Human Embryonic Stem Cell Therapeutic Strategies to Target HIV Disease

Human Embryonic Stem Cell Therapeutic Strategies to Target HIV Disease

Funding Type: 
Comprehensive Grant
Grant Number: 
RC1-00149
Award Value: 
$2,401,903
Disease Focus: 
HIV/AIDS
Immune Disease
Stem Cell Use: 
Embryonic Stem Cell
Status: 
Closed
Public Abstract: 
AIDS is a disease that currently has no cure. It arises when the human immunodeficiency virus (HIV) infects certain types of blood cells. These cells would normally be used to fight infection, but instead are destroyed by the virus, leading to immunodeficiency. We have recently been able to induce the development of human embryonic stem cells (hESC) into the types of cells that HIV can infect. In addition, we were able to show that a marker gene could be introduced into the hESC, and this gene continued to produce its protein throughout development of the cell into the more mature blood cell types. This sets the stage for testing the possibility of using gene-modified hESC to treat HIV or other immune system diseases. We have 3 different types of anti-HIV genetic approaches that we will test in laboratory models. These will be placed into hESC, and the cells allowed to develop into blood cells. We will then test whether our “therapeutic” genes can inhibit HIV infection in culture. We will also develop novel mouse models that allow development of hESC into blood cells in the body (in vivo). We will test the efficacy of certain of these genetic approaches in these systems, as they should more closely represent the situation in people. These studies will provide proof-of-principle that cells in the immune system can be modified by manipulation of hESC, and may help to develop future therapeutic approaches to combat HIV disease. In addition, these studies will be relevant to other immune system disorders such as autoimmune diseases. It was estimated that by January 31 2005, approximately 151,000 Californians were HIV infected. Furthermore, according to the California HIV Surveillance Report, 1752 new cases of HIV infection (1700 adult and 52 pediatric cases), and 5 deaths were reported between April 1 and September 31, 2006. Current treatment strategies prolong life, but do not cure infection, and are themselves quite toxic. Consequently HIV disease, and improved therapeutic approaches for this disease, are issues of great importance to the people of California.
Statement of Benefit to California: 
Current treatment strategies to halt HIV infection (AIDS) prolong life, but do not cure infection, and are themselves quite toxic. There are over 150,000 Californians infected with the AIDS virus. Consequently HIV disease, and improved therapeutic approaches for this disease, are issues of great importance to the people of California. Our studies will explore the potential of using human embryonic stem cells to fight AIDS and HIV infection. We have shown that human embryonic stem cells can develope into the immune system cells that are destroyed by the AIDS virus. In addition, we are exploring ways to genetically modify these cells (gene therapy) so that they would be protected from infection, and be better able to fight the infection in the body. We hope to eventually use these genetically modified cells to treat HIV infected individuals. If successful, our results may allow HIV infected individuals to discontinue, or greatly reduce the amount of anti-viral drugs that they must now take. This could directly benefit the patients' health, cut the cost of therapy, and allow less productive time lost from work, thus benefitting the State economy as a whole.
Progress Report: 

Year 1

This CIRM grant was designed to explore the potential to genetically manipulate human embryonic stem cells (hESC), to develop new approaches to combat and protect against AIDS virus (HIV) infection. This is an important goal, because even though current anti-HIV medications are quite beneficial, they are expensive, may have unwanted side effects, and must be taken for the remainder of the patient’s life. Stem cell gene therapy approaches may have the ability to provide long-term protective effects for the patient. HIV infects several different types of blood cells, most notably CD4+ T cells and macrophages. Both of these cell types express CD4, the protein that allows the virus to attach to and infect the target cell. Our initial studies optimized macrophage and T cell development from hESC, which should allow us to subsequently introduce our candidate genetic approaches into hESC, and then test the ability of these genes to function in these blood cells derived from hESC. Several different approaches are being tested to maximize the potential for controlling or eliminating HIV from the body of infected individuals, These are in various stages of development. One area that has shown promise, which initially involved the use of hematopoietic stem cells as a prelude to working with hESC, is engineering stem cells such that mature cells that develop from these stem cells can actually attack HIV infected cells. It is our hope that genetically manipulated hESC will allow us to replace cells lost to HIV infection with cells protected against viral infection, and/or to develop strategies that allow the body to defend itself against infection.

Year 2

This CIRM grant was designed to explore the potential to genetically manipulate human embryonic stem cells (hESC), to develop new approaches to combat and protect against AIDS virus (HIV) infection. This is an important goal, because even though current anti-HIV medications are quite beneficial, they are expensive, may have unwanted side effects, and must be taken for the remainder of the patient’s life. Stem cell gene therapy approaches may have the ability to provide long-term protective effects for the patient. HIV infects several different types of blood cells, most notably CD4+ T cells and macrophages. Both of these cell types express CD4, the protein that allows the virus to attach to and infect the target cell. Our initial studies optimized macrophage and T cell development from hESC, which has allowed us to introduce our candidate genetic approaches into hESC, and then test the ability of these genes to function in these blood cells derived from hESC. Several different approaches are being tested, some in hESC and others in hematopoietic stem cells (HSC) to maximize the potential for controlling or eliminating HIV from the body of infected individuals. These are in various stages of development. One area that has shown promise, which initially involved the use of HSC as a prelude to working with hESC, is engineering stem cells such that mature cells that develop from these stem cells can actually attack HIV infected cells. This type of technology could be extended to other chronic infectious diseases or cancers. A second approach involves manipulating cells such that they control virus replication. Development of this latter approach is ongoing. It is our hope that genetically manipulated hESC will allow us to replace cells lost to HIV infection with cells protected against viral infection, and/or to develop strategies that allow the body to defend itself against infection.

Year 3

This CIRM grant was designed to explore the potential of human embryonic stem cells to develop into cells found in the blood, and to adapt these stem cells with genetic approaches to combat infection by the AIDS virus. Over the course of this grant we made significant progress in showing that human embryonic stem cells can develop into several types of blood cells. Importantly this includes T lymphocytes, including cells of the CD4+ T cell lineage and cells of the macrophage lineage, which are the main cell types that can be infected by the AIDS virus. We had originally proposed several genetic strategies to either prevent HIV from productively infecting target cells, or to allow cells to directly attack virally infected target cells. To date we have shown that we can add new genes into human embryonic stem cells, and that we can control their expression in mature T lymphocytes derived from these stem cells, however the process of development of T cells from embryonic stem cells is very difficult and inefficient. We had the most success with one of our three genetic approaches, however to best test the efficacy of this approach, we took a step back and assessed its usefulness using human bone marrow-derived stem cells, which are much easier to convert into mature human T lymphocytes than are human embryonic stem cells. The successful strategy involved the genes for a cell surface molecule, called the T cell receptor (TCR). The TCR is the molecule that normal T lymphocytes use to target and attack foreign or infected cells in the body. These molecules are exquisitely specific for particular foreign particles, and will only recognize a particular pathogenic agent. Thus for example, a TCR specific for measles virus will not detect cells infected with the AIDS virus. We engineered genes encoding a TCR that specifically recognized a part of the AIDS virus that could be detected on infected cells, and inserted these genes into the bone marrow stem cells. Following this, we directed the development of these genetically altered stem cells into T lymphocytes, by implanting them into a mouse that contained human immune tissues required for the development of these cells into a mature state. This strategy allowed the genetically engineered stem cells to develop into CD8+ “killer” T lymphocytes that could detect and kill HIV infected cells. Theses T lymphocytes did not kill normal, uninfected cells, thus we engineered cells that could target and eliminate HIV infected cells. We are continuing to explore this system, and to adapt and improve this method such that it can be employed with human embryonic stem cells.

Year 4

Our project was designed to develop new genetic approaches that could be introduced into stem cells to combat HIV (AIDS virus) infection. We have used this recent time to complete experiments demonstrating that cell surface molecules that direct cytotoxic T cells towards their HIV-infected targets, can be introduced into human blood-forming stem cells. These in turn direct the stem cells to develop into killer T cells that can attack HIV infected cells. We have tested this approach in a new in vivo model, and found it to be highly efficacious. The introduction of this genetic engineering approach allowed the animals to control HIV infection, and preserved the presence of CD4 T cells, which are normally killed by the virus.

© 2013 California Institute for Regenerative Medicine