The use of Tween 20 as a blocking agent in the immunological detection of proteins transferred to nitrocellulose membranes

Generation and characterization of murine antiflagellum monoclonal antibodies that are protective against lethal challenge with Pseudomonas aeruginosa

Two murine monoclonal antibodies, IIG5 (IgG3) and IVE8 (IgG2a), that bind to Pseudomonas aeruginosa type a flagella and type b flagella, respectively, were prepared by conventional hybridoma methodology. Specificity of each monoclonal antibody for type a or type b flagella was demonstrated by enzyme-linked immunosorbent assay, indirect immunofluorescence, and immunoblotting. The percentage of P. aeruginosa isolates recognized by each monoclonal antibody was analyzed by enzyme-linked immunosorbent assay. Among a panel of 257 flagellated P. aeruginosa clinical isolates, IIG5 bound to 67.7% of the isolates and IVE8 bound to another 30.7%, for a combined coverage of 98.4%. Inhibition of motility of P. aeruginosa by the monoclonal antibodies was observed in vitro in a soft agar assay and was dose dependent. The protective efficacy of IIG5 and IVE8 was examined in a mouse burn wound sepsis model. The antiflagellum monoclonal antibodies provided specific and significant prophylactic and therapeutic protection against lethal challenge with P. aeruginosa strains.

Evaluation of the ELISA and comparison to the complement fixation test and radial immunodiffusion enzyme assay for detection of antibodies against Mycoplasma hyopneumoniae in swine serum

An enzyme-linked immunosorbent assay (ELISA) was evaluated for detection of antibodies (Ab) against Mycoplasma hyopneumoniae and M. flocculare in sera from swine experimentally infected with these agents. In addition, the ELISA was compared with the complement fixation test (CFT), and radial immunodiffusion enzyme assay (RIDEA) for the demonstration of Ab against M. hyopneumoniae. Twenty two 6-week-old swine from a respiratory disease-free herd were divided into five groups. Two or three pigs from each of the four groups were inoculated, respectively, with M. hyopneumoniae or with M. flocculare while two pigs in each group were contact exposed to the inoculated penmates. A fifth group, consisting of three pigs, served as inoculated controls. Pigs inoculated with M. hyopneumoniae began coughing 13 days post inoculation (PI). Antibodies were first detected 2 weeks PI with the CFT, 3 weeks PI with the ELISA, and 5 weeks PI with the RIDEA. With the ELISA and RIDEA, Ab were still detectable one year PI at a very low level. With the CFT, Ab were not detectable in sera from any swine beyond 5 months PI. At necropsy 1 year PI, no lesions were detected in lungs of any of the animals nor were mycoplasmas detected. M. flocculare inoculated or contact-exposed pigs never evidenced clinical signs. Antibodies against M. flocculare were first detected 5 to 12 weeks PI with CFT, and 6 to 12 weeks PI with the ELISA. Peak optical density (OD) values obtained in the ELISA with M. flocculare Ab were as high as the values obtained with peak M. hyopneumoniae Ab titers. Levels of Ab against M. flocculare were at relatively higher OD at 1 year PI than Ab against M. hyopneumoniae. Sera with high levels of Ab against M. flocculare cross-reacted slightly with M. hyopneumoniae antigen in immunoblotting and ELISA.

Glycoprotein synthesis in the subcommissural organ of the chick embryo. II. An immunochemical study

In the chick embryo, A74 immunoaffinity chromatography allowed to purify specific glycoproteins relevant to the SCO ventricular secretory process. The eluted fractions of the subcommissural organ (SCO), the cerebral hemispheres (CH) and the medulla oblongata (MO) were compared using the Concanavalin A (Con A) and wheat germ agglutinin (WGA) staining procedures after western-blotting. Analysis of the optical density of the reactive bands allowed to estimate the relative concentration of the various glycopeptides in the eluted fractions. In the SCO-eluted fractions at least ten Con A-positive glycopeptides were identified, their apparent molecular weight ranging from 240 to 42 kD. Only three of these appeared to be WGA-positive (98, 88, and 52 kD). In the CH-eluted fractions only a 52 kD Con A- and WGA-positive glycopeptide was revealed, while in the MO-eluted fractions a 32 kD glycopeptide was also Con A- and WGA-positive. These results are discussed in regard to the known biosynthesis pathway of complex type glycoproteins.

Protein blotting: ten years on

Protein blotting was originally described in 1979 as an outgrowth of nucleic acid techniques, and received its commonly used designation of 'Western' blotting in 1981. The use of the technique to render electrophoresed proteins accessible for further analysis has found many roles, the most prominent being subsequent reaction with antibodies or antisera, which has many clinical and research applications. Since the initial development of the system there have been many changes to the techniques involved, but the basic principles remain unaltered. This review discusses these changes, and also provides a summary of current techniques.

Markers for human placental trophoblasts in two-dimensional gel electrophoresis

Primary cultures of trophoblasts established from human term placentae showed high viability and reproducibility. Two-dimensional gel patterns obtained by metabolically labeling the trophoblasts with [35S]-methionine demonstrated that their pattern of gene expression was stable during the 6-d period investigated. Gel analysis demonstrated the keratins 7, 8, 14, 17, 18, and 19. Analysis of the gel pattern confirmed the presence of a small proportion of contaminating fibroblasts and lymphocytes. The gel patterns were compared with that of skin fibroblasts, peripheral lymphocytes, and epithelial cells to identify a group of proteins that are enriched in the trophoblasts and thus may be used as marker for these cells.

Characterization of Streptococcus gordonii (S. sanguis) PK488 adhesin-mediated coaggregation with Actinomyces naeslundii PK606

Intergeneric coaggregation of Streptococcus gordonii (S. sanguis) PK488 and Actinomyces naeslundii PK606 was studied by using coaggregation-defective (Cog-) mutants of both strains. A streptococcal protein of 38 kilodaltons was identified with anti-S. gordonii serum absorbed with Cog- cells of the streptococcus. Absorbed immunoglobulin G specifically blocked coaggregation of the streptococcus-actinomyces pair but did not affect the coaggregation of the streptococcus with other coaggregation partners. The 38-kilodalton protein was found in the supernatant of mild sonicated cell suspensions and was extracted from whole cells with sodium barbital or with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS). An immunoreactive protein of the same size was found in sonicated cell supernatants of several other oral streptococci that also coaggregated with A. naeslundii PK606. Inhibition of S. gordonii PK488-A. naeslundii PK606 coaggregation was not observed with any of 16 different sugars tested. We propose that a functionally similar adhesin that mediates coaggregations with A. naeslundii PK606 is expressed by several species of the genus Streptococcus.

Immunochemical characterization of antigenic domains on human interferon-beta: spatially distinct epitopes are associated with both antiviral and antiproliferative activities

The use of a panel of monoclonal antibodies (mAb) raised against recombinant (serine-17) human interferon-beta (rHuIFN-beta ser) has permitted the identification of three epitopes on HuIFN-beta, designated as sites I, II and III, based solely on functional differences, i.e., the neutralization of antiviral and antiproliferative activities of natural and recombinant HuIFN-beta (Redlich, P.N. and Grossberg, S. E., J. Immunol. 1989. 143: 1887). Site I- and II-directed mAb possessed neutralizing activity whereas none was noted by mAb recognizing site III. To characterize further these epitopes by immunochemical means, we studied their (a) spatial relationship by competitive binding assays, (b) antigenic structure by Western blotting, and (c) sensitivity to chemical modification by the measurement of mAb reactivity after radioiodination. Competitive antibody binding studies revealed site II to be spatially distinct from sites I and III. Furthermore, site I- and II-directed mAb could easily recognize rHuIFN-beta ser on a Western blot, suggesting that both these epitopes are primarily sequential in structure or denaturation resistant. Chemical modification by radioiodination, which did not alter the biologic activity of rHuIFN-beta ser, had likewise little effect on mAb reactivity to site I; however, reactivity to site II was diminished and reactivity to site III was minimal following the radioiodination process. Both site I- and II-directed mAb inhibited the binding of 125I-rHuIFN-beta ser to intact Daudi cells, suggesting that inhibition of receptor binding is their mechanism of neutralization. Thus, we conclude that epitopes I and II, which are associated with both antiviral and antiproliferative activities of rHuIFN-beta, are spatially and immunochemically distinct.

Characterization of fourteen strains of Neisseria gonorrhoeae: structural analyses and serum reactivities

Resistance to normal human serum (NHS) killing in Neisseria gonorrhoeae has been associated with particular types of Protein I (PI) and lipopolysaccharide (LPS), but many exceptions exist, and the role of these structures in determining serum reactivities remains controversial. In reality, the response of the gonococcus to NHS is probably governed by several parameters involving a number of outer-membrane (OM) components. We surveyed the serum reactivities of 14 strains of N. gonorrhoeae and characterized each of their major OM components. The strains presented a spectrum of sensitivity to pooled NHS. As assessed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, immunoblotting, and peptide mapping, the strains were also quite heterogeneous in terms of PI, H.8 antigen, and LPS type, and the presence of the 2-1-L8 epitope. Five of the strains had identical PIAs in varying LPS and H.8 backgrounds, and four had identical PIBs in varying LPS and H.8 backgrounds. As assessed by electrophoretic migration and monoclonal antibody binding, Protein III and the 44,000 Dalton protein were identical in these strains. We found no association between PI subclass and serum sensitivity, while H.8 and LPS variation appeared to be related to bactericidal responses. The diversity and close interaction of gonococcal components in the OM are undoubtedly involved in differential abilities to survive NHS killing.

A radioimmunoassay for antibodies to the Ro/SSA particle

A radioimmunoassay (RIA) for antibodies to the Ro/SSA particle is described using Iodogen to radiolabel the antigenic protein moiety of Ro/SSA with 125I. RIA methods utilizing either 33% saturated ammonium sulfate (NH4)2SO4 or 3.5% polyethylene glycol to separate bound from free antigen are comparable. Either method is similar to ELISA in sensitivity and specificity. This RIA provides a fluid phase assay for the Ro/SSA-anti-Ro/SSA system not previously available.

Efficacy against ovine enzootic abortion of an experimental vaccine containing purified elementary bodies of Chlamydia psittaci

A vaccine prepared from purified, inactivated elementary bodies of Chlamydia psittaci protected sheep against abortion after subcutaneous challenge with live chlamydiae. Immunoblot analysis of serum samples revealed a consistently dominant antibody response against the chlamydial major outer membrane protein in all vaccinated sheep. Reactions to other chlamydial antigens were also detected but were less pronounced or inconsistent. Serological responses detected by complement fixation were variable and did not correlate with immunity.

Morganella morganii urease: purification, characterization, and isolation of gene sequences

Morganella morganii, a very common cause of catheter-associated bacteriuria, was previously classified with the genus Proteus on the basis of urease production. M. morganii constitutively synthesizes a urease distinct from that of other uropathogens. The enzyme, purified 175-fold by passage through DEAE-Sepharose, phenyl-Sepharose, Mono-Q, and Superose 6 chromatography resins, was found to have a native molecular size of 590 kilodaltons and was composed of three distinct subunits with apparent molecular sizes of 63, 15, and 6 kilodaltons, respectively. Amino-terminal analysis of the subunit polypeptides revealed a high degree of conservation of amino acid sequence between jack bean and Proteus mirabilis ureases. Km for urea equalled 0.8 mM. Antiserum prepared against purified enzyme inhibited activity by 43% at a 1:2 dilution after 1 h of incubation. All urease activity was immunoprecipitated from cytosol by a 1:16 dilution. Antiserum did not precipitate ureases of other species except for one Providencia rettgeri strain but did recognize the large subunits of ureases of Providencia and Proteus species on Western blots (immunoblots). Thirteen urease-positive cosmid clones of Morganella chromosomal DNA shared a 3.5-kilobase (kb) BamHI fragment. Urease gene sequences were localized to a 7.1-kb EcoRI-SalI fragment. Tn5 mutagenesis revealed that between 3.3 and 6.6 kb of DNA were necessary for enzyme activity. A Morganella urease DNA probe did not hybridize with gene sequences of other species tested. Morganella urease antiserum recognized identical subunit polypeptides on Western blots of cytosol from the wild-type strain and Escherichia coli bearing the recombinant clone which corresponded to those seen in denatured urease. Although the wild-type strain and recombinant clone produced equal amounts of urease protein, the clone produced less than 1% of the enzyme activity of the wild-type strain.

Purification and characterization of L-dopa decarboxylase from human kidney

L-dopa decarboxylase has been purified to homogeneity from post mortem removed human kidneys. Homogeneity was examined by polyacrylamide gel electrophoresis (PAGE) analysis both in the presence and absence of SDS. The enzyme has a molecular weight of 100,000 daltons estimated by gel filtration and 50,000 daltons determined after SDS-PAGE. Human L-dopa decarboxylase therefore is a dimer. Polyclonal antibodies produced against human L-dopa decarboxylase react with the 50,000 daltons enzyme subunit after immuno-blotting and also precipitates enzyme activity. Activity against L-dopa is partially inhibited by 5-hydroxytryptophan (5-HTP). The effect of various cations on L-dopa decarboxylase activity has also been tested.

Technical problems concerning the use of immunoblots for the detection of antinuclear antibodies

When the immunoblotting technique is used as a diagnostic tool, the reproducibility of the results is a major problem. When purified radiolabelled proteins were applied onto SDS gels, the recovery of radioactivity on the blot after electrophoresis, blotting and incubation ranged from 10 to 65%, depending on the protein. Although the addition of SDS was subsequently shown to improve protein transfer from gel to blot, it is not recommended because immunological recognition of proteins is diminished after this transfer step. We suggest that during the incubation of protein blots detergents are necessary not only to diminish non-specific background, but also to renature proteins. However, since these detergents also elute protein from nitrocellulose and other blotting matrices, they are in part responsible for the lack of reproducibility in immunoblotting results.

Purification and characterization of a Bacteroides loeschei adhesin that interacts with procaryotic and eucaryotic cells

The adhesin of Bacteroides loeschei PK1295 that mediates coaggregation with Streptococcus sanguis 34 and hemagglutination of erythrocytes was purified to electrophoretic homogeneity. The lectinlike protein has an estimated native Mr of 450,000 and consists of six subunits of identical molecular weight (Mr 75,000). The purified adhesin appears to be a basic protein with a pI between 7.4 and 8.0. Amino acid and N-terminal sequence analyses were carried out with the purified protein. These indicated that the protein contains a large number of Asx and Glx residues as well as basic amino acid residues. The binding site of the pure adhesin retained its native configuration during purification. When preincubated with streptococcal partner cells at pH 4.6, the adhesin prevented B. loeschei cells from coaggregating with the streptococci. An adhesin preparation adjusted to a pH of 6.8 rapidly agglutinated both streptococci and neuraminidase-treated erythrocytes. Galactosides inhibited the agglutination reactions.

L-dopa decarboxylase in Ceratitis capitata white puparia and human: a comparative study

1. L-DOPA decarboxylase (DDC) from Ceratitis capitata and from human kidney have been purified by the same methodology. 2. Both enzymes show mol. wts of 100,000, consisting of two identical mol. wt subunits and solely decarboxylate L-DOPA. 3. In the presence of 5-hydroxytryptophan (5-HTP) only the DDC activity from human kidney is remarkably reduced. 4. Addition of exogenous coenzyme is essential only for human DDC activity. 5. Polyclonal antibodies, raised against DDC purified from insects or humans, cross-react with both antigens.

Identification of cytoplasmic soluble antigens related to the major surface antigens of Leishmania braziliensis braziliensis and L. donovani chagasi

This study describes the identification of aqueous-soluble antigens in Leishmania promastigotes immunologically and biochemically closely related to the major surface antigen. Proteins from surface-iodinated L. braziliensis braziliensis and L. donovani chagasi promastigotes, extracted and separated by partitioning in the detergent Triton X-114, were analyzed. Immunoblotting of the extracted proteins, using homologous antisera, showed recognition of a 72-kDa labeled, amphiphilic antigen of L. b. braziliensis and a 65-kDa surface antigen of L. d. chagasi. The respective homologous sera also recognized non-labeled hydrophilic antigens, similar in their apparent molecular weights to the major surface antigens. The amphiphilic and hydrophilic antigens of each species were found to share common antigenic determinants, inasmuch as monospecific antibodies that recognized the amphiphilic protein reacted with the hydrophilic antigen. Structural homology was also obtained in the peptide-digestion profiles of the amphiphilic and the respective hydrophilic major antigens. Zymogram assay showed that both amphibilic and hydrophilic fractions displayed proteolytic activity that could be directly attributed to the major L. b. braziliensis and L. d. chagasi antigens. The hydrophilic antigens found in this study are probably not hydrolytic products of the surface antigens and occur in large quantities in the promastigote cytosol.

Comparative analysis of bovine extracts by immunoblotting and ELISA inhibition. Rabbit and human responses against cow epithelial and urine antigens

Bovine epithelial and urine antigen extracts were compared using enzyme-linked immunosorbent (ELISA) inhibition assay and sodium-dodecyl-sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with immunoblotting. According to ELISA inhibition results, the two extracts share about 2% of their antigenic components. Urine-derived antigens seem to be antigenically closer to serum proteins than epithelial antigens, as determined by rabbit immune sera. The IgG responses of allergic farmers against epithelial antigens were directed mainly against a protein of 20 kD, while non-allergic farmers had only very weak reactions. Generally, the IgG response against urinary antigens seemed to be more heterogeneous than against epithelial antigens. Almost all cow-allergic farmers reacted with a band at 20 kD in IgE immunoblotting against urinary and epithelial antigen while all non-allergic farmers showed negative results.

The use of gold reagents to quantitate antibodies eluted from nitrocellulose blots: application to electron microscopic immunocytochemistry

An assay is described in which gold reagents were used to quantitate nanogram amounts of antibody that had been eluted from antigens immobilized on nitrocellulose paper. Standard curves were generated by the application of rabbit immunoglobulin G (IgG) to nitrocellulose sheets assembled in a dot blot matrix apparatus. Blots were stained using either colloidal gold or immunogold, enabling quantitation of IgG concentration by scanning densitometry. Linear and reproducible standard curves were obtained. As little as 1 ng IgG/dot could be quantified using either gold reagent. In contrast to colloidal gold, immunogold could be used specifically to quantitate rabbit IgG regardless of the presence of bovine serum albumin or antigen coeluted from the nitrocellulose blot. The applicability of the immunogold assay was demonstrated by fractionating a complex rabbit antiserum raised against the RIM protein of frog retinal rod outer segments. Anti-RIM antibody was affinity-purified, quantitated by the immunogold assay, and subsequently employed in immunocytochemical studies using thin sections of retina embedded in a hydrophilic plastic, LR-Gold.

Identification and characterization of peptidoglycan-associated proteins in Neisseria gonorrhoeae

The principal proteins associated with Neisseria gonorrhoeae peptidoglycan (PG), as identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, are the following: two proteins at approximately 90 kilodaltons (kDa), single major species at both 60 and 44 kDa, a 34- to 36-kDa protein, and three proteins between 28 and 32 kDa. A protein analogous to Escherichia coli Braun lipoprotein was not detected with gonococcal cell wall preparations. The identity of the PG-associated proteins was confirmed immunologically with antibody generated against purified cell walls. Two types of protein species, dithiothreitol extractable (the majority) and alkylation dependent (primarily the 34- to 36-kDa protein), appeared to be associated with the N. gonorrhoeae cell wall fraction. It was found that a crucial step in the extraction of the proteins from the PG fraction was the inclusion of an acetone-water wash of the purified PG pellet. Studies with cell wall preparations obtained from N. gonorrhoeae intrinsically labeled with 32P revealed that the acetone wash was removing phospholipid from the cell wall fraction and thus facilitating protein extraction. Autoradiographic analysis with PG material derived from 125I-surface-labeled cells indicated that the 44-kDa protein is exposed on the surface of the organism even when associated with the PG layer. Radioimmunoprecipitation with anti-PG antibody confirmed these findings. Lectin analysis (wheat germ agglutinin conjugated to horseradish peroxidase) suggested that the 34- to 36-kDa protein is covalently attached to the PG layer.

Multiple immunoblot: a sensitive technique to stain proteins and detect multiple antigens on a single two-dimensional replica

A multiple immunoblotting technique was developed to positively identify up to three different antigens on a single nitrocellulose replica of a two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel. Three highly sensitive immunoblot assays were selected, including: horseradish peroxidase/luminescence, alkaline phosphatase, and silver-enhanced immunogold. As a major advantage, the method permits a simultaneous detection of up to three different antigens without eluting the antibody-dye complex between staining of single polypeptides, thus providing a highly accurate identification of closely migrating components. The staining procedure is summarized in a flow chart. In addition to the multiple immunoblot staining, some suggestions are provided for a sensitive protein staining.

Possible members of the potyvirus group transmitted by mites or whiteflies share epitopes with aphid-transmitted definitive members of the group

There are at least ten viruses identified in the literature that resemble definitive potyviruses in having flexuous filamentous particles and inducing the formation of "pinwheel" cytoplasmic inclusions in infected cells but that are transmitted by eriophyid mites, whiteflies or soil fungi and not by aphids, the vectors of the definitive potyviruses. The taxonomic status of these viruses is uncertain at present. Using a broadly cross-reactive antiserum raised against the dissociated coat protein core (residues 68-285) of a definitive potyvirus (Johnsongrass mosaic virus), we have shown that wheat streak mosaic virus which is transmitted by mite and sweet potato mild mottle virus which is transmitted by whitefly have coat proteins that share epitopes with definitive potyviruses. This finding further supports their classification as definitive members of the potyvirus group. The cross-reactive antiserum used here had been shown previously to react with coat proteins of fifteen different definitive potyviruses. The antiserum did not react with coat proteins of potexviruses and tobamoviruses.

Phosphorylation by cell surface protein kinase of bovine and human fibrinogen and fibrin

Human and bovine fibrinogen as well as fibrin are shown to be phosphorylated by Co631 (monolayer, hamster) and RPL12 (suspension, chicken) cells by their surface protein kinase of the casein kinase II type. The phosphate label is introduced into the alpha-peptide. The kinase system phosphorylates serine residues and utilizes GTP equally well as ATP. The participation of intact cell surfaces indicates the possibility of phosphorylation of extracellular fibrinogen independently of the site of its biosynthesis.

Extraction and identification of a 31,000 mol.wt glycoprotein antigen of Ostertagia circumcincta by sera from resistant sheep

Under similar extraction conditions, Triton X-100 sonicates gave higher yields of protein from third stage larvae and adult O. circumcincta than seven other detergents tested. Using sera from sheep which had been experimentally defined by both immunological and parasitological parameters as being either resistant or susceptible to O. circumcincta, a molecule from Triton X-100 extracts of third stage O. circumcincta larvae was identified which reacted preferentially with sera from resistant sheep. This molecule has a molecular weight of 31,000 and preliminary characterization studies revealed it to be a glycoprotein which was not found in later larval stages or adult worms. Antibodies to this 31,000 mol.wt antigen were present in sera of sheep as early as 3 weeks after experimental infection with O. circumcincta.

IgE and IgG antibodies of patients with allergy to birch pollen as tools to define the allergen profile of Betula verrucosa

IgE and IgG antibody response to birch pollen antigens were studied by means of immunoblotting experiments testing 58 sera from patients with Type I allergy to birch pollen. 56/58 patients showed IgE antibodies reactive with Bet v I, a 17 kilodalton (kD) pollen protein. 2D-electrophoresis/immunoblot revealed a heterogeneity of that protein. Ten spots (pH 4.9-5.9) could be detected, presumably representing differentially glycosylated isoallergens. In 33/58 patients, there was no evidence of IgE antibodies directed against allergens other than Bet v I. However, in 25/58 of patients' sera, 11 minor allergens (13, 15, 18, 27, 29, 32, 39, 44, 57, and 68 kD) with individual incidences from 1.7% to 17.2% were identified. All proteins were also recognized by the patients' IgG antibodies: in the case of Bet v I recognition was weak, whereas the IgG response to the minor allergens was pronounced. Sera from healthy individuals showed similar IgG antibody responses, but no IgG to the 15, 27, and 29 kD proteins. Our results suggest that IgG directed against minor allergens may function as trapping antibodies in healthy individuals. Too low or lacking amounts of anti-Bet v I IgG may facilitate an allergic reaction.

Reactivities of immunoglobulin E and immunoglobulin G subclasses identified by isoelectric focusing-immunoprint in allergic patients

Probing of IgE or IgG subclass reactivities on single allergenic components in an extract is tedious and time-consuming under native conditions. Isoelectric focusing immunoblotting combines a powerful, highly resolving native separation method with the specificity and sensitivity of immunological test methods. This method is easy and quick to perform. The potential usefulness of this method is demonstrated by eight examples of a type I or type III allergy analyzing IgE and IgG subclass reactivities and their distribution.

Characterization of Micropolyspora faeni antigens by human antibodies and immunoblot analysis

IgG, IgM and IgA antibody responses against Micropolyspora faeni (Mf) antigens were studied by means of immunoblotting experiments using 70 sera derived from three groups of farmers, namely patients with extrinsic allergic alveolitis (EAA) due to thermophilic actinomycetes (n = 25), patients without EAA but with hay exposure (n = 14), and patients suspected to have EAA (n = 31), and 27 sera from two groups of control persons (healthy laboratory workers, n = 13; healthy farmers, n = 14). Patients with EAA showed IgG, IgM and IgA antibody responses mainly against the antigens with molecular weights (MW) of 11, 12, 25, 35 and 60 kD ("major antigens"), and in addition, but less often, against six antigens with MW in the range of 15 to 62.5 kD ("minor antigens"). The other two groups of patients and also the exposed control persons showed very similar results; however, the antibody response in healthy farmers was substantially weaker in comparison to the three groups of patients and was almost limited to the major antigens with MW 11, 25 and 60 kD. Although patients with proven EAA had higher amounts of antibodies, there was no correlation between this antibody response and the onset of disease. The results indicate the necessity of including at least the major antigens with MW of 11, 25 and 60 kD in all extracts used for in vitro diagnosis of Mf-induced EAA.

A new neomycin phosphotransferase II solid phase assay in combination with polyacrylamide sodium dodecylsulphate gel electrophoresis

A new general method for the determination of neomycin phosphotransferase (NPT) II (EC 2.7.1.95) activity in cell extracts after separation in SDS-polyacrylamide gels is described. The enzymatic activity of NPT II is restored after SDS-polyacrylamide gel electrophoresis by incubating the gel for 3 h (20 mM Tris-HCl buffer, pH 7.4). The enzymatic activity is determined by in situ phosphorylation of aminoglycoside antibiotics bound to solid supports and brought into direct contact with the gel surface. A novel, mechanically stable, negatively charged matrix was synthesized for use in this solid phase enzyme assay and compared to phosphocellulose and carboxymethylcellulose paper. This new method allows the easy and exact determination of the molecular weight of any fusion protein with NPT II by assaying the position of the enzymatic activity in the gel and a consecutive immunological reaction following protein transfer onto nitrocellulose membranes.

Human B cell lines can be triggered to secrete an interleukin 2-like molecule

To determine whether human B cells can be triggered to secrete interleukin 2 (IL-2), 19 tumor cell lines derived from patients with undifferentiated lymphomas of Burkitt's and non-Burkitt's types and 6 normal lymphoblastoid cell lines were tested. Cells were grown in the presence or absence of the new tumor promoter teleocidin, and culture supernatants were assayed for IL-2 activity using the standard CTLL-2 assay. Teleocidin (10 ng/ml) triggered IL-2 secretion in 7/8 (87%) EBV-negative lymphoma cell lines of American origin and in 6/6 (100%) normal lymphoblastoid cell lines, but in only 1/6 (16%) EBV-positive tumor cell lines of American origin. Teleocidin had no effect on 5/5 (0%) African Burkitt's cell lines. IL-2 secretion was not detected in control supernatants. IL-2 secretion correlated with the induction of IgM secretion and was linked to both EBV status and karyotype. The following similarities in the functional biological characteristics of T cell and B cell IL-2 suggest that B cell IL-2 is not a factor which mimics IL-2 activity in the CTLL-2 assay: (i) neutralization of IL-2 by anti-IL-2 monoclonal antibody (DMS-1); (ii) elution of IL-2 following its adsorption to CTLL-2 cells; (iii) determination of the MW of IL-2 by SDS-PAGE and Western blot analysis; and (iv) ability of B cell IL-2 to support T cell proliferation and blocking of this activity by anti-tac monoclonal antibody. cDNA probes for T cell IL-2, however, did not detect IL-2 mRNA in B cells. The cell lines were also found to constitutively express IL-2 receptors detected by anti-tac monoclonal antibody, and to secrete soluble IL-2 receptors measured by ELISA. Our results imply that under certain circumstances, B cells can be triggered to secrete IL-2 or an IL-2-like molecule and thus influence T cell activation and proliferation.

Accumulation of chlamydial lipopolysaccharide antigen in the plasma membranes of infected cells

The presence of a chlamydia-specified antigen associated with the plasma membrane of infected cell lines was demonstrated by indirect immunofluorescence staining with a monoclonal antibody, designated 47A2, specific for the chlamydial genus-specific lipopolysaccharide (LPS) antigen. Staining of HeLa, L-929, and McCoy cells infected with the L2 or F serovar of Chlamydia trachomatis was observed either without fixation or following aldehyde fixation and brief drying. The 47A2-reactive antigen appeared to be present on the plasma membrane, on bleb-like structures on the host cell surface, and on proximal processes of neighboring uninfected cells. Antibodies to chlamydial protein antigens such as the major outer membrane protein produced no surface staining under similar conditions. Membrane vesicles elaborated from infected cells were enriched for the 47A2-reactive antigen. Superinfection of chlamydia-infected cells with vesicular stomatitis virus, an enveloped virus which buds from the plasma membrane, allowed purification of progeny virions that were enriched with chlamydial LPS. These results are consistent with the presence of chlamydial LPS in the plasma membranes of infected host cells.

N-myc gene expression and oncoprotein characterisation in medulloblastoma

Although medulloblastoma and neuroblastoma share many common biological, histological and immunological features, the frequency of N-myc amplification differs markedly between the two tumours. In this study, Southern blot analysis revealed that the N-myc gene was not amplified in any of the nine medulloblastoma samples analysed. In contrast, over-expression of the gene was found in six of 11 samples as determined by immunocytochemistry and/or Western blot analysis, using an antiserum raised against a synthetic peptide representing a sequence unique to the N-myc gene product. The specificity of this reagent was demonstrated by studies on a variety of cell lines expressing N-myc and/or c-myc oncoproteins. Of the 12 medulloblastoma samples collected over a two-year period and analysed in the course of this project, a trend towards longer disease-free survival was noted in the patients having low levels of the N-myc protein in their tumour.

Interactions of synapsin I with small synaptic vesicles: distinct sites in synapsin I bind to vesicle phospholipids and vesicle proteins

Synapsin I is a major neuron-specific phosphoprotein that is specifically localized to the cytoplasmic surface of small synaptic vesicles. In the present study, the binding of synapsin I to small synaptic vesicles was characterized in detail. The binding of synapsin I was preserved when synaptic vesicles were solubilized and reconstituted in phosphatidylcholine. After separation of the protein and lipid components of synaptic vesicles under nondenaturing conditions, synapsin I bound to both components. The use of hydrophobic labeling procedures allowed the assessment of interactions between phospholipids and synapsin I in intact synaptic vesicles. Hydrophobic photolabeling followed by cysteine-specific cleavage of synapsin I demonstrated that the head domain of synapsin I penetrates into the hydrophobic core of the bilayer. The purified NH2-terminal fragment, derived from the head domain by cysteine-specific cleavage, bound to synaptic vesicles with high affinity confirming the results obtained from hydrophobic photolabeling. Synapsin I binding to synaptic vesicles could be inhibited by the entire molecule or by the combined presence of the NH2-terminal and tail fragments, but not by an excess of either NH2-terminal or tail fragment alone. The purified tail fragment bound with relatively high affinity to synaptic vesicles, though it did not significantly interact with phospholipids. Binding of the tail fragment was competed by holosynapsin I; was greatly decreased by phosphorylation; and was abolished by high ionic strength conditions or protease treatment of synaptic vesicles. The data suggest the existence of two sites of interaction between synapsin I and small synaptic vesicles: binding of the head domain to vesicle phospholipids and of the tail domain to a protein component of the vesicle membrane. The latter interaction is apparently responsible for the salt and phosphorylation dependency of synapsin I binding to small synaptic vesicles.

Electrostatic and hydrophobic interactions of synapsin I and synapsin I fragments with phospholipid bilayers

Synapsin I, a major neuron-specific phosphoprotein, is localized on the cytoplasmic surface of small synaptic vesicles to which it binds with high affinity. It contains a collagenase-resistant head domain and a collagenase-sensitive elongated tail domain. In the present study, the interaction between synapsin I and phospholipid vesicles has been characterized, and the protein domains involved in these interactions have been identified. When lipid vesicles were prepared from cholesterol and phospholipids using a lipid composition similar to that found in native synaptic vesicle membranes (40% phosphatidylcholine, 32% phosphatidylethanolamine, 12% phosphatidylserine, 5% phosphatidylinositol, 10% cholesterol, wt/wt), synapsin I bound with a dissociation constant of 14 nM and a maximal binding capacity of about 160 fmol of synapsin I/microgram of phospholipid. Increasing the ionic strength decreased the affinity without greatly affecting the maximal amount of synapsin I bound. When vesicles containing cholesterol and either phosphatidylcholine or phosphatidylcholine/phosphatidylethanolamine were tested, no significant binding was detected under any conditions examined. On the other hand, phosphatidylcholine vesicles containing either phosphatidylserine or phosphatidylinositol strongly interacted with synapsin I. The amount of synapsin I maximally bound was directly proportional to the percentage of acidic phospholipids present in the lipid bilayer, whereas the Kd value was not affected by varying the phospholipid composition. A study of synapsin I fragments obtained by cysteine-specific cleavage showed that the collagenase-resistant head domain actively bound to phospholipid vesicles; in contrast, the collagenase-sensitive tail domain, though strongly basic, did not significantly interact. Photolabeling of synapsin I was performed with the phosphatidylcholine analogue 1-palmitoyl-2-[11-[4-[3-(trifluoromethyl)diazirinyl]phenyl] [2-3H]undecanoyl]-sn-glycero-3-phosphocholine; this compound generates a highly reactive carbene that selectively interacts with membrane-embedded domains of membrane proteins. Synapsin I was significantly labeled upon photolysis when incubated with lipid vesicles containing acidic phospholipids and trace amounts of the photoactivatable phospholipid. Proteolytic cleavage of photolabeled synapsin I localized the label to the head domain of the molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Optimizing the solid-phase immunofiltration assay. A rapid alternative to immunoassays

The technical variables of the solid-phase immunofiltration assay (SPIA) for the detection of antibodies bound to antigens on a solid-phase filter have been investigated. The binding to solid-phase filters of 125I-labelled axial filament proteins derived from Treponema phagedenis and the optimal conditions for blocking non-specific protein binding were analysed. Axial filament was applied to nitrocellulose, Hybond Nylon and Zeta Probe. After extensive rinsing, the highest amount (68%) of axial filament was observed bound to Zeta Probe. However, blocking non-specific protein binding by pre-wetting the filter with rinsing buffer containing 0.5% Tween 20, prevented the binding of protein to the filter only when nitrocellulose was used as solid phase. Tween 20 (0.5%) in the rinsing and incubation solutions was found to be necessary for the reduction of non-specific binding of contaminants in turbid sera. However, the use of such solutions resulted in a substantial leakage of antigen (47%) during rinsing procedures. Binding of antigen-specific antibody was analysed using 125I-labelled protein A. The maximal possible binding of the antibody occurred within 5 min when the antibody solution was filtered. For optimal binding of 125I-labelled protein A an incubation time of 1 h was needed. It is suggested that solid-phase immunofiltration may provide a rapid alternative for radioimmunoassays or enzyme immunoassays for the detection of specific antibodies.

Enhanced immunodetection of blotted house dust mite protein allergens on nitrocellulose following blocking with Tween 20

The effect of blocking nitrocellulose membranes with the nonionic detergent Tween 20 on the detection, by protein blotting, of IgE-binding to house dust mite Dermatophagoides pteronyssinus allergens has been investigated. Tween blocking led to enhanced immunodetection of allergens despite removal of proteins from the membrane when compared to protein blocking agents which did not displace transferred components. The enhancement varied with the different mite components and, for one in particular, antigen Der p II, an increase of more than 100-fold in IgE antibody binding occurred despite a concurrent loss of more than 90% of Der p II from the membrane. Both the enhancement of binding and loss of components from the membrane were dependent upon the time course of blocking and the concentration of Tween used.

A polyclonal antiserum against the rabbit progesterone receptor recognizes the human receptor: biochemical characterization

Polyclonal antiserum was generated in guinea pigs immunized with the 116,000 Mr rabbit uterine progesterone receptor (PR). The PR antigen was partially purified by DEAE-cellulose chromatography and preparative sodium dodecyl sulphate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and the 116,000 Mr band excised and injected into guinea pigs. The antiserum recognized on protein blots rabbit uterine PR of Mr 116,000 and 81,000. The antiserum was judged to be specific for PR from normal and malignant human tissues as determined by sedimentation shift on sucrose gradients, immunoprecipitation studies, protein blotting, and fluorographic analysis using photolabelled samples. Comparison of protein blots probed with this polyclonal antiserum or with a recently obtained monoclonal antibody to human PR indicated that similar PR structures were recognized in rabbit and human samples by both antisera. Characterization of the polyclonal antiserum has demonstrated its suitability for investigating the immunolocalization or PR in normal and malignant human tissues as well as the receptor structure detected on protein blots.

Preparation and characterization of monoclonal antibodies against native membrane-bound penicillin-binding protein 1B of Escherichia coli

We prepared monoclonal antibodies against penicillin-binding protein 1B (PBP 1B) of Escherichia coli to study the membrane topology, spatial organization, and enzyme activities of this protein. The majority of the antibodies derived with PBP 1B as the immunogen reacted against the carboxy terminus. To obtain monoclonal antibodies recognizing other epitopes, we used PBP 1B lacking the immunodominant carboxy-terminal 65 amino acids as the immunogen. Eighteen monoclonal antibodies directed against membrane-bound PBP 1B were isolated and characterized. The epitopes recognized by those monoclonal antibodies were located with various truncated forms of PBP 1B. We could distinguish four different epitope areas located on different parts of the molecule. Interestingly, we could not isolate monoclonal antibodies against the amino terminus, although they were specifically selected for. This is attributed to its predicted extreme hydrophilicity and flexibility, which could make the amino terminus very sensitive to proteolytic degradation. All antibodies reacted against native PBP 1B in a dot-blot immunobinding assay. One monoclonal antibody also recognized PBP 1B in a completely sodium dodecyl sulfate-denatured form. This suggests that all the other monoclonal antibodies recognize conformational epitopes. These properties make the monoclonal antibodies suitable tools for further studies.

Production and characterization of murine monoclonal antibodies to Histoplasma capsulatum yeast cell antigens

Four monoclonal antibodies (MAbs) were produced by immunizing mice with a disrupted yeast cell homogenate of Histoplasma capsulatum. MAbs 1 and 2 reacted only with the yeast cell antigens of H. capsulatum and Blastomyces dermatitidis, whereas MAbs 3 and 4 showed broader cross-reactivity. MAb 3 cross-reacted with B. dermatitidis, Paracoccidioides brasiliensis, Sporothrix schenckii, and Candida albicans, and MAb 4 cross-reacted with B. dermatitidis, C. albicans, Coccidioides immitis, Aspergillus fumigatus, and Mycobacterium tuberculosis. All four MAbs exhibited unique specificity when reacted with three different strains of H. capsulatum (G217B, A811, and P-IN). MAb 1 belonged to the IgG2b subclass, MAb 3 belonged to the IgG1 subclass, and MAbs 2 and 4 belonged to the IgG3 subclass. MAbs 1, 2, and 3 formed bands in the Western immunoblot assay; the two dominant distinct bands had apparent molecular masses of 72 and 62 kilodaltons.

Partial characterisation of the human erythrocyte antigen Pta

Ghosts were prepared from erythrocytes positive for the rare blood group antigen Pta. Immunoblotting of the solubilised ghosts with anti-Pta located the antigen on a band with an Mr of 31,600, about 1,100 higher than that of sialoglycoprotein gamma. Binding to the same band was also observed when cytoskeleton preparations from Pt(a+) erythrocytes were immunoblotted with the antibody. Haemagglutination and immunoblotting experiments were consistent in demonstrating that the Pta antigen is not inactivated by treatment of intact erythrocytes with neuraminidase or trypsin but is destroyed by treatment with alpha-chymotrypsin, papain or pronase. The data indicate that the Pta antigen is carried on a 'new' erythrocyte membrane protein.