Recreating HIV resistance

As the rates of HIV infection rise around the world, a small percentage of people will never have to worry about contracting the disease. They are naturally resistant to the virus. Scientists in Philadelphia are working on a treatment that would recreate this resistance through genetic modification. From WHYYs health and science desk Kerry Grens reports.

As the rates of HIV infection rise around the world, a small percentage of people will never have to worry about contracting the disease. They are naturally resistant to the virus. Scientists in Philadelphia are working on a treatment that would recreate this resistance through genetic modification. From WHYYs health and science desk Kerry Grens reports.

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Transcript:

Behind a biohazard door plastered with warnings, scientists in labcoats and gloves hunch over work benches.

Perez: We have three hoods in there, a wall of incubators, refrigerators, 2 centrifuges…

Elena Perez, an assistant professor at the University of Pennsylvania, says this room was her second home for years. She’s been trying to develop an HIV treatment based on a rare human trait.

Perez: We’re really kind of modelling this approach after you could call an experiment of nature.

In the 1990s scientists discovered that about one percent of caucasians are naturally immune to HIV infection. Stephen O’brien, chief of the Laboratory of Genomic Diversity at the National Cancer Institute, helped uncover why. He looked at the genes of people who had been exposed to HIV, but never contracted the virus.

O’Brien: When we looked at these people we discovered that some of them had two copies of this delta 32 mutation in the ccr5 gene.

This mutation in the gene called ccr5 blocks HIV’s entry into a person’s immune cells — keeping them infection-free. O’Brien says that immediately researchers and companies jumped on the idea that perhaps they could mimic the same mechanism. Just this year the first medicine using this logic became available to patients. The drugs seems to work, but it’s expensive and difficult to administer. Another problem with HIV drugs is that some people become resistant to them over time. Perez and her colleague Carl June at UPenn School of Medicine, are working on a different approach by genetically modifying immune cells.

June: So the prediction would be if we could edit the gene so that it would no longer function, then they would have an immune system that would be virtually HIV proof, and have the same thing as people who are lucky and inherit the genes.

June and Perez started with mice — they take out some of their immune cells that are circulating in the blood — and in a test tube add a molecule that acts like scissors for DNA. The scissors snip the ccr5 gene, crippling its function. They then inject the immune cells back into the mice, and voila — the mice can stave off infection. June says his hope is that in HIV-infected adults, these genetically modified immune cells could replace the cells that die off from infection.

June: Because these cells can divide, even the ones that have had the gene disrupted, they can then repopulate with cells that are resistant to HIV and reconstitute the immune system. June says the procedure could be similar to a series of blood transfusions. Eric Daar, the chief of the division of HIV medicine at the Los Angeles Biomedical Research Institute, cautions that successfully modifying genes in human immune cells is no guarantee.

Daar: Even if you can get to that point, which is pretty far off still. But the next step. Then the question is can you do this in a large way for many people. It’s a much bigger undertaking than just giving people medication.

June expects clinical trials in humans on the safety of the procedure to begin this winter. From WHYY’s health and science desk, I’m Kerry Grens.