Statement of Benefit to California:
SYNOPSIS: The applicant proposes to genetically modify hESC to down regulate Class I HLA to achieve immunological evasion without the need for severe immunosuppression treatments. Aim 1 proposes to test lentiviral-mediated transduction of hESC with siRNA targeting all or specific Class I HLA alleles. Aim 2 proposes to characterize the level of HLA inhibition upon differentiation of siRNA transduced hESC into hematopoietic lineages. Aim 3 proposes to establish a fully reconstituted SCID-hu mouse model for in vivo testing of strategies to prevent allograft rejection of hESC-derived cell transplants. INNOVATION AND SIGNIFICANCE: This is a very innovative and potentially highly significant study to use siRNA methods to inhibit Class 1 HLA expression in human ESC-derived cells and to test the immune response to these cells in vitro and in vivo. In general, these studies are well conceived and have a good chance at yielding important and significant results. STRENGTHS: This proposal demonstrates that the PI is well versed on multiple fields, including siRNA knockdown methodologies, human ESC, and immunology-based studies. In general, this is a coherent set of experiments that does a good job of fitting the model for these SEED grants. The aims to first test lentivirus-mediated knockdown of Class 1 HLA is appropriate and the scope of the siRNAs to be tested using either antigen-specific or pan-specific siRNAs provides a good chance of success. The second aim to use hematopoietic differentiation should be achievable and the in vitro immune testing using pre-screened T-cell lines and NK cells is reasonable. The third aim to test in vivo response is more exploratory but a logical follow-up to the other studies. There is a good discussion of potential problems and proposed solutions. There is strong preliminary data, including design of the lentiviral vectors and the effective use of this siRNA method in 293 cells. WEAKNESSES: More information about the known Class 1 HLA expression on the H1 cell line could be provided; it is unclear whether these cells are HLA-A2 positive. The PI states that they will get the H1 cells from Dr. Zach, their collaborator. As the PI is an independent investigator, she should make arrangements to obtain cells independently. The studies proposed in aim 3 using the in vivo model, in collaboration with Dr. Zach, may have a hard time demonstrating effective immune response against these cell lines as T-cell or other immune cell engraftment of these mice is limited, though important other information can be obtained. DISCUSSION: The PI has extensive experience with siRNA work and presents a sound and well-ordered experimental strategy. The work is novel because although several groups are using siRNAs in ESC work, but not many are doing immune suppression studies.