Neutrophil extracellular traps (NETs) are web-like structures extruded by neutrophils after activation or in response to microorganisms. These extracellular structures are decondensed chromatin fibers loaded with antimicrobial granular proteins, peptides, and enzymes. NETs clear microorganisms, thus keeping a check on infections at an early stage, but if dysregulated, may be self-destructive to the body. Indeed, NETs have been associated with autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), antiphospholipid syndrome (APS), psoriasis, and gout. More recently, increased NETs associate with COVID-19 disease severity. While there are rigorous and reliable methods to quantify NETs from neutrophils via flow cytometry and immunofluorescence, the accurate quantification of NETs in patient plasma or serum remains a challenge. Here, we developed new methodologies for the quantification of NETs in patient plasma using multiplex ELISA and immunofluorescence methodology. Plasma from patients with SLE, non-genotyped healthy controls, and genotyped healthy controls that carry either the homozygous risk or non-risk IRF5-SLE haplotype were used in this study. The multiplex ELISA using antibodies detecting myeloperoxidase (MPO), citrullinated histone H3 (CitH3) and DNA provided reliable detection of NETs in plasma samples from SLE patients and healthy donors that carry IRF5 genetic risk. An immunofluorescence smear assay that utilizes only 1 µl of patient plasma provided similar results and data correlate to multiplex ELISA findings. The immunofluorescence smear assay is a relatively simple, inexpensive, and quantifiable method of NET detection for small volumes of patient plasma.
BackgroundCancer-testis (CT) genes are targets for tumor antigen-specific immunotherapy given that their expression is normally restricted to the immune-privileged testis in healthy individuals with aberrant expression in tumor tissues. While they represent targetable germ-tissue antigens and play important functional roles in tumorigenesis, there is currently no standardized approach for identifying clinically relevant CT genes. Optimized algorithms and validated methods for accurate prediction of reliable CT antigens with high immunogenicity are also lacking.MethodsSequencing data from the Genotype-Tissue Expression (GTEx) and The Genomic Data Commons (GDC) databases was utilized for the development of a bioinformatic pipeline to identify CT exclusive genes. A CT germness score was calculated based on the number of CT genes expressed within a tumor type and their degree of expression. The impact of tumor germness with clinical outcome was evaluated using healthy GTEx and GDC tumor samples. We then used a triple-negative breast cancer mouse model to develop and test an algorithm that predicts epitope immunogenicity based on the identification of germline sequences with strong MHCI and MHCII binding affinities. Germline sequences for CT genes were synthesized as long synthetic peptide vaccines and tested in the 4T1 triple-negative model of invasive breast cancer with Poly(I:C) adjuvant. Vaccine immunogenicity was determined by flow cytometric analysis ofin vitroandin vivoT cell responses. Primary tumor growth and lung metastasis was evaluated by histopathology, flow cytometry and colony formation assay.ResultsWe developed a new bioinformatic pipeline to reliably identify CT exclusive genes as immunogenic targets for immunotherapy. We identified CT genes that are exclusively expressed within the testis, lack detectable thymic expression, and are significantly expressed in multiple tumor types. High tumor germness correlated with tumor progression but not with tumor mutation burden, supporting CT antigens as appealing targets in low mutation burden tumors. Importantly, tumor germness also correlated with markers of anti-tumor immunity. Vaccination of 4T1 tumor bearing mice with Siglece and Lin28a antigens resulted in increased T cell anti-tumor immunity and reduced primary tumor growth and lung metastases.ConclusionOur results present a novel strategy for the identification of highly immunogenic CT antigens for the development of targeted vaccines that induce anti-tumor immunity and inhibit metastasis.
SLE is a complex multifactorial autoimmune disease characterized by high levels of autoantibodies that impact many organs. Neutrophil extracellular traps (NETs) are a potential source of antigen leading to the production of autoantibodies, as antibodies against NET components are detected in SLE patients. Higher level of NETs and decreased clearance of NETs are associated with SLE and other autoimmune diseases. Neutrophils play an key role in pediatric lupus and NETs from pediatric lupus patients activate plasmacytoid dendritic cells (pDCs) to produce high levels of IFN-α. Polymorphisms within and around the IRF5 gene associate with risk of developing SLE. We previously reported that healthy donor neutrophils from IRF5 homozygous risk carriers underwent increased spontaneous NETosis, as compared to non-risk donors, that resulted in increased IFN-α production, plasma cell differentiation and autoantibody production. Whether the observed increase in neutrophil-mediated ETosis is a systemic signature of IRF5-driven pre-symptomatic SLE is not known, nor is it known whether these IRF5 risk carriers have defects in NET clearance. We thus developed and optimized new assays to detect small quantities of NET remnants in plasma samples using a combined MPO-CitH3 antibody cocktail followed by detection of DNA by ELISA. Further, we designed a novel immunofluorescence technique to visualize and quantify plasma NETs in healthy donor risk and non-risk carriers, as compared to pediatric and adult SLE patients. In addition, plasma DNase 1 and DNase 1L3 levels were measured. This study will report on the mechanisms by which circulating NETs are increased in pediatric and adult SLE, as well as the contribution of IRF5 genetic risk to NET clearance. Supported by Lupus Research Alliance Department of Defense CDMRP LRP W81XWH-18-1-0674
Neutrophil extracellular traps (NETs) are web-like structures made up of decondensed chromatin fibers along with neutrophil granular proteins that are extruded by neutrophils after activation or in response to foreign microorganisms. NETs have been associated with autoimmune and inflammatory diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, coronavirus disease 2019 (COVID-19), and others. There are reliable methods available to quantitate NETs from neutrophils, but their accurate quantification in patient plasma or serum remains a challenge. We developed a highly sensitive ELISA to detect NETs in serum/plasma and designed a novel smear immunofluorescence assay to detect NETs in as little as 1 μL of serum/plasma. We further validated our technology on plasma samples from SLE patients and healthy donors that carry interferon regulatory factor 5 genetic risk. The multiplex ELISA combines the use of three antibodies against myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and DNA to detect the NET complexes with higher specificities. The immunofluorescence smear assay can visually detect intact structures of NETs in 1 μL of serum/plasma and provide similar results that correlate with findings from the multiplex ELISA. Furthermore, the smear assay is a relatively simple, inexpensive, and quantifiable method of NET detection for small volumes.
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