Mat_peptide: comprehensive annotation of mature peptides from polyproteins in five virus families

MOTIVATION

Sequence repositories have few well-annotated virus mature peptide sequences. Therefore post-translational proteolytic processing of polyproteins into mature peptides (MPs) has been performed in silico, with a new computational method, for over 200 species in 5 pathogenic virus families (Caliciviridae, Coronaviridae, Flaviviridae, Picornaviridae and Togaviridae).

RESULTS

Using pairwise alignment with reference sequences, MPs have been annotated and their sequences made available for search, analysis and download. At publication the method had produced 156 216 sequences, a large portion of the protein sequences now available in https://www.viprbrc.org. It represents a new and comprehensive mature peptide collection.

AVAILABILITY AND IMPLEMENTATION

The data are available at the Virus Pathogen Resource https://www.viprbrc.org, and the software at https://github.com/VirusBRC/vipr_mat_peptide.

Influenza Research Database: An integrated bioinformatics resource for influenza virus research

The Influenza Research Database (IRD) is a U.S. National Institute of Allergy and Infectious Diseases (NIAID)-sponsored Bioinformatics Resource Center dedicated to providing bioinformatics support for influenza virus research. IRD facilitates the research and development of vaccines, diagnostics and therapeutics against influenza virus by providing a comprehensive collection of influenza-related data integrated from various sources, a growing suite of analysis and visualization tools for data mining and hypothesis generation, personal workbench spaces for data storage and sharing, and active user community support. Here, we describe the recent improvements in IRD including the use of cloud and high performance computing resources, analysis and visualization of user-provided sequence data with associated metadata, predictions of novel variant proteins, annotations of phenotype-associated sequence markers and their predicted phenotypic effects, hemagglutinin (HA) clade classifications, an automated tool for HA subtype numbering conversion, linkouts to disease event data and the addition of host factor and antiviral drug components. All data and tools are freely available without restriction from the IRD website at https://www.fludb.org.

Influenza research database: an integrated bioinformatics resource for influenza research and surveillance

Please cite this paper as: Squires et al. (2012) Influenza research database: an integrated bioinformatics resource for influenza research and surveillance. Influenza and Other Respiratory Viruses 6(6), 404–416.

Background  The recent emergence of the 2009 pandemic influenza A/H1N1 virus has highlighted the value of free and open access to influenza virus genome sequence data integrated with information about other important virus characteristics.

Design  The Influenza Research Database (IRD, http://www.fludb.org) is a free, open, publicly‐accessible resource funded by the U.S. National Institute of Allergy and Infectious Diseases through the Bioinformatics Resource Centers program. IRD provides a comprehensive, integrated database and analysis resource for influenza sequence, surveillance, and research data, including user‐friendly interfaces for data retrieval, visualization and comparative genomics analysis, together with personal log in‐protected ‘workbench’ spaces for saving data sets and analysis results. IRD integrates genomic, proteomic, immune epitope, and surveillance data from a variety of sources, including public databases, computational algorithms, external research groups, and the scientific literature.

Results  To demonstrate the utility of the data and analysis tools available in IRD, two scientific use cases are presented. A comparison of hemagglutinin sequence conservation and epitope coverage information revealed highly conserved protein regions that can be recognized by the human adaptive immune system as possible targets for inducing cross‐protective immunity. Phylogenetic and geospatial analysis of sequences from wild bird surveillance samples revealed a possible evolutionary connection between influenza virus from Delaware Bay shorebirds and Alberta ducks.

Conclusions  The IRD provides a wealth of integrated data and information about influenza virus to support research of the genetic determinants dictating virus pathogenicity, host range restriction and transmission, and to facilitate development of vaccines, diagnostics, and therapeutics.

ViPR: an open bioinformatics database and analysis resource for virology research

The Virus Pathogen Database and Analysis Resource (ViPR, www.ViPRbrc.org) is an integrated repository of data and analysis tools for multiple virus families, supported by the National Institute of Allergy and Infectious Diseases (NIAID) Bioinformatics Resource Centers (BRC) program. ViPR contains information for human pathogenic viruses belonging to the Arenaviridae, Bunyaviridae, Caliciviridae, Coronaviridae, Flaviviridae, Filoviridae, Hepeviridae, Herpesviridae, Paramyxoviridae, Picornaviridae, Poxviridae, Reoviridae, Rhabdoviridae and Togaviridae families, with plans to support additional virus families in the future. ViPR captures various types of information, including sequence records, gene and protein annotations, 3D protein structures, immune epitope locations, clinical and surveillance metadata and novel data derived from comparative genomics analysis. Analytical and visualization tools for metadata-driven statistical sequence analysis, multiple sequence alignment, phylogenetic tree construction, BLAST comparison and sequence variation determination are also provided. Data filtering and analysis workflows can be combined and the results saved in personal 'Workbenches' for future use. ViPR tools and data are available without charge as a service to the virology research community to help facilitate the development of diagnostics, prophylactics and therapeutics for priority pathogens and other viruses.

Effects of pentobarbital on upper airway patency during sleep

We hypothesised that pentobarbital would improve upper airway mechanics based on an increase in latency to arousal and amplitude of the phasic genioglossus electromyogram (EMG), and a decrease in the active upper airway critical closing pressure (P(crit)). 12 healthy subjects received pentobarbital (100 mg) or placebo in a double-blind, crossover protocol. During wakefulness, we measured the genioglossus reflex response to negative pressure pulses. During sleep, carbon dioxide was insufflated into the inspired air. Airway pressure was then decreased in a stepwise fashion until arousal from sleep. With basal breathing during sleep: flow rate was lower in volunteers given pentobarbital; end-tidal CO(2) concentration and upper airway resistance were greater; and P(crit) was unaffected (pentobarbital mean ± SD -11.7 ± 4.5 versus placebo -10.25 ± 3.6 cmH(2)O; p = 0.11). Pentobarbital increased the time to arousal (297 ± 63s versus 232 ± 67 s; p<0.05), at which time phasic genioglossus EMG was higher (6.2 ± 4.8% maximal versus 3.1 ± 3%; p<0.05) as were CO(2) levels. The increase in genioglossus EMG after CO(2) administration was greater after pentobarbital versus placebo. Pentobarbital did not affect the genioglossus negative-pressure reflex. Pentobarbital increases the time to arousal and stimulates genioglossus muscle activity, but it also increases upper airway resistance during sleep.

Text-mining of PubMed abstracts by natural language processing to create a public knowledge base on molecular mechanisms of bacterial enteropathogens

BACKGROUND

The Enteropathogen Resource Integration Center (ERIC; http://www.ericbrc.org) has a goal of providing bioinformatics support for the scientific community researching enteropathogenic bacteria such as Escherichia coli and Salmonella spp. Rapid and accurate identification of experimental conclusions from the scientific literature is critical to support research in this field. Natural Language Processing (NLP), and in particular Information Extraction (IE) technology, can be a significant aid to this process.

DESCRIPTION

We have trained a powerful, state-of-the-art IE technology on a corpus of abstracts from the microbial literature in PubMed to automatically identify and categorize biologically relevant entities and predicative relations. These relations include: Genes/Gene Products and their Roles; Gene Mutations and the resulting Phenotypes; and Organisms and their associated Pathogenicity. Evaluations on blind datasets show an F-measure average of greater than 90% for entities (genes, operons, etc.) and over 70% for relations (gene/gene product to role, etc). This IE capability, combined with text indexing and relational database technologies, constitute the core of our recently deployed text mining application.

CONCLUSION

Our Text Mining application is available online on the ERIC website (http://www.ericbrc.org/portal/eric/articles). The information retrieval interface displays a list of recently published enteropathogen literature abstracts, and also provides a search interface to execute custom queries by keyword, date range, etc. Upon selection, processed abstracts and the entities and relations extracted from them are retrieved from a relational database and marked up to highlight the entities and relations. The abstract also provides links from extracted genes and gene products to the ERIC Annotations database, thus providing access to comprehensive genomic annotations and adding value to both the text-mining and annotations systems.

Neostigmine but not sugammadex impairs upper airway dilator muscle activity and breathing

BACKGROUND

Cholinesterase inhibitor-based reversal agents, given in the absence of neuromuscular block, evoke a partial upper airway obstruction by decreasing skeletal upper airway muscle function. Sugammadex reverses neuromuscular block by encapsulating rocuronium. However, its effects on upper airway integrity and breathing are unknown.

METHODS

Fifty-one adult male rats were anaesthetized with isoflurane, tracheostomized, and a femoral artery and vein were cannulated. First, we compared the efficacy of sugammadex 15 mg kg(-1) and neostigmine 0.06 mg kg(-1) to reverse respiratory effects of rocuronium-induced partial paralysis [train-of-four ratio (T4/T1)=0.5]. Subsequently, we compared the safety of sugammadex and neostigmine given after recovery of the T4/T1 to 1, by measuring phasic genioglossus activity and breathing.

RESULTS

During partial paralysis (T4/T1=0.5), time to recovery of minute volume to baseline values was 10.9 (2), 75.8 (18), and 153 (54) s with sugammadex, neostigmine, and placebo, respectively (sugammadex was significantly faster than neostigmine and placebo, P<0.05). Recovery of T4/T1 was also faster for sugammadex than neostigmine and placebo. Neostigmine administration after complete recovery of T4/T1 decreased upper airway dilator muscle activity to 64 (30)% of baseline and decreased tidal volume (P<0.05 for both variables), whereas sugammadex had no effect on either variable.

CONCLUSIONS

In contrast to neostigmine, which significantly impairs upper airway dilator muscle activity when given after recovery from neuromuscular block, a reversal dose of sugammadex given under the same conditions does not affect genioglossus muscle activity and normal breathing. Human studies will be required to evaluate the clinical relevance of our findings.

A new asset for pathogen informatics--the Enteropathogen Resource Integration Center (ERIC), an NIAID Bioinformatics Resource Center for Biodefense and Emerging/Re-emerging Infectious Disease

ERIC (Enteropathogen Resource Information Center) is one of the National Institute of Allergy and Infectious Diseases (NIAID) Bioinformatics Resource Centers for Biodefense and Emerging/Re-emerging Infectious Disease. ERIC serves as a comprehensive information resource for five related pathogens: Yersinia enterocolitica, Yersinia pestis, diarrheagenic E. coli, Shigella spp., and Salmonella spp. ERIC integrates genomics, proteomics, biochemical and microbiological information to facilitate the interpretation and understanding of ERIC pathogens and select related non-pathogens for the advancement of diagnostics, therapeutics, and vaccines. ERIC (www.ericbrc.org) is evolving to provide state-of-the-art analysis tools and data types, such as genome sequencing, comparative genomics, genome polymorphisms, gene expression, proteomics, and pathways as well as expertly curated community genome annotation. Genome sequence and genome annotation data and a variety of analysis and tools for eight strains of Yersinia enterocolitica and Yersinia pestis pathogens (Yersinia pestis biovars Mediaevalis KIM, Mediaevalis 91001, Orientalis CO92, Orientalis IP275, Antiqua Angola, Antiqua Antiqua, Antiqua Nepal516, and Yersinia enterocolitica 8081) and two strains of Yersinia pseudotuberculosis (Yersinia pseudotuberculosis IP32953 and IP31758) are currently available through the ERIC portal. ERIC seeks to maintain a strong collaboration with the scientific community so that we can continue to identify and incorporate the latest research data, tools, and training to best meet the current and future needs of the enteropathogen research community. All tools and data developed under this NIAID contract will be freely available. Please contact info@ericbrc.org for more information.

Enteropathogen Resource Integration Center (ERIC): bioinformatics support for research on biodefense-relevant enterobacteria

ERIC, the Enteropathogen Resource Integration Center (www.ericbrc.org), is a new web portal serving as a rich source of information about enterobacteria on the NIAID established list of Select Agents related to biodefense—diarrheagenic Escherichia coli, Shigella spp., Salmonella spp., Yersinia enterocolitica and Yersinia pestis. More than 30 genomes have been completely sequenced, many more exist in draft form and additional projects are underway. These organisms are increasingly the focus of studies using high-throughput experimental technologies and computational approaches. This wealth of data provides unprecedented opportunities for understanding the workings of basic biological systems and discovery of novel targets for development of vaccines, diagnostics and therapeutics. ERIC brings information together from disparate sources and supports data comparison across different organisms, analysis of varying data types and visualization of analyses in human and computer-readable formats.

Cancer vaccine development

A new era involving the evaluation of recombinant cancer vaccines has begun with the concurrent emergence of insights and technologies in the fields of molecular biology and immunology. These advances include: The identification and cloning of an array of genes associated with the neoplastic process, such as oncogenes, suppressor genes, genes encoding oncofoetal antigens and tissue-lineage determinants. The development of a variety of viral and bacterial vectors to deliver and present gene products. The identification of numerous T-cell costimulatory molecules and an understanding of their mode of action. The cloning and analysis of the modes of action of an array of cytokines and other immunomodulatory molecules. More sophisticated knowledge of the mode(s) of antigen presentation and T-cell activation. One current challenge in cancer therapy is the delineation of strategies toward the rational design and implementation of recombinant vaccines that will be of therapeutic benefit to cancer patients and/or members of groups at high risk for specific neoplasias. Numerous concepts are emerging in this regard. The study of immunologic intervention using laboratory animal models demonstrates that no one approach will prevail for all cancer types or, perhaps, for the various stages of the neoplastic process of a given tumour type. The immunological role(s) of CD8+, CD4+, natural killer and other cell types, as well as the roles of antibodies, must all be taken into consideration. This article reviews some of the strategies currently undergoing evaluation toward the development of recombinant vaccines for several carcinoma types.

Agonist peptide from a cytotoxic t-lymphocyte epitope of human carcinoembryonic antigen stimulates production of tc1-type cytokines and increases tyrosine phosphorylation more efficiently than cognate peptide

The identification of an agonist peptide (YLSGADLNL, designated CAP1-6D) to an immunodominant cytotoxic T-lymphocyte (CTL) epitope (designated CAP1) of human carcinoembryonic antigen (CEA) has previously been reported. The agonist peptide harbors a single amino acid substitution at a non-MHC anchor residue and is proposed to exert its effects at the level of the T-cell receptor (TCR). The type and magnitude of cytokines produced by CAP1-reactive CTL upon stimulation with the agonist peptide, CAP1-6D, were compared to those obtained upon stimulation with the cognate CAP1 peptide. In addition, early events in the TCR signaling pathway were examined for differences in tyrosine phosphorylation. Upon stimulation with the agonist peptide CAP1-6D, several different CEA-specific CTL lines exhibited a marked shift in the peptide dose response, which resulted in as much as a 1,000-fold increase in the levels of GM-CSF and gamma-IFN produced as compared with the use of the CAP1 peptide. However, levels of IL-4 and IL-10, which are associated with anti-inflammatory effects, were very low or non-existent. The cytokine profile of CAP1- and CAP1-6D-specific CTL is consistent with a Tc1-type CTL. Consistent with these findings, CEA-specific CTL showed increased tyrosine phosphorylation of TCR signaling proteins ZAP-70 and TCR zeta chains in response to both peptides. However, when CAP1-6D was compared with the wild-type peptide, the increase in ZAP-70 phosphorylation was greater than the increase in zeta phosphorylation. CTL generated with the CAP1-6D agonist were shown capable of lysis of human carcinoma cells expressing native CEA. The ability to upregulate the production of GM-CSF, gamma-IFN, TNFalpha and IL-2 with the agonist peptide, as compared with CAP1, may help in initiating or sustaining anti-tumor immune responses and thus potentially prove to be useful in the treatment of CEA-positive tumors.

Strategies in the development of recombinant vaccines for colon cancer

A new era involving the evaluation of recombinant vaccines for colon cancer has begun with the concurrent emergence of insights and technologies in the fields of molecular biology and immunology. These advances include (I) the identification and cloning of an array of genes associated with the neoplastic process, such as oncogenes, suppressor genes, genes encoding oncofetal antigens, and tissue lineage determinants; (2) the development of a variety of viral and bacterial vectors to deliver and present gene products; (3) the identification of numerous T-cell costimulatory molecules and the knowledge of their mode of action; (4) the cloning and analysis of the modes of action of an array of cytokines and other immunomodulatory molecules; and (5) a more sophisticated knowledge of the mode(s) of antigen presentation and T-cell activation.

Generation of human cytolytic T lymphocyte lines directed against prostate-specific antigen (PSA) employing a PSA oligoepitope peptide

Prostate-specific Ag (PSA), which is expressed in a majority of prostate cancers, is a potential target for specific immunotherapy. Previous studies have shown that two 10-mer PSA peptides (designated PSA-1 and PSA-3) selected to conform to human HLA class I-A2 motifs can elicit CTL responses in vitro. A longer PSA peptide (30-mer) designated PSA-OP (oligoepitope peptide), which contains both the PSA-1 and PSA-3 HLA-A2 epitopes and an additional potential CTL epitope (designated PSA-9) for the HLA-class I-A3 allele, was investigated for the ability to induce cytotoxic T cell activity. T cell lines from different HLA-A2 and HLA-A3 donors were established by in vitro stimulation with PSA-OP; the CTL lines lysed PSA-OP as well as PSA-1- or PSA-3-pulsed C1R-A2 cells, and PSA-OP and PSA-9-pulsed C1R-A3 cells, respectively. The CTL lines derived from the PSA-OP peptide also lysed PSA-positive prostate cancer cells. PSA-OP-derived T cell lines also lysed recombinant vaccinia-PSA-infected targets but not targets infected with wild-type vaccinia. PSA-OP did not bind HLA-A2 and HLA-A3 molecules. The decrease in cytotoxicity in the presence of protease inhibitors suggests that the PSA-OP is cleaved into shorter peptides, which in turn can interact with HLA-class I molecules and, as a consequence, induce CTL-mediated lysis. We have also demonstrated that it is possible to induce CTL responses in HLA-A2.1/Kb transgenic mice by immunization with PSA-OP with adjuvant. These studies thus provide evidence that oligopeptides such as PSA-OP may be useful candidates for peptide-based cancer vaccines.

Generation of Human Cytolytic T Lymphocyte Lines Directed Against Prostate-Specific Antigen (PSA) Employing a PSA Oligoepitope Peptide

Prostate-specific Ag (PSA), which is expressed in a majority of prostate cancers, is a potential target for specific immunotherapy. Previous studies have shown that two 10-mer PSA peptides (designated PSA-1 and PSA-3) selected to conform to human HLA class I-A2 motifs can elicit CTL responses in vitro. A longer PSA peptide (30-mer) designated PSA-OP (oligoepitope peptide), which contains both the PSA-1 and PSA-3 HLA-A2 epitopes and an additional potential CTL epitope (designated PSA-9) for the HLA-class I-A3 allele, was investigated for the ability to induce cytotoxic T cell activity. T cell lines from different HLA-A2 and HLA-A3 donors were established by in vitro stimulation with PSA-OP; the CTL lines lysed PSA-OP as well as PSA-1- or PSA-3-pulsed C1R-A2 cells, and PSA-OP and PSA-9-pulsed C1R-A3 cells, respectively. The CTL lines derived from the PSA-OP peptide also lysed PSA-positive prostate cancer cells. PSA-OP-derived T cell lines also lysed recombinant vaccinia-PSA-infected targets but not targets infected with wild-type vaccinia. PSA-OP did not bind HLA-A2 and HLA-A3 molecules. The decrease in cytotoxicity in the presence of protease inhibitors suggests that the PSA-OP is cleaved into shorter peptides, which in turn can interact with HLA-class I molecules and, as a consequence, induce CTL-mediated lysis. We have also demonstrated that it is possible to induce CTL responses in HLA-A2.1/Kb transgenic mice by immunization with PSA-OP with adjuvant. These studies thus provide evidence that oligopeptides such as PSA-OP may be useful candidates for peptide-based cancer vaccines.

Olanzapine compared with chlorpromazine in treatment-resistant schizophrenia

OBJECTIVE

The purpose of this study was to compare the efficacy of olanzapine with that of chlorpromazine plus benztropine in patients with treatment-resistant schizophrenia.

METHOD

One hundred three previously treatment-resistant patients with schizophrenia diagnosed according to the DSM-III-R criteria were given a prospective 6-week trial of 10-40 mg/day of haloperidol. Eighty-four of them failed to respond to that trial and agreed to be randomly assigned to an 8-week fixed-dose trial of either 25 mg/day of olanzapine alone or 1200 mg/day of chlorpromazine plus 4 mg/day of benztropine mesylate.

RESULTS

Fifty-nine (70%) of the 84 subjects completed the trial. The primary outcome measures were Brief Psychiatric Rating Scale total score and positive symptom score, Scale for the Assessment of Negative Symptoms global score, and Clinical Global Impression score. An analysis of variance for the subjects who completed the study showed no difference in efficacy between the two drugs. Seven percent of the olanzapine-treated patients responded according to a priori criteria; no chlorpromazine-treated patients responded. The olanzapine-treated patients had fewer motor and cardiovascular side effects than the chlorpromazine-treated patients. Extrapyramidal symptoms and akathisia were similar in the two groups, although no antiparkinsonian drugs were used in the olanzapine group.

CONCLUSIONS

Olanzapine and chlorpromazine showed similar efficacy, and the total amount of improvement with either drug was modest. Olanzapine-treated patients had fewer side effects than chlorpromazine-treated patients.

Phenotypic stability of a cytotoxic T-cell line directed against an immunodominant epitope of human carcinoembryonic antigen

CTL lines have now been generated against defined peptides of a range of human tumor-associated antigens (TAAs). One of the potential uses of these epitope-specific CTLs is in adoptive transfer immunotherapy. This is a modality, however, that will require long-term in vitro culture of CTLs. To date, little has been reported concerning the phenotypic stability of human epitope-specific CTLs as a consequence of long-term in vitro propagation via peptide stimulation. We report here the serial phenotypic characterization of a CTL line directed against an immunodominant epitope (YLSGANLNL, designated CAP-1) of human carcinoembryonic antigen (CEA). This CTL line was derived from peripheral blood mononuclear cells of a patient with metastatic carcinoma who had been treated with a recombinant CEA-vaccinia vaccine in a Phase I trial; the CTLs were analyzed through 20 in vitro cycle passages of stimulation with CAP-1 peptide and interleukin 2 in the presence of autologous antigen-presenting cells. The CTL line was shown to be phenotypically stable in terms of high levels of cytokine (IFN-gamma, tumor necrosis factor, and granulocyte-macrophage colony-stimulating factor) production, expression of homing-adhesion molecules, ability to lyse peptide-pulsed targets, and ability to lyse human carcinoma cells endogenously expressing CEA in a MHC-restricted manner. Vbeta T-cell receptor gene usage was also analyzed. These studies thus present a rationale for the use of long-term cultured epitope-specific human CTLs, directed against a human TAA for potential adoptive transfer immunotherapy protocols.

Identification of an enhancer agonist cytotoxic T lymphocyte peptide from human carcinoembryonic antigen

A vaccination strategy designed to enhance the immunogenicity of self-antigens that are overexpressed in tumor cells is to identify and slightly modify immunodominant epitopes that elicit T-cell responses. The resultant T cells, however, must maintain their ability to recognize the native configuration of the peptide-MHC interaction on the tumor cell target. We used a strategy to enhance the immunogenicity of a human CTL epitope directed against a human self-antigen, which involved the modification of individual amino acid residues predicted to interact with the T-cell receptor; this strategy, moreover, required no prior knowledge of these actual specific interactions. Single amino acid substitutions were introduced to the CAP1 peptide (YLSGANLNL), an immunogenic HLA-A2+-binding peptide derived from human carcinoembryonic antigen (CEA). In this study, four amino acid residues that were predicted to potentially interact with the T-cell receptor of CAP1-specific CTLs were systematically replaced. Analogues were tested for binding to HLA-A2 and for recognition by an established CTL line directed against CAP1. This line was obtained from peripheral blood mononuclear cells from an HLA-A2+ individual vaccinated with a vaccinia-CEA recombinant. An analogue peptide was identified that was capable of sensitizing CAP1-specific CTLs 10(2)-10(3) times more efficiently than the native CAP1 peptide. This enhanced recognition was shown not to be due to better binding to HLA-A2. Therefore, the analogue CAP1-6D (YLSGADLNL, Asn at position 6 replaced by Asp) meets the criteria of a CTL enhancer agonist peptide. Both the CAP1-6D and the native CAP1 peptide were compared for the ability to generate specific CTL lines in vitro from unimmunized apparently healthy HLA-A2+ donors. Whereas CAP1 failed to generate CTLs from normal peripheral blood mononuclear cells, the agonist peptide was able to generate CD8+ CTL lines that recognized both the agonist and the native CAP1 sequence. Most importantly, these CTLs were capable of lysing human tumor cells endogenously expressing CEA. The use of enhancer agonist CTL peptides may thus represent a new efficient direction for immunotherapy protocols.

In vitro generation of human cytotoxic T lymphocytes specific for peptides derived from prostate-specific antigen

BACKGROUND

Protein antigens are presented to cytotoxic T lymphocytes as small peptides (approximately 9-10 amino acids long) bound to class I molecules of the major histocompatibility complex. The identification of tumor-associated antigens and specific peptide epitopes (i.e., antigenic determinants) may be useful in the development of anticancer vaccines. The generation of a cytotoxic T-cell response to one peptide epitope (amino acids 146-154) of human prostate-specific antigen (PSA) has been reported.

PURPOSE

Our aim was to identify novel PSA peptides capable of eliciting specific cytotoxic T-cell responses.

METHODS

Candidate peptides were identified on the basis of the following criteria: 1) they contained consensus amino acid motifs for binding to HLA-A2, which is the most common type of class I molecule; 2) they lacked strong homology with PSA-related kallikrein proteins; and 3) they were capable of stabilizing HLA-A2 class I molecules on the surface of human T2 (transport deletion mutant) cells, which are defective in antigen presentation. T-cell lines capable of killing (i.e., lysing) T2 target cells that had been pulsed with specific PSA peptides were generated from three different males (two disease-free individuals and one patient with prostate cancer) by incubating peripheral blood mononuclear cells with the peptides and interleukin 2. Specific cell lysis was monitored by the release of radioactivity from target cells that had been labeled with [111In]oxyquinoline.

RESULTS

Two novel PSA peptides capable of eliciting cytotoxic T-cell responses were identified; these peptides were designated PSA-1 (amino acids 41-150) and PSA-3 (amino acids 154-163). Four different cytotoxic T-cell lines were generated in response to these peptides-three against PSA-3 and one against PSA-1. Specific lysis of peptide-pulsed T2 cells by the T-cell lines was blocked by the addition of a monoclonal antibody directed against class I molecules. The T-cell lines were also capable of lysing PSA-positive, HLA-A2-positive LNCaP cells (human prostate carcinoma cells). The specificity of LNCaP cell lysis was shown by the following: 1) the inability of added human K562 (chronic myelogenous leukemia) cells to inhibit it, 2) the ability of added anti-HLA-A2 antibodies to block it, and 3) the inability of the T-cell lines to induce substantial lysis of PSA-negative, HLA-A2-positive human cancer cells.

IMPLICATIONS

Our studies form a rational basis for the use of PSA peptides or recombinant vectors encoding PSA in the development of anticancer vaccine immunotherapy protocols for patients with prostate cancer.

Identification of overlapping epitopes in mutant ras oncogene peptides that activate CD4+ and CD8+ T cell responses

Mutant ras p21 proteins contain sequences which distinguish them from normal endogenous ras and, thus, may represent unique epitopes for T cell recognition of antigen bearing tumor cells. Here, we examined the capacity of a mutant K-ras 9-mer peptide to induce in vivo CD8+ cytotoxic T lymphocytes (CTL). The peptide chosen reflected positions 4-12 of the point-mutated sequence of the K-ras oncogene encoding the Gly to Val substitution at codon 12. The overall rationale for selecting this particular 9-mer sequence was threefold: the mutant peptide contained a putative major histocompatibility complex (MHC) class I consensus anchor motif for murine H-2Kd; specific binding to MHC class I may then create an immunogenic complex for the induction of anti-ras CD8+ CTL; and finally, the mutant sequence overlapped with a newly characterized anti-ras CD4+ T helper type 1 epitope, which may have implications for the coordination and activation of both anti-ras immune mechanisms against the same target cell antigenic determinant. A functional interaction with H-2Kd was demonstrated with the mutant ras4-12(V12) peptide, but not the normal ras4-12(G12) peptide, which specifically inhibited an H-2Kd-restricted, anti-nucleoprotein NP147-155 CTL response in a dose-dependent fashion. An anti-ras CD8+ T cell line was then established from immune splenocytes of BALB/c (H-2d) mice injected with ras4-12 (V12) in adjuvant, which mediated peptide-specific lysis of syngeneic P815 tumor targets. Cytotoxicity was restricted by H-2Kd and strongly specific for the mutant ras peptide. Importantly, these anti-ras CTL specifically lysed a syngeneic tumor line (i.e. A20 lymphoma) transduced with the corresponding point-mutated ras oncogene, suggesting T cell receptor recognition of endogenously derived antigen. Overall, these data demonstrated that mutant ras p21 at codon 12(Gly-->Val) contained a peptide sequence which exhibited specific functional binding to a murine MHC class I molecule; the ability of the mutant, but not the normal sequence to bind selectively to murine MHC class I likely reflected the generation of a C-terminal anchor residue; and the ras4-12(V12) peptide was immunogenic for the production of antigen-specific CD8+ CTL, which lysed in vitro a syngeneic tumor cell line harboring the mutant K-ras oncogene.

Peptide-specific activation of cytolytic CD4+ T lymphocytes against tumor cells bearing mutated epitopes of K-ras p21

Alterations in the ras p21 protein have been associated with both rodent and human neoplasia. Thus, mutated ras p21 proteins may bear unique antigenic epitopes for immune recognition, such as by T cells, which have been implicated in host antitumor activity. Synthetic peptides that mimic segments of mutated ras p21 have been reported to be immunogenic in mice in vivo, although detailed functional analyses remains undefined. Here, in a murine model, we explored and characterized distinct effector properties of host-derived T lymphocytes reactive to mutated ras peptides, which was consistent with the CD4+ T helper type 1 (Th1) subset. BALB/c mice (H-2d) were immunized with a purified peptide, 13 amino acids in length, containing the substitution of Gly (G12) to Val (V12) at position 12, which is commonly found in human carcinomas. An alpha beta T cell receptor-positive, CD3+, CD4+, CD8- T cell line was established, which expressed peptide-specific proliferation. Cytokine assays revealed the production of interleukin-2, interferon-gamma, tumor necrosis factor and granulocyte-macrophage colony-stimulating factor. Moreover, antigen-specific cytotoxicity was demonstrable against: (1) Iad-bearing A20 tumor cells incubated with exogenously bound V12 peptide; and (2) A20 tumor cells transduced with the K-ras p21 oncogene encoding the corresponding point mutation. CD4(+)-mediated cytotoxicity was major histocompatibility complex (MHC) class II-restricted, as revealed by the absence of lysis against MHC class II- P815 targets, inhibition of A20 lysis with anti-Iad monoclonal antibodies, and induction of lysis against L cell targets transfected with E alpha A beta d. Independent isolation of a second CD4+ V12 line revealed a very similar cytolytic and MHC class II-restricted profile. Overall, these data demonstrated that peptide immunization produced a CD4+ Th1 response that specifically recognized tumor cells expressing endogenous activated K-ras epitopes, which may have implications for the development of peptide-based active immunotherapies.

Generation of human cytotoxic T cells specific for human carcinoembryonic antigen epitopes from patients immunized with recombinant vaccinia-CEA vaccine

BACKGROUND

The human carcinoembryonic antigen (CEA), which is expressed in several cancer types, is a potential target for specific immunotherapy using recombinant vaccines. Previous studies have shown that when the CEA gene is placed into vaccinia virus, the recombinant vaccine (rV-CEA) can elicit T-cell responses in both rodents and non-human primates.

PURPOSE

Our objective was to determine if rVCEA could elicit CEA-specific T-cell responses in humans with appropriate human leukocyte antigen (HLA) motifs.

METHODS

Peripheral blood lymphocytes (PBLs) obtained from patients with metastatic carcinoma, both before and after vaccination with rV-CEA, were analyzed for T-cell response to specific 9- to 11-mer CEA peptides selected to conform to human HLA class I-A2 motifs.

RESULTS

While little or no T-cell growth was seen from preimmunization PBLs of patients pulsed with CEA peptides and interleukin 2 (IL-2), T-cell lines were obtained from PBLs of patients after vaccination with one to three cycles of stimulation. Cytolytic T-cell lines from three HLA-A2 patients were established with a 9-amino acid peptide (CAP-1), and the CD8+/CD4+ double-positive T-cell line (V24T) was chosen for detailed analysis. When autologous Epstein-Barr virus (EBV)-transformed B cells were either incubated with CAP-1 peptide or transduced with the CEA gene using a retroviral vector, they were lysed by the V24T cell line, but allogeneic non-A2 EBV-transformed B cells were not. The SW403 human colon carcinoma cell line, which is CEA positive and HLA-A2 positive, was also lysed by the V24T cell line, while two non-HLA-A2 CEA-positive colon carcinoma cell lines were not. To further confirm the class I HLA-A2 restricted nature of the V24T cytotoxicity, the non-HLA-A2 SW837 CEA-expressing colon carcinoma cell line was infected with a recombinant vaccinia virus expressing the HLA class I-A2 gene, and it became susceptible to V24T lysis. Cells infected with vector alone were not lysed.

CONCLUSIONS

This study demonstrates for the first time (a) the ability to generate a human cytolytic T-cell response to specific epitopes of CEA, (b) the class I HLA-A2 restricted nature of the T-cell mediated lysis, and (c) the ability of human tumor cells to endogenously process CEA to present a specific CEA peptide in the context of major histocompatibility complex for T-cell-mediated lysis.

IMPLICATIONS

These findings have implications in the development of specific second-generation cancer immunotherapy protocols.

Biologic properties of a CH2 domain-deleted recombinant immunoglobulin

Monoclonal antibody (MAb) B72.3 reacts with TAG-72, a high-molecular-weight mucin expressed on several types of human carcinoma, and is currently being used in clinical trials for the diagnosis and therapy of human carcinoma. An expression construct containing cDNA encoding an immunoglobulin (Ig) heavy chain, with the variable region of murine MAb B72.3 and a human Ig constant region with a deletion of the CH2 domain, was generated. Immunoglobulin from the transfectoma with the highest expression of the TAG-72 immunoreactive antibody was designated MAb chimeric (c) B72.3 delta CH2. The pharmacokinetics of serum clearance of iodine-labeled MAbs cB72.3 delta CH2 and the intact cB72.3 were compared in athymic mice. By 24 hr, less than 1% of the cB72.3 delta CH2 was left in the plasma, while 36% of the cB72.3 still remained. The T1/2 alpha values of the cB72.3 delta CH2 and cB72.3 MAbs were 1.7 and 2.4 hr, respectively. The T1/2 beta values were 7.8 hr for the domain-deleted cMAb and 48.9 hr for cB72.3. Biodistribution studies in athymic mice bearing LS-174T xenografts showed a reduction in the percentage of injected dose per gram in tumor with 131I-cB72.3 delta CH2; however, the 131I-cB72.3 delta CH2 both localized to tumors faster and cleared from the blood faster than the 125I-cB72.3 MAb. Only trace amounts of the 131I-cB72.3 delta CH2 were detected in normal tissues, including kidney. The faster clearance rate, more rapid tumor targeting and lack of metabolic uptake in normal tissues demonstrated with the iodine-labeled CH2 domain-deleted cMAb may be an advantage for certain clinical protocols.

Construction and purification of domain-deleted immunoglobulin variants of the recombinant/chimeric B72.3 (y1) monoclonal antibody

Chimeric antibodies have been produced against a pancarcinomic tumor associated antigen, TAG-72, by fusing the genes for the variable region of mouse MAb B72.3 to the genes for the constant region of human IgG. In our efforts to optimize the pharmacokinetics of plasma clearance and the efficiency of tumor localization and penetrance of cB72.3, we have now developed truncated versions of immunoglobulin heavy chains. The domain-deleted antibodies are produced by transfecting cells that produce chimeric kappa chains with expression vectors that encode chimeric heavy chains lacking the sequences that encode the CH2 domain, CH3 domain, or both. Despite the absence of these domains, the transfectomas secrete H2L2 tetramers with appropriate antigenic specificity. All the domain-deleted immunoglobulins can be purified by chromatography on Protein G Sepharose which binds to a site on the Fab region that is retained in the domain-deleted antibodies. The CH2CH3 domain-deleted immunoglobulin produced in cell culture is analogous in size to enzymatically produced F(ab')2.

Molecular and morphological changes in the cat lateral geniculate nucleus and visual cortex induced by visual deprivation are revealed by monoclonal antibodies Cat-304 and Cat-301

Monoclonal antibody Cat-301 recognizes a surface-associated proteoglycan on subsets of neurons in the mammalian CNS (Hockfield and McKay, 1983). The expression of Cat-301 immunoreactivity on Y cells in the cat LGN is sharply reduced by early visual deprivation (Sur et al., 1988). We employed an immunosuppression strategy (Hockfield, 1987) to further study alterations in the expression of experience-dependent molecules. Newborn BALB/c mice were injected with LGN from dark-reared cats to induce a suppression of the immune response to antigens expressed in visually deprived animals. These mice were then immunized with LGN from normal cats to elicit an immune response to antigens with an expression dependent on normal early visual experience. This strategy permitted the generation of monoclonal antibody Cat-304, which recognizes a surface-associated antigen on neuronal cell bodies and proximal dendrites, and which appears histologically identical to Cat-301. Further analyses show that Cat-304 and Cat-301 recognize different epitopes on the same 680-kDa chondroitin sulfate proteoglycan. We examined the effects of early visual deprivation on Cat-304 immunoreactivity in the LGN and visual cortex of cats. In LGN from normal cats, Cat-304 labels neurons in layers A, A1, and C, in interlaminar zones, and in the medial interlaminar nucleus. In LGN from dark-reared cats, the number of antibody-positive neurons is markedly reduced, and the cross-sectional area of the remaining positive neurons is smaller than normal. In cortical area 17 of normally reared cats, Cat 304-positive neurons are densely distributed in 2 bands, in layers IV and V/VI. Labeled neurons are also present in layers II and III. In area 17 of dark-reared cats, the number of antibody-positive neurons is reduced. The reduction in the number of labeled neurons is most pronounced in layers II/III and V/VI. Antibody-positive neurons are smaller in all cortical layers of dark-reared cats. The changes in the expression of Cat-301 immunoreactivity in dark-reared visual cortex and LGN are identical to those of Cat-304. The laminar differences in the effect of dark rearing on Cat-301 and Cat-304 expression in the visual cortex provides support for the suggestion that layer IV of cortical area 17 may be less susceptible to prolongation of plasticity by dark rearing than layers II/III and V/VI. Further, the biochemical and histological studies reported provide evidence that early visual experience regulates protein expression in the cat LGN and visual cortex.

Neuronal subsets express multiple high-molecular-weight cell-surface glycoconjugates defined by monoclonal antibodies Cat-301 and VC1.1

Cat-301 and VC1.1 are monoclonal antibodies that recognize surface-associated molecules on subsets of mammalian CNS neurons. Earlier work demonstrated that Cat-301 recognizes a 680-kDa chondroitin sulfate proteoglycan (PG). VC1.1 has been shown to recognize 3 polypeptide bands on Western blot analysis; a major band at 95-105 kDa and additional bands at 145 kDa and 170 kDa. In the present report, we show that VC1.1 also reacts with a high-molecular-weight glycoconjugate. Immunoprecipitation experiments and biochemical characterizations indicate that Cat-301 and VC1.1 define at least 3 distinct high-molecular-weight antigens. The VC1.1 antigens react with antikeratan sulfate antibodies, while the Cat-301 antigens do not. By immunodepletion, we show that some VC1.1 antigens are Cat-301 positive, while others are Cat-301 negative. In addition, Cat-301-reactive proteoglycans are heterogeneous with respect to the presence or absence of VC1.1 epitopes. Double-label immunofluorescence studies with these 2 antibodies are consistent with the biochemical results and show that there are 3 classes of immunoreactive neurons in the cat CNS:Cat-301+/VC1.1+, Cat-301-/VC1.1+, and Cat-301+/VC1.1-. These results indicate that structural microheterogeneity exists among Cat-301 and VC1.1 high-molecular-weight glycoconjugates. This heterogeneity may be a reflection of the diverse neuronal phenotypes that are recognized by Cat-301 and VC1.1 in the mammalian CNS.

Monoclonal antibody rat 401 recognizes Schwann cells in mature and developing peripheral nerve

Monoclonal antibody Rat 401 recognizes subsets of cells in the developing central and peripheral nervous systems. Previous studies have shown that in the central nervous system (CNS) Rat 401 immunoreactivity diminishes sharply with cellular differentiation. Here we have examined the time course, cellular localization, and biochemical nature of the Rat 401 antigen in the rat peripheral nerve. In contrast to the CNS, in the periphery Rat 401 immunoreactivity is maintained into adulthood. Rat 401 staining is restricted to Schwann cells in mature peripheral nerve. Myelin-related Schwann cells are intensely immunoreactive, whereas nonmyelin-related Schwann cells are weakly immunoreactive. Unlike many Schwann cell markers, Rat 401 staining is maintained in cultured Schwann cells that lack axon contact. Biochemical analyses show that the antigen recognized by Rat 401 in the peripheral nerve is identical to that in embryonic CNS. The results demonstrate that the capacity for maintained Rat 401 immunoreactivity is restricted to Schwann cells as these cells are stained in adult animals as well as in embryos. In contrast, the same antigens are lost from the CNS at an early stage of development.

Molecular differences among neurons reveal an organization of human visual cortex

Monoclonal antibody Cat-301 recognizes a cell-surface proteoglycan on subsets of neurons in several areas of the cat and macaque monkey central nervous system. In striate and extrastriate visual cortex of the macaque, the distribution of Cat-301-positive neurons demonstrates features of cellular organization that correlate with previously described functional subdivisions. Here we show that Cat-301 recognizes an antigen in human cortex that is closely related, if not identical, to the antigen in laboratory animals. Further, we use Cat-301 to demonstrate an organization of molecularly defined neurons in primary and secondary visual cortex (cortical areas V1 and V2) of the human. The organization demonstrated with Cat-301 in human area V1 correlates with the organization of ocular dominance columns demonstrated by cytochrome oxidase histochemistry. The organization demonstrated with Cat-301 in human area V2 correlates with the thick stripes of the cytochrome oxidase pattern. The present observations provide evidence for a visual pathway in human cortex homologous to the magnocellular pathway in macaque, a pathway involved in processing the low-contrast, achromatic, and moving components of visual stimuli.

Characterization of an activity-dependent, neuronal surface proteoglycan identified with monoclonal antibody Cat-301

Monoclonal antibody Cat-301 was previously shown to recognize a surface-associated antigen on subsets of mammalian CNS neurons whose expression is regulated by neuronal activity early in an animal's postnatal life. We now present the partial purification and characterization of the Cat-301 antigen and demonstrate that it is a chondroitin sulfate proteoglycan. Extracellular localization of the Cat-301 epitope is demonstrated by staining live, intact neurons in situ. Extraction of the antigen from membranes in the absence of detergent indicates that it is either a peripheral membrane protein or a component of an extracellular matrix. The Cat-301 antigen migrates on Western blots of SDS gels with a molecular weight of integral of 680,000 dalton and is purified by DEAE chromatography and Sepharose gel filtration in 8 M urea (pH 4.9) buffer. The antigen is sensitive to chondroitinase ABC, indicating that it is a chondroitin sulfate proteoglycan. Furthermore, we provide strong evidence that the biochemically characterized antigen is indeed the histologically detected species by using a second antibody, Cat-304, that produces immunohistological staining patterns identical to those of Cat-301 and reacts with the purified antigen, but at a distinct epitope. Our earlier developmental findings and the present localization and biochemical results suggest that the antigen may play a role in the maturation of functional connections between neurons, perhaps through stabilization of axosomatic and axodendritic synapses.

A reliable method for assessing topographical arrangement of proteins in the chromaffin granule membrane

An efficient and reliable method for preparing chromaffin granules and membranes for topographical analysis has been designed to meet the following criteria. Only labeling of truly intact organelles is analyzed for cytoplasmic surface probes. No resealing of open membranes occurs under specified reaction conditions. Saturation of available sites must be demonstrated. Problems in meeting these conditions are discussed, in particular the interference of granule lysate with labeling reactions.

Limited proteolytic digestion of coated vesicle assembly polypeptides abolishes reassembly activity

We have previously identified a fraction containing several assembly polypeptides (AP) that promotes reassembly of clathrin into vesicle-free coat structures [Zaremba S, Keen JH: J Cell Biol 97:1339, 1983]. The AP are prepared from purified bovine brain-coated vesicles by extraction with 0.5 M TRIS-HCl followed by Sepharose CL-4B column chromatography. Centrifugation in sucrose gradients under nonassembly conditions supports earlier observations suggesting that four active polypeptides in the AP preparation, of Mr approximately 110,000, 100,000, 50,000, and 16,500 are present in a discrete complex that is incorporated as a unit into reassembled coats. The 16,500-dalton polypeptide does not coelectrophorese with authentic bovine brain calmodulin and does not exhibit calmodulin's Ca2+-induced shift in electrophoretic mobility. When the partially purified AP fraction was digested with elastase, the Mr approximately 110,000 and 100,000 polypeptides were rapidly degraded with little or no effect on the Mr approximately 50,000 and 16,500 bands. This treatment abolished the in vitro coat-forming ability of the AP fraction and the loss of activity closely parallels the loss of the Mr approximately 100,000 band. Disappearance of the Mr approximately 110,000 and 100,000 bands is accompanied by the generation of new bands at Mr approximately 76,000 and 65,000. When the elastase-treated AP is examined by sucrose gradient sedimentation in nonassembly buffers, the new bands continue to cosediment with the Mr approximately 50,000 and 16,500 polypeptides. This indicates that the elastase digestion has cleaved off a fragment of the Mr approximately 110,000 and 100,000 bands, leaving behind a truncated, inactive AP complex. A protein kinase activity has been detected in coated vesicle preparations that utilizes the 50,000-dalton AP as its preferred substrate [Keen JH, Zaremba S: J Cell Biol 97:174a, 1983]. Elastase treatment does not abolish this activity, indicating that the kinase by itself is not sufficient for maintaining reassembly activity.

Assembly polypeptides from coated vesicles mediate reassembly of unique clathrin coats

A protein activity has been identified in extracts of coated vesicles that enables purified clathrin triskelions to reassemble in vitro into coat structures of uniform size. Coats formed in the presence of this preparation, regardless of the buffer system employed, are uniform in size with a mean diameter of 78 nm (+/- 5 nm SD) and a sedimentation coefficient (S20,w) of approximately 250S. Analysis of the reassembled coats on dodecyl sulfate acrylamide gels reveals that they have specifically incorporated three polypeptides from the preparation: those of Mr congruent to 52,000, 100,000, and 110,000. The 52,000-, 100,000-, and 110,000-mol-wt polypeptides are incorporated in molar ratios of 0.85, 1.11, and 0.26, respectively, per three clathrin monomers (equivalent to one triskelion). We therefore designate these as assembly polypeptides (AP). In contrast, coats formed from clathrin alone, under permissive buffer conditions, are larger (400S), more heterogeneous in size (101 nm +/- 15 nm SD), and are composed only of clathrin and its associated light chains. These biochemical and biophysical characteristics distinguish AP-reassembled coats from coats formed by triskelions alone. AP-reassembled coats can be isolated, dissociated, then reassembled in the absence of any other factors. This recycling indicates that all the information needed for reassembly is present in the coat-incorporated polypeptides themselves. Reassembly is stoichiometric and saturable with respect to both clathrin and AP concentration. In the presence of AP, significant coat reassembly occurs at clathrin concentrations as low as 0.06 mg/ml. AP-mediated reassembly proceeds at 4 degrees, 22 degrees, and 37 degrees C. Coat formation also proceeds efficiently at intracellular pH values (7.2-7.5) in the presence of AP. In its absence, reassembly does not occur at all above pH 6.7. In summary, AP promotes clathrin reassembly into coat structures of uniform size and distinctive composition under physiologically relevant salt, temperature, and pH conditions. In addition, the close similarity in size between AP-reassembled coats in vitro and coated membranes in the Golgi region in vivo raises the possibility that AP in the cell may be associated with this subpopulation of coat structures.

Transmembrane nature of chromaffin granule dopamine beta-monooxygenase

The topographical arrangement of membrane-bound dopamine beta-monooxygenase in the chromaffin granule was investigated by proteolytic treatment and radiolabeling of intact granules or the isolated granule membranes. Topographical analysis was furthered by precipitating detergent extracts of treated membranes with specific antibodies to dopamine beta-monooxygenase, followed by electrophoresis of the immunoprecipitate in acrylamide-dodecyl sulfate. Trypsin or pronase treatment of intact granules cleaved small portions of membrane-bound dopamine beta-monooxygenase, resulting in proteins with slightly lower molecular weights. Membranes bearing these smaller forms of membrane-bound dopamine beta-monooxygenase were fully active enzymatically. Pronase treatment of isolated membranes cleaved all of the membrane-bound dopamine beta-monooxygenase antigenic sites from the membrane and also removed the enzymatic activity. Lactoperoxidase-catalyzed iodination revealed that membrane-bound dopamine beta-monooxygenase can be labeled in intact granules, but to a greater extent in isolated membranes. Quantitative peptide mapping showed that the distribution of label among tryptic peptides of membrane-bound dopamine beta-monooxygenase differed, depending on whether intact granules or isolated membranes had been labeled. The results of these experiments provide evidence that membrane-bound dopamine beta-monooxygenase is a transmembrane protein which has its active site exclusively on the intragranular face, plus a unique portion of its polypeptide chain exposed on the cytoplasmic face of the intact granule.