Clinical Use and Therapeutic Potential of IVIG/SCIG, Plasma-Derived IgA or IgM, and Other Alternative Immunoglobulin Preparations

Antibody diversity in IVIG: Therapeutic opportunities for novel immunotherapeutic drugs

Significant progress has been made in the elucidation of human antibody repertoires. Furthermore, non-canonical functions of antibodies have been identified that reach beyond classical functions linked to protection from pathogens. Polyclonal immunoglobulin preparations such as IVIG and SCIG represent the IgG repertoire of the donor population and will likely remain the cornerstone of antibody replacement therapy in immunodeficiencies. However, novel evidence suggests that pooled IgA might promote orthobiotic microbial colonization in gut dysbiosis linked to mucosal IgA immunodeficiency. Plasma-derived polyclonal IgG and IgA exhibit immunoregulatory effects by a diversity of different mechanisms, which have inspired the development of novel drugs. Here we highlight recent insights into IgG and IgA repertoires and discuss potential implications for polyclonal immunoglobulin therapy and inspired drugs.

A new hope? Possibilities of therapeutic IgA antibodies in the treatment of inflammatory lung diseases

Inflammatory lung diseases represent a persistent burden for patients and the global healthcare system. The combination of high morbidity, (partially) high mortality and limited innovations in the last decades, have resulted in a great demand for new therapeutics. Are therapeutic IgA antibodies possibly a new hope in the treatment of inflammatory lung diseases? Current research increasingly unravels the elementary functions of IgA as protector against infections and as modulator of overwhelming inflammation. With a focus on IgA, this review describes the pathological alterations in mucosal immunity and how they contribute to chronic inflammation in the most common inflammatory lung diseases. The current knowledge of IgA functions in the circulation, and particularly in the respiratory mucosa, are summarized. The interplay between neutrophils and IgA seems to be key in control of inflammation. In addition, the hurdles and benefits of therapeutic IgA antibodies, as well as the currently known clinically used IgA preparations are described. The data highlighted here, together with upcoming research strategies aiming at circumventing the current pitfalls in IgA research may pave the way for this promising antibody class in the application of inflammatory lung diseases.

Polyvalent human immunoglobulin for infectious diseases: Potential to circumvent antimicrobial resistance

Antimicrobial resistance (AMR) is a global health problem that causes more than 1.27 million deaths annually; therefore, it is urgent to focus efforts on solving or reducing this problem. The major causes of AMR are the misuse of antibiotics and antimicrobials in agriculture, veterinary medicine, and human medicine, which favors the selection of drug-resistant microbes. One of the strategies proposed to overcome the problem of AMR is to use polyvalent human immunoglobulin or IVIG. The main advantage of this classic form of passive immunization is its capacity to enhance natural immunity mechanisms to eliminate bacteria, viruses, or fungi safely and physiologically. Experimental data suggest that, for some infections, local administration of IVIG may produce better results with a lower dose than intravenous application. This review presents evidence supporting the use of polyvalent human immunoglobulin in AMR, and the potential and challenges associated with its proposed usage.

Efficacy of Glucocorticoid plus Intravenous Immunoglobulin in Children with Immunoglobulin-Insensitive Kawasaki Disease

This study mainly analyzes the clinical effect of glucocorticoid (GC) plus intravenous immunoglobulin (IVIG) in treating children with immunoglobulin (Ig)-insensitive Kawasaki disease (KD). From September 2013 to November 2021, 86 Ig-insensitive KD children were selected, including 46 children (observation group, Obs) treated with GC plus IVIG, and 40 children (control group, Con) treated with IVIG. The symptom (fever and fever) resolution time, inflammatory factors (C-reactive protein, CRP; procalcitonin, PCT; interleukin-6, IL-6), immune indicators (CD3+, CD4+, CD8+ T lymphocytes CD3+, CD4+, and CD4+/CD8+), and incidence of adverse reactions were compared between the groups. The results identified shorter fever and rash resolution time in Obs compared with Con. The posttreatment CRP, PCT, IL-6, and CD8+ and the incidence of adverse events reduced notably in Obs and were lower than Con, while CD3+, CD4+, and CD4+/CD8+ elevated statistically and were higher than that of Con. Our results indicate that GC plus IVIG can significantly promote symptom resolution, alleviate inflammatory response, and improve immune function in children with Ig-insensitivity KD, with favorable safety and clinical promotion value.

The Functional Role of IgA in the IgM/IgA-Enriched Immunoglobulin Preparation Trimodulin

In comparison to human immunoglobulin (Ig) G, antibodies of IgA class are not well investigated. In line with this, the functional role of the IgA component in IgM/IgA-enriched immunoglobulin preparations is also largely unknown. In recent years, powerful anti-pathogenic and immunomodulatory properties of human serum IgA especially on neutrophil function were unraveled. Therefore, the aim of our work is to investigate functional aspects of the trimodulin IgA component, a new plasma-derived polyvalent immunoglobulin preparation containing ~56% IgG, ~23% IgM and ~21% IgA. The functional role of IgA was investigated by analyzing the interaction of IgA with FcαRI, comparing trimodulin with standard intravenous IgG (IVIG) preparation and investigating Fc receptor (FcR)-dependent functions by excluding IgM-mediated effects. Trimodulin demonstrated potent immunomodulatory, as well as anti-pathogenic effects in our neutrophil model (neutrophil-like HL-60 cells). The IgA component of trimodulin was shown to induce a strong FcαRI-dependent inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) signaling, counteract lipopolysaccharide-induced inflammation and mediate phagocytosis of Staphylococcus aureus. The fine-tuned balance between immunomodulatory and anti-pathogenic effects of trimodulin were shown to be dose-dependent. Summarized, our data demonstrate the functional role of IgA in trimodulin, highlighting the importance of this immunoglobulin class in immunoglobulin therapy.

Immunomodulation: Immunoglobulin Preparations Suppress Hyperinflammation in a COVID-19 Model via FcγRIIA and FcαRI

The rapid spread of SARS-CoV-2 has induced a global pandemic. Severe forms of COVID-19 are characterized by dysregulated immune response and "cytokine storm". The role of IgG and IgM antibodies in COVID-19 pathology is reasonably well studied, whereas IgA is neglected. To improve clinical outcome of patients, immune modulatory drugs appear to be beneficial. Such drugs include intravenous immunoglobulin preparations, which were successfully tested in severe COVID-19 patients. Here we established a versatile in vitro model to study inflammatory as well as anti-inflammatory processes by therapeutic human immunoglobulins. We dissect the inflammatory activation on neutrophil-like HL60 cells, using an immune complex consisting of latex beads coated with spike protein of SARS-CoV-2 and opsonized with specific immunoglobulins from convalescent plasma. Our data clarifies the role of Fc-receptor-dependent phagocytosis via IgA-FcαRI and IgG-FcγR for COVID-19 disease followed by cytokine release. We show that COVID-19 associated inflammation could be reduced by addition of human immunoglobulin preparations (IVIG and trimodulin), while trimodulin elicits stronger immune modulation by more powerful ITAMi signaling. Besides IgG, the IgA component of trimodulin in particular, is of functional relevance for immune modulation in this assay setup, highlighting the need to study IgA mediated immune response.

Enhanced Pro-apoptotic Effects of Fe(II)-Modified IVIG on Human Neutrophils

Mild modification of intravenous immunoglobulin (IVIG) has been reported to result in enhanced polyspecificity and leveraged therapeutic effects in animal models of inflammation. Here, we observed that IVIG modification by ferrous ions, heme or low pH exposure, shifted the repertoires of specificities in different directions. Ferrous ions exposed Fe(II)-IVIG, but not heme or low pH exposed IVIG, showed increased pro-apoptotic effects on neutrophil granulocytes that relied on a FAS-dependent mechanism. These effects were also observed in human neutrophils primed by inflammatory mediators or rheumatoid arthritis joint fluid in vitro, or patient neutrophils ex vivo from acute Crohn's disease. These observations indicate that IVIG-mediated effects on cells can be enhanced by IVIG modification, yet specific modification conditions may be required to target specific molecular pathways and eventually to enhance the therapeutic potential.

Immunoglobulin Therapy in a Patient With Severe Chikungunya Fever and Vesiculobullous Lesions

Chikungunya virus (CHIKV) is an emerging arbovirus whose transmission has already been reported in several countries. Although the majority of individuals acutely infected with CHIKV appear to become asymptomatic, reports showing the occurrence of atypical and severe forms of the disease are increasing. Among them, the neurological and skin manifestations require medical attention. Treatment of CHIKV infection is almost symptomatic. In this sense, we report the case of a 56-years-old man who presented fever, headaches, paresthesia and pain in the right arm with visible red spots on the skin starting 30 days before Hospital admission. Tests determined Chikungunya infection and excluded other co-morbidities. Disease evolved with edema in hands and feet and extensive hemorrhagic bullous lesions on the skin of upper and lower limbs. Variations in hematological counts associated with liver dysfunction determined this patient's admission to the Intensive Care Unit. Then, he received intravenous antibiotic and immunoglobulin therapy (400 mg/Kg/day for the period of 5 days) with total recovery from the lesions after 10 days of follow-up. A general improvement in blood cell count and successful wound healing was observed. After discharge, no other clinical sign of the disease was reported until nowadays. This case reports for the first time the successful administration of intravenous immunoglobulin therapy to a patient with severe atypical dermatological form of Chikungunya Fever without any associated comorbidity.

The neonatal Fc receptor: Key to homeostasic control of IgG and IgG-related biopharmaceuticals

IgG and albumin are the most abundant proteins in the circulation and have the longest half-lives. These properties are due to a unique receptor, the neonatal Fc receptor (FcRn). Although FcRn is named for its function of transferring IgG across the placenta from maternal to fetal circulation, FcRn functions throughout life to maintain IgG and albumin concentrations. FcRn protects IgG and albumin from intracellular degradation and recycles them back into the circulation. Clinical trials have confirmed that pathogenic antibodies can be depleted by blocking this homeostatic function of FcRn. Moreover, understanding the molecular interactions between IgG and FcRn has resulted in the design of therapeutic monoclonal antibodies with more efficacious pharmacokinetics. As a result of genetic engineering these monoclonals can be delivered at lower doses and at longer intervals. More recent findings have demonstrated that FcRn enhances phagocytosis by neutrophils, immune complex clearance by podocytes and antigen presentation by dendritic cells, macrophages, and B cells. This minireview highlights the relevance of FcRn to transplantation.

Differential Recognition of Diet-Derived Neu5Gc-Neoantigens on Glycan Microarrays by Carbohydrate-Specific Pooled Human IgG and IgA Antibodies

Sialic acids (Sias) cover vertebrate cell surface glycans. N-Acetylneuraminic acid (Neu5Ac) and its hydroxylated form N-glycolylneuraminic acid (Neu5Gc) are common Sia in mammals. Humans cannot synthesize Neu5Gc but accumulate it on cells through red-meat rich diets, generating numerous immunogenic Neu5Gc-neoantigens. Consequently, humans have diverse anti-Neu5Gc antibodies affecting xenotransplantation, cancer, atherosclerosis, and infertility. Anti-Neu5Gc antibodies circulate as IgG, IgM, and IgA isotypes; however, repertoires of the different isotypes in a large population have not been studied yet. Here, we used glycan microarrays to investigate anti-Neu5Gc IgGs and IgAs in intravenous immunoglobulin (IVIG) or pooled human IgA, respectively. Binding patterns on microarrays fabricated with Neu5Gc- and Neu5Ac-glycans, together with inhibition assays, revealed that different IVIG preparations have highly specific anti-Neu5Gc IgG reactivity with closely related repertoires, while IgAs show cross-reactivity against several Neu5Ac-glycans. Such different anti-Neu5Gc IgG/IgA repertoires in individuals could possibly mediate distinctive effects on human diseases.

High dose IVIG successfully reduces high rhGAA IgG antibody titers in a CRIM-negative infantile Pompe disease patient

Alglucosidase alfa (rhGAA) has altered the course of an otherwise fatal outcome in classic infantile Pompe disease (IPD), which presents with cardiomyopathy and severe musculoskeletal involvement. However, the response to therapy is determined by several factors including the development of high and sustained antibody titers (HSAT) to rhGAA. Cross-reactive immunologic material (CRIM) negative patients are at the highest risk for development of HSAT. Immune tolerance induction (ITI) with methotrexate, rituximab, and intravenous immunoglobulin (IVIG) has been largely successful in preventing the immune response and in achieving tolerance when done in conjunction with enzyme replacement therapy (ERT) initiation. Reducing antibody titers in cases with an entrenched immune response remains a challenge in the field despite the use of multiple immunomodulatory agents. Success has been shown with addition of bortezomib to the ITI regimen, yet the prolonged course and potential risks with the use of such agents' demands caution. We present here a 7-year-old CRIM-negative IPD patient who was not successfully tolerized by an ITI regimen with rituximab, methotrexate, and IVIG due to intolerability to the regimen and recurrent infections. She went on to develop HSAT, with significant clinical decline, loss of all motor abilities, and a fragile medical state, which made it challenging to institute the bortezomib based regimen to reduce HSAT. She had severe developmental delay, respiratory failure with invasive ventilation and tracheostomy, persistent hypotonia, ptosis of eyelids, diffuse severe osteopenia, contractures, and was completely G-tube fed. As a rescue mechanism, we treated her with high dose and high frequency IVIG in an attempt to reduce rhGAA IgG antibody titers (antibody titers; titers). Her titers saw a steady decline on weekly IVIG doses at 1g/kg for 20weeks. Subsequently when the IVIG regimen was altered to 1g/kg every month, rising titers were detected and therefore the regimen was changed to a biweekly regimen. High dose IVIG resulted in an eightfold decrease in antibody titers. Clinically, she showed improvement with partial recovery of previously lost motor abilities, especially hand movements and better head and neck control than before. The regimen was safely tolerated with no hospitalizations. The effectiveness of IVIG as a single agent, in this case with multiple comorbidities and fragile clinical status, was lifesaving and may represent an effective, perhaps lifesaving rescue approach to reduce antibody titers.