![]() ![]() ![]() 5 Rep proteins are also needed for the preferential integration of wtAAV genomes into human chromosome 19 9–11 and presumably for the rescue of the integrated genome upon superinfection with a helpervirus. During productive viral replication, the Rep proteins are needed for DNA replication as well as packaging of the viral DNA into preformed capsids. ![]() The AAV genome organization is simple and consists only of a rep and a cap gene flanked by two inverted terminal repeats (ITRs). 6–8 For a recent review of AAV biology, see ref. 5 The infectious virus particle consists of a small (20–25 nm in diameter), icosahedral capsid containing a linear, single-stranded DNA genome, approximately 4.7 kb in length, with plus and minus strands packaged with equal efficiency into preformed, empty viral particles composed of 60 copies of the three viral proteins VP1, VP2, and VP3. 4 In contrast to most other members of the Parvoviridae family, AAV is replication defective and is only able to replicate efficiently in the presence of a helper virus such as adenovirus or herpes virus. 1 Among the most attractive features of AAV vectors are the lack of pathogenicity of wild-type AAV, 2, * the availability of a variety of serotypes with broad but distinct tropism, and the low immunogenicity of AAVs.ĪAV is a nonenveloped, single-stranded DNA virus of the Parvoviridae family and was first discovered as a contaminant of adenovirus preparations. Moreover, the treatment of lipoprotein-lipase deficiency with an AAV vector is the first clinically approved gene therapy treatment in the Western world. O ver the past years, adeno-associated virus (AAV)-based vectors have gained rising attention as a gene delivery vehicle for preclinical research and are used increasingly in clinical trials to treat a large number of diseases. The main purpose of this review is to assess the current literature with respect to dual-AAV-vector design, to highlight the effectiveness of the different methodologies and to briefly discuss future areas of research to improve the efficiency of dual-AAV-vector transduction. Coinfection of a cell with these two rAAVs will then-through a variety of mechanisms-result in the transcription of an assembled mRNA that could not be encoded by a single AAV vector because of the DNA packaging limits of AAV. Among the most promising approaches to overcome the limitation imposed by the packaging capacity of AAV is the use of dual-vector approaches, whereby a transgene is split across two separate AAV vectors. Hence, approaches to overcome this limitation have become an important area of research for AAV gene therapy. Nonetheless, for certain diseases the packaging limit of AAV does not allow the delivery of a full-length therapeutic protein by a single AAV vector. Excluding the ITRs, for a protein of typical length, this allows the incorporation of ∼3.5 kb of DNA for the promoter, polyadenylation sequence, and other regulatory elements into a single AAV vector. ![]() For most applications this is not of major concern because the median human protein size is 375 amino acids. One limitation of rAAVs is that their genome-packaging capacity is only ∼5 kb. Moreover, rAAVs have a low immunogenic profile, and the various AAV serotypes and variants display broad but distinct tropisms. rAAVs are attractive vectors for several reasons: wild-type AAVs are nonpathogenic, and rAAVs can trigger long-term transgene expression even in the absence of genome integration-at least in postmitotic tissues. Recombinant adeno-associated virus vectors (rAAV) are being explored as gene delivery vehicles for the treatment of various inherited and acquired disorders. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |