Patients benefit from using own CD4 T-cells
Stimulating CD28 receptor causes HIV resistance
HIV researchers continue to explore novel ways to fight the disease and enhance the benefits of antiretroviral therapy. One new approach involves transferring activated autologous CD4 T-cells into HIV-infected patients with a goal of augmenting natural immunity to HIV infection. Reconstituting CD4 helper cell activity, along with decreasing CCR5 expression, may augment natural immunity to HIV infection, according to the study published in Nature Medicine.1
"Around 1994, we were a lab interested in T-cell activation, and we developed a way to grow T-cells more efficiently than had been previously published," says Bruce L. Levine, PhD, an investigator in the Abramson Family Cancer Research Institute at the University of Pennsylvania, and director of the Clinical Cell and Vaccine Production Facility at the University of Pennsylvania Cancer Center in Philadelphia. "The director of the program I work for thought that it could provide a way to reconstitute the immune system in infections or cancer," Levine says.
So Levine and other researchers began to study the benefits of this approach among HIV-infected patients. "We got cells from HIV-infected donors at the U.S. Navy, and I grew them in the lab with and without antiretroviral drugs in a growth media," Levine explains. "So the thinking at the time was that if you activate HIV-infected CD4 cells, then you activate the virus, and you wouldn’t be able to culture those cells for a long time, and that’s why we had antiretroviral drugs in media."
However, investigators found that the virus didn’t grow under either condition. This led to the discovery that stimulating the CD28 receptor would turn off the production of CCR5 receptors within the CD4 cells, and this would lead to HIV resistance, Levine says.
CD4 T-cells were co-stimulated
After publishing their findings, Levine and co-investigators set up a clinical trial. "At first we enrolled three drug-naive people and used this method of stimulation on their T-cells," Levine says. "So they came into a blood bank and underwent apheresis, a procedure used to donate platelets for patients undergoing chemotherapy."
Using a negative selection method, investigators took the antibodies against the unwanted cells and added them to the white cell population, and then removed them with magnetic beads. This left a population that was fairly enriched for CD4 T-cells, Levine says. The next step was to stimulate the enriched cells for two weeks and then harvest and wash the cells. They were concentrated and infused in three escalating doses six weeks apart, he says. "This was a phase I trial designed to test safety and feasibility, so we were looking for increases in CD4 counts and for the CD4-to-CD8 ratio," Levine says. "The second element was to observe whether there was a lack of increase in the viral load."
Investigators saw no spikes in viral load in any of the patients, and there was an increase in CD4 count, he notes. "In the first three patients, it was so remarkable that we filed an amendment to include people who had been on drug therapy before," Levine says. "The second cohort of five patients went through the study and had the same dose protocol." Altogether they studied eight patients with a total of 51 infusions. After each patient received the first three doses, investigators again amended the protocol to include a second part where the subjects could receive additional infusions every eight weeks, Levine says.
"The investigational lab aspects were looking at immune response of these people before and after their infusions and were looking at some measures of their immune system to give us an indication of whether the cells we infused were persisting or dividing," he says. "The most remarkable of those were that we showed an increase in IL2 response and a decrease in vivo on CD4 T-cells of the CCR5 receptor, which is the HIV coreceptor."
The research demonstrates that HIV resistance is created by infusing the stimulated CD4 T-cells in HIV patients, Levine says.
Supplement to drug therapy
"The study shows the uniqueness of this method of stimulation, and it shows that the cells when they are infused are highly resistant to HIV," Levine adds. Also, there were no upward spikes in viral load among the treatment-naive subjects. Among the people receiving highly active antiretroviral therapy (HAART), when the viral load was undetectable, it remained so, Levine says. "We looked by more sensitive methods for changes in the latent HIV viral load, and that either did not change, or in a couple of patients it looked like it decreased," Levine says. "But it’s hard to separate the effect of the drugs and the effect of the infusions because this is a small study."
Should clinical research lead to a new treatment approach for HIV infection, it will give a boon to the arsenal of HIV drugs and treatment, especially these days when there are increasing reports of drug-resistant virus, Levine notes. "Drug regimens are difficult to adhere to for most people, so it appears to us as though drug therapy has several problems with it," he adds. "In addition to that, drugs do not eradicate HIV from the body, and there’s a latent HIV reservoir, so we see this new approach as a supplement to drug therapy."
It should help patients on HAART by reconstituting their immune systems and giving them greater immunity to HIV as well as to opportunistic pathogens. "And perhaps it will reduce this latent HIV reservoir and help with the goal of having patients live healthy with HIV for the long term," Levine says. Investigators are pursuing this method and now are continuing trials based on the technique, Levine says. "This is a gene transfer trial that’s currently run at Walter Reed Army Medical Center in Washington, DC, and patients are coming in there and we’re doing the subprocessing at Penn," he says.
A current randomized phase I/II trial involves using this method of activation and immune reconstitution in treating cancer patients, Levine says. "This method has potential for wide application in treating cancer and autoimmune disease as a supplement, not as stand-alone therapy," he says. "We see it not as a substitute for drug therapy, but as a supplement to it." The trial is open only to active-duty or retired military personnel.
"A third trial opening up will be open to the general population, but as with all trials, there will be certain inclusion and exclusion criteria," Levine says. The third trial is expected to begin in the summer, he says.
Editor’s note: For more information about the clinical trials, go to the following Web sites:
You can also contact Bruce L. Levine, PhD, Director, Clinical Cell and Vaccine Production Facility, University of Pennsylvania Cancer Center, Room 553, BRB 2/3, 421 Curie Blvd., Philadelphia, PA 19104-6160. Telephone: (215) 573-6788. Fax: (215) 573-8590. E-mail: LevineBL@mail.med.upenn.edu.
1. Levine BL, Bernstein WB, Aronson NE, et al. Adoptive transfer of co-stimulated CD4+ T cells induces expansion of peripheral T cells and decreased CCR5 expression in HIV infection. Nature Med 2002; 8:47-53.