Development of an enzyme-linked immunosorbent assay for Bartonella henselae infection detection

Several serological diagnostics rely on enzyme-linked immunosorbent assay (ELISA) to detect bacterial infections. However, for some pathogens, including Bartonella henselae, diagnosis still depends on manually intensive, time-consuming assays including micro-immunofluorescence, Western blotting or indirect immunofluorescence. For such pathogens, there is obviously still a need to identify antigens to establish a reliable, fast and high-throughput assay (Dupon et al. ). We evaluated two B. henselae proteins to develop a novel serological ELISA: a well-known antigen, the 17-kDa protein, and GroEL, identified during this study by a proteomic approach. When serum IgG were tested, the specificity and sensitivity were 76 and 65·7% for 17-kDa, respectively, and 82 and 42·9% for GroEL, respectively. IgM were found to be more sensitive and specific for both proteins: 17-kDa protein, specificity 86·2% and sensitivity 75%; GroEL, specificity 97·7% and sensitivity 45·3%. IgM antibodies were also measured in lymphoma patients and patients with Mycobacterium tuberculosis infection to assess the usefulness of our ELISA to distinguish them from B. henselae infected patients. The resulting specificities were 89·1 and 93·5% for 17-kDa protein and GroEL, respectively. Combining the results from the two tests, we obtained a sensitivity of 82·8% and a specificity of 83·9%. Our work described and validated a proteomic approach suitable to identify immunogenic proteins useful for developing a serological test of B. henselae infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

A reliable serological assay for the diagnosis of Cat Scratch Disease (CSD) - a pathological condition caused by Bartonella henselae infection - has not yet been developed. Such an assay would be extremely useful to discriminate between CSD and other pathologies with similar symptoms but different aetiologies, for example lymphoma or tuberculosis. We investigate the use of two B. henselae proteins - GroEL and 17-kDa - to develop a serological-based ELISA, showing promising results with the potential for further development as an effective tool for the differential diagnosing of B. henselae infection.

Prevention of arthritis by locally synthesized recombinant antibody neutralizing complement component C5

Treatment of patients suffering from chronic diseases such as rheumatoid arthritis with recombinant antibodies is time consuming and fairly expensive and can be associated with side effects due to generalized depletion of the target molecule. We have addressed these issues by developing an alternative approach consisting of the intraarticular injection of a DNA vector encoding for the anti-C5 neutralizing recombinant miniantibody MB12/22. This method allows local production of the antibody in sufficient amount to be effective in preventing joint inflammation in a rat model of antigen-induced arthritis. Injection of the DNA vector in a right knee of normal rats resulted in the production of the minibody detected in the synovial washes by western blot with a strong signal peaking at 3 days after administration. DNA encoding for the minibody was shown for 14 days in the synovial tissue and was undetectable in the controlateral knee and in other organs. The preventive effect of this approach was evaluated in rats receiving a single injection of the vector 3 days before the induction of antigen-induced arthritis and analyzed 3 days later. The treated rats exhibited a lower increase in swelling, associated with a lower number of PMN in the articular washes and reduced deposition of C9 in synovial tissue compared to control rats. These results suggest that treating the inflamed joints with a vector that induces a local production of a neutralizing anti-C5 antibody may represent a useful strategy to inhibit in situ complement activation and to treat patients with monoarthritis. Moreover, this approach may be adopted as a novel therapeutic strategy to prevent monoarthritis as an alternative to local treatment with antibodies commonly used in this form of arthritis, with the advantages of the lower cost and the longer persistence of antibody production.

Treatment of experimental arthritis by targeting synovial endothelium with a neutralizing recombinant antibody to C5

OBJECTIVE

To show that a new recombinant protein (MT07) obtained by fusing a synovial-homing peptide to a neutralizing antibody to C5 can be selectively delivered to inflamed synovium and can effectively control joint inflammation in experimental models of arthritis.

METHODS

Binding of MT07 to human, rat, and mouse synovial tissue was evaluated in vitro by immunofluorescence, and selective localization in the inflamed joints of rats was documented in vivo using time-domain optical imaging. The antiinflammatory effect of MT07 was tested in a rat model of antigen-induced arthritis (AIA) and in a mouse model of collagen antibody-induced arthritis (CAIA).

RESULTS

MT07 was able to bind to samples of inflamed synovium from humans, mice, and rats while failing to recognize uninflamed synovium as well as inflamed mouse lung or rat kidney. In vivo analysis of the biodistribution of MT07 confirmed its preferential homing to inflamed joints, with negligible inhibition of circulating C5 levels. MT07 prevented and resolved established inflammation in a rat model of AIA, as demonstrated by changes in joint swelling, polymorphonuclear cell counts in synovial washes, release of interleukin-6 and tumor necrosis factor α, and tissue damage. A similar therapeutic effect was obtained testing MT07 in a CAIA model.

CONCLUSION

Our findings show that the novel recombinant molecule MT07 has the unique ability to selectively target inflamed joints and to exert local control of the inflammatory process by neutralizing the complement system without interfering with circulating C5 levels. We believe that this approach can be extended to other antiinflammatory drugs currently used to treat patients with rheumatoid arthritis.

RhoB is associated with the anti-angiogenic effects of celiac patient transglutaminase 2-targeted autoantibodies

Celiac patient-derived anti-transglutaminase 2 (TG2) antibodies disturb several steps in angiogenesis, but the detailed molecular basis is not known. Therefore, we here analyzed by microarray technology the expression of a set of genes related to angiogenesis and endothelial cell biology in order to identify factors that could explain our previous data related to vascular biology in the context of celiac disease. To this end, in vitro models using human umbilical vein endothelial cells (HUVECs) or in vivo models of angiogenesis were used. A total of 116 genes were analyzed after treatment with celiac patient autoantibodies against TG2. Compared to treatment with control IgA celiac patient, total IgA induced a consistent expression change of 10 genes, the up-regulation of four and down-regulation of six. Of these genes the up-regulated RhoB was selected for further studies. RhoB expression was found to be up-regulated at both messenger RNA and protein level in response to celiac patient total IgA as well as anti-TG2-specific antibody derived from a celiac patient. Interestingly, down-regulation of RhoB by specific small interfering RNA treatment in endothelial cells could rescue the deranged endothelial length and tubule formation caused by celiac disease autoantibodies. RhoB function is controlled by its post-translational modification by farnesylation. This modification of RhoB required for its correct function can be prevented by the cholesterol lowering drug simvastatin, which was also able to abolish the anti-angiogenic effects of celiac anti-TG2 autoantibodies. Taken together, our results would suggest that RhoB plays a key role in the response of endothelial cells to celiac disease-specific anti-TG2 autoantibodies.

Cryptic genetic gluten intolerance revealed by intestinal antitransglutaminase antibodies and response to gluten-free diet

BACKGROUND AND OBJECTIVE

Antitransglutaminase (anti-TG2) antibodies are synthesised in the intestine and their presence seems predictive of future coeliac disease (CD). This study investigates whether mucosal antibodies represent an early stage of gluten intolerance even in the absence of intestinal damage and serum anti-TG2 antibodies.

METHODS

This study investigated 22 relatives of patients with CD genetically predisposed to gluten intolerance but negative for both serum anti-TG2 antibodies and intestinal abnormalities. Fifteen subjects were symptomatic and seven were asymptomatic. The presence of immunoglobulin A anti-TG2 antibodies in the intestine was studied by creating phage-antibody libraries against TG-2. The presence of intestinal anti-TG2 antibodies was compared with the serum concentration of the intestinal fatty acid-binding protein (I-FABP), a marker for early intestinal mucosal damage. The effects of a 12-month gluten-free diet on anti-TG2 antibody production and the subjects' clinical condition was monitored. Twelve subjects entered the study as controls.

RESULTS

The intestinal mucosa appeared normal in 18/22; 4 had a slight increase in intraepithelial lymphocytes. Mucosal anti-TG2 antibodies were isolated in 15/22 subjects (68%); in particular symptomatic subjects were positive in 13/15 cases and asymptomatic subjects in 2/7 cases (p=0.01). No mucosal antibodies were selected from the controls' biopsies. There was significant correlation between the presence of intestinal anti-TG2 antibodies and positive concentrations of I-FABP (p=0.0008). After a gluten-free diet, 19/22 subjects underwent a second intestinal biopsy, which showed that anti-TG2 antibodies had disappeared in 12/15 (p=0.002), while I-FABP decreased significantly (p<0.0001). The diet resolved both extraintestinal and intestinal symptoms.

CONCLUSIONS

A new form of genetic-dependent gluten intolerance has been described in which none of the usual diagnostic markers is present. Symptoms and intestinal anti-TG2 antibodies respond to a gluten free-diet. The detection of intestinal anti-TG2 antibodies by the phage-antibody libraries has an important diagnostic and therapeutic impact for the subjects with gluten-dependent intestinal or extraintestinal symptoms. Clinical trial number NCT00677495.

Inhibition of transglutaminase 2 enzymatic activity ameliorates the anti-angiogenic effects of coeliac disease autoantibodies

OBJECTIVE

Earlier work has demonstrated that serum autoantibodies from coeliac patients targeted against transglutaminase 2 (TG2) inhibit in vitro angiogenesis. The aim of this study was to establish whether coeliac patient-derived monoclonal TG2-targeted antibodies produced by recombination technology exert similar anti-angiogenic effects to serum-derived coeliac autoantibodies. In addition, we studied whether the monoclonal patient autoantibodies modulate endothelial cell TG2 activity and whether such modulation is related to the anti-angiogenic effects.

MATERIAL AND METHODS

The influence of coeliac patient-derived monoclonal TG2-targeted antibodies on endothelial cell tubule formation was studied using a three-dimensional angiogenic cell culture model. Endothelial cell TG2 enzymatic activity was determined by means of a live-cell enzyme-linked immunosorbent assay.

RESULTS

Coeliac patient-derived monoclonal TG2-targeted antibodies produced by recombination technology inhibited endothelial tubule formation and enhanced the crosslinking activity of TG2. When this enzymatic activity was inhibited using site-directed irreversible TG2 inhibitors in the presence of autoantibodies, in vitro angiogenesis reverted to the control level.

CONCLUSIONS

Since we found a significant negative correlation between endothelial cell angiogenesis and TG2 activity, we suggest that the anti-angiogenic effects of coeliac patient-derived TG2-targeted autoantibodies are exerted by enhanced enzymatic activity of TG2.

Rapid interactome profiling by massive sequencing

We have developed a high-throughput protein expression and interaction analysis platform that combines cDNA phage display library selection and massive gene sequencing using the 454 platform. A phage display library of open reading frame (ORF) fragments was created from mRNA derived from different tissues. This was used to study the interaction network of the enzyme transglutaminase 2 (TG2), a multifunctional enzyme involved in the regulation of cell growth, differentiation and apoptosis, associated with many different pathologies. After two rounds of panning with TG2 we assayed the frequency of ORFs within the selected phage population using 454 sequencing. Ranking and analysis of more than 120 000 sequences allowed us to identify several potential interactors, which were subsequently confirmed in functional assays. Within the identified clones, three had been previously described as interacting proteins (fibronectin, SMOC1 and GSTO2), while all the others were new. When compared with standard systems, such as microtiter enzyme-linked immunosorbant assay, the method described here is dramatically faster and yields far more information about the interaction under study, allowing better characterization of complex systems. For example, in the case of fibronectin, it was possible to identify the specific domains involved in the interaction.

Majority of children with type 1 diabetes produce and deposit anti-tissue transglutaminase antibodies in the small intestine

OBJECTIVE

Anti-tissue transglutaminase (TG2) antibodies are the serological marker of celiac disease. Given the close association between celiac disease and type 1 diabetes, we investigated the production and deposition of anti-TG2 antibodies in the jejunal mucosa of type 1 diabetic children.

RESEARCH DESIGN AND METHODS

Intestinal biopsies were performed in 33 type 1 diabetic patients with a normal mucosal architecture: 14 had high levels (potential celiac disease patients) and 19 had normal levels of serum anti-TG2 antibodies. All biopsy specimens were investigated for intestinal deposits of IgA anti-TG2 antibodies by double immunofluorescence. In addition, an antibody analysis using the phage display technique was performed on the intestinal biopsy specimens from seven type 1 diabetic patients, of whom four had elevated and three had normal levels of serum anti-TG2 antibodies.

RESULTS

Immunofluorescence studies showed that 11 of 14 type 1 diabetic children with elevated levels and 11 of 19 with normal serum levels of anti-TG2 antibodies presented with mucosal deposits of such autoantibodies. The phage display analysis technique confirmed the intestinal production of the anti-TG2 antibodies; however, whereas the serum-positive type 1 diabetic patients showed a preferential use of the VH5 antibody gene family, in the serum-negative patients the anti-TG2 antibodies belonged to the VH1 and VH3 families, with a preferential use of the latter.

CONCLUSIONS

Our findings demonstrate that there is intestinal production and deposition of anti-TG2 antibodies in the jejunal mucosa of the majority of type 1 diabetic patients. However, only those with elevated serum levels of anti-TG2 antibodies showed the VH usage that is typical of the anti-TG2 antibodies that are produced in patients with celiac disease.

Profiling the autoantibody repertoire by screening phage-displayed human cDNA libraries

The advent of the serological identification of antigens by procedures such as cDNA cloning and recombinant protein expression has allowed the direct molecular definition of immunogenic proteins. The phage-display technology provides several advantages over conventional immunoscreening procedures based on plasmid or lambda-phage cDNA libraries. So far, attempts to display open reading frames, such as those encoded by cDNA fragments, on filamentous phages have not been very successful. We managed to develop a strategy based on "folding reporters" which allows filtering out open reading frames from DNA and displaying them on filamentous phages in such a way that they are amenable to subsequent selection or screening. Once the cDNA library of interest is created, phage-display technology is used for selection of novel putative antigens; these are then validated by printing isolated protein on microarray and screening with patients' sera.

Selection and Characterization of a Novel Agonistic Human Recombinant Anti-Trail-R2 Minibody with Antileukemic Activity

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising natural anticancer therapeutic agent because through its “death receptors”, TRAIL-R1 and TRAIL-R2, it induces apoptosis in many transformed tumor cells, but not in the majority of normal cells. Hence, agonistic compounds directed against TRAIL death receptors have the potential of being excellent cancer therapeutic agents, with minimal cytotoxicity in normal tissues. Here, we report the selection and characterization of a new single-chain fragment variable (scFv) to TRAIL-R2 receptor isolated from a human phage-display library, produced as minibody (MB), and characterized for the in vitro anti-leukemic tumoricidal activity. The anti-TRAIL-R2 MB2.23 efficiently and specifically bound to membrane-associated TRAIL-R2 on different leukemic cell lines and could act as a direct agonist in vitro, initiating apoptotic signaling as well as complement-dependent cytotoxicity and antibody-dependent cell cytotoxicity, providing a rationale for further investigations of MB2.23 in anticancer therapy.

In vivo targeting of human neutralizing antibodies against CD55 and CD59 to lymphoma cells increases the antitumor activity of rituximab

An in vivo model of human CD20+ B-lymphoma was established in severe combined immunodeficiency mice to test the ability of human neutralizing miniantibodies to CD55 and CD59 (MB55 and MB59) to enhance the therapeutic effect of rituximab. The miniantibodies contained single-chain fragment variables and the hinge-CH2-CH3 domains of human IgG(1). LCL2 cells were selected for the in vivo study among six B-lymphoma cell lines for their high susceptibility to rituximab-dependent complement-mediated killing enhanced by MB55 and MB59. The cells injected i.p. primarily colonized the liver and spleen, leading to the death of the animals within 30 to 40 days. Thirty percent of mice receiving biotin-labeled rituximab (25 microg) i.p. on days 4 and 11 after cell injection survived to 120 days. Administration of biotin-labeled rituximab, followed by avidin (40 microg) and biotin-labeled MB55-MB59 (100 microg) at 4-h intervals after each injection resulted in the survival of 70% of mice. Surprisingly, 40% of mice survived after the sole injection of avidin and biotin-labeled MB55-MB59, an observation consistent with the in vitro data showing that the miniantibodies induced killing of approximately 25% cells through antibody-dependent cell cytotoxicity. In conclusion, MB55 and MB59 targeted to tumor cells represent a valuable tool to enhance the therapeutic effect of rituximab and other complement-fixing antitumor antibodies.

Anti-idiotypic response in mice expressing human autoantibodies

Celiac disease is an autoimmune illness characterized by intestinal mucosal injury and malabsorption precipitated by dietary exposure to gluten of some cereals. The immune response is based on both cellular and humoral components, although the former seem to be more important in the pathogenesis. The autoantibody response is directed at the enzyme tissue transglutaminase, tTG or TG2, which possibly play a role in the onset of the disease. In this study we sought to develop an animal model in which to analyze the immunological regulation and significance of anti-TG2 antibodies, by expressing specific human single-chain antibody fragments in mice using adeno-associated virus vectors. Upon vector injection in the skeletal muscles, high and persistent systemic levels of anti-TG2 antibodies were obtained. Mice injected with vectors encoding antibodies also recognizing rodent TG2, also developed a strong anti-idiotypic response. This finding raises the question of whether an anti-idiotypic response to anti-TG2 antibodies is a factor associated with celiac disease.

Gluten ataxia: passive transfer in a mouse model

Gluten sensitivity is an autoimmune disease that usually causes intestinal atrophy resulting in a malabsorption syndrome known as celiac disease. However, gluten sensitivity may involve several organs and is often associated with extraintestinal manifestations. Typically, patients with celiac disease have circulating anti-tissue transglutaminase and anti-gliadin antibodies. When patients with gluten sensitivity are affected by other autoimmune diseases, other autoantibodies may arise like anti-epidermal transglutaminase in dermatitis herpetiformis, anti-thyroid peroxidase antibodies in thyroiditis, and anti-islet cells antibodies in type 1 diabetes. The most common neurological manifestation of gluten sensitivity is ataxia, the so-called gluten ataxia (GA). In patients with GA we have demonstrated that anti-gliadin and anti-tissue transglutaminase antibodies cross-react with neurons but that additional anti-neural antibodies are present. The aim of the present article is to review the knowledge on animal models of gluten sensitivity, as well as reviewing the role of anti-neural antibodies in GA.

Using archaeal histones for precise DNA fragmentation

The fragmentation of DNA is a useful procedure for many molecular biology procedures. However, most methods used to fragment DNA are poorly controllable, and cannot be used to create small fragments. We describe a method to generate random DNA fragments of a predictable size to be cloned in expression vectors for the construction of display libraries. The DNA is allowed to form complexes with archaeal histones from Methanothermus fervidus (HMf) and the HMf/DNA core complex is naturally protected from nuclease DNaseI activity, giving rise to DNA fragments of approximately 60 bp and multiples thereof. We found that by varying the wt/wt ratio between DNA and HMf, the concentration of DNA and the incubation time with DNaseI, DNA fragments of desired size can be obtained. This approach should be applicable to the efficient fragmentation of DNA for the construction of phage display polypeptide libraries, as well as any other molecular biology procedures in which small DNA fragments of defined size are required.

Selective therapeutic control of C5a and the terminal complement complex by anti-C5 single-chain Fv in an experimental model of antigen-induced arthritis in rats

OBJECTIVE

To determine the role of the terminal complement complex (TCC) in the development of experimental antigen-induced arthritis (AIA) and the therapeutic effects of human anti-C5 single-chain Fv (scFv).

METHODS

Two different anti-C5 scFv, one that inhibits both release of C5a and assembly of the TCC (TS-A 12/22) and another that selectively blocks formation of the TCC (TS-A 8), were injected at the onset of AIA. The effects of these scFv on disease severity were evaluated for up to 21 days and compared with the effects of injection of an unrelated scFv. AIA was also established in C6-deficient and C6-sufficient PVG rats to obtain further information on the role of the TCC in this model.

RESULTS

TS-A 12/22 and TS-A 8 proved to be equally effective in reducing joint swelling, cell counts and tumor necrosis factor alpha levels in synovial lavage fluids, and the degree of histomorphologic changes compared with the effects of the unrelated scFv. TS-A 12/22 and TS-A 8 prevented the deposition of C9 but not that of C3, confirming the ability of the 2 scFv to neutralize C5. Administration of the 2 anti-C5 scFv after AIA onset also reduced disease severity. In C6-deficient rats with AIA, disease activity was reduced markedly compared with that in C6-sufficient rats.

CONCLUSION

These 2 human anti-C5 scFv could represent potential therapeutic reagents to be used in patients with rheumatoid arthritis. In addition, the finding that TS-A 8 was as effective as TS-A 12/22 in reducing disease severity suggests that the TCC is mainly responsible for the joint inflammation and damage observed in AIA.

Humoral immune response to tissue transglutaminase is related to epithelial cell proliferation in celiac disease

BACKGROUND & AIMS

Tissue transglutaminase (tTG) autoantibodies are markers of celiac disease, and the enzyme is required for several crucial biological processes. The aim of this study was to determine whether these autoantibodies are involved in the pathogenesis of the mucosal lesion typical of celiac disease.

METHODS

Using rhodamine-conjugated phalloidin staining, we evaluated whether tTG antibodies, both commercially available and cloned from patients with celiac disease, cause cytoskeletal changes in Caco-2, MCF7, and NIH 3T3 cells. We monitored cell levels of bromodeoxyuridine incorporation to determine whether tTG autoantibodies are able to induce NIH 3T3 fibroblasts and epithelial mucosal cells into S phase.

RESULTS

Treatment with tTG antibodies caused a dose-dependent increase of membrane ruffling in Caco-2, MCF7, and NIH 3T3 cells. It also dose-dependently induced G(0)-synchronized NIH 3T3 fibroblasts into S phase but did not affect the rate of apoptosis. Similarly, tTG antibodies induced S-phase entry of epithelial cells in cultured intestinal biopsy specimens from patients with celiac disease. They did not affect biopsy specimens from patients without celiac disease.

CONCLUSIONS

Our results suggest that tTG autoantibodies per se, by interacting with the extracellular membrane-bound transglutaminase, may play an important role in epithelial cell proliferation in celiac disease.

Looking for celiac disease: diagnostic accuracy of two rapid commercial assays

BACKGROUND

Early diagnosis and treatment with gluten-free diet reduces mortality and the prevalence of associated disorders in celiac disease (CD). A simple "in the office" test of anti-transglutaminase antibodies might be of great help in first-line screening for CD.

AIMS

We evaluated the sensitivity and specificity of two commercial kits based, respectively, on rapid detection of IgA-IgG anti-human-transglutaminase antibodies (anti-h-tTG) in serum and IgA anti-h-tTG antibody in one drop of whole blood. These assays were compared to a well-established enzyme-linked immunosorbent assay technique.

METHODS

Serum samples were analyzed from 114 biopsy-confirmed celiacs, 120 healthy controls, 20 first-degree relatives of celiacs, and 75 diseased controls. The whole blood samples were analyzed from 51 biopsy-confirmed celiacs and 100 controls.

RESULTS

The serum-based test was positive in all 114 celiacs (sensitivity 100%). Among the controls there were seven healthy blood donors, one first-degree relative, and three diseased controls who tested positive (specificity 94.9%). The blood drop-based assay testing IgA antibodies was positive in 46 of 51 (sensitivity 90.2%), and since three of the five patients testing negative had total IgA deficiency, the sensitivity value can be increased to 95.8%. All 100 controls tested negative (specificity 100%).

CONCLUSIONS

The commercial kits described here produce high values of sensitivity and specificity, offering the general practitioner who suspects a possible case of CD the real possibility to look for anti-h-tTG antibodies in his own medical office during a standard visit at a satisfyingly low cost.

Characterizing monoclonal antibody epitopes by filtered gene fragment phage display

In the present paper, we describe a novel approach to map monoclonal antibody epitopes, using three new monoclonal antibodies that recognize h-TG2 (human transglutaminase 2) as an example. The target gene was fragmented and cloned upstream of an antibiotic-resistance gene, in the vector pPAO2, to select for in-frame polypeptides. After removal of the antibiotic-resistance gene by Cre/Lox recombination, an antigen fragment phage display library was created and selected against specific monoclonal antibodies. Using the h-TG2 fragment library, we were able to identify epitopes. This technique can also be broadly applied to the study of protein-protein interactions.

Controlling complement resistance in cancer by using human monoclonal antibodies that neutralize complement-regulatory proteins CD55 and CD59

Expression of the complement-regulatory proteins (CRP) CD46, CD55 and CD59 represents a strategy used by tumor cells to evade complement-dependent cell cytoxicity stimulated by monoclonal antibodies. We have isolated two single-chain variable fragments (scFv) to CD55 and CD59 from a human phage-display library and from these scFv we have produced two miniantibodies (MB), MB-55 (against CD55) and MB-59 (against CD59), containing the human hinge-CH2-CH3 domains of IgG1. The specificity of the two MB for the corresponding CRP was assessed by ELISA using purified CD46, CD55 and CD59. MB-55 and MB-59 neutralized the inhibitory activity of CD55 and CD59, respectively, restoring the complement-mediated lysis of sheep and guinea pig erythrocytes that was otherwise inhibited by the two CRP. FACS analysis revealed binding of MB-55 and MB-59 to the lymphoma cell line Karpas 422. The two MB induced a two-fold increase in the complement-dependent killing of these cells stimulated by Rituximab, a chimeric anti-CD20 monoclonal antibody. Transfection of HEK293T cells with vectors encoding MB-55 or MB-59 markedly reduced the expression of CD55 and CD59. We conclude that the human antibodies MB-55 and MB-59 may represent a therapeutic tool to increase the complement-dependent killing activity of Rituximab in the treatment of non-Hodgkin's lymphoma.

Characterization of the anti-tissue transglutaminase antibody response in nonobese diabetic mice

Type 1 diabetes mellitus is an autoimmune disorder characterized by destruction of insulin-producing pancreatic beta cells by T lymphocytes. In nonobese diabetic (NOD) mice, a role has been hypothesized for dietary gluten proteins in the onset of diabetes, and because gluten dependence is the major feature of celiac disease, together with production of Abs to the autoantigen tissue transglutaminase (tTG), we looked for the presence of anti-tTG Abs in the serum of NOD mice and, to establish their origin, analyzed the Ab repertoire of NOD mice using phage display Ab libraries. We found significant levels of serum anti-tTG Abs and were able to isolate single-chain Ab fragments to mouse tTG mainly from the Ab libraries made from intestinal lymphocytes and to a lesser extent from splenocytes. Data from NOD mice on a gluten-free diet suggest that the anti-tTG response is not gluten-dependent. The intestinal Ab response to tTG is a feature of NOD mice, but the underlying mechanisms remain obscure.

Dual sugar gut-permeability testing on blood drop in animal models

BACKGROUND

Intestinal permeability is determined by measuring nonmetabolized sugars. In animals, intestinal permeability is determined in urine, using cumbersome and expensive metabolic cages. We developed an HPLC method for determining concentrations of lactulose (L) and L-rhamnose (R) in blood-drop of rabbits and mice, and we compared these results with the procedure based on sugars excreted in urine. We measured the intestinal permeability induced by a fragment (DeltaG) of the zonula occludens toxin which opens the paracellular pathway.

METHODS

The animals received sugar solution and later received the same solution+DeltaG. Five-hour urine collection and timed blood tests were performed after ingestion of sugars. Sugars were measured with HPLC, and the percentage of recovered sugars was expressed as L/R ratio.

RESULTS

At 60 min after administration of sugars, the mean L/R ratio for rabbits and mice was 0.026 and 0.052, respectively. At 60 min after administration of sugars+DeltaG, the mean L/R ratio for rabbits and mice was 0.22 and 0.53. The mean L/R ratio in the urine was 0.023 at basal condition and 0.25 after DeltaG ingestion.

CONCLUSIONS

Testing small serum samples for sugar permeability is effective for monitoring changes in permeability of the gut in animals. This cheap simple method allows us to measure in vivo the biological activity of other molecules which modulate the paracellular pathway.

Mass screening for coeliac disease using antihuman transglutaminase antibody assay

AIMS

To determine coeliac disease prevalence by an anti-transglutaminase antibody assay in a large paediatric population; to evaluate acceptance of the screening programme, dietary compliance, and long term health effects.

METHODS

Cross-sectional survey of 3188 schoolchildren (aged 6-12) and prospective follow up of diagnosed cases. Main outcome measures were: prevalence of coeliac disease defined by intestinal biopsy or positivity to both human tissue transglutaminase and anti-endomysium antibodies in HLA DQ2-8 positive subjects; percentage of children whose families accepted screening; dietary compliance as defined by negativity for anti-transglutaminase antibodies; and presence of clinical or laboratory abnormalities at 24 month follow up.

RESULTS

The families of 3188/3665 children gave their consent (87%). Thirty biopsy proven coeliacs were identified (prevalence 1:106). Three other children testing positive for both coeliac related autoantibodies and HLA DQ2-8 but refusing biopsy were considered as having coeliac disease (prevalence 1:96). Of 33 cases, 12 had coeliac related symptoms. The 30 biopsy proven coeliacs followed a gluten-free diet. Of 28 subjects completing 18-24 months follow up, 20 (71.4%) were negative for anti-transglutaminase antibodies, while eight were slightly positive; symptoms resolved in all 12 symptomatic children.

CONCLUSIONS

Prevalence of coeliac disease is high in Italian schoolchildren. Two thirds of cases were asymptomatic. Acceptance of the programme was good, as was dietary compliance. Given the high prevalence and possible complications of untreated coeliac disease, the availability of a valid screening method, and evidence of willingness to comply with dietary treatment population mass screening deserves careful consideration.

One-step cloning of anti tissue transglutaminase scFv from subjects with celiac disease

Celiac disease is characterized by intestinal mucosal injury and malabsorption precipitated by dietary exposure to gluten of some cereals with a prominent role being played by gliadins, specific antigenic determinants found in wheat gluten. Patients suffering from celiac disease have serum antibodies recognizing gliadin, as well as the endomysial autoantigen tissue transglutaminase. Phage display antibody libraries have revealed ectopic production of anti-transglutaminase antibodies by intestinal lymphocytes with a biased use of the VH5 antibody gene family. Here we report a study on the pairing of VH and VL families in the antibodies to transglutaminase. Our results led to the construction of small phage display antibody libraries based on the amplification of the two genes in the VH5 family from intestinal lymphocytes. This method can be used for the rapid characterization of the anti-transglutaminase response in a potentially large number of subjects including asymptomatic patients whose serum antibodies may be undetectable.

Celiac disease in patients with sporadic and inherited cardiomyopathies and in their relatives

AIMS

To investigate celiac disease (CD) and related co-morbidity in patients with familial and sporadic cardiomyopathy and in their relatives.

METHODS AND RESULTS

We screened anti-human-tissue-transglutaminase (IgA and IgG anti-h-tTG) and anti-endomysial antibodies (AEAs) in 238 consecutive adult patients with inherited or sporadic dilated cardiomyopathy (DCM), 418 relatives, and 2000 healthy blood donors. HLADQ2-DQ8 was tested in tTG-positive subjects. The IgA-tTG-positive patients with cardiomyopathy underwent duodenal biopsy. Twenty-six subjects were tTG-positive: five DCM patients (2.1%), two of 28 (7.1%) and three of 390 (0.7%) relatives with and without echocardiographic abnormalities respectively, and 16 controls (0.8%). Twenty-two of 26 subjects were AEA-positive, and 25 HLA-positive. Of the five patients with cardiomyopathy and biopsy-proven CD, four suffered iron-deficiency anaemia. Two CD-positive DCM patients and two tTG-positive relatives were from families with inherited disease in which CD did not co-segregate with DCM. CONCLUSIONS; The higher prevalence of CD in patients with sporadic or inherited DCM, and of tTG-positive serology in relatives with echocardiographic abnormalities, suggests that immune-mediated mechanisms are active in subsets of patients/families. However, gluten intolerance cannot be considered causative since CD seems to be associated but not co-segregated with DCM in familial cases.

Antibodies in proteomics II: screening, high-throughput characterization and downstream applications

There are many ways in which the use of antibodies and antibody selection can be improved and developed for high-throughput characterization. Standard protocols, such as immunoprecipitation, western blotting and immunofluorescence, can be used with antibody fragments generated by display technologies. Together with novel approaches, such as antibody chips and intracellular immunization, these methods will yield useful proteomic data following adaptation of the protocols for increased reliability and robustness. To date, most work has focused on the use of standard, well-characterized commercial antibodies. Such protocols need to be adapted for broader use, for example, with antibody fragments or other binders generated by display technologies, because it is unlikely that traditional approaches will provide the required throughput.

Antibodies in proteomics I: generating antibodies

The explosion in genome sequencing, and in subsequent DNA array experiments, has provided extensive information on gene sequence, organization and expression. This has resulted in a desire to perform similarly broad experiments on all the proteins encoded by a genome. Panels of specific antibodies, or other binding ligands, will be essential tools in this endeavour. Because traditional immunization will be unlikely to generate antibodies in sufficient quantity, and of the required quality and reproducibility, in vitro selection methods will probably be used. This review--the first of two--examines the strategies available for in vitro antibody selection. The second review discusses the adaptation of these methods to high throughput and the uses to which antibodies, once derived, can be put.

Selecting open reading frames from DNA

We describe a method to select DNA encoding functional open reading frames (ORFs) from noncoding DNA within the context of a specific vector. Phage display has been used as an example, but any system requiring DNA encoding protein fragments, for example, the yeast two-hybrid system, could be used. By cloning DNA fragments upstream of a fusion gene, consisting of the beta-lactamase gene flanked by lox recombination sites, which is, in turn, upstream of gene 3 from fd phage, only those clones containing DNA fragments encoding ORFs confer ampicillin resistance and survive. After selection, the beta-lactamase gene can be removed by Cre recombinase, leaving a standard phage display vector with ORFs fused to gene 3. This vector has been tested on a plasmid containing tissue transglutaminase. All surviving clones analyzed by sequencing were found to contain ORFs, of which 83% were localized to known genes, and at least 80% produced immunologically detectable polypeptides. Use of a specific anti-tTG monoclonal antibody allowed the identification of clones containing the correct epitope. This approach could be applicable to the efficient selection of random ORFs representing the coding potential of whole organisms, and their subsequent downstream use in a number of different systems.

Predicting antigenic peptides suitable for the selection of phage antibodies

Selection from phage antibody libraries can be considered to be an in vitro immune system in which the antibody response is reduced to the bare minimum of antigen recognition. Using selections of antibodies on peptides from a phage antibody library, we investigated what constitutes peptide antigenicity in the context of the antibody-protein binding site. We selected polyclonal antibodies in a high throughput format against 44% of 90 overlapping peptides derived from three different proteins. Of these, 33% of peptides (epitopic peptides) were able to select antibodies that recognized the protein from which the peptides were derived. Although no algorithm was able to predict all epitopic peptides, solvent accessibility was the best predictor in this cell-free antibody selection context. We subsequently applied solvent accessibility to successfully predict epitopic peptides from p53 and Znf217, and showed that such peptide selected single-chain antibodies were able to recognize soluble p53 in ELISA and Znf217 in a western blot. This is likely to have considerable utility in functional genomics and proteomics where it should be possible to select antibodies against gene products on the basis of deduced amino acid sequence in a high throughput fashion.

The analysis of the fine specificity of celiac disease antibodies using tissue transglutaminase fragments

Celiac disease is an intestinal malabsorption characterized by an intolerance to cereal proteins accompanied by immunological responses to dietary gliadins and an autoantigen located in the endomysium. The latter has been identified as the enzyme tissue transglutaminase which belongs to a family of enzymes that catalyze protein cross-linking reactions and is constitutively expressed in many tissues as well as being activated during apoptosis. In a recent paper, we described the selection and characterization of anti-transglutaminase Igs from phage antibody libraries created from intestinal lymphocytes from celiac disease patients. In this work, using transglutaminase gene fragments, we identify a region of tissue transglutaminase recognized by these antibodies as being conformational and located in the core domain of the enzyme. This is identical to the region recognized by anti-transglutaminase Igs found in the serum of celiac disease patients.

The cleavage site of C5 from man and animals as a common target for neutralizing human monoclonal antibodies: in vitro and in vivo studies

The isolation of an anti-C5 single-chain fragment variable (scFv) antibody, TS-A12/22, from a human phage display library, is described. This antibody inhibits the activation of C5 and the assembly of the terminal complement complex implicated in cell and tissue damage. Using antibody-sensitized sheep erythrocytes and rabbit red cells as target cells in hemolytic assays, we found that TS-A12/22 inhibited the activation of C5 by the convertases of both classical and alternative pathways. Western blot analysis and competition experiments with synthetic peptides showed that TS-A12/22 reacted with the alpha chain of C5 and recognized the cleavage site of this complement component by the C5 convertase. As a result, the antibody prevented splitting of C5 and inhibited the generation of C5a and of the terminal complement complex. The identification of the TS-A12/22 recognition site as a conserved sequence in man, mouse, rat and rabbit enabled the demonstration of in vitro inhibition of complement activity in these species. The scFv TS-A12/22 was tested in a rat model of antigen-induced arthritis and proved to be effective in preventing influx of polymorphonuclear cells into the knee joint and C9 deposition on synovial tissue.

Anti-tissue transglutaminase antibodies from coeliac patients inhibit transglutaminase activity both in vitro and in situ

BACKGROUND AND AIMS

Coeliac disease (CD) is a multifactorial disorder which has an autoimmune component characterised by the occurrence of disease specific autoreactive antibodies against the enzyme tissue transglutaminase (tTG). The aim of this study was to investigate whether binding of antibodies to the enzyme influences tTG activity.

METHODS

tTG activity was assayed in the presence of immunoglobulin A (IgA) and immunoglobulin G (IgG) purified from the serum of coeliac patients, CUB 7402 (an anti-tTG mouse monoclonal antibody), and human anti-tTG monoclonal antibodies derived from both intestinal lymphocytes from three patients with CD and from peripheral blood lymphocytes from healthy subjects. For our studies we used calcium treated and untreated recombinant human tTG. Furthermore, the effects of antibodies were determined by immunohistochemical detection of tTG activity in sections of human umbilical cord.

RESULTS

IgG and IgA from CD patients inhibited tTG activity in vitro in a dose dependent manner, with a different rate of inhibition among patients. The monoclonal antibody CUB 7402 and human monoclonal antibodies displayed a dose dependent inhibitory effect towards the catalytic activity of the enzyme, both in vitro and in situ. Preincubation of tTG with CaCl(2) caused loss of the inhibitory effect due to CUB 7402 but not that caused by human monoclonal antibodies.

CONCLUSIONS

Purified CD IgA, IgG, as well as human anti-tTG monoclonal antibodies inhibited the enzymatic activity of human tTG both in vitro and in situ.

A reliable screening procedure for coeliac disease in clinical practice

BACKGROUND

The main autoantigen recognized by the sera of patients with coeliac disease (CD) is tissue transglutaminase (tTG). A human-recombinant form of tTG was used to develop an ELISA to measure anti-tTG serum antibodies for the diagnosis of CD. Preliminary retrospective reports suggest that the human tTG-based ELISA could identify coeliac patients missed by the IgA-anti-endomysium antibody test (AEA). Whether the human recombinant tTG ELISA is sufficiently accurate to become the main diagnostic CD tool in everyday clinical practice is unknown. The objective was to determine, in a prospective study, the sensitivity and specificity of an ELISA test based on the use of human tTG compared with AEA, to analyse the discordant cases for HLA DQ2-8 and for clinical and intestinal biopsy characteristics.

METHODS

1106 patients referred to a gastrointestinal outpatient clinic for symptoms attributable to CD, 52 first-degree relatives of CD patients and 200 healthy controls were tested for both anti-human tTG and AEA antibodies.

RESULTS

Out of 1158 subjects, 146 were tested positive for anti-tTG antibodies and 140 were biopsy-proven coeliacs. The AEA test identified 126/1158 coeliacs who also tested positive for anti-tTG antibodies. The 14 patients missed by the AEA test carried the typical HLA-DQ for CD; they had normal levels of total serum IgA and had milder pathology than those with both anti-tTG and AEA positivity (P < 0001).

CONCLUSIONS

These results prove that human tTG-based ELISA is an excellent diagnostic tool for CD, for mass screening by both the specialist and the general clinic.

Using phage display in neurobiology

In this unit some of the basic protocols involved in the manipulation of phage display libraries are described, including the rescue and amplification of such libraries, selection and screening from them and testing of derived clones.

Analyzing the peripheral blood antibody repertoire of a celiac disease patient using phage antibody libraries

Celiac disease (CD) is an autoimmune enteropathy characterized by intestinal malabsorption and immunological responses to dietary gliadins and an auto antigen located in the endomysium. The latter has recently been identified as the enzyme tissue transglutaminase (tTG). The linkage between gliadins, tTG and the autoimmune response has still to be clarified. In this work we report the production and analysis of a phage antibody library from the peripheral blood lymphocytes (PLB) of a CD patient. The library contained polyreactive and monoreactive antibodies to alpha-gliadin, to the dietary antigen beta-lactoglobulin, but not to tTG. The majority of the VH regions of the anti-alpha-gliadin antibodies belonged to the VH 4 family. The possibility of exploiting phage display antibodies as tools to study the molecular events associated with CD is discussed.

Antibodies in haystacks: how selection strategy influences the outcome of selection from molecular diversity libraries

Antibodies against most antigens can be isolated from high quality phage antibody libraries. However, not all antibodies binding a particular antigen are necessarily found when standard selections are performed. Here we investigate the effect of two different selection strategies on the isolation of antibodies against a number of different antigens, and find that these different strategies tend to select different antibodies, with little overlap between them. This indicates that the full diversity of these libraries is not tapped by a single selection strategy and that each selection strategy imposes different selective criteria in addition to that of antigen binding. To fully exploit such libraries, therefore, many different selection strategies should probably be employed for each antigen. The use of alternative strategies should be considered when selection apparently fails, or when the number of different antibodies recognizing an antigen needs to be maximised. Furthermore, the microtitre selection strategy developed is likely to prove useful in the application of phage antibody libraries to the human genome project, allowing the high throughput selection of antibodies against multiple antigens simultaneously.