Safety and immunogenicity of an intranasal Pseudomonas aeruginosa hybrid outer membrane protein F-I vaccine in human volunteers

A hybrid protein [Met-Ala-(His)(6) OprF(190-342)-OprI(21-83)] consisting of the mature outer membrane protein I (OprI) and amino acids 190-342 of OprF of Pseudomonas aeruginosa was expressed in Escherichia coli and purified by Ni(2+) chelate-affinity chromatography. After several studies in healthy volunteers, as well as in patients, had proven the tolerability and immunogenicity of the the OprF-OprI vaccine, after intra-muscular application, we developed an emulgel for intranasal immunization. For this purpose we combined a highly concentrated OprF-I with sodium dodecylsulfate as vehicle and the gel matrix natriumlauryl sulfate. After safety and pyrogenicity evaluations in animals, eight healthy adult human volunteers received the OprF-I gel intranasally three times at 2-week intervals. The vaccination was well tolerated and no side effects were observed. An antibody induction (IgG and IgA) could be detected in the sera. These data support continued clinical investigation of the protection against infections in cystic fibrosis patients and patients prone to P. aeruginosa infections.

The genome of the archaeal virus SIRV1 has features in common with genomes of eukaryal viruses

The virus SIRV1 of the extremely thermophilic archaeon Sulfolobus has a double-stranded DNA genome similar in architecture to the genomes of eukaryal viruses of the families Poxviridae, Pycodnaviridae, and Asfarviridae: the two strands of the 32,301 bp long linear genome are covalently connected forming a continuous polynucleotide chain and 2029 kb long inverted repeats are present at the termini. Very likely it also shares with these viruses mechanisms of initiation of replication and resolution of replicative intermediates.

Immunogenic efficacy of differently produced recombinant vaccines candidates against Pseudomonas aeruginosa infections

Three different variants of the recombinant hybrid outer membrane protein OprF (aa 190-342)-OprI (aa 21-83) could be obtained in high yield after expression in Escherichia coli. The hybrid protein was modified N terminally, either with a minimal histidine tag or with a homologous sequence of OprF. Both recombinant proteins were purified by nickel chelate affinity chromatography under native and denaturing conditions, and this produced three suitable candidates for a vaccination trial, protein His-F-I, which was purified in its native as well as in its refolded form; and the native purified N terminally extended protein, ex-F-I. In mice, significantly higher antibody titers and survival rates after challenge with Pseudomonas aeruginosa were observed following immunization with protein His-F-I, purified under native conditions.

A recombinant hybrid outer membrane protein for vaccination against Pseudomonas aeruginosa

Among the numerous targets which can be used for the development of vaccines against Pseudomonas aeruginosa we focused on the outer membrane proteins OprF and OprI. The C-terminal part of OprF from aa 190 to aa 350 was investigated for its conservation and its localization of B-cell epitopes. A hybrid protein which combines the protective epitopes of OprF and OprI was expressed in E. coli and was proven to be highly protective against an intraperitoneal challenge with P. aeruginosa by active immunization of immunocompromised mice as well as by passive immunization of SCID mice with specific antisera. A purification procedure of the N-terminal His-tagged hybrid antigen was established using immobilized-metal-affinity chromatography. To evaluate its safety and immunogenicity the recombinant protein was purified for the immunization of human volunteers. The OprF/OprI hybrid protein is considered to be a candidate for a vaccine against P. aeruginosa.

Safety and immunogenicity of a Pseudomonas aeruginosa hybrid outer membrane protein F-I vaccine in human volunteers

A hybrid protein [Met-Ala-(His)6OprF190-342-OprI21-83] consisting of the mature outer membrane protein I (OprI) and amino acids 190 to 342 of OprF of Pseudomonas aeruginosa was expressed in Escherichia coli and purified by Ni2+ chelate-affinity chromatography. After safety and pyrogenicity evaluations in animals, four groups of eight adult human volunteers were vaccinated intramuscularly three times at 4-week intervals and revaccinated 6 months later with either 500, 100, 50, or 20 microg of OprF-OprI adsorbed onto A1(OH)3. All vaccinations were well tolerated. After the first vaccination, a significant rise of antibody titers against P. aeruginosa OprF and OprI was measured in volunteers receiving the 100- or the 500-microg dose. After the second vaccination, significant antibody titers were measured for all groups. Elevated antibody titers against OprF and OprI could still be measured 6 months after the third vaccination. The capacity of the elicited antibodies to promote complement binding and opsonization could be demonstrated by a C1q-binding assay and by the in vitro opsonophagocytic uptake of P. aeruginosa bacteria. These data support the continued development of an OprF-OprI vaccine for use in humans.

Mutations in a peptidylprolyl-cis/trans-isomerase gene lead to a defect in 3'-end formation of a pre-mRNA in Saccharomyces cerevisiae

In a genetic screen aimed at the identification of trans-acting factors involved in mRNA 3'-end processing of budding yeast, we have previously isolated two temperature-sensitive mutants with an apparent defect in the 3'-end formation of a plasmid-derived pre-mRNA. Surprisingly, both mutants were rescued by the essential gene ESS1/PTF1 that encoded a putative peptidylprolyl-cis/trans-isomerase (PPIase) (Hani, J., Stumpf, G., and Domdey, H. (1995) FEBS Lett. 365, 198-202). Such enzymes, which catalyze the cis/trans-interconversion of peptide bonds N-terminal of prolines, are suggested to play a role in protein folding or trafficking. Here we report that Ptf1p shows PPIase activity in vitro, displaying an unusual substrate specificity for peptides with phosphorylated serine and threonine residues preceding proline. Both mutations were found to result in amino acid substitutions of highly conserved residues within the PPIase domain, causing a marked decrease in PPIase activity of the mutant enzymes. Our results are suggestive of a so far unknown involvement of a PPIase in mRNA 3'-end formation in Saccharomyces cerevisiae.

A Salmonella typhimurium strain genetically engineered to secrete effectively a bioactive human interleukin (hIL)-6 via the Escherichia coli hemolysin secretion apparatus

Human interleukin-6 (hIL-6) cDNA was genetically fused with the Escherichia coli hemolysin secretorial signal (hlyA[S]) sequence in a plasmid vector. Recombinant E. coli XL-1 Blue and attenuated Salmonella typhimurium secreted a 30 kDa hIL-6-HlyA(S) fusion protein, with an additional form of higher apparent molecular mass produced by S. typhimurium. In S. typhimurium cultures hIL-6-HlyA(S) concentrations entered a plateau at 500 to 600 ng ml(-1) culture supernatant. In contrast to E. coli XL-1 Blue, in S. typhimurium culture supernatants hIL-6-HlyA(S) was accumulated faster reaching three-fold higher maximal concentrations. The cell proliferating activity of hIL-6-HlyA(S) fusion protein(s) was equivalent to that of mature recombinant hIL-6. Furthermore. hIL-6-secreting S. typhimurium were less invasive than the attenuated control strain. Therefore, the bulky hemolysin secretorial peptide at the C-terminus of the fusion protein does not markably affect hIL-6 activity, suggesting that the hemolysin secretion apparatus provides an excellent system to study immunomodulatory effects of in situ synthesized IL-6 in Salmonella vaccine strains.

The nucleotide sequence of Saccharomyces cerevisiae chromosome XIV and its evolutionary implications

In 1992 we started assembling an ordered library of cosmid clones from chromosome XIV of the yeast Saccharomyces cerevisiae. At that time, only 49 genes were known to be located on this chromosome and we estimated that 80% to 90% of its genes were yet to be discovered. In 1993, a team of 20 European laboratories began the systematic sequence analysis of chromosome XIV. The completed and intensively checked final sequence of 784,328 base pairs was released in April, 1996. Substantial parts had been published before or had previously been made available on request. The sequence contained 419 known or presumptive protein-coding genes, including two pseudogenes and three retrotransposons, 14 tRNA genes, and three small nuclear RNA genes. For 116 (30%) protein-coding sequences, one or more structural homologues were identified elsewhere in the yeast genome. Half of them belong to duplicated groups of 6-14 loosely linked genes, in most cases with conserved gene order and orientation (relaxed interchromosomal synteny). We have considered the possible evolutionary origins of this unexpected feature of yeast genome organization.

Expression of a non-MDR2-coded liver phosphatidylcholine membrane transport protein in Xenopus laevis oocytes

Phosphatidylcholines (PC) are secreted into the bile via a membrane transport protein(s). Recently, evidence for ATP-dependent mdr2-encoded PC transport as well as for carrier-mediated PC transport had been reported. Therefore, we investigated whether mdr2 P-glycoprotein is involved in the transport of a water-soluble short chain phosphatidylcholine analogue L-alpha-dibutyroyl-PC (diC4PC) induced by expression of liver mRNA in Xenopus laevis oocytes. Expression of mouse and rat mdr2 cRNA did not result in diC4PC net uptake in Xenopus laevis oocytes. By contrast oocytes showed a similar carrier-mediated uptake activity for diC4PC after injection of mouse, rat and human liver total mRNA (Km 7.7, 9.6, and 11.6 mM). Antisense inhibition of mdr2 mRNA expression increased diC4PC uptake induced by total liver mRNA from mouse and rat. The present data prove the existence of a specific mRNA for a non-mdr2-coded cell membrane PC carrier in mouse, rat, and human liver which exhibits similar transport affinity for diC4PC as the PC carrier in rat liver canalicular membranes.

The Pseudomonas aeruginosa outer membrane protein I vaccine: immunogenicity and safe administration in man

After expression in Escherichia coli and purification by Ni++ chelate-affinity chromatography, the outer membrane protein I (OprI) of Pseudomonas aeruginosa was tested in experimental animals for its safety and pyrogenicity. Four groups of 7 adult human volunteers were then vaccinated 3 times at four-weekly intervals with either 500 micrograms, 200 micrograms, 50 micrograms or 20 micrograms of OprI adsorbed onto aluminum hydroxide. The vaccinations were well tolerated and without systemic side effects, but a significant rise of antibody titers against OprI was measured in the serum of those who had received the 500 micrograms, 200 micrograms or 50 micrograms doses. Raised antibody titers against OprI were still present 30 weeks after the final vaccination. It was possible to demonstrate binding of the complement component C1q to the elicited antibodies, and this confirms their ability to promote antibody-mediated complement-dependent opsonization.

A hybrid outer membrane protein antigen for vaccination against Pseudomonas aeruginosa

Recently a hybrid protein containing parts of the outer membrane proteins OprF (aa 190-342) and OprI (aa 21-83) from Pseudomonas aeruginosa fused to the glutathione-S-transferase was shown to protect mice against a 975-fold 50% lethal dose of P. aeruginosa. To omit the use of the GST-protein, the hybrid protein OprF-OprI was expressed in E. coli using distinct modifications which have not to be eliminated after its expression. Using different signal peptides, the yield of the hybrid protein OprF-OprI in E. coli could be increased to 30% of the total cell protein, however, only a very small amount of the hybrid preprotein was processed and could be isolated from the periplasm of the host. A construct containing an N-terminal extension of 11 amino acids from the original OprF gene gave rise to a significantly higher expression in the cytoplasm. Purification was facilitated by the addition of a five histidine tag at the C-terminus. An even higher expression was obtained by a construct in which a six histidine tag was attached to the N-terminus of the hybrid protein. The N-terminal extended OprF-OprI as well as the N-terminal his-tagged OprF-OprI hybrid antigens were purified by immobilized-metal affinity chromatography under native and denaturing conditions and can now be tested for protectivity against P. aeruginosa in animal model systems.

Assignment of the human organic anion transporting polypeptide (OATP) gene to chromosome 12p12 by fluorescence in situ hybridization

BACKGROUND/AIMS

The organic anion transporting polypeptide (OATP) of human liver mediates the basolateral hepatocellular uptake of numerous cholephilic anions and steroidal compounds. The aim of this study was to clone the human OATP gene and to map its chromosomal localization by fluorescence in situ hybridization.

METHODS

A polymerase chain reaction-amplified fragment of the human OATP gene was used to isolate a genomic OATP clone from a P1-derived artificial chromosome human genomic library. Human metaphase chromosomes were hybridized with digoxigenin-labeled DNA from the genomic OATP clone and incubated in fluoresceinated antidigoxigenin antibodies for in situ detection of specific hybridization signals.

RESULTS

Sequence analysis revealed that the isolated P1-derived artificial chromosome clone contained a large portion of the human OATP gene. Fluorescence in situ hybridization of human chromosomes with the genomic OATP clone resulted in the specific labeling of the OATP gene on the short arm of chromosome 12 at band 12p12.

CONCLUSIONS

Mapping of a genomic OATP clone to chromosome 12p12 represents a first step towards the molecular characterization of the human OATP gene. While no liver disease has so far been associated with cytogenetic abnormalities of the short arm of chromosome 12, the genomic OATP sequence provides the basis for studies on gene structure and on the tissue-specific regulation of OATP gene expression.

Dependence of yeast pre-mRNA 3'-end processing on CFT1: a sequence homolog of the mammalian AAUAAA binding factor

3'-End formation of pre-mRNA in yeast and mammals follows a similar but distinct pathway. In Saccharomyces cerevisiae, the cleavage reaction can be reconstituted by two activities called cleavage factor I and II (CFI and CFII). A CFII component, designated CFT1 (cleavage factor two) was identified by its sequence similarity to the AAUAAA-binding subunit of the mammalian cleavage and polyadenylation specificity factor (CPSF), even though the AAUAAA signal sequence appears to play no role in yeast pre-mRNA 3' processing. Depletion of a yeast whole-cell extract with antibodies to CFT1 protein abolished cleavage and polyadenylation of pre-mRNAs. Addition of CFII restored cleavage activity, but not polyadenylation. Polyadenylation required the further addition of poly(A) polymerase and polyadenylation factor I, suggesting a close but not necessarily direct association of these two factors with the CFT1 protein.

Inverse splicing of a discontinuous pre-mRNA intron generates a circular exon in a HeLa cell nuclear extract

We have recently reported the first example of inverse splicing of a eukaryotic pre-mRNA intron using a whole cell extract from the yeast Saccharomyces cerevisiae. The concomitant circularization of the exon in the course of this splicing reaction gave rise to the hypothesis that the circular RNA species, which had been recently discovered in vivo in mammalian cells, were generated by inverse splicing. Here we report the formation of a circular exon in HeLa cell nuclear extracts by an inverse splicing reaction of the second intron of the human beta-globin gene from a pre-mRNA transcript in which the two intron halves flanked an artificially fused, single exon. Our data demonstrate that the mammalian pre-mRNA splicing system has indeed an intrinsic capability of aligning splice sites in reverse order and that this alignment can be followed by a complete splicing reaction, whereby the discontinuous intron sequences are removed. Thus we propose that circular exons in vivo arise as a result of an inverse splicing reaction following the pairing of a 5' splice site with an upstream 3' splice site and that the frequency of this event is influenced by the presence and strength of other, competing splice sites.

Safety and immunogenicity of a Pseudomonas aeruginosa outer membrane protein I vaccine in human volunteers

The outer membrane protein I (OprI) of Pseudomonas aeruginosa was expressed in Escherichia coli and purified by Ni2+ chelate-affinity chromatography. After safety and pyrogenicity evaluation in animals, four groups of seven adult human volunteers were vaccinated three times at four week intervals with either 500 micrograms, 200 micrograms, 50 micrograms or 20 micrograms of OprI adsorbed onto Al(OH)3. All vaccinations were well tolerated and no systemic side effects were detected. A significant rise of antibody titers against OprI could be measured in the serum of all volunteers who had received the 500 micrograms, 200 micrograms or 50 micrograms doses. Elevated antibody titers against OprI could still be measured 30 weeks after the final vaccination. Binding of the complement component C1q to the elicited antibodies could be demonstrated, showing the ability of the latter to promote antibody-mediated complement-dependent opsonization.

The ribosomal protein gene RPS3 is an essential single copy gene of the yeast Saccharomyces cerevisiae

The communication reports the cloning, sequencing, and analysis of the RPS3 gene from yeast, which codes for the ribosomal protein YS3. Sequence analyses of a 2.45 kb DNA fragment revealed an open reading frame with the potential to code for a 240 amino-acid long protein. The first 20 amino acids display a 90% identity to a 20 amino-acid long protein sequence of yeast ribosomal protein S3, that was obtained by protein sequencing of purified yeast ribosomal proteins. The promoter region of the RPS3 gene contains several upstream conserved sequence elements (UASrpg, T-rich region) that usually regulate transcription of ribosomal protein genes. Northern blot experiments demonstrate that this ORF is transcribed into an approximately 900 nt long mRNA. The major start site of transcription is located near position -20. The RPS3 gene is a single copy gene in yeast. Its disruption yields non viable haploid spores of Saccharomyces cerevisiae.

Cloning and characterization of the ALG3 gene of Saccharomyces cerevisiae

The Saccharomyces cerevisiae alg3-1 mutant is described as defective in the biosynthesis of dolichol-linked oligosaccharides (Huffaker and Robbins, Proc. Natl. Acad. Sci. USA, 80, 7466-7470, 1983). Man5GlcNAc2-PP-Dol accumulates in alg3 cells and Endo H resistant carbohydrates are transferred to protein by the oligosaccharyltransferase complex. In this study, we describe the cloning of the ALG3 locus by complementation of the temperature sensitive growth defect of the alg3 stt3 double mutant. The isolated ALG3 gene complements both the defect in the biosynthesis of lipid-linked oligosaccharides of the alg3-mutant and the under-glycosylation of secretory proteins. The inactivation of the nonessential ALG3 gene results in the accumulation of lipid-linked Man5GlcNac2 and protein-bound carbohydrates which are completely Endo H resistant. The ALG3 locus encodes a potential ER-transmembrane protein of 458 amino acids (53 kDa) with a C-terminal KKXX-retrieval sequence.

Complete nucleotide sequence of Saccharomyces cerevisiae chromosome X

The complete nucleotide sequence of Saccharomyces cerevisiae chromosome X (745 442 bp) reveals a total of 379 open reading frames (ORFs), the coding region covering approximately 75% of the entire sequence. One hundred and eighteen ORFs (31%) correspond to genes previously identified in S. cerevisiae. All other ORFs represent novel putative yeast genes, whose function will have to be determined experimentally. However, 57 of the latter subset (another 15% of the total) encode proteins that show significant analogy to proteins of known function from yeast or other organisms. The remaining ORFs, exhibiting no significant similarity to any known sequence, amount to 54% of the total. General features of chromosome X are also reported, with emphasis on the nucleotide frequency distribution in the environment of the ATG and stop codons, the possible coding capacity of at least some of the small ORFs (<100 codons) and the significance of 46 non-canonical or unpaired nucleotides in the stems of some of the 24 tRNA genes recognized on this chromosome.

Pre-mRNA topology is important for 3'-end formation in Saccharomyces cerevisiae and mammals

Various signal motifs that are required for efficient pre-mRNA 3'-end formation in the yeast Saccharomyces cerevisiae have been reported. None of these known signal sequences appears to be of the same general importance as is the mammalian AAUAAA motif. To establish the importance of yeast pre-mRNA termini in 3'-end formation, the ends of a pre-mRNA transcript synthesized in vitro were ligated before incubation in a yeast whole-cell extract. Such covalently closed circular RNAs were not cleaved at their poly(A) sites. Interestingly, pseudocircular RNAs with complementary 3'- and 5'-terminal sequences allowing the formation of panhandle structures were also resistant to cleavage. However, 3'-end processing was impeded neither by terminal hairpins at either or at both ends nor by RNA oligonucleotides complementary to either or both ends of a linear pre-mRNA. Intriguingly mammalian pseudocircular pre-mRNAs also were not cleaved at their poly(A) sites when incubated in a HeLa cell nuclear extract. These results provide evidence for the general importance of RNA topology in the formation of an active 3'-end processing complex in S. cerevisiae and higher eukaryotes. The possibility of a torus-shaped factor involved in 3'-end formation is discussed.

In vitro generation of a circular exon from a linear pre-mRNA transcript

Recent findings have firmly established the existence of circular exons in vivo. We were interested in the possible splicing mechanism by which these unusual mRNA molecules could be created in vitro, though no biological relevance has been attached to their existence as yet. In this report we demonstrate that a modified synthetic linear yeast ACT1 transcript whose sequence begins with the 3'-part of its original intron, is continued by 247 nt of exon sequence and terminates with the 5'-part of its intron will generate a circular exon when introduced to standard in vitro splicing reactions in whole cell splice extracts from Saccharomyces cerevisiae. The formation of a circular exon was found to be independent of specific circular or secondary structures of the pre-mRNA transcript. We hypothesize that circular exons which are found in vivo may be generated from pre-mRNAs which derive from rare events of transcription initiation within an intron.

Outer membrane proteins of Pseudomonas aeruginosa as vaccine candidates

We tested the ability of the recombinant outer membrane proteins of Pseudomonas aeruginosa to serve as a protective vaccine against this Gram-negative pathogen in the presence of two main pathophysiological events leading to P. aeruginosa sepsis: (i) systemic infection during immunosuppression; and (ii) bacterial translocation. A hybrid vaccine was cloned which combined the protective epitopes of outer membrane protein F (OprF) and outer membrane protein I (OprI). This vaccine proved to be highly protective against an intraperitoneal challenge with P. aeruginosa in immunosuppressed mice. Oral immunization of mice with recombinant OprI expressing Salmonella dublin, induced s-IgA antibodies in the gut mucosa against OprI. These provided protection against translocation of P. aeruginosa in an immunosuppressed mouse model. To test whether OprI is effective in man, recombinant OprI was purified and used for the immunization of human volunteers. Immunization was tolerated well, and no side effects were observed. Antibody titers against OprI were measured in 90% of the volunteers after immunization.

Sequence analysis of a 78.6 kb segment of the left end of Saccharomyces cerevisiae chromosome II

We report the sequence analysis of a 78,601 bp DNA segment on the left arm of chromosome II of Saccharomyces cerevisiae. This 78.6 kb segment spans the region from the start of a subtelomeric Y' element up to the ILS1 gene. It contains 49 open reading frames (ORFs) with more than 100 amino acids length including 14 internal and five overlapping ORFs. The gene density, excluding the internal ORFs, was calculated as one ORF per 2.2 kb. Eight ORFs (PKC1, TyA, TyB, ATP1, ROX3, RPL17a, PET112 and ILS1) correspond to previously characterized genes. ORF YBL0718 was identified as CDC27; YBL0706 as TEL1. Four other ORFs show strong similarities to already known genes. The gene product of YBL0838 is 60% identical to the ribosomal protein RPL32 from rat, mouse and man. YBL0701 encodes a protein with significant similarity to the initiation factor eIF2 associated p67 glycoprotein from rat. Eight ORFs were disrupted and the resulting yeast strains analysed with respect to their phenotype.

PTF1 encodes an essential protein in Saccharomyces cerevisiae, which shows strong homology with a new putative family of PPIases

Complementation of a temperature sensitive mutant of the yeast Saccharomyces cerevisiae resulted in the isolation of PTF1 (processing/termination factor 1), an essential gene encoding a putative 3'-end processing or transcription termination factor of pre-mRNAs. Ptf1p shows significant homology to a newly discovered family of PPIases. This family is characterized by its insensitivity to immunosuppressive drugs and the lack of homology with cyclophilins and FK-506 binding proteins [Rahfeld et al. (1994) FEBS Lett. 352, 180-184]. Should Ptf1p display PPIase activity, it would be the first characterized, eukaryotic member of this putative family, which is essential for growth.

Protection of immunocompromised mice against lethal infection with Pseudomonas aeruginosa by active or passive immunization with recombinant P. aeruginosa outer membrane protein F and outer membrane protein I fusion proteins

Recombinant outer membrane proteins (Oprs) of Pseudomonas aeruginosa were expressed in Escherichia coli as glutathione S-transferase (GST)-linked fusion proteins. GST-linked Oprs F and I (GST-OprF190-350 [GST linked to OprF spanning amino acids 190 to 350] and GST-OprI21-83, respectively) and recombinant hybrid Oprs (GST-OprF190-342-OprI21-83 and GST-OprI21-83-OprF190-350) were isolated and tested for their efficacy as vaccines in immunodeficient mice. GST-OprF-OprI protected the mice against a 975-fold 50% lethal dose of P. aeruginosa. Expression of GST-unfused OprF-OprI failed in E. coli, although this hybrid protein has been expressed without a fusion part in Saccharomyces cerevisiae and used for immunizing rabbits. The immune rabbit sera protected severe combined deficient (SCID) mice against a 1,000-fold 50% lethal dose of P. aeruginosa. Evidence is provided to show that the most C-terminal part of OprF (i.e., amino acids 332 to 350) carries an important protective epitope. Opr-based hybrid proteins may have implications for a clinical vaccine against P. aeruginosa.

Splicing of a circular yeast pre-mRNA in vitro

We have tested the fate of a circularized synthetic pre-mRNA transcript in a whole cell splicing extract of Saccharomyces cerevisiae. Our results demonstrate that this circular precursor RNA is able to induce spliceosome formation in vitro and that the products of the following splicing reaction are the lariat-shaped intron, and a mature circular mRNA. Thus, it would appear that free 5' and/or 3' ends are not obligatory for a splicing reaction to occur, although we find its efficiency to be strongly influenced by the presence or lack of free ends. To our knowledge, this is the first demonstration that a circular pre-mRNA molecule is recognized as a suitable substrate by an eukaryotic mRNA splicing apparatus.

TH1 cells trigger tumor necrosis factor alpha-mediated hypersensitivity to Pseudomonas aeruginosa after adoptive transfer into SCID mice

Recent experiments have shown that gamma interferon (IFN-gamma), either administered or induced in vivo, e.g., by certain bacteria, is a key mediator in inducing hypersensitivity to bacterial lipopolysaccharides. The source of endogenous IFN-gamma in this context (natural killer versus TH1 cells) has not been investigated yet. In order to investigate the role of antigen-specific, IFN-gamma-producing TH1 cells in murine Pseudomonas aeruginosa infection, a murine TH1 cell line was propagated in vitro by using recombinant P. aeruginosa outer membrane protein I. Adoptive transfer experiments were performed by intravenous injection of various amounts of TH1 cells into P. aeruginosa-challenged SCID mice. Adoptive transfer of 5 x 10(6) T cells into SCID mice followed by an intraperitoneal challenge with 1.4 x 10(6) CFU of live P. aeruginosa resulted in the rapid death of the animals within 12 h postchallenge, whereas transfer of lower T-cell doses and saline as a control did not cause any detrimental effects. After challenge with 2.8 x 10(6) CFU of P. aeruginosa, similar results were obtained 18 h postchallenge; however, at the end of the 72-h observation period, no significant differences in survival rates were obtained between the groups treated with different amounts of T cells. The rapid death of mice treated with 5 x 10(6) T cells was reflected by 860-fold-elevated levels of tumor necrosis factor alpha (TNF-alpha) present in serum 2 h postchallenge, whereas no significant differences in TNF-alpha serum levels were detectable in mice treated with lower doses of T cells or with saline. Pretreatment of T-cell-reconstituted SCID mice with neutralizing anti-IFN-gamma monoclonal antibodies completely protected mice from bacterial challenge and reduced TNF-alpha levels in serum. We conclude that under the experimental conditions described here, IFN-gamma- and interleukin-2-producing TH1 cells represent an important trigger mechanism inducing TNF-alpha-mediated hypersensitivity to bacterial endotoxin.

Complete DNA sequence of yeast chromosome II

In the framework of the EU genome-sequencing programmes, the complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome II (807 188 bp) has been determined. At present, this is the largest eukaryotic chromosome entirely sequenced. A total of 410 open reading frames (ORFs) were identified, covering 72% of the sequence. Similarity searches revealed that 124 ORFs (30%) correspond to genes of known function, 51 ORFs (12.5%) appear to be homologues of genes whose functions are known, 52 others (12.5%) have homologues the functions of which are not well defined and another 33 of the novel putative genes (8%) exhibit a degree of similarity which is insufficient to confidently assign function. Of the genes on chromosome II, 37-45% are thus of unpredicted function. Among the novel putative genes, we found several that are related to genes that perform differentiated functions in multicellular organisms of are involved in malignancy. In addition to a compact arrangement of potential protein coding sequences, the analysis of this chromosome confirmed general chromosome patterns but also revealed particular novel features of chromosomal organization. Alternating regional variations in average base composition correlate with variations in local gene density along chromosome II, as observed in chromosomes XI and III. We propose that functional ARS elements are preferably located in the AT-rich regions that have a spacing of approximately 110 kb. Similarly, the 13 tRNA genes and the three Ty elements of chromosome II are found in AT-rich regions. In chromosome II, the distribution of coding sequences between the two strands is biased, with a ratio of 1.3:1. An interesting aspect regarding the evolution of the eukaryotic genome is the finding that chromosome II has a high degree of internal genetic redundancy, amounting to 16% of the coding capacity.

Outer membrane proteins of Pseudomonas aeruginosa as vaccine candidates

We tested the ability of recombinant outer membrane proteins of Pseudomonas aeruginosa to serve as a protective vaccine against this gram negative pathogen under two main pathophysiological events leading to P. aeruginosa sepsis. i) systemic infection during immunosuppression, and ii) bacterial translocation. A hybrid vaccine was cloned combining protective epitopes of outer membrane protein F (OprF) and outer membrane protein I (OprI). This vaccine proved to be highly protective against an intraperitoneal challenge with P. aeruginosa in immunosuppressed mice. Oral immunization of mice, with recombinant Salmonella dublin expressing OprI induced s-IgA antibodies in the gut mucosa against OprI and provided protection against translocation of P. aeruginosa in an immunosuppressed mouse model. To test whether OprI is safe for use in humans, recombinant OprI was purified and used for immunization of volunteers. Vaccination was well tolerated and no major side effects were observed. The induction of serum antibodies against OprI was found to be dose-dependent and was observed in total in 65% of the volunteers.

Protection of immunosuppressed mice against translocation of Pseudomonas aeruginosa from the gut by oral immunization with recombinant Pseudomonas aeruginosa outer membrane protein I expressing Salmonella dublin

AroA Salmonella dublin was used as recipient for a plasmid coding for the outer membrane protein I (OprI) of Pseudomonas aeruginosa. Oral immunization of Balb/c mice with recombinant S. dublin induced serum IgG and IgA antibodies against P. aeruginosa. In spleen and Peyer's patches anti-P. aeruginosa IgG- and IgA-secreting cells could be measured by the ELISPOT technique. In an oral challenge of immunosuppressed mice with P. aeruginosa the orally immunized animals had a 58-fold higher LD50 than control animals.

Flexibility and interchangeability of polyadenylation signals in Saccharomyces cerevisiae

Various signal motifs have been reported to be essential for proper mRNA 3'-end formation in the yeast Saccharomyces cerevisiae. However, none of these motifs has been shown to be sufficient to direct 3'-end processing and/or transcription termination. Therefore, several structural motifs have to act in concert for efficient 3'-end formation. In the region upstream of the three polyadenylation sites of the yeast gene for alcohol dehydrogenase I (ADH1), we have identified a hitherto unknown signal sequence contained within the octamer AAAAAAAA. This motif, located 11 nucleotides upstream of the first ADH1 polyadenylation site, is responsible for the utilization of this site in vitro and in vivo, since mutational alteration drastically reduced 3'-end formation at this position. Insertion of 38 ADH1-derived nucleotides encompassing the (A)8 motif into the 3'-end formation-deficient cyc1-512 deletion mutant restored full processing capacity in vitro. Insertion of the octamer alone did not restore 3'-end formation, although mutation of the (A)8 motif in the functional construct had abolished 3'-end processing activity almost completely. This demonstrates that the sequence AAAAAAAA is a necessary, although not sufficient, signal for efficient mRNA 3'-end formation in S. cerevisiae.

Complete DNA sequence of yeast chromosome XI

The complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome XI has been determined. In addition to a compact arrangement of potential protein coding sequences, the 666,448-base-pair sequence has revealed general chromosome patterns; in particular, alternating regional variations in average base composition correlate with variations in local gene density along the chromosome. Significant discrepancies with the previously published genetic map demonstrate the need for using independent physical mapping criteria.

The beta-tubulin genes of Drosophila auraria are arranged in a cluster

When the beta 1-, beta 2- and beta 3-tubulin-specific DNAs from Drosophila melanogaster were used as probes to recognize tubulin-specific sequences in the chromosomes of Drosophila auraria, they were found to hybridize to the same polytene band in region 32C of the 2L polytene chromosome. Three overlapping clones were isolated from a lambda EMBL3 genomic library of D. auraria, and they all contain beta-tubulin-specific sequences based on hybridization and partial-sequencing experiments of subcloned fragments. These clones hybridize in situ to the same polytene chromosome band in region 32C and they represent an approximately 35-kb fragment of genomic DNA.

Identification of pre-mRNA polyadenylation sites in Saccharomyces cerevisiae

In contrast to higher eukaryotes, little is known about the nature of the sequences which direct 3'-end formation of pre-mRNAs in the yeast Saccharomyces cerevisiae. The hexanucleotide AAUAAA, which is highly conserved and crucial in mammals, does not seem to have any functional importance for 3'-end formation in yeast cells. Instead, other elements have been proposed to serve as signal sequences. We performed a detailed investigation of the yeast ACT1, ADH1, CYC1, and YPT1 cDNAs, which showed that the polyadenylation sites used in vivo can be scattered over a region spanning up to 200 nucleotides. It therefore seems very unlikely that a single signal sequence is responsible for the selection of all these polyadenylation sites. Our study also showed that in the large majority of mRNAs, polyadenylation starts directly before or after an adenosine residue and that 3'-end formation of ADH1 transcripts occurs preferentially at the sequence PyAAA. Site-directed mutagenesis of these sites in the ADH1 gene suggested that this PyAAA sequence is essential for polyadenylation site selection both in vitro and in vivo. Furthermore, the 3'-terminal regions of the yeast genes investigated here are characterized by their capacity to act as signals for 3'-end formation in vivo in either orientation.

Antibody Production in Silkworm Cells and Silkworm Larvae Infected with a Dual Recombinant Bombyx Mori Nuclear Polyhedrosis Virus

We have examined the efficiency of coexpression of two heterologous genes from a recombinant Bombyx mori nuclear polyhedrosis virus for the production of antibodies in silkworm larvae. The cDNAs encoding the light and the heavy chains of a murine immunoglobulin, directed against lipoprotein I of Pseudomonas aeruginosa, were brought under the control of two separate copies of the viral polyhedrin promotor. Infection of silkworm cells with the recombinant baculovirus yielded a maximum of 6.4 micrograms/ml IgG2A in the culture supernatant 72 hours post infection, while 800 micrograms/ml IgG2A was found in the hemolymph of infected fifth instar silkworm larvae seven days after infection with the same construct. The recombinant antibody exhibited a similar antigen specificity and avidity to that of the monoclonal antibody derived from ascites fluid.

Automated sequencing and mapping of cosmid DNA with fluorescently-labeled dideoxynucleotide terminators

We have established a method for directly sequencing cosmid DNA on an automated DNA sequencer. The major advantage of this method is that only small amounts of cosmid template DNA are needed for the sequencing reactions.

Rapid sequencing of the Sendai virus 6.8 kb large (L) gene through primer walking with an automated DNA sequencer

The determination of the complete DNA sequence of the large (L) polymerase gene of Sendai virus strain Fushimi was used to explore the potential and feasibility of primer walking with fluorescent dye-labelled dideoxynucleotide terminators on an automated ABI DNA sequencer. The rapid identification of the complete sequence demonstrated that this approach is a time- and cost-saving alternative to classical sequencing techniques. Analysis of the data revealed that the L gene of Sendai virus strain Fushimi consists of exactly 6800 nucleotides and that the deduced amino acid sequence identifies a single open reading frame encoding a protein of 252.876 kDa. In contrast to Sendai virus strain Enders, the L mRNA of strain Fushimi is monocistronic. The comparison of the deduced amino acid sequences of the L genes of three different Sendai virus strains confirmed the existence of conserved as well as variable regions in the L protein and revealed a high grade of conservation in the carboxyterminal third. Furthermore, functional amino acid sequence motifs, like elements of RNA-dependent RNA polymerases and ATP-binding sites as postulated previously, were identified.

[Genome analysis--current status of knowledge and future perspectives]

The rapid recent progress in molecular biology has placed the complete analysis of the human genome near at hand. This analysis of the human genome is not only restricted to the mapping, i.e. the localization of the genes on the chromosomes, but also involves the complete sequence analysis of the human DNA. Combined with increasingly sophisticated techniques which demand less and less amounts of material, the high resolution genome maps and the availability of a growing set of human genes will also expand the spectrum of possible future applications. Like in other fields these new technological developments will generate problems of social, ethical and legal nature. Therefore it seems absolutely essential not only to advance further technical developments and methodological improvements, but also to integrate these developments within a broad open discussion about their intended and unintended consequences.

Evaluation of protective mAbs against Pseudomonas aeruginosa outer membrane protein I by C1q binding assay

Seven monoclonal antibodies (mAbs) against the outer membrane proteins (OPRs) F, H and I of Pseudomonas aeruginosa were prepared. Western blot analysis has shown the mAbs to cross-react with all 17 serotypes of P. aeruginosa according to the International Antigenic Typing Scheme. Two of the mAbs (2A1, 6A4) protected mice against fatal P. aeruginosa pneumonia. The protective potential of the mAbs did not correlate with the immunoglobulin isotype nor with the fine antigen specificity and the in vitro bactericidal activity of the mAbs. Only the binding of the first complement component C1q of the mAbs as estimated in vitro by an ELISA was significantly correlated with their protective potential.

Protection of immunosuppressed mice against infection with Pseudomonas aeruginosa by recombinant P. aeruginosa lipoprotein I and lipoprotein I-specific monoclonal antibodies

Outer membrane protein I (OprI) is one of the major proteins of the outer membrane of Pseudomonas aeruginosa. The protective effect of OprI vaccination and that of three OprI-specific monoclonal antibodies (MAbs) against infection with P. aeruginosa were tested in immunosuppressed mice. The combination of Oprl and MAb 2A1 protected the mice against a challenge with a 96-fold 50% lethal dose. The binding site of MAb 2A1 was mapped, resulting in the identification of a protective epitope (amino acids 7 to 20).

Protection against experimental Pseudomonas aeruginosa infection by recombinant P. aeruginosa lipoprotein I expressed in Escherichia coli

Lipoprotein I (OprI) is one of the major proteins of the outer membrane of Pseudomonas aeruginosa. OprI is a candidate for a vaccine against P. aeruginosa, because it cross-reacts antigenically in all serotype strains of the International Antigenic Typing Scheme. We recently cloned and expressed the gene coding for OprI in Escherichia coli. This heterologously expressed OprI was used successfully to immunize mice against P. aeruginosa. In addition, OprI from serogroup 12 of P. aeruginosa was highly purified by preparative isoelectric focusing and used for immunization of mice. Both vaccines protected the mice against a challenge with a four- to fivefold 50% lethal dose of P. aeruginosa.

Protection of immunosuppressed mice against infection with pseudomonas aeruginosa by monoclonal antibodies to outer membrane protein OprI

Two monoclonal antibodies (mAbs) designated 2A1 and 6A4 which had been shown to be directed against Pseudomonas aeruginosa outer membrane lipoprotein I were tested in cyclophosphamide treated mice for their protective ability against P. aeruginosa infection. Pretreatment of mice with either 2 mg of 2A1 or 4 mg of 6A4 in combination with lethally irradiated human leucocytes reduced the mortality after subsequent subcutaneous injection of 100 living P. aeruginosa organisms to 50% of the controls. Without leucocytes only mAb 2A1 (isotype IgG2b) showed protection (47%). Irradiated leucocytes alone without mAb did not protect the mice significantly from fatal P. aeruginosa infection.

Antibody Production in Baculovirus-Infected Insect Cells

We have employed the baculovirus expression system for the production of a mouse monoclonal IgG antibody directed against lipoprotein I of Pseudomonas aeruginosa. Both light and heavy chain cDNAs were introduced into the baculovirus genome in a single step of homologous recombination. Insect cells that were infected with the recombinant virus stably secreted antigen-binding and glycosylated antibody molecules capable of binding the complement component C1q.

A yeast tRNA precursor containing a pre-mRNA intron is spliced via the pre-mRNA splicing mechanism

We have replaced the 14 nucleotide long intervening sequence of the Saccharomyces cerevisiae SUP6 (ochre) tRNA(Tyr) gene by the 52 nucleotide long second intron of the S. cerevisiae MATa1 gene. Yeast cells containing this modified pre-tRNA showed the typical suppressor phenotype indicating that the MATa1 pre-mRNA intron was exactly excised in vivo from the primary tRNA transcript and a mature and functional tRNA was formed. Several lines of evidence show that the splicing reaction proceeded via the pre-mRNA splicing mechanism: the reaction yielded a lariat shaped excised intron with a lariat shaped intron-exon 2 molecule as intermediate; point mutations in the conserved UAC-UAAC box of the intron impaired splicing of the precursor RNA; in a temperature sensitive rna2 strain splicing of this tRNA precursor was inhibited at the restrictive temperature. Our results imply that in yeast the excision of a pre-mRNA intron is not dependent on the transcription apparatus by which it was generated and that transcription and splicing are uncoupled processes in vivo, too. Furthermore these data demonstrate that recognition of an RNA as a substrate for a pre-mRNA splicing reaction is, at least qualitatively, only intron dependent.

The intron of the yeast actin gene contains the promoter for an antisense RNA

Using Northern blot analysis we have detected an approximately 840 nucleotide-long RNA which is complementary to the 5' leader sequence and the first ten nucleotides of the coding sequence of the yeast actin (ACT1) messenger RNA. We have determined two transcription start sites for this actin antisense RNA (ASR1), both within the ACT1 intron, at about 80 and 90 nucleotides downstream from the 5' splice site. Analysis of a cDNA clone showed that this RNA species overlaps the entire trailer sequence and approximately 20 nucleotides of the coding sequence of the nearby yeast YPT1 gene.

Cloning, characterization and heterologous expression of the SmaI restriction-modification system

The genes coding for the class-II Serratia marcescens restriction-modification system have been cloned and expressed in E. coli. Recombinant clones, restricted incoming phage only poorly; the recombinant plasmids, however, became fully modified in vivo, i.e. completely resistant against digestion with R.SmaI. The determined nucleotide sequence of the cloned system revealed three open reading frames with lengths of 252 bp, 741 bp, and 876 bp. Through various deletion experiments and an insertion-mutation experiment the 876 bp open reading frame could be assigned to the SmaI DNA modification enzyme and the 741 bp open reading frame to the SmaI restriction endonuclease. Mapping of the transcription start sites of the genes revealed that the SmaI endonuclease is transcribed as polycistronic mRNA together with a 252 bp long preceding open reading frame of unknown function. No homology was found when comparing the amino acid sequence of M.SmaI with the published sequences of m5C-specific DNA modification methyltransferases. On the other hand, a stretch of 14 amino acids in the C-proximal region of M.SmaI shows a significant homology to the C-proximal amino acid sequences of the N6A-methyltransferases M.HinfI and M.DpnIIA and the N4C-methyltransferase M.PvuII.

Pseudomonas aeruginosa outer membrane lipoprotein I gene: molecular cloning, sequence, and expression in Escherichia coli

Lipoprotein I (OprI) is one of the major proteins of the outer membrane of Pseudomonas aeruginosa. Like porin protein F (OprF), it is a vaccine candidate because it antigenically cross-reacts with all serotype strains of the International Antigenic Typing Scheme. Since lipoprotein I was expressed in Escherichia coli under the control of its own promoter, we were able to isolate the gene by screening a lambda EMBL3 phage library with a mouse monoclonal antibody directed against lipoprotein I. The monocistronic OprI mRNA encodes a precursor protein of 83 amino acid residues including a signal peptide of 19 residues. The mature protein has a molecular weight of 6,950, not including bound glycerol and lipid. Although the amino acid sequences of protein I of P. aeruginosa and Braun's lipoprotein of E. coli differ considerably (only 30.1% identical amino acid residues), peptidoglycan in E. coli, are identical. Using lipoprotein I expressed in E. coli, it can now be tested whether this protein alone, without P. aeruginosa lipopolysaccharide contaminations, has a protective effect against P. aeruginosa infections.

Specific oligodeoxynucleotide probes obtained through RNA sequencing

By combining several established techniques we developed a method to test the specificity of mixed oligodeoxynucleotide hybridization probes and to provide the information for the design of long nondegenerate, and therefore more specific probes. Mixed oligodeoxynucleotide probes derived from known peptide sequences are first used to initiate primer extension reactions with poly(A)+RNA as template in the presence of three dNTPs and one ddNTP to generate cDNA transcripts of defined lengths. Comparing the lengths of the cDNA transcripts with the possible nucleic acid sequence coding for the known oligopeptide indicates whether the oligodeoxynucleotide mix hybridizes predominantly to the RNA of interest. In a second step, the oligodeoxynucleotide mix with the highest specificity is used for indirect RNA sequence analysis. This confirms the specificity of the probe and provides information to design a long, highly specific oligodeoxynucleotide probe for the gene of interest. This simple two-step-procedure helps to circumvent the time-consuming procedures of subcloning and sequencing of cross-hybridizing fragments.

Cloning and characterization of cDNAs coding for the heavy and light chains of a monoclonal antibody specific for Pseudomonas aeruginosa outer membrane protein I

A set of seven monoclonal antibodies (MAb) directed against outer membrane proteins of Pseudomonas aeruginosa has been examined by Western blot analysis, indirect immunofluorescence tests and subclass typing. The hybridoma cell line secreting MAb 6A4, which reacts with outer membrane protein I, belongs to the IgG2a subclass and crossreacts with the 17 P. aeruginosa serotypes as listed in the International Antigenic Typing System, was selected as source for the preparation of poly(A)+RNA which in turn was used as template for cDNA synthesis and cloning. Full length cDNA clones of the gamma heavy chain as well as the kappa light chain were obtained and characterized by nucleotide sequence analysis. The complete cDNA sequences coding for the heavy and light chains will be the prerequisite for the construction and heterologous expression of a chimeric human-mouse monoclonal antibody which might be used in therapy of P. aeruginosa infections.