Autoantibodies against triosephosphate isomerase. A possible clue to pathogenesis of hemolytic anemia in infectious mononucleosis

Metabolic Shades of S-D-Lactoylglutathione

S-D-lactoylglutathione (SDL) is an intermediate of the glutathione-dependent metabolism of methylglyoxal (MGO) by glyoxalases. MGO is an electrophilic compound that is inevitably produced in conjunction with glucose breakdown and is essentially metabolized via the glyoxalase route. In the last decades, MGO metabolism and its cytotoxic effects have been under active investigation, while almost nothing is known about SDL. This article seeks to fill the gap by presenting an overview of the chemistry, biochemistry, physiological role and clinical importance of SDL. The effects of intracellular SDL are investigated in three main directions: as a substrate for post-translational protein modifications, as a reservoir for mitochondrial reduced glutathione and as an energy currency. In essence, all three approaches point to one direction, namely, a metabolism-related regulatory role, enhancing the cellular defense against insults. It is also suggested that an increased plasma concentration of SDL or its metabolites may possibly serve as marker molecules in hemolytic states, particularly when the cause of hemolysis is a disturbance of the pay-off phase of the glycolytic chain. Finally, SDL could also represent a useful marker in such metabolic disorders as diabetes mellitus or ketotic states, in which its formation is expected to be enhanced. Despite the lack of clear-cut evidence underlying the clinical and experimental findings, the investigation of SDL metabolism is a promising field of research.

Seroreactivity against glycolytic enzymes in inflammatory bowel disease

BACKGROUND

Patients with inflammatory bowel disease (IBD) carry autoantibodies such as perinuclear antineutrophil cytoplasmic antibodies. The aim of the current study was to further characterize the immune reactivity in IBD.

METHODS

We used an immunoproteomic approach with extracts from granulocytes and serum from ulcerative colitis (UC) patients and controls to identify target antigens. By means of Western blot analysis, we screened 60 UC and 60 Crohn's disease (CD) patients, 60 diseased, and 60 healthy controls for the antibodies. We performed gene array experiments on RNA extracted from colonic mucosal biopsies from 42 IBD patients and six controls.

RESULTS

We identified aldolase A, phosphoglycerate mutase, alpha-enolase, triose-phosphate isomerase, and malate dehydrogenase as target antigens in IBD. Seroreactivity to at least one of these five antigens was detected in 53.3% of UC patients, 38.3% of CD patients, and 8.3% of controls. Seroreactivity to at least two antigens was detected in 16.7% of UC patients, 11.7% of CD patients, and none of the controls. Gene array experiments showed a significant upregulation of aldolase A, phosphoglycerate mutase, alpha-enolase, and pyruvate kinase mRNA in biopsies from IBD patients, but not controls. UC and CD patients also showed enhanced expression of hypoxia-inducible factor-1, a transcription factor that induces expression of glycolytic enzymes.

CONCLUSIONS

IBD patients show strong seroreactivity toward enzymes involved in the glycolysis. IBD patients also have increased colonic mRNA expression of glycolytic enzymes, which is triggered by hypoxia through the transcription factor HIF-1.

Proteomic surveillance of autoimmunity in osteoarthritis: identification of triosephosphate isomerase as an autoantigen in patients with osteoarthritis

OBJECTIVE

Autoimmunity to proteins, such as type II collagen and cartilage intermediate layer protein, that are produced by chondrocytes has been reported in patients with osteoarthritis (OA) as well as in patients with rheumatoid arthritis (RA). However, it remains to be determined whether the overall specificities of the autoimmunity differ between OA and RA patients. This study sought to clarify the differences by applying proteomic surveillance for the detection of autoantigens comprehensively.

METHODS

Serum samples were obtained from 20 patients with OA, 20 patients with RA, and 20 healthy volunteers. Human chondrocyte proteins were separated from the sera by 2-dimensional electrophoresis, and antigenic protein spots were detected by Western blotting. The antigenic proteins were then identified by mass fingerprinting. The antigenicity of the identified proteins was confirmed and the prevalence of the autoantibodies in the OA, RA, and other disease groups was determined with the use of recombinant proteins. In addition, autoepitopes were mapped on the antigens.

RESULTS

Nineteen protein spots were recognized only by the OA sera, but not by the RA sera. One of these proteins was identified as triosephosphate isomerase (TPI). IgG-type anti-TPI autoantibodies were detected in 24.7% of the serum samples and 24.1% of the synovial fluid samples from the patients with OA, whereas <6% of the RA and systemic lupus erythematosus samples were positive for anti-TPI. In addition, multiple autoepitopes were identified on TPI.

CONCLUSION

The overall profile of autoimmunity in OA differs from that in RA, which may reflect the OA-specific pathologic role of autoimmunity. The autoantibody to TPI, detected predominantly in the OA samples and produced by the antigen-driven mechanism, has the potential to be used as a diagnostic marker for OA.

Oxidative injury to endothelial cells due to Epstein-Barr virus-induced autoantibodies against manganese superoxide dismutase

During the course of acute Epstein-Barr virus (EBV) infection, there is a rise of oxygen radical production. As a consequence, the production of the oxygen radical scavenger manganese superoxide dismutase (MnSOD) is increased. Patients with acute EBV infections regularly develop autoantibodies against MnSOD that are able to inhibit the enzyme activity in vitro. To elucidate the origin of the autoantibodies, the epitopes on MnSOD were determined. The entire sequence of MnSOD was synthesized as overlapping pentadecapeptides, which were scanned for their reactivity with sera of patients with acute EBV infections. Sera as well as affinity-purified anti-MnSOD antibodies reacted with the peptides p(no15) (amino acids 47-61) and p(no30) (amino acids 122-136) lying in crucial parts of the MnSOD tetramer. The two main epitopes p(no15) and p(no30) showed sequence homologies with EBV-encoded proteins. Reactivity of affinity-purified antibodies with a peptide of the homologous BGLF4 points to a molecular mimicry causing the occurrence of anti-MnSOD antibodies. Anti-MnSOD antibodies were able to block the protective effects of MnSOD in a model for oxidative damage produced by xanthine/xanthine oxidase in EAhy926 endothelial cells. Thus, these autoantibodies may contribute in vivo to the clinical symptoms by accumulation of toxic oxygen radicals.

Disease association, origin, and clinical relevance of autoantibodies to the glycolytic enzyme enolase

Serum autoantibodies to the glycolytic enzyme enolase have been reported in a diverse range of inflammatory, degenerative, and psychiatric disorders. Diseases in which these antibodies have been reported in high incidence include autoimmune polyglandular syndrome type 1 (80%, 35 of 44), primary (69%, 60 of 87), and secondary (58%, 14 of 24) membranous nephropathy, cancer-associated retinopathy (68.8%, 11 of 16), autoimmune hepatitis type 1 (60%, 12 of 20), mixed cryoglobulinemia with renal involvement (63.6%, seven of 11), cystoid macular edema (60%, six of 10), and endometriosis (50%, 21 of 41). In autoimmune polyglandular syndrome type 1 patients, all had chronic mucocutaneous candidiasis with demonstrated antibody reactivity to candida enolase, which is suggestive of cross reactivity or epitope mimicry. Formation of autoantibodies to enolase may be a normal process, with reported incidence in apparently healthy subjects ranging from 0% (zero of 91) to 11.7% (seven of 60). Nonetheless, we suggest that excessive production of these autoantibodies, which are generated as a consequence of uptake of enolase by antigen-presenting cells and subsequent B cell activation, can potentially initiate tissue injury as a result of immune complex deposition.

The anaemia of infection

Anaemia is a common finding in infected individuals, and in many cases is an indicator of disease activity and/or duration. The term 'anaemia of infection' refers to a specific syndrome related to the more broadly defined 'anaemia of chronic disease'. In this syndrome, cytokines produced as part of the host response to infection induce anaemia by well-defined pathophysiological mechanisms. In this chapter, the diagnosis, significance, pathophysiology and treatment of the anaemia of infection will be reviewed. Other mechanisms which can produce anaemia in infected individuals will also be reviewed.

Haemolysis in hepatitis A virus infections coinciding with the occurrence of autoantibodies against triosephosphate isomerase and the reactivation of latent persistent Epstein-Barr virus infection

Haemolysis has been observed frequently as a complication of acute hepatitis A virus (HAV) infection. However, the pathogenic mechanism has not been elucidated completely. In individual cases the detection of anti-erythrocyte antibodies of unknown specificity was described. The raised serum IgM fraction was shown to consist partially of autoantibodies. Previously, we detected autoantibodies of immunoglobulin class M directed against triosephosphate isomerase (IgM anti-TPI) in patients with infectious mononucleosis. These autoantibodies are able to induce haemolysis. In this study the occurrence of IgM anti-TPI in acute HAV infections and other viral diseases has been investigated. In 33 of 134 patients suffering from HAV infection (IgM anti-TPI was detected. Haematological and chemical data were available from seven of these 33 patients. Mild-to-moderate signs of haemolysis correlating with the IgM anti-TPI titre in the follow-up examinations were demonstrated. The presence of IgM anti-TPI in HAV infections is connected with a reactivation of a latent persistent EBV infection. In other viral infections both the detection of IgM anti-TPI and evidence of a reactivated EBV infection is rare. Thus, we anticipate that IgM anti-TPI antibodies occurring with the reactivation of a latent persistent EBV infection take part in provoking haemolysis in acute HAV infections.

Manganese superoxide dismutase as a target of autoantibodies in acute Epstein-Barr virus infection

Antibodies directed against the autoantigen p26 were detected in sera from 32 patients with acute Epstein-Barr virus (EBV) infection and clinical symptoms of infectious mononucleosis. P26 has now been identified as the enzyme manganese superoxide dismutase (MnSOD) by comparison of the NH2-terminal amino acid sequence. Antibodies against MnSOD belong to the immunoglobulin class M. They are not detectable in sera of patients with other herpesvirus infections. In the 32 patients investigated, the rise and fall of the autoantibodies coincides with the clinical symptoms. In vitro, the autoantibodies were shown to inhibit the dismutation of superoxide radicals by blocking MnSOD. As presented in the discussion this effect may contribute to the pathogenesis of acute EBV infection.

Hemolysis and autoantibodies to triosephosphate isomerase in a patient with acute hepatitis A virus infection

Having returned from a holiday in Southeast Europe, a 30-year-old German woman developed acute hepatitis. Hepatitis A virus (HAV) infection was diagnosed serologically. During the course of the infection, hemolysis was found. IgM antibodies against triosephosphate isomerase (IgM anti-TPI) were detected in the patient's serum from the acute phase of the HAV infection. Affinity purified IgM anti-TPI from the serum reduced the enzyme activity in vitro and caused an increased 51Cr release from erythrocytes. IgM anti-TPI is assumed to be one of the causative agents of hemolysis in HAV infection.

Prolonged haemolytic anaemia in malaria and autoantibodies against triosephosphate isomerase

Prolonged haemolysis may accompany infection with Plasmodium falciparum. We observed prolonged haemolysis in 4 of 10 patients with this type of malaria after parasitological cure. IgM antibodies specific for the glycolytic enzyme triosephosphate isomerase were detected in these patients' sera. Clinical recovery and a decrease in haemolysis coincided with a fall in these autoantibodies. In vitro, affinity purified autoantibodies isolated from the sera directed against triosephosphate isomerase induced lysis of erythrocytes and activation of complement as shown by the 51Cr release assay. We assume that autoantibodies against triosephosphate isomerase contribute to the development of prolonged haemolysis and anaemia in P falciparum malaria.

Affinity purification of antibodies from sera using polyvinylidenedifluoride (PVDF) membranes as coupling matrices for antigens presented by autoantibodies to triosephosphate isomerase

Polyvinylidenedifluoride (PVDF) membranes covered with antigen can be used for affinity purification of antibodies from sera. These antibodies serve as an appropriate substitute for monoclonal antibodies when performing cytological and analytical experiments with the respective antigen. The usefulness of this method is demonstrated with the purification of IgM autoantibodies produced against human triosephosphate isomerase in acute Epstein-Barr virus infection. Compared with the original serum, the specific activity of the purified antibodies was up to 1400-fold higher, and the recovery of the anti-triosephosphate isomerase activity between 25 and 33%.