New approach makes cells resistant to HIV, researchers find
“This protection would be long term,” said Jia Xie, senior staff scientist at TSRI and first author of the study published today in the journal Proceedings of the National Academy of Sciences.
The researchers, led by study senior author Richard Lerner, M.D., Lita Annenberg Hazen Professor of Immunochemistry at TSRI, plan to collaborate with investigators at City of Hope’s Center for Gene Therapy to evaluate this new therapy in efficacy and safety tests, as required by federal regulations, prior to testing in patients.
“City of Hope currently has active clinical trials of gene therapy for AIDS using blood stem cell transplantation, and this experience will be applied to the task of bringing this discovery to the clinic,” said John A. Zaia, M.D., director of the Center for Gene Therapy in the Hematological Malignancy and Stem Cell Transplantation Institute at City of Hope. “The ultimate goal will be the control of HIV in patients with AIDS without the need for other medications.”
“We at TSRI are honored to be able to collaborate with physicians and scientists at City of Hope, whose expertise in transplantation in HIV patients should hopefully allow this therapy to be used in people,” added Lerner.
The new TSRI technique offers a significant advantage over therapies where antibodies float freely in the bloodstream at a relatively low concentration. Instead, antibodies in the new study hang on to a cell’s surface, blocking HIV from accessing a crucial cell receptor and spreading infection.
Xie called it the “neighbor effect.” An antibody stuck nearby is more effective than having many antibodies floating throughout the bloodstream. “You don’t need to have so many molecules on one cell to be effective,” he said.
Before testing their system against HIV, the scientists used rhinovirus (responsible for many cases of the common cold) as a model. They used a vector called lentivirus to deliver a new gene to cultured human cells.
This gene instructed cells to synthesize antibodies that bind with the human cell receptor (ICAM-1) that rhinovirus needs. With the antibodies monopolizing that site, the virus cannot enter the cell to spread infection.
“This is really a form of cellular vaccination,” said Lerner.Because the delivery system can’t reach exactly 100 percent of cells, the finished product was a mix of engineered and unengineered cells. The researchers then added rhinovirus to these cell populations and waited to see what would happen.
The vast majority of cells died in about two days. In dishes with only unengineered cells, the population never recovered. There was an initial die-off in the mixed engineered/unengineered populations, too, but their numbers quickly bounced back. After 125 hours, these cell populations were back up to around the same levels as cells in an undiseased control group.
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