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PubMed2003

Generation of an adenoviral vector containing an addition of a heterologous ligand to the serotype 3 fiber knob.

As an initial assessment of the feasibility of employing the adenovirus serotype 3 (Ad3) fiber knob as a locale for introducing a tropism-modifying motif, we generated an adenoviral vector containing a six-histidine tag genetically fused to the carboxy-terminus of the Ad3 fiber knob. The heterologous tag proved to be accessible for binding in the context of the virion and, moreover, had rendered the modified vector capable of mediating gene transfer through an artificial, non-Ad3 receptor.

Adenoviridae↗
PubMed1998

Amino acids in the capsid protein of tomato yellow leaf curl virus that are crucial for systemic infection, particle formation, and insect transmission.

A functional capsid protein (CP) is essential for host plant infection and insect transmission in monopartite geminiviruses. We studied two defective genomic DNAs of tomato yellow leaf curl virus (TYLCV), Sic and SicRcv. Sic, cloned from a field-infected tomato, was not infectious, whereas SicRcv, which spontaneously originated from Sic, was infectious but not whitefly transmissible. A single amino acid change in the CP was found to be responsible for restoring infectivity. When the amino acid sequences of the CPs of Sic and SicRcv were compared with that of a closely related wild-type virus (TYLCV-Sar), differences were found in the following positions: 129 (P in Sic and SicRcv, Q in Sar), 134 (Q in Sic and Sar, H in SicRcv) and 152 (E in Sic and SicRcv, D in Sar). We constructed TYLCV-Sar variants containing the eight possible amino acid combinations in those three positions and tested them for infectivity and transmissibility. QQD, QQE, QHD, and QHE had a wild-type phenotype, whereas PHD and PHE were infectious but nontransmissible. PQD and PQE mutants were not infectious; however, they replicated and accumulated CP, but not virions, in Nicotiana benthamiana leaf discs. The Q129P replacement is a nonconservative change, which may drastically alter the secondary structure of the CP and affect its ability to form the capsid. The additional Q134H change, however, appeared to compensate for the structural modification. Sequence comparisons among whitefly-transmitted geminiviruses in terms of the CP region studied showed that combinations other than QQD are present in several cases, but never with a P129.

Amino Acid Sequence↗
PubMed2004

Adenovirus structure.

Structural studies continue to play an essential role as the focus of adenovirus research shifts in emphasis from basic biology to adenovirus-based vector technologies. A crucial step in developing novel therapeutics for gene replacement, cancer, and vaccines is often to modify the virion. Such engineered changes are designed to retarget the virus, or to reduce the immunological responses to infection. These efforts are far more effective when they are based on detailed structural knowledge. This minireview provides a brief summary of the wealth of information that has been obtained from the combined application of X-ray crystallography and electron microscopy. This knowledge now includes a good working model for the architectural organization of the virion, and atomic resolution molecular structures for all the major capsid proteins, hexon, penton, and fiber. We highlight new developments, which include the structure of the penton base and the discovery that adenovirus has several relatives. We sketch how the structural information can be used to engineer novel virions and conclude with the prospects for future progress.

Adenoviruses, Human↗
PubMed1991

[Genetic engineering production of H37Rv M. tuberculosis proteins].

A complete library of M. tuberculosis H37Rv genes was produced by incorporating the DNA fragments of M. tuberculosis H37Rv into the lambda pSI phasmid. For this, DNA isolated from the mycobacteria was treated by EcoRI restrictases and the fragments of 8-17 thousand nucleotide pairs were crosslinked with the phasmid DNA. Hybrid DNA molecules were packed into the caspids from the proteins of E. coli BHB2688 and BHB2690 strains. By estimates, this library contained 98% of M. tuberculosis H37Rv genome so that any required gene can be found at 0.99 probability. The needed genes were sought by monoclonal antibodies against a protein with a molecular mass of 17-19 kDa (IT-12, IT-51, IT-54) obtained from the WHO. The protein gene was also produced by the method for raising the end sequences using synthesis of two oligonucleotides SP30 complementary to segments that limit this gene in the presence of Taq-DNA-polymerase and DNA of M. tuberculosis H37Rv. Copies of a gene (MT-1) were produced by denaturation, firing and raising. This gene was incorporated in the puC119 plasmid and expressed in E. coli cells, the direction of reading being checked up. A protein with a molecular mass of 19 kDa was detected in E. coli extracts with the expressed pMT-2 plasmid using monoclonal antibodies IT-12 and IT-54 in enzyme-linked immunoassay and immunoblotting.

Antibodies, Monoclonal↗
PubMed2001

Engineering of alfalfa mosaic virus RNA 3 into an expression vector.

RNA 3 of alfalfa mosaic virus (AMV) encodes the 5'-proximal movement protein (MP) gene and the 3'-proximal coat protein (CP) gene which is expressed from a subgenomic RNA. Several strategies were explored to use this RNA as a vector for expression of the green fluorescent protein (GFP) in Nicotiana tabaccum plants expressing the viral polymerase proteins P1 and P2 (P12 plants). Insertion of a subgenomic promoter (sgp)-GFP cassette between the CP gene and the 3'-untranslated region (UTR) interfered with RNA accumulation in protoplasts, indicating that cis-acting sequences required for replication were disrupted. When GFP was fused to the N-terminus of MP or CP, the chimeric RNAs accumulated in protoplasts but cell-to-cell movement in plants was blocked. Insertion of a GFP-sgp cassette immediately upstream of the CP gene caused a hypersensitive host response. However, insertion of a GFP-sgp cassette upstream of the MP gene did not affect symptom formation and yielded a vector that expressed GFP in inoculated but not in the systemic leaves of both P12 tobacco and non-transgenic N. benthamina plants. When the size of the GFP gene was reduced from 700 to 300 nucleotides, virus infection was observed in the non-inoculated leaves. Analysis of the progeny of some chimera revealed novel data on replication, encapsidation and recombination of AMV RNA 3.

3' Untranslated Regions↗
PubMed2005

Production of an engineered killer peptide in Nicotiana benthamiana by using a potato virus X expression system.

The decapeptide killer peptide (KP) derived from the sequence of a single-chain, anti-idiotypic antibody acting as a functional internal image of a microbicidal, broad-spectrum yeast killer toxin (KT) was shown to exert a strong microbicidal activity against human pathogens. With the aim to exploit this peptide to confer resistance to plant pathogens, we assayed its antimicrobial activity against a broad spectrum of phytopathogenic bacteria and fungi. Synthetic KP exhibited antimicrobial activity in vitro towards Pseudomonas syringae, Erwinia carotovora, Botrytis cinerea, and Fusarium oxysporum. KP was also expressed in plants by using a Potato virus X (PVX)-derived vector as a fusion to the viral coat protein, yielding chimeric virus particles (CVPs) displaying the heterologous peptide. Purified CVPs showed enhanced antimicrobial activity against the above-mentioned plant pathogens and human pathogens such as Staphylococcus aureus and Candida albicans. Moreover, in vivo assays designed to challenge KP-expressing plants (as CVPs) with Pseudomonas syringae pv. tabaci showed enhanced resistance to bacterial attack. The results indicate that the PVX-based display system is a high-yield, rapid, and efficient method to produce and evaluate antimicrobial peptides in plants, representing a milestone for the large-scale production of high-added-value peptides through molecular farming. Moreover, KP is a promising molecule to be stably engineered in plants to confer broad-spectrum resistance to phytopathogens.

Anti-Bacterial Agents↗
PubMed2006

Transcutaneous vaccination with virus-like particles.

Virus-like particles (VLP) are inert, empty capsids of viruses, which contain no DNA/RNA from the virus itself. However they retain the structure of a virus and they can be engineered to have antigens attached. We have constructed VLP, derived from Rabbit hemorrhagic disease virus, and shown they are highly immunogenic. We tested the capacity of these engineered VLP to induce immune responses when they are administered to mice via the transcutaneous route. This route of vaccination is important, in order to generate mucosal protection. Our data showed that VLP are taken up by dendritic cells (DC), antigen-presenting cells that are essential to initiate acquired immune responses. The VLP induced an increase in expression of CD40, CD80 and CD86 but required an adjuvant, CpG DNA oligo-deoxy nucleotides (ODN) motifs, to enhance these responses. In vivo testing has also shown that the VLP, when wiped on to the skin in conjunction with immunostimulatory CpG, induce Ag-specific immune responses, typified by high levels of IFN-gamma and IgG1.

Administration, Cutaneous↗
PubMed1987

Pathogen-derived resistance to viral infection using a negative regulatory molecule.

The principle of pathogen-derived resistance (the use of pathogen-derived genes to interfere with the pathogenic process and thereby confer disease resistance to the host) has been put forward as a broadly applicable conceptual tool for use in the genetic engineering of resistance to pathogens and parasites. It was previously predicted that four mechanisms of pathogen-derived resistance could be established using the bacteriophage QB and its host, Escherichia coli, as a model system. This paper demonstrates and helps ellucidate the first of these mechanisms by using a viral regulatory protein, the QB coat protein, to block viral replication. The QB coat protein gene was transferred to susceptible E. coli. Expression of this gene had no obvious detrimental effect on the host. Low-level, constitutive expression of the coat protein conditions very high levels of resistance to QB infection. The resulting resistance is not associated with RNA interference or loss of pili as attachment sites, and does not appear to be associated with premature encapsidation. This low-level expression of the QB coat protein also produces an intermediate level of resistance to the closely related phage SP, but fails to protect against the unrelated phage f2. Thus the resistance does not result from a generalized antiviral host response induced by the presence of the coat protein. We conclude that the QB coat protein blocks viral infection, as was predicted, due to its action as a negative regulatory molecule. The use of negative regulatory molecules may provide an effective mechanism for use in the genetic engineering of pathogen-derived resistance.

Capsid↗
PubMed2005

Generation of HPV pseudovirions using transfection and their use in neutralization assays.

It has recently become possible to generate high-titer papillomavirus-based gene-transfer vectors. The vectors, also known as papillomavirus pseudoviruses (PsV), have been useful for studying papillomavirus assembly, entry, and neutralization, and may have future utility as laboratory gene-transfer tools or vaccine vehicles. This chapter outlines a simple method for production of PsV and their use in a high-throughput papillomavirus neutralization assay. The production method is based on transfection of a 293 cell line, 293TT, engineered to express high levels of SV40 large T antigen. The cells are co-transfected with codon-modified papillomavirus capsid genes, L1 and L2, together with a pseudogenome plasmid containing the SV40 origin of replication. Pseudogenome encapsidation within L1/L2 capsids is largely sequence independent, and plasmids entirely lacking PV sequences can be packaged efficiently, provided they are less than 8 kilobases in size. Non-infectious virus-like particles (VLPs) can also be produced after transfection of 293TT cells with L1 alone. Efficient purification of the PsV or VLPs is achieved by Optiprep (iodixanol) density gradient ultracentrifugation. Using these methods, it is possible to produce highly purified PsV with yields of at least 10(9) transducing units from a single 75-cm2 flask of cells. PsV encapsidating a secreted alkaline phosphatase (SEAP) reporter plasmid were used to develop a high-throughput in vitro neutralization assay in a 96-well plate format. Infection of 293TT cells is monitored by SEAP activity in the culture supernatant, using a highly sensitive chemiluminescent reporter system. Antibody-mediated PsV neutralization is detected by a reduction in SEAP activity. The neutralization assay has similar analytic sensitivity to, and higher specificity than, a standard VLP-based enzyme-linked immunosorbent assay (ELISA).

Cell Line↗
PubMed1993

Potential use of poliovirus as a vector.

The live attenuated Sabin strains of poliovirus have proven their efficacy at inducing a good humoral and secretory antibody response in humans. The extensive characterization of poliovirus neutralization antigenic sites and the atomic resolution of the three-dimensional structure of the viral capsid have enabled the use of the most stably attenuated poliovirus strain (the Sabin type 1 strain) as a vector for the presentation of short foreign antigenic domains in place of one of its own neutralization antigenic sites. The creation of such chimeras has been achieved by manipulating poliovirus infectious cDNA and transfecting the resulting chimeric cDNAs onto susceptible cell cultures. However, this epitope-presentation system has a limitation in terms of the sequence and size of the foreign domain that can be incorporated into the poliovirus capsid without disrupting virus viability. This has led to the construction of poliovirus hybrid genomes bearing insertions of longer heterologous sequences in place of part of the poliovirus structural genes. Upon transfection onto susceptible cells providing the poliovirus structural proteins in trans (e.g. cells previously infected with the Sabin 1 strain), stocks of encapsidated RNA replicons which expressed the foreign protein could be obtained. In addition, viable recombinant viruses bearing insertions of heterologous sequences at various places into the poliovirus genome without deleting poliovirus sequences have been reported. Potential applications of these chimeric and recombinant polioviruses in the engineering of new recombinant vaccines are discussed.

Animals↗
PubMedDate not supplied

[The use of filamentous phage M13 in protein engineering].

M13B1 vector based on the filamentous phage M13 has been constructed. M13B1 phage carries the gene of resistance to ampicillin and contains the unique site of recognition for BamHI restriction endonuclease in gene VIII coding for the major coat protein. BamHI restriction site has been inserted into the gene of the major coat protein by means of oligonucleotide directed mutagenesis. The synthetic DNA fragment coding for the model peptides has been inserted through BamHI site into the M13B1 DNA. The possibility of inserting foreign peptides into the N-terminus at maintaining the viability of hybrid phages has been shown. The differences in specificity of the recombinant phage maturation have been determined by analysing the amino acid sequence of B-protein.

Amino Acid Sequence↗
PubMed2002

A molecular assembly system that renders antigens of choice highly repetitive for induction of protective B cell responses.

Virus like particles (VLPs) are known to induce potent B cell responses in the absence of adjuvants. Moreover, epitope-specific antibody responses may be induced by VLPs that contain peptides inserted in their immunodominant regions. However, due to steric problems, the size of the peptides capable of being incorporated into VLPs while still permitting capsid assembly, is rather limited. While peptides genetically fused to either the N- or C-terminus of VLPs present fewer assembly problems, the immune responses obtained against such epitopes are often limited, most likely because the epitopes are not optimally exposed. In addition, such particles may be less stable in vivo. Here, we show that peptides and proteins engineered to contain a free cys can be chemically coupled to VLPs formed from the hepatitis B core antigen (HBcAg) containing a lys in the immuno-dominant region. By using this approach steric hindrance of capsid assembly is abrogated. Peptides or protein coupled to VLPs in an oriented fashion are shown to induce strong and protective B cell responses even against self-epitopes in the absence of adjuvants. This molecular assembly system may be used to induce strong B cell responses against most antigens.

Animals↗
PubMed2006

Expression of viral capsid protein antigen against Epstein-Barr virus in plastids of Nicotiana tabacum cv. SR1.

Epstein-Barr virus (EBV) infects nearly 90% of adults worldwide and is the pathogenic source of a broad spectrum of malignancies originating from lymphoid and epithelial cells. Currently, no vaccine has been developed to immunologically inactivate this virus. In infected patients, anti-EBV viral capsid antigen (VCA) immunoglobins represent some of the useful diagnostic markers for carcinoma development. To demonstrate that the EBV VCA antigen can be produced in plants, the plastid genome of tobacco (Nicotiana tabacum cv. SR1) was transformed with a VCA-expressing cassette. The EBV VCA mRNA was actively transcribed in the transplastomic plants and antigen production was detected. This study indicates that plastid transformation could be a promising strategy in EBV VCA antigen production.

Antigens↗
PubMed1998

A DNA clone encoding the full-length infectious genome of odontoglossum ringspot tobamovirus and mutagenesis of its coat protein gene.

A full-length DNA clone encoding the genome of odontoglossum ringspot tobamovirus (ORSV) was synthesized and placed adjacent to a bacteriophage T7 RNA polymerase promoter. Capped-RNA transcripts produced in vitro were highly infectious when mechanically inoculated onto seedlings of Nicotiana benthamiana and Oncidium Gower Ramsey. A representative clone, designated pOT2, caused a disease phenotype identical to that produced by parental viral RNA. ELISA, Western blot analysis, Northern blot hybridization and electron microscopy verified the infectivity of pOT2. A coat protein deficient mutant of the clone, pO delta CP1, was produced with the initiation codon of the coat protein cistron of ORSV abolished. Transcripts from pO delta CP1 were infective, able to move in N. benthamiana but produced no coat protein. This demonstrates that the coat protein was dispensable for RNA replication and for movement. This is believed to be the first report of an ORSV infectious clone driven by a T7 RNA polymerase promoter.

Blotting, Northern↗
PubMed1990

Crystallization of genetically engineered active maltose-binding proteins, including an immunogenic viral epitope insertion.

Three mutants of the maltose- or maltodextrin-binding protein encoded by the malE gene of Escherichia coli, with extensive genetic changes, have been purified and crystallized in different crystal forms. Two of these mutant proteins, MalE178 and MalE341, carry net deletions of seven and 13 residues, respectively, near the surface of the molecule. These mutations have very little effect on either the transport activity of the mutant strains or the sugar-binding activity of the purified mutant proteins. The third mutant protein involves the insertion of an 11-residue peptide of the C3 epitope from type 1 poliovirus VP1 protein into the MalE178 deletion mutant, with retention of essentially all the biological properties of the wild-type and the immunological properties of the C3 epitope. We are undertaking three-dimensional structure analysis in order to understand how the protein accommodates these large changes in its surface structure and how the C3 epitope retains its immunological properties in this new environment. The same system could be used to determine easily the structures of other peptide epitopes, especially those in proteins with unknown structures.

ATP-Binding Cassette Transporters↗
PubMed2003

Simultaneous CAR- and alpha V integrin-binding ablation fails to reduce Ad5 liver tropism.

Targeting adenovirus encoding therapeutic genes to specific cell types has become a major goal in gene therapy. Coxsackievirus and adenovirus receptor (CAR) and alpha(V) integrins have been identified as the primary cell surface components that interact with adenovirus type 5 (Ad5)-based vectors during in vitro transduction. Redirecting Ad5-based vectors requires abrogation of the natural interaction between the viral capsid and its cellular receptors and simultaneous introduction of a new binding specificity into the viral capsid. To abrogate native Ad5 tropism, fiber knob mutations Pro409Glu and Lys417Ala were each incorporated into adenoviral vectors, while the RGD motif was deleted from the penton base. In vitro transduction experiments showed that these capsid mutations eliminated Ad5 interactions with CAR and alpha(V) integrins. Moreover, incorporation in the fiber HI loop of a vitronectin-derived ligand (VN4) specific for the uPAR/CD87 receptor provided the Lys417Ala virus with an alternative entry pathway specific for uPAR-expressing cells, indicating a successful in vitro retargeting of the vector. Unexpectedly, however, simultaneous disruption of Ad5 binding to CAR and alpha(V) integrins had no effect on liver gene transfer following systemic administration in mice. This study highlights the need to understand better the molecular determinants involved in adenovirus uptake by the liver to control the fate of adenoviral vectors in vivo.

Adenoviridae↗
PubMed2005

A human adenoviral vector with a chimeric fiber from canine adenovirus type 1 results in novel expanded tropism for cancer gene therapy.

The development of novel therapeutic strategies is imperative for the treatment of advanced cancers like ovarian cancer and glioma, which are resistant to most traditional treatment modalities. In this regard, adenoviral (Ad) cancer gene therapy is a promising approach. However, the gene delivery efficiency of human serotype 5 recombinant adenoviruses (Ad5) in cancer gene therapy clinical trials to date has been limited, mainly due to the paucity of the primary Ad5 receptor, the coxsackie and adenovirus receptor (CAR), on human cancer cells. To circumvent CAR deficiency, Ad5 vectors have been retargeted by creating chimeric fibers possessing the knob domains of alternate human Ad serotypes. Recently, more radical modifications based on 'xenotype' knob switching with non-human adenovirus have been exploited. Herein, we present the characterization of a novel vector derived from a recombinant Ad5 vector containing the canine adenovirus serotype 1 (CAV-1) knob (Ad5Luc1-CK1), the tropism of which has not been previously described. We compared the function of this vector with our other chimeric viruses displaying the CAV-2 knob (Ad5Luc1-CK2) and Ad3 knob (Ad5/3Luc1). Our data demonstrate that the CAV-1 knob can alter Ad5 tropism through the use of a CAR-independent entry pathway distinct from that of both Ad5Luc1-CK2 and Ad5/3-Luc1. In fact, the gene transfer efficiency of this novel vector in ovarian cancer cell lines, and more importantly in patient ovarian cancer primary tissue slice samples, was superior relative to all other vectors applied in this study. Thus, CAV-1 knob xenotype gene transfer represents a viable means to achieve enhanced transduction of low-CAR tumors.

Adenoviruses, Canine↗
PubMed1991

Rescue of a foreign gene by Sendai virus.

A simple protocol for the rescue of a synthetic genome into a paramyxovirus has been developed. First, a synthetic Sendai virus-like RNA, containing the antisense coding region of the chloramphenicol acetyltransferase gene replacing the coding region of the Sendai virus genome, was transcribed from a cDNA. When introduced into cells that are infected with Sendai virus, this RNA construct was transcribed, replicated, and packaged into infectious virions. The addition of infected cell extract to the RNA prior to transfection markedly enhanced levels of chloramphenicol acetyltransferase expression and rescue. However, this enhancement is not due to encapsidation of the RNA into nucleocapsids as the RNA remains nuclease-sensitive. Uninfected cell extract also enhances expression and rescue efficiency, implying involvement of a cellular factor(s) with the synthetic viral-like RNA construct that allows for enhanced polymerase recognition. This system should allow for the dissection of the various cis-acting RNA signals within the paramyxovirus genome.

Animals↗