimetidine Administration Causes Drug-Induced Immune Hemolytic Anemia by Eliciting the Production of Cimetidine-Dependent Antibodies and Drug-Independent Non-specific Antibodies

Previously, it was reported that multiple patients had hemolytic anemia associated with cimetidine administration, while only one patient who had received intravenous cimetidine was serologically diagnosed with drug-induced immune hemolytic anemia (DIIHA) caused by cimetidine-dependent antibodies. However, the ability of oral cimetidine intake to induce the production of antibodies has not been examined. In this study, we report a 44-year-old male patient in whom oral cimetidine administration resulted in cimetidine-dependent antibodies and drug-independent non-specific antibodies, leading to the development of DIIHA. Serological tests showed that the results of direct antiglobulin test (DAT) for anti-IgG (3+) and anti-C3d (1+) were positive. The IgM and IgG cimetidine-dependent antibodies (the highest total titer reached 4,096) were detected in the plasma incubated with O-type RBCs and 1 mg/mL cimetidine or the plasma incubated with cimetidine-coated RBCs. IgG-type drug-independent non-specific antibodies were detected in blood samples collected at days 13, 34, 41, and 82 post-drug intake. This is the first study to report that oral administration of cimetidine can elicit the production of cimetidine-dependent antibodies, leading to DIIHA, and the production of drug-independent non-specific antibodies, resulting in hemolytic anemia independent of cimetidine. Presence of pathogenic antibodies were detectable longer than 41 days. This suggests that patients with DIIHA caused by cimetidine need to be given necessary medical monitoring within 41 days after cimetidine intake.

Emerging Biomarkers and Therapeutic Strategies for Refractory Bullous Pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disorder in the elderly. Systemic and topical use of glucocorticoids and immunosuppressants has been shown to be effective in most patients. However, refractory BP patients are challenged to clinicians with severe clinical symptoms, resistance to treatment, and high relapse rate. How to predict and assess the refractory and severity of bullous pemphigoid is the key issue in clinical practice, and the urgent need for precision medicine in refractory patients is driving the search for biomarkers and biologics. Recently, some biomarkers, such as the level of specific autoantibodies and released cytokines, have been proposed as the potential parameters to reflect the disease severity and predict the treatment response and relapse of refractory BP. Moreover, new biologics targeting pathogenic antibodies, complement, Th2 axis, eosinophils, and Th17 axis have shown potent efficacy on refractory BP. Here, we review the literature and give an overview of emerging biomarkers and therapeutic strategies for refractory bullous pemphigoid to improve the prognosis of the patient.

A drug candidate for treating adverse reactions caused by pathogenic antibodies inducible by COVID-19 virus and vaccines

In a previous study, we reported that certain anti-spike antibodies of COVID-19 and SARS-CoV viruses can have a pathogenic effect through binding to sick lung epithelium cells and misleading immune responses to attack self-cells. We termed this new pathogenic mechanism Antibody Dependent Auto-Attack (ADAA). This study explores a drug candidate for prevention and treatment of such ADAA-based diseases. The drug candidate is a formulation comprising N-acetylneuraminic acid methyl ester (NANA-Me), an analog of N-acetylneuraminic acid. NANA-Me acts through a unique mechanism of action (MOA) which is repairment of the missing sialic acid on sick lung epithelium cells. This MOA can block the antibody binding to sick cells, which are vulnerable to pathogenic antibodies. Our in vivo data showed that the formulation significantly reduced the sickness and deaths caused by pathogenic anti-spike antibodies. Therefore, the formulation has the potential to prevent and treat the serious conditions caused by pathogenic antibodies during a COVID-19 infection. In addition, the formulation has potential to prevent and treat the adverse reactions of COVID-19 vaccines because the vaccines can induce similar antibodies, including pathogenic antibodies. The formulation will be helpful in increasing the safety of the vaccines without reducing the vaccine efficacy. Compared to existing antiviral drugs, the formulation has a unique MOA of targeting receptors, broad spectrum of indications, excellent safety profile, resistance to mutations, and can be easily produced.

Pathogenic antibodies induced by spike proteins of COVID-19 and SARS-CoV viruses

This study, using a virus-free mouse model, explores the pathogenic roles of certain antibodies specific to the spike proteins of highly pathogenic coronaviruses such as the COVID-19 and the SARS-CoV viruses. Our data showed that these pathogenic antibodies, through a mechanism of Antibody Dependent Auto-Attack (ADAA), target and bind to host vulnerable cells or tissues such as damaged lung epithelium cells, initiate a self-attack immune response, and lead to serious conditions including ARDS, cytokine release, and death. Moreover, the pathogenic antibodies also induced inflammation and hemorrhage of the kidneys, brain, and heart. Furthermore, the pathogenic antibodies can bind to unmatured fetal tissues and cause abortions, postpartum labors, still births, and neonatal deaths of pregnant mice. Novel clinical interventions, through disrupting the host-binding of these pathogenic antibodies, can be developed to fight the COVID-19 pandemic. In addition, the new concept of ADAA explored by this study may be applicable to other infectious diseases, such as the highly pathogenic influenza infections. It should be noted that the majority of anti-spike antibodies are non-pathogenic, as only 2 of 7 monoclonal antibodies tested showed significant pathogenic effects.

Pathogenic antibodies induced by spike proteins of COVID-19 and SARS-CoV viruses

This study, using a virus-free mouse model, explores the pathogenic roles and novel mechanism of action of certain antibodies specific to the spike proteins of highly pathogenic coronaviruses such as the COVID-19 and the SARS-CoV viruses. These pathogenic antibodies, induced during a highly pathogenic infection such as the COVID-19 infection, target and bind to host vulnerable cells or tissues such as damaged lung epithelium cells, initiate a persistent self-attack immune response, and lead to serious conditions including ARDS, cytokine storms, and death. Moreover, the pathogenic antibodies may also be responsible for infection-related autoimmune diseases, including those experienced by COVID-19 long haulers. Furthermore, the pathogenic antibodies can bind to the unmatured fetal tissues and cause abortions, postpartum labors, still births, and neonatal deaths of pregnant females. Novel clinical interventions, through disrupting the binding of these pathogenic antibodies, can be developed to fight the COVID-19 pandemic. In addition, the new concept explored by this study may be applicable to other infectious diseases, such as the highly pathogenic influenza infections.

SARS-CoV-2 receptor binding domain-specific antibodies activate platelets with features resembling the pathogenic antibodies in heparin-induced thrombocytopenia

Severe COVID-19 is associated with unprecedented thromboembolic complications. We found that hospitalized COVID-19 patients develop immunoglobulin Gs (IgGs) that recognize a complex consisting of platelet factor 4 and heparin similar to those developed in heparin-induced thrombocytopenia and thrombosis (HIT), however, independent of heparin exposure. These antibodies activate platelets in the presence of TLR9 stimuli, stimuli that are prominent in COVID-19. Strikingly, 4 out of 42 antibodies cloned from IgG1+ RBD-binding B cells could activate platelets. These antibodies possessed, in the heavy-chain complementarity-determining region 3, an RKH or Y5 motif that we recently described among platelet-activating antibodies cloned from HIT patients. RKH and Y5 motifs were prevalent among published RBD-specific antibodies, and 3 out of 6 such antibodies tested could activate platelets. Features of platelet activation by these antibodies resemble those by pathogenic HIT antibodies. B cells with an RKH or Y5 motif were robustly expanded in COVID-19 patients. Our study demonstrates that SARS-CoV-2 infection drives the development of a subset of RBD-specific antibodies that can activate platelets and have activation properties and structural features similar to those of the pathogenic HIT antibodies.