Autoantibodies to apolipoprotein A-1 as a biomarker of cardiovascular autoimmunity

Leveraging knowledge of HDLs major protein ApoA1: Structure, function, mutations, and potential therapeutics

Apolipoprotein A1 (ApoA1) is a member of the Apolipoprotein family of proteins. It's a vital protein that helps in the production of high-density lipoprotein (HDL) particles, which are crucial for reverse cholesterol transport (RCT). It also has anti-inflammatory, anti-atherogenic, anti-apoptotic, and anti-thrombotic properties. These functions interact to give HDL particles their cardioprotective characteristics. ApoA1 has recently been investigated for its potential role in atherosclerosis, diabetes, neurological diseases, cancer, and certain infectious diseases. Since ApoA1's discovery, numerous mutations have been reported that affect its structural integrity and alter its function. Hence these insights have led to the development of clinically relevant peptides and synthetic reconstituted HDL (rHDL) that mimics the function of ApoA1. As a result, this review has aimed to provide an organized explanation of our understanding of the ApoA1 protein structure and its role in various essential pathways. Furthermore, we have comprehensively reviewed the important ApoA1 mutations (24 mutations) that are reported to be involved in various diseases. Finally, we've focused on the therapeutic potentials of some of the beneficial mutations, small peptides, and synthetic rHDL that are currently being researched or developed, since these will aid in the development of novel therapeutics in the future.

Autoantibodies to Oxidatively Modified Peptide: Potential Clinical Application in Coronary Artery Disease

Coronary artery disease (CAD) is a global health issue. Lipid peroxidation produces various by-products that associate with CAD, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA). The autoantibodies against HNE and MDA-modified peptides may be useful in the diagnosis of CAD. This study included 41 healthy controls (HCs) and 159 CAD patients with stenosis rates of <30%, 30−70%, and >70%. The plasma level of autoantibodies against four different unmodified and HNE-modified peptides were measured in this study, including CFAH1211−1230, HPT78−108, IGKC2−19, and THRB328−345. Furthermore, feature ranking, feature selection, and machine learning models have been utilized to exploit the diagnostic performance. Also, we combined autoantibodies against MDA and HNE-modified peptides to improve the models’ performance. The eXtreme Gradient Boosting (XGBoost) model received a sensitivity of 78.6% and a specificity of 90.4%. Our study demonstrated the combination of autoantibodies against oxidative modification may improve the model performance.

An Autoantigen Atlas From Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. We used DS-affinity proteomics to define the autoantigen-ome of lung fibroblasts and bioinformatics analyses to study the relationship between autoantigenic proteins and COVID-induced alterations. Using DS-affinity, we identified an autoantigen-ome of 408 proteins from human HFL1 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigen-ome have thus far been found to be altered at protein or RNA levels in SARS-CoV-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a connection between COVID infection and autoimmunity. The vast number of COVID-altered proteins with high intrinsic propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles suggests a need for long-term monitoring of autoimmunity in COVID. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic, such as “long COVID” syndrome.

Role of Clinical Characteristics and Biomarkers at Admission to Predict One-Year Mortality in Elderly Patients with Pneumonia

BACKGROUND

A hospitalization for community-acquired pneumonia results in a decrease in long-term survival in elderly patients. We assessed biomarkers at admission to predict one-year mortality in a cohort of elderly patients with pneumonia.

METHODS

A prospective observational study included patients >65 years hospitalized with pneumonia. Assessment of PSI, CURB-65, and biomarkers (C-reactive protein (CRP), procalcitonin (PCT), NT-pro-B-type natriuretic peptide (NT-proBNP), interleukin (IL)-6 and -8, tumor necrosis factor alpha (TNF-α), serum amyloid A (SAA), neopterin (NP), myeloperoxidase (MPO), anti-apolipoprotein A-1 IgG (anti-apoA-1), and anti-phosphorylcholine IgM (anti-PC IgM)) was used to calculate prognostic values for one-year mortality using ROC curve analyses. Post hoc optimal cutoffs with corresponding sensitivity (SE) and specificity (SP) were determined using the Youden index.

RESULTS

A total of 133 patients were included (median age 83 years [IQR: 78-89]). Age, dementia, BMI, NT-proBNP (AUROC 0.65 (95% CI: 0.55-0.77)), and IL-8 (AUROC 0.66 (95% CI: 0.56-0.75)) were significantly associated with mortality, with NT-proBNP (HR 1.01 (95% CI 1.00-1.02) and BMI (HR 0.92 (95% CI 0.85-1.000) being independent of age, gender, comorbidities, and PSI with Cox regression. At the cutoff value of 2200 ng/L, NT-proBNP had 67% sensitivity and 70% specificity. PSI and CURB-65 were not associated with mortality.

CONCLUSIONS

NT-proBNP levels upon admission and BMI displayed the highest prognostic accuracy for one-year mortality and may help clinicians to identify patients with poor long-term prognosis.

A Master Autoantigen-ome Links Alternative Splicing, Female Predilection, and COVID-19 to Autoimmune Diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare but reported adverse effects of the currently available COVID vaccines.

An Autoantigen Atlas from Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. Using DS affinity, we identified an autoantigenome of 408 proteins from human fetal lung fibroblast HFL11 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigenome have thus far been found to be altered at protein or RNA levels in SARS-Cov-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a strong connection between viral infection and autoimmunity. The vast number of COVID-altered proteins with propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles raises concerns about potential adverse effects of mRNA vaccines. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic.

Atherosclerotic plaque vulnerability is increased in mouse model of lupus

Anti-apolipoprotein A-1 (anti-apoA-1 IgG) and anti-double stranded DNA (anti-dsDNA IgG) autoantibodies have been described as mediators of atherogenesis in mice and humans. In the present study, we aim to investigate the association between atherosclerotic parameters, autoantibodies and plaque vulnerability in the context of systemic lupus erythematosus (SLE). We therefore bred a lupus prone-mouse model (Nba2.Yaa mice) with Apoe^−/− mice resulting in Apoe^−/−Nba2.Yaa mice spontaneously producing anti-apoA-1 IgG antibodies. Although Apoe^−/−Nba2.Yaa and Apoe^−/− mice subject to a high cholesterol diet displayed similar atherosclerosis lesions size in aortic roots and abdominal aorta, the levels of macrophage and neutrophil infiltration, collagen, MMP-8 and MMP-9 and pro-MMP-9 expression in Apoe^−/−Nba2.Yaa mice indicated features of atherosclerotic plaque vulnerability. Even though Apoe^−/−Nba2.Yaa mice and Apoe^−/− mice had similar lipid levels, Apoe^−/−Nba2.Yaa mice showed higher anti-apoA-1 and anti-dsDNA IgG levels. Apoe^−/−Nba2.Yaa mice displayed a reduction of the size of the kidney, splenomegaly and lymph nodes (LN) hypertrophy. In addition, anti-apoA-1 and anti-dsDNA IgG increased also in relation with mRNA levels of GATA3, IL-4, Bcl-6 and CD20 in the spleen and aortic arch of Apoe^−/−Nba2.Yaa mice. Our data show that although atherosclerosis-lupus-prone Apoe^−/−Nba2.Yaa mice did not exhibit exacerbated atherosclerotic lesion size, they did show features of atherosclerotic plaque destabilization in correlation with the increase of pro-atherogenic autoantibodies.

Low Level Antibodies Against Alpha-Tropomyosin Are Associated With Increased Risk of Coronary Heart Disease

Objective

Natural autoantibodies have been implicated to play a key role in the pathogenesis of coronary heart disease (CHD) because they augment autoimmune activation. The aim of this study was to identify novel specific autoantibodies of CHD, and analyze the relationship between their levels and CHD risk indicators.

Approach and Results

First, clinical data and sera from CHD patients were collected. Then, one protein microarray containing 37 proteins that represent candidate autoantigens was developed. The arrays were used to profile autoantibodies in randomly selected sera from 35 samples (20 CHD patients, and 15 healthy controls). After that, microarray data were analyzed and autoantibodies for CHD were screened out. Then, ELISA detection was conducted to validate the differentiable autoantibodies using larger numbers of serum samples (131 CHD patients, and 131 healthy controls). Finally, the associations of antibodies with CHD risk indicator parameters were assessed. Inter-group comparison by microarray indicated that three CHD novel autoantibodies, including glucose-6-phosphate isomerase (G6PI), alpha-tropomyosin (TPM1), and heterogeneous nuclear ribonucleoprotein D-like (HnRNPDL), were significantly (P < 0.05) increased when compared with the healthy controls. Moreover, a significant increase of IgG autoantibodies for these three autoantigens was confirmed in CHD patients by ELISA (P < 0.0001). The correction analysis revealed a negative correlation of anti-TPM1 antibody levels and total cholesterol (P = 0.0034), and low-density lipoprotein cholesterol (P = 0.0086), respectively.

Conclusion

G6PI, TPM1, and HnRNPDL were CHD natural autoantigens, and serum anti-TPM1 antibody could be used as a potential marker to predict the risk for CHD patients.

Antibodies towards high-density lipoprotein components in patients with psoriasis

Psoriasis is a chronic inflammatory immune disorder associated with an increased risk of atherosclerosis. This increased risk is not fully understood. High-density lipoproteins (HDL) play an important role in the prevention of atherosclerosis and any factors that may hamper HDL function such as anti-HDL antibodies (aHDL) might be associated with an increased cardiovascular risk. We aimed to determine whether anti-HDL antibodies (aHDL) are present in patients with psoriasis. Sixty-seven patients with psoriasis were compared with a healthy control group. Epidemiologic and clinical data were recorded. IgG and IgM aHDL, IgG anti-apolipoprotein A-I (aApoA-I), anti-apolipoprotein E (aApoE), and anti-paraoxonase 1 (aPON1) antibodies, as well as VCAM-1, IL-6, and TNF-α were assessed by ELISA. Apolipoprotein A-I (ApoA-I) and Apolipoprotein E (ApoE) were measured by immunoturbidimetric immunoassay. Patients with psoriasis had higher titers of IgG aHDL (p < 0.001), IgG aApoA-I (p = 0.001) and aApoE antibodies (p < 0.001). IgG aHDL and aApoE titers were higher in patients with severe psoriasis (p = 0.010 and p = 0.018, respectively). Multiple regression analysis, considering all clinical and biological variables, showed that aApoE, IL-6, and aPON1 are the biological variables that best explain aHDL variability. This is the first report showing the presence of aHDL, aApoA-I, and aApoE antibodies in patients with psoriasis. These antibodies were associated with increased disease severity and may contribute to the pathogenesis of atherosclerosis in psoriasis. They may fulfill the clinical need for biomarkers of cardiovascular risk associated with psoriasis that would help to stratify patients for prevention and therapeutic approaches.

Association of novel biomarkers with major clinical outcomes in a cohort of patients with atherosclerotic renovascular disease

Introduction

In this study, we investigate whether the addition of biomarkers to a model based on traditional risk factors improves risk prediction and patient selection for revascularization in atherosclerotic renovascular disease.

Methods

Patients in the Salford Renovascular Study who had the following biomarkers analysed on a baseline sample were included in this study: FGF-23, Cystatin C, kidney injury molecule-1, myeloperoxidase, neutrophil gelatinase-associated lipocalin, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), high-sensitivity Troponin T and anti-apolipoprotein A1 IgG. Cox proportional hazards models and net reclassification index were used to study the effects of either individual or a panel of biomarkers on predicting death, end-stage kidney disease and cardiovascular events.

Results

A total of 112 patients were followed up for a median 59.9 months (IQR 33.6–86.9). In total, 75 patients died, 21 reached end-stage kidney disease and 36 suffered a cardiovascular event. Only NT-proBNP maintained a statistically significant association with all end-points (death: HR 1.62 [95% CI 1.26–2.10], P < 0.0005; end-stage kidney disease: HR 1.51 [95% 1.19–1.91], P = 0.001; cardiovascular event: HR 1.56 [95% CI 1.23–1.97], P < 0.0005). Risk reclassification improved with addition of all biomarkers as a panel to the base model. Only patients with NT-proBNP concentrations above 300 ng/L gained benefit from revascularization with regard to all adverse end-points compared with medically managed patients.

Conclusions

NT-proBNP is independently associated with increased risk for all adverse events in atherosclerotic renovascular disease. Novel biomarkers may have an incremental risk predictive value when used in combination with traditional risk factors, and NT-proBNP may have value in patient selection for revascularization. Given the small size of this study, larger multicentre studies are required to validate these findings.

ELISA methods comparison for the detection of auto-antibodies against apolipoprotein A1

BACKGROUND

Autoantibodies against apolipoprotein A1 (anti-apoA1 IgG) have emerged as an independent biomarker for cardiovascular disease and mortality. Across studies, different ELISA methods have been used to measure the level of circulating anti-apoA1 IgG which could lead to substantial result differences between assays.

OBJECTIVES

To make a comparative study of available anti-apoA1 IgG detection methods and to determine whether the choice of matrix sample (serum vs plasma) could influence the results.

METHODS

Blood samples were obtained from 160 healthy blood donors and collected on 4 different matrixes (serum, plasma-EDTA, -citrate, -lithium-heparinate). Anti-apoA1 IgG was measured using two homemade (Geneva's and Lisbon's) and one commercial ELISA kits. Passing-Bablok and Bland-Altman were used to compare the results. Anti-apoA1 IgG seropositivity cut-offs were defined according to the user's/manufacturer's criterion.

RESULTS

The current results showed substantial differences between those 3 assays. The dynamic ranges were significantly different, the commercial kit displaying the narrowest one. Passing-Bablok analysis demonstrated important proportional and constant biases between assays. The anti-apoA1 IgG seropositivity rate in Geneva, Lisbon and commercial assays varied between 24.5% and 1.9%. Matrix comparisons demonstrated that the matrix choice (plasma versus serum) influenced anti-apoA1 IgG results as well as the seropositivity rate in an assay-dependent manner. The coating antigen source was identified as important factor underlying results heterogeneity across assays.

CONCLUSIONS

These results highlight the impact of the method and the cut-off used on anti-apoA1 IgG results and emphasize the need of standardizing existing assays. Given the important matrix influence, we suggest to use serum as matrix of choice.

Antibodies Against the C-Terminus of ApoA-1 Are Inversely Associated with Cholesterol Efflux Capacity and HDL Metabolism in Subjects with and without Type 2 Diabetes Mellitus

Background: We determined relationships of cholesterol efflux capacity (CEC), plasma cholesterol esterification (EST) and cholesteryl ester transfer (CET) with anti-c-terminus apoA-1 (Ac-terAA1) and anti-apolipoprotein (apo)-1 (AAA1) autoantibodies in subjects with and without Type 2 diabetes mellitus (T2D). Methods: In 75 T2D subjects and 75 nondiabetic subjects, Ac-terAA1 and AAA1 plasma levels were measured by enzyme-linked immunosorbent assay. CEC was measured as [³H]-cholesterol efflux from human cultured fibroblasts to diluted individual subject plasma. Plasma EST and CET were assayed by isotope methods. Results: Ac-terAA1 and AAA1 levels and were similar between T2D and control subjects. Univariate regression analysis (n = 150) demonstrated that Ac-terAA1 levels were inversely correlated with CEC, EST, CET, total cholesterol, non-HDL cholesterol, triglycerides and apolipoprotein B, (p < 0.05 to p < 0.01), but not with glucose and HbA1c. In separate multivariable linear regression models, CEC, EST and CET were inversely associated with Ac-terAA1 levels independently of age, sex, T2D and drug use (β = −0.186, p = 0.026; β = −0.261, p < 0.001; and β = −0.321, p < 0.001; respectively). These associations were lost after additional adjustment for non-HDL cholesterol and triglycerides. No associations were observed for AAA1. Conclusions: CEC, plasma EST and CET are inversely associated with Ac-terAA1 autoantibodies, conceivably attributable to an inverse relationship of these autoantibodies with apolipoprotein B-containing lipoproteins.

Anti-GRP78 autoantibodies induce endothelial cell activation and accelerate the development of atherosclerotic lesions

The 78-kDa glucose-regulated protein (GRP78) is an ER molecular chaperone that aids in protein folding and secretion. However, pathological conditions that cause ER stress can promote the relocalization of GRP78 to the cell surface (csGRP78), where it acts as a signaling receptor to promote cancer progression. csGRP78 also possesses antigenic properties, leading to the production of anti-GRP78 autoantibodies, which contribute to tumor growth. In contrast, the presence and role of anti-GRP78 autoantibodies in atherosclerosis is unknown. Here, we show that atherosclerotic-prone ApoE-/- mice develop circulating anti-GRP78 autoantibodies that bind to csGRP78 on lesion-resident endothelial cells. Moreover, GRP78-immunized ApoE-/- mice exhibit a marked increase in circulating anti-GRP78 autoantibody titers that correlated with accelerated lesion growth. Mechanistically, engagement of anti-GRP78 autoantibodies with csGRP78 on human endothelial cells activated NF-κB, thereby inducing the expression of ICAM-1 and VCAM-1, a process blocked by NF-κB inhibitors. Disrupting the autoantibody/csGRP78 complex with enoxaparin, a low-molecular-weight heparin, reduced the expression of adhesion molecules and attenuated lesion growth. In conclusion, anti-GRP78 autoantibodies play a crucial role in atherosclerosis development, and disruption of the interaction between anti-GRP78 autoantibodies and csGRP78 represents a therapeutic strategy.

Autoantibody to apolipoprotein A-1 in hepatitis C virus infection: a role in atherosclerosis?

Background/purpose

One to three per cent of the world’s population has hepatitis C virus (HCV) infection, which is not only a major cause of liver disease and cancer but also associated with an increased risk of atherosclerosis, despite an ostensibly favourable lipid profile. Autoantibodies are frequent in HCV infection and emerging evidence shows that autoantibodies could be valuable for cardiovascular disease (CVD) risk stratification. This study investigated a novel independent biomarker of CVD, autoantibodies to apolipoprotein A-1 (anti-apoA-1 IgG) and lipids in patients with chronic HCV before, during and after direct-acting anti-viral (DAA) therapy.

Methods

Eighty-nine blinded serum samples from 27 patients with advanced chronic HCV were assayed for lipids and anti-apoA-1 IgG by ELISA.

Results

Pre-treatment HCV viral load correlated with high-density lipoprotein cholesterol (HDL-C, r = 0.417; p = 0.042) and negatively with apolipoprotein (apo)B (r = − 0.497; p = 0.013) and markers of CVD risk, the apoB/apoA-1 ratio (r = − 0.490; p = 0.015) and triglyceride level (TG)/HDL-C ratio (r = − 0.450; p = 0.031). Fourteen (52%) of 27 patients had detectable anti-apoA-1 IgG autoantibodies pre-treatment; only two became undetectable with virological cure. Autoantibody-positive sera had lower apoA-1 (p = 0.012), HDL-C (p = 0.009) and total cholesterol (p = 0.006) levels.

Conclusions

This is the first report of the presence of an emerging biomarker for atherosclerosis, anti-apoA-1 IgG, in some patients with HCV infection. It may be induced by apoA-1 on the surface of HCV lipoviral particles. The autoantibodies inversely correlate with apoA-1 and HDL levels and may render HDL dysfunctional. Whether these hypothesis-generating findings have clinical implications in HCV patients requires further study.

Review of biomarkers to assess the effects of switching from cigarettes to modified risk tobacco products

Context: One approach to reducing the harm caused by cigarette smoking, at both individual and population level, is to develop, assess and commercialize modified risk alternatives that adult smokers can switch to. Studies to demonstrate the exposure and risk reduction potential of such products generally involve the measuring of biomarkers, of both exposure and effect, sampled in various biological matrices.Objective: In this review, we detail the pros and cons for using several biomarkers as indicators of effects of changing from conventional cigarettes to modified risk products.Materials and methods: English language publications between 2008 and 2017 were retrieved from PubMed using the same search criteria for each of the 25 assessed biomarkers. Nine exclusion criteria were applied to exclude non-relevant publications.Results: A total of 8876 articles were retrieved (of which 7476 were excluded according to the exclusion criteria). The literature indicates that not all assessed biomarkers return to baseline levels following smoking cessation during the study periods but that nine had potential for use in medium to long-term studies.Discussion and conclusion: In clinical studies, it is important to choose biomarkers that show the biological effect of cessation within the duration of the study.

Anti-apolipoprotein A-1 autoantibodies are associated with immunodeficiency and systemic inflammation in HIV patients

OBJECTIVES

To determine the existence of autoantibodies against apolipoprotein A-1 (anti-apoA-1 IgG) in HIV patients and explore their association with biological features of HIV infection and different inflammatory biomarkers. We also evaluated their impact on CD4⁺ lymphocytes survival.

METHODS

Anti-apoA-1 IgG plasma levels were assessed by ELISA in 237 HIV positive patients from a national prospective cohort with no current lipid-lowering therapy.

RESULTS

58% of patients were found positive for anti-apoA-1 IgG and were associated with lower CD4⁺ counts, but higher viremia and systemic inflammation. Logistic regression analyses indicated that high anti-apoA-1 IgG levels were associated with a 16-fold increased risk of displaying low CD4⁺ levels, independent of HIV RNA levels and treatment (adjusted Odds ratio [OR]:16.1, 95% Confidence Interval [95%CI]:1.80-143.6; p = 0.01), and a 6-fold increased risk of having a detectable viremia, independent of antiretroviral treatment (OR:5.47; 95% CI:1.63-18.36; p = 0.006). In vitro, anti-apoA-1 IgG induced dose and time-dependent CD4⁺ apoptosis that was increased by exposure to HIV RNA.

CONCLUSIONS

In HIV patients, anti-apoA-1 IgG levels are associated with low CD4+ counts, high viremia and a pro-inflammatory systemic profile. Anti-apoA-1 IgG can promote CD4+ lymphocyte apoptosis via undefined pathways.

Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes

Glial fibrillary acidic protein (GFAP) is expressed in peri-islet Schwann cells, as well as in glia cells, and has been reported to be an autoantigen candidate for type 1 diabetes mellitus (T1DM). We confirmed that the production of the autoantibodies GFAP and glutamic acid decarboxylase 65 (GAD65) was increased and inversely correlated with the concentration of secreted C peptide in female nonobese diabetic mice (T1DM model). Importantly, the development of T1DM in female nonobese diabetic mice at 30 wk of age was predicted by the positive GFAP autoantibody titer at 17 wk. The production of GFAP and GAD65 autoantibodies was also increased in KK-A^y mice [type 2 diabetes mellitus (T2DM) model]. In patients with diabetes mellitus, GFAP autoantibody levels were increased in patients with either T1DM or T2DM, and were significantly associated with GAD65 autoantibodies but not zinc transporter 8 autoantibodies. Furthermore, we identified a B-cell epitope of GFAP corresponding to the GFAP autoantibody in both mice and patients with diabetes. Thus, these results indicate that autoantibodies against GFAP could serve as a predictive marker for the development of overt autoimmune diabetes.-Pang, Z., Kushiyama, A., Sun, J., Kikuchi, T., Yamazaki, H., Iwamoto, Y., Koriyama, H., Yoshida, S., Shimamura, M., Higuchi, M., Kawano, T., Takami, Y., Rakugi, H., Morishita, R., Nakagumi, H. Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes.

Anti-ApoA-1 IgG serum levels predict worse poststroke outcomes

BACKGROUND

Autoantibodies to apolipoprotein A-1 (anti-ApoA-1 IgG) were shown to predict major adverse cardiovascular events and promote atherogenesis. However, their potential relationship with clinical disability and ischaemic lesion volume after acute ischaemic stroke (AIS) remains unexplored.

MATERIALS AND METHODS

We included n = 76 patients admitted for AIS and we investigated whether baseline serum anti-ApoA-1 IgG levels could predict (i) AIS-induced clinical disability [assessed by the modified Rankin Scale (mRS)], and (ii) AIS-related ischaemic lesion volume [assessed by Computed Tomography (CT)]. We also evaluated the possible pro-apoptotic and pro-necrotic effects of anti-ApoA-1 IgG on human astrocytoma cell line (U251) using flow cytometry.

RESULTS

High levels of anti-ApoA-1 IgG were retrieved in 15·8% (12/76) of patients. Increased baseline levels of anti-ApoA-1 IgG were independently correlated with worse mRS [β = 0·364; P = 0·002; adjusted odds ratio (OR): 1·05 (95% CI 1·01-1·09); P = 0·017] and CT-assessed ischaemic lesion volume [β = 0·333; P < 0·001; adjusted OR: 1·06 (95% CI 1·01-1·12); P = 0·048] at 3 months. No difference in baseline clinical, biochemical and radiological characteristics was observed between patients with high vs. low levels of anti-ApoA-1 IgG. Incubating human astrocytoma cells with anti-ApoA-1 IgG dose dependently induced necrosis and apoptosis of U251 cells in vitro.

CONCLUSION

Anti-ApoA-1 IgG serum levels at AIS onset are associated with poorer clinical recovery and worse brain lesion volume 3 months after AIS. These observations could be partly explained by the deleterious effect of anti-ApoA-1 IgG on human brain cell survival in vitro and may have clinical implication in the prediction of poor outcome in AIS.

ApoA1 and ApoA1-specific self-antibodies in cardiovascular disease

Apolipoprotein A1 (ApoA1) is a main protein moiety in high-density lipoprotein (HDL) particles. Generally, ApoA1 and HDL are considered as atheroprotective. In prooxidant and inflammatory microenvironment in the vicinity to the atherosclerotic lesion, ApoA1/HDL are subjected to modification. The chemical modifications such as oxidation, nitration, etc result in altering native architecture of ApoA1 toward dysfunctionality and abnormality. Neutrophil myeloperoxidase has a prominent role in this mechanism. Neo-epitopes could be formed and then exposed that makes them immunogenic. Indeed, these epitopes may be recognized by immune cells and induce production of proatherogenic ApoA1-specific IgG antibodies. These antibodies are biologically relevant because they are able to react with Toll-like receptor (TLR)-2 and TLR4 in target cells and induce a variety of pro-inflammatory responses. Epidemiological and functional studies underline a prognostic value of ApoA1 self-antibodies for several cardiovascular diseases, including myocardial infarction, acute coronary syndrome, and severe carotid stenosis.

Anti-apolipoprotein A-1 autoantibodies as risk biomarker for cardiovascular diseases in type 2 diabetes mellitus

OBJECTIVE

Anti-Apolipoprotein A-1 autoantibodies (anti-ApoA-1 IgG) represent an emerging prognostic cardiovascular marker in patients with myocardial infarction or autoimmune diseases associated with high thrombotic events. The aim of this work is to investigate the incidence of anti-apoA-1 autoantibodies in type 2 diabetes (T2DM) patients with and without CVD and to study potential association with disease risk and its effect on plasma lipid parameters.

METHODS

Qualitative determination of anti-apoA-1 IgG was assayed in sera from 302 subjects classified into T2DM patients (n=102), T2DM+CVD (n=112) and healthy controls (n=88).

RESULTS

The incidence of anti-apoA-1 IgG was significantly higher among CVD patients (35.7%) than T2DM patients (8.8%) or control subjects (6.1%), p<0.0001. A significant association with CVD was identified (p<0.0001) and subjects who were positive for anti-apoA-1 IgG were at 8.5 times increased risk to develop CVD when compared to controls. Diabetic patients who were positive for the antibodies showed 5.7 times increased CVD risk. ROC analysis indicated anti-apoA-1 IgG as a risk biomarker for CVD in T2DM patients with an AUC value of 0.76, sensitivity of 35.7% and specificity of 91.2%. Studying the effect on lipid parameters, anti-apoA-1 IgG associated with significantly higher serum concentrations of TC and non-HDL-C in all groups and with higher concentrations of LDL-C in diabetic patients and higher TC/HDL-C ratio in CVD patients.

CONCLUSION

Our results indicate that anti-apoA-1 IgG is a cardiovascular risk biomarker in T2DM patients.

CD14 as a Mediator of the Mineralocorticoid Receptor-Dependent Anti-apolipoprotein A-1 IgG Chronotropic Effect on Cardiomyocytes

In vitro and animal studies point to autoantibodies against apolipoprotein A-1 (anti-apoA-1 IgG) as possible mediators of cardiovascular (CV) disease involving several mechanisms such as basal heart rate interference mediated by a mineralocorticoid receptor-dependent L-type calcium channel activation, and a direct pro-inflammatory effect through the engagement of the toll-like receptor (TLR) 2/CD14 complex. Nevertheless, the possible implication of these receptors in the pro-arrhythmogenic effect of anti-apoA-1 antibodies remains elusive. We aimed at determining whether CD14 and TLRs could mediate the anti-apoA-1 IgG chronotropic response in neonatal rat ventricular cardiomyocytes (NRVC). Blocking CD14 suppressed anti-apoA-1 IgG binding to NRVC and the related positive chronotropic response. Anti-apoA-1 IgG alone induced the formation of a TLR2/TLR4/CD14 complex, followed by the phosphorylation of Src, whereas aldosterone alone promoted the phosphorylation of Akt by phosphatidylinositol 3-kinase (PI3K), without affecting the chronotropic response. In the presence of both aldosterone and anti-apoA-1 IgG, the localization of TLR2/TLR4/CD14 was increased in membrane lipid rafts, followed by PI3K and Src activation, leading to an L-type calcium channel-dependent positive chronotropic response. Pharmacological inhibition of the Src pathway led to the decrease of L-type calcium channel activity and abrogated the NRVC chronotropic response. Activation of CD14 seems to be a key regulator of the mineralocorticoid receptor-dependent anti-apoA-1 IgG positive chronotropic effect on NRVCs, involving relocation of the CD14/TLR2/TLR4 complex into lipid rafts followed by PI3K and Src-dependent L-type calcium channel activation.

Impact of systemic inflammation and autoimmune diseases on apoA-I and HDL plasma levels and functions

The cholesterol of high-density lipoproteins (HDLs) and its major proteic component, apoA-I, have been widely investigated as potential predictors of acute cardiovascular (CV) events. In particular, HDL cholesterol levels were shown to be inversely and independently associated with the risk of acute CV diseases in different patient populations, including autoimmune and chronic inflammatory disorders. Some relevant and direct anti-inflammatory activities of HDL have been also recently identified targeting both immune and vascular cell subsets. These studies recently highlighted the improvement of HDL function (instead of circulating levels) as a promising treatment strategy to reduce inflammation and associated CV risk in several diseases, such as systemic lupus erythematosus and rheumatoid arthritis. In these diseases, anti-inflammatory treatments targeting HDL function might improve both disease activity and CV risk. In this narrative review, we will focus on the pathophysiological relevance of HDL and apoA-I levels/functions in different acute and chronic inflammatory pathophysiological conditions.