Lack of myristoylation of poliovirus capsid polypeptide VP0 prevents the formation of virions or results in the assembly of noninfectious virus particles

We previously described the generation of a set of mutations into a cDNA of poliovirus type 1 in the myristoylation signal of the capsid polypeptide VP4 (D. Marc, G. Drugeon, A.-L. Haenni, M. Girard, and S. van der Werf, EMBO J. 8:2661, 1989). Genomic transcripts synthesized in vitro from the mutated cDNAs were found to be noninfectious upon transfection of permissive cells, and this property correlated with the lack of VP0 myristoylation in vivo. In the study presented here, we analyzed the assembly intermediates that could be recovered from cells transfected with the mutated transcripts. We found that 14S pentamers could still assemble to a certain extent with an unmyristoylated VP0. Furthermore, viral particles sedimenting at 150S and containing capsid polypeptides VP1 to VP4 and virus-specific RNA were detected in the transfected cells. However, these mature virions were less abundant than those recovered after transfection with an infectious transcript, and they were devoid of infectivity. The results suggest that VP0 myristoylation plays a role in the late steps of poliovirus assembly and that the myristate moiety of VP4 may be required in the early steps of poliovirus infection.

Immunogenicity of the human immunodeficiency virus (HIV) recombinant nef gene product. Mapping of T-cell and B-cell epitopes in immunized chimpanzees

The nonstructural nef gene product of human immunodeficiency virus (HIV), p27, is a regulatory "early phase" protein produced by HIV-infected cells. As a possible negative regulator of transcription, it has been suggested that p27 may be involved in the control of HIV proviral latency. Immune reactivity to p27 may result in early destruction of HIV-replicating cells before viral assembly or of latently infected cells. It appeared, thus, of interest to investigate the immunogenicity of the molecule in chimpanzees immunized against HIV antigens. Two of the six chimpanzees that were injected with soluble recombinant p27 in association with other HIV proteins, displayed significant and sustained T-helper lymphocyte proliferative responses to p27 and to the other antigens. Using a set of synthetic peptides spanning the entire p27 sequence, two T-cell epitopes could be located: one within the last 20 amino-acids of the C terminus of the molecule, the other around the region of residues 118-122. Sera from the same animals also reacted to p27 in a radioimmunoassay as well as to some of the peptides in enzyme-linked immunosorbent assay. Sequential B-cell epitopes could thus be determined as being located in the regions of amino acids: 17-35, 52-66, and 185-205. The results obtained with peptides spanning the region between amino acid residues 65 and 172 indicate that at least two additional B-cell epitopes were present in the region comprised between amino acid 65 and 146. Interestingly, the extreme C terminus of the molecule encompasses both immunodominant T- and B-cell epitopes. Taken together, these observations should prove useful for the rational design of a HIV vaccine.

Thyroglossal duct cyst

Thyroglossal duct cyst is a midline congenital nonodontogenic cyst seen predominantly in children. The clinical history and physical examination, along with characteristic radiographic findings, enable the physician to make a preoperative diagnosis with a high degree of certainty. Surgery is the definitive treatment.

Critical role of neighbouring sequences on the immunogenicity of the C3 poliovirus neutralization epitope expressed at the surface of recombinant bacteria

The C3 neutralization epitope of poliovirus type 1 (PV-1) is a continuous epitope comprised within residues 93-103 of capsid protein VP1. These residues form a loop at the surface of the virus particle. The authors compared the immunogenicity of two peptides which contain this epitope, when presented at the surface of Escherichia coli by genetic insertion in the outer membrane protein LamB. One peptide was 13 residues long (VP1:93-103) and the other one contained flanking sequences increasing its size to 35 residues (VP1:86-115). Mice and rabbits were immunized with recombinant bacteria expressing the corresponding LamB-VP1 hybrid proteins. Antibodies against synthetic peptides, against native and heat denatured viral particles, as well as neutralizing antibodies were monitored. In this mode of presentation the shortest form of the epitope was more immunogenic. We provide evidence that the conformation of the epitope is different in the two hybrid LamB proteins and discuss possible consequences for immunogenicity.

The 15 amino acid residues preceding the amino terminus of the envelope protein in the yellow fever virus polyprotein precursor act as a signal peptide

The 15 amino acids which precede the sequence of the envelope (E) protein in the yellow fever virus (YFV) polyprotein precursor have been proposed to function as a signal peptide for the E protein (P. Desprès A. Cahour, C. Wychowski, M. Girard and M. Bouloy; Ann. Inst. Pasteur/Virol., 139, 59-67, 1988). To confirm this hypothesis, recombinant SV40 genomes were constructed in which the sequence of the E protein, or that of the poliovirus VP0 capsid polypeptide were placed immediately downstream of and in frame with the sequence of the putative signal peptide, under the control of the late SV40 promoter. The E protein expressed by the hybrid virus SV-E was recognized by two neutralizing monoclonal antibodies directed against the YFV envelope protein. In this construct, the E protein was deleted of its C-terminal transmembrane zone. Therefore, as expected, the protein appeared to be efficiently transported along the exocytic pathway and excreted into the cell culture medium. In addition, when the putative signal peptide was fused in frame with poliovirus polypeptide VP0, the expressed chimeric polypeptide was targeted to the endoplasmic reticulum where it underwent glycosylation.

Prevalence of hepatitis B virus infection in the Austral archipelago, French Polynesia: identification of transmission patterns for the formulation of immunization strategies

A sero-epidemiological survey of hepatitis B virus (HBV) infection in a randomly selected sample of 957 persons from the population of the Austral Island group in French Polynesia was conducted as a first step before developing an immunization programme strategy. Prevalence rates of HBsAg ranged from 3.09% to 27% in the different islands of the group with a weighted mean of 10.48%, while the prevalence rate for at least one marker ranged from 46.91% to 81.03% with a weighted mean of 64.12%. In the 0-11 months and 1-4 years age groups, 2.08% and 10.57%, respectively, of the children were HBsAg carriers. These findings, when compared to the mean population carrier rate of 10.48%, suggest that HBV transmission occurred mostly after the first year of life. The highest prevalence rate for HBeAg positivity was in the 5-19 years age group (more than 40% of the HBsAg carriers were HBeAg positive), suggesting that contagiousness was greatest in childhood and adolescence. HBsAg was found in 11.45% of women of child-bearing age and HBeAg in 19.09% of women positive for HBsAg. It is concluded that immunization of newborns and infants, using vaccine alone, should be the most effective strategy for reducing HBV infection in the Austral Islands archipelago.

Characterization of the 5' and 3' ends of viral messenger RNAs isolated from BHK21 cells infected with Germiston virus (Bunyavirus)

The 3' ends of the S and M messenger RNAs isolated from BHK21 cells infected with Germiston virus were analyzed by mapping with RNase T2 or nuclease S1. The transcription termination signal was found to be located approximately 115 and 80 nucleotides upstream from the 3' end of the S and M genomic RNA templates, respectively. Both mRNAs were found to possess several adenosine residues at their 3' ends, but were not polyadenylated. They have acquired at their 5' end a heterologous 12- to 18-nucleotide-long sequence, which is not coded for by the virus. Sequencing of the 5' terminal region from single molecules cloned into pBR327 revealed that these primers are rich in C and G residues and possess a U or a C adjacent to the viral sequence.

Processing of yellow fever virus polyprotein: role of cellular proteases in maturation of the structural proteins

The yellow fever virus (YFV) cDNA segment coding for the part of the precursor polyprotein generating the structural proteins C (capsid), prM (precursor to the membrane protein M), and E (envelope) was expressed in vitro by using the T7 promoter-polymerase transcription system coupled to translation in rabbit reticulocyte lysates. A polypeptide of the expected molecular weight was observed to accumulate in the assay and was processed into proteins C, prM, and E only when dog pancreas microsomal membranes were added to the translation system. Proteins prM and E were translocated inside the endoplasmic reticulum, where prM underwent glycosylation. Regions essential for translocation of these proteins were localized to the 18- and 15-amino-acid C-terminal hydrophobic regions of proteins C and prM, respectively. Translocation of protein prM appeared to be less efficient than that of protein E. Maturation of these proteins followed different kinetics, indicating that the prM signal is probably cleaved off more slowly. A polypeptide composed of proteins C and prM, similar to the NVx polypeptide described in yellow fever virus-infected cells, was also produced in the in vitro system in the presence of membranes. No mature protein M was detected, suggesting that the cleavage of prM to M is a late processing event mediated by a protease different from endoplasmic reticulum signalases.

Role of myristoylation of poliovirus capsid protein VP4 as determined by site-directed mutagenesis of its N-terminal sequence

Mutations were introduced by oligonucleotide-directed mutagenesis into the cDNA of poliovirus type 1 (Mahoney) in the region coding for the first five amino acids (myristoylation signal) of the viral capsid protein precursor P1. The cDNAs were then transcribed in vitro and the properties of the transcripts carrying the mutations studied in vitro by translation in a reticulocyte lysate or in vivo upon transfection of primate cells. Mutation of amino acid residue number 5 (Ser5----Thr) did not affect the viral phenotype, whereas mutations of residues number 1 (Gly1----Arg), 2 (Ala2----Pro) or 5 (Ser5----Pro) prevented myristoylation of P1 and were lethal. However, delayed production of virus was occasionally observed as the result of reverse mutations, which were found to restore a functional myristoylation signal as well as a wild-type virus phenotype. Thus, the myristoylation signal of the poliovirus polyprotein can accommodate Ala, Ser, Thr or Leu residues at position 2 and Ser, Thr or Ala residues at position 5. Mutations that altered myristoylation of P1 and affected virus viability did not prevent replication of the viral RNA but severely impeded in vitro processing of P1. This suggests that myristoylation plays a role in poliovirus capsid protein assembly.

Reliability of data on haematotoxicity of antidepressants. A retrospective assessment of haematological monitoring in clinical studies on tricyclics

At the present time, there is some concern over the haematological adverse effects of antidepressants. The present paper examines retrospectively 314 clinical trials in depression which were published in English or French between 1958 and 1986 and which used at least one of the following tricyclics: amitriptyline, clomipramine, imipramine. Two decision tables assess the depth of detail with which haematological monitoring and safety were described by the authors of each study. The results indicate that more than 98% of the papers under scrutiny either provide no information on the subject or do so in a manner which is entirely subjective. Thus, it seems that current knowledge of haematotoxicity of antidepressants is almost entirely the result of spontaneous reports from doctors, with its well-known drawbacks.

Isolation of recombinant partial gag gene product p18 (HIV-1Bru) from Escherichia coli

The membrane-associated structural protein, p18, of the human immunodeficiency virus (HIV-1), has been expressed in Escherichia coli. The recombinant protein was purified by cation-exchange chromatography on S Sepharose followed by cation-exchange high-performance liquid chromatography (HPLC) on Sulfoethyl Aspartamide. The isolation of 28.7 mg of recombinant p18 from 16.71 of cell culture represents an overall yield of ca. 20%. Recombinant p18 was characterized by sodium dodecyl sulphate polyacrylamide gel electrophoresis, reversed-phase HPLC, amino acid composition and amino acid sequence analysis of the N-terminus. Edman degradation of peptides generated by trypsin or Staphylococcus aureus V8 proteolytic digestion, including the C-terminus, confirmed the amino acid sequence to be that predicted from the cDNA. A C-terminally cleaved form of recombinant p18, p18LM, was separated in the cation-exchange HPLC step and was partially characterized in parallel with the intact molecule. By Western blotting it was shown that recombinant p18 in addition to the cleaved form p18LM is recognized by a monoclonal antibody which was generated against the natural protein from HIV-1.

Preliminary characterization of cis interactions between mutations of poliovirus genome

The effects of three distinct point mutations in the P3 genomic region of poliovirus type 1 (Mahoney strain) have previously been analysed. A U to C change at position 5658, which modifies the proteinase 3C, is responsible for a small plaque phenotype and defective RNA replication. An A to G change at position 7256, which modifies the replicase 3D, is responsible for temperature sensitivity. A C to U change at position 7348, which is silent at the protein level, has no apparent phenotypic effect. These three mutations were introduced into a single poliovirus genome by recombinant cDNA techniques. The resulting plurimutant virus, vHA507, was temperature-sensitive and exhibited a small plaque phenotype. Both these characters were accentuated compared to those of the viruses in which the mutations were on separate genomes. Spontaneous ts+ revertants of vHA507 arose by true reversion of the replicase mutation. The small plaque phenotype and defective RNA replication were partially suppressed in the case of these revertants, despite the fact that the proteinase mutation was still present on their genomes. This suppression was assumed to be due to the presence of the silent mutation at position 7348. This system provides a simple model of cis interactions within the poliovirus genome.

The spore coat of a fucosylation mutant in Dictyostelium discoideum

Strain HL250 of Dictyostelium discoideum cannot convert GDP-mannose to GDP-fucose, resulting in an inability to fucosylate protein. This affects a group of proteins which are normally fucosylated intracellularly and then secreted via prespore vesicles to become part of the outer lamina of the spore coat. We have found that strain HL250 nevertheless accumulates typical amounts of these proteins, stores them normally in prespore vesicles, and secretes them normally to become a part of the spore coat. However, affected proteins are proteolyzed after germination, the spore coat is more accessible to penetration by a macromolecular probe, and germination is inefficient in older spores. These findings can be explained by a dependence of the integrity of the outer layer of the spore coat on protein-linked fucose.

[Information storage by the French blood banking community in 1988]

This report presents the results of a survey about computerization of the French Blood Bank Community. Questionnaires issued on the behalf of the French Automation Working Party (G.A.I.T.S.) were sent, then analysed during the second term of 1988. The answers allowed us to obtain a picture of the advance of computerization in the French Blood Transfusion Services.

Modulations of the in vitro translational efficiencies of Yellow Fever virus mRNAs: interactions between coding and noncoding regions

As an approach to define the structural features within the 5' noncoding region of Yellow Fever virus (YFV) that modulate mRNA translational efficiency, we have studied how minor changes in this region affect the translational capacity in vitro of the corresponding mRNAs. A cDNA sequence coding for part of the YFV structural proteins was inserted into the vector pGEM3 containing the bacteriophage T7 promoter. This vector was engineered by site-directed mutagenesis to permit in vitro synthesis of transcripts containing only 5 vector nucleotides at their 5' end. The sequence of the YFV 5' untranslated region was further modified in order to alter the secondary structure of resulting T7 transcripts. The efficiency of these messengers in programming cell-free translation systems varied from 1- to 15-fold, correlating inversely with the potential of the 5' untranslated sequences to form stable secondary structures. A chimaeric messenger containing the YFV 5' noncoding (5' NC) region linked to a heterologous mRNA derived from Germiston virus, was tested for its in vitro translatability. We found a translational efficiency about 2-fold higher than that obtained with homologous transcripts, suggesting that YFV 5' NC region can function as a potential enhancer for gene expression. Data obtained with a series of plasmids constructed by linking the native YFV 5'NC region to various coding regions of the YFV genome indicated that interactions between the untranslated sequence and protein coding regions influence mRNAs translational efficiency.

HIV-1 core proteins expressed from recombinant vaccinia viruses

The sequences encoding the core proteins p55, p25, and p18 of the human immunodeficiency virus (HIV-1) have been inserted into the vaccinia virus genome. Infection of cultured cells with the live recombinant viruses led to the expression of proteins that were recognized by sera from HIV-seropositive individuals. Immunization of mice with the recombinant virus expressing the HIV p25 protein and the p55 precursor yielded high levels of antibodies directed against the corresponding HIV antigens. The data obtained are discussed in terms of the possible use of these live recombinant viruses in the development of a strategy toward an AIDS vaccine.

A point mutation in the poliovirus polymerase gene determines a complementable temperature-sensitive defect of RNA replication

We have previously described the isolation of a RNA- temperature-sensitive (ts) mutant of poliovirus type 1, ts035, after chemical mutagenesis by 5-fluorouracil. The ts defect of ts035 correlated with defective RNA replication, since the two characters corevert in the case of spontaneous revertants. The alteration of a trans-acting replication function of ts035 was suggested by significant rescue following mixed infection with another ts mutant, ts221, or with wild-type virus. Protein synthesis appeared normal at 39 degrees (nonpermissive temperature) in shift-up experiments and no defect of RNA elongation was evidenced when the activity of replication complexes or purified polymerase was measured at 39 degrees. These results provide circumstantial evidence that the initiation of ts035 RNA synthesis at 39 degrees is impaired. Molecular cloning of the ts035 genome allowed us to construct a recombinant virus with the same ts phenotype as ts035, by the transfer of a fragment of the mutant polymerase gene into the wild-type genome. Two mutations were present in this region of the ts035 genome but the determination of nucleotide sequences in the case of ts035 revertants indicated that only the substitution from A to G at nucleotide 7256 was necessary for the ts phenotype. This mutation replaces Asn 426 by an Asp in polypeptide 3D, the viral polymerase.

Cell-mediated immune proliferative responses to HIV-1 of chimpanzees vaccinated with different vaccinia recombinant viruses

The only animal that can be reproducibly infected with HIV, and that thus provides an experimental system for testing the effectiveness of prototype vaccines, is the chimpanzee. We compared proliferative responses to HIV and to vaccinia virus (VV) antigens of lymphocytes taken at various times from chimpanzees vaccinated with recombinant VV expressing different HIV genes. Animals were immunized with the original VV strain, as control, or with constructs expressing gp160 (VV160) given exclusively or in combination with one or two other constructs producing p25 (VV25), F/3'-orf (VVF), or the human interleukin-2 (IL-2) gene, which was included in an attempt to amplify immune responses. Irrespective of the HIV gene utilized, lymphocyte proliferation to HIV was usually weak and rapidly decreased after each inoculation, contrasting with strong and sustained responses to VV. Lack of adequate recall reactivity after challenge with fixed autologous lymphocytes expressing VV-produced HIV antigens indicated that vaccination resulted only in low levels of HIV-specific memory cell priming. The use of IL-2-producing VV did not lead to increased responsiveness. Reactivity to soluble purified gp160, but not to p25, could be detected in PBL from animals that had received both VV160 and VV25, while immunization with VVF resulted in a significant response to this protein in one of two animals. The transient nature of T cell reactivity to HIV might explain why, in similar studies, chimpanzees were not protected from infection with live HIV.

Substitution in the poliovirus replicase gene determines actinomycin D sensitivity of viral replication at elevated temperature

A series of ts+ revertants and recombinants derived from a temperature-sensitive plurimutant of poliovirus type 1 showed identical plaquing efficiencies at 37 degrees C and at 39 degrees C and exhibited similar yields and plaque morphology to wild-type virus. However, these viruses were characterized by clear inhibition of viral RNA synthesis at 39 degrees C, as measured by uridine incorporation in the presence of actinomycin D. Similarly, virus yields were decreased by one log in the presence of actinomycin D during infection at 39 degrees C. All the ts+ recombinants formed between temperature-sensitive mutants of poliovirus that were inhibited by actinomycin D carried a glutamine----histidine modification at residue 170 of their viral replicase (polypeptide 3D), due to a G----U substitution at nucleotide 6496. Inhibition of viral growth was increased by pretreatment of cells with actinomycin D for 3 h prior to infection, suggesting that actinomycin D sensitivity could reflect an increased dependence of viral RNA replication on host factor(s).

Hepatitis B virus surface antigen (HBsAg) as carrier for synthetic peptides having an attached hydrophobic tail

B- and T-cell epitopes from three distinct regions of the hepatitis B virus (HBV) envelope (env) protein (preS1, preS2 and S) are involved in eliciting protective immunity. Since preS1 sequences inhibit the secretion of HBV env proteins from eukaryotic cells, it is difficult to prepare immunogens rich in preS1 sequences. This problem can be overcome by linking synthetic peptides from the preS1 region to particles containing both S and preS2 sequences. We describe here a novel approach for binding of synthetic peptides to exposed hydrophobic domains on HBV env proteins. Long chain fatty acids or mercaptans are covalently linked to synthetic peptides. Peptides with the attached hydrophobic tails interact strongly with HBV env proteins (S + preS2), whereby hybrid immunogens are generated. Such immunogens can be used in combination with alum, the only adjuvant approved for human use. The combination of the preS1 peptide [preS(12-47)] with particles containing the S and preS2 regions resulted in an immunogen which: (1) elicits a broad spectrum of protective antibodies; (2) circumvents the nonresponsiveness to: (a) preS1 epitopes in preS1-nonresponder strains of mice; and (b) S-protein in S-protein-nonresponder strains of mice; and (3) augments the immune response to S-protein. The combination of HBV env proteins with a synthetic peptide from the envelope of the human immunodeficiency virus (HIV-1) resulted in an immunogen eliciting anti-HIV-1. Hybrid immunogens consisting of viral proteins and of synthetic peptides represent a feasible approach for the design of future vaccines.