Immune Cells Engineered in Lab to Resist HIV Infection, Stanford Study Shows



"We inactivated one of the receptors that HIV uses to gain entry and added new genes to protect against HIV, so we have multiple layers of protection what we call stacking," says Porteus, the study's principal investigator. "We can use this strategy to make cells that are resistant to both major types of HIV."


"Providing an infected person with resistant T cells would not cure their viral infection," says Sara Sawyer, PhD, assistant professor of molecular genetics and microbiology at the University of Texas-Austin and a co-author of the study. "However, it would provide them with a protected set of T cells that would ward off the immune collapse that typically gives rise to AIDS."

The study is published in the Jan. 22 issue of Molecular Therapy.

One of the big challenges in treating AIDS is that the virus is notorious for mutating, so patients must be treated with a cocktail of drugs known as highly active antiretroviral therapy or HAART which hit it at various stages of the replication process. The researchers were able to get around that problem with a new, multi-pronged genetic attack that blocks HIV on several fronts. Essentially, they hope to mimic HAART through genetic manipulation.





Blocking HIV infection through both the CCR5 and CXCR4 receptors is important, Porteus said, as it hasn't been achieved before by genome editing. To test the T cells' protective abilities, the scientists created versions in which they inserted one, two and all three of the genes and then exposed the T cells to HIV.

Though the T cells with the single- and double-gene modifications were somewhat protected against an onslaught of HIV, the triplets were by far the most resistant to infection. These triplet cells had more than 1,200-fold protection against HIV carrying the CCR5 receptor and more than 1,700-fold protection against those with the CXCR4 receptor, the researchers reported. The T cells that hadn't been altered succumbed to infection with 25 days.


"I'm very excited about what's happened already," he says. "This is a significant improvement in that first-generation application."

He says a potential drawback of the strategy is that while the nuclease is designed to create a break in one spot, it could possibly cause a break elsewhere, leading to cancer or other cell aberration. He said it's also possible the cells may not tolerate the genetic change.

"It's possible the cells won't like the proteins they're asked to express, so they won't grow," he adds.

But he said he believes both problems are technically surmountable. He said the researchers' next step is to test the strategy in T cells taken from AIDS patients, and then move on to animal testing. He said he hopes to begin clinical trials within three to five years.



In addition to Sawyer, he collaborated with Richard Voit, a former Stanford graduate student who is now an MD/PhD candidate at the University of Texas Southwestern Medical Center, and Moira McMahon, PhD, a former postdoctoral scholar at Stanford who is now at the University of California-San Diego.
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