Mapping the surface regions of Pseudomonas aeruginosa PAK pilin: the importance of the C-terminal region for adherence to human buccal epithelial cells

The adherence of non-mucoid Pseudomonas aeruginosa strains is believed to be mediated by the pilus, which consists of a single protein subunit of 15,000 Daltons called pilin. Ten antipeptide antisera were raised to map the surface regions of pilin from P. aeruginosa strain K (PAK). Only one of the antipeptide antisera to the eight predicted surface regions failed to react with PAK pili in direct ELISA. Five out of eight synthetic peptides representing the eight predicted surface regions reacted with anti-PAK pilus antiserum, indicating their surface exposure. Combining the antipeptide and antipilus antisera results, all eight predicted surface regions were demonstrated to be surface-exposed. The PAK 128-144-OH peptide produced the best binding antiserum to PAK pili. Only antipeptide Fab fragments directed against the disulphide bridged C-terminal region of PAK pilin blocked the adherence of pili to human buccal epithelial cells, which suggests that this region contains the receptor-binding domain of the PAK pilus.     

Identification of human adenovirus early region 1 products by using antisera against synthetic peptides corresponding to the predicted carboxy termini.

Synthetic peptides were prepared which corresponded to the carboxy termini of the human adenovirus type 5 early region 1B (E1B) 58,000-molecular-weight (58K) protein (Tyr-Ser-Asp-Glu-Asp-Thr-Asp) and of the E1A gene products (Tyr-Gly-Lys-Arg-Pro-Arg-Pro). Antisera raised against these peptides precipitated polypeptides from adenovirus type 5-infected KB cells; serum raised against the 58K carboxy terminus was active against the E1B 58K phosphoprotein, whereas serum raised against the E1A peptide immunoprecipitated four major and at least two minor polypeptides. These latter proteins migrated with apparent molecular weights of 52K, 50K, 48.5K, 45K, 37.5K, and 35K, and all were phosphoproteins. By using tryptic phosphopeptide analysis, the four major species (52K, 50K, 48.5K, and 45K) were found to be related, as would be expected if all were products of the E1A region. The ability of the antipeptide sera to precipitate these viral proteins thus confirmed that the previously proposed sequence of E1 DNA and mRNA and the reading frame of the mRNA are correct. Immunofluorescent-antibody staining with the antipeptide sera indicated that the 58K E1B protein was localized both in the nucleus and in the cytoplasm, especially in the perinuclear region. The E1A-specific serum also stained both discrete patches in the nucleus and diffuse areas of the cytoplasm. These data suggest that both the 58K protein and the E1A proteins may function in or around the nucleus. These highly specific antipeptide sera should allow for a more complete identification and characterization of these important viral proteins.     

Immunohistochemical detection of human estrogen receptor with region D-specific antipeptide antibodies.

To study the possibility of using antipeptide antibodies for the immunohistochemical determination of human estrogen receptors (ER), three peptides corresponding to the putative major antigenic regions of the human ER (Met12-Leu26, or ERP1; Thr227-Gln267, or ERP2; Leu256-Gly275, or ERP3) were used to produce site-specific rabbit polyclonal antipeptide antisera. High titer antibodies were obtained against all the peptides used, as judged by time-resolved fluoroimmunoassay. The antibodies against region D (ERP3) specifically immunoprecipitated the ER proteins in vitro, as did the antiERP2 antibodies to a much smaller extent. With one of the region D-specific antibodies (antiERP3 Ab2) ER could also be immunohistochemically detected. When benign and malignant human breast and normal endometrial tissues were used, the immunohistochemical staining observed with these antipeptide antibodies correlated well with the staining obtained with an established method. Thus, the results reported here show that this part of region D in ER is a potential antigenic epitope for the production of site-specific antibodies against ER. Antipeptide antibodies produced against this region can be used to immunolocalize the ER in various normal and pathological human tissues.     

Immunochemical mapping of antigenic regions on the human thyrotropin beta-subunit by antipeptide antibodies

To study antigenic sites present in the beta-subunit of human thyrotropin (hTSH), we produced site-specific antibodies directed against synthetic peptides analogous to the 1-18, 44-59, and 85-112 regions of the thyrotropin beta-subunit. The hTSH beta(1-18) peptide-carrier conjugate elicited antisera capable of binding to both radiolabeled hTSH and its beta-subunit whereas antibodies elicited against the hTSH beta(44-59) peptide-carrier conjugate bound only to the peptide. Thus, the NH2-terminal region of hTSH beta appears to be accessible at the surface of the hormone whereas the hTSH beta(44-59) region may be poorly accessible. Two monoclonal antipeptide antibodies that bound to 125I-hTSH beta, designated as TS01 and TS02, were selected after immunization with the hTSH beta(85-112) peptide-carrier conjugate. The antigenic site recognized by TS01 was located on the eight COOH-terminal(105-112) amino acid residues. TS02 antibody bound to an antigenic region included within Cys95 and Cys105. Both antigenic sites appeared to be more accessible on the free hTSH beta than on the hormone. Immunoblots performed on various preparations containing TSH revealed that TS02 antibody detected the beta-subunit from both the human and bovine species but not the rat TSH beta. Under reducing conditions, a low molecular weight material was identified in hTSH beta, likely caused by intrachain nicking.     

The structure of phenobarbital-inducible rat liver cytochrome P-450 isoenzyme PB-4. Production and characterization of site-specific antibodies

Fifteen peptides corresponding in sequence to segments of the major phenobarbital-inducible forms of rat hepatic cytochrome P-450 (termed P-450 PB-4 and P-450 PB-5) were chemically synthesized, conjugated to carrier proteins, and used to prepare site-specific rabbit and/or mouse antipeptide antibodies. Four of the synthetic peptides were recognized by rabbit heterosera raised against purified P-450 PB-4. The titer of these heterosera measured against P-450 PB-4 was only partially reduced upon complete adsorption of antipeptide activity suggesting that these peptides represent minor antigenic determinants. Each of the antipeptide antibodies recognized purified P-450 PB-4 and the highly homologous P-450 PB-5 as demonstrated by a solid-phase enzyme-linked immunosorbent assay. Although each antipeptide immunoprecipitated both purified 125I-labeled P-450 PB-4 and also in vitro-synthesized apo-P-450 PB-4, the yields of immunoprecipitation were low relative to that obtained using anti-P-450 heterosera. Only one of the antipeptide antibodies gave a good signal in an immunoblot analysis of either microsomal or purified P-450s PB-4 and PB-5. Three antipeptide antibodies raised against hydrophilic segments located in the amino-terminal one-third of P-450 PB-4 markedly inhibited the P-450 PB-4-catalyzed O-deethylation of the model substrate 7-ethoxycoumarin. Four of the antipeptide antibodies were found to cross-react with P-450 beta NF-B, the major aromatic hydrocarbon-inducible rat hepatic P-450, suggesting that certain amino acid sequences or regions of secondary structure are conserved between the major phenobarbital-induced and polycyclic-induced rat liver P-450 isoenzymes. These studies demonstrate the utility of antipeptide antibodies for evaluation of antigenic sites exposed in native P-450 PB-4, for identification of specific amino acid sequences important for the interaction of P-450 PB-4 with its substrate and/or with cytochrome P-450 reductase in a reconstituted system and for elucidation of structural and immunochemical homologies between P-450 PB-4 and other P-450 isoenzymes present in rat liver endoplasmic reticulum.     

Antigenic properties of synthetic fragments of the heavy chain of influenza virus A hemagglutinin

The antigenic properties of the synthetic peptides corresponding to the regions 122-133, 136-147, 154-164 of the virus A/Aichi/2/68 hemagglutinin heavy chain have been studied. The 122-133 and 136-147 peptides comprise together almost whole antigenic determinant A, while the 154-164 peptide is a part of determinant B. Rabbits immunized by the peptides conjugated with carrier-protein BSA gave the high immune response to hapten-peptides. Each antiserum reacted only with homologous conjugate. All the antipeptide serums reacted with the virus A/Aichi/2/68 fixed on the base. Conjugate of the 136-147 peptide reacted with the rabbit antiserum against the virus A/Aichi/2/68 rendering the direct evidence to location of at least one hemagglutinin antigenic determinant in the region 136-147.     

Lipid-induced recognition of a conformational determinant (residues 65 to 83) in myelin basic protein

The precipitation by antibodies to intact myelin basic protein (BP) and to synthetic peptides containing a sequence based on the region 65 to 83 of bovine BP, S82, S81, S79, and S24, of intact BP in solution or bound to lipid vesicles was compared, using 125I-BP or 14C-DPPC-labeled lipid-BP vesicles. The antipeptide antibodies were shown earlier to recognize conformational determinants which are not expressed in the intact protein in solution. Several anti-BP antibodies precipitated more of the BP free in solution than when bound to lipid vesicles, suggesting that some of the determinants recognized by these antibodies were either sequestered in the bilayer or were altered in conformation. In contrast, one anti-peptide antisera, which had a high titer for the conformational determinant in two of these peptides, S82 and S81, precipitated the protein to a significant degree when it was bound to PG vesicles, even though it did not react with the intact protein in solution. These results indicated that PG was able to confer on the protein the unique peptide conformation recognized by this antibody. PS was less effective, and other lipids were ineffective at conferring this conformation on the protein, supporting earlier results which showed that the conformation of the protein is influenced by the lipid composition of its environment. None of the other anti-peptide antibodies studied bound to the protein either in solution or in lipid vesicles. These results indicate that the lipid environment can sequester or alter the conformation of some antigenic determinants, preventing recognition by some anti-BP antibodies, and can expose or generate other conformational determinants, allowing recognition by an anti-peptide antiserum.     

Antipeptide antibodies directed against cytoplasmic rhodopsin sequences recognize the beta-adrenergic receptor

Antibodies were made against synthetic peptides that correspond to cytoplasmic domains of rhodopsin, the photopigment protein of the retinal rod. These antipeptide antibodies recognized rhodopsin as detected by immunoblot analysis. Antibodies directed against the cytoplasmic loop between transmembrane domains 1 and 2, as well as those directed against the serine/threonine-rich region of the COOH terminus of bovine rhodopsin, also recognized purified beta-adrenergic receptor isolated from mouse S49 lymphoma cells. In addition, antibodies raised against membrane-associated rhodopsin recognized the beta-adrenergic receptor. Both the antipeptide and anti-rhodopsin antibodies were able to detect a 65-kDa protein band corresponding to the molecular weight of the beta-adrenergic receptor in membranes derived from human placenta, rat adipocytes, and S49 mouse lymphoma cells. Putative recognition sites for the rhodopsin antibodies on the beta-adrenergic receptor are identified, and the significance of the homology between the two proteins is discussed.     

Synthesis and antigenic activity of peptides of the nucleocapsid protein of the hepatitis delta virus]

Hepatitis delta virus (HDV), a recently discovered infectious agent, participates in severe, often lethal forms of acute and chronic hepatitis and liver cirrhosis. Based on theoretical analysis of secondary structure, hydrophilicity and acrophilicity data, several regions of HDV antigen, presumably containing B-epitopes, have been revealed and the corresponding peptides have been synthesized by the solid phase method. All the peptides obtained reacted with the respective antipeptide rabbit sera. The peptides and their conjugates with BSA or KLH were used for ELISA with individual and pooled anti-HD-positive sera from patients with chronic delta hepatitis. The high antigenicity of the peptide 65-80 shows that one of the antigenically active regions of HDAg is situated between these amino acid residues and that the peptide may be used for detection of anti-HD antibodies in patients blood sera.     

Localization of neutralizing regions of the envelope gene of feline leukemia virus by using anti-synthetic peptide antibodies.

We synthesized 27 synthetic peptides corresponding to approximately 80% of the sequences encoding gp70 and p15E of Gardner-Arnstein feline leukemia virus (FeLV) subtype B. The peptides were conjugated to keyhole limpet hemocyanin and injected into rabbits for preparation of antipeptide antisera. These sera were then tested for their ability to neutralize a broad range of FeLV isolates in vitro. Eight peptides elicited neutralizing responses against subtype B isolates. Five of these peptides corresponded to sequences of gp70 and three to p15E. The ability of these antipeptide antisera to neutralize FeLV subtypes A and C varied. In certain circumstances, failure to neutralize a particular isolate corresponded to sequence changes within the corresponding peptide region. However, four antibodies which preferentially neutralized the subtype B viruses were directed to epitopes in common with Sarma subtype C virus. These results suggest that distal changes in certain subtypes (possibly glycosylation differences) alter the availability of certain epitopes in one virus isolate relative to another. We prepared a "nest" of overlapping peptides corresponding to one of the neutralizing regions of gp70 and performed slot blot analyses with both antipeptide antibodies and a monoclonal antibody which recognized this epitope. We were able to define a five-amino-acid sequence required for reactivity. Comparisons were made between an anti-synthetic peptide antibody and a monoclonal antibody reactive to this epitope for the ability to bind both peptide and virus, as well as to neutralize virus in vitro. Both the anti-synthetic peptide and the monoclonal antibodies bound peptide and virus to high titers. However, the monoclonal antibody had a 4-fold-higher titer against virus and a 10-fold-higher neutralizing titer than did the anti-synthetic peptide antibody. Competition assays were performed with these two antibodies adjusted to equivalent antivirus titers against intact virions affixed to tissue culture plates. The monoclonal antibody had a greater ability to compete for virus binding, which suggested that differences in neutralizing titers may relate to the relative affinities of these antisera for the peptide conformation in the native structure.     

Immunochemical studies of human erythropoietin using site-specific anti-peptide antibodies. Identification of a functional domain

Anti-peptide antibodies that bind to the amino terminus of human erythropoietin (residues 1-26) do not inhibit the hormone's biological activity, indicating that this region of the protein does not play a role in receptor recognition (Sytkowski, A. J., and Fisher, J. W. (1985) J. Biol Chem. 260, 14727-14731). We have now identified six other regions of the primary sequence that are relatively hydrophilic and, therefore, have a higher probability of being accessible to such antibody probes. Antibodies raised against synthetic peptides homologous to five of these regions, corresponding to residues 40-59, 80-99, 99-118, 111-129, and 131-150 recognize erythropoietin, confirming the prediction based upon relative hydrophilicity. Antibodies to a carboxyl terminal peptide 147-166 failed to bind the hormone, presumably due to steric hindrance imposed by a disulfide bond between Cys161 and one of the other cysteinyl residues. The antibodies were affinity purified on the relevant immobilized peptide and their capacity to inhibit (neutralize) erythropoietin's activity was assessed. Only anti-peptide 99-118 and anti-peptide 111-129 antibodies inhibited erythropoietin. This effect was reversed by excess peptide, demonstrating that the neutralizing action of the antibody was due to its antigen-specific binding. The results strongly suggest that the portion of erythropoietin's amino acid sequence represented by these peptides plays a functional role in the hormone's action, most probably by forming part of the receptor-binding domain.     

HBsAg合成肽段的免疫源性和抗肽血清与天然HBsAg的结合测定

我们将三种乙型肝炎表面抗原的合成肽段在联结载体或不接载体的情况下,分别制备成4种免疫原对兔子进行了免疫。大部分兔子都产生了抗肽抗体。其中抗P_(122-48)(auw)与抗P_(122-148)(adw)都能与天然HBsAg反应,而抗P_(122-148)(adw)的抗HBs活力比文献报道的都高,通过结构分析表明:含有天然蛋白上免疫显性区域的免疫原是合成疫苗的理想选者。     

The potential protective effect of immunization with outer-membrane protein I from Neisseria gonorrhoeae

Immunization of rabbits with outer membranes (OM) of Neisseria gonorrhoeae produced antibodies directed against outer-membrane proteins PI and PIII. The antibodies directed against PIII reacted equally well on Western blots with all strains tested, but antibodies directed against PI reacted only with the homologous strain. When purified PIB was used for immunization the immune response was quite different: the sera obtained reacted with both homologous and heterologous PIB types and also reacted with strains expressing PIA. Western blotting of peptides produced by sequential cleavage of PIB revealed that the antigenic determinants recognized by anti-OM sera were predominantly located in the central surface-exposed region of PIB, as is the epitope recognized by the protective anti-PIB monoclonal antibody SM24. In contrast antibodies produced by immunization with purified PI reacted with antigenic determinants in the N-terminal portion of PIB. Nevertheless these determinants are accessible to immune attack on the native protein since the anti-PI sera were opsonic and were strongly bactericidal for both PIA- and PIB-expressing strains.     

Mapping of B-neutralizing and T-helper cell epitopes on the bovine leukemia virus external glycoprotein gp51.

A battery of 19 synthetic peptides was used to characterize efficient neutralizing and helper T-cell epitopes on the bovine leukemia virus (BLV) external envelope glycoprotein gp51. Four of the antipeptide antisera raised in rabbits inhibited the formation of BLV-induced syncytia; these antisera are directed against peptides 64-73, 98-117, and 177-192. Only antisera directed against the 177-192 region also neutralized vesicular stomatitis virus-BLV pseudotypes. This study clearly demonstrates that neutralizing properties can be observed with antibodies raised to regions undescribed so far and included in both the amino-terminal and central parts of the antigen. In addition, some helper T-cell determinants were defined from gp51-immunized mice and from BLV-infected cattle. Although none of the peptides tested behaved as a universal helper T-cell epitope, peptide 98-117 stimulated T-cell proliferation from BALB/c mice and from three infected cows, while peptide 169-188 strongly stimulated T-cell proliferation from one infected cow. Further experiments performed with three peptides overlapping the 169-188 region (177-192, 179-192, 181-192) demonstrated the particular relevance of residue(s) P-177 and/or D-178 in the helper T-cell epitope. These data should assist in the design of an efficient subunit vaccine against BLV infection that contains peptides possessing both B-neutralizing and helper T-cell determinants.     

Identification of an immunodominant neutralizing and protective epitope from measles virus fusion protein by using human sera from acute infection.

Polyclonal sera obtained from African children with acute measles were used to screen a panel of 15-mer overlapping peptides representing the sequence of measles virus (MV) fusion (F) protein. An immunodominant antigenic region from the F protein (p32; amino acids 388 to 402) was found to represent an amino acid sequence within the highly conserved cysteine-rich domain of the F protein of paramyxoviruses. Epitope mapping of this peptide indicated that the complete 15-amino-acid sequence was necessary for high-affinity interaction with anti-MV antibodies. Immunization of two strains of mice with the p32 peptide indicated that it was immunogenic and could induce antipeptide antibodies which cross-reacted with and neutralized MV infectivity in vitro. Moreover, passive transfer of antipeptide antibodies conferred significant protection against fatal rodent-adapted MV-induced encephalitis in susceptible mice. These results indicate that this epitope represents a candidate for inclusion in a future peptide vaccine for measles.     

Identification of immunodominant epitopes derived from the respiratory syncytial virus fusion protein that are recognized by human CD4 T cells

Memory CD4 T-cell responses against respiratory syncytial virus (RSV) were evaluated in peripheral blood mononuclear cells of healthy blood donors with gamma interferon enzyme-linked immunospot (Elispot) assays. RSV-specific responses were detected in every donor at levels varying between 0.05 and 0.3% of CD4 T cells. For all donors tested, a considerable component of the CD4 T-cell response was directed against the fusion (F) protein of RSV. We characterized a set of 31 immunodominant antigenic peptides targeted by CD4 T cells in the context of the most prevalent HLA class II molecules within the Caucasian population. Most antigenic peptides were HLA-DR restricted, whereas two dominant DQ peptides were also identified. The antigenic peptides identified were located across the entire sequence of the F protein. Several peptides were presented by more than one major histocompatibility complex class II molecule. Furthermore, most donors recognized several F peptides. Detailed knowledge about immunodominant antigenic peptides will facilitate the ability to monitor CD4 T-cell responses in patients and the measurement of correlates of protection in vaccinated subjects.     

Antipeptide antibodies of predetermined specificity recognize and neutralize the bioactivity of the pan-specific hemopoietin interleukin 3

Ten peptides that corresponded to portions of the T cell lymphokine pan-specific hemopoietin interleukin 3 (IL 3) were synthesized, coupled to keyhole limpet hemocyanin, and used to raise antipeptide antibodies in rabbits. These antisera reacted to varying degrees with native biologically active IL 3. Antibodies directed against peptides corresponding to residues 1-29 at the NH2 terminus, 123-140 at the COOH terminus, and to residues 64-82 and 91-112 were affinity-purified on peptide columns. Immunoabsorbent columns produced from affinity-purified antibodies to the 1-29, 91-112, and 123-140 although not the 64-82 peptide were effective in depleting biologically active IL 3 from conditioned medium. However, the antibodies specific for peptides 91-112 and 123-140 had only a low affinity for native IL 3 and it was only in the case of the anti-1-29 antibodies that a significant amount of IL 3 remained bound after extensive washing and could be recovered from the column by acid elution. The affinity-purified antibodies directed to peptides 1-29, 91-112, and 123-140 significantly inhibited the biological activity of IL 3, although with different dose-response characteristics. Anti-1-29 antibodies inhibited bioactivity over a wide range of concentrations (down to 20 ng/ml) although the inhibition was never complete. In contrast, the anti-91-112 antibodies, although effective only at high concentrations, produced complete inhibition of biological activity. These experiments demonstrated that antibodies to defined peptides can be used to generate antibodies to native IL 3 and should form useful tools in analyzing the structure and function of the native molecules.     

Reverse immunogenetics: from HLA-disease associations to vaccine candidates

Analysis of the human leukocyte antigens (HLA) in patients with either infectious or autoimmune diseases has led to the identification of several HLA alleles associated with either resistance or susceptibility to disease. Understanding the role of HLA molecules in the presentation of peptide antigens to T cells has led to the use of ‘reverse immunogenetics’: a novel approach to analysing the key antigenic peptides that are presented by the relevant HLA molecules. Recent advances in the analysis of naturally occurring peptides bound to HLA molecules has allowed the direct identification of antigenic peptides from living cells and has supported the development of vaccine candidates, such as the liver-stage antigen 1 in malaria.     

Antibodies against synthetic fragments of the prion protein for the diagnosis of bovine spongiform encephalopathy

Seven peptides matching fragments of the prion protein and containing from 17 to 31 amino acid residues were synthesized to obtain antibodies for diagnostics of bovine spongiform encephalopathy. Rabbits were immunized with either free peptides or peptide-protein conjugates to result in sera with a high level of antipeptide antibodies. Immunohistochemical assay revealed sera against four free peptides and a protein-peptide conjugate, which effectively bind to the pathogenic isoform of the prion protein in brain tissue preparations from cattle afflicted with bovine spongiform encephalopathy and do not interact with normal brain preparations. The resulting antipeptide sera can be used in developing a diagnostic kit for bovine spongiform encephalopathy.     

Use of synthetic peptides to map the antigenic determinants of glycoprotein D of herpes simplex virus.

The predictive algorithm Surfaceplot (J.M.R. Parker, D. Guo, and R.S. Hodges, Biochemistry 25:5425-5432, 1986) was used to examine glycoprotein D of herpes simplex virus type 1 (HSV-1) for amino acid residues with a high probability of being exposed on the molecular surface. Based on these data, 11 different peptides corresponding to 10-residue segments in the primary sequence of glycoprotein D and one 20-residue segment were synthesized, conjugated to carrier proteins, and used to generate specific antisera in rabbits. Two synthetic peptides predicted not to be on the surface of glycoprotein D were included as negative controls. The polyclonal antisera against individual synthetic peptide conjugates were in turn evaluated for their ability to recognize both isolated glycoprotein D and intact HSV-1 virions in an enzyme-linked immunosorbent assay. Based on Surfaceplot predictions, eight linear antigenic sites on glycoprotein D were thereby defined from the 12 antipeptide antisera prepared. Four of these sites contained epitopes to which complement-independent neutralizing antibodies could be generated. The latter sites corresponded to sequences 12 to 21, 267 to 276, 288 to 297, and 314 to 323 of the mature protein. An additional peptide sequence, 2 to 21, was found to generate antisera which had potent virus-neutralizing capacity in the presence of complement. Identification of a neutralizing epitope in the sequence 314 to 323 makes it likely that the membrane-spanning region of glycoprotein D is within the subsequent sequence, 323 to 339. Antipeptide antisera prepared in this study from 12 synthetic peptides contained 13 surface sites predicted by Surfaceplot, of which 7 were not predicted by the parameters of Hopp and Woods (Proc. Natl. Acad. Sci. USA 78:3824-3828, 1981). Of these seven sites not predicted by the Hopp and Woods plot, all generated antipeptide antibodies that bound to HSV-1 virions and three of these seven sites generated neutralizing antibodies. In total, 8 of 12 synthetic peptides containing surface regions produced antipeptide antibodies that bound to HSV-1 virions and 5 of these generated neutralizing antibodies. These results suggest the advantages of Surfaceplot in mapping antigenic determinants in proteins.