HIV continues to be a major public health problem with more than 30 million people infected worldwide. Although small molecule drugs prolong the lives of HIV infected individuals, there is no cure or effective vaccine available. Gene therapy for HIV offers a promising alternative to current treatments due to advantages including the possibility of a one-time treatment, controlled or constitutive anti-HIV gene expression, and long-term viral inhibition upon transduction of blood stem cells with the possibility of creating a "functional cure". HIV is characterized by a prolonged course of infection often spanning several years, thus providing a large window of opportunity for gene therapeutic intervention. All cells susceptible to HIV infection (CD4 T cells, macrophages, and dendritic cells) are derived from hematopoietic stem cells (HSCs). If anti-HIV activity could be introduced into HSCs, this phenotype would be passed on to the differentiated HIV target cells. Current drawbacks to allogeneic and autologous bone marrow transplants for HIV gene therapy with ex vivo engineered HSCs include the possibility of graft rejection and low transduction efficiency which leads to low in vivo cell marking of the transplanted cells.
With the development of induced pluripotent stem cells (iPSCs), however, it is now possible to generate patient-specific pluripotent stem cells from an adult individual. These iPSCs can be maintained in an undifferentiated state and have enormous potential as a source of autologous cells and tissues for therapeutic use. iPSC derived anti-HIV HSCs, generated from patient specific cells, will eliminate the problem of graft rejection. Also, HSCs derived from a single iPSC colony will be clonal thus allowing for complete characterization of the engineered cells including the site of integration of the anti-HIV genes, their functionality, safety, and anti-HIV efficacy. All cells arising from the clonal iPS colony will contain the anti-HIV genes eliminating the problem of low transduction efficiency and in vivo marking of transplanted cells. As iPSCs can be maintained in an undifferentiated state, a continuous supply of HIV resistant cells can be generated. In the proposed research we plan on optimizing the generation of anti-HIV gene expressing iPSCs from multiple cell sources and differentiating these cells into HIV resistant HSCs and immune cells including macrophages and dendritic cells in vitro and T cells, B cell, macrophages, and dendritic cells in vivo in a humanized mouse model. We will characterize the safety, toxicity, functionality, and anti-HIV efficacy of the anti-HIV iPSC derived immune system cells. The data generated from this proposal will bring these novel therapies closer to the clinic.
Statement of Benefit to California:
Currently around 106,000 California residents are infected with HIV while an additional 68,000 have AIDS. California is second only to New York in AIDS cases with no end in sight due to the lack of effective vaccines or a cure. Novel and innovative therapeutic approaches need to be developed to combat this devastating disease. Gene therapy for HIV offers a promising alternative treatment to current antiretroviral drugs with the potential of creating a “functional cure”.
Recently, long term control of viral replication was observed in an HIV-1 infected individual who received a stem cell transplant in Berlin, Germany for acute myeloid leukemia. The transplanted allogeneic stem cells were from an individual who was homozygous for the CCR5 ∆32-bp deletion. This study highlights the importance in developing anti-HIV gene and cellular therapies which are capable of generating HIV-resistant immune system cells. Based on these results, there is hope for developing a novel treatment for HIV infected individuals by generating a continuous supply of HIV resistant autologous cells which could be used for regenerative therapy. With the introduction of iPSC technology, there is now the potential for developing a source of self-renewing pluripotent stem cells capable of indefinite expansion from a patient’s own cells.
All HIV infected individuals, male, female, of any age and race, will be able to benefit from this treatment as we would be using their own cells to generate the HIV-resistant HSCs. The anti-HIV HSCs generated from these iPSC lines can be frozen and stored for future use. This strategy would help overcome the disadvantages of current HIV gene therapy protocols which have obtained minimal in vivo gene marking and the transplantation of a finite number of cells which have not been fully characterized. Also, if subsequent treatments are needed, future transplantations can be administered without having the patient’s cells undergo apheresis, transduction, and re-transplantation due to the continuous supply of HIV resistant immune cells from the patient-specific anti-HIV iPSC lines.