Replication-defective adenovirus infection reduces Helicobacter felis colonization in the mouse in a gamma interferon- and interleukin-12-dependent manner.
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Helicobacter infection leads to chronic inflammation of the stomach. Although the infection persists in spite of an immune response, animal studies have shown that adjuvant-based oral vaccines can protect against infection and even eliminate established infection. These vaccines are thought to induce a Th2 immune response, counterbalancing the Th1 response seen with natural infections. As a prelude to using adenovirus vectors carrying cytokine genes to modulate the immune response to established Helicobacter felis infection, we first examined the effect of the replication-defective adenovirus (RDA) vector itself. C57BL/6 mice chronically infected with H. felis (8 to 10 weeks) received intramuscular injections of RDA. The effect of RDA on the severity of H. felis colonization and the degree of gastric inflammation was assessed 2 weeks later. RDA caused a significant decrease in H. felis colonization without significantly altering the associated inflammation. RDA did not alter the H. felis-specific immunoglobulin G1 (IgG1), IgG2a, and IgA responses in the serum but was associated with an increase in gamma interferon (IFN-gamma)-producing CD8(+) spleen cells. To determine if IFN-gamma or Th1 cytokines were involved in the response to RDA, we examined RDA treatment of H. felis infection in mice lacking either IFN-gamma or interleukin-12 (IL-12). RDA failed to alter H. felis colonization in either of these two mouse strains. Thus, viral infection of mice chronically infected with H. felis led to a significant decrease in H. felis colonization in an IFN-gamma- and IL-12-dependent manner. These results demonstrate that Th1 responses associated with systemic viral infection can influence an established H. felis infection. (+info)
Induction of apoptosis by adenovirus E4orf4 protein is specific to transformed cells and requires an interaction with protein phosphatase 2A.
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We previously have shown that adenovirus type 5 E4orf4 protein associates with protein phosphatase 2A (PP2A) and induces apoptosis in transformed cells in a p53-independent manner. Here we show that the interaction between E4orf4 and PP2A is required for induction of apoptosis by the viral protein. This conclusion is supported by a mutation analysis of E4orf4 protein, showing a correlation between the ability to bind PP2A and to induce apoptosis, and by the observation that transfection of an antisense construct of the PP2A-B55 subunit reduces expression of the PP2A-B55 subunit and inhibits induction of apoptosis by E4orf4, but not by p53. The mutant analysis also indicates that even a low level of interaction with PP2A is sufficient to initiate the E4orf4 apoptotic pathway. In addition, E4orf4 inhibits cellular transformation by various oncogenes, and this function is coupled to its ability to induce apoptosis. Furthermore, expression of oncogenes in primary cell cultures sensitizes these cells to induction of apoptosis by E4orf4. Our results suggest that E4orf4 is a potentially useful tool for cancer gene therapy. (+info)
Role of the type 5 adenovirus gene encoding the early region 1B 55-kDa protein in pulmonary pathogenesis.
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Comparison of the inflammatory response of Sigmodon hispidus cotton rats to pulmonary infection with wild-type 5 adenovirus (Ad5) or with a viral mutant, in which the early region 1B gene encoding a 55-kDa protein, Ad5dl110 (dl110), was deleted, indicated that the inflammation in animals infected with dl110 was markedly reduced compared with the inflammation in animals infected with wild-type Ad5, although both viruses replicated to the same extent. Comparable experiments done with C57BL/6 mice yielded identical results, even though only the early phase of gene expression essential for viral replication occurs in mice. Cytokine analysis of infected mouse lungs indicated that tumor necrosis factor-alpha and IL-6 were produced in relatively large quantities in wild-type Ad5-infected mice and at significantly lower levels in dl110-infected mice during the early stages of infection. (+info)
Role of alpha(v) integrins in adenovirus cell entry and gene delivery.
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Adenoviruses (Ad) are a significant cause of acute infections in humans; however, replication-defective forms of this virus are currently under investigation for human gene therapy. Approximately 20 to 25% of all the gene therapy trials (phases I to III) conducted over the past 10 years involve the use of Ad gene delivery for treatment inherited or acquired diseases. At present, the most promising applications involve the use of Ad vectors to irradicate certain nonmetastatic tumors and to promote angiogenesis in order to alleviate cardiovascular disease. While specific problems of using Ad vectors remain to be overcome (as is true for almost all viral and nonviral delivery methods), a distinct advantage of Ad is the extensive knowledge of its macromolecular structure, genome organization, sequence, and mode of replication. Moreover, significant information has also been acquired on the interaction of Ad particles with distinct host cell receptors, events which strongly affect virus tropism. This review provides an overview of the structure and function of Ad attachment (coxsackievirus and Ad receptor [CAR]) and internalization (alpha(v) integrins) receptors and discusses their precise role in virus infection and gene delivery. Recent structure studies of integrin-Ad complexes by cryoelectron microscopy are also highlighted. Finally, unanswered questions arising from the current state of knowledge of Ad-receptor interactions are presented in the context of improving Ad vectors for future human gene therapy applications. (+info)
Cellular uptake and nuclear delivery of recombinant adenovirus penton base.
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An Ad2 capsid component, the penton base, expressed as recombinant protein, was found to be capable of affecting the entire entry pathway of adenovirion in HeLa cells, i.e., cell attachment, endocytosis, vesicular escape, intracytoplasmic movement, and translocation through the nuclear pore complex. Data with pentamerization-defective mutants suggested that none of these successive steps depended upon penton base pentamer status, indicating that the peptide domains responsible for these functions were carried by the monomer. Observations performed with wild-type (WT) and an integrin-binding-site double-mutant (K288E340) suggested that the penton base could enter the cell via an alternative, RGD- and LDV-independent, pathway. Of three mutants that were found to be defective in nuclear addressing in insect cells, only one, W165H, was also altered in nuclear transport in HeLa cells. The other two, W119H and RRR547EQQ, showed a WT pattern of nuclear localization in HeLa cells, suggesting that the region including tryptophan-119 and the basic signal at position 547 did not act as a nuclear localization signal in the human cell context. The integrity of cellular structures and the cytoskeleton seemed to be required for the vectorial movement and nuclear import of WT penton base, as suggested by experiments using permeabilized HeLa cells, isolated nuclear membranes, and cytoskeleton-targeted drugs. (+info)
Viral evolution revealed by bacteriophage PRD1 and human adenovirus coat protein structures.
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The unusual bacteriophage PRD1 features a membrane beneath its icosahedral protein coat. The crystal structure of the major coat protein, P3, at 1.85 A resolution reveals a molecule with three interlocking subunits, each with two eight-stranded viral jelly rolls normal to the viral capsid, and putative membrane-interacting regions. Surprisingly, the P3 molecule closely resembles hexon, the equivalent protein in human adenovirus. Both viruses also have similar overall architecture, with identical capsid lattices and attachment proteins at their vertices. Although these two dsDNA viruses infect hosts from very different kingdoms, their striking similarities, from major coat protein through capsid architecture, strongly suggest their evolutionary relationship. (+info)
Structure of the human adenovirus serotype 2 fiber head domain at 1.5 A resolution.
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Adenovirus binds to its receptor via the head domain of its fiber protein. We have crystallized the adenovirus serotype 2 (subgroup C) receptor binding domain and solved the structure at 1.5 A resolution by the molecular replacement technique using the known adenovirus type 5 head structure. Included in the high-resolution model are 306 water molecules, five alternative side chain conformations, and individual anisotropic temperature factors for each atom. The overall structure of the serotype 2 head is very similar to its serotype 5 homologue, apart from differences in some of the flexible loops. All but subgroup B adenoviruses are believed to use the recently identified protein CAR (Coxsackievirus and adenovirus receptor) as receptor. By comparison of the two structures and sequence alignment of CAR binding and non-CAR binding serotype fiber heads, we discuss possible receptor binding sites and propose a receptor binding site in a crevice between two monomers on the side of the trimer. The structural basis of the extraordinary stability of the fiber head trimer is also discussed. (+info)
Mutations in the DG loop of adenovirus type 5 fiber knob protein abolish high-affinity binding to its cellular receptor CAR.
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The amino acid residues in adenovirus type 5 (Ad5) fiber that interact with its cellular receptor, the coxsackie B virus and Ad receptor (CAR), have not been defined. To investigate this, multiple mutations were constructed in the region between residues 479 and 497 in Ad5 fiber (beta-strands E and F and the adjacent region of the DG loop). The effects of these mutations on binding to CAR were determined by use of cell-binding competition experiments, surface plasmon resonance, and direct binding studies. The mutation effects on the overall folding and secondary structure of the protein were assessed by circular dichroism (CD) spectroscopy. Deletions of two consecutive amino acids between residues 485 and 493 abolished high-affinity binding to CAR; the CD spectra indicated that although there was no disruption of the overall folding and secondary structure of the protein, local conformational changes did occur. Moreover, single site mutations in this region of residues with exposed, surface-accessible side chains, such as Thr492, Asn493, and Val495, had no effect on receptor binding, which demonstrates that these residues are not in contact with CAR themselves. This implies the involvement of residues in neighboring loop regions. Replacement of the segment containing the two very short beta-strands E and F and the turn between them (residues 479 to 486) with the corresponding sequence from Ad3 (betaEFAd3-->5 mutation) resulted in the loss of receptor binding. The identical CD spectra for betaEFAd3-->5 and wild-type proteins suggest that these substitutions caused no conformational rearrangement and that the loss of binding may thus be due to the substitution of one or more critical contact residues. These findings have implications for our understanding of the interaction of Ad5 fiber with CAR and for the construction of targeted recombinant Ad5 vectors for gene therapy purposes. (+info)