Efficient processing of an antigenic sequence for presentation by MHC class I molecules depends on its neighboring residues in the protein

Processing of endogenously synthesized proteins generates short peptides that are presented by MHC class I molecules to CD8 T lymphocytes. Here it is documented that not only the sequence of the presented peptide but also the residues by which it is flanked in the protein determine the efficiency of processing and presentation. This became evident when a viral sequence of proven antigenicity was inserted at different positions into an unrelated carrier protein. Not different peptides, but different amounts of the antigenic insert itself were retrieved by isolation of naturally processed peptides from cells expressing the different chimeric proteins. Low yield of antigenic peptide from an unfavorable integration site could be overcome by flanking the insert with oligo-alanine to space it from disruptive neighboring sequences. Notably, the degree of protection against lethal virus disease related directly to the amount of naturally processed antigenic peptide

Toxin–antitoxin based transgene expression in mammalian cells

Long-term, recombinant gene expression in mammalian cells depends on the nature of the transgene integration site and its inherent properties to modulate transcription (epigenetic effects). Here we describe a method by which high transgene expression is achieved and stabilized in extensively proliferating cultures. The method is based on strict co-expression of the transgene with an antitoxin in cells that express the respective toxin. Since the strength of antitoxin expression correlates with an advantage for cell growth, the cells with strong antitoxin expression are enriched over time in cultures of heterogeneous cells. This principle was applied to CHO cell lines that conditionally express the toxin kid and that are transduced to co-express the antitoxin kis together with different transgenes of interest. Cultivation of pools of transfectants that express the toxin steadily increase their transgene expression within several weeks to reach a maximum that is up to 120-fold over the initial status. In contrast, average transgene expression drops in the absence of toxin expression. Together, we show that cells conditionally expressing kid can be employed to create overexpressing cells by a simple coupling of kis to the transgene of interest, without further manipulation and in absence of selectable drugs

Subversion of Cellular Autophagosomal Machinery by RNA Viruses

Infection of human cells with poliovirus induces the proliferation of double-membraned cytoplasmic vesicles whose surfaces are used as the sites of viral RNA replication and whose origin is unknown. Here, we show that several hallmarks of cellular autophagosomes can be identified in poliovirus-induced vesicles, including colocalization of LAMP1 and LC3, the human homolog of Saccharomyces cerevisiae Atg8p, and staining with the fluorophore monodansylcadaverine followed by fixation. Colocalization of LC3 and LAMP1 was observed early in the poliovirus replicative cycle, in cells infected with rhinoviruses 2 and 14, and in cells that express poliovirus proteins 2BC and 3A, known to be sufficient to induce double-membraned vesicles. Stimulation of autophagy increased poliovirus yield, and inhibition of the autophagosomal pathway by 3-methyladenine or by RNA interference against mRNAs that encode two different proteins known to be required for autophagy decreased poliovirus yield. We propose that, for poliovirus and rhinovirus, components of the cellular machinery of autophagosome formation are subverted to promote viral replication. Although autophagy can serve in the innate immune response to microorganisms, our findings are inconsistent with a role for the induced autophagosome-like structures in clearance of poliovirus. Instead, we argue that these double-membraned structures provide membranous supports for viral RNA replication complexes, possibly enabling the nonlytic release of cytoplasmic contents, including progeny virions, from infected cells

Recombination between Polioviruses and Co-Circulating Coxsackie A Viruses: Role in the Emergence of Pathogenic Vaccine-Derived Polioviruses

Ten outbreaks of poliomyelitis caused by pathogenic circulating vaccine-derived polioviruses (cVDPVs) have recently been reported in different regions of the world. Two of these outbreaks occurred in Madagascar. Most cVDPVs were recombinants of mutated poliovaccine strains and other unidentified enteroviruses of species C. We previously reported that a type 2 cVDPV isolated during an outbreak in Madagascar was co-circulating with coxsackieviruses A17 (CA17) and that sequences in the 3′ half of the cVDPV and CA17 genomes were related. The goal of this study was to investigate whether these CA17 isolates can act as recombination partners of poliovirus and subsequently to evaluate the major effects of recombination events on the phenotype of the recombinants. We first cloned the infectious cDNA of a Madagascar CA17 isolate. We then generated recombinant constructs combining the genetic material of this CA17 isolate with that of the type 2 vaccine strain and that of the type 2 cVDPV. Our results showed that poliovirus/CA17 recombinants are viable. The recombinant in which the 3′ half of the vaccine strain genome had been replaced by that of the CA17 genome yielded larger plaques and was less temperature sensitive than its parental strains. The virus in which the 3′ portion of the cVDPV genome was replaced by the 3′ half of the CA17 genome was almost as neurovirulent as the cVDPV in transgenic mice expressing the poliovirus cellular receptor gene. The co-circulation in children and genetic recombination of viruses, differing in their pathogenicity for humans and in certain other biological properties such as receptor usage, can lead to the generation of pathogenic recombinants, thus constituting an interesting model of viral evolution and emergence

Genetic Management of Virus Diseases in Peanut

Peanut, also known as groundnut (Arachis hypogaea L.) is a major oilseed crop in the world. About 31 viruses representing 14 genera are reported to naturally infe.ct peanut in different parts of the world, although only a few of these are of economic importance. These include groundnutrosette disease in Africa, tomato spotted wilt-disease in the United States, peanut bud necrosis disease in south Asia, and peanut stripe virus disease in east and southeast Asia. Cucumber mosaic virus disease in China and Argentina and peanut stem necrosis disease in certain -pockets in southern India are also economically important. Host plant resistance provides the most effective and economic option to manage virus diseases. However, for many virus diseases, effective resistance gene(s) in cultivated peanut have not been identified. With a few exceptions, the virus resistance breeding work has received little attention in peanut improvement programs. Transgenic resistance offers another option in virus resistance breeding. This review focuses on the status of genetic resistance to various economically important groundnut viruses and'use of transgenic-technology for the improvement of virus resistance

Analyse des étapes précoces de l'infection de cellules in vitro par le poliovirus (PV) (transcytose du PV à travers les entérocytes et caractérisation des particules 147S produites en amont de la décapsidation par un mutant du PV responsable d'infections persistantes)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Effet antiviral de siRNA dans des modèles d'infections lytiques et persistantes par des virus à RNA positif

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Infection persistante de cellules intestinales humaines par le poliovirus, guérison et résistance cellulaire à la lyse (étude des mécanismes)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF