Theory and methods for immunization in culture and monoclonal antibody production

Osteoblast lineage-specific cell-surface antigen (A7) regulates osteoclast recruitment and calcification during bone remodeling

Bone remodeling is a continuous process characterized by highly coordinated cell-cell interactions in distinct multi-cellular units. Osteoclasts, which are specialized bone resorbing cells, play a central role in bone remodeling. Although the RANKL/RANK axis determines the gross number of osteoclasts present in bone tissue, detailed molecular events regulating bone remodeling related to osteoclast recruitment, initiation of bone remodeling, and coupling of bone resorption and bone formation are still ambiguous. We hypothesized that osteoblast-specific cell-surface molecules contribute to the molecular modulation of bone remodeling. Therefore, we searched for regulatory cell-surface molecules expressed on osteoblasts by use of B-cell hybridoma technology. We obtained a monoclonal antibody A7 (A7 MAb) highly specific to cells of osteoblast-lineage. Here we describe the expression pattern and possible role of A7 antigen specifically recognized by A7 MAb. In vitro, A7 antigen was expressed on cell-surface of osteoblasts and osteoblast-like bone marrow stromal cells. In vivo, A7 antigen was detected in a subset of bone surface osteoblasts and in osteocytes, with a typical cell membrane expression pattern. Tissue array analysis showed only a limited expression of A7 antigen in osteocytes close to the bone surface. Immunoblotting and immunoprecipitation analysis showed that A7 antigen is a lineage-specific cell-surface protein with an approximate molecular weight of 45 KDa. Cross-linking of cell-surface A7 antigen in cultures of osteoclastogenesis showed stimulation of osteoclast formation. Marked suppression of calcification in primary osteoblast cultures was observed when A7 antigen was cross-linked with anti-A7 antigen MAb, A7 MAb. These data suggest that A7 antigen regulates recruitment of osteoclasts and triggering of calcification. A7 antigen may be an important molecule involved in the precise regulation of bone remodeling.

Blocking the proteolytic activity of zymogen matriptase with antibody-based inhibitors

Matriptase is a member of the type-II transmembrane serine protease (TTSP) family and plays a crucial role in the development and maintenance of epithelial tissues. As all chymotrypsin-like serine proteases, matriptase is synthesized as a zymogen (proform), requiring a cleavage event for full activity. Recent studies suggest that the zymogen of matriptase possesses enough catalytic activity to not only facilitate autoactivation, but also carry out its in vivo functions, which include activating several proteolytic and signaling cascades. Inhibition of zymogen matriptase may therefore be a highly effective approach for limiting matriptase activity. To this end, here we sought to characterize the catalytic activity of human zymogen matriptase and to develop mAb inhibitors against this enzyme form. Using a mutated variant of matriptase in which the serine protease domain is locked in the zymogen conformation, we confirmed that the zymogen form of human matriptase has catalytic activity. Moreover, the crystal structure of the catalytic domain of zymogen matriptase was solved to 2.5 Å resolution to characterize specific antibody-based matriptase inhibitors and to further structure-based studies. Finally, we describe the first antibody-based competitive inhibitors that target both the zymogen and activated forms of matriptase. We propose that these antibodies provide a more efficient way to regulate matriptase activity by targeting the protease both before and after its activation and may be of value for both research and preclinical applications.

Antibody-based inhibition of circulating DLK1 protects from estrogen deficiency-induced bone loss in mice

Soluble delta-like 1 homolog (DLK1) is a circulating protein that belongs to the Notch/Serrate/delta family, which regulates many differentiation processes including osteogenesis and adipogenesis. We have previously demonstrated an inhibitory effect of DLK1 on bone mass via stimulation of bone resorption and inhibition of bone formation. Further, serum DLK1 levels are elevated and positively correlated to bone turnover markers in estrogen (E)-deficient rodents and women. In this report, we examined whether inhibition of serum DLK1 activity using a neutralizing monoclonal antibody protects from E deficiency-associated bone loss in mice. Thus, we generated mouse monoclonal anti-mouse DLK1 antibodies (MAb DLK1) that enabled us to reduce and also quantitate the levels of bioavailable serum DLK1 in vivo. Ovariectomized (ovx) mice were injected intraperitoneally twice weekly with MAb DLK1 over a period of one month. DEXA-, microCT scanning, and bone histomorphometric analyses were performed. Compared to controls, MAb DLK1 treated ovx mice were protected against ovx-induced bone loss, as revealed by significantly increased total bone mass (BMD) due to increased trabecular bone volume fraction (BV/TV) and inhibition of bone resorption. No significant changes were observed in total fat mass or in the number of bone marrow adipocytes. These results support the potential use of anti-DLK1 antibody therapy as a novel intervention to protect from E deficiency associated bone loss.

Three monoclonal antibodies against the serpin protease nexin-1 prevent protease translocation

Protease nexin-1 (PN-1) belongs to the serpin family and is an inhibitor of thrombin, plasmin, urokinase-type plasminogen activator, and matriptase. Recent studies have suggested PN-1 to play important roles in vascular-, neuro-, and tumour-biology. The serpin inhibitory mechanism consists of the serpin presenting its so-called reactive centre loop as a substrate to its target protease, resulting in a covalent complex with the inactivated enzyme. Previously, three mechanisms have been proposed for the inactivation of serpins by monoclonal antibodies: steric blockage of protease recognition, conversion to an inactive conformation or induction of serpin substrate behaviour. Until now, no inhibitory antibodies against PN-1 have been thoroughly characterised. Here we report the development of three monoclonal antibodies binding specifically and with high affinity to human PN-1. The antibodies all abolish the protease inhibitory activity of PN-1. In the presence of the antibodies, PN-1 does not form a complex with its target proteases, but is recovered in a reactive centre cleaved form. Using site-directed mutagenesis, we mapped the three overlapping epitopes to an area spanning the gap between the loop connecting α-helix F with β-strand 3A and the loop connecting α-helix A with β-strand 1B. We conclude that antibody binding causes a direct blockage of the final critical step of protease translocation, resulting in abortive inhibition and premature release of reactive centre cleaved PN-1. These new antibodies will provide a powerful tool to study the in vivo role of PN-1's protease inhibitory activity.

Development of a lipopolysaccharide-targeted peptide mimic vaccine against Q fever

Coxiella burnetii is a Gram-negative bacterium that causes acute and chronic Q fever in humans. Creation of a safe and effective new generation vaccine to prevent Q fever remains an important public health goal. Previous studies suggested that Ab-mediated immunity to C. burnetii phase I LPS (PI-LPS) is protective. To identify the potential peptides that can mimic the protective epitopes on PI-LPS, a PI-LPS-specific mAb 1E4 was generated, characterized, and used to screen a phage display library. Interestingly, our results indicate that 1E4 was able to inhibit C. burnetii infection in vivo, suggesting that 1E4 is a protective mAb. After three rounds of biopanning by 1E4 from the phage display library, a mimetic peptide, m1E41920, was identified, chemically synthesized, and conjugated to keyhole limpet hemocyanin (KLH) for examining its immunogenicity. The results indicate that the synthetic peptide m1E41920 was able to inhibit the binding of 1E4 to PI Ag, suggesting m1E41920 shares the same binding site of 1E4 with the epitopes of PI Ag. In addition, m1E41920-KLH elicited a specific IgG response to PI Ag, and immune sera from m1E41920-KLH-immunized mice was able to inhibit C. burnetii infection in vivo, suggesting that m1E41920 may specifically mimic the protective epitope of PI-LPS. Furthermore, m1E41920-KLH was able to confer significant protection against C. burnetii challenge. Thus, m1E41920-KLH is a protective Ag and may be useful for developing a safe and effective vaccine against Q fever. This study demonstrates the feasibility of developing a peptide mimic vaccine against Q fever.

Variation in FCN1 affects biosynthesis of ficolin-1 and is associated with outcome of systemic inflammation

Ficolin-1 is a recognition molecule of the lectin complement pathway. The ficolin-1 gene FCN1 is polymorphic, but the functional and clinical consequences are unknown.The concentration of ficolin-1 in plasma and FCN1 polymorphisms in positions -1981 (rs2989727), -791 (rs28909068), -542 (rs10120023), -271 (rs28909976), -144 (rs10117466) and +7918 (rs1071583) were determined in 100 healthy individuals. FCN1 expression by isolated monocytes and granulocytes and ficolin-1 levels in monocyte culture supernatants were assessed in 21 FCN1-genotyped individuals. FCN1 polymorphisms were determined in a cohort of 251 patients with systemic inflammation. High ficolin-1 plasma levels were significantly associated with the minor alleles in position -542 and -144. These alleles were also significantly associated with high FCN1 mRNA expression. The level of ficolin-1 in culture supernatants was significantly higher in individuals homozygous for the minor alleles at positions -542 and -144. Homozygosity for these alleles was significantly associated with fatal outcome in patients with systemic inflammation. None of the other investigated polymorphisms were associated with FCN1 and ficolin-1 expression, concentration or disease outcome. Functional polymorphic sites in the promoter region of FCN1 regulate both the expression and synthesis of ficolin-1 and are associated with outcome in severe inflammation.

Development of novel monoclonal antibodies that define differentiation stages of human stromal (mesenchymal) stem cells

Human mesenchymal stem cells (hMSC) are currently being introduced for cell therapy, yet, antibodies specific for native and differentiated MSCs are required for their identification prior to clinical use. Herein, high quality antibodies against MSC surface proteins were developed by immunizing mice with hMSC, and by using a panel of subsequent screening methods. Flow cytometry analysis revealed that 83.5, 1.1, and 8.5% of primary cultures of hMSC were double positive for STRO-1 and either of DJ 3, 9, and 18, respectively. However, none of the three DJ antibodies allowed enrichment of clonogenic hMSC from BMMNCs as single reagents. Using mass-spectrometric analysis, we identified the antigen recognised by DJ3 as CD44, whereas DJ9 and DJ18 recognized HLA-DRB1 and Collagen VI, respectively. The identified proteins were highly expressed throughout in vitro osteogenic- and adipogenic differentiation. Interestingly, undifferentiated cells revealed a sole cytoplasmic distribution pattern of Collagen VI, which however changed to an extracellular matrix appearance upon osteogenic- and adipogenic differentiation. In relation to this, we found that STRO-1(+/-)/Collagen VI(-) sorted hMSC contained fewer differentiated alkaline phosphatase(+) cells compared to STRO-1(+/-)/Collagen VI(+) hMSC, suggesting that Collagen VI on the cell membrane exclusively defines differentiated MSCs. In conclusion, we have generated a panel of high quality antibodies to be used for characterization of MSCs, and in addition our results may suggest that the DJ18 generated antibody against Collagen VI can be used for negative selection of cultured undifferentiated MSCs.

The innate pattern recognition molecule Ficolin-1 is secreted by monocytes/macrophages and is circulating in human plasma

Ficolin-1 (M-Ficolin) is a pattern recognition molecule of the complement system that is expressed by myeloid cells and type II alveolar epithelial cells. Ficolin-1 has been shown to localize in the secretory granules of these cells and attached to cell surfaces, but whether Ficolin-1 exists a soluble molecule in the extracellular environment or in plasma is unknown. In this study we explored the possibility that Ficolin-1 may be secreted from monocytes, macrophages or immature dendritic cells and may exist in human plasma. Expression of Ficolin-1 was analyzed using real-time quantitative PCR and SDS-PAGE/western blot. Secretion of Ficolin-1 was investigated in cells and plasma from healthy donors through affinity purification using N-acetyl-d-glucosamine-agarose beads and ELISA. Ficolin-1 was found differentially expressed and synthesised by monocytes, macrophages and immature dendritic cells. Notably monocytes and macrophages, but not immature dendritic cells are able to secrete Ficolin-1 into the extracellular environment. Moreover, Ficolin-1 was detected in human plasma from healthy donors with a median concentration of 60.5 ng/ml ranging from 45.7 to 100.4 ng/ml. We show that Ficolin-1 is secreted into the extracellular environment from human monocytes/macrophages, but not immature dendritic cells. Importantly, these results demonstrate that Ficolin-1 exists in human plasma and serum under normal conditions, hereby revising the general assumption that Ficolin-1 is solely a cellular associated protein.

Production of monoclonal antibodies against Neisseria meningitidis using popliteal lymph nodes and in vivo/in vitro immunization: prevalence study of new monoclonal antibodies in greater São Paulo, Brazil

A rapid and efficient method for preparing monoclonal antibody (MAb) serotypes using Neisseria meningitidis outer membrane were used in BALB/c mouse footpads for the immunization. The popliteal lymph nodes were isolated 19 days later for MAb-producing hybridomas, from which the MAbs against the 37 kDa protein were screened. Variations in class 2/3 (PorB) proteins form the basis for meningococcal serotyping. This is the first report on the preparation of MAbs against N. meningitidis that is specific to PorB protein using popliteal lymph nodes. The new monoclonal antibodies were specific for PorB outer membrane protein FL24(PL)Br, a new serotype 24 class 3 antigens of non-typeable (NT:NST) serogroup B strain, and FL14(PL)Br specific for the serotype 14, and reacted with the S3446 reference strain analyzed. A total of 12% of the case isolates reacted with one or more of the monoclonal antibodies. The high-affinity MAbs produced by hybridoma methodology provide a basis for further research on the pathogenesis and early diagnosis of meningococcus.

Rapid and efficient preparation of monoclonal antibodies against 35 kDa lipoprotein of Mycoplasma penetrans

To develop a rapid and efficient method for preparing monoclonal antibodies (MAb) against 35 kDa lipoprotein of Mycoplasma penetrans, BALB/c mice were injected into the footpads for immunization, and the popliteal lymph nodes were isolated 19 days later for MAb-producing hybridomas, from which the mAbs against the 35 kDa lipoprotein were screened. The identification of the mAb against the 35 kDa lipoprotein was performed using indirect enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Using popliteal lymph node procedures, we generated several positive clones, one of which we characterized by ELISA and immunoblot. The clone 1D41B8 was identified as the immunoglobulin G1 (IgG1) isotype, kappa chain with affinity constants (Ka) of 2.95 x 10(9) M(-1). The MAbs did not cross-react with a number of control bacteria, which included Mycoplasma fermentans, Mycoplasma hominis, and Mycoplasma genitalium. This is the first report on the preparation of mAbs against M. penetrans that is specific to 35 kDa lipoprotein using popliteal lymph nodes. The high-specificity and high-affinity MAbs produced by two methodologies used of hybridomas provide a basis for further research on the pathogenesis and early diagnosis of M. penetrans. This simple approach may become a method of choice for the generation and production of MAbs in a short period of time.

The impact of FCN2 polymorphisms and haplotypes on the Ficolin-2 serum levels

Ficolin-2 (L-ficolin), derived from the FCN2 gene, is an innate immunity pattern recognition molecule found in human serum in which inter-individual variation in serum appears to be under genetic control. To validate and extend this finding, we developed a sandwich ELISA for detection of human Ficolin-2 in serum samples and identified FCN2 genotypes with a Taq Man-based minor groove binder assay and by sequencing. Serum samples were applied to gel-permeation chromatography and fractions were analysed by an ELISA, SDS-PAGE and subsequently Western blotting. In 214 Danish blood donors, the median Ficolin-2 serum concentration was determined to 5.4 microg/ml (range: 1.0-12.2 microg/ml). An ELISA, SDS-PAGE and Western blot analysis of gel-permeation chromatography fractions showed that Ficolin-2 comprises a mixture of covalently and non-covalently linked Ficolin-2 oligomers independent of the individual genotypes. The variation in serum concentration was associated with three polymorphisms in the promoter and one polymorphism in the structural part of the FCN2 gene. Further analysis indicated that two particular alleles on the same haplotype determined a low Ficolin-2 concentration. Our results show that inter-individual variation of Ficolin-2 concentration is associated with polymorphisms in the promoter and the structural part of the FCN2 gene.

Expression of hiwi gene in human gastric cancer was associated with proliferation of cancer cells

Stem cell genetics research may be critical to our understanding of carcinogenesis, as both stem cells and cancer cells possess the ability to self-renew. Recent discoveries have indicated that the piwi family of genes plays an essential role in stem cell self-renewal in diverse organisms. The hiwi gene, the human homolog of the piwi family, participates in germ cell proliferation and its overexpression may cause the development of germ cell malignancy, but its expression and function in epithelial solid cancers have not been explored. In the present study, we investigated whether there was an association between hiwi expression and human gastric cancer and its potential mechanism. RT-PCR findings demonstrated that hiwi was expressed in different gastric cancer cell lines. To identify the HIWI protein in gastric cancer, we developed a specific monoclonal antibody against HIWI and immunohistochemistry was performed on various gastric tissues. We found that the expression ratio of hiwi in normal gastric tissues, atrophic gastritis, intestinal metaplasia and gastric cancers was 10% (5/50), 36% (18/50), 36% (18/50) and 76% (38/50), respectively, which was consistent with precancerous development. Notably, the expression pattern of hiwi in gastric cancer tissues was similar to that of Ki67, which was used as a marker of proliferation. Moreover, the suppression of hiwi by antisense or RNAi inhibited the growth of gastric cancer cells and induced cell cycle arrest in G2/M phase. These results suggest that hiwi may be involved in the development of gastric cancer and is a potential target for cancer therapy.

Monoclonal Antibodies to Esophageal Cancer–Related Gene2 Protein

Esophageal cancer related gene2 (ECRG2) acts as a bi-functional gene associated with regulation of cell growth and death, and plays an important role in carcinogenesis of esophageal cancer. RT-PCR and Northern blot data showed that ECRG2 was expressed in normal esophagus, liver, colon, and lung tissues, but lost or greatly down-regulated in the adjacent and cancerous tissues, especially in esophageal cancer. However, studies of protein have been hampered by the lack of a sensitive and specific antibody. Here, we generated anti-ECRG2 monoclonal antibodies (MAbs) by using c-terminal of ECRG2 peptide as immunogen. Antibodies 8C9c53, 5E3c9, and 3C5c76, are suitable for detecting the ECRG2 on ELISA and Western blot assays, and 1E4c2 and 4B6c41 are suitable for immunofluorescence microscopy. The study also provides novel data about ECRG2 protein expression in the cytoplasm and the possibility of post-translation modification in mammalian cells. Based on these findings, it may be expected that anti-ECRG2 monoclonal antibodies will be valuable tools for research and diagnosis.

Deamidation and cross-linking of gliadin peptides by transglutaminases and the relation to celiac disease

Activation of small intestinal gluten-reactive CD4+ T cells is a critical event in celiac disease. Such cells predominantly recognise gluten peptides in which specific glutamines are deamidated. Deamidation may be catalysed by intestinal tissue transglutaminase (TG2), a protein which is also the main autoantigen in celiac disease. Our aim was to study how the two main catalytic activities of transglutaminase--deamidation and transamidation (cross-linking) of an immunodominant gliadin epitope--are influenced by the presence of acceptor amines in the intestinal mucosa, and thereby contribute to further elucidation of the pathogenetic mechanisms in celiac disease. We prepared monoclonal antibodies, reacting specifically with the non-deamidated epitope QPFPQPQLPYPQPQ-amide and/or the deamidated epitope QPFPQPELPYPQPQ-amide. A solid phase immunoassay combined with gel filtration chromatography was used to analyse deamidation and cross-linking of these peptides to proteins. Our results show that QPFPQPQLPYPQPQ-amide was deamidated when incubated with purified TG2, with fresh mucosal sheets and with mucosal homogenates. Of other transglutaminases tested, only Streptoverticillium transglutaminase was able to generate the deamidated epitope. A fraction of the non-deamidated epitope was cross-linked to proteins, including TG2. The results suggest that intestinal TG2 is responsible for generation of the active deamidated epitope. As the epitope often occurs in a repeat structure, the result may be cross-linking of a deamidated, i.e., activated cell epitope. Alternatively, the deamidation may occur by reversal of the cross-linking reaction. The results provide a basis for the suggestion that binding of a peptide to a protein, in connection to its modification to a T cell epitope, might be a general explanation for the role of TG2 in celiac disease and a possible mechanism for the generation of autoantigens.

High Prevalence of Human Anti‐bovine IgG Antibodies as the Major Cause of False Positive Reactions in Two‐Site Immunoassays Based on Monoclonal Antibodies

A sandwich ELISA for quantification of the endometrial protein PP14 revealed false positive reactions in 81% of male sera (n = 54). The PP14 ELISA was based on two monoclonal antibodies (Mabs) with different epitope specificities--a catcher and a biotinylated indicator. The monoclonal antibodies were purified by protein G affinity chromatography from culture supernatant containing 10% (v/v) fetal calf serum (FCS). Human anti-animal IgG (bovine, mouse, horse, and swine) antibodies and human anti-bovine serum albumin antibodies were measured using an ELISA design, with direct bridging of the solid phase and biotinylated antigens. The false positive reactions were abolished by addition of 1% (v/v) bovine serum to the dilution buffer (DB). Human anti-bovine IgG antibodies (HABIA) were detected in 99 out of 104 sera from blood donors (50 females; 54 males). HABIA levels in male sera (n = 54) were positively correlated to the false positive signals in the PP14 ELISA (r = 0.923; p < 0.0001). Antibodies to IgG from other mammalian species (mouse, horse, and swine) were also detected in the donor sera, but levels and frequencies were lower compared to that of HABIA. Furthermore, HABIA were positively correlated to human anti-bovine serum albumin antibodies in the donor sera (r = 0.639; p < 0.0001; n = 103). HABIA (prevalence 95%) cause false positive reactions due to crossbinding of contaminating bovine IgG and/or crossreaction with mouse IgG in two-site immunoassays. The apparent presence of human anti-mouse IgG antibodies (HAMA), described to create false positive results, may be due to a crossreacting fraction of the polyclonal circulating antibodies against bovine IgG.

Screening for Epitope Specificity Directly on Culture Supernatants in the Early Phase of Monoclonal Antibody Production by an ELISA with Biotin‐Labeled Antigen

This report describes an assay for comparison of epitope specificity in groups of monoclonal antibodies against a given antigen. The only prerequisite is the biotin-labeled antigen. One of the monoclonal antibodies is captured onto a plastic surface via a rabbit anti-mouse Ig, and the other preincubated with biotinylated antigen. When the two antibodies react with the same epitope subsequent binding of the biotin-labeled antigen is abolished (inhibition). In the cases where no inhibition was observed, the two antibodies were considered to react with distinct, independent epitopes. The obvious advantages using this assay, are that it can be performed directly on culture supernatants in the early phase of monoclonal antibody production, and also works for antigens with repetitive epitopes. Moreover, the bonus effect, i.e., a signal in excess of the reference signal when sets of monoclonal antibodies with different epitope specificity are compared, gives a relative measure of affinity.

Targeting the proteome/epitome, implementation of subtractive immunization

Monoclonal antibody technology has generated invaluable tools for both the analytical and clinical sciences. However, standard immunization approaches frequently fail to provide monoclonal antibodies with the desired specificity. Subtractive immunization provides a powerful alternative to standard immunization and allows for the production of truly unique antibodies. With the intent of targeting specific epitopes within the proteome, subtractive immunization has been broadly and successfully implemented for the production of monoclonal antibodies otherwise unobtainable by standard immunization. Subtractive immunization utilizes a distinct immune tolerization approach that can substantially enhance the generation of monoclonal antibodies to desired antigens. The approach is based on tolerizing the host animal to immunodominant or otherwise undesired antigen(s) (tolerogen) that may be structurally or functionally related to the antigen of interest. Tolerization of the host animal can be achieved through one of three methods: High Zone, Neonatal, or Drug-induced tolerization. The tolerized animal is then inoculated with the desired antigen (immunogen) and antibodies generated by the subsequent immune response are screened for the desired antigenic reactivity. Over the past 15 years a large number of investigators have used the subtractive approach with cleverly chosen tolerogen-immunogen combinations and successfully generated uniquely reactive antibodies which are often neutralizing or function-blocking. This review will focus on the implementation of subtractive immunization for the production of antibodies otherwise unobtainable by standard immunization.

A mu-capture immunoassay for detection of human herpes virus-6 (HHV-6) IgM antibodies in human serum

BACKGROUND

Human herpes virus-6 (HHV-6) was first isolated in 1986. It has been shown to cause exanthema subitum and has been associated with various other diseases. HHV-6 infection is widespread, and more than 90% of the population have antibodies against HHV-6 at the age of 2 years. Once acquired, the virus remains latent in the body. This makes it difficult to draw any conclusions about a causal relationship between the demonstration of HHV-6 and a specific disease.

OBJECTIVES

This work was to develop a mu-capture HHV-6 IgM enzyme linked immuno sorbent assay (ELISA) for use in routine diagnosis and for wide scale patient population analysis.

STUDY DESIGN

A mu-capture HHV-6 IgM ELISA was established. A total of 682 sera consisting of 585 sera from Danish blood donors and 97 sera from patients with autoimmune antibodies were analysed in the HHV-6 IGM ELISA. One hundred and ninety-two sera had earlier been analysed for total HHV-6 antibody content in a competitive ELISA, 94 sera were analysed for cytomegalovirus (CMV) IgM and 57 sera for Epstein Barr virus (EBV) antibodies, using different ELISA assays. The results for 12 primary infections with HHV-6 are also reported.

RESULTS

A HHV-6 IgM optical density (OD)-ratio was calculated according to a constant positive control. An empirical cut off of 0.5 HHV-6 IgM OD-ratio was chosen (with regard to the 10 HHV-6 seroconverters), which resulted in a specificity of 97.5% of the HHV-6 IgM ELISA. Two of the three donor sera with HHV-6 IgM OD-ratios more than 1.05 had total HHV-6 antibody titers significantly above the group with IgM OD-ratios below 0.7 consisting with HHV-6 reactivation. There was no cross reactions to EBV or CMV IgM positive sera.

CONCLUSION

The HHV-6 IgM ELISA seems valid to diagnose primary HHV-6 infection in particular in combination with the HHV-6 total antibody assay.

Phase variation analysis of Coxiella burnetii during serial passage in cell culture by use of monoclonal antibodies

Antigenic changes in Coxiella burnetii Nine Mile strain phase I during serial passages in cell culture were analyzed with three groups of monoclonal antibodies (MAbs) against lipopolysaccharide. The MAbs of group 1 did not react with organisms that were passaged over five times, and the MAbs of group 2 did not react with organisms that were passaged over eight times. The MAbs of group 3 reacted with organisms passaged up to 15 times but did not react with phase II cells. These results suggest that C. burnetii could be differentiated into four phase states during phase variation.

Antibody-based diagnostic and therapeutic innovations for human cancer

As adjuvants, antibody-based diagnostic and therapeutic innovations can potentially decrease morbidity and mortality associated with many human malignancies. Current strategies employing genetically modified constructs may improve tumor penetration and increase versatility.

The use of in vitro immunisation, as an adjunct to monoclonal antibody production, may result in the production of hybridomas secreting polyreactive antibodies

The possibility that immortalisation of in vitro immunised splenocytes may result in hybridomas secreting polyreactive antibodies was investigated. A panel of nine murine hybridomas, secreting IgM(kappa) anti-goat immunoglobulin G (anti-GIgG), was produced by immortalising splenocytes that had been immunised in vitro with GIgG. The ability of the corresponding monoclonal antibodies (Mabs) to bind multiple antigens was investigated using two techniques. First, the affinity constants characterising the interactions of each of the nine Mabs with each of a panel of six antigens were determined. Second, the specific anti-GIgG activities of each hybridoma supernatant and its corresponding affinity-purified IgM fraction were determined and compared. In total, these experiments indicated that eight of the nine hybridomas were polyreactive.

Generation of three selenium-containing catalytic antibodies with high catalytic efficiency using a novel hapten design method

A novel strategy for design of haptens that were used to produce catalytic antibodies was developed and three monoclonal antibodies, 3G5, 2F3, and 5C9, were generated using this strategy. These monoclonal antibodies were converted into selenium-containing abzymes by chemically modifying the hydroxyl group of serines followed by sodium hydrogen selenide displacement. These selenium-containing abzymes exhibited remarkable glutathione peroxidase activity, which surpasses the activity of some native glutathione peroxidases. The activities of the selenium-containing abzymes Se-3G5, Se-2F3, and Se-5C9 which catalyzed reduction of hydroperoxides by glutathione were 2.23, 4.20, and 3.79 times that of rabbit liver glutathione peroxidase, respectively. Detailed steady-state kinetics study on Se-2F3 was carried out and the value of k(cat)/K(m) (H(2)O(2)) was found to be 2.11 x 10(7) M(-1) min(-1) which was supposed to be one of the highest among the known catalytic antibodies. The data of association constants and glutathione peroxidase activities of these catalytic antibodies and the steady-state kinetics of Se-2F3 showed that the method might be a remarkably efficient one for generating catalytic antibodies with glutathione peroxidase activity.

A new assay for thyroglobulin concentration in serum using monoclonal antibodies against synthetic peptides

The concentration of thyroglobulin (Tg) measured by radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA) is greatly affected by the presence of anti-Tg autoantibodies in sera. We developed a new assay for detecting Tg in the presence of high concentrations of anti-Tg autoantibodies. A 48-kDa fragment was purified from Tg after treatment with V8 protease. This fragment did not appear to bind to two types of monoclonal antibodies (57Ab and 28D3) against a peptide in the C-terminus (amino acids 2735-2748) of Tg and intact Tg, respectively, by ELISA and Western blot analysis. In contrast, anti-Tg autoantibody or anti-Tg polyclonal antibody reacted well with this fragment. Our new ELISA used 57Ab as a solid phase antibody and 28D3 as a antibody conjugated to horseradish peroxidase. Buffer containing purified 48-kDa fragment was used to neutralize autoantibodies against Tg. With this assay, the recovery of Tg was 84.0-89.6% in normal healthy donors (n=5) in the presence of immunoglobulin G (IgG) purified from sera positive for anti-Tg autoantibody, and 76.2-104.4% in patient sera Grave's disease (n=15). Furthermore, the Tg concentrations in sera from patients with Grave's disease (n=20) ranged from 25 to 526 ng/ml, even though the Tg concentration, as measured by a commercial RIA did not exceed 55 ng/ml. There was good agreement between Tg concentrations measured by new Tg-ELISA and commercial Tg-RIA in sera that were negative for anti-Tg autoantibody. Overall, our new ELISA containing a Tg fragment to neutralize the presence of autoantibodies, showed good sensitivity and precision, and may be useful for routine use. Further investigations with the new assay should allow wider assessment of the prevalence and pattern of thyroid autoimmunity or thyroid neoplasms.

Biochemical characterization of selenium-containing catalytic antibody as a cytosolic glutathione peroxidase mimic

A selenium-containing catalytic antibody (Se-4A4), prepared by converting reactive serine residues of a monoclonal antibody (4A4) raised against a GSH derivative into selenocysteines, acts as a mimic of cytosolic glutathione peroxidase (cGPX). To clarify the mechanism of action of this catalytic antibody, detailed studies on kinetic behaviour and biological activity were carried out. A rate of acceleration (kcat/Km/kuncat) 10(7)-fold that of the uncatalytic reaction is observed. Under similar conditions, the turnover number (kcat) of Se-4A4 is 42% of that of the natural rabbit liver cGPX. The Se-4A4 reaction involves a Ping Pong mechanism, which is the same as that of the natural cGPX. The selenocysteine residue is located in the binding site of the antibody and is shown to be crucial for this activity. Of the thiol compounds tested, only GSH is able to serve as substrate for Se-4A4. It was demonstrated, using the free-radical-damage system (hypoxanthine/xanthine oxidase) of cardiac mitochondria, that Se-4A4 can protect mitochondria from free-radical damage at least 10(4)-fold more effectively than the natural cGPX.

cDNA cloning, recombinant expression and characterization of polypetides with exceptional DNA affinity

Polypeptides remaining tightly associated with isolated genomic DNA are of interest with respect to their potential involvement in the topological organization and/or function of genomic DNA. Such residual DNA-polypeptide complexes were used for raising monoclonal antibodies by in vitro immunization. Screening of a murine lambdagt11 cDNA library with these antibodies released a positive cDNA (MC1D) encoding a 16 kDa polypeptide. The cloned homologous human cDNA (HC1D) was identified in the dbest data base by partial sequence comparison, and it was sequenced full length. The cDNA-derived amino acid sequences comprise nuclear location signals but none of the known DNA-binding motifs. However, the recombinantly expressed proteins show in vitro DNA binding affinities. A polyclonal antiserum to the recombinant MC1D protein immunostains sub-nuclear structures, and it detects a residual 16 kDa polypeptide on western blots of DNA digests. These results support the conclusion that the cloned cDNAs reflect mRNAs encoding one of the chemically-resistant polypeptides which can be detected in isolated genomic DNA by sensitive techniques, e.g. by125Iodine labeling and SDS-PAGE.

Production of a monoclonal antibody by in vitro immunization that recognizes a native chondroitin sulfate epitope in the embryonic chick limb and heart

We report the production of a monoclonal antibody (d1C4) by in vitro immunization that has immunoreactivity with a native chondroitin sulfate epitope in embryonic chick limb and heart. Murine lymphocytes were stimulated by direct exposure to unfixed, unsolubilized precartilage mesenchymal aggregates in high-density micromass culture derived from Stage 22-23 chick limb buds. Specificity of d1C4 reactivity was demonstrated by sensitivity of immunohistochemical staining to pretreatment with chondroitinase ABC or AC, preferential immunoreactivity with chondroitin-6-sulfate glycosaminoglycan (CS-C GAG) in ELISA, and competition of immunohistochemical staining with CS-C GAG. Immunohistochemical analysis of the expression of the d1C4 epitope revealed a striking localization of immunoreactivity in the extracellular matrix (ECM) of precartilage aggregates of chick limb mesenchyme in high-density micromass culture by 16 hr and the prechondrogenic limb core at Stage 23 in vivo. Immunoreactivity in both cultured limb mesenchyme and the embryonic limb continued through differentiation of prechondrogenic condensations into cartilage tissue. In the developing chick heart, d1C4 staining was found throughout the ECM of atrioventricular cushion tissue by Stage 25, but was localized to mesenchyme adjacent to the myocardium in the outflow tract cushions. There was an abrupt demarcation between d1C4-reactive intracardiac mesenchyme and unreactive extracardiac mesenchyme of the dorsal mesocardium in the Stage 22 embryo. This study demonstrates the efficacy of in vitro immunization of lymphocytes for the production of MAbs to native ECM constituents, such as CS-GAGs. Immunohistochemical data utilizing d1C4 suggest that CS-GAGs bearing this epitope may be important in early morphogenetic events leading to cartilage differentiation in the limb and valvuloseptal morphogenesis in the heart.

Soluble haemoglobin is a marker of recent Plasmodium falciparum infections

Monoclonal antibodies (Mab) were raised against haemoglobin (Hb) associated with Plasmodium falciparum protein and used to develop an ELISA, measuring circulating levels of released Hb. This assay was evaluated in different malaria patients in parallel with ELISA assays for C-reactive protein (CRP) and haptoglobin. Levels of Hb were negatively associated with levels of haptoglobin. Increased levels of serum Hb and CRP and decreased levels of haptoglobin were seen in Danish malaria patients. Consecutive studies showed that increased Hb levels were detectable 3-7 days after initiation of treatment probably because of drug induced destruction of infected erythrocytes. Increased levels of CRP were measured 0-3 days after initiation of treatment. The Hb assay was used in an epidemiological study of malaria in an area of Sudan with unstable malaria transmission. The proportion of Sudanese adults with detectable soluble Hb was higher in the rainy season with malaria transmission compared to the dry season. Hb levels in the rainy season were negatively associated with levels of haptoglobin. Most adults had increased levels of soluble Hb and decreased levels of haptoglobin 7 and 30 days after their treatment of P. falciparum malaria compared to the levels during acute disease. Thus, both soluble Hb and haptoglobin appear to be markers of recent P. falciparum infections. Very high levels of CRP protein were measured in some of the malaria patients at the day of treatment while lower levels were recorded 7 and 30 days after treatment. Soluble Hb levels were associated with malariometric parameters in a similar fashion to haptoglobin. The new Mab-based assay for measuring soluble Hb in the peripheral blood of malaria patients may be useful for future epidemiological studies of malaria.

Isolation and characterization of a new member of the scavenger receptor superfamily, glycoprotein-340 (gp-340), as a lung surfactant protein-D binding molecule

We have purified a previously unknown glycoprotein (designated gp-340) from human bronchioalveolar lung washings from a patient with alveolar proteinosis. gp-340 was identified by its calcium-dependent binding to lung surfactant protein D (SP-D) and by its molecular mass of 340 kDa in the reduced state on SDS-polyacrylamide gel electrophoresis (PAGE). gp-340 was purified from the 10,000 x g pellet of the lavage fluid by ion-exchange and gel permeation chromatography. On SDS-PAGE, gp-340 showed an apparent molecular mass of 290 kDa in the unreduced state. On gel chromatography under non-dissociating conditions, the apparent molecular mass of gp-340 was >1000 kDa. The presence of N-linked glycosylation was shown by digestion with N-glycosidase F, which reduced the apparent molecular mass of gp-340 under reducing condition to about 300 kDa. Partial amino acid sequence data showed the presence of scavenger-receptor type domains. Monoclonal and polyclonal antibodies were raised against gp-340, and their specificities were confirmed by Western blotting. The antibodies were used for immunohistochemical localization of gp-340 in the lung, where it was found on the surface of and within alveolar macrophages. Direct binding between gp-340 and SP-D took place at physiological ionic strength, required the presence of calcium, and was not inhibited by maltose. The binding between SP-D and mannan also required the presence of calcium, but this interaction was completely inhibited by maltose. The same binding pattern was seen between gp-340 and recombinant human SP-D composed of the trimeric neck region and three carbohydrate recognition domains. These findings indicate that the binding between gp-340 and SP-D is a protein-protein interaction rather than a lectin-carbohydrate interaction and that the binding to gp-340 takes place via the carbohydrate recognition domain of SP-D. We conclude that gp-340 is a new member of the scavenger-receptor superfamily and likely to be a truncated form of a receptor for SP-D.

Production and characterization of mouse monoclonal antibodies against Afipia felis

A series of 10 monoclonal antibodies reacting with Afipia felis antigens were selected from mice immunized with live organisms of the reference strain ATCC 53690. Immunoblotting against SDS-PAGE-separated A felis sonicate allowed the antibodies to be classified into three groups: 1) 168-4, -6, -7 and -10 reacted with a 53 kDa antigen, 2) 168-1, -3 and -9 reacted with both 53 kDa and 60 kDa antigens, and 3) 168-2, -5 and -9 reacted with other antigens. Antibodies of group 1 did not cross-react with other Afipia species or 36 unrelated bacteria, whereas those of groups 2 and 3 reacted with other Afipia species and some unrelated bacteria. Immunoblots of crossed immunoelectrophoretic patterns of A. felis sonicate against rabbit antiserum showed that antibodies of groups 1 and 2 bound to the same precipitin arcs. Antibodies of group 1 reacted with a species-specific epitope on the 53 kDa antigen, while those of group 2 reacted with other epitopes shared by the 53 kDa and 60 kDa antigens. The binding of antibodies of group 1 to A. felis sonicate was inhibited by post-infection rabbit serum, whereas no inhibition was observed for antibodies of group 2. The species-specific epitope of the 53 kDa antigen and the early appearance of antibodies against this epitope after infection suggest that this antigen can be used in a serodiagnostic test for A. felis infection.

Monoclonal antibodies against human tetranectin, epitope characterization and use in immunohistochemistry

Two IgG2a/kappa- and three IgG1/kappa monoclonal antibodies (MAbs) were produced against human tetranectin (TN): this is the first report of stable hybridomas producing MAbs against TN. All the MAbs reacted with non-conformational epitopes located within amino acid residues 50-181 of the primary sequence. In relative epitope mapping with enzyme immunoassay and isotachophoresis the five MAbs defined two independent epitope groups. One of them is suggested to be immunodominant in rabbits, since MAbs inhibited binding of a polyclonal rabbit antibody. Several combinations of MAbs were suitable for TN-ELISA and two MAbs could be used for immunohistochemical detection of TN in both fresh frozen and paraffin-embedded tissues. The MAbs will facilitate future studies on structure, function, clinical significance and immunolocalization of TN.

A non-denaturing enzyme linked immunosorbent assay with protein preadsorbed onto aluminum hydroxide

A method has been developed which prevents denaturation of proteins used for coating of plastic surfaces in enzyme linked immunosorbent assays (ELISA). The system takes advantage of the use of aluminum hydroxide (Al(OH)3) as an adsorbent for proteins. A model protein has been analyzed. and monoclonal antibodies specific for either the native form or the denatured form of the protein were used to monitor the extent of denaturation. Adsorption of the proteins to Al(OH)3 in carbonate buffer, pH 9.3, before coating the ELISA plate abolished the denaturation otherwise observed after direct adsorption of protein to plastic surfaces. The protection against denaturation was dependent on the buffer system and was not observed when phosphate buffers were used, due to elution of protein from Al(OH)3 or lack of binding to Al(OH)3 in the presence of phosphate. There is evidence that protein adsorbed onto the Al(OH)3 is required for binding of Al(OH)3 onto the plastic surface. This system may be useful in assay systems where discrimination between the native and denatured forms of proteins is important.

Characterization of two ELISAs for NGAL, a newly described lipocalin in human neutrophils

NGAL is a newly described member of the lipocalin protein family, secreted from specific granules of human neutrophils upon activation of the cells. Its ability to bind the bacterial chemotactic formylpeptide FMLP indicates, that NGAL may have modulatory effects on the immune response. We here describe monoclonal and polyclonal antibodies against NGAL, which can be used for Western blotting and immunohistochemistry, and furthermore describe two ELISAs using either exclusively the polyclonal anti-NGAL antibodies or the polyclonal and monoclonal antibodies in combination. The assays are equally specific, reproducible, accurate, and sensitive, with a detection limit of 32 ng/l. The antibodies and assays will be valuable tools in the future investigation of NGAL expression in inflammatory and malignant disorders and in the elucidation of the function of NGAL as a modulator of the inflammatory response.

Monoclonal antibodies recognizing nitrite oxidoreductase of Nitrobacter hamburgensis, N. winogradskyi, and N. vulgaris

Three monoclonal antibodies (MAbs) against nitrite oxidoreductase (NOR) of Nitrobacter hamburgensis were produced. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting analysis of the purified enzyme showed that the MAbs named Hyb 153.1 and Hyb 153.3 both recognized a protein with a molecular mass of 64,000 Da, while Hyb 153.2 recognized a protein with a molecular mass of 115,000 Da. The molecular masses of these proteins are in the same range as those of the proteins of the alpha (115,000-Da) or beta (65,000-Da) subunit of the NOR. By using the antibodies, the amount of NOR was shown to be dependent on the growth conditions. The highest level of NOR was observed in N. hamburgensis when cells were growing mixotrophically. Analysis of whole-cell extracts of N. hamburgensis, N. winogradskyi, and N. vulgaris indicated serological homology of the NORs from these species of the genus Nitrobacter. The immunological analysis enables detection of the key enzyme of the genus Nitrobacter.

Protein structure of fetal antigen 1 (FA1). A novel circulating human epidermal-growth-factor-like protein expressed in neuroendocrine tumors and its relation to the gene products of dlk and pG2

The present paper describes the primary structure, glycosylation and tissue localization of fetal antigen 1 (FA1) isolated from second-trimester human amniotic fluid. FA1 is a single-chained, heterogeneous glycoprotein of 225-262 amino acid residues. FA1 has six well conserved epidermal-growth-factor motifs and contains up to ten O-glycosylation and N-glycosylation sites, six of which are differentially glycosylated. Alignment to the translated sequences of Mus. musculus dlk and human dlk revealed 86% and 99% identity, respectively, to a 259-amino-acid residue overlap, and this high similarity extends with minor corrections to the human adrenal-specific mRNA, pG2 as well. Immunohistochemical analysis demonstrated the presence of FA1 in 10 out of 14 lung tumors containing neuroendocrine elements, and in the placental villi where FA1 was exclusively seen in stromal cells in close contact to the vascular structure. In the pancreas, FA1 co-localized with insulin in the insulin secretory granules of the beta cells within the islets of Langerhans. Our findings suggest that FA1 is synthesized as a membrane anchored protein and released into the circulation after enzymic cleavage, and that circulating FA1 represents the post-translationally modified gene product of human dlk which, in turn, is identical to human adrenal-specific mRNA pG2.

An enzyme-linked immunosorbent assay (ELISA) for detection of Clostridium aldrichii in anaerobiodigesters

Monoclonal antibodies (Mabs) against Clostridium aldrichii were prepared by in vivo and in vitro immunization with whole cells and produced after fusion as ascites in BALB/c mice. An enzyme-linked immunosorbent assay (ELISA) was used to test for specificity and sensitivity of the Mabs to detect Cl. aldrichii. The lower limit for Cl. aldrichii detection in pure and mixed culture with ELISA was 10(5) cells ml-1. Twenty other species of bacteria, including 12 cellulolytic species, were tested for cross-reactivity with the ELISA, but none was detected. The ELISA was used for detection of Cl. aldrichii over a 16-month period in five mesophilic continuously-stirred tank reactors (CSTR) with wood, glucose, sludge or sorghum as substrates. The population of Cl. aldrichii in the poplar wood anaerobic digester effluent was 10(6)-10(7) cells ml-1 over that time. These numbers were confirmed by anaerobic microbiological methods. Results from the ELISA technique were obtained in 36 h vs 3 weeks for culture methods. It is concluded that the ELISA is a useful, time-saving method for identification, detection and quantification of Cl. aldrichii in axenic, mixed culture, and in complex undefined cultures such as those found in anaerobic digesters.

Characterization of monoclonal antibodies to apolipoprotein (a) and development of a chemiluminescent assay for phenotyping apolipoprotein (a) isomorphs

Apo(a) is linked to Lp(a) through non-covalent interactions and disulfide bond with apo B. Monoclonal antibodies were raised to reduced and carboxymethylated apo(a) in order to study apo(a) interaction with apo B and to develop a sensitive immunoassay for apo(a) and Lp(a). Nine antibodies were characterized for overlapping epitopes and for single or multiple binding sites on native Lp(a) or denatured apo(a). All monoclonal antibodies bound to Lp(a) and denatured apo(a) when these preparations were absorbed on polystyrene. In contrast, three antibodies (3D1, 4B4 and 6H9) failed to react with Lp(a) in solution, in a competitive displacement assay. This observation indicates that these epitopes are masked in native Lp(a). Cross-reactivity with plasminogen was noted for only one monoclonal antibody (4B4). An assay of competitive binding to immobilized Lp(a) or apo(a) revealed that four distinct groups of epitopes were recognized by the monoclonal antibodies: (A) 1G7, 3A5 partially overlapping with 8B6, (B) 5C4, 5B10 partially overlapping with 7C1, (C) 3D1 overlapping with 6H9, and (D) 4B4. A double antibody sandwich assay, using homologous and heterologous combinations of monoclonal antibodies, showed that monoclonal antibodies 1G7, 3A5 and 8B6 of group A, and 5C4 and 5B10 of group B recognized multiple epitopes on Lp(a) while all other antibodies (3D1, 6H9, 4B4) recognized single epitopes. Based on reports of others for the sequence of apo(a), deduced from the cDNA of the human apo(a) gene, it is proposed that monoclonal antibodies which recognize multiple epitopes are directed toward the repetitive kringle 4-like domains of apo(a) while those recognizing single epitopes are probably directed to the kringle 5 or the protease-like domain of apo(a). Monoclonal antibodies which recognized repetitive epitopes were used for the development of a highly sensitive chemiluminescent immunoblotting system for detection of apo(a) isomorphs after resolving plasma protein by polyacrylamide (4%) gel electrophoresis in the presence of sodium dodecyl sulfate. Seven relatively common isomorphs were identified and readily resolved as a mixture. The detection limit was 5-10 pg for each apo(a) isomorph. The high sensitivity allowed for the detection of isomorphs present in over 99% of plasma samples despite a wide range of ratios of apo(a) isomorphs.

In vitro immunization of mouse spleen cells for the production of monoclonal IgG1 antibodies using an antigen-specific T helper cell clone (D.10.G4.1)

The in vitro immunization of mouse spleen cells for the production of antigen-specific monoclonal antibodies has been investigated in detail. Using various, previous published in vitro immunization protocols with and without antigen, we were able to show that IgM antibody production was not induced by the antigen. Nevertheless we developed a new in vitro immunization protocol for eliciting antigen-specific monoclonal IgG1 antibodies. Specific antibodies were generated by an antigen-driven immune response which included an immunoglobulin class switch. Co-culture of mouse spleen cells with an activated conalbumin specific T helper cell clone (TH2 D.10.G4.1) in the presence of conalbumin elicited three monoclonal IgG1 antibodies that bound specifically to conalbumin. We conclude that for the in vitro generation of monoclonal antibodies against T cell dependent proteins the addition of antigen activated specific TH2 cell clones is essential.

Immunogenicity of HILDA/LIF either in a soluble or in a membrane anchored form expressed in vivo by recombinant vaccinia viruses

Insertion of various cDNAs in the genome of the vaccinia virus (VV) enables the in vivo and in vitro study of the functional role and/or the immunogenicity of the virally encoded recombinant proteins. We have prepared a recombinant VV expressing the cDNA of the human cytokine HILDA/LIF (human interleukin for DA cells/leukaemia inhibitory factor), and used this virus to immunize mice against this protein, which is very homologous to its murine counterpart (approximately 80% homology). We also constructed and expressed by the same system a chimeric gene encoding the HILDA/LIF protein fused to the 37 COOH-terminal amino-acids of the human decay accelerating factor (DAF). This sequence proved to be sufficient for the targeting of the fusion protein to the cell membrane, where it is linked to the phosphatidylinositols. Both recombinant VVs induced cytokine-specific antibodies in mice as analysed with an ELISA where the recombinant HILDA/LIF was plastic-coated and a cytofluorometric assay where the LIF-DAF molecule was present at the cell surface of stably transfected P815. In the latter case HILDA/LIF remained biologically active suggesting that it was expressed in its native form. The LIF-DAF fusion protein was found to exhibit a better capacity to elicit an antibody response against the native form of the cytokine as detected in cytofluorometric assays. Whatever the recombinant virus used to immunize the mice, the MoAbs obtained were positive either in the ELISA or in the cytofluorometric assays but one, which suggested that the plastic coating induced a conformational change of HILDA/LIF.

Immunohistochemical detection of an enamel protein-related epitope in rat bone at an early stage of osteogenesis

Monoclonal antibody MI315 was produced against hamster tooth germ homogenate by in vitro immunization. It was found that MI315 reacted with enamel matrix, ameloblasts, and bone matrix at an early stage of osteogenesis. Decalcified tissues of rat femurs and mandibles were examined with MI315 using indirect immunofluorescence. In endochondral ossification of femurs, immunoreactivity was found in bone extracellular matrix (ECM) deposited on the surface of the cartilage core of primary spongiosa, but not in the cartilage core itself. In intramembranous ossification of 0-day-old rat mandibles, intense immunofluorescence was detected in bone ECM and a few young osteocytes, but not in osteoblasts. Immunoreactivity in bone ECM of 2-day-old rats decreased and almost disappeared from bone ECM of 4-day-old rats. Although in nondecalcified sections of 0-day-old rats, negligible immunofluorescence was detected in bone ECM which showed positive staining in decalcified tissues, the immunostaining appeared after decalcification using ethylenediaminetetraacetic acid (EDTA). These results indicate that a substance(s), which had a common epitope with an enamel-derived protein(s), existed in immature bone ECM of both endochondral and intramembranous ossification, and that it might be masked by bone mineral. Monoclonal antibody MI315 is a useful tool to investigate the time- and position-specific changes in osteogenesis and amelogenesis.

Production and specificity of poly- and monoclonal antibodies raised against Shewanella putrefaciens

Polyclonal antibodies were raised in rabbits and mice against Shewanella putrefaciens. Murine monoclonal antibodies were produced against the type strain (ATCC 8071) as well as wild type strains isolated from fish products. The specificities of four polyclonal and 12 monoclonal antibodies were tested by dot-blotting, an indirect and a competitive ELISA against 16 Gram-negative strains; including six strains of S. putrefaciens and one strain of Pseudomonas rubescens (NC 10695). All polyclonal antibodies reacted strongly with S. putrefaciens and with Ps. rubescens and cross-reacted with the nine other bacteria (Pseudomonas spp., Aeromonas spp. and Vibrio anguillarum). The monoclonal antibodies could be divided into three groups with different patterns of specificity. The largest group (8 monoclonal antibodies) reacted strongly with S. putrefaciens and with Ps. rubescens and showed only weak reactions with the other strains. The results confirm that Ps. rubescens should be classified as S. putrefaciens.

Effect of murine ascites on the ability of hybridoma cells to produce antibody and proliferate in vitro

Murine ascites has been shown to contain a variety of growth promoting activities. In this study, we examined the effects of ascites fluid on the efficiency of hybridoma production and cell growth. SP2/0 mouse myeloma cells were injected into peritoneal cavities of mice and ascitic fluid was collected. Lymphocytes from mice immunized with porcine growth hormone (pGH) were fused with myeloma cells in a standard hybridization procedure. These cells were then dispensed in 96-well plates in medium containing either 2.5% ascites or 20% fetal calf serum (FCS) and cultured for few days. Supernatants from these cultures were collected and analyzed for anti-pGH antibodies. It was demonstrated that ascites-supplemented medium increased the efficiency in generating specific antibody-secreting hybridomas by 4-fold over FCS-supplemented medium. Furthermore, hybridoma cells were cultured in microtiter plate and found to proliferate in response to ascites in a dose dependent manner. This effect was abolished by prior digestion of ascites with trypsin, indicating its protein nature. B-lymphocyte related cytokines seemed less likely involved because antibodies to IL-4 and IL-6 failed to alter the stimulatory effect of ascites. Ascites was fractionated by FPLC using Superose 12 column and the active moiety was found to be a small m.w. peptide (< 1,000 dalton). Therefore, murine ascites is capable of substituting for conventional FCS in culture medium in the area of hybridoma technology.