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Expression vectors and gene transfer.

The development of DNA cloning techniques, together with the possibility of reintroducing cloned DNA fragments into the genome of a living organism, has led to an extraordinary growth of our knowledge in molecular biology over the past twenty years. In the present paper a brief overview of the vectors and techniques used in transforming different groups of organisms is given. The importance and applications of genetic engineering for each group (yeasts, plants, Drosophila and mammals) will be discussed.

Animals

Preclinical evaluation of AL-001, a gene therapy for wet age-related macular degeneration.

BACKGROUND: Frequent intravitreal administration of antivascular endothelial growth factor Vascular endothelial growth factor agents remains a major limitation in the management of wet age-related macular degeneration (wAMD). This study evaluated whether suprachoroidal delivery of an engineered recombinant adeno-associated viral (rAAV)-aflibercept vector could achieve sustained, targeted expression with improved efficacy and safety compared with intravitreal administration. METHODS: AL-001, an engineered rAAV vector expressing aflibercept, was developed and characterized. Its expression profile was first assessed in New Zealand white rabbits following suprachoroidal space (SCS) injection. Efficacy, pharmacokinetics, and safety were then evaluated in a nonhuman primate model of laser-induced choroidal neovascularization (CNV), comparing SCS and intravitreal (IVT) administration routes. RESULTS: AL-001 efficiently expressed aflibercept in relevant ocular cells in vitro. In rabbits, SCS administration produced sustained aflibercept levels in ocular tissues. In the nonhuman primate CNV model, a single SCS injection of AL-001 showed favorable efficacy to IVT injection and a notable mild inflammatory response. At week 4, grade IV lesion incidence was 0% (0/48) after SCS administration versus 14.3% (6/42) after IVT administration (absolute difference, -14.3 percentage points; 95% CI, 3.7%-27.8%; P = 0.0258). Throughout follow-up, mean leakage area and grade IV lesion incidence remained 0 with SCS, versus IVT peaks of approximately 0.3 mm2 and 33.0%, respectively, declining to 0.03 mm2 and 2.0% by day 100. Both the medium and high doses decreased pathological vascular leakage and subretinal hyperreflective material. Vector administration preceded laser-induced CNV modeling, demonstrating that sustained intraocular aflibercept expression in the retina and choroid provided durable antiangiogenic protection. Pharmacokinetic analysis confirmed distinct ocular exposure profiles between routes, with viral genomes confined predominantly to the injected eye and no significant systemic accumulation. AL-001 was well tolerated, without sustained intraocular pressure elevation or severe ocular inflammation, and only mild-to-moderate treatment-emergent adverse events. Low pre-existing anti-AAV2 immunity and time-dependent neutralizing antibody responses postdosing, informing a translational model for patient stratification and redosing feasibility. CONCLUSION: Suprachoroidal administration of AL-001 is well tolerated and provides durable, targeted aflibercept expression with pronounced antiangiogenic efficacy. These results support AL-001 as a promising, long-acting therapeutic candidate for wAMD.

AAV

Legal and regulatory aspects of genetically engineered animals.

The commercialization of genetically engineered food animals will pose a number of legal and regulatory questions. These may be grouped into questions of process and questions of products. The process of animal genetic engineering with artificially constructed vectors will probably be regulated in much the same manner as other veterinary procedures. There may be some discussion, however, as to whether animal drug or animal biologic regulations are more applicable. The products of animal genetic engineering, i.e., transgenic food animals and food products made from them, also raise important questions about product safety and identity. These include whether and how genetically engineered food animals will be subject to federal inspection for wholesomeness, whether artificial vectors, foreign genes, or gene products will adulterate recipient animal tissues, and how food products made from such animals will be labeled. Prior federal experience with the inspection of interspecific hybrids of cattle and buffalo provides a useful basis for further policy developments in the inspection and labeling of genetically engineered food animals. In particular, the inspection of cattle/buffalo hybrids has established a phenotypic (based on appearance) criterion for deciding how novel food animals should be inspected. As the genetic engineering of food animals on a production basis draws nearer, it may be necessary to supplement the phenotypic criterion with genetic (based on pedigree) criteria to assure that the essential characteristics of animals slaughtered under current food statutes are maintained.

Animal Husbandry

Retrovirus vectors for study of biochemical processes.

Retroviruses can be viewed as a collection of different modules controlling different processes. As such, they are very malleable both by genetic engineering and by evolution. They are thus both a useful tool in the laboratory and a dangerous pathogen in nature.

Genetic Engineering

Construction of mobilizable vectors derived from plasmids RP4, pUC18 and pUC19.

Mobilizable narrow-host-range plasmids were constructed from pUC18 and pUC19 by addition of a segment of pSUP2021 bearing the basis of mobilization (bom) site and origin of transfer (oriT) of RP4. One pair of expression vectors, pARO180 and pARO190, retains the beta-lactamase (bla) gene and twelve of the 13 restriction enzyme multiple cloning sites (MCS) of pUC18/19. Another pair was created by replacing the bla gene with the gene encoding kanamycin resistance (kan) from Tn5. The molecules replicate to high copy number in Escherichia coli and Enterobacter aerogenes. They can be transferred efficiently to other Gram- bacteria from the mobilizing strain, E. coli S17-1. In non-enteric strains, the new plasmids can be used as suicide vectors in site-specific insertional mutagenesis.

DNA Mutational Analysis