Molecular recognition of a single-chain Fv antibody specific for GA-pyridine, an advanced glycation end-product (AGE), elucidated using biophysical techniques and synthetic antigen analogues.

Advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed by non-enzymatic reaction between reducing-sugar and Arg/Lys in proteins and are involved in various diabetic complications. GA-pyridine is derived from glycolaldehyde and is one of the most cytotoxic AGEs. Here, we established a single-chain Fv (scFv) antibody against GA-pyridine, 73MuL9-scFv, and examined the details of its specificity and antigen recognition by using various techniques involving biophysics, chemical biology and structural biology. We also synthesized several compounds that differ slightly in regard to the position and number of GA-pyridine substituent groups, and revealed that GA-pyridine was specifically bound to 73MuL9-scFv. Thermodynamic analysis revealed that the association of GA-pyridine to 73MuL9-scFv was an exothermic and enthalpy driven reaction, and thus that the antigen recognition involved multiple specific interactions. Crystallographic analysis of the Fv fragment of 73MuL9-scFv revealed that several CH-π and hydrogen bond interactions took place between the Fv-fragment and GA-pyridine, which was consistent with the results of thermodynamic analysis. Further studies using 73MuL9-scFv as a tool to clarify the relevance of GA-pyridine to diabetic complications are warranted.

Alcohol Consumption in Rheumatoid Arthritis: A Path through the Immune System.

Benefits and harms of different components of human diet have been known for hundreds of years. Alcohol is one the highest consumed, abused, and addictive substances worldwide. Consequences of alcohol abuse are increased risks for diseases of the cardiovascular system, liver, and nervous system, as well as reduced immune system function. Paradoxically, alcohol has also been a consistent protective factor against the development of autoimmune diseases such as type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis (RA). Here, we focused on summarizing current findings on the effects of alcohol, as well as of its metabolites, acetaldehyde and acetate, on the immune system and RA. Heavy or moderate alcohol consumption can affect intestinal barrier integrity, as well as the microbiome, possibly contributing to RA. Additionally, systemic increase in acetate negatively affects humoral immune response, diminishing TFH cell as well as professional antigen-presenting cell (APC) function. Hence, alcohol consumption has profound effects on the efficacy of vaccinations, but also elicits protection against autoimmune diseases. The mechanism of alcohol's negative effects on the immune system is multivariate. Future studies addressing alcohol and its metabolite acetate's effect on individual components of the immune system remains crucial for our understanding and development of novel therapeutic pathways.

Associations between an expanded autoantibody profile and treatment responses to biologic therapies in patients with rheumatoid arthritis.

BACKGROUND: Although biologics represent a major advance in rheumatoid arthritis (RA), many patients fail to achieve adequate responses to these agents. We examined whether combined positivity to three well-characterized autoantibodies predicts treatment response among RA patients initiating biologics. METHODS: The study included biologic-naïve patients initiating anti-TNF treatment, biologic-exposed patients switching to rituximab or tocilizumab, and patients (biologic naïve or exposed) initiating abatacept. Rheumatoid factor (RF), anti-cyclic citrullinated peptide (CCP) antibody, and IgG antibodies to malondialdehyde-acetaldehyde (MAA) were measured using banked enrollment serum. The relationship between the number of autoantibodies positive (0-3) and treatment response (absolute improvement in 28-joint Disease Activity Score [DAS28-CRP] or improvement > 1.2) at 6 months was examined using multivariable linear and logistic regression. RESULTS: Of 1,229 patients initiating biologics, 79% were women; 89% were Caucasian. The number of baseline RA-related autoantibodies positive was associated with improved treatment response in a dose-dependent fashion. Compared to patients seronegative for all autoantibodies, adjusting for covariates, those positive for all three were more than twice (OR 2.35; 95% CI 1.57-3.51) as likely to achieve DAS28 improvement > 1.2 units. Associations of autoantibody positivity with biologic treatment response were strongest for anti-CCP antibody, persisted in analyses limited to biologic naïve patients, and did not appear to differ markedly among different agents examined. CONCLUSION: An expanded autoantibody profile appears to significantly predict RA treatment response to biologic treatment in a dose-dependent fashion. Incorporating these serologic profiles with additional biomarkers or other informative patient characteristics could provide an opportunity to personalize RA management.

Autoantibodies to Malondialdehyde-Acetaldehyde Are Detected Prior to Rheumatoid Arthritis Diagnosis and After Other Disease Specific Autoantibodies.

OBJECTIVE: To examine serum autoantibodies to malondialdehyde-acetaldehyde (MAA) prior to rheumatoid arthritis (RA) diagnosis. METHODS: Concentrations of anti-MAA antibody isotypes, anti-cyclic citrullinated peptide 2 (anti-CCP-2), and IgM rheumatoid factor (IgM-RF) were evaluated before and after RA diagnosis in samples from cases (n = 214) and controls (n = 210). The timing of elevations in autoantibody concentrations relative to RA diagnosis was explored using separate mixed models for each antibody and/or isotype. Associations between prediagnosis autoantibody concentrations in RA patients were examined using mixed effects linear regression models. RESULTS: Concentrations of IgG (log2 difference 0.34) and IgA (log2 difference 0.43) anti-MAA antibodies in RA patients diverged from controls at 3.0 years and 2.3 years prior to diagnosis, respectively (P < 0.05 for both). There was no evidence of case-control divergence for IgM anti-MAA antibody concentration. Anti-CCP-2 and IgM-RF concentrations diverged between RA patients and controls beginning at 17.6 years and 7.2 years prior to RA diagnosis, respectively. All 3 anti-MAA antibody isotypes (IgA, IgM, and IgG) were significantly associated with anti-CCP-2 antibody and RF concentrations prior to diagnosis (ß = 0.22-0.27 for IgM-RF; ß = 0.44-0.93 for anti-CCP-2) (P < 0.001). CONCLUSION: IgG and IgA anti-MAA autoantibodies are elevated prior to RA diagnosis but appear later in the preclinical course than anti-CCP-2 or RF. These findings suggest that MAA formation and anti-MAA immune responses could play a role in the transition from subclinical autoimmunity to clinically apparent arthritis.

Immunogenic and inflammatory responses to citrullinated proteins are enhanced following modification with malondialdehyde-acetaldehyde adducts.

BACKGROUND/OBJECTIVE: Malondialdehyde-acetaldehyde adducts (MAA) act as potent immune adjuvants and co-localize with citrullinated antigens in tissues effected by rheumatoid arthritis (RA). We sought to examine the role of MAA-adducts in promoting RA-related autoimmunity and inflammation. METHODS: DBA/J1 mice were immunized with human serum albumin (HSA), HSA-MAA, citrullinated HSA (HSA-Cit), or HSA-MAA-Cit with subsequent measurement of serum anti-citrullinated protein antibody (ACPA) and anti-Cit T cell responses. Cellular binding of the same antigens was examined using THP-1 monocytes and Chinese Hamster Ovary (CHO) cells transfected with specific scavenger receptors (SRs: TLR4, SR-B2, SREC-1). The effects of these antigens on THP-1 activation were then examined by quantifying plate adherence, pro-inflammatory (TNFα, IL-1ß, IL-10) cytokine release, and SR (CD14, SR-B2)/co-stimulatory molecule (CD80, HLA-DR) expression. Comparisons were completed using one-way ANOVA with Tukey's post-hoc test. RESULTS: Mice immunized with co-modified HSA produced significantly higher ACPA concentrations than all other groups whereas T cell responses to citrullinated proteins were highest following immunization with HSA-MAA. Both transfected CHO and THP-1 cells demonstrated significantly higher binding of HSA-MAA-Cit vs. HSA or HSA-Cit. THP-1 cells exposed to HSA-MAA-Cit expressed significantly higher concentrations of TNFα, IL-1ß, and IL-10 vs. all other groups. Furthermore, THP-1 cells demonstrated significantly increased plate adherence and higher expression of CD14, SR-B2, and HLA-DR following incubation with HSA-MAA-Cit vs. HSA or HSA-Cit. CONCLUSION: These studies demonstrate that MAA-adduction of citrullinated antigen greatly enhances immune and cellular responses, potentially acting as a key co-factor in RA pathogenesis.

Convenient method of producing cyclic single-chain Fv antibodies by split-intein-mediated protein ligation and chaperone co-expression.

Single-chain Fv (scFv) is a recombinant antibody in which the variable regions of the heavy chain (VH) and light chain (VL) are connected by a short flexible polypeptide linker. Compared with monoclonal antibodies, scFvs have the advantages of low-cost production using Escherichia coli and easy genetic manipulation. ScFvs are, therefore, regarded as useful modules for producing next-generation medical antibodies. The practical use of scFvs has been limited due to their aggregation propensity mediated by interchain VH-VL interactions. To overcome this problem, we recently reported a cyclic scFv whose N-terminus and C-terminus were connected by sortase A-mediated ligation. Preparation of cyclic scFv is, however, a time-consuming process. To accelerate the application study of cyclic scFv, we developed a method to produce cyclic scFv by the combined use of a protein ligation technique based on protein trans-splicing reaction (PTS) by split intein and a chaperone co-expression system. This method allows for the preparation of active cyclic scFv from the cytoplasm of E. coli. The present method was applied to the production of cyclic 73MuL9-scFv, a GA-pyridine antibody, as a kind of advanced glycation end-product. These findings are expected to evoke further application study of cyclic scFv.

Malondialdehyde-Acetaldehyde Adducts and Antibody Responses in Rheumatoid Arthritis-Associated Interstitial Lung Disease.

OBJECTIVE: To compare serum anti-malondialdehyde-acetaldehyde (anti-MAA) antibody levels and MAA expression in lung tissue from patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD) to those found in controls. METHODS: Anti-MAA antibody (IgA, IgM, IgG) concentrations were measured in patients with RA-ILD and compared to those of RA patients with chronic obstructive pulmonary disease (COPD) and RA patients without lung disease. Associations between anti-MAA antibody with RA-ILD were assessed using multivariable logistic regression. Lung tissue from patients with RA-ILD, other ILD, or emphysema, and from controls (n = 3 per group) were stained for MAA, citrulline, macrophages (CD68), T cells (CD3), B cells (CD19/CD27), and extracellular matrix proteins (type II collagen, fibronectin, vimentin). Tissue expression and colocalization with MAA were quantified and compared. RESULTS: Among 1,823 RA patients, 90 had prevalent RA-ILD. Serum IgA and IgM anti-MAA antibody concentrations were higher in RA-ILD than in RA with COPD or RA alone (P = 0.005). After adjustment for covariates, the highest quartiles of IgA anti-MAA antibody concentration (odds ratio 2.09 [95% confidence interval 1.11-3.90]) and IgM (odds ratio 2.23 [95% confidence interval 1.19-4.15]) were significantly associated with the presence of RA-ILD. MAA expression in RA-ILD lung tissue was greater than in tissue from all other groups (P < 0.001), and it colocalized with citrulline (r = 0.79), CD19+ B cells (r = 0.78), and extracellular matrix proteins (type II collagen [r = 0.72] and vimentin [r = 0.77]) to the greatest degree in RA-ILD. CONCLUSION: Serum IgA and IgM anti-MAA antibody is associated with ILD among RA patients. MAA is highly expressed in RA-ILD lung tissue, where it colocalizes with other RA autoantigens, autoreactive B cells, and extracellular matrix proteins, highlighting its potential role in the pathogenesis of RA-ILD.

Malondialdehyde-acetaldehyde antibody concentrations in rheumatoid arthritis and other rheumatic conditions.

OBJECTIVE: To compare anti-malondialdehyde-acetaldehyde (MAA) antibody concentrations between rheumatoid arthritis (RA) patients and healthy and rheumatic disease controls. METHODS: Anti-MAA antibody (IgA, IgM, IgG) was measured using ELISA and banked serum from patients with RA (n = 284), osteoarthritis (OA, n = 330), spondyloarthropathy (SpA, n = 50), and systemic lupus erythematosus (SLE, n = 88) as well as healthy controls (n = 82). Anti-MAA antibody concentrations and the frequency of positivity were compared across groups. Multivariable linear regression analysis limited to RA and OA patients (due to sample size and data availability) was used to identify factors associated with anti-MAA antibody concentrations. RESULTS: Although RA patients demonstrated among the highest circulating concentrations across isotypes, only IgA anti-MAA antibody was significantly higher than all other groups (p ≤ 0.02). Proportions (7% to 74%) of OA and SLE (less so for SpA) samples were positive for anti-MAA antibody, limiting the discriminatory capacity of anti-MAA antibody in RA (positive in 18% to 80%). In analyses limited to those with RA or OA, factors associated with higher anti-MAA antibody concentrations included RA case status, younger age (IgM), male sex (IgG), African American race (IgA, IgG) and current smoking (IgA). C-reactive protein levels and comorbidities were not associated with anti-MAA antibody concentrations. CONCLUSION: With the possible exception of the IgA isotype, serum anti-MAA antibodies measured with currently available assays do not appear to adequately discriminate RA from other rheumatic conditions. With the identification of specific proteins that are MAA-modified in diseased tissues and requisite assay refinement, anti-MAA antibody holds potential promise as a biomarker in RA.

Liver tissue metabolically transformed by alcohol induces immune recognition of liver self-proteins but not in vivo inflammation.

Precision-cut liver slices (PCLSs) provide a novel model for studies of alcoholic liver disease (ALD). This is relevant, as in vivo ethanol exposure does not appear to generate significant liver damage in ethanol-fed mice, except in the National Institute on Alcohol Abuse and Alcoholism binge model of ALD. Previous studies have shown that the two metabolites of ethanol consumption, malondialdhyde (MDA) and acetaldehyde (AA), combine to form MDA-AA (MAA) adducts, which have been correlated with the development and progression of ALD. In this study, murine PCLSs were incubated with ethanol and examined for the production of MAA adducts. PCLSs were homogenized, and homogenates were injected into C57BL/6 mice. PCLSs from control-, pair-, and ethanol-fed animals served as targets in in situ cytotoxic assays using primed T cells from mice hyperimmunized with control or ethanol-exposed PCLS homogenates. A CD45.1/CD45.2 passive-transfer model was used to determine whether T cells from the spleens of mice hyperimmunized with PCLS ethanol-exposed homogenates trafficked to the liver. PCLSs incubated with ethanol generated MAA-modified proteins in situ. Cytotoxic (CD8+) T cells from immunized mice killed naïve PCLSs from control- and pair-fed mice in vitro, a response that was blunted in PCLSs from ethanol-fed mice. Furthermore, CD45.1 CD8+ T cells from hyperimmunized mice trafficked to the liver but did not initiate liver damage. This study demonstrates that exposure to liver tissue damaged by ethanol mediates robust immune responses to well-characterized alcohol metabolites and native liver proteins in vitro. Moreover, although these proinflammatory T cells traffic to the liver, these responses appear to be dampened in vivo by locally acting pathways. NEW & NOTEWORTHY This study shows that the metabolites of ethanol and lipid breakdown produce malondialdehyde-acetaldehyde adducts in the precision-cut liver slice model system. Additionally, precision-cut liver slices exposed to ethanol and harboring malondialdehyde-acetaldehyde adducts generate liver-specific antibody and T cell responses in the spleens of naïve mice that could traffic to the liver.

Gingival tissue, an extrasynovial source of malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins.

BACKGROUND AND OBJECTIVE: Postranslational modification of proteins can lead to the production of autoantibodies and loss of immune tolerance. This process has been hypothesised to be a critical factor in the pathogenesis of rheumatoid arthritis. The objective of this study was to demonstrate that inflamed human gingival tissue provides an extrasynovial source of malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins all of which are considered to be linked to the development of rheumatoid arthritis. Identification of such modified proteins in inflamed gingiva may explain, in part, how inflammation of the periodontal tissues may influence the development of rheumatoid arthritis. MATERIAL AND METHODS: Gingival biopsies of healthy, mild and moderate periodontitis were triple stained with antibodies against malondialdehyde-acetaldehyde adducts, citrullinated and carbamylated proteins. RESULTS: Assessment of healthy gingival tissue revealed negligible staining for carbamylated, malondialdehyde-acetaldehyde (MAA), or citrullinated proteins. Mild periodontitis was positive for all three modifications. Furthermore, there was an increase in staining intensity for carbamylated, citrullinated and MAA-modified proteins in moderate periodontitis. Negative staining results were observed for the isotype controls. CONCLUSION: This study provides evidence for the presence of citrullinated, carbamylated and MAA adduct modified proteins in inflamed periodontal tissues. The potential for these proteins to play a role in autoimmunity in a multi-system inflammatory syndromic disease model now needs to be determined.

Enrichment of malondialdehyde-acetaldehyde antibody in the rheumatoid arthritis joint.

Objective: To characterize the expression of malondialdehdye-acetaldehyde (MAA) adducts and anti-MAA antibody in articular tissues and serum of patients with RA. Methods: Paired sera and SF were examined from 29 RA and 13 OA patients. Anti-MAA antibody, RF, ACPA and total immunoglobulin were quantified. SF-serum measures were compared within and between disease groups. The presence and co-localization of MAA, citrulline and select leukocyte antigens in RA and OA synovial tissues were examined using immunohistochemistry. Results: Circulating and SF anti-MAA antibody concentrations were higher in RA vs OA by 1.5- to 5-fold. IgG (P < 0.001), IgM (P = 0.006) and IgA (P = 0.036) anti-MAA antibodies were higher in paired RA SF than serum, differences not observed for total immunoglobulin, RF or ACPA. In RA synovial tissues, co-localization of MAA with citrulline and CD19+ or CD27+ B cells was demonstrated and was much higher in magnitude than MAA or citrulline co-localization with T cells, monocytes, macrophages or dendritic cells (P < 0.01). Conclusion: Anti-MAA antibodies are present in higher concentrations in the RA joint compared with sera, a finding not observed for other disease-related autoantibodies. Co-localization of MAA and citrulline with mature B cells, coupled with the local enrichment of anti-MAA immune responses, implicates MAA-adduct formation in local autoantibody production.

A purified MAA-based ELISA is a useful tool for determining anti-MAA antibody titer with high sensitivity.

Atherosclerosis is widely accepted to be a chronic inflammatory disease, and the immunological response to the accumulation of LDL is believed to play a critical role in the development of this disease. 1,4-Dihydropyridine-type MAA-adducted LDL has been implicated in atherosclerosis. Here, we have demonstrated that pure MAA-modified residues can be chemically conjugated to large proteins without by-product contamination. Using this pure antigen, we established a purified MAA-ELISA, with which a marked increase in anti-MAA antibody titer was determined at a very early stage of atherosclerosis in 3-month ApoE-/- mice fed with a normal diet. Our methods of Nε-MAA-L-lysine purification and purified antigen-based ELISA will be easily applicable for biomarker-based detection of early stage atherosclerosis in patients, as well as for the development of an adduct-specific Liquid Chromatography/Mass Spectrometry-based quantification of physiological and pathological levels of MAA.

Antibodies against malondialdehyde-acetaldehyde adducts can help identify patients with abdominal aortic aneurysm.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a pathologic dilation of the aorta. Inflammation of the aortic wall has been shown to be involved in AAA formation. Malondialdehyde-acetaldehyde (MAA) adducts are MAA/protein hybrids with immunogenic, proinflammatory, and profibrotic properties. Levels of MAA adducts are elevated in patients with coronary artery disease; however, the role of MAA adducts in AAA is unclear. We hypothesize that levels of circulating antibodies against MAA adducts are increased in patients with AAA. METHODS: Plasma samples were collected from mice and patients with AAA and control patients with atherosclerosis but not AAA. AAA was induced in mice by a standard CaCl2 protocol, with matching sham mice. Plasma levels of anti-MAA antibodies were quantified by enzyme-linked immunosorbent assay. RESULTS: Patients with AAA exhibited higher levels of immunoglobulin G and immunoglobulin A anti-MAA antibody subtypes (P = .049 and .026, respectively) compared with control patients. Conversely, immunoglobulin M anti-MAA antibodies in AAA patients were lower compared with control patients (P = .018). In CaCl2-treated mice, immunoglobulin G anti-MAA antibodies were elevated after AAA formation (P = .006). CONCLUSIONS: The pattern of anti-MAA antibodies is able to distinguish between patients with AAA and patients with atherosclerosis but no AAA. These results demonstrate that MAA adducts are associated with AAA and suggest that they may play a role in either initiating or propagating chronic inflammation in AAA.

Malondialdehyde-acetaldehyde adducts and anti-malondialdehyde-acetaldehyde antibodies in rheumatoid arthritis.

OBJECTIVE: Malondialdehyde-acetaldehyde (MAA) adducts are a product of oxidative stress associated with tolerance loss in several disease states. This study was undertaken to investigate the presence of MAA adducts and circulating anti-MAA antibodies in patients with rheumatoid arthritis (RA). METHODS: Synovial tissue from patients with RA and patients with osteoarthritis (OA) were examined for the presence of MAA-modified and citrullinated proteins. Anti-MAA antibody isotypes were measured in RA patients (n = 1,720) and healthy controls (n = 80) by enzyme-linked immunosorbent assay. Antigen-specific anti-citrullinated protein antibodies (ACPAs) were measured in RA patients using a multiplex antigen array. Anti-MAA isotype concentrations were compared in a subset of RA patients (n = 80) and matched healthy controls (n = 80). Associations of anti-MAA antibody isotypes with disease characteristics, including ACPA positivity, were examined in all RA patients. RESULTS: Expression of MAA adducts was increased in RA synovial tissue compared to OA synovial tissue, and colocalization with citrullinated proteins was found. Increased levels of anti-MAA antibody isotypes were observed in RA patients compared to controls (P < 0.001). Among RA patients, anti-MAA antibody isotypes were associated with seropositivity for ACPAs and rheumatoid factor (P < 0.001) in addition to select measures of disease activity. Higher anti-MAA antibody concentrations were associated with a greater number of positive antigen-specific ACPA analytes (expressed at high titer) (P < 0.001) and a higher ACPA score (P < 0.001), independent of other covariates. CONCLUSION: MAA adduct formation is increased in RA and appears to result in robust antibody responses that are strongly associated with ACPAs. These results support speculation that MAA formation may be a cofactor that drives tolerance loss, resulting in the autoimmune responses characteristic of RA.

Unique antibody responses to malondialdehyde-acetaldehyde (MAA)-protein adducts predict coronary artery disease.

Malondialdehyde-acetaldehyde adducts (MAA) have been implicated in atherosclerosis. The purpose of this study was to investigate the role of MAA in atherosclerotic disease. Serum samples from controls (n = 82) and patients with; non-obstructive coronary artery disease (CAD), (n = 40), acute myocardial infarction (AMI) (n = 42), or coronary artery bypass graft (CABG) surgery due to obstructive multi-vessel CAD (n = 72), were collected and tested for antibody isotypes to MAA-modifed human serum albumin (MAA-HSA). CAD patients had elevated relative levels of IgG and IgA anti-MAA, compared to control patients (p<0.001). AMI patients had a significantly increased relative levels of circulating IgG anti-MAA-HSA antibodies as compared to stable angina (p<0.03) or CABG patients (p<0.003). CABG patients had significantly increased relative levels of circulating IgA anti-MAA-HSA antibodies as compared to non-obstructive CAD (p<0.001) and AMI patients (p<0.001). Additionally, MAA-modified proteins were detected in the tissue of human AMI lesions. In conclusion, the IgM, IgG and IgA anti-MAA-HSA antibody isotypes are differentially and significantly associated with non-obstructive CAD, AMI, or obstructive multi-vessel CAD and may serve as biomarkers of atherosclerotic disease.

Human monoclonal Fab and human plasma antibodies to carbamyl-epitopes cross-react with malondialdehyde-adducts.

Oxidized low-density lipoprotein (OxLDL) plays a crucial role in the development of atherosclerosis. Carbamylated LDL has been suggested to promote atherogenesis in patients with chronic kidney disease. Here we observed that plasma IgG and IgM antibodies to carbamylated epitopes were associated with IgG and IgM antibodies to oxidation-specific epitopes (ρ = 0·65-0·86, P < 0·001) in healthy adults, suggesting a cross-reaction between antibodies recognizing carbamyl-epitopes and malondialdehyde (MDA)/malondialdehyde acetaldehyde (MAA) -adducts. We used a phage display technique to clone a human Fab antibody that bound to carbamylated LDL and other carbamylated proteins. Anti-carbamyl-Fab (Fab106) cross-reacted with oxidation-specific epitopes, especially with MDA-LDL and MAA-LDL. We showed that Fab106 bound to apoptotic Jurkat cells known to contain these oxidation-specific epitopes, and the binding was competed with soluble carbamylated and MDA-/MAA-modified LDL and BSA. In addition, Fab106 was able to block the uptake of carbamyl-LDL and MDA-LDL by macrophages and stained mouse atherosclerotic lesions. The observed cross-reaction between carbamylated and MDA-/MAA-modified LDL and its contribution to enhanced atherogenesis in uraemic patients require further investigation.

Plasma IgA antibody levels to malondialdehyde acetaldehyde-adducts are associated with inflammatory mediators, obesity and type 2 diabetes.

AIM: Obesity and type 2 diabetes (T2D) associate with increased oxidative stress. Malondialdehyde acetaldehyde (MAA) adducts have been suggested to be one of the antigenic epitopes in MDA-LDL responsible for the antibody recognition. Our aim was to investigate the associations between plasma IgA antibodies to MAA-LDL, inflammatory markers, adipokines, obesity, and T2D. METHODS: IgA to MAA-LDL were measured in a subsample (n = 1507) of the Finnish Health 2000 survey. The associations between antibody levels, obesity, TNF-α, IL-6, high-sensitivity (hs) CRP, resistin, adiponectin, fasting plasma (fp) glucose, fp-insulin, glycosylated hemoglobin (Hb-A1C), and T2D were investigated. RESULTS: IgA to MAA-LDL associated positively with fasting plasma insulin. IgA to MAA-LDL were higher among subjects with T2D (P < 0.001) compared to subjects with normal glucose metabolism. IgA to MAA-LDL associated with obesity, but was not independently (P = 0.002, not significant after correction for multiple tests) associated with T2D in logistic regression analysis. IgA to MAA-LDL, obesity, and TNF-α all associated with markers of glucose metabolism. CONCLUSIONS: T2D subjects had increased IgA to MAA-LDL compared to subjects with normal glucose metabolism. The data suggest that the associations between IgA to MAA-LDL and markers of glucose metabolism were independent of TNF-α but dependent on components of the metabolic syndrome.

Natural antibodies of newborns recognize oxidative stress-related malondialdehyde acetaldehyde adducts on apoptotic cells and atherosclerotic plaques.

Malondialdehyde acetaldehyde (MAA) adducts are generated under oxidative stress and shown to be highly immunogenic. Our aim was to investigate the recognition of MAA adducts by human natural antibodies in newborns before or at the time of full-term pregnancy. Plasma samples of pre-term (n = 11) and full-term (n = 36) newborns were enriched in specific IgM binding to MAA adducts compared with the maternal plasma IgM levels. Umbilical cord blood lymphocyte phage display library was generated to clone Fabs that specifically recognized MAA adducts without cross-reactivity to malondialdehyde. Fab clones from the antibody libraries of the pre-term and full-term newborns showed high sequence homology to the germline genes encoding the variable regions of antibodies, confirming that these Fabs represented the natural antibody repertoire of human fetuses. The MAA-specific umbilical cord blood Fabs bound to apoptotic human endothelial cells and the binding was efficiently competed with MAA adducts. The MAA-specific Fabs also recognized epitopes on advanced atherosclerotic lesions, and the uptake of infrared (IR)-labeled MAA-low-density lipoprotein by mouse J774A.1 macrophages was significantly reduced in the presence of these Fabs. In conclusion, MAA adducts were identified as one of the major antigenic targets for human natural antibodies already before the time of birth. MAA-specific natural antibodies are suggested to regulate apoptotic cell clearance starting from fetal development and to participate in the immunomodulation of atherosclerosis development during adulthood.