Construction of recombinant neisserial Hsp60 proteins and mapping of antigenic domains

Here we report the cloning and expression, in Escherichia coli, of PCR-amplified DNA encoding the 63-kDa stress-inducible protein of Neisseria gonorrhoeae strains VP1 and PiD2, Neisseria meningitidis 2996 and the commensal Neisseria flavescens. DNA sequence analysis revealed in all cases one open reading frame of 541-544 amino acids corresponding to a protein of approximately 57 000 Da. The various neisserial proteins were >98% identical at the amino acid level and showed extensive homology with proteins belonging to the HspSO heat-shock-protein family. We constructed defined glutathione S-transferase fusion polypeptides of the gonococcal Hsp60 homologue to locate antigenic domains on the recombinant protein. Variation in the immunoreactivity of two monoclonal antibodies recognizing a conserved and a neisseria-unique antigenic Hsp60 determinant, respectively, could thus be deduced to result from single amino acid substitutions. Analysis of the antibody response in patients’sera demonstrated reactivity with the same fusion polypeptides in six out of nine sera, indicating that neisserial Hsp60 is expressed during the natural infection and that distinct domains on the protein are immunodominant in vivo.     

Identification and molecular analysis of a 63-kilodalton stress protein from Neisseria gonorrhoeae.

Iron limitation, glucose deprivation, and growth under low oxygen supply (environmental stress) increased the expression of several proteins of Neisseria gonorrhoeae, including a 63-kilodalton protein identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This gonococcal stress protein (GSP63) was detected in the cytosol and copurified with lithium acetate-derived outer membranes. Successful purification of the protein was achieved by sucrose density gradient centrifugation and by chromatography on phenyl-Sepharose. Gel filtration of the purified protein revealed a molecular weight of approximately 450,000, suggesting that in its native state, the protein consists of a multimer of six to eight subunits. Isoelectric focusing indicated a pI of 5.2. Immunoblotting experiments using a polyclonal antiserum raised against the purified protein demonstrated cross-reactivity with a protein of the same electrophoretic mobility as GSP63 in all eight gonococcal isolates tested. N-terminal amino acid sequencing of the protein revealed up to 65% homology with members of the Hsp60 heat shock protein family, suggesting that GSP63 is related to this group of proteins. This relationship was further substantiated by the immunological cross-reactivity of GSP63 with mycobacterial Hsp60 and the ATP-binding activity of the gonococcal stress protein.     

Immunologic and structural characterization of the dominant 66- to 73-kDa antigens of Borrelia burgdorferi

The 66- to 73-kDa proteins of Borrelia burgdorferi are dominant immunogens and expressed in all strains of B. burgdorferi. The humoral response to these Ag occurs relatively early during the course of infection. Two-dimensional Western blot analysis of this group of Ag revealed them to consist of a tetrad of proteins with apparent molecular mass of 66, 68, 71, and 73 kDa. Furthermore, in this study we demonstrate the 66-kDa protein to be a potent inducer of lymphoproliferation in the patient immune to B. burgdorferi. Monospecific polyclonal antibodies and mAb demonstrate that each of these proteins was immunologically distinct. However, direct amino acid sequence of the 66- and 68-kDa Ag was almost identical and had a high level of sequence similarity to the GroEL heat-shock protein (Hsp60) of Escherichia coli and the 60-kDa immunodominant protein of Treponema pallidum. The amino terminal sequence of the 71- and 73-kDa proteins of B. burgdorferi was almost identical and these proteins had remarkable sequence similarity to the DnaK heat-shock protein of E. coli (Hsp70). It appears likely, therefore, that proteins related to the heat-shock family are potent immunogens of B. burgdorferi.     

Expression and immunologic characterization of recombinant heat shock protein 58 of Leptospira species: a major target antigen of the humoral immune response

A clone of Leptospira interrogans serovar lai that was isolated by immunoscreening of a genomic lambda library with sera from convalescent patients with leptospirosis directed expression of a unique 62-kDa protein in Escherichia coli. When examined by SDS-PAGE, the protein comigrated with an immunodominant protein present in leptospiral cell lysate. Determination of the nucleotide sequence of the 2.7-kb insert DNA identified two genes homologous to the hsp58 and hsp10 of L. interrogans serovar copenhageni reported previously. The overexpressed recombinant Hsp58 protein was purified and used to immunize a rabbit to produce a polyclonal antibody. Immunoblot analysis using the rabbit anti-Hsp58 G antibodies showed that the 62-kDa protein was commonly present in lysates of other serovars of leptospires, consistent with the strong sequence conservation between the hsp58 genes of the two serovars. Immunoglobulin G antibodies to the Hsp58 were specifically detected by ELISA in 82% of sera (18/22) from patients with leptospirosis. Deletion analysis of the recombinant Hsp58 protein indicated that a strong antigenic determinant for humoral immune response is located between amino acids 360 and 380 (DREKLQERLAKLAGGVAVIHV) of Hsp58, which are highly conserved among the GroEL family. The strong sequence conservation of the Hsp58 among leptospires and its importance as a major target for the humoral immune response warrant further studies of its potential pathogenetic role.     

Partial primary structure of the 48- and 90-kilodalton core proteins of cell surface-associated heparan sulfate proteoglycans of lung fibroblasts. Prediction of an integral membrane domain and evidence for multiple distinct core proteins at the cell surface of human lung fibroblasts

Heparitinase treatment of cell surface-associated heparan sulfate proteoglycans (HSPG) of human lung fibroblasts reveals core proteins with apparent Mr values of 125,000, 90,000, 64,000, 48,000 and 35,000 (Lories, V., De Boeck, H., David, G., Cassiman, J.-J., and Van den Berghe, H. (1987) J. Biol. Chem. 262, 854-859). The 90- and 48-kDa core proteins share the epitope of the monoclonal antibody 6G12 which was used to screen a human lung fibroblast expression cDNA library. Rescreening of the libraries yielded clone 48K5 with an insert of 3439 base pairs. Polyclonal antibodies were raised in rabbits against a fragment of the protein encoded by the 48K5 cDNA different from the part carrying the 6G12 epitope. These antibodies specifically recognize the 90- and 48-kDa core proteins on Western blots of total cellular extracts of human lung fibroblast HSPG. The specific reactivity of the polyclonal antiserum confirms the identity of the 48K5 clone and further distinguishes the 48- and the 90-kDa core proteins, which do share the 6G12-defined epitope and at least one additional antigenic determinant with the 48K5 cDNA-encoded protein, from the 125-, 64-, and 35-kDa core proteins of cell surface HSPG of human lung fibroblasts which do not react with either antibody preparation. The protein encoded by the 48K5 clone contains a stop-transfer sequence indicative of an integral membrane protein and three potential glycosaminoglycan attachment sites. The 48K5 clone detects two major poly(A)+ RNA species in human lung fibroblasts presumably generated by the use of alternative polyadenylation signals. The 48K5 gene was mapped to chromosome 8q23 by in situ hybridization and hybridization to DNA of somatic cell hybrids.     

Monoclonal antibodies to gonococcal outer membrane protein I: location of a conserved epitope on protein IB

Hybrid cell lines have been derived which produce monoclonal antibodies reacting with outer membrane protein I from Neisseria gonorrhoeae strain P9. The antibodies obtained showed variable reactivity with other strains but one antibody recognized an epitope present on all of the strains tested which expressed the protease sensitive protein IB. Purified IgG labelled with 125I was used in competitive radioimmunoassays with unlabelled antibody to investigate the spacial distribution of the epitopes recognized. Each pair of antibodies showed some degree of inhibition. The relative magnitude of inhibition suggested that the conserved epitope lies within a variable region containing other epitopes which determine the antigenic specificity of the protein. Western blotting of peptides derived by proteolytic digestion of protein IB revealed that the conserved epitope is located close to the chymotrypsin cleavage site within a 7000 Mr surface exposed region of the molecule.     

Heat-shock response in Legionella pneumophila

The heat-shock response of Legionella pneumophila was examined by radiolabelling bacterial cell proteins with [35S]methionine following a temperature shift from 30 to 42 degrees C. Five heat-shock proteins were identified as having molecular masses of 17, 60, 70, 78, and 85 kilodaltons (kDa). The 85- and 60-kDa proteins were equally distributed between supernatant and pellet fractions following ultracentrifugation at 100,000 x g, the 70- and 78-kDa proteins were found primarily in the supernatant, and the 17-kDa protein was found primarily in the pellet. Synthesis of subsets of the heat-shock proteins could be stimulated by novobiocin, patulin, or puromycin. Ethanol, an effector of the heat-shock response in other microorganisms, had little effect on L. pneumophila, even at the highest concentration tolerated by the bacterial cells (1.9%). Finally, the 60-kDa heat-shock protein of L. pneumophila was immunologically cross-reactive with a polyclonal antibody prepared to the Escherichia coli groEL protein. However, a mouse monoclonal antibody reactive with the 60-kDa protein of all legionellae tested did not cross-react with the E. coli groEL protein, suggesting that the Legionella 60-kDa protein contains common and unique epitopes.     

Monoclonal antibodies recognizing different epitopes of the 27-kDa gap junction protein from rat liver

Monoclonal antibodies (2-3E2, 6-3G11, and 7-3H6) against gap junction plaques purified from rat liver were prepared and characterized. Immunoblot analysis of liver gap junctions revealed that all three antibodies reacted with the 27-kDa protein, but not with the 22-kDa one. The 2-3E2 and 6-3G11 antibodies both reacted with the 27-kDa protein in gap junctions purified from livers of the rat, mouse, rabbit, and guinea pig; the 7-3H6 antibody, however, failed to react with the 27-kDa protein from guinea pig liver. The 7-3H6 antibody reacted strongly with the 24- to 26-kDa degradation products of the 27-kDa protein. Indirect immunofluorescence showed that the 6-3G11 and 7-3H6 antibodies both gave the same specific fluorescence labeling on rat liver cryosections, suggesting that these two antibodies recognized the cytoplasmic sites of the 27-kDa protein. Immunoblot analysis of protease-digested fragments from the 27-kDa protein revealed that the 7-3H6 antibody reacted with the 24- and 17-kDa fragments (including portions of the carboxyl-terminal domain of the 27-kDa protein) produced with endoproteinases Arg-C and Lys-C, respectively. Immunoblot analysis of CNBr fragments of the 27-kDa protein revealed that all three antibodies reacted with the 10-kDa fragment, which is thought to be the carboxyl-terminal domain of the 27-kDa protein. These results demonstrate that three monoclonal antibodies recognize different epitopes of the cytoplasmic sites (probably the carboxyl-terminal domain) of the 27-kDa liver gap junction protein.     

Analysis of common antigen of flagella in Bacillus cereus and Bacillus thuringiensis

Abstract Flagellar antigen of Bacillus cereus H.1 was purified and tested for serodiagnostic antigen by ELISA. The antibody against the flagellar antigen of B. cereus H.1 reacted not only with the homologous specific antigen but also reacted with the flagellar antigens of 23 strains of B. cereus . This common flagellar antigen of B. cereus was found to be due to 61-kDa protein by SDS-PAGE and immunoblot assay. Monoclonal antibody H15A5 against common antigenic epitope of B. cereus also reacted with flagellar antigens of 21 strains of Bacillus thuringiensis by ELISA. This monoclonal antibody reacted with the 61-kDa protein of the flagella of B. cereus H.1 and H.2 and B. thuringiensis Kurstaki HD1, Alesti and Aizawai juroi by immunoblot analysis. These results indicated that the common antigenic epitope of the 61-kDa protein existed in the flagella both of B. cereus and B. thuringiensis .     

Autoantibodies against chaperonin CCT in human sera with rheumatic autoimmune diseases: comparison with antibodies against other Hsp60 family proteins

Chaperonin CCT containing t-complex polypeptide 1 is a cytosolic molecular chaperone that assists in the folding of actin, tubulin, and other proteins and is a member of the 60-kDa heat shock protein (Hsp60) family. We examined antibody titers against human CCT and other Hsp60 family members in the sera of patients with rheumatic autoimmune diseases, including rheumatoid arthritis, systemic lupus erythematodes, Sj?gren syndrome, and mixed connective tissue disease. Autoantibody titers against not only human mitochondrial Hsp60 but also CCT were significantly higher in the sera of patients with rheumatic autoimmune diseases than in healthy control sera. Although immunoglobulin G (IgG) titers against Escherichia coli GroEL were high in all the groups of sera tested, no significant differences in anti-GroEL responses were detected between patients and healthy controls. IgG titers against mycobacterial Hsp65 showed a similar pattern to titers of autoantibodies recognizing GroEL. Immunoabsorption experiments demonstrated that most of the autoantibodies recognizing CCT were cross-reactive with mitochondrial Hsp60, E coli GroEL, and mycobacterial Hsp65. Although most of the anti-Hsp60 IgG recognized CCT, anti-GroEL (or antimycobacterial Hsp65) IgG contained antibodies specific for GroEL (or mycobacterial Hsp65) in addition to antibodies cross-reactive with CCT and Hsp60. Results from immunoblot analyses, together with weak (15% to 20%) amino acid sequence identities between CCT and the other Hsp60 family members, suggested that CCT-reactive autoantibodies recognize conformational epitopes that are conserved among CCT and other Hsp60 family members.     

Monoclonal antibody characterization of the 195-kilodalton major surface glycoprotein of Plasmodium falciparum malaria schizonts and merozoites: identification of additional processed products and a serotype-restricted repetitive epitope

The gp195 from Camp strain parasites was characterized with eight monoclonal antibodies (MAb) that recognize different epitopes on gp195 and three of its merozoite-associated processed products. Four MAb (3H7, 3B10, 7F1, and 4G12) reacted with different epitopes on the 45-kDa glycosylated product (gp45), shown by differences in their reactivities with soluble and immunoblotted gp45. One MAb (7H10) reacted with a conformational epitope probably formed as a result of the interaction of gp45 with a nonglycosylated 45-kDa product (p45). Three other MAb (3D3, 7B11, and 7B2) reacted with different epitopes on a nonglycosylated 83-kDa product (p83), shown by differences in their reactivities against various parasite isolates in immunofluorescent antibody assays. Immunoprecipitation of antigens that were pulse-labeled with [3H]isoleucine and chased with cold isoleucine showed that p45 and gp45 were processed products of gp195 and p83 was sequentially processed into smaller fragments of 73 and 67 kDa (p73 and p67). Immunoblots showed that the 7B11 and 7B2 epitopes were present on p83, p73, and p67, but that the 3D3 epitope was present only on p83 and p73. A two-site immunoassay showed the 3D3 epitope to be repetitive. The 3D3 and 7B11 epitopes were serotype restricted (present in seven and 24 of 33 isolates, respectively), but the other five epitopes were common to all isolates tested. The gp195 and its processed products have Mr that are consistent with the Mr of a number of antigens shown previously to be associated with the immune complexes that are formed when merozoites are agglutinated by antibodies contained in some growth inhibitory immune sera.     

Comparison of the 34,000-Da pp60src substrate and a 38,000-Da phosphoprotein identified by monoclonal antibodies

One of the cellular targets of the pp60src tyrosine kinase is a phosphoprotein with a Mr = 34,000 and an isoelectric point of approximately 7.5 (Radke, K., Gilmore, T., and Martin, G. S. (1980) Cell 21, 821-828; Erikson, E., and Erikson, R. L. (1980) Cell 21, 829-836). We report here the preparation of monoclonal antibodies to partially purified 34-kDa protein and to a heretofore unrecognized phosphoprotein that is not a pp60src target. Two antibodies were initially obtained that recognized phosphoproteins in the Mr = 34,000-39,000 range. One of these antibodies immunoprecipitated a 34,000-Da protein which, on the basis of its molecular mass, phosphorylation state, and isoelectric point, was determined to be the 34-kDa pp60src substrate. The second monoclonal antibody bound to a 38,000-Da nucleolar associated protein, which appeared not to be a target of the pp60src kinase and was found by tryptic analysis to be structurally unrelated to the 34-kDa protein. The monoclonal antibody to the 34-kDa protein coupled to Sepharose CL-4B was used to purify the pp60src substrate to homogeneity in milligram quantities. Both the purified 34-kDa protein and the monoclonal antibody are currently being used in studies aimed at elucidating the structure and function of this pp60src target.     

Antigenic determinants of the HLA-B7 molecule; Bw6- and B7-specific determinants are spatially separate

Monoclonal antibodies that bind HLA-B7 were used to show that the B7-specific determinant is at a topologically different site from that of the broad polymorphic, Bw6 determinant. The relationship to other antigenic determinants defined by monoclonal antibodies was also assessed. These results were independently obtained in four ways: (1) by cellular blocking assays, in which there was no inhibition of 125I-B7 antibody binding in the presence of Bw6 antibody and no inhibition of 125I-Bw6 antibody binding in the presence of B7 antibody; (2) cellular binding assays under conditions of antibody saturation showed the binding of B7-specific and Bw6 antibodies were additive; (3) solid-phase radioimmune assays demonstrated enhancement between B7-specific and Bw6 antibodies; (4) analysis of antigen antibody complexes by size-exclusion high pressure liquid chromatography showed Bw6 and B7 antibodies could form tetramolecular complexes with papain-solubilized HLA-B7. Limitations were encountered in using cellular blocking assays to map antigenic determinants of HLA-B7. These assays can produce blocking in cases where two antibodies are not competing for an antigenic determinant. Mapping antigenic determinants with assays using purified HLA-B7 as the antigenic target, in addition to cell-based assays, provided a more accurate picture.     

Respiratory syncytial virus fusion glycoprotein: further characterization of a major epitope involved in virus neutralization

Competition experiments and biological assays with a panel of 15 monoclonal antibodies confirmed the presence of at least four antigenic sites on the fusion protein of human respiratory syncytial virus, three of which were involved in virus neutralization. One antigenic site, recognized by two strongly neutralizing antibodies, was conserved after reduction and denaturation and shown by immunoblotting to be localized on the F1 fragment of the fusion protein. Cleavage of this protein with staphylococcal protease V8 or papain produced a series of smaller peptides from 11 to 7 kilodaltons that retained this important neutralization determinant. Compared with the other neutralization sites, the epitope defined by monoclonal antibody 7C2 thus appears as the major neutralization epitope. Our peptide mapping results support the hypothesis that this major epitope is composed of a continuous sequence on the viral genome.     

Topographic analysis of antigenic determinants recognized by monoclonal antibodies to the photoreceptor guanyl nucleotide-binding protein, transducin

Antigenic sites for six monoclonal antibodies that bind to the alpha subunit (G alpha) of the photoreceptor guanyl nucleotide-binding protein (G-protein or transducin) have been determined. Five of these antibodies (4A, 7A, 7B, 7C, and 7D) were shown in the preceding paper (Hamm, H. E., Deretic, D., Hofmann, K. P., Schleicher, A., and Kohl, B. (1987) J. Biol. Chem. 262, 10831-10838) to block G-protein-rhodopsin interaction. We have blotted tryptic and chymotryptic peptides of G-protein to nitrocellulose paper and found that these antibodies bind to peptides that contain the COOH-terminal end of the protein assessed by 32P-ADP-ribosylation of the COOH-terminus by pertussis toxin. The antigenic site is not exactly at the COOH-terminus since the antibodies also bind two peptides which lack a 2-kDa piece from the COOH-terminus. Antigenic sites are therefore on the 7-kDa chymotryptic peptide and 5-kDa tryptic peptide more than 2 kDa away from the COOH-terminus. Further evidence for this antigenic site comes from the ability of these antibodies to block pertussis toxin-mediated ADP-ribosylation while still binding to the previously ADP-ribosylated protein both on nitrocellulose blots and in immunoprecipitations. Antibody 4H, which was shown not to interrupt any of the functions studied, binds to the 11-kDa major tryptic fragment. To aid in the mapping of these sites onto the surface of G alpha, a model of the three-dimensional structure of G alpha has been generated using the G alpha primary sequence, predicted secondary structure, hydropathy plot, and the constraints of the GDP-binding site of the GTP-binding protein elongation factor Tu solved by Jurnak (Jurnak, F. (1985) Science 230, 32-36).     

Demonstration of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes by monoclonal antibodies

Calmodulin-dependent cyclic nucleotide phosphodiesterase from bovine brain is found to be composed of two distinct subunits, 60,000- and 63,000-dalton polypeptides. Peptide mapping of the subunits by partial proteolysis demonstrated that the 60-kDa polypeptide is not derived from the 63-kDa species. The interaction of the enzyme with three monoclonal antibodies, A6, C1, and A2, and the analysis of immunocomplexes by sucrose density gradient centrifugation revealed that calmodulin-dependent cyclic nucleotide phosphodiesterase exists in three different forms, i.e. (a) homodiamer of 60-kDa, (b) heterodimer of 60- and 63-kDa, and (c) homodimer of 63-kDa. A6 antibody reacts with both 60- and 63-kDa polypeptides indicating that they are immunologically related. C1 and A2 antibodies react with only 60-kDa polypeptide species. By using C1 Sepharose 4B affinity column chromatography, the 63-kDa homodimer which did not bind to the column (Fraction I) was separated from the 60-kDa polypeptide containing isozymes (the heterodimer and the 60-kDa homodimer) which were retained on the column and later eluted as a mixture (Fraction II). Fraction I, the 63-kDa homodimer enzyme, has higher Vmax toward cGMP as substrate than cAMP whereas the opposite was found with Fraction II. The specific activity of Fraction II enzyme toward cAMP was approximately 500 mumol/min/mg, the highest value ever reported for brain calmodulin-dependent cyclic nucleotide phosphodiesterase preparations.     

Heat-shock response of the upper intertidal barnacle Balanus glandula: thermal stress and acclimation

In the intertidal zone in the Pacific Northwest, body temperatures of sessile marine organisms can reach 35 degrees C for an extended time during low tide, resulting in potential physiological stress. We used immunochemical assays to examine the effects of thermal stress on endogenous Hsp70 levels in the intertidal barnacle Balanus glandula. After thermal stress, endogenous Hsp70 levels did not increase above control levels in B. glandula exposed to 20 and 28 degrees C. In a separate experiment, endogenous Hsp70 levels were higher than control levels when B. glandula was exposed to 34 degrees C for 8.5 h. Although an induced heat-shock response was observed, levels of conjugated ubiquitin failed to indicate irreversible protein damage at temperatures up to 34 degrees C. With metabolic labeling, we examined temperature acclimation and thermally induced heat-shock proteins in B. glandula. An induced heat-shock response of proteins in the 70-kDa region (Hsp70) occurred in B. glandula above 23 degrees C. This heat-shock response was similar in molting and non-molting barnacles. Acclimation of B. glandula to relatively higher temperatures resulted in higher levels of protein synthesis in the 70-kDa region and lack of an upward shift in the induction temperature for heat-shock proteins. Our results suggest that B. glandula may be well adapted to life in the high intertidal zone but may lack the plasticity to acclimate to higher temperatures.     

Detection of multiple antigenically related proteins from various rat tissues by monoclonal antibodies against 3 alpha-hydroxysteroid dehydrogenase.

Mouse hybridomas were prepared by fusing myelomas and spleen cells from mice immunized with purified rat 3 alpha-hydroxysteroid dehydrogenase. Hybridomas secreting monoclonal antibodies against 3 alpha-hydroxysteroid dehydrogenase were selected by indirect enzyme-linked immunoassay and then subcloned by limiting dilution. From two mice we have obtained four positive hybridomas, three secreting high affinity immunoglobulin (Ig) G1 and one secreting IgM. Only two of these monoclonal antibodies (MAbs 3G6 and 7D3, both IgG1) recognized denatured enzyme and, therefore, were used for further immunoblotting experiments. MAb 7D3 recognized a structurally related mouse enzyme, but not the human enzyme, whereas monoclonal antibody 3G6 recognized a human enzyme, but not the mouse enzyme. When these two monoclonal antibodies were used in immunoblotting to survey the expression of 3 alpha-hydroxysteroid dehydrogenase in rat liver and a number of other tissues, striking differences were found in the protein band patterns in kidney, lung, and testis. Both MAbs 7D3 and 3G6 recognized 3 alpha-hydroxysteroid dehydrogenase, a 34-kDa 7D3 recognized a protein of the same size as the liver protein, whereas MAb 3G6 recognized a 34-kDa protein plus another protein of 36 kDa. In kidney only MAb 3G6, but not MAb 7D3, recognized a 34-kDa protein. Conversely, the 34-kDa protein in testis was recognized by MAb 7D3, but not by MAb 3G6. These findings suggest the existence of multiple antigenically related proteins in different tissues.     

Shift in S-layer protein expression responsible for antigenic variation in Campylobacter fetus.

Campylobacter fetus strains possess regular paracrystalline surface layers (S-layers) composed of high-molecular-weight proteins and can change the size and crystalline structure of the predominant protein expressed. Polyclonal antisera demonstrate antigenic cross-reactivity among these proteins but suggest differences in epitopes. Monoclonal antibodies to the 97-kDa S-layer protein of Campylobacter fetus subsp. fetus strain 82-40LP showed three different reactivities. Monoclonal antibody 1D1 recognized 97-kDa S-layer proteins from all C. fetus strains studied; reactivity of monoclonal antibody 6E4 was similar except for epitopes in S-layer proteins from reptile strains and strains with type B lipopolysaccharide. Monoclonal antibody 2E11 only recognized epitopes on S-layer proteins from strains with type A lipopolysaccharide regardless of size. In vitro shift from a 97-kDa S-layer protein to a 127-kDa S-layer protein resulted in different reactivity, indicating that size change was accompanied by antigenic variation. To examine in vivo variation, heifers were genetically challenged with Campylobacter fetus subsp. venerealis strains and the S-layer proteins from sequential isolates were characterized. Analysis with monoclonal antibodies showed that antigenic reactivities of the S-layer proteins were varied, indicating that these proteins represent a system for antigenic variation.     

Epitope scanning reveals gain and loss of strain specific antibody binding epitopes associated with the conversion of normal cellular prion to scrapie prion

We used anti-prion (PrP) monoclonal antibodies (Mabs) in different combinations to scan changes in the availability of antibody binding epitopes--using an epitope scanning assay--in brain homogenates from normal mice, and from mice infected with either ME7 or 139 A strains of infectious scrapie prion (PrPSc). In ME7-infected brains, the epitope detected by the Mab pair 8B4/8H4 is reduced, while the epitope detected by the Mab pair 8F9/11G5 is increased. Mab 8F9/11G5 detect a conformational epitope on PrPSc because the rise in Mab 8F9/11G5 binding is sensitive to a denaturing agent but resistant to proteinase K (PK). While the increase in Mab 8F9/11G5 binding correlates with the presence of PK-resistant PrP and clinical signs of infection, the reduction in Mab 8B4/8H4 binding is detected earlier. Fractionation of the ME7-infected brain homogenate in sucrose gradient revealed that the PrPSc species detected by the epitope scanning assay are heterogeneous in size, with a molecular mass of approximately > or = 2000-kDa. We also investigated whether these findings were applicable to two other strains of PrPSc, namely 87 V and 22 L. We found that the decrease in Mab 8B4/8H4 binding detected in ME7-infected brains was also detected in 87 V-infected brains but not in 22 L-infected brains. In contrast, the increase in Mab 8F9/11G5 binding detected in ME7- and 139 A-infected brains was also detected in 22 L-infected brains but not in 87 V-infected brains. Therefore, each prion strain has its unique conformation, and we can monitor the conversion of normal cellular prion (PrPC) to PrPSc based on the changes in the antibody binding patterns. The epitope can be decreased or increased, linear or conformational, detected late or early during infection, in a strain specific manner.