Antibody responses to DNA in normal immunity and aberrant immunity

DNA Oligonucleotides as Antivirals and Vaccine Constituents against SARS Coronaviruses: A Prospective Tool for Immune System Tuning

The SARS-CoV-2 pandemic has demonstrated the need to create highly effective antivirals and vaccines against various RNA viruses, including SARS coronaviruses. This paper provides a short review of innovative strategies in the development of antivirals and vaccines against SARS coronaviruses, with a focus on antisense antivirals, oligonucleotide adjuvants in vaccines, and oligonucleotide vaccines. Well-developed viral genomic databases create new opportunities for the development of innovative vaccines and antivirals using a post-genomic platform. The most effective vaccines against SARS coronaviruses are those able to form highly effective memory cells for both humoral and cellular immunity. The most effective antivirals need to efficiently stop viral replication without side effects. Oligonucleotide antivirals and vaccines can resist the rapidly changing genomic sequences of SARS coronaviruses using conserved regions of their genomes to generate a long-term immune response. Oligonucleotides have been used as excellent adjuvants for decades, and increasing data show that oligonucleotides could serve as antisense antivirals and antigens in vaccine formulations, becoming a prospective tool for immune system tuning.

Post-genomic platform for development of oligonucleotide vaccines against RNA viruses: diamond cuts diamond

The coronavirus pandemic has starkly demonstrated the need to create highly effective vaccines against various viral diseases. The emerging new platforms for vaccine creation (adenovirus vectors and mRNA vaccines) have shown their worth in the fight against the prevention of coronavirus infection. However, adenovirus vectors and mRNA vaccines have a serious disadvantage: as a rule, only the S protein of the coronavirus is presented as an antigen. This tactic for preventing infection allows the ever-mutating virus to escape quickly from the immunity protection provided by such vaccines. Today, viral genomic databases are well-developed, which makes it possible to create new vaccines on a fundamentally new post-genomic platform. In addition, the technology for the synthesis of nucleic acids is currently experiencing an upsurge in demand in various fields of molecular biology. The accumulated experience suggests that the unique genomic sequences of viruses can act as antigens that trigger powerful humoral and cellular immunity. To achieve this effect, the following conditions must be created: the structure of the nucleic acid must be single-stranded, have a permanent 3D nanostructure, and have a unique sequence absent in the vaccinated organism. Oligonucleotide vaccines are able to resist the rapidly changing genomic sequences of RNA viruses by using conserved regions of their genomes to generate a long-term immune response, acting according to the adage that a diamond cuts a diamond. In addition, oligonucleotide vaccines will not contribute to antibody-dependent enhanced infection, since the nucleic acid of the coronavirus is inside the viral particle. It is obvious that new epidemics and pandemics caused by RNA viruses will continue to arise periodically in the human population. The creation of new, safe, and effective platforms for the production of vaccines that can flexibly change and adapt to new subtypes of viruses is very urgent and at this moment should be considered as a strategically necessary task.

Antibody Complexes

Monoclonal based therapeutics have always been looked at as a futuristic natural way we could take care of pathogens and many diseases. However, in order to develop, establish and realize monoclonal based therapy we need to understand how the immune system contains or kill pathogens. Antibody complexes serve the means to decode this black box. We have discussed examples of antibody complexes both at biochemical and structural levels to understand and appreciate how discoveries in the field of antibody complexes have started to decoded mechanism of viral invasion and create potential vaccine targets against many pathogens. Antibody complexes have made advancement in our knowledge about the molecular interaction between antibody and antigen. It has also led to identification of potent protective monoclonal antibodies. Further use of selective combination of monoclonal antibodies have provided improved protection against deadly diseases. The administration of newly designed and improved immunogen has been used as potential vaccine. Therefore, antibody complexes are important tools to develop new vaccine targets and design an improved combination of monoclonal antibodies for passive immunization or protection with very little or no side effects.

Foot-and-mouth disease vaccines: recent updates and future perspectives

Foot-and-mouth disease (FMD) is a major worldwide viral disease in animals, affecting the national and international trade of livestock and animal products and leading to high economic losses and social consequences. Effective control measures of FMD involve prevention through vaccination with inactivated vaccines. These inactivated vaccines, unfortunately, require short-term protection and cold-chain and high-containment facilities. Major advances and pursuit of hot topics in vaccinology and vectorology are ongoing, involving peptide vaccines, DNA vaccines, live vector vaccines, and novel attenuated vaccines. DIVA capability and marker vaccines are very important in differentiating infected animals from vaccinated animals. This review focuses on updating the research progress of these novel vaccines, summarizing their merits and including ideas for improvement.

Single-Molecule Interactions of a Monoclonal Anti-DNA Antibody with DNA

Interactions of DNA with proteins are essential for key biological processes and have both a fundamental and practical significance. In particular, DNA binding to anti-DNA antibodies is a pathogenic mechanism in autoimmune pathology, such as systemic lupus erythematosus. Here we measured at the single-molecule level binding and forced unbinding of surface-attached DNA and a monoclonal anti-DNA antibody MRL4 from a lupus erythematosus mouse. In optical trap-based force spectroscopy, a microscopic antibodycoated latex bead is trapped by a focused laser beam and repeatedly brought into contact with a DNA-coated surface. After careful discrimination of non-specific interactions, we showed that the DNA-antibody rupture force spectra had two regimes, reflecting formation of weaker (20-40 pN) and stronger (>40 pN) immune complexes that implies the existence of at least two bound states with different mechanical stability. The two-dimensional force-free off-rate for the DNA-antibody complexes was ~2.2 × 10^-3 s^-1, the transition state distance was ~0.94 nm, the apparent on-rate was ~5.26 s^-1, and the stiffness of the DNA-antibody complex was characterized by a spring constant of 0.0021 pN/nm, suggesting that the DNA-antibody complex is a relatively stable, but soft and deformable macromolecular structure. The stretching elasticity of the DNA molecules was characteristic of single-stranded DNA, suggesting preferential binding of the MRL4 antibody to one strand of DNA. Collectively, the results provide fundamental characteristics of formation and forced dissociation of DNA-antibody complexes that help to understand principles of DNA-protein interactions and shed light on the molecular basis of autoimmune diseases accompanied by formation of anti-DNA antibodies.

Antigen and substrate withdrawal in the management of autoimmune thrombotic disorders

Prevailing approaches to manage autoimmune thrombotic disorders, such as heparin-induced thrombocytopenia, antiphospholipid syndrome and thrombotic thrombocytopenic purpura, include immunosuppression and systemic anticoagulation, though neither provides optimal outcome for many patients. A different approach is suggested by the concurrence of autoantibodies and their antigenic targets in the absence of clinical disease, such as platelet factor 4 in heparin-induced thrombocytopenia and β(2)-glycoprotein-I (β(2)GPI) in antiphospholipid syndrome. The presence of autoantibodies in the absence of disease suggests that conformational changes or other alterations in endogenous protein autoantigens are required for recognition by pathogenic autoantibodies. In thrombotic thrombocytopenic purpura, the clinical impact of ADAMTS13 deficiency caused by autoantibodies likely depends on the balance between residual antigen, that is, enzyme activity, and demand imposed by local genesis of ultralarge multimers of von Willebrand factor. A corollary of these concepts is that disrupting platelet factor 4 and β(2)GPI conformation (or ultralarge multimer of von Willebrand factor oligomerization or function) might provide a disease-targeted approach to prevent thrombosis without systemic anticoagulation or immunosuppression. Validation of this approach requires a deeper understanding of how seemingly normal host proteins become antigenic or undergo changes that increase antibody avidity, and how they can be altered to retain adaptive functions while shedding epitopes prone to elicit harmful autoimmunity.

Administration of M. leprae Hsp65 interferes with the murine lupus progression

The heat shock protein [Hsp] family guides several steps during protein synthesis, are abundant in prokaryotic and eukaryotic cells, and are highly conserved during evolution. The Hsp60 family is involved in assembly and transport of proteins, and is expressed at very high levels during autoimmunity or autoinflammatory phenomena. Here, the pathophysiological role of the wild type [WT] and the point mutated K⁴⁰⁹A recombinant Hsp65 of M. leprae in an animal model of Systemic Lupus Erythematosus [SLE] was evaluated in vivo using the genetically homogeneous [NZBxNZW]F₁ mice. Anti-DNA and anti-Hsp65 antibodies responsiveness was individually measured during the animal's life span, and the mean survival time [MST] was determined. The treatment with WT abbreviates the MST in 46%, when compared to non-treated mice [p<0.001]. An increase in the IgG2a/IgG1 anti-DNA antibodies ratio was also observed in animals injected with the WT Hsp65. Incubation of BALB/c macrophages with F₁ serum from WT treated mice resulted in acute cell necrosis; treatment of these cells with serum from K⁴⁰⁹A treated mice did not cause any toxic effect. Moreover, the involvement of WT correlates with age and is dose-dependent. Our data suggest that Hsp65 may be a central molecule intervening in the progression of the SLE, and that the point mutated K⁴⁰⁹A recombinant immunogenic molecule, that counteracts the deleterious effect of WT, may act mitigating and delaying the development of SLE in treated mice. This study gives new insights into the general biological role of Hsp and the significant impact of environmental factors during the pathogenesis of this autoimmune process.

The Generation of Extracellular DNA in SLE: the Role of Death and Sex

DNA is a large macromolecule that plays a central role in the pathogenesis of systemic lupus erythematosus (SLE), serving as a target antigen of autoantibodies as well as a major component of immune complexes. These complexes can both promote immune disturbances as well as deposit in the kidney to incite inflammation. While the origin of anti-DNA autoantibodies in SLE has received intense investigation, the mechanisms by which DNA exits cells to form immune complexes in the circulation is not well understood. To determine the origin of DNA circulating in the blood in SLE, our laboratory has been using a murine model system to track the in vivo fate of DNA from Jurkat T cells that have been made apoptotic or necrotic in vitro and then administered to mice. Results of these studies indicate that DNA from apoptotic and necrotic cells appears in the blood in a time- and dose-dependent manner. Irrespective of origin, this DNA has properties of nucleosomes as shown by its molecular weight. The process of release requires the presence of macrophages and can be modified by glucocorticoids as well as inflammation. In addition, sex may play a role in the generation of extracellular DNA from dead cells as male and female mice differ in their responses in this model. Together, these studies clarify the origin of extracellular DNA circulating in the blood in SLE and suggest steps in this process that can be interdicted by novel therapy.

Development and selection of edited B cells in B6.56R mice

Tolerance to dsDNA is broken in mice with a high-affinity anti-DNA H chain transgene, 56R, on the C57BL/6 background (B6.56R). B6.56R produce more anti-dsDNA Abs than BALBc.56R. To investigate how anti-DNA Abs are regulated on the B6 background, phenotypic and genetic studies were performed. B6.56R have reduced numbers of B cells and phenotypically altered B cell subsets, including relative increases in the proportions of IgM-negative bone marrow B cells, cells with a marginal zone phenotype, and cells with a transitional T3 phenotype. The peripheral B cell repertoire in B6.56R is restricted: most B cells express the 56R H chain and use a similar, limited subset of editor L chains. DNA binding is more common in B6.56R because the repertoire is shifted toward L chains that are more permissive for DNA binding. H chain editing is also observed and is increased in spontaneous as compared with LPS hybridomas. A subset of spontaneous hybridomas appears to lack H chain expression.

MERTK polymorphisms associated with risk of haematological disorders among Korean SLE patients

OBJECTIVE

The MER receptor tyrosine kinase (MERTK) gene is critical for the efficient clearance of apoptotic cells and has implications for inflammation and autoimmune diseases such as systemic lupus erythematosus (SLE). We investigated the genetic polymorphisms in MERTK to evaluate it as a potential candidate gene for a host genetic study of SLE and clinical manifestations in patients with SLE.

METHODS

By resequencing the coding and flanking regions of the MERTK gene in 24 unrelated Koreans, 37 polymorphisms were identified. Based on gene position, minor allele frequency and inter-single-nucleotide polymorphism (SNP) linkage disequilibrium, six of these polymorphisms were selected for subsequent genotyping and association analysis with the risk of SLE and haematological disorders in 350 Korean SLE patients and 330 controls.

RESULTS

Although no significant associations with the risk of SLE were found, logistic regression analyses revealed that variants +465C > G (P = 0.05) and +130215insdelT (P = 0.0005) were significantly associated with decreased risk of leucopenia in SLE patients. Further, +465C > G, +95616G > A, +123157A > G and the haplotype ht1 also showed significant associations (P = 0.006-0.05) with a decreased risk of lymphopenia in SLE patients.

CONCLUSION

Our findings suggest that polymorphisms in MERTK might be one of the genetic risk factors for presenting leucopenia and lymphopenia in SLE patients.

The binding of sera of patients with SLE to bacterial and mammalian DNA

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antibodies to DNA (anti-DNA). Although these antibodies have features of antigen drive, the source of this DNA is not defined. To assess the potential role of foreign and self-DNA as driving antigens, the specificity of SLE sera for bacterial and mammalian DNA was evaluated. Micrococcus lysodeikticus (MC) and calf thymus (CT) DNA were tested as antigens, with absorption on CT DNA columns used to identify antibodies to antigenic sites on the two DNA. Among 9 sets of longitudinal sera tested, all showed binding to both DNA, and none showed exclusive or predominant binding to CT DNA. With absorbed sera, antibodies could be distinguished in terms of cross-reactive or selective binding to the DNAs. These findings suggest that anti-DNA antibodies vary in specificity and are consistent with a role of both foreign and self-DNA in anti-DNA induction.

Antinucleosome antibodies and decreased deoxyribonuclease activity in sera of patients with systemic lupus erythematosus

Nucleosomes are the dominant autoantigens in patients with systemic lupus erythematosus (SLE), and immune complexes involving nucleosomes are the major cause of tissue damage. The activity of DNase I, the enzyme responsible for nucleosome degradation, has been found to be decreased in patients with SLE. However, it is not known whether DNase activity is a clinically useful parameter. The aim of our study was to assess DNase activity in a prospective study of 113 patients with SLE in relation to disease activity and organ involvement. We included two control groups: 9 patients with undifferentiated connective tissue disease (UCTD) and 14 healthy individuals. DNase activity was found to be lower in patients with SLE (63.75%+/-12.1%) than in the controls (81.3%+/-9.25%) (P<0.001). DNase activity in patients with UCTD (64.9%+/-18.2%; P=0.854) did not differ from that in patients with SLE. Patients with SLE had higher antinucleosome antibody titers (356.3+/-851) than the controls (1.44+/-2.77; P<0.01) or UCTD patients (39.9+/-57.7; P<0.01). In addition, samples positive for antinucleosome antibodies displayed low levels of DNase activity. Within the SLE group, the presence of renal disease had no impact on DNase activity or antinucleosome antibody titers. Also, the SLE disease activity index showed no correlation with DNase activity. In a longitudinal study of six SLE patients, DNase activity did not follow disease activity or autoantibody titers. Our results confirm that serum DNase activity is decreased in patients with SLE, but we conclude that it is not a clinically useful parameter for the prediction of flare-ups of disease or renal involvement.

Anti-telomere antibodies in systemic lupus erythematosus (SLE): a comparison with five antinuclear antibody assays in 430 patients with SLE and other rheumatic diseases

OBJECTIVE

To investigate the prevalence and diagnostic significance of antibodies against telomeric DNA in systemic lupus erythematosus (SLE) and other autoimmune rheumatic diseases, and to make comparisons with five conventional anti-DNA or anti-nuclear antibody (ANA) assays.

METHODS

Antibodies to telomeres, which are highly repetitive sequences of DNA (TTAGGG/CCCTAA) at the end of eukaryotic chromosomes, were measured by an enzyme linked immunosorbent assay (ELISA) in 305 patients with SLE and 125 patients with other autoimmune rheumatic diseases (78 rheumatoid arthritis, 32 primary Sjögren's syndrome, eight mixed connective tissue disease, seven miscellaneous rheumatic diseases). Other assays used were two commercial ELISA assays for anti-dsDNA using calf thymus as antigen, Crithidialuciliae immunofluorescence, and radioimmunoassay (RIA) for anti-dsDNA and immunofluorescence using Hep-2 cells for ANA.

RESULTS

The prevalence of anti-telomere in SLE was 60%, v 5% in rheumatoid arthritis and 18% in other autoimmune rheumatic diseases. Specificity of anti-telomere for SLE was 91%; positive and negative predictive values were 95% and 46%, respectively. For anti-dsDNA by two ELISA assays using calf thymus as antigen, sensitivities were 69% and 29% and specificities 66% and 96%, respectively. Other anti-dsDNA assays had low sensitivities (RIA 43%, Crithidia immunofluorescence 13%). The association of anti-telomere with a history of nephritis in patients with SLE was stronger (p = 0.005) than by any other assay (p = 0.006-0.999). The correlations between the different assays were good (p<0.001 for all comparisons).

CONCLUSIONS

The new ELISA for anti-telomere antibodies using standardised human dsDNA as antigen is a sensitive and highly specific test for SLE.

B lymphocytes and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by B cell hyperactivity in association with autoantibodies, most prominently those directed to components of the cell nucleus. The source of the antigens that drive B cell responses in SLE is unknown, although recent studies suggest mechanisms by which the self-antigens become immunogenic and stimulate responses. Among these mechanisms, abnormalities in the generation of apoptotic cells or their clearance may increase the availability of nuclear antigens to drive responses. In addition, autoantibody crossreactivity may promote induction of responses to disparate antigens, foreign and self, and enable a single autoantibody to cause disease by crossreactive binding. In addition to reflecting increased exposure to self-antigen, autoantibody responses in SLE may result from abnormalities in B cell signaling and regulation by cytokines. New approaches to therapy aim to abrogate autoantibody production by targeting specific steps in B cell activation, including blockade of T cell costimulation.

The use of fluorometric assays to assess the immune response to DNA in murine systemic lupus erythematosus

Antibodies to DNA (anti-DNA) play an important role in the pathogenesis of systemic lupus erythematosus (SLE). In blood, these antibodies may exist in a free, unbound state or as part of complexes with DNA. Furthermore, circulating DNA may be either complexed or free. Because of the central role of these immunoreactants (anti-DNA and DNA) in the disease, monitoring of their levels could provide valuable information for both clinical and investigative purposes. In these studies, we have explored the use of a DNA-binding dye, PicoGreen, for the detection of circulating DNA, either total or immune complex bound. In addition, we have used this dye for Farr-type antibody assays. Using autoimmune MRL/lpr mice as a model, we have shown that, while the levels of free DNA in the plasma of these mice were comparable with those of normal BALB/c mice, the amounts in complexes precipitable by ammonium sulfate were significantly greater. Furthermore, we showed that Farr assays using PicoGreen reliably detect levels of free anti-DNA, with values correlated with anti-DNA levels by an enzyme-linked immunosorbent assay. Together, our results suggest that a fluorometric dye can accurately monitor DNA and anti-DNA antibody levels in SLE and may provide important information on immunopathogenesis.

Anti-DNA and autoantibodies

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by antinuclear antibodies (ANAs), including pathogenic specificities to DNA. As shown by recent research, ANA production is a genetically determined process in which self antigens drive B and T cells that have escaped the normal mechanisms of tolerance. Although antibodies can bind isolated protein or nucleic acid species, the in vivo driving antigens likely exist as complexes that have been released from apoptotic cells. The clinical measurement of ANAs, although valuable in assessing diagnosis and prognosis, must nevertheless be interpreted with caution because ANAs, despite their disease associations, can occur in healthy individuals.

The role of bacterial DNA in autoantibody induction

Bacterial DNA has potent immunological properties that can stimulate the immune system in SLE in both specific and non-specific ways. As such, this molecule may play an important role in disease pathogenesis, because it can exert immunomodulatory activity and function as a molecular mimic. Future studies will hopefully both determine the role of foreign nucleic acids in the induction of autoantibodies and lead to strategies for their elimination.

Responses of human B cells to DNA and phosphorothioate oligodeoxynucleotides

Emerging information has documented that certain DNA and sODNs can be both immunogenic and immunostimulatory. sODNs, but not DNA, induce T-cell-independent polyclonal activation of human B cells by engaging cell-surface receptors. Manifestations of sODN-induced human B-cell activation include expression of activation markers, proliferation, Ig production and anti-DNA antibody production. IL-2 and intact T cells enhanced B-cell responses to sODNs but were not required. Monocytes also provided a modest enhancement of human B-cell responses induced by sODNs. The chemical nature of sODNs capable of stimulating human B cells and the specific cell-surface receptors involved have not been completely delineated. Further studies will be necessary to elucidate the potential role of stimulatory sODNs in disease pathogenesis and to develop a means to employ ODNs as therapeutic agents in humans.