The researchers started with blood-forming stem cells normally found in the bone marrow. These cells form all the cells of the human blood system including immune and red blood cells. They then inserted a gene from an immune cell of an HIV-infected individual. That protein can recognize the HIV virus and would ordinarily guide the person’s immune system to attack infected cells. In an HIV-infected person so few of those infection-fighting cells exist that the immune system can’t do its job.
The idea was that blood-forming stem cells carrying that HIV-targeting protein would mature into an immune system primed to recognize and destroy HIV-infected cells.
To test their idea, the authors inserted the engineered stem cells into mice. These mice also had transplanted into them a human thymus, the organ that is responsible for making a population of infection-fighting cells called T cells. (The human T cells can’t mature properly in the mouse thymus. By implanting the mouse with a human thymus the researchers mimicked how the cells might behave in a human.) As they hoped, the blood-forming stem cells produced human T cells that were able to kill HIV-infected cells.
The authors called this study a proof-of-principle, saying that by inserting different proteins into the blood-forming stem cells they could direct the immune system to attack Hepatitis, herpes or human papillomavirus.
A press release by UCLA quotes Jerome Zack, an author on the paper and CIRM grantee, as saying:
"This approach could be used to combat a variety of chronic viral diseases. It's like a genetic vaccine."PLoS ONE, December 7, 2009
CIRM funding: Jerome Zack (RC1-00149)