Epitope-specific Monoclonal Antibodies Research Articles

Differentiation of pathogenic Entamoeba histolytica infections from nonpathogenic infections by detection of galactose-inhibitable adherence protein antigen in sera and feces.

We determined whether epitope-specific monoclonal antibodies to the galactose-inhibitable adherence protein (GIAP) of Entamoeba histolytica could be used in an enzyme-linked immunosorbent assay (ELISA) to detect antigen in serum and feces and differentiate between nonpathogenic zymodemes and the potentially invasive pathogenic organisms that require treatment. Overall, 57% of subjects from Cairo, Egypt, with symptomatic intestinal amebiasis and 42% with asymptomatic infection possessed GIAP antigen in their sera, whereas 4% of uninfected controls or subjects with other parasitic infections possessed GIAP antigen in their sera (P < 0.001). In subjects from Durban, South Africa, only 6% of uninfected controls or those with nonpathogenic E. histolytica infection were positive for GIAP in serum, whereas 3 of 4 with asymptomatic pathogenic intestinal infection and 75% with amebic liver abscess were positive for GIAP in serum. Fifteen stool samples from patients with intestinal amebiasis were available for study; all had a positive ELISA result for fecal GIAP antigen. Epitope-specific monoclonal antibodies identified 8 of 15 subjects with fecal antigen from pathogenic strains. Seven of those eight subjects had adherence protein antigen in their sera, whereas none of seven with apparent nonpathogenic E. histolytica infection had adherence protein antigen in their sera. In summary, we were able to detect E. histolytica adherence protein antigen directly in serum and fecal samples by ELISA. The presence of amebic antigen in serum demonstrated 94% specificity for pathogenic E. histolytica infection, and amebic antigen is present during asymptomatic intestinal infection. In conjunction with antibody detection, this method should be very useful in the diagnosis and management of intestinal amebiasis.

Antibodies to Epitopes of Herpes Simplex Virus Type 1 Glycoprotein B (gB) in Human Sera: Analysis of Functional gB Epitopes Defined by Inhibition of Murine Monoclonal Antibodies

The epitopes on herpes simplex virus (HSV) glycoprotein B (gB) recognized by sera of 23 patients with well-characterized HSV infection were studied. Twelve epitope-specific monoclonal antibodies with neutralization (NT) or antibody-dependent cellular cytotoxicity (ADCC) activities were used in competitive ELISA binding inhibition studies. The sera were additionally analyzed for homologous viral type NT, ADCC activity, and gB-reactive antibody by ELISA. Seroconversion was observed in each assay during convalescence. Relative type specificity for sera from HSV-1-infected but not from HSV-2-infected individuals was demonstrated in the ADCC assay. Sera from HSV-infected patients contained antibodies recognizing 9 of 12 epitopes, representing 5 of the 6 characterized antigenic domains of gB tested. Two of the epitopes were blocked in a type-specific fashion. The incidence of epitopic recognition increased gradually with time and was delayed compared with the detection of functional ADCC or NT activity and overall antibody recognition of gB in the ELISA.

Initial characterization of the major mouse cytochrome p450 enzymes involved in the reductive metabolism of the hypoxic cytotoxin 3-Amino-1,2,4-Benzotriazine-1,4- di- N-Oxide (Tirapazamine, SR 4233, Win 59075)

The benzotriazine di- N-oxide SR4233 (tirapazamine, WIN 59075) is currently in phase I clinical trials as the lead compound in a series of novel and highly selective antitumour hypoxic cytotoxins. Reductive bioactivation is thought to proceed via a one-electron reduced, oxidizing nitroxide radical and also forms the inactive single N-oxide SR4317 via radical disproportionation or a second oneelectron reduction. In mouse liver microsomes reductive metabolism is catalysed predominantly by cytochrome P450 (70%) and cytochrome P450 reductase (30%). The aim of the present study was to examine which cytochrome P450 isozymes may be involved. Reduction of SR4233 to SR4317 was monitored by HPLC analysis. Metabolism by microsomes from both control and dexamethasone-induced BALB/c male mice was 70% inhibited by carbon monoxide. The cytochrome P450 inhibitor SKF 525A, following aerobic preincubation, also inhibited SR4233 reduction by 58%. Reduction was induced 2–3-fold by dexamethasone and was not accountable by increases in cytochrome P450 reductase or DT-diaphorase. The induction data and the greater degree of inhibition of SR 4233 reduction by metyrapone compared to α-naphthoflavone suggested a possible involvement of Cyp2b, Cyp2c and Cyp3a cytochrome P450 subfamilies. Both Cyp3a (7.4-fold) and Cyp2b (1.8-fold) type enzymes were shown by western immunoblot analysis to be induced by dexamethasone, the latter correlating more closely with increased SR 4233 reductase activity and also with the 2-fold induction of benzphetamine TV-demethylase, a Cyp2b-type enzyme. No inhibition of SR4233 reduction was seen with erythromycin or cyclosporin A which act as substrates/inhibitors for Cyp3a-type enzymes, but inhibition was seen with p-nitrophenol and tolbutamide which are substrates for Cyp2el- and Cyp2c-type enzymes, respectively (11% and 25% inhibition in induced microsomes). SR4233 itself inhibited benzphetamine N-demethylase, which is catalysed by Cyp2b-type enzymes but not erythromycin N-demethylase which is catalysed by Cyp3a-type isoforms. Immunoinhibition studies with epitope specific monoclonal antibodies were consistent with the major involvement of phenobarbitone- and steroid-inducible products of the Cyp2b and Cyp2c subfamilies. These forms contributed at least 53% and 26%, respectively, of the cytochrome P450-associated SR4233 reductase activity in the induced microsomes. The findings support our earlier conclusion that cytochrome P450 is the major SR 4233 reductase in mouse liver and provides leads as to the possible involvement of specific isoforms in human tumours and normal tissues.

Immunogenicity in mice of tandem repeats of an epitope from herpes simplex gD protein when expressed by recombinant adenovirus vectors

The antigenic and immunogenic potential was examined of human adenovirus type 5 (Ad) recombinants carrying and expressing from one to four tandem repeats of a linear neutralizing epitope from the gD protein of herpes simplex virus type 1 (HSV-1) as a fusion with the β-galactosidase protein. The fusion proteins produced by these Ad vectors in infected cell culture reacted with a herpes simplex virus (HSV) epitope-specific monoclonal antibody to a degree dependent on the number of epitope repeats in the protein. Mice immunized by intraperitoneal injection of the Ad vectors developed an anti-HSV immune response as measured by ELISA and by HSV-1 neutralization assays. The mean antibody titre induced by a single injection of the Ad vector increased with the number of epitope repeats expressed by the recombinant. Any animal that had developed a serum-neutralizing titre of at least 1:80 survived challenge with a normally lethal dose of HSV-2 administered by the intraperitoneal route. Recombinant vectors expressing four repeats of the HSV epitope were as effective in antibody induction and protection as an adenovirus vector carrying and expressing the entire HSV gD protein. These results suggest that the expression of tandem repeats of appropriate epitopic sequences by adenovirus vectors may provide a safe and effective method of immunizing against HSV infection.

Epitope specificity of monoclonal antibodies against Newcastle disease virus: competitive fluorogenic enzyme immunoassay.

A test to determine the epitope specificity of monoclonal antibodies (MCA) was developed for hybridoma clones producing antibodies against Newcastle disease virus (NDV). The virus was first immobilized on nitrocellulose membranes of Millititer HA plates. Dilutions of MCA were then added, singly, or simultaneously in pairs, and bound antibody was quantitated with alkaline phosphatase-labelled detector antibody and a fluorogenic substrate, 4-methylumbelliferyl phosphate (4-MUP). Fluorescence count was measured fluorometrically. Additivity indices were calculated and plotted against dilutions of paired MCA. Antibodies that recognized identical epitopes displayed non-additivity at saturating antibody dilutions, followed by partial additivity and by total additivity at low, non-saturating dilutions. In contrast, MCA that recognized distinct epitopes exhibited total additivity throughout the curve. MCA that exhibited partial additivity were interpreted as competing for overlapping shared epitopes, or, distinct epitopes in close proximity, resulting in steric hinderance.

Degradation of rat liver cytochromes P450 3A after their inactivation by 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine: Characterization of the proteolytic system

The suicide substrate 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4-dihydropyridine (DDEP) inactivates rat liver cytochrome P450 (P450) 3A isozymes through prosthetic heme alkylation of the apoprotein in a mechanism-based fashion, which marks them for rapid proteolysis. In this article, through the use of epitope-specific monoclonal antibodies, we show that both 3A1 and 3A2 isozymes are targeted for proteolysis. Furthermore, using intact rats, isolated rat hepatocytes, and rat liver subcellular fractions supplemented with ATP and MgCl 2, as well as various proteolytic inhibitors as probes, we now report that the hepatic cytosolic ubiquitin-dependent proteolytic system rather than hepatic lysosomes is involved in the rapid degradation of DDEP-induced heme alkylated P450s 3A.

Mapping epitope specificities of monoclonal antibodies to thyroid peroxidase using recombinant antigen preparations.

Five separate monoclonal antibodies (MoAbs) to human thyroid peroxidase (hTPO) were raised by immunising Balb/c mice with hTPO purified from detergent solubilised thyroid microsomes by high performance liquid chromatography (HPLC). The epitope specificities of these MoAbs were determined by assessing their ability to bind to purified recombinant fusion protein fragments of human TPO (TPO(r)) generated in E. coli. A total of seven small overlapping fragments (averaging 104 amino acid residues) of hTPO, encompassing over 90% of the extracellular region of the molecule, were generated as glutathione S-transferase (GST) fusion proteins. The sequential epitopes on TPO(r) recognised by these MoAbs were analysed by both immunoblotting and enzyme linked immunosorbent assay (ELISA). Two different MoAbs (A4 and A5) recognised sequential epitopes within the TPO(r) preparation termed R1a + b (residues 1-160) and more specifically, in the case of MoAb A4, within the subfragment R1b (residues 70-160). The inability of the other MoAbs (A1-A3) to recognise recombinant fragments, suggests they either recognise conformational determinants on the TPO molecule or epitopes that are present on the small regions of the TPO molecule which have not been expressed as recombinant proteins.

Isolation by fluorescence-activated cell sorting of cells of a human lymphoblastoid cell strain containing mutations in the lambda immunoglobulin gene.

Fluorescence-activated cell sorting (FACS) was used to establish clonal populations of a human lymphoblastoid cell strain that contain spontaneously occurring and N-methyl-N'-nitro-N-nitrosoguanidine-induced mutations in the lambda immunoglobulin gene. Multiple rounds of FACS using a monoclonal antibody specific for the membrane-expressed human lambda immunoglobulin were used to enrich the population fraction of cells lacking a wild-type lambda immunoglobulin on the cell surface. Approximately 20% of the clonal populations established after five rounds of FACS-mediated enrichment did not express the lambda immunoglublin epitope recognized by the monoclonal antibody used for selection. However, evaluation of the FACS-selected mutant clonal populations with a polyclonal antilambda antibody, or a monoclonal antibody directed against a different epitope on the lambda immunoglobulin made by the T5-1 cells, indicated that the mutant clonal populations expressed lambda immunoglobulin on their cell surfaces. Additionally, the presence of lambda mRNA and of both secreted and cytoplasmic lambda protein confirmed the transcription and translation of the lambda immunoglobulin gene. These data suggest that FACS-mediated selection employing epitope-specific monoclonal antibodies provides a powerful technique for isolation of cell populations that express mutations within the coding region of the lambda immunoglobulin gene.

Direct measurement of calpastatin subtypes by sandwich enzyme immunoassay using monoclonal antibodies

Six stable hybridoma cell lines secreting monoclonal antibodies to human calpastatin were established. All monoclonal antibodies belong to the IgG1 subclass and recognized different epitopes on calpastatin. At least two groups were distinguished; the first group was specific for muscle-type (M-) calpastatin and the second group recognized not only M-calpastatin but also erythrocyte-type (E-) calpastatin. The inhibitory effect of all monoclonal antibodies on calpastatin activity was relatively low even at high concentrations of antibodies. Enzyme immunoassay systems were developed for direct determination of calpastatin subtypes in human cells requiring no other sample treatment than the disruption of the cells. The assay methods were, in principle, based on the sandwich enzyme immunoassay using epitope-specific monoclonal antibodies. The enzyme immunoassay system for M-calpastatin was specific for M-calpastatin and could not detect E-calpastatin. The enzyme immunoassay system for total calpastatin detected not only M-calpastatin but also E-calpastatin. The sensitivity of these assay systems was 10 pmol l-1 of calpastatins. Antigenicity of calpastatins was found to be unchanged in the presence of EDTA and haemoglobin. Good reproducibilities of within-and between-assay series and excellent recovery of exogenous calpastatins from cell lysates were observed. From these results, it seems that our newly developed subtype-specific enzyme immunoassay systems for calpastatins are useful in biochemical studies and clinical testing for determination of calpastatin subtypes.

Trichinella spiralis: Influence of an immunodominant, carbohydrate-associated determinant on the host antibody response repertoire

Host antibody responses to the G2.1 epitope, a carbohydrate-associated determinant shared by several Trichinella spiralis glycoproteins, were examined by competitive inhibition enzyme-linked immunosorbant assay (ELISA). The G2.1 epitope dominated the AKR/J mouse antibody response whether the antigens were injected or introduced through infection, as determined by the serum blocking ability of a G2.1 epitope-specific monoclonal antibody (mAb). Serum T. spiralis-binding activity from several other infected mouse strains was blocked 22 to 86% by the G2.1 epitope-specific mAb. In addition to mice, the G2.1 epitope evoked powerful antibody responses in four other species. The binding activity of Trichinella-reactive antibodies from infected rats and pigs was inhibited 56 and 34%, respectively, by the mAb. Greater than 48% of the T. spiralis serum-binding activity from 4 5 infected humans was G2.1-specific. Most of the rabbit antibody response induced by injection of a previously characterized 43-kDa antigen was also directed to the G2.1 determinant. The specificities of 10 T. spiralis-reactive mAb were examined, and 7 reacted with the immunodominant epitope. Finally, of nine helminth species examined, only T. spiralis and T. pseudospiralis extracts efficiently blocked G2.1-specific antibody binding to solid-phase antigens. These results suggest that the responses to G2.1 epitope may play an important role during infection.

Synthesis of a tetrasaccharide of the genus-specific lipopolysaccharide epitope of Chlamydia

Allyl 2-acetamido-2-deoxy-3,4- O-(1,1,3,3,-tetraisopropyldisiloxan-1,3-diyl)-β- d-glucopyranoside was coupled with methyl (4,5,7,8-tetra- O-acetyl-3-deoxy-α- d- manno-2-octulopyranosyl bromide)onate ( 1) to give a good yield of the α-(2→6)-linked disaccharide, isolated after deacetylation and regioselective conversion into the corresponding 7′,8′- O-carbonyl or 7′,8′- O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl) derivatives, respectively. Subsequent glycosylation with 1 gave a high yield of the α- and β-(2″→4′)-linked trisaccharide derivatives 16 and 18, whereas block synthesis using the α-(2→8)-linked Kdo-disaccharide bromide derivative 19 afforded a low yield of the corresponding α- and β-(2″→4′)-linked tetrasaccharide derivatives 20 and 22. Removal of the protecting groups furnished the disaccharide allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2→6)-2-acetamido-2-deoxy-β- d-glucopyranoside, the trisaccharide allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2→4)-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)- (2→6)-2-acetamido-2-deoxy-β- d-glucopyranoside, and the tetrasaccharide allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2→8)-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)- (2→4)-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2→6)-2-acetamido-2-deoxy-β- d-glucopyranoside in high yield. Copolymerization of the allyl glycosides with acrylamide gave artificial polyvalent haptens suitable for defining epitope specificities of monoclonal antibodies directed against Chlamydia lipopolysaccharides.

Determination of the epitope specificities of monoclonal antibodies using unprocessed supernatants of hybridoma cultures

A double monoclonal antibody (mAb) ELISA has been developed to determine the epitope specificites of murine monoclonal (mAbs). It permits the mAbs which bind to the same or adjacent epitopes to be distinguished from those which bind to separate epitopes on soluble monomeric proteins. The assay is designed for the early evaluation of mAbs in hybridoma culture supernatants when purified or labeled mAbs are not available. It does not rely on chemical or enzymatic fragmentation of the antigen and does not generate results which may ne due to differences in the affinities of the mAbs. Moreover the characteristic multiple binding of polychonal antibodies to the same epitope is also avoided. A further advantage is the accessibility of epitopes on a given antigen since the antigen is presented by a solid-phase mAb, in contrast to assays in which the antigen itself is adsorbed onto the solid phase. The test was evaluated using the culture supernatants from hybridomas which produced mAbs against the complement proteins C3a, C6 or C7.

Spontaneous mutations leading to antigenic variations in the glycoproteins of vesicular stomatitis virus field isolates

Strains of vesicular stomatitis virus, New Jersey serotype (VSV-NJ), isolated from diseased cattle or swine were examined by genomic RNA sequencing for genetic diversity potentially leading to antigenic variations in their type-specific glycoproteins as determined by reactivity with epitope-specific monoclonal antibodies (MAbs). Seven field isolates recovered in Colorado, New Mexico, Georgia, and Mexico during the widespread 1982–1985 epizootic in the western United States resembled the prototypic 1952 Hazelhurst subtype by partial sequence homology, but amino acid reversions to the 1949 Ogden subtype occurred frequently. When studies were performed with MAbs directed to the Ogden subtype glycoprotein, relatively limited antigenic variation, and only in neutralization epitope VIII, was noted among two of five epizootic isolates from Colorado and New Mexico. However, amino acid differences in the glycoprotein of a 1983 isolate from an enzootic region of Georgia resulted in major antigenic deficiencies in epitopes V, VI, and VII as determined by Western blotting and neutralization of infectivity with epitope-specific MAbs. Quite a few genetic but no antigenic differences were noted in an enzootic 1984 isolate from Mexico, a potential origin of the United States epizootic. Marked or complete loss of epitopes VII, VI, VIII, and V can be traced to spontaneous mutations leading to amino acid substitutions at glycoprotein positions 199, 263, 275, and 317, respectively, in the enzootic Georgia isolate 07/83-GA-P and the epizootic New Mexico isolate 06/85-NM-B. By comparison, closely adjacent amino acid substitutions at glycoprotein positions 210, 268, 277, and 364 occurred in epitope-deficient mutants selected for resistance to neutralization by MAbs specific for epitopes VII, VI, VIII, and V, respectively. Two neutralization epitopes designated X and XI were found to be unique for the G protein of the 1952 Hazelhurst isolate … /52-GA-P. The epitope X-specific MAb H21, in particular, failed to neutralize the infectivity not only of the Ogden subtype …/49-UT-B but also was ineffective against all the 1982–1985 field isolates. The classical 1952 Hazelhurst strain of VSV-NJ is genetically and antigenically quite different from those viruses isolated during the 1982–1985 epizootic.

Determination of the epitope specificity of monoclonal antibodies against the inner core region of bacterial lipopolysaccharides by use of 3-deoxy- d- manno-octulosonate-containing synthetic antigens

Partial structures of enterobacterial lipopolysaccharides (LPS) of the Rechemotype, consisting of lipid A and 3-deoxy- d- manno-2-octulosonic acid (Kdo), as well as oligosaccharides and derivatives of Kdo were synthesized and used to characterize the epitope specificity of monoclonal antibodies against Re-mutant LPS. High-molecular-weight antigens, obtained after copolymerization of the respective allyl glycosides with acrylamide, and the haptenic oligosaccharides were used in immunoprecipitation, immune hemolysis, and in inhibition assays. A monoclonal antibody (clone 20, IgM) recognizing a terminal Kdo p group was shown to require for its binding the α-anomeric configuration and OH-4 and OH-5 groups, whereas the C-7C-8 chain was of minor importance. Another monoclonal antibody (clone 25, IgG 3), which recognizes a (2→4)-linked Kdo disaccharide, was shown to require for its binding the α-anomeric configuration of both residues. The isomer having a reducing β-Kdo residue was significantly less active, and that with a terminal β-Kdo group was completely inactive. The OH-5 group of the reducing residue was shown to be not important for the specificity of this antibody, since it could be replaced by a hydrogen atom without loss of serological reactivity. The α-(2→8)-linked Kdo disaccharide was strongly cross-reactive with its (2→4)-linked isomer. The antibody recognized also parts of the 2-amino-2-deoxy- d-glucose backbone of lipid A.

Transcription-inhibition and RNA-binding domains of influenza A virus matrix protein mapped with anti-idiotypic antibodies and synthetic peptides

We have undertaken by biochemical and immunological experiments to locate the region of the matrix (M1) protein responsible for down-regulating endogenous transcription of A/WSN/33 influenza virus. A more refined map of the antigenic determinants of the M1 protein was obtained by binding of epitope-specific monoclonal antibodies (MAbs) to chemically cleaved fragments. Epitope 2-specific MAb 289/4 and MAb 7E5 reverse transcription inhibition by M1 protein and react with a 4-kilodalton cyanogen bromide fragment extending from amino acid Gly-129 to Gln-164. Anti-idiotype serum immunoglobulin G prepared in rabbits immunized with MAb 289/4 or MAb 7E5 mimicked the action of M1 protein by inhibiting transcription in vitro of influenza virus ribonucleoprotein cores. This transcription-inhibition activity of anti-MAb 7E5 immunoglobulin G and anti-MAb 289/4 immunoglobulin G could be reversed by MAb 7E5 and MAb 289/4 or could be removed by MAb 7E5-Sepharose affinity chromatography. Transcription of influenza virus ribonucleoprotein was inhibited by one of three synthetic oligopeptides, a nonodecapeptide SP3 with an amino acid sequence corresponding to Pro-90 through Thr-108 of the M1 protein. Of all the structural proteins of influenza virus, only NP and M1 showed strong affinity for binding viral RNA or other extraneous RNAs. The 4-kilodalton cyanogen bromide peptide (Gly-129 to Gln-164), exhibited marked affinity for viral RNA, the binding of which was blocked by epitope 2-specific MAb 7E5 but not by MAbs directed to three other epitopes. Viral RNA also bound strongly to the nonodecapeptide SP3 and rather less well to anti-idiotype anti-MAb 7E5; these latter viral RNA-binding reactions were only slightly blocked by preincubation of anti-MAb 7E5 or SP3 with MAb 7E5. These experiments suggest the presence of at least two RNA-binding sites, which also serve as transcription-inhibition sites, centered around amino acid sequences 80 through 109 (epitope 4?) and 129 through 164 (epitope 2) of the 252 amino acid M1 protein of A/WSN/33 influenza virus. A hydropathy plot of the M1 protein calculated by free-energy transfer suggests that the two hydrophilic transcription-inhibition RNA-binding domains are brought into close proximity by an alpha-helix-forming intervening hydrophobic domain.

Epitope mapping by deletion mutants and chimeras of two vesicular stomatitis virus glycoprotein genes expressed by a vaccinia virus vector

Deletion mutants and chimeras of the glycoprotein (G) genes of vesicular stomatitis virus serotypes Indiana (VSV-Ind) and New Jersey (VSV-NJ) were cloned in plasmids and vaccinia virus vectors under control of the bacteriophage T7 polymerase promoter for expression in CV-1 cells co-infected with a T7 polymerase-expressing vaccinia virus recombinant. Truncated and chimeric G proteins expressed by these vectors were tested for their capacity to react with VSV-Ind and VSV-NJ epitope-specific monoclonal antibodies (MAbs) by Western blot analysis for those antigenic determinants not affected by disulfide-bond reducing conditions or by immuno dotblot analysis for those that are. These experiments allowed us to create putative epitope maps for glycoproteins of both serotypes based on binding affinity and cross-reactivity of VSV-Ind and VSV-NJ MAbs for truncated or chimeric G proteins of known amino acid sequences. Seven of the 9 VSV-NJ G epitopes, including all 4 epitopes involved in virus neutralization by MAbs, mapped to the center (amino acid sequence 193–289) of the 517 amino acid VSV-NJ G protein. Four of the 11 VSV-Ind G epitopes, including 2 neutralizable epitopes, mapped to the cysteine-rich amino-terminal domain (amino acid sequence 80–183) of the 511 amino acid VSV-Ind G protein; the remaining 7 VSV-Ind G epitopes, including 2 involved in virus neutralization, were clustered in the cysteine-poor carboxy-terminal domain (amino acid sequence 286–428). In site-specific mutants of the VSV-Ind G gene defective in one or both glycosylation sites, only the amino-terminal epitopes of the VSV-Ind G protein were affected bydeletion of the carbohydrate chain at residue 179; deletion of the carbohydrate chain at residue 336 did not alter reactivity of the G protein with any of the relevant monoclonal antibodies. These results are discussed in relation to earlier attempts to map the antigenic determinants of VSV-N1 and VSV-Ind G proteins by proteolysis of the G protein and by sequencing the G genes of mutant viruses selected for their resistance to neutralization by epitopespecific monoclonal antibodies.

Synthesis of a trisaccharide of 3-deoxy- d- manno-2-octulopyranosylonic acid (KDO) residues related to the genus-specific lipopolysaccharide epitope of chlamydia

The disaccharides, O-(sodium 3-deoxy-α- and -β- d- manno-2-octulopyranosylonate)-(2→8)-sodium (allyl 3-deoxy-α- d- manno-2-octulopyranosid)onate, were prepared via glycosylation of methyl (allyl 4,5,7-tri- O-acetyl-3-deoxy-α- d- manno-2- octulopyranosid)onate with methyl (4,5,7,8-tetra- O-acetyl-3-deoxy- d- manno-2- octulopyranosyl bromide)onate under Helferich and Koenigs-Knorr conditions, respectively. Based on g.l.c.-m.s. data of the α- and β-(2→8)-linked disaccharide derivatives, obtained after carbonyl- and carboxyl-group reduction, followed by methylation, the α-anomeric configuration was assigned to the terminal KDO-residue in the KDO-region of Chlamydial lipopolysaccharide. The trisaccharide O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2→8)-(sodium 3-deoxy- α- d- manno-2-octulopyranosylonate)-(2→4)-sodium (allyl 3-deoxy-α- d- manno-2- octulopyranosid)onate was obtained via block synthesis using an α-(2→8)-linked disaccharide bromide derivative as the glycosyl donor. Copolymerization of the allyl glycosides with acrylamide gave water-soluble macromolecular antigens, suitable for defining epitope specificities of monoclonal antibodies directed against Chlamydial LPS.

Analysis of epitope specificity of monoclonal antibodies by counterflow isotachophoresis on nitrocellulose membranes

When working with monoclonal antibodies (MCAB) to an individual antigen (AG) it is necessary to determine that epitope specificity, i.e., their targeting toward the same or different determinants. Competitive analysis of MCAB is usually used for this purpose, by solidphase radioimmunoassay [4], for which purified AG and radioactive labeling of each of the MCAB to be compared are required. In the investigation described below it is shown that epitope specificity of MCAB can be analyzed by counterflow isotachophoresis (ITP) on a nitrocellulose membrane (NCM) [I] on a model of MCAB to human (HAFP) and mouse (MAFP) a-fetoprotein (AFP). The method does not require purified AG or MCAB, or their radioactive labeling, it canbe performed automatically, and requires only the simplest electrophoretic equipment. Rat MCAB to MAFP and mouse MCAB to HAFP were used. Rat MCAB were obtained as described previously [6]. Culture media (CM) of three hybridomas (D6, G~, Ha), both initial and concentrated tenfold by precipitation with (NH~)2SO~ (0.33 of saturation), were used for analysis. MCAB to HAFP were obtained by fusing the splenocytes of a mouse immunized with a purified HAFP preparation and myeloma X63-AgS.653 cells. MCAB of three cell lines (D1o, De, Es) in mouse ascites fluid were used. Rabbit antiserum of MAFP (anti-MAFP) was obtained as described previously [2] and neonatal mouse serum (NMS) was used as the MAFP preparation. A commercial immunodiagnostic serum for primary carcinoma of the liver (N. F. Gamaleya Institute of Epidemiology and Microbiology, Academy of Medical Sciences of the USSR), including rabbit anti-HAFP and AG, containing 50 ~g HAFP in i ml and with a large excess of serum albumin, was used as the system for determining HAFP. Mouse MCAB to rat L~ IgG (rat anti-L K containing 3 mg of antibodies in i ml [5] and rat IgG (i0 mg/ml), generously provided by A. Yu. Rudenskii (AllUnion Research Institute of Genetics, Main Administration of the Microbiological Industry of the USSR), were used. Fab'-fragments of donkey antiserum to rabbit IgG, conjugated with horseradish peroxidase (P) (Fab'-P), were obtained by V. S. Poltorandina by the method in [8]. To abolish cross reactions between reagents used in the analysis, embryonic calf serum (ECS) was added to the anti-MAFP, and rat IgG and ECS were added to the Fab'-P in concentrations chosen beforehand.

Mouse hepatic cytochrome p-450 isozyme induction by 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene, pyrazole, and phenobarbital

The effects of 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) and pyrazole on mouse hepatic cytochrome P-450 isozyme expression were compared to the P-450 induction pattern elicited by phenobarbital. TCPOBOP and PB administration caused a similar induction profile by increasing microsomal protein and cytochrome P-450 content and the catalytic activities of several monooxygenases in DBA/2N and AKR/J mice. There were, however, several quantitative and some qualitative differences in the induction profile caused by phenobarbital and TCPOBOP. A few strain-related differences were also observed. Immunoblot analysis with polyclonal anti-coumarin hydroxylase (P-450 Coh) antibody and epitope-specific monoclonal antibodies 1-7-1 and 2-66-3 showed that both phenobarbital and TCPOBOP increase the amount of P450IIB and P-450 Coh. TCPOBOP caused a more pronounced increase in the amount of P-450IIB than phenobarbital, and TCPOBOP also caused an increase in the amount of P-450IA2. These data suggest that in the mouse, TCPOBOP increases mainly the expression of P-450 isozymes responsive to phenobarbital. The effects of pyrazole differed greatly from those caused by TCPOBOP and phenobarbital. In the DBA/2N mice, pyrazole increased coumarin 7-hydroxylation 9.4-fold, whereas in the AKR/J mice the activity was induced only to a level equivalent to the DBA/2N basal level. In immunoblot experiments with anti-P-4500 Coh antibody, the amount of P-450 Coh was considerably higher in DBA 2N mice treated with phenobarbital, TCPOBOP, or pyrazole in comparison with the AKR/J mice, indicating a strain specificity in the inducibility of coumarin 7-hydroxylase by pyrazole.

Site-specific mutations in vectors that express antigenic and temperature-sensitive phenotypes of the M gene of vesicular stomatitis virus

Full-length cDNA copies of mRNAs coding for the matrix (M) proteins of vesicular stomatitis virus and its mutant tsO23(III) were cloned in pBSM13- (BlueScribe). The authenticity of these clones was demonstrated by restriction enzyme mapping, DNA sequencing, and in vitro transcription and translation to identify the two M proteins by Western immunoblotting with epitope-specific monoclonal antibodies. Site-directed mutants were constructed by primer extension of synthetic oligodeoxynucleotides with one or two nucleotide changes to alter the glycine at amino acid 21 of the wild-type (wt) M gene to glutamic acid, alanine, or proline. Similarly, a revertant was created in the M gene of mutant tsO23 by a Glu-21----Gly substitution. A series of wt- and mutant-M-gene chimeras was also constructed to create mutant and revertant clones with Leu----Phe and His----Tyr alterations at amino acids 111 and 227, respectively. We then moved the wt and tsO23 M genes and their site-specific mutants and chimeras cloned in pBSM13- into the eucaryotic expression vector pTF7 directed by the T7 bacteriophage RNA polymerase of the vaccinia virus recombinant vTF1-6,2. Western blot analysis of the M proteins transiently expressed in CV-1 cells by plasmids carrying M genes altered at amino acid 21 revealed that the critical antigenic determinant (epitope 1) is expressed only by the Gly-21 M protein and not by Glu-21, Ala-21, or Pro-21 M proteins. Of particular interest is an apparent conformational change, evidenced by slightly but significantly retarded electrophoretic migration, in plasmid-expressed M proteins with amino acids substituted for glycine at position 21. The glutamic acid at position 21 of tsO23 is not responsible for its temperature-sensitive phenotype, because a tsO23 revertant plasmid with glycine substituted at position 21 fails to rescue tsO23 virus in cells infected at the restrictive temperature; conversely, plasmids expressing wt M protein with substitutions of glutamic acid, alanine, or proline at position 21 are just as effective in marker rescue of tsO23 as is the Gly-21 wt M protein. Marker rescue experiments with wt- and mutant-M-gene chimeras support the hypothesis of K. Morita, R. Vanderoef, and J. Lenard (J. Virol. 61:256-263, 1987) that the temperature-sensitive phenotype of tsO23 is due to a phenylalanine substituted for leucine at amino acid 111, rather than the His-227----Tyr substitution or the Gly-21----Glu substitution, which independently accounts for the loss of epitope 1 in the mutant M protein of tsO23.(ABSTRACT TRUNCATED AT 400 WORDS)