PubMed · 11653721
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1986-06-07. Field-test ups and downs.. https://pubmed.ncbi.nlm.nih.gov/11653721/
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In an attempt to exploit the remarkable tissue-tropism of the human parvovirus B19 to target human hematopoietic cells of the erythroid lineage, recombinant human adeno-associated virus 2 genomes were encapsidated in parvovirus B19 capsids. Although efficient transduction of primary human hematopoietic cells in the erythroid lineage occurred, a low-level of transgene expression in non-erythroid cells was also detected. These studies suggest that cell surface expression of P antigen, the primary receptor for parvovirus B19, is necessary but not sufficient for parvovirus B19 vector-mediated transduction of human hematopoietic cells. These studies also suggest the existence of a putative cell surface co-receptor, which is required for successful infection of human hematopoietic cells by parvovirus B19.
Virus expression vectors based on the tobacco mosaic virus (TMV) genome are powerful tools for foreign gene expression in plants. However, the inclusion of increased genetic load in the form of foreign genes limits the speed of systemic plant invasion and host range of these vectors due to reduced replication and movement efficiencies. To improve these properties of TMV vectors, the gene encoding the 30-kDa movement protein was subjected to mutagenesis and DNA shuffling. A vector that expresses the green fluorescent protein was used to allow simple visual discrimination of mutants with enhanced movement phenotypes. An initial round of mutagenesis produced 53 clones with a faster local movement phenotype. Two subsequent rounds of DNA shuffling produced additional clones that showed further increased rates of cell-to-cell movement and degrees of systemic invasion in restrictive hosts. Surprisingly, sequence analysis of the best performing shuffled genes revealed alterations resulting in coding and silent changes in the movement protein gene. Separation of these coding and silent alterations into distinct gene backgrounds revealed that each contributes to improved movement protein function to differing degrees. The resulting vectors demonstrate that the complex activities of the movement protein genes of viruses can be evolved to have improved movement phenotypes, as evidenced by cell-to-cell and systemic invasion. The experiments produced improved vectors that will be of use both for in planta functional screening and for therapeutic protein production and demonstrated the power of shuffling for plant virus vector improvement.
PCR detection of genetically modified (GM) line-specific recombinant DNA was carried out on Bt 11, Event 176 and Non-GM maize grain harvested in 1999. Of 100 grains of Bt 11 line, Event 176 specific DNA was detected in 11 grains. Of 30 grains of Event 176 line, Mon 810 or Bt 11 specific DNA was detected in 5 grains. In addition, Bt 11 or Event 176 specific DNA was detected in 4 of 30 Non-GM grains. These data suggest that maize grains (not seed) often contain DNAs of different lines from what they were expected to contain. Furthermore, quantitative PCR was performed to estimate the genotype of the Event 176 grains described above. The results showed that the genotype of all the grains containing different recombinant DNA is heterozygous. Therefore, it was considered that the grains containing the unintended recombinant DNA were not accidental contaminants, but that airborne pollination had introduced the recombinant DNA into the grains.