Research in the Gao Lab primarily involves the discovery, development and use of adeno-associated virus vectors for gene therapy of genetic diseases and the study of miRNA functions in mammals. The lab continues to work on isolation, characterization and vectorology of novel AAV vectors from primate tissues, molecular mechanisms of AAV evolution and diversity, and molecular interactions between endogenous AAV, AAV vector, host genomes and innate RNAi defense pathways. We also develop novel strategies for rAAV gene therapy of an inherited neurodegenerative disease, Canavan Disease, using novel AAVs that can cross the blood-brain-barrier for efficient CNS gene delivery and endogenous miRNA-mediated posttranscriptional de-targeting. Another area of research interest in the lab is to explore AAV vectors for delivery of denovo synthesized biological miRNA antagonists or over express microRNAs to elucidate micro RNA functions in adult mammals.
1. AAV vector holds great promise for gene therapy application. Our lab previously isolated a diverse family of natural variants of primate AAVs some of which have unique tissue tropism and can accomplish highly efficient and stable gene transfer. We are currently expanding the novel AAV discovery effort to chimpanzee tissues, considering its phylogenetic closeness to humans. We focus our effort on isolating the naturally selected and evolved variants of those AAVs that are proven to be efficient gene transfer vehicles in certain tissue targets such as AAV1 to muscle, AAV5 to lung, AAV6 for muscle, AAV9 for liver, heart and brain by crossing the blood-brainbarrier. The research in this area will not only lead to more novel vector candidates for different applications but also shed light on how AAV evolves in nature.
2. AAV2-based gene therapeutics has been extensively studied in different clinical applications, demonstrating some impressive safety profiles. However, as those more efficient novel primate AAV-derived vectors move into the clinical evaluation stage, it is critically important for us to study interactions of those vectors with endogenous AAVs, host genome and host innate defense systems and potential consequences of such interactions. This is the second area of research interest in the lab.
3. When systemically delivered, some of novel primate AAVs could transvascularly target liver, heart, brain and other major tissues. In an attempt to restrict tissue tropism, de-target gene expression of AAV vectors from unintended tissues, and reduce transgene toxicity and immunogenicity, tissue specific transgene expression becomes another essential safety measure. Traditional transcription regulation by tissue specific promoters in AAV vectors often cannot achieve desired tissue specificity and efficiency due to the limited packaging capacity of AAV. Our lab explores tissue specific endogenous miRNAs as the effective strategy to regulate AAV transduction postranscriptionally with focuses on optimization and mechanisms.
4. To date, more than 600 different species of micro RNAs have been discovered. However, the functionality of those miRNAs in mammals and their possible associations with human diseases remain largely unknown. One attractive strategy to study their function in animal models is to take the advantage of tissue tropism and efficiency of AAV vector to overexpress either miRNAs or their antagonists in adult animals to disrupt miRNA homeostasis. To this end, our lab works on the design, optimization and delivery of expression cassettes for miRNA or their antagonist as well as analysis of biological consequences of their stable over expression by rAAV..
5. Canavan disease is a devastating genetic disease, resulting in fetal white matter spongy degeneration. Currently, there is no effective clinical intervention for the disease. Gene therapy represents a highly promising option for treating the disease. The major challenge for this approach is to efficiently target the entire white matter for gene replacement therapy. A recent study revealed that intravascularly delivered AAV9, one of the novel primate AAVs we previously isolated, can cross the blood-brain barrier and realize extensive gene transfer to both neurons and astrocytes in CNS. Our lab evaluates a panel of natural variants of AAV9 to identity the vector candidates that not only can efficiently cross the blood-brain barrier for CNS gene transfer but also are less immunogenic and toxic. The goal is to combine novel vector platform with miRNA-mediated gene expression regulation for development of effective and safe gene therapeutics for Canavan disease.
1. Zhang H, Xie J, Xie Q, Wilson JM, Gao G. Adenovirus-Adeno-Associated Virus Hybrid for large-scale recombinant adenovirus production. Hum Gene Ther, epub ahead of print, 2009.
2. Gao G, Wang Q, Calcedo R, Mays L, Bell P, Wang L, Vandenberghe LH, Grant R, Sanmiguel J, Furth EE, Wilson JM. Adeno-associated virus-mediated gene transfer to non-human primate liver can elicit destructive transgene-specific T cell Responses. Hum Gene Ther, epub ahead of print, 2009
3. Vandenberghe LH, Wilson JM and Gao G. Tailoring the AAV vector capsid for gene therapy. Gene Therapy. 2009.16(3):311-9.
4. Gao G, Yu L, Johnston J, Calcedo R, Grant R and Wilson JM. High Level Transgene Expression in Nonhuman Primate Liver with Novel AAV Serotypes Containing Self-complementary Genomes. J Virol, 80:6192-6194, 2006.
5. Gao GP, You Lu, Roberto Caceldo, Grant Rebecca, and James Wilson: Biology of Novel AAV Serotype Vector Mediated Liver Gene Transfer in NHPs. Molecular Therapy, 13:77-87, 2006.
6. Gao, G.P., Vandenberghe, L.H. and Wilson J.M. New Serotypes of AAV Vectors. Current Gene Therapy, 2005, (3):285-97
7. Gao GP, Vandenberghe LH, Alvira MR, Lu Y, Calcedo R, Zhou X, and Wilson JM. Clades of Adeno-Associated Viruses are Widely Disseminated in Human Tissues. J Virol, 78: 6381-6388, 2004.
8. Gao GP, Lebherz C, Weiner DJ, Grant R, Calcedo R, Bagg A, Zhang Y, and Wilson JM. Erythropoietin Gene Therapy Leads to Autoimmune Anemia in Macaques. Blood, 103: 3300-3302, 2004.
9. Gao GP, Alvira MR, Somanathan S, Lu Y, Sanmiguel J, Abbas Z, Johnston J, and Wilson JM. Adeno-Associated Viruses Undergo Substantial Evolution in Primates During Natural Infections. PNAS, 100:6081-6086, 2003.
10. Gao GP, Alvira M, Wang L, Calcedo R, and Wilson JM. Novel Adeno-associated Viruses from Rhesus Monkeys as Vectors for Human Gene Therapy. Proc Natl Acad Sci USA, 99: 11854-11859, 2002.
11. Gao, G.P., Qu, G., Faust, Lynn Z., Engdahl, Ryan K., Xiao, W.D., Hughes, J.V., Zoltick, P.W., and Wilson, J.M. High-titer adeno-associated viral vectors from a rep/cap cell line and hybrid shuttle virus. Hum Gene Thera, 9:2353-2362, 1998.
12. Kaul, R., Gao, G.P., Balamurugan, K., and Matalon, R. Cloning of the human aspartoacylase cDNA and a common missense mutation in Canavan Disease. Nature Genet, 5:118-123, 1993.