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Pauliina Lehtolainen
AMERICAN SOCIETY OF GENE THERAPY The ASGT meeting in July 2000 was held in Colorado, Denver. I participated the meeting with the poster titled: Targeted delivery of biotinylated molecules to rat brain using scavidin fusion protein gene transfer. The latest research results in the field of gene therapy were presented. Especially the developments in the gene transfer vectors, in the targeted gene therapy, in regulated gene expression and the news about on-going studies in clinics. Also many young scientists presented their first results; I think the meeting is very suited for that too. A lot of research regarding targeted vectors were presented, based on the development of the new receptors or stripping the native binding site on cells. I review some interesting posters or oral presentations about targeting and a vector named 'sleeping beauty'. Many approaches for development of 'targeting' vectors utilized modification of adenovirus binding proteins. R. Pasqualini et al presented a research about targeting adenoviral vectors to vascular receptors. They have designed molecular adapters that mediate attachment of adenovirus type 5 vectors to organ-specific vascular receptors. Adapters contained organ-homing peptide (lung-homing membrane dipeptidase receptor) conjugated to an Ad5- fiber knob region binding moiety. The vector was able to infect cell lines that were not susceptible to unmodified Ad5 infection. Results indicate that Ad5 vectors can be targeted to specific vascular receptors. A. Durrbach's (et al) poster was titled: Antibody-targeted gene transfer using fusogenic Influenza peptide and histone H1 as a DNA carrier. The vector was targeted by G250 antibody to human renal cancer cells. The fusogenic peptide of hemagglutinin of Influenza was used to favor DNA translocation from the acidic endocytic compartments; the translocation of DNA from endosomes to cytosol and to nucleus is known to be one of the limiting steps in non-viral gene transfer techniques. The histone H1 was used as a carrier to the conjugate because of its ability to interact with DNA. Il -12 was used as a reporter gene. Addition of fusogenic Influenza peptide and histone increased Il-12 production by 10-fold. The stability of the vector was increased; it remained in the endocytic compartments for 1 day and was hardly disrupted in degradative compartments. Vector was also found in nucleus and was targeted to subcutaneous human renal carcinoma cells after one i.v. injection. B. Parrott and M. Barry had an poster about using metabolic biotinylation of recombinant proteins for viral gene therapy vector targeting. They had a method to biotinylate tagged proteins in mammalian cells and mice using the endogenous biotinylation enzymes. This would enable targeting of these biotinylated proteins into various proteins, peptides and antibodies complexed with avidin. They used the technique to biotinylate the fiber protein of adenovirus type 5, VSVG envelope protein and capsid proteins for AAV successfully. P. Hackett et al have developed a system called 'Sleeping beauty', a vector based on retrotransposons; the self-movable elements in genome which mediate stable, single-copy integration of transgenes into chromosomes. The efficacy of transposition was dependent on the ratio of transposase to transposon. The optimal transposon size is 5-6 kb, which includes 1,6-5 kb inserts containing gene of interest, selection marker, ITR etc. Activity was investigated in zebra fish embryos and human HeLa cells and in vivo by production of factor XI. The expression was long lasting being active through F6 generation in mice and regarding factor IX production 6 months reaching therapeutic concentrations, 3 % of normal. As a summary, the meeting was informative and I warmly thank for Finnish gene therapy society getting the travel fund. Otherwise, the trip would have been impossible. Not only the meeting itself was great, but also we had some time to get to known to the city of Denver with colleagues! If something has to be complained about, there was no 'get together parties' arranged, the days were long and all the personal contacts had to be created during the sessions and short brakes or at the posters. And that we got the abstract book on site; not in advance like most of the Americans. The issues could have been seen on the internet, but the web site was slow to use. So, in order to be in right place at the right time needed work; the days were long... but isn't it meant to be so in the meetings? Pauliina Lehtolainen |