Lupus autoantibodies to native DNA preferentially bind DNA presented on PolIV

Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

Perinuclear anti-neutrophil cytoplasmic antibody in systemic lupus erythematosus indicates more severe condition

OBJECTIVE

To investigate the clinical significance of perinuclear anti-neutrophil cytoplasmic antibody (p-ANCA) in patients with systemic lupus erythematosus (SLE).

METHODS

This retrospective study included 120 SLE patients. All patients were divided into group p-ANCA+ and group p-ANCA-. Demographic characteristics, clinical symptoms, autoantibodies, laboratory tests and renal pathology were compared between these two groups.

RESULTS

Among 120 patients, 45 (37.5%) patients were p-ANCA+ and 75 (62.5%) patients were p-ANCA-. The occurrence of lupus nephritis was significantly higher in group p-ANCA+ (P = 0.046). For autoantibodies, the occurrences of anti-dsDNA, anti-nucleosome and anti-histone were significantly higher in group p-ANCA+ (P < 0.001, P = 0.004 and P = 0.006, respectively). Titers of anti-dsDNA antibody, erythrocyte sedimentation rate (ESR), serum beta-2-microglobulin (β2-MG) and systemic lupus erythematosus disease activity index (SLEDAI) were higher in group p-ANCA+ (P < 0.001, P = 0.021, P < 0.001 and P = 0.005, respectively), while albumin was significantly lower than p-ANCA- group (P = 0.012). There were no differences in the classification of lupus nephritis, activity index and chronicity index. p-ANCA correlated with lupus nephritis, anti-dsDNA antibody, anti-nucleosome antibody and anti-histone antibody, and also disease activity markers, such as titers of anti-dsDNA antibody, ESR, albumin, serum β2-MG and SLEDAI.

CONCLUSION

The appearance of p-ANCA in SLE indicated high probability of lupus nephritis and more severe condition.

PCR inhibition in qPCR, dPCR and MPS-mechanisms and solutions

DNA analysis has seen an incredible development in terms of instrumentation, assays and applications over the last years. Massively parallel sequencing (MPS) and digital PCR are now broadly applied in research and diagnostics, and quantitative PCR is used for more and more practises. All these techniques are based on in vitro DNA polymerization and fluorescence measurements. A major limitation for successful analysis is the various sample-related substances that interfere with the analysis, i.e. PCR inhibitors. PCR inhibition affects library preparation in MPS analysis and skews quantification in qPCR, and some inhibitors have been found to quench the fluorescence of the applied fluorophores. Here, we provide a deeper understanding of mechanisms of specific PCR inhibitors and how these impact specific analytical techniques. This background knowledge is necessary in order to take full advantage of modern DNA analysis techniques, specifically for analysis of samples with low amounts of template and high amounts of background material. The classical solution to handle PCR inhibition is to purify or dilute DNA extracts, which leads to DNA loss. Applying inhibitor-tolerant DNA polymerases, either single enzymes or blends, provides a more straightforward and powerful solution. This review includes mechanisms of specific PCR inhibitors as well as solutions to the inhibition problem in relation to cutting-edge DNA analysis.

Inhibition mechanisms of hemoglobin, immunoglobulin G, and whole blood in digital and real-time PCR

Blood samples are widely used for PCR-based DNA analysis in fields such as diagnosis of infectious diseases, cancer diagnostics, and forensic genetics. In this study, the mechanisms behind blood-induced PCR inhibition were evaluated by use of whole blood as well as known PCR-inhibitory molecules in both digital PCR and real-time PCR. Also, electrophoretic mobility shift assay was applied to investigate interactions between inhibitory proteins and DNA, and isothermal titration calorimetry was used to directly measure effects on DNA polymerase activity. Whole blood caused a decrease in the number of positive digital PCR reactions, lowered amplification efficiency, and caused severe quenching of the fluorescence of the passive reference dye 6-carboxy-X-rhodamine as well as the double-stranded DNA binding dye EvaGreen. Immunoglobulin G was found to bind to single-stranded genomic DNA, leading to increased quantification cycle values. Hemoglobin affected the DNA polymerase activity and thus lowered the amplification efficiency. Hemoglobin and hematin were shown to be the molecules in blood responsible for the fluorescence quenching. In conclusion, hemoglobin and immunoglobulin G are the two major PCR inhibitors in blood, where the first affects amplification through a direct effect on the DNA polymerase activity and quenches the fluorescence of free dye molecules, and the latter binds to single-stranded genomic DNA, hindering DNA polymerization in the first few PCR cycles. Graphical abstract PCR inhibition mechanisms of hemoglobin and immunoglobulin G (IgG). Cq quantification cycle, dsDNA double-stranded DNA, ssDNA single-stranded DNA.

Increased frequency of circulating follicular helper T cells in lupus patients is associated with autoantibody production in a CD40L-dependent manner

This study was to determine the frequency of circulating follicular helper T (Tfh) cells in patients with systemic lupus erythematosus (SLE) and investigate the relationship between Tfh cells and autoantibody production. An increased frequency of circulating Tfh cells was found in SLE patients, and there were positive co-relationship between Tfh cells and SLEDAI, serum IgG, Anti-nuclear antibody titers and anti-dsDNA (P=0.0004, 0.0006, 0.0237, 0.0000, respectively). B cells sorted from SLE patients produced more IgG than healthy controls in the presence of autologous CD4(+) T cells. CD4(+) T cells were further sorted into CXCR5(+) and CXCR5(-) cells, and CD4(+)CXCR5(+) T cells helped B cells producing more IgG than CD4(+)CXCR5(-) T cells. Blocking the interaction of T cells and B cells by anti-CD40L but not anti-ICOSL dramatically decreased antibody production in the co-culture system. This study suggests that increased frequency of circulating Tfh cells in SLE patients is associated with excess B-cell help and autoantibody production in a CD40L dependent manner.