Catalytic antibodies in clinical and experimental pathology: human and mouse models

gp120-derived amyloidogenic peptides form amyloid fibrils that increase HIV-1 infectivity

Apart from mediating viral entry, the function of the free HIV-1 envelope protein (gp120) has yet to be elucidated. Our group previously showed that EP2 derived from one β-strand in gp120 can form amyloid fibrils that increase HIV-1 infectivity. Importantly, gp120 contains ~30 β-strands. We examined whether gp120 might serve as a precursor protein for the proteolytic release of amyloidogenic fragments that form amyloid fibrils, thereby promoting viral infection. Peptide array scanning, enzyme degradation assays, and viral infection experiments in vitro confirmed that many β-stranded peptides derived from gp120 can indeed form amyloid fibrils that increase HIV-1 infectivity. These gp120-derived amyloidogenic peptides, or GAPs, which were confirmed to form amyloid fibrils, were termed gp120-derived enhancers of viral infection (GEVIs). GEVIs specifically capture HIV-1 virions and promote their attachment to target cells, thereby increasing HIV-1 infectivity. Different GAPs can cross-interact to form heterogeneous fibrils that retain the ability to increase HIV-1 infectivity. GEVIs even suppressed the antiviral activity of a panel of antiretroviral agents. Notably, endogenous GAPs and GEVIs were found in the lymphatic fluid, lymph nodes, and cerebrospinal fluid (CSF) of AIDS patients in vivo. Overall, gp120-derived amyloid fibrils might play a crucial role in the process of HIV-1 infectivity and thus represent novel targets for anti-HIV therapeutics.

The Heterogeneous Multiple Sclerosis Lesion: How Can We Assess and Modify a Degenerating Lesion?

Multiple sclerosis (MS) is a heterogeneous disease of the central nervous system that is governed by neural tissue loss and dystrophy during its progressive phase, with complex reactive pathological cellular changes. The immune-mediated mechanisms that promulgate the demyelinating lesions during relapses of acute episodes are not characteristic of chronic lesions during progressive MS. This has limited our capacity to target the disease effectively as it evolves within the central nervous system white and gray matter, thereby leaving neurologists without effective options to manage individuals as they transition to a secondary progressive phase. The current review highlights the molecular and cellular sequelae that have been identified as cooperating with and/or contributing to neurodegeneration that characterizes individuals with progressive forms of MS. We emphasize the need for appropriate monitoring via known and novel molecular and imaging biomarkers that can accurately detect and predict progression for the purposes of newly designed clinical trials that can demonstrate the efficacy of neuroprotection and potentially neurorepair. To achieve neurorepair, we focus on the modifications required in the reactive cellular and extracellular milieu in order to enable endogenous cell growth as well as transplanted cells that can integrate and/or renew the degenerative MS plaque.

DNA hydrolysing IgG catalytic antibodies: an emerging link between psychoses and autoimmunity

It is not uncommon to observe autoimmune comorbidities in a significant subset of patients with psychotic disorders, namely schizophrenia (SCZ) and bipolar disorder (BPD). To understand the autoimmune basis, the DNA abyzme activity mediated by serum polyclonal IgG Abs were examined in psychoses patients, quantitatively, by an in-house optimized DNase assay. A similar activity exhibited by IgG Abs from neuropsychiatric-systemic lupus erythematosus (NP-SLE) patients was used as a comparator. Our data revealed that the IgG DNase activity of SCZ was close to that of NP-SLE and it was twofold higher than the healthy controls. Interestingly, the association between DNase activity with PANSS (positive, general and total scores) and MADRS were noted in a subgroup of SCZ and BPD patients, respectively. In our study group, the levels of IL-6 and total IgG in BPD patients were higher than SCZ and healthy controls, indicating a relatively inflammatory nature in BPD, while autoimmune comorbidity was mainly observed in SCZ patients.

Differential Diagnostics of Active Progressing Multiple Sclerosis Using a Fluorescent Biomarker with Resonance Energy Transfer

Previous data showed that myelin-reactive autoantibodies found in patients with multiple sclerosis and mice with experimental autoimmune encephalomyelitis recognize and hydrolyze various fragments of myelin basic protein (MBP). Moreover, antibody-mediated cleavage of the encephalithogenic fragment MBP_81-103 flanked with two fluorescent proteins can serve as a new biomarker of multiple sclerosis. Here we describe creation of the next generation of this biomarker based on antibody-dependent degradation of a new chemically synthesized fluorescent substrate with resonance energy transfer that contains fluorophore Cy5 and quencher QXL680 separated by MBP_81-99 protein (Cy5-MBP_81-99-QXL680). This substrate is degraded during incubation with purified antibodies and B cells from patients with multiple sclerosis, but not healthy volunteers.

Diagnostics of autoimmune neurodegeneration using fluorescent probing

The discovery of antibody-mediated catalysis was a breakthrough that showed antibody function is not limited to specific binding interactions, and that immunoglobulins (Igs) may also chemically transform their target antigens. Recently, so-called “natural catalytic antibodies” have been intimately linked with several pathologies, where they either protect the organism or contribute to the development of autoimmune abnormalities. Previously, we showed that myelin-reactive autoantibodies from patients with multiple sclerosis (MS) and mice with experimental autoimmune encephalomyelitis (EAE) exhibit the ability to recognize and hydrolyse distinct epitopes within myelin basic protein (MBP). Further, the antibody-mediated cleavage of encephalitogenic MBP peptide 81–103, flanked by two fluorescent proteins, can serve as a novel biomarker for MS. Here, we report the next generation of this biomarker, based on the antibody-mediated degradation of a novel chemically synthesized FRET substrate, comprising the fluorophore Cy5 and the quencher QXL680, interconnected by the MBP peptide 81–99: Cy5-MBP_81–99-QXL680. This substrate is degraded upon incubation with either purified antibodies from MS patients but not healthy donors or purified antibodies and splenocytes from EAE but not from non-immunized mice. Data presented herein suggest the elaboration of potential specific, rapid, and sensitive diagnostic criteria of active progressive MS.

Catalytic antibodies in patients with systemic lupus erythematosus

OBJECTIVE

Antibodies with catalytic (hydrolytic) properties to DNA or RNA have been reported in systemic lupus erythematosus (SLE). However, it is well known that ethnicity plays an important role in the presentation of SLE and severity of the disease; hence, these data may not truly represent a general feature of all SLE patients. Therefore, we have analyzed the hydrolyzing activity of immunoglobulin G (IgG) of SLE patients from the Indian population with an aim to decode whether the catalytic antibody response represents part of an active disease process.

METHODS

IgGs were isolated from the sera of 72 consecutive patients diagnosed with SLE. As a control, IgGs from healthy donors were used. The catalytic activity of IgG was measured by PFR-MCA and affinity-linked oligonucleotide nuclease assay.

RESULTS

IgGs from patients with SLE from the Indian subcontinent displayed significantly higher hydrolysis rates of both the surrogate substrate, PFR-MCA, and the DNA than IgG from healthy individuals. Intergroup comparisons of the IgG-PFR-MCA interactions with clinical manifestations of the disease demonstrated a significantly increased level of hydrolysis among the patients with renal involvement who tested positive for anti-dsDNA antibodies. The PFR-MCA hydrolysis also appears to be associated with the active disease (p=0.0988, vs. inactive group).

CONCLUSION

The prevalence of catalytic antibodies represents a general feature of SLE patients, irrespective of their origin.

Dengue Virus Nonstructural Protein 1-Induced Antibodies Cross-React with Human Plasminogen and Enhance Its Activation

Dengue virus (DENV) infection is the most common mosquito-borne viral disease, and it can cause life-threatening dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Abnormal activation of the coagulation and fibrinolysis system is one of the hallmarks of DHF/DSS. However, the mechanism underlying hemorrhage in DHF/DSS remains elusive. In previous studies, plasminogen (Plg) cross-reactive Abs, which can recognize DENV nonstructural protein (NS) 1, have been found in dengue patients. However, it is unclear whether these Abs are indeed induced by DENV NS1. Thus, we immunized mice with recombinant NS1 from both bacteria and drosophila to determine whether NS1 can induce Plg cross-reactive Abs. The results from the NS1-immunized mouse sera indicated that NS1 immunization induced Abs that could cross-react with Plg. To study the effects of these NS1-induced Plg cross-reactive Abs on fibrinolysis, we isolated several Plg cross-reactive anti-NS1 mAbs from these mice and found that some of them could enhance Plg activation. In addition, epitope mapping with a phage-displayed random peptide library revealed that one of these mAbs (2A5) could recognize NS1 C-terminal residues 305-311, which share sequence homology with Plg residues 590-597. A synthetic peptide of NS1 residues 305-311 could inhibit the binding of both 2A5 and its Fab to Plg and its enhanced activation. Thus, our results suggest that DENV NS1 can induce Plg cross-reactive Abs through molecular mimicry, which can enhance Plg activation and may contribute to the pathogenesis of DHF/DSS.

Anti-DNA antibody mediated catalysis is isotype dependent

Anti-DNA antibodies are the serological hallmark of systemic lupus erythematosus, and participate in the pathogenesis of lupus nephritis by cross-reacting with multiple renal antigens. Previously, using a panel of murine anti-DNA IgGs that share identical variable regions but that differ in the constant regions, we demonstrated that the cross-reaction and renal pathogenicity of anti-DNA antibodies are isotype dependent. In this study, we investigated the catalytic potential of this anti-DNA antibody panel, and determined its isotype dependency. The three isotype switch variants (IgG1, IgG2a, IgG2b) and the parent IgG3 PL9-11 anti-DNA antibodies were compared in their catalysis of 500 base pair linear double stranded DNA and a 12-mer peptide (ALWPPNLHAWVP), by gel analysis, MALDI-TOF mass spectrometry, and nuclear magnetic resonance spectroscopy. The binding affinity of anti-DNA antibodies to double stranded DNA and peptide antigens were assessed by ELISA and surface plasmon resonance. We found that the PL9-11 antibody isotypes vary significantly in their potential to catalyze the cleavage of both linear and double stranded DNA and the proteolysis of peptides. The degree of the cleavage and proteolysis increases with the incubation temperature and time. While different PL9-11 isotypes have the same initial attack sites within the ALWPPNLHAWVP peptide, there was no correlation between binding affinity to the peptide and proteolysis rates. In conclusion, the catalytic properties of anti-DNA antibodies are isotype dependent. This finding provides further evidence that antibodies that share the same variable region, but which have different constant regions, are functionally distinct. The catalytic effects modulated by antibody constant regions need to be considered in the design of therapeutic antibodies (abzymes) and peptides designed to block pathogenic autoantibodies.

Clinical and experimental studies of multiple sclerosis in Russia: experience of the leading national research centers

Mechanisms of axonal damage and adaptive capacity in multiple sclerosis (MS), including cortical reorganization, have been actively studied in recent years. The lack of regenerative capabilities and the irreversibility of neurodegeneration in MS are critical factors for the optimization of MS treatment. In this study, we present the results of clinical and basic studies in the field of MS by two leading Russian centers. Clinical and neuroimaging correlations show that spinal damage in MS is accompanied by functional reorganization of the cerebral cortex, which is determined not only by the efferent component but also by the afferent component. Comparative analysis of MS treatment with both interferon β1b (IFN-β1b) and IFN-β1a at a dosage of 22 µg for 3 years through subcutaneous administration and glatiramer acetate showed equally high efficiency in reducing the number of exacerbations in relapsing-remitting MS and secondary-progressive MS. We demonstrate a reduced risk of disability in relapsing-remitting MS and secondary-progressive MS patients in all groups treated with IFN-β1 and glatiramer acetate. MS appears to be a disease that would greatly benefit from the development of personalized therapy; thus, adequate molecular predictors of myelin degradation are greatly needed. Therefore, novel ideas related to the viral hypothesis of the etiology of MS and new targets for therapeutic intervention are currently being developed. In this manuscript, we discuss findings of both clinical practice and fundamental research reflecting challenges and future directions of MS treatment in the Russian Federation.

RNA aptamer against autoantibodies associated with multiple sclerosis and bioluminescent detection probe on its basis

Nowadays, there are no specific laboratory tests for establishing the diagnosis of multiple sclerosis (MS). The presence of proteolytic autoantibodies against myelin basic protein is now considered as a characteristic feature of MS. New 2'-F-containing RNA aptamer of high affinity and specificity to these antibodies was selected. Covalent conjugate of this aptamer and Ca(2+)-regulated photoprotein obelin was obtained for the first time and applied as a label in bioluminescent microplate assay to detect target antibodies. The developed model solid-phase microassay is simple, fast, and highly sensitive.

Antibody-antigen pair probed by combinatorial approach and rational design: bringing together structural insights, directed evolution, and novel functionality

The unique hypervariability of the immunoglobulin (Ig) superfamily provides a means to create both binding and catalytic antibodies with almost any desired specificity and activity. The diversity of antigens and concept of adaptive response suggest that it is possible to find an antigen pair to any raised Ig. In the current review we discuss combinatorial approaches, which makes it possible to obtain an antibody with predefined properties, followed by 3D structure-based rational design to enhance or dramatically change its characteristics. A similar strategy, but applied to the second partner of the antibody-antigen pair, may result in selection of complementary substrates to the chosen Ig. Finally, 2D screening may be performed solving the "Chicken and Egg" problem when neither antibody nor antigen is known.

A novel molecular analysis of genes encoding catalytic antibodies

Among the numerous questions remaining opened about catalytic antibodies (abzymes), the understanding of the origin of the genes encoding them is of vital significance. An original statistical analysis of genes encoding abzymes is described in the present report. Results suggested that these genes display a high conservation degree with their germline counterpart and a limited number of amino acid changes. Hence, on the contrary with high-affinity antibodies, maturation process by accumulation of somatic hypermutations is not required for the catalytic function. We demonstrated that despite a weak somatic mutation rate, the physicochemical properties of mutated amino acid (AA) are predominantly dissimilar with that of the germline AA. Further, we developed a novel approach in order to analyze the nature of genes encoding catalytic antibodies. For the first time, an unexpected and significant high level expression of rare gene subgroups was noticed and emphasized. The data described in this paper would lay the foundation for future studies about origin of genes encoding catalytic antibodies.

Do proteolytic antibodies complete the panoply of the autoimmune response in acquired haemophilia A?

Acquired haemophilia A (AHA) is a rare bleeding disorder characterized by the sudden generation of autoantibodies against factor VIII (FVIII) in individuals with no previous history of abnormal haemostasis. Understanding the pathogenesis of this disease has been hampered by the rarity of the patients and the difficulty in obtaining biological material from untreated patients. Still, progress has been made recently in understanding the pathogenesis of AHA. In particular, the importance of CD4(+) T cells in AHA development has been documented and the epitopes targeted by T cells on FVIII have been delineated. Accordingly, a polymorphism in the cytotoxic T-lymphocyte-associated protein 4 gene (CTLA4), known to participate in the regulation of CD4(+) T-cell responses, and a preferential usage of certain human leukocyte antigen class II haplotypes, have been associated with the disease. Recent findings have documented the presence of immunoglobulin G (IgG) with proteolytic activity against FVIII and factor IX (FIX) in patients with AHA. While FVIII-hydrolysing IgG has been shown to inactivate FVIII, FIX-hydrolysing IgG from AHA patients activate FIX in vitro. Here, we describe the latest findings on the immuno-pathogenesis of AHA, with a special focus on the potential role played by antibodies endowed with proteolytic properties.

Evidence for the role of B cells and immunoglobulins in the pathogenesis of multiple sclerosis

The pathogenesis of multiple sclerosis (MS) remains elusive. Recent reports advocate greater involvement of B cells and immunoglobulins in the initiation and propagation of MS lesions at different stages of their ontogeny. The key role of B cells and immunoglobulins in pathogenesis was initially identified by studies in which patients whose fulminant attacks of demyelination did not respond to steroids experienced remarkable functional improvement following plasma exchange. The positive response to Rituximab in Phase II clinical trials of relapsing-remitting MS confirms the role of B cells. The critical question is how B cells contribute to MS. In this paper, we discuss both the deleterious and the beneficial roles of B cells and immunoglobulins in MS lesions. We provide alternative hypotheses to explain both damaging and protective antibody responses.

Combinatorial antibody library from multiple sclerosis patients reveals antibodies that cross-react with myelin basic protein and EBV antigen

Multiple sclerosis (MS) is a widespread neurodegenerative autoimmune disease with unknown etiology. It is increasingly evident that, together with pathogenic T cells, autoreactive B cells are among the major players in MS development. The analysis of myelin neuroantigen-specific antibody repertoires and their possible cross-reactivity against environmental antigens, including viral proteins, could shed light on the mechanism of MS induction and progression. A phage display library of single-chain variable fragments (scFvs) was constructed from blood lymphocytes of patients with MS as a potential source of representative MS autoantibodies. Structural alignment of 13 clones selected toward myelin basic protein (MBP), one of the major myelin antigens, showed high homology within variable regions with cerebrospinal fluid MS-associated antibodies as well as with antibodies toward Epstein-Barr latent membrane protein 1 (LMP1). Three scFv clones showed pronounced specificity to MBP fragments 65-92 and 130-156, similar to the serum MS antibodies. One of these clones, designated E2, in both scFv and full-size human antibody constructs, was shown to react with both MBP and LMP1 proteins in vitro, suggesting natural cross-reactivity. Thus, antibodies induced against LMP1 during Epstein-Barr virus infection might act as inflammatory trigger by reacting with MBP, suggesting molecular mimicry in the mechanism of MS pathogenesis.

Autoantibodies with enzymatic properties in human autoimmune diseases

Immunoglobulins (Ig) or antibodies are heavy plasma proteins, with sugar chains added to amino acid residues by N-linked glycosylation and occasionally by O-linked glycosylation. The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation with activation of complement and activation of effector cells. In addition to this plethora of functions, some antibodies express enzymatic activity. Antibodies endowed with enzymatic properties have been described in human autoimmune manifestations in a variety of disorders such as autoimmune thyroiditis, systemic erythematosus (SLE), scleroderma, rheumatoid arthritis (RA), multiple sclerosis (MS) and acquired hemophilia (AH). Antibodies isolated from these conditions were able to specifically hydrolyze thyroglobulin, DNA, RNA, myelin basic protein (MBP), and factor VIII (FVIII) or factor IX (FIX), respectively. The therapeutic relevance of these findings is discussed.

Anti-histone H1 IgGs from blood serum of systemic lupus erythematosus patients are capable of hydrolyzing histone H1 and myelin basic protein

Novel hydrolytic activity of the anti-histone H1 antibodies (Ab) toward histone H1 and myelin basic protein (MBP) was shown. Blood serum of ten patients with clinically diagnosed systemic lupus erythematosus (SLE), and nine healthy donors (control) were screened for the anti-histone H1 antibody- and anti-MBP antibody-mediated specific proteolytic activity. IgGs were isolated by chromatography on Protein G-Sepharose, and four of ten SLE patients appeared to possess IgGs that were capable of cleaving both histone H1 and MBP. Such activity was confirmed to be an intrinsic property of the IgG molecule, since it was preserved at gel filtration at alkaline and acidic pH. At the same time, proteolytic activity was absent in the sera-derived Ab of all healthy donors under control. Anti-histone IgGs were purified by the affinity chromatography on histone H1-Sepharose. Their cross-reactivity toward cationic proteins (histones, lysozyme, and MBP) and their capability of hydrolyzing histone H1 and MBP were detected. However, these IgGs were not cleaving core histones, lysozyme, or albumin. Capability of cleaving histone H1 and MBP was preserved after additional purification of anti-histone H1 IgGs by the HPLC gel filtration. The protease activity of anti-histone H1 IgG Ab was inhibited by serine protease inhibitors.

Proteolytic antibodies activate factor IX in patients with acquired hemophilia

Acquired hemophilia is a rare bleeding disorder characterized by the spontaneous occurrence of inhibitory antibodies against endogenous factor VIII (FVIII). IgG from some patients with acquired hemophilia hydrolyze FVIII. Because of the complex etiology of the disease, no clinical parameter, including the presence of FVIII-hydrolyzing IgG, has been associated with patient's survival or death. Here, we demonstrate the presence of anti-FIX antibodies in acquired hemophilia patients. IgG from some patients were found to hydrolyze FIX. In most cases, IgG-mediated FIX-hydrolysis resulted in FIX activation. IgG-mediated hydrolysis of FIX thus led to the significant generation of activated FIX in 25 of 65 patients. Based on the estimated kinetic parameters, patients' IgG activated up to 0.3nM FIX in 24 hours, an amount that restored thrombin generation in vitro provided the presence of more than or equal to 3% residual FVIII activity in plasma. This work identifies proteolytic IgG as novel molecules able to activate FIX under pathologic conditions. IgG-mediated FIX activation is a prevalent phenomenon among acquired hemophilia patients. The presence of FIX-activating IgG may partly compensate for the antibody-mediated inhibition of endogenous FVIII in restoring thrombin generation. This clinical trial was registered at www.clinicaltrials.gov as #NCT00213473.

Catalytic antibodies: balancing between Dr. Jekyll and Mr. Hyde

The immunoglobulin molecule is a perfect template for the de novo generation of biocatalytic functions. Catalytic antibodies, or abzymes, obtained by the structural mimicking of enzyme active sites have been shown to catalyze numerous chemical reactions. Natural enzyme analogs for some of these reactions have not yet been found or possibly do not exist at all. Nowadays, the dramatic breakthrough in antibody engineering and expression technologies has promoted a considerable expansion of immunoglobulin's medical applications and is offering abzymes a unique chance to become a promising source of high-precision "catalytic vaccines." At the same time, the discovery of natural abzymes on the background of autoimmune disease revealed their beneficial and pathogenic roles in the disease progression. Thus, the conflicting Dr. Jekyll and Mr. Hyde protective and destructive essences of catalytic antibodies should be carefully considered in the development of therapeutic abzyme applications.

Varied immune response to FVIII: presence of proteolytic antibodies directed to factor VIII in different human pathologies

The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation of the complement and its activation, and activation of effector cells. In addition to this plethora of functions, antibodies are capable of expressing enzymatic activity. Antibodies with catalytic function are a result of the productive interplay between the highly evolved machinery of the immune system and the chemical framework used to induce them (antigens). Catalytic antibodies are immunoglobulins with an ability to catalyze the reactions involving the antigen for which they are specific. Catalytic immunoglobulins of the IgM and IgG isotypes have been detected in the serum of healthy donors. In addition, catalytic immunoglobulins of the IgA isotype have been detected in the milk of healthy mothers. Conversely, antigen-specific hydrolytic antibodies have been reported in a number of inflammatory, autoimmune, and neoplastic disorders. The pathophysiological occurrence and relevance of catalytic antibodies remains a debated issue. Through the description of the hydrolysis of coagulation factor VIII as model target antigen, we propose that catalytic antibodies directed to the coagulation factor VIII may play a beneficial or a deleterious role depending on the immuno-inflammatory condition under which they occur.

Monoclonal antibodies specific to Cucumber mosaic virus coat protein possess DNA-hydrolyzing activity

Monoclonal antibodies (mAbs) specific to Cucumber mosaic virus coat protein (CMV-CP) were designed from cDNA and deduced amino acid sequences of the light chain genes of 10 out of 14 different hybridoma cell lines. Ten of these mAbs revealed a very restricted germline family VkappaII, within which gene bd2 has identical amino acid sequences with VIPase and an i41SL 1-2 catalytic antibody light chain, both of which possess peptidase activity. Four out of the 14 mAbs illustrated another germline family VkappaIA, within which gene bb1.1 had high homology with BV04-01 light chain mAb, which hydrolyses ssDNA. Interestingly, our mAbs showed DNA-hydrolytic activity at an optimum pH of 4-5, which is a typical pattern of autoimmune diseases in which autoantibodies hydrolyze supercoiled plasmid DNA. This is the first evidence ever that CMV-CP could stimulate catalytic antibodies, which have an identical sequence homology with autoantibodies. Furthermore, the CMV-CP-specific mAbs will be important for isolating antibodies specific to the CPs of bacteria, viruses, cancer cells, etc. that could be used for medical therapy.

Detection and characterization of IgG- and sIgA-Abzymes capable of hydrolyzing histone H1

Immunoglobulins IgG and sIgA actively hydrolyzing histone H1 have been detected on analyzing proteolytic activity of antibodies isolated by chromatography on Protein A-agarose from blood serum of patients with multiple sclerosis and from colostrum of healthy mothers. These antibodies hydrolyze other histones less actively and virtually failed to cleave lysozyme of chicken egg. By gel filtration at acidic pH and subsequent analysis of protease activity of chromatographic fractions, it was shown that IgG and sIgA molecules were responsible for hydrolysis of histone H1. Anti-histone H1 antibodies of IgG and sIgA classes were purified by affinity chromatography on histone H1-Sepharose from catalytically active antibody preparations. The protease activity of anti-histone H1 IgG antibodies was inhibited by serine proteinase inhibitors, whereas anti-histone H1 sIgA antibodies were insensitive to inhibitors of serine, asparagine, and cysteine proteases.

Recognition and degradation of myelin basic protein peptides by serum autoantibodies: novel biomarker for multiple sclerosis

The pathologic role of autoantibodies in autoimmune disease is widely accepted. Recently, we reported that anti-myelin basic protein (MBP) serum Abs from multiple sclerosis (MS) patients exhibit proteolytic activity toward the autoantigen. The aim of this study is to determine MBP epitopes specific for the autoantibodies in MS and compare these data with those from other neuronal disorders (OND), leading to the generation of new diagnostic and prognostic criteria. We constructed a MBP-derived recombinant "epitope library" covering the entire molecule. We used ELISA and PAGE/surface-enhanced laser desorption/ionization mass spectroscopy assays to define the epitope binding/cleaving activities of autoantibodies isolated from the sera of 26 MS patients, 22 OND patients, and 11 healthy individuals. The levels of autoantibodies to MBP fragments 48-70 and 85-170 as well as to whole MBP and myelin oligodendrocyte glycoprotein molecules were significantly higher in the sera of MS patients than in those of healthy donors. In contrast, selective reactivity to the two MBP fragments 43-68 and 146-170 distinguished the OND and MS patients. Patients with MS (77% of progressive and 85% of relapsing-remitting) but only 9% of patients with OND and no healthy donors were positive for catalysis, showing pronounced epitope specificity to the encephalitogenic MBP peptide 81-103. This peptide retained its substrate properties when flanked with two fluorescent proteins, providing a novel fluorescent resonance energy transfer approach for MS studies. Thus, anti-MBP autoantibody-mediated, epitope-specific binding and cleavage may be regarded as a specific characteristic of MS compared with OND and healthy donors and may serve as an additional biomarker of disease progression.

Anti-idiotypic antibody mimics proteolytic function of parent antigen

Functional imaging of subtilisin Carlsberg active center by the idiotypic network yielded a catalytic anti-idiotypic antibody with endopeptidase, amidase, and esterase activities. A monoclonal antibody inhibitory to subtilisin (Ab1 5-H4) was employed as the template for guiding the idiotypic network to produce the catalytic anti-idiotypic Ab2 6B8-E12. Proteolytic activity of 6B8-E12 was demonstrated by zymography using self-quenched fluorescein-BSA conjugate and in a coupled assay detecting Ab2-dependent RNase A inactivation. Cleavage of peptide substrates by 6B8-E12 revealed distinct patterns of hydrolysis with high preference for aromatic residues before or after the scissile bond. Catalytic activity of Ab2 was inhibited by phenylmethylsulfonyl fluoride, a mechanism-based inhibitor of serine hydrolases. 5-H4 and 6B8-E12 were cloned, produced in Escherichia coli as single-chain variable fragments (scFvs), and purified. Kinetic parameters for amidolytic and esterolytic activities were similar in Ab2 and its scFv derivative. Although the antigen-specific portion of 6B8-E12 possesses no primary structure similarity to subtilisin, it mimics proteolytic and amidolytic functions of the parental antigen, albeit with 4 orders of magnitude slower acceleration rates. The lack of detectable endopeptidase activity of 6B8-E12 scFv raises interesting issues concerning general evolution of catalytic activity. The in silico 3D models of Ab1 and Ab2 revealed strong structural similarity to known anti-protease antibodies and to abzymes, respectively. These results indicate that the idiotypic network is capable, to a significant extent, of reproducing catalytic apparatus of serine proteases and further validate the use of imaging of enzyme active centers by the immune system for induction of abzymes accelerating energy-demanding amide bond hydrolysis.

Formation of different abzymes in autoimmune-prone MRL-lpr/lpr mice is associated with changes in colony formation of haematopoietic progenitors

It was shown that IgGs from the sera of 2–7-month-old control non-autoimmune (CBA x C57BL)F1 and BALB/c mice and 2–3-month-old autoimmune prone MRL-lpr/lpr mice (conditionally healthy mice) are catalytically inactive. During spontaneous development of deep systemic lupus erythematosus (SLE)-like pathology a specific reorganization of immune system of these mice leads to conditions associated with a production of IgGs hydrolyzing DNA, ATP and polysaccharides with low catalytic activities (conditionally pre-diseased mice).A significant increase in DNase, ATPase and amylase IgG relative activities associated with a transition from pre-diseased to deep diseased mice is correlated with additional changes in differentiation and proliferation of mice bone marrow haematopoietic stem cells (HSCs) and lymphocyte proliferation in different organs.The highest increase in all abzyme activities was found in mice immunized with DNA, which in comparison with pre-diseased and diseased mice are characterized by a different profile of HSC differentiation and by a suppression of cell apoptosis. Abzyme activities in the serum of pregnant females were comparable with those for pre-diseased mice, but the profile of HSC differentiation and cell apoptosis levels in pregnant and pre-diseased mice were quite different. Right after the beginning of lactation (4 days after delivery) and in a late time of lactation (14 days after delivery) there was an observed increase in cell apoptosis and two different stages of significant change in the HSC differentiation profiles; the first stage was accompanied with a significant increase and the second with a remarkable decrease in abzyme activities. Overall, all mouse groups investigated are characterized by a specific relationship between abzyme activities, HSC differentiation profiles, levels of lymphocyte proliferation, and cell apoptosis in different organs. From our point of view, the appearance of ATPase, DNase activities may be considered the earliest statistically significant marker of mouse spontaneous SLE and a further significant increase in their activities correlates with the appearance of SLE visible markers and with an increase in concentrations of anti-DNA Abs and urine protein. However, development of autoimmune (AI)-reactions and the increase in the sera anti-DNA antibodies (Abs) and in the abzyme activities in pregnant and lactating mice do not associate with SLE visible markers and proteinuria. The possible differences in immune system reorganizations during pre-disease, disease, pregnancy and lactation leading to production of different auto-antibodies and abzymes are discussed.

Induction of a protein-targeted catalytic response in autoimmune prone mice: antibody-mediated cleavage of HIV-1 glycoprotein GP120

We have induced a polyclonal IgG that degrades the HIV-1 surface antigen, glycoprotein gp120, by taking advantage of the susceptibility of SJL mice to a peptide-induced autoimmune disorder, experimental autoimmune encephalomyelitis (EAE). Specific pathogen-free SJL mice were immunized with structural fragments of gp120, fused in-frame with encephalitogenic peptide MBP(85-101). It has resulted in a pronounced disease-associated immune response against antigens. A dramatic increase of gp120 degradation level by purified polyclonal IgG from immunized versus nonimmunized mice has been demonstrated by a newly developed fluorescence-based assay. This activity was inhibited by anti-mouse immunoglobulin antibodies as well as by Ser- and His-reactive covalent inhibitors. A dominant proteolysis site in recombinant gp120 incubated with purified polyclonal IgG from immunized mice was shown by SDS-PAGE. The SELDI-based mass spectrometry revealed that these antibodies exhibited significant specificity toward the Pro484-Leu485 peptide bond. The sequence surrounding this site is present in nearly half of the HIV-I variants. This novel strategy can be generalized for creating a catalytic vaccine against viral pathogens.

Autoantibodies to myelin basic protein catalyze site-specific degradation of their antigen

Autoantibody-mediated tissue destruction is among the main features of organ-specific autoimmunity. This report describes "an antibody enzyme" (abzyme) contribution to the site-specific degradation of a neural antigen. We detected proteolytic activity toward myelin basic protein (MBP) in the fraction of antibodies purified from the sera of humans with multiple sclerosis (MS) and mice with induced experimental allergic encephalomyelitis. Chromatography and zymography data demonstrated that the proteolytic activity of this preparation was exclusively associated with the antibodies. No activity was found in the IgG fraction of healthy donors. The human and murine abzymes efficiently cleaved MBP but not other protein substrates tested. The sites of MBP cleavage determined by mass spectrometry were localized within immunodominant regions of MBP. The abzymes could also cleave recombinant substrates containing encephalytogenic MBP(85-101) peptide. An established MS therapeutic Copaxone appeared to be a specific abzyme inhibitor. Thus, the discovered epitope-specific antibody-mediated degradation of MBP suggests a mechanistic explanation of the slow development of neurodegeneration associated with MS.

Hydrolysis of myelin basic protein by polyclonal catalytic IgGs from the sera of patients with multiple sclerosis

Various catalytic antibodies or abzymes have been detected recently in the sera of patients with several autoimmune pathologies, where their presence is most probably associated with autoimmunization. Recently we have shown that DNase, RNase, and polysaccharide-hydrolyzing activities are associated with IgGs from the sera of patients with multiple sclerosis (MS). Here we present evidence demonstrating that highly purified MS IgGs (but not Igs from the sera of healthy individuals) catalyze specifically hydrolysis of human myelin basic protein (hMBP). In contrast to many known proteases, IgGs do not hydrolyze many other different proteins. Specific inhibitors of acidic and thiol proteases have no remarkable effect on proteolytic activity of IgGs. However, specific inhibitor of serine (PMSF, AEBSF, and benzamidin) and metal-dependent (EDTA) proteases significantly inhibit activity of proteolytic abzymes. Interestingly, the ratio of serine-like and metal-dependent activities of MS IgGs varied very much from patient to patient. The findings speak in favor of the generation by the immune systems of individual MS patients of a variety of polyclonal anti-MBP IgGs with different catalytic properties.

Metal-dependent hydrolysis of myelin basic protein by IgGs from the sera of patients with multiple sclerosis

Homogeneous IgG fractions were obtained by chromatography of the sera of patients with multiple sclerosis (MS) on Protein G-Sepharose under conditions that remove non-specifically bound proteins. These IgGs contained several chelated metals, the relative amount of which decreases in the order: Fe>or=Ca>Cu>or=Zn>or=Mg>or=Mn>or=Pb>or=Co>or=Ni. In contrast to homogeneous IgGs of healthy individuals, Abs of MS patients effectively hydrolyzed human myelin basic protein (MBP). A minor metal-dependent fraction was obtained by chromatography of highly purified IgGs from MS patient on Chelex-100. This IgG fraction did not hydrolyze human MBP in the absence of Me(2+) ions but was activated after addition of Me(2+) ions: Mg(2+)>Mn(2+)>Cu(2+)>Ca(2+). Proteolytic activities of IgGs from other MS patients were also activated by other metal ions (Ni(2+), Fe(2+), Co(2+), Zn(2+), Pb(2+), and Co(2+)) and especially Ni(2+). Ni(2+)-activated IgGs were separated into distinct MBP-hydrolyzing fractions by chromatography on HiTraptrade mark Chelating Sepharose charged with Ni(2+). Detection of Mg(2+)-dependent proteolytic activity in the SDS-PAGE area corresponding only to IgG provided direct evidence that IgG from sera of MS patients possesses metal-dependent human MBP-hydrolyzing activity. Observed properties of MS abzymes distinguish them from other known mammalian metalloproteases and demonstrate their pronounced catalytic diversity. Metal-dependent IgGs from MS patients represent the first example of abzymes with metal-dependent proteolytic activity.

Catalytic activity of autoantibodies toward myelin basic protein correlates with the scores on the multiple sclerosis expanded disability status scale

Autoantibodies toward myelin basic protein (MBP) evidently emerge in sera and cerebrospinal fluid of the patients with multiple sclerosis (MS), as well as in a MS rodent model, i.e., experimental autoimmune encephalomyelitis (EAE). The studies of the last two decades have unveiled somewhat controversial data on the diagnostic applicability of anti-MBP autoantibodies as a disease' marker. Here, we present the results of new functional analysis of the anti-MBP autoantibodies isolated from MS (in patients) and EAE (in mice) sera, based on their proteolytic activity against the targeted autoantigen. The activity was shown to be the intrinsic property of the IgG molecule. No activity was found in the sera-derived antibody fraction of healthy donors and control mice. Sera of 24 patients with clinically proven MS at different stages of the disease, and 20 healthy controls were screened for the anti-MBP antibody-mediated proteolytic activity. The activity correlated with the scores on the MS expanded disability status scale (EDSS) (r(2)=0.85, P<0.001). Thus, the anti-MBP autoantibody-mediated proteolysis may be regarded as an additional marker of the disease progression.

Induction of covalent binding antibodies

Covalent interactions between antibody combining site residues and substrates have been implicated in the catalytic activity of abzymes elicited by design or occurring naturally in autoimmune disease. In this study, the potential for covalent binding by antibodies (Abs) was investigated by the induction of immune responses against molecules presenting chemically reactive haptenic groups. Immunogenic conjugates containing a phosphonate diester or a pyruvate carbonyl group were used to elicit antibodies that could specifically react with the electrophilic moieties. Products formed by covalent binding were detected by a western blot technique or by differential ELISA on reduced or unreduced carbonyl haptens. Antisera to the diphenylphosphonate contained antibodies with covalent reactivity, which increased with immunization. The reactivity was specific to the anti-phosphonate response and not to control immune sera induced against the unmodified carrier protein. Reactivity was focused on the antibody light (L) chain. Antisera to the phenylpyruvate hapten appeared to bind strongly to proteins modified by the carbonyl group hapten. However, anti-carrier antisera and non-immune sera had similar reactivity, indicating that the pyruvate moiety reacts nonspecifically with immunoglobulins. This suggested that affinity maturation of antibodies for reversible binding through hemiacetal or Schiff base adducts with antigens requires a less reactive carbonyl in the antigen. On the other hand, the induction of antibodies with enhanced nucleophilic reactivity toward phosphonate esters implies that irreversible binding to the B cell receptor can drive clonal expansion and antibody selection. These results support a designer strategy for generating nucleophilic abzymes and could also account for the occurrence of chemically reactive or catalytic antibodies in natural immunity or autoimmunity.

Role of complementary proteins in autoimmunity: an old idea re-emerges with new twists

It has been suggested that complementary proteins are involved in autoimmunity through a network involving idiotype-anti-idiotype reactions termed 'autoantigen complementarity'. We propose that complementary proteins, which occur naturally or result from cellular dysfunction, might be more common than recognized currently. This implies that the role of complementary proteins in autoimmunity merits increasing investigation. The concept of complementary proteins is reviewed here and, also, new ideas are presented that underscore the role of open-reading frames in frame -1 of recognized genes in the production of complementary proteins (frame -1 is the reverse complement sequence of a gene that uses the antisense of the codons of frame +1). Furthermore, a novel role for palindromic sequences in autoimmunity and a new model explaining how abzymes and autoantigen complementarity might be related are proposed.

Catalytic autoantibodies in multiple sclerosis: Pathogenetic and clinical aspects

The significance of catalytic autoantibodies abzymes in the pathogenesis of multiple sclerosis was evaluated in patients with different disease patterns and severity of disability.

Highlights of frontiers in autoimmunity: fundamental aspects and clinical perspectives

The aim of this meeting, on the shores of Balaton lake, was to discuss the ins, outs, ups and downs of autoimmune diseases. Participants were encouraged to discuss existing paradigms and to base their work on continuously reworked hypotheses derived from discoveries, rather than have it driven by theories based on a hypothesis. This event provided proof of the utility of modern approaches in defining the origin of this group of diseases as well as acting as an international forum for collaboration and dispute. Whilst highlighting the unique aspects of autoimmunity, this meeting suggested many avenues for future research and the design of novel strategies for immuno-intervention.

Idiotypic network mimicry and antibody catalysis: lessons for the elicitation of efficient anti-idiotypic protease antibodies

An important challenge in the field of catalytic antibodies is the generation of antibodies with designed sequence-specific protease activities. Such catalysts would not only be recruited for diverse applications in basic biological science, but could also offer new approaches in biotechnology and medicine. We have previously used the "internal image" property of the idiotypic network to elicit antibodies with efficient esterase and amidase activities. In the present report, we present preliminary results for the production of anti-idiotypic antibodies mimicking subtilisin. A monoclonal inhibitory antibody of subtilisin was characterized and used to elicit anti-idiotypic antibodies. Some of these antibodies exhibit not only an amidase activity against synthetic substrates, but are also able to cleave a protein, bovine serum albumin (BSA).