Antibodies against RNA hydrolyze RNA and DNA

Immunoglobulins with Non-Canonical Functions in Inflammatory and Autoimmune Disease States

Immunoglobulins are known to combine various effector mechanisms of the adaptive and the innate immune system. Classical immunoglobulin functions are associated with antigen recognition and the initiation of innate immune responses. However, in addition to classical functions, antibodies exhibit a variety of non-canonical functions related to the destruction of various pathogens due to catalytic activity and cofactor effects, the action of antibodies as agonists/antagonists of various receptors, the control of bacterial diversity of the intestine, etc. Canonical and non-canonical functions reflect the extreme human antibody repertoire and the variety of antibody types generated in the organism: antigen-specific, natural, polyreactive, broadly neutralizing, homophilic, bispecific and catalytic. The therapeutic effects of intravenous immunoglobulins (IVIg) are associated with both the canonical and non-canonical functions of antibodies. In this review, catalytic antibodies will be considered in more detail, since their formation is associated with inflammatory and autoimmune diseases. We will systematically summarize the diversity of catalytic antibodies in normal and pathological conditions. Translational perspectives of knowledge about natural antibodies for IVIg therapy will be also discussed.

The DNA-hydrolyzing activity of IgG antibodies from human placenta

OBJECTIVE

Since during pregnancy and lactation women tend to develop autoimmune processes, characterization of placenta immunoglobulins and their possible catalytic functions is a very important step towards understanding the function of placenta.

METHODS

ELISA, affinity chromatography, SDS-PAGE and MALDI mass spectrometry were used.

RESULTS

It was shown, that ten placentas contain in average 1.1 ± 0.33 mg IgGs/g of placenta and 0.11 ± 0.1 mЕ anti-DNA antibodies/g of placenta. All ten individual IgG preparations were characterized by a specific ratio and various combinations of heavy (47.5-51.7 kDa) and light (22.2-33.3 kDa) chains with different molecular masses. All intact IgGs demonstrate DNase but have not amylase activity. Several strict criteria have been used to show that the DNase activity is an intrinsic property of placenta IgGs. The heavy chains of antibodies were catalytically inactive. The light chains of 22-24 kDa of all IgGs demonstrated maximal DNase activity, while the chains of approximately 25-33.2 kDa were significantly less active. IgGs were completely inactive after dialysis against EDTA. The optimal external cofactors of placenta DNase abzymes are Mg²⁺ and Cu²⁺ ions, while, activity in the presence of Mn²⁺ and Ca²⁺ is approximately 3-4-fold lower. Activation of DNase abzymes by Cu²⁺ ions was revealed for the first time. Placental antibodies possess selective cytotoxicity against cancer cells.

CONCLUSION

It was shown previously, that appearance of serum DNase abzymes is the good indicator of the beginning and obvious spontaneous or induced autoimmune diseases. The detection of placenta DNase antibodies indicates that during pregnancy, autoimmune processes can affect this organ.

Antibodies to H1 histone from the sera of HIV-infected patients recognize and catalyze site-specific degradation of this histone

Histones and their posttranslational modifications have key roles in chromatin remodeling and gene transcription. Besides intranuclear functions, histones act as damage-associated molecules when they are released into the extracellular space. Administration of histones to animals leads to systemic inflammatory and toxic responses. Autoantibodies with enzymatic activities (abzymes) are distinctive feature of some autoimmune and viral diseases. Electrophoretically and immunologically homogeneous IgGs containing no canonical enzymes were isolated from sera of human immunodeficiency virus-infected patients by chromatography on several affinity sorbents. In contrast to canonical proteases (trypsin, chymotrypsin, and proteinase K), IgGs from human immunodeficiency virus-infected patients purified by affinity chromatography on Sepharose containing immobilized histones specifically recognized and hydrolyzed only histones but not many other tested globular proteins. Using matrix-assisted laser desorption/ionization mass spectrometry, the sites of H1 histone (193 amino acids [AAs]) cleavage by anti-H1 histone IgGs were determined for the first time. It was shown that 1 cluster of 2 major and 4 moderate sites of cleavage is located at the beginning (106-112 AAs) of the known antigenic determinants disposed at the long C-terminal sequence of H1. Two clusters of minor and very weak sites of the protein cleavage correspond to middle (8 sites, 138-158 AAs) and terminal (5 sites, 166-176 AAs) parts of the antigenic determinants. It was shown that in contrast to canonical proteases, N-terminal part of H1 histone (1-136 AAs) containing no antigenic determinants is an unpredictably very resistant against hydrolysis by abzymes, while it can be easily cleavage by canonical proteases. Because histones act as damage-associated molecules, abzymes against H1 and other histones can play important role in pathogenesis of acquired immune deficiency syndrome and probably other different diseases.

DNA-hydrolysing activity of IgG antibodies from the sera of patients with schizophrenia

It is believed that damage to the membranes of brain cells of schizophrenia (SCZ) patients induces the formation of autoantigens and autoantibodies. Nevertheless, the importance of immunological changes leading to the loss of tolerance to self-antigens in the genesis of SCZ has not been established. The MALDI mass spectra of the IgG light chains of 20 healthy donors were relatively homogeneous and characterized by one peak with only one maximum. In contrast to the healthy donors, the MALDI mass spectra of IgG light chains corresponding to 20 SCZ patients demonstrated, similarly to 20 autoimmune systemic lupus erythematosus (SLE) patients, two maxima of a comparable intensity. In addition, the MALDI spectra of the IgG light chains of five SLE and four SCZ patients contained a small additional brightly pronounced peak with remarkably lower molecular mass compared with the main one. DNase autoantibodies (abzymes) can be found in the blood of patients with several autoimmune diseases, while the blood of healthy donors or patients with diseases without a significant disturbance of the immune status does not contain DNase abzymes. Here, we present the first analysis of anti-DNA antibodies and DNase abzymes in the sera of SCZ patients. Several strict criteria have been applied to show that the DNase activity is an intrinsic property of IgGs from the sera of SCZ patients. The sera of approximately 30% of SCZ patients displayed a higher content of antibodies (compared with 37% of SLE) interacting with single- and double-stranded DNA compared with healthy donors. Antibodies with DNase activity were revealed in 80% of the patients. These data indicate that some SCZ patients may show signs of typical autoimmune processes to a certain extent.

Antibodies from the sera of HIV-infected patients efficiently hydrolyze all human histones

Histones and their post-translational modifications have key roles in chromatin remodeling and gene transcription. Besides intranuclear functions, histones act as damage-associated molecular pattern molecules when they are released into the extracellular space. Administration of exogenous histones to animals leads to systemic inflammatory and toxic responses through activating Toll-like receptors and inflammasome pathways. Here, using ELISA it was shown that sera of HIV-infected patients and healthy donors contain autoantibodies against histones. Autoantibodies with enzymic activities (abzymes) are a distinctive feature of autoimmune diseases. It was interesting whether antibodies from sera of HIV-infected patients can hydrolyze human histones. Electrophoretically and immunologically homogeneous IgGs were isolated from sera of HIV-infected patients by chromatography on several affinity sorbents. We present first evidence showing that 100% of IgGs purified from the sera of 32 HIV-infected patients efficiently hydrolyze from one to five human histones. Several rigid criteria have been applied to show that the histone-hydrolyzing activity is an intrinsic property of IgGs of HIV-infected patients. The relative efficiency of hydrolysis of histones (H1, H2a, H2b, H3, and H4) significantly varied for IgGs of different patients. IgGs from the sera of 40% of healthy donors also hydrolyze histones but with an average efficiency approximately 16-fold lower than that of HIV-infected patients. Similar to proteolytic abzymes from the sera of patients with several autoimmune diseases, histone-hydrolyzing IgGs from HIV-infected patients were inhibited by specific inhibitors of serine and of metal-dependent proteases, but an unexpected significant inhibition of the activity by specific inhibitor of thiol-like proteases was also observed. Because IgGs can efficiently hydrolyze histones, a negative role of abzymes in development of acquired immune deficiency syndrome cannot be excluded. Copyright © 2016 John Wiley & Sons, Ltd.

In-Cell RNA Hydrolysis Assay: A Method for the Determination of the RNase Activity of Potential RNases

Conventional procedures to assay RNA degradation by a protein with ribonuclease (RNase) activity require a step to isolate intact RNA molecules, which are used as a substrate. Here, we established a novel “In-cell RNA hydrolysis assay” in which RNAs within cells are used as a substrate for the RNA-hydrolyzing protein, thereby avoiding the need to prepare intact RNA molecules. In this method, the degree of RNA degradation is indicated by the fluorescence intensity of RNA molecules released from fixed and permeabilized cells following treatment with the potential RNase. A catalytic 3D8 antibody capable of degrading RNAs and pancreatic RNase A were used as model RNases. Our data demonstrate that the novel In-cell RNA hydrolysis assay is a reliable and sensitive method to analyze the activities of potential RNA-hydrolyzing proteins such as catalytic antibodies.

Systemic lupus erythematosus: molecular cloning and analysis of recombinant DNase monoclonal κ light chain NGK-1

Because DNase antibodies are cytotoxic, enter the nucleus and cause DNA fragmentation inducing cell death by apoptosis, they can play an important role in the pathogenesis of different autoimmune pathologies and especially systemic lupus erythematosus (SLE). The interesting goal of catalytic antibodies research is not only to study a possible biological role of such antibodies, but also to develop in future new human and animal therapies that use the advantages offered by abzymes. An immunoglobulin κ light chain library from SLE patients was cloned into a phagemid vector. Phage particles displaying recombinant monoclonal antibody light chains (MLChs) capable of binding DNA were isolated by affinity chromatography on DNA-cellulose. Sixteen of the 46 MLChs efficiently hydrolyzed DNA; one MLCh (approximately 27-28kDa) was expressed in Escherichia coli and purified by metal chelating and gel filtration. MLCh NGK-1 was electrophoretically homogeneous and demonstrated a positive answer with mouse IgGs against light chains of human antibodies after western blotting. SDS-PAGE in a gel containing DNA demonstrated that the MLCh hydrolyzes DNA and is not contaminated by canonical DNases. The DNase MLCh was activated by several metal ions. The protein sequence of the DNase MLCh has homology with mammalian DNases I and shares with them several identical or similar (with the same side chain functionality) important amino acid residues, which are necessary for DNA hydrolysis and binding of Mg(2+) and Ca(2+) ions. The affinity of DNA for this first example of a MLCh (K(M) = 0.3 microM) was 150- to 200-fold higher than for human DNase I.

Systemic lupus erythematosus: molecular cloning of several recombinant DNase monoclonal kappa light chains with different catalytic properties

An immunoglobulin light chain phagemid library derived from peripheral blood lymphocytes of three patients with systemic lupus erythematosus was used. Phage particles displaying DNA binding light chains were isolated by affinity chromatography on DNA-cellulose, and the fraction eluted by an acidic buffer (pH 2.6) was used for preparation of individual monoclonal light chains (MLChs, 28 kDa). Thirty three of 687 individual colonies obtained were randomly chosen for study of MLCh DNase activity. Nineteen of 33 clones contained MLChs with DNase activity. Four preparations of MLChs were expressed in Escherichia coli in soluble form, purified by metal chelating chromatography followed by gel filtration, and studied in detail. Detection of DNase activity after SDS-PAGE in a gel containing DNA demonstrated that the four MLChs are not contaminated by canonical DNases. The MLChs demonstrated one or two pH optima. They were inactive after the dialysis against ethylenediaminetetraacetic acid but could be activated by several externally added metal ions; the ratio of relative activity in the presence of Mg(2+) , Mn(2+) , Ni(2+) , Ca(2+) , Zn(2+) , and Co(2+) was individual for each MLCh preparation. K(+) and Na(+) inhibited the DNase activity of various MLChs at different concentrations. Hydrolysis of DNA by all four MLCh was saturable and consistent with Michaelis-Menten kinetics. These clones are the first examples of recombinant MLChs possessing high affinity for DNA (Km  = 3-9 nM) and demonstrating high kcat values (3.4-6.9 min(-1) ). These observations suggest that the systemic lupus erythematosus light chain repertoire can serve as a source of new types of DNases.

IgGs containing λ- and κ-type light chains and of all subclasses (IgG1-IgG4) from the sera of patients with autoimmune diseases and viral and bacterial infections hydrolyze DNA

We present the first evidence demonstrating that small fractions of IgGs of all four subclasses (IgG1-IgG4) from patients with viral (tick-borne encephalitis), bacterial infections (streptococcal infection or erysipelas), and suppurative surgical infections caused by epidermal staphylococci as well as from patients with autoimmune diseases (systemic lupus erythematosus and multiple sclerosis) are catalytically active in the hydrolysis of supercoiled DNA. The hydrolysis of DNA was analyzed by agarose gel electrophoresis. The catalytic activities of nonfractionated IgGs increased in the following order: tick-borne encephalitis < suppurative surgical infection < streptococcal infection < multiple sclerosis < systemic lupus erythematosus, whereas IgGs of healthy donors were inactive. However, the pools of antibodies corresponding to any particular disease were characterized by a specific ratio of IgGs of all four subclasses (IgG1-IgG4) and IgGs containing λ- and κ-type light chains, and each of these subfractions of immunoglobulins demonstrated characteristic relative DNase activity. The relative activities of IgGs containing λ-type light chains may on average be higher, lower, or comparable with those for IgGs with κ-type light chains. The relative contributions of IgGs of different subclasses to the total activity of IgGs also varied widely in the case of various diseases: IgG1 (7%-45%), IgG2 (0.4%-73%), IgG3 (0%-12%), and IgG4 (9%-66%). Thus, immune systems of patients with different diseases can generate a variety of anti-DNA abzymes of different types and with different catalytic properties, which can play an important role in the pathogenesis or protection from the development of these diseases.

DNase, RNase, and phosphatase activities of antibodies formed upon immunization by DNA, DNase I, and DNase II

Relative DNase, RNase (efficiency of hydrolysis of ribo- and deoxyribooligonucleotides (ON)), and phosphatase (removal of the ON 5' terminal phosphate) catalytic activities of antibodies (AB) obtained after rabbit immunization by DNA, DNase I, and DNase II were compared. It is shown that electrophoretically homogeneous preparations of polyclonal AB from non-immunized rabbits did not exhibit such activities. Immunization of rabbits by DNA, DNase I, and DNase II results in generation of IgG abzymes that exhibit high activity in the ON hydrolysis reaction and even higher activity in cleavage of 5' terminal phosphate of ON. In this case K(m) values for supercoiled plasmid DNA and ON found in reactions of their AB-dependent nuclease hydrolysis and phosphatase cleavage of 5' terminal phosphate differ by 2-4 orders of magnitude. This shows that nuclease and phosphatase activities belong to different abzyme fractions within polyclonal AB. Thus, in this work data indicative of the possibility of a formation of antibodies exhibiting phosphatase activity after immunization of animals with DNA, DNase I, and DNase II, were obtained for the first time. Possible reasons for production of AB with phosphatase activity after immunization of rabbits with these immunogens are discussed.

Diversity of DNA-hydrolyzing antibodies from the sera of autoimmune-prone MRL/MpJ-lpr mice

It has been shown for the first time that polyclonal IgG abzymes (Abzs) with DNase activity from the sera of autoimmune-prone MRL/MpJ-lpr mice can be separated by isoelectric focusing into many subfractions having the isoelectric points (pI) from 4.5 to 9, with the maximal activity for Abzs with pI = 6.5-9.0. Affinity chromatography on DNA-cellulose separated DNase IgGs into many subfractions demonstrating a range of affinities for DNA and different levels of the relative DNase activities (RDA) due to intrinsically bound metals and after addition of external Mg(2+) , Mn(2+) , Ca(2+), and Mg(2+) +Ca(2+). Some fractions significantly increase RDAs in the presence of external ions (Mg(2+) + Ca(2+)  > Mg(2+)  > Mn(2+)  > Ca(2+)), while each of this cofactor can also inhibit or have no influence on the RDAs of another fractions. It is known that complexes of DNA with histones and other proteins of apoptotic cells are the primary immunogens in systemic lupus erythematosus (SLE). Bovine serum albumin (BSA) and methylated BSA (mBSA) increase the RDAs of only some fractions, while have no effect or inhibit other IgG fractions. The ratio of the RDAs in the presence of all metal ions, BSA, and mBSA was individual for every abzyme fraction. Mn(2+) and Ca(2+) stimulated accumulation of only relaxed form of supercoiled DNA (scDNA) in the case of all subfractions, while in the presence of Mg(2+) antibodies (Abs) of some subfractions (and in the presence of Mn(2+) +Ca(2+) all subfractions) produced relaxed DNA (rDNA) and linear DNA (linDNA) in a variable extent. The data obtained show that the polyclonal Abzs of mice may be a cocktail of Abs directly to DNA, RNA, and their complexes with proteins and anti-idiotypic Abs to active centers of different nucleases. The diversity of the physicochemical and kinetic characteristics of the Abzs seems to be significantly widened when pre-diseased mice spontaneously develop the disease.

An RNA-hydrolyzing recombinant antibody exhibits an antiviral activity against classical swine fever virus

Some proteins with ribonuclease (RNase) activity have been shown to suppress viral replication. A well-characterized recombinant antibody, 3D8 single-chain variable fragment (3D8 scFv), has RNA-hydrolyzing and cell-penetrating activities. Here, we investigated antiviral activity of 3D8 scFv against classical swine fever virus (CSFV). In a cell line expressing 3D8 scFv (C26), intracellular RNA-hydrolysis activity was higher compared to control PK-15 cells and viral replication was strongly suppressed at the viral RNA level, with the evidence of independency of IFN-alpha/beta induction. Exogenous treatment of 3D8 scFv, prior to or post-CSFV infection, was also shown to suppress CSFV replication at the viral RNA level. These observations suggest that antiviral activity of 3D8 scFv may be due to the intrinsic RNase activity of 3D8 scFv, which is capable of targeting viral RNA genomes or transcripts.

Peculiarities of abzymes from sera and milk of healthy donors and patients with autoimmune and viral diseases

The detection of catalytic activity of antibodies is the earliest indicator of development of autoimmune diseases (AID). In early stages of AID, the repertoire of abzymes with various properties is relatively small, but it is greatly increased during their development. Catalytic diversity of the abzymes includes DNase, RNase, ATPase, and oxidoreductase activities; there are antibodies phosphorylating proteins, lipids, and polysaccharides. This review summarizes new data on abzyme heterogeneity and possible reasons for this phenomenon. A possible role of abzymes and their exceptional multiplicity in the pathogenesis of different AID is discussed.

DNA-hydrolyzing activity of IgG antibodies from the sera of patients with tick-borne encephalitis

DNase autoantibodies (Abzs) can be found in the blood of patients with several autoimmune diseases, while the blood of healthy donors or patients with diseases with an insignificant disturbance of the immune status does not contain DNase Abzs. Here we present the first analysis of the DNase Abzs activity in the patients with tick-borne encephalitis (TBE). Several strict criteria have been applied to show that the DNase activity is an intrinsic property of IgGs from the sera of TBE patients but not from healthy donors. The relative activity of IgGs has been shown to vary extensively from patient to patient, but most of the preparations (91%) had detectable levels of the DNase activity. Polyclonal DNase IgGs were not active in the presence of EDTA or after a dialysis against EDTA, but could be activated by several externally added metal ions, with the level of activity decreasing in the order Mn(2+) + Ca(2+) > or = Mn(2+)+ Mg(2+) > or = Mn(2+) > or = Mg(2+) + Ca(2+) > or = Co(2+) > or = Mg(2+) > Ca(2+), while K(+), Na(+), Ni(2+), Zn(2+), and Cu(2+) did not stimulate DNA hydrolysis. Affinity chromatography on DNA-cellulose separated the DNase IgGs into many subfractions with various affinities for DNA and very different levels of the relative activity. Possible reasons for catalytic diversity of polyclonal human Abzs are discussed.