Circulating IgA Antibodies Research Articles

Mucosal immunity in COVID-19: a comprehensive review.

Mucosal immunity plays a crucial role in defending against coronaviruses, particularly at respiratory sites, serving as the first line of defense against viral invasion and replication. Coronaviruses have developed various immune evasion strategies at the mucosal immune system, hindering the recognition of infected cells and evading antibody responses. Understanding the immune mechanisms and responses is crucial for developing effective vaccines and therapeutics against coronaviruses. The role of mucosal immunity in COVID-19 is significant, influencing both local and systemic immune responses to the virus. Although most clinical studies focus on antibodies and cellular immunity in peripheral blood, mucosal immune responses in the respiratory tract play a key role in the early restriction of viral replication and the clearance of SARS-CoV-2. Identification of mucosal biomarkers associated with viral clearance will allow monitoring of infection-induced immunity. Mucosally delivered vaccines and those under clinical trials are being compared and contrasted to understand their effectiveness in inducing mucosal immunity against coronaviruses. A greater understanding of lung tissue-based immunity may lead to improved diagnostic and prognostic procedures and novel treatment strategies aimed at reducing the disease burden of community-acquired pneumonia, avoiding the systemic manifestations of infection and excess morbidity and mortality. This comprehensive review article outlines the current evidence about the role of mucosal immune responses in the clearance of SARS-CoV-2 infection, as well as potential mucosal mechanisms of protection against (re-)infection. It also proposes that there is a significant role for mucosal immunity and for secretory as well as circulating IgA antibodies in COVID-19, and that it is important to elucidate this in order to comprehend especially the asymptomatic and mild states of the infection, which appear to account for the majority of cases. Moreover, it is possible that mucosal immunity can be exploited for beneficial diagnostic, therapeutic, or prophylactic purposes. The findings from recent studies on mucosal immunity in COVID-19 can be used to develop effective vaccines and treatments that can effectively target both mucosal and systemic immune responses.

Circulating IgA Antibodies Against Fusobacterium nucleatum Amyloid Adhesin FadA are a Potential Biomarker for Colorectal Neoplasia.

Fn, an oral anaerobe highly prevalent in colorectal cancer, secretes the amyloid-like FadAc to promote colorectal cancer tumorigenesis. We report that circulating levels of anti-FadAc IgA, but not IgG, are increased in patients with both early and advanced colorectal cancer compared with the healthy controls, and especially in those with proximal colorectal cancer. Anti-FadAc IgA may be developed into a serological biomarker for early detection of colorectal cancer.

Etiopathogenesis of dermatitis herpetiformis.

Dermatitis herpetiformis is a rare chronic, autoimmune bullous disease linked to gluten sensitivity with intense pruritus and characteristic skin eruptions. Etiopathogenesis is complex and not fully understood. It is currently considered to be a specific cutaneous manifestation of celiac disease. Genetic, environmental and immunological factors influence both conditions. Exposure to gluten is the starting point of an inflammatory cascade leading to the formation of circulating IgA antibodies against tissue transglutaminase and skin immune IgA deposition followed by skin lesions. Binding of the immune complex deposits of IgA transglutaminases and epidermal antibodies with enzymes in the papillary dermis stimulates complement activation, neutrophil influx, proinflammatory cytokine release and overproduction of matrix metalloproteinases. We have collected current knowledge of the pathogenesis of dermatitis herpetiformis.

Multiplexed analysis of circulating IgA antibodies for SARS-CoV-2 and common respiratory pathogens in COVID-19 patients.

Previous studies have revealed a diagnostic role of pathogen-specific IgA in respiratory infections. However, co-detection of serum specific IgA for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and common respiratory pathogens remains largely unexplored. This study utilizes a protein microarray technology for simultaneous and quantitative measurements of specific IgAs for eight different respiratory pathogens including adenovirus, respiratory syncytial virus, influenza virus type A, influenza virus type B, parainfluenza virus, mycoplasma pneumoniae, chlamydia pneumoniae, and SARS-CoV-2 in serum sample of patients with coronavirus disease 2019 (COVID-19). A total of 42 patients with COVID-19 were included and categorized into severe cases (20 cases) and nonsevere cases (22 cases). The results showed that co-detection rate of specific-IgA for SARS-CoV-2 with at least one pathogen were significantly higher in severe cases than that of nonsevere cases (72.2% vs. 46.2%, p = .014). Our study indicates that co-detection of IgA antibodies for respiratory pathogens might provide diagnostic value for the clinics and also be informative for risk stratification and disease management in patients with COVID-19.

Mucosal Immunity in COVID-19: A Neglected but Critical Aspect of SARS-CoV-2 Infection.

The mucosal immune system is the largest component of the entire immune system, having evolved to provide protection at the main sites of infectious threat: the mucosae. As SARS-CoV-2 initially infects the upper respiratory tract, its first interactions with the immune system must occur predominantly at the respiratory mucosal surfaces, during both inductive and effector phases of the response. However, almost all studies of the immune response in COVID-19 have focused exclusively on serum antibodies and systemic cell-mediated immunity including innate responses. This article proposes that there is a significant role for mucosal immunity and for secretory as well as circulating IgA antibodies in COVID-19, and that it is important to elucidate this in order to comprehend especially the asymptomatic and mild states of the infection, which appear to account for the majority of cases. Moreover, it is possible that mucosal immunity can be exploited for beneficial diagnostic, therapeutic, or prophylactic purposes.

Synthetic peptides reproducing tissue transglutaminase-gliadin complex neo-epitopes as probes for antibody detection in celiac disease patients' sera.

Celiac disease (CD) patients usually present high levels of circulating IgA antibodies directed to different antigens, in particular tissue transglutaminase (tTG), gliadin (Glia), and endomysium. A series of synthetic peptide constructs containing cross-linked tTG and Glia deamidated peptides have been synthesized. Peptides were tested in enzyme-linked immunosorbent assays against celiac disease patients' sera versus normal blood donors, and their conformational features were evaluated by molecular modeling techniques. Four peptides were recognized as epitopes by autoantibodies (IgG class) circulating in CD patients' sera before gluten-free diet. The peptide II, containing Ac-tTG(553-564)-NH2 sequence cross-linked with deamidated Ac-α2-Glia(63-71)-NH2, was able to identify specific disease antibodies with a sensitivity of 50% and a specificity of 94.4%. Structural conformations of the linear fragments Ac-tTG(553-564)-NH2 and Ac-α2-Glia(63-71)-NH2 and the corresponding cross-linked peptide II were calculated by molecular modeling. Results showed that cross-linking is determinant to assume conformations, which are not accessible to the linear fragments.

Peripheral T-cell lymphoma complicated by immunoglobulin A pemphigus: A case report and literature review.

Peripheral T-cell lymphomas (PTCLs) account for 12% of non-Hodgkin’s lymphomas (NHLs). Immunoglobulin (Ig) A pemphigus is an autoimmune blistering disease characterized by tissue-bound and circulating IgA antibodies that target epidermal cell surface components. Malignant lymphomas are often linked with autoimmune disease and the autoimmune blistering disease, paraneoplastic pemphigus, has been associated with NHL. However, cases of PTCLs that are complicated by IgA pemphigus are particularly rare. The current study presents the first known case of PTCL complicated by IgA pemphigus. A 43-year-old male was admitted to the Union Hospital (Wuhan, China) in March 2012 with multiple swollen lymph nodes. Pathology examinations revealed PTCL. Immunohistochemical staining was positive for cluster of differentiation (CD)2, CD3, CD5, CD7 and CD47, and negative for CD20. Ki-67 was ~40% positive. The patient was treated with four cycles of cyclophosphamide, Adriamycin, vincristine and prednisone, and two cycles of gemcitabine, cisplatin and dexamethasone; in addition, the patient received radiation of the retroperitoneal region (total dose, 36 Gy). The patient underwent thalidomide maintenance therapy for 20 days before flaccid blisters appeared on the trunk and limbs. Histopathology and immunofluorescence indicated IgA pemphigus, and intravenous methylprednisolone was administered, followed by treatment with prednisone. Subsequently, no evidence of recurrent lymphoma or pemphigus has been observed.

Domestic cat microsphere immunoassays: Detection of antibodies during feline immunodeficiency virus infection

Microsphere immunoassays (MIAs) allow rapid and accurate evaluation of multiple analytes simultaneously within a biological sample. Here we describe the development and validation of domestic cat-specific MIAs for a) the quantification of total IgG and IgA levels in plasma, and b) the detection of IgG and IgA antibodies to feline immunodeficiency virus (FIV) capsid (CA) and surface (SU) proteins, and feline CD134 in plasma. These assays were used to examine the temporal antibody response of domestic cats infected with apathogenic and pathogenic FIVs, and domestic cats infected with parental and chimeric FIVs of varying pathogenicity. The results from these studies demonstrated that a) total IgG antibodies increase over time after infection; b) α-CA and α-SU IgG antibodies are detectable between 9 and 28days post-infection and increase over time, and these antibodies combined represent a fraction (1.8 to 21.8%) of the total IgG increase due to infection; c) measurable α-CD134 IgG antibody levels vary among individuals and over time, and are not strongly correlated with viral load; d) circulating IgA antibodies, in general, do not increase during the early stage of infection; and e) total IgG, and α-CA and α-SU IgG antibody kinetics and levels vary with FIV viral strain/pathogenicity. The MIAs described here could be used to screen domestic cats for FIV infection, and to evaluate the FIV-specific or total antibody response elicited by various FIV strains/other diseases.

A case of vancomycin‐induced linear IgA bullous dermatosis with circulating IgA antibodies to the NC16a domain of BP180

A case of vancomycin‐induced linear IgA bullous dermatosis with circulating IgA antibodies to the <scp>NC</scp>16a domain of <scp>BP</scp>180

IgA Anti-p200 Pemphigoid

Anti-p200 pemphigoid is a rare autoimmune subepidermal blistering disorder. Clinically, it may resemble bullous pemphigoid, linear IgA bullous dermatosis, or dermatitis herpetiformis. Immunologically, anti-p200 pemphigoid is characterized by the development of IgG antibodies directed against a basement membrane zone protein with a molecular weight of 200 kDa. We report the first case, to our knowledge, of anti-p200 pemphigoid associated with IgA antibodies and having clinical features resembling pemphigus herpetiformis or dermatitis herpetiformis localized on traumatized areas. Histopathological examination of lesional skin showed dermal-epidermal separation and microabscesses composed of neutrophils in the dermal papillae. Direct immunofluorescence disclosed the presence exclusively of linear in vivo-bound IgA along the basement membrane zone. With the use of laser scanning confocal microscopy, in vivo-bound IgA was localized above collagen type IV and colocalized with laminin 332. Indirect immunofluorescence showed circulating IgA antibodies against basement membrane zone at a titer of 1:160 that reacted with the floor of an artificial blister of salt-split skin. Western immunoblot analysis using dermal extract confirmed the reactivity of circulating IgA antibodies with the 200-kDa antigen corresponding to laminin γ1; however, immunoblotting using recombinant protein of 107 amino acid C-terminus of laminin γ1 was negative for circulating IgA antibodies. Immunoelectron microscopy disclosed the reactivity of circulating IgA autoantibodies within the lower lamina lucida. To the best of our knowledge, this is the first case fulfilling the immunopathological criteria for anti-p200 pemphigoid associated with IgA antibodies and having unusual clinical features.

IgA pemphigus

Pemphigus is a life-threatening autoimmune blistering disease. Pemphigus is divided into 4 major types; pemphigus vulgaris, pemphigus foliaceus, paraneoplastic pemphigus, and IgA pemphigus. Among them, IgA pemphigus is characterized by tissue-bound and circulating IgA antibodies targeting desmosomal or nondesmosomal cell surface components in the epidermis. Histopathologically, slight epidermal acantholysis and extensive neutrophilic infiltration in either the upper part or all layers of the epidermis were observed. IgA pemphigus is subdivided into intraepidermal neutrophilic IgA dermatosis-type (IEN-type), whose target antigen is still unknown (probably nondesmosomal cell surface protein), and subcorneal pustular dermatosis-type (SPD-type), whose target antigen is desmocollin 1 (Dsc1). We summarize reported cases of IgA pemphigus and describe current knowledge including epidemiology, clinical manifestations, pathology, laboratory tests, pathophysiology, associated diseases, prognosis and treatment, and future perspectives of IgA pemphigus.

Linear immunoglobulin A bullous dermatosis

Linear immunoglobulin A bullous dermatosis (LABD) is a rare acquired, heterogeneous, subepidermal blistering disease characterized by linear IgA deposits at the dermal–epidermal basement membrane zone, often with circulating IgA antibodies in the basement membrane zone. Linear IgA disease shares many characteristics with other subepidermal bullous diseases, mainly bullous pemphigoid and dermatitis herpetiformis. However, there are clinical and immunopathologic distinctions that have led to the recognition of LABD as a separate entity. This review will focus on the clinical manifestations, the etiopathogenesis, as well as the management of LABD, based on the best data available at the time of preparation.

Circulating antibodies directed against “polycyclic aromatic hydrocarbon-like” structures in the sera of cancer patients

Background: An increase in immunoglobulin (Ig) A isotype directed against benzo(a)pyrene (BP) structure has previously been described in sera of cancer patients. In this study, new polycyclic aromatic hydrocarbon (PAH) conjugates were synthesized in order to more closely mimic the endogenous ligands of the cytosolic aryl hydrocarbon receptor (AhR). PAH [benzo(a)pyrene; 1,2-benzanthracene; dibenz[a,c]anthracene; 7,12-dimethylbenza[a]anthracene; benzo(ghi)perylene] were bound to protein carriers such as bovine serum albumin (BSA) via N-acetyl-cysteine (NAC). Methods: The levels of circulating antibodies (Abs) directed against PAH–NAC conjugates in the sera of cancer patients were evaluated using an Enzyme-Linked Immunosorbent Assay (ELISA) with these new conjugates. The avidity (IC 50) and specificity of these circulating Abs were assessed via competition experiments. Results: An increase in Ig directed against these PAH–NAC conjugates was found in the sera of cancer patients, irrespective of the state and stage of the tumors. These Ig were principally of the A isotype. Sera from cancer patients had significantly higher optical density (OD) ranges than the controls, p < 0.0001. The ELISA test for breast cancer ( n = 155) and ovarian cancer ( n = 62) identified 82% and 92% of positive patients, respectively. The percentage positive in the control group ( n = 60) was around 5%. Moreover, competition experiments with the different PAH–NAC conjugates and NAC–BSA revealed an estimated avidity of 10 −6 M for the circulating IgA antibodies. Conclusions: The Abs discriminated between the different PAH–NAC conjugates and NAC–BSA. Therefore, these Abs recognize a carcinogenic PAH–NAC structure and not only a BP structure. These markers may be useful in the future for monitoring cancer evolution and recurrence.

Autoantibodies against epidermal transglutaminase are a sensitive diagnostic marker in patients with dermatitis herpetiformis on a normal or gluten-free diet

Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate circulating IgA antibodies against epidermal transglutaminase (eTG) and tissue transglutaminase (tTG). It has been suggested that eTG is the autoantigen of DH. The purpose of this study was to characterize the autoimmune response to eTG and tTG in patients with DH on a normal or gluten-free diet (GFD). Sera from 52 patients with DH were studied for the presence of IgA antibodies to eTG and tTG by enzyme-linked immunosorbant assay. In 38 patients, serum was obtained before initiation of a GFD, whereas 14 patients had been on a GFD for at least 2 years. Autoantibodies against eTG were detected in 36 of 38 patients (95%) and those against tTG in 30 of 38 patients (79%) with DH on a normal diet. Of 14 patients on a long-term GFD, 7 patients were free of DH lesions and did not require dapsone treatment. None of these patients showed circulating antibodies against eTG or tTG. The remaining 7 patients on a GFD were not able to stop taking dapsone. All these patients demonstrated anti-eTG antibodies, whereas only 3 of them showed additional reactivity against tTG. Autoantibody levels against eTG and tTG before and after introduction of a GFD were not examined in the same patients. Our data suggest that antibodies to eTG are the most sensitive serologic marker in treated and untreated patients with DH and confirm the central role of eTG in the pathogenesis of this disease.

Susceptibility to Vibrio cholerae Infection in a Cohort of Household Contacts of Patients with Cholera in Bangladesh

BackgroundDespite recent progress in understanding the molecular basis of Vibrio cholerae pathogenesis, there is relatively little knowledge of the factors that determine the variability in human susceptibility to V. cholerae infection.Methods and FindingsWe performed an observational study of a cohort of household contacts of cholera patients in Bangladesh, and compared the baseline characteristics of household members who went on to develop culture-positive V. cholerae infection with individuals who did not develop infection. Although the vibriocidal antibody is the only previously described immunologic marker associated with protection from V. cholerae infection, we found that levels of serum IgA specific to three V. cholerae antigens—the B subunit of cholera toxin, lipopolysaccharide, and TcpA, the major component of the toxin–co-regulated pilus—also predicted protection in household contacts of patients infected with V. cholerae O1, the current predominant cause of cholera. Circulating IgA antibodies to TcpA were also associated with protection from V. cholerae O139 infection. In contrast, there was no association between serum IgG antibodies specific to these three antigens and protection from infection with either serogroup. We also found evidence that host genetic characteristics and serum retinol levels modify susceptibility to V. cholerae infection.ConclusionsOur observation that levels of serum IgA (but not serum IgG) directed at certain V. cholerae antigens are associated with protection from infection underscores the need to better understand anti–V. cholerae immunity at the mucosal surface. Furthermore, our data suggest that susceptibility to V. cholerae infection is determined by a combination of immunologic, nutritional, and genetic characteristics; additional factors that influence susceptibility to cholera remain unidentified.

Antiphospholipid Antibodies in Patients with Small-Vessel Vasculitis

The definition of adult Henoch-Schonlein purpura (HSP) is controversial, and the role of IgA antibodies in the pathogenesis of this disease is not fully established. Most classification systems do not include measures of circulating IgA antibodies or tissue-bound IgA in the disease definition. Nor has the presence of IgA been shown …

The localization of the target antigens and antibodies in linear IgA disease is heterogeneous, and dependent on the methods used.

Fifty-nine patients with linear IgA disease, 24 with onset in childhood and 35 with adult onset, were studied. Sera from all patients were tested by indirect immunofluorescence, using as substrates intact normal skin and normal skin which had been split through the lamina lucida region of the basement membrane zone by suction and by prolonged incubation with molar NaCl. This enabled the site of the target antigen for the circulating IgA antibodies to be determined. The sites of deposition of the IgA antibodies in vivo were detected by raising a suction blister in eight patients, and splitting seven patients' biopsies by prolonged incubation with molar NaCl. Eighteen sera were positive with intact skin, and 34 with split skin. Twenty-nine sera were positive with suction blisters as substrate; 14 bound to the epidermal aspect of the split skin, seven in a combined pattern (binding to the epidermis and dermis) and six to the dermal aspect. Thirty-one sera bound to salt-split skin, 24 to the epidermal side and seven on the dermal side. There was discordance between the two methods of skin splitting in 15 sera. Seven sera gave a combined pattern with suction but with salt-split skin, five of these bound epidermally, one was dermal, and one negative. Five sera showed epidermal binding on salt-split skin and were negative on suction blisters, and the reverse was seen with one serum. Two sera gave variable results on suction blisters. Direct immunofluorescence studies showed dermal binding on all eight patients with suction blisters, and epidermal binding in four and dermal binding in three patients with salt splitting.(ABSTRACT TRUNCATED AT 250 WORDS)

Inflammatory epidermolysis bullosa acquisita with coexistent IgA antibodies to plectin

We present a case of inflammatory epidermolysis bullosa acquisita (EBA) with IgA antibodies to plectin. Analysis of lesional skin biopsies by electron microscopy revealed the split level to be in the sublamina densa zone, corresponding to the diagnosis of EBA. Direct immunofluorescence of perilesional skin demonstrated u-serrated depositions of IgG and IgA that under immunoelectron microscopy were shown to be located in the sublamina densa. In contrast, indirect immunofluorescence on salt-split skin revealed circulating IgA antibodies that stained the roof rather than the floor of the blister. Immunoblotting showed these serum antibodies to be directed to the cytoplasmic hemidesmosomal antigen plectin. The antiplectin specificity of these antibodies was confirmed by 'knockout' immunofluorescence analysis; the serum IgA did not bind to skin sections of a patient with plectin-deficient epidermolysis bullosa. To our knowledge, this case demonstrates for the first time the existence of IgA antibodies against plectin.

Recurrent Goodpasture’s disease secondary to a monoclonal IgA1-κ antibody autoreactive with the α1/α2 chains of type IV collagen

Goodpasture's disease is characterized by crescentic glomerulonephritis and lung hemorrhage in the presence of anti-glomerular basement membrane (anti-GBM) antibodies. This disease usually is mediated by IgG autoantibodies directed against the noncollagenous domain of the alpha3(IV) collagen chain, the Goodpasture autoantigen. In rare cases, anti-GBM antibodies of IgA or IgM class are involved, but their specificity has not been determined, and their target antigen remains unknown. The authors present the case of a 62-year-old man with anti-GBM disease mediated by a monoclonal IgA-kappa antibody, which progressed to end-stage renal disease despite intensive immunosuppression. The patient underwent living-related kidney transplantation, but lung hemorrhage and crescentic glomerulonephritis recurred, causing the loss of the allograft 2 years later. Indirect immunofluorescence found the presence of circulating IgA antibodies reactive with a basement membrane component, identified by enzyme-linked immunoabsorbent assay and Western blot as the alpha1/alpha2(IV) collagen chains. Sensitivity to digestion with collagenase indicated that IgA bound to epitopes located in the collagenous domain. This is the first case of recurrent Goodpasture's disease secondary to an autoreactive IgA antibody. The specificity of an IgA antibody implicated in the pathogenesis of anti-GBM disease has been investigated for the first time, identifying the alpha1/alpha2(IV) collagen chains as a novel target for nephritogenic antibodies.

Frequency of IgA antibodies in pemphigus, bullous pemphigoid and mucous membrane pemphigoid.

Circulating and bound IgA antibodies can be found in the autoimmune blistering diseases, but their prevalence, clinical relevance and target antigens remain unknown. Thirty-two patients with pemphigus, 73 with bullous pemphigoid and 28 with mucous membrane pemphigoid were studied retrospectively. Direct immunofluorescence (DIF) analysis of IgG, IgA, IgM and C3 was carried out for all cases. Sera were studied by standard indirect immunofluorescence, indirect immunofluorescence on salt-split skin, immunoblotting for bullous pemphigoid and mucous membrane pemphigoid and ELISA for pemphigus. With DIF, we found IgA autoantibodies in 22 of all 133 cases. Circulating IgA antibodies to skin were detected in 2 of 3 IgA-DIF-positive patients with pemphigus, in 3 of 6 with bullous pemphigoid, and in 6 of 13 with mucous membrane pemphigoid. We confirm that the IgA reactivity is more frequently associated with mucous membrane involvement, especially in cases without critical involvement (5/8). The role of IgA and its antigenic specificity in these diseases remain unclear.