UC Santa Cruz researchers are currently developing a novel AIDS vaccine that, they predict, will be ready for clinical trials within the next two years. The researchers are studying an older AIDS vaccine, called AIDSVAX (aka RV 144), that was tested in Thailand back in ’09. Participants in the vaccine trial, which reached 16,000 people, ultimately saw a 31 percent prevention rate (making it the only vaccine known to prevent HIV infection).
The problem with creating an AIDS vaccine stems from HIV manifesting under many different viral strains in an infected person. An effective AIDS vaccine must cause the immune system to create “broadly neutralizing antibodies” for a large range of strains.
AIDSVAX targets gp120—a protein that can prevent HIV infection by binding to a receptor on the exterior of T-Cells—like the new vaccine will. Researchers hope to make a better vaccine by improving on AIDSVAX’s targeting of gp120. Ultimately, the latest trial revealed that certain individuals were equipped with antibodies called “elite neutralizers” after being vaccinated. Participants with these “elite neutralizers” were able to better target gp120 and neutralize multiple strains of HIV.
The AIDSVAX trial also showed that the neutralizing antibodies are drawn to carbohydrates, known as glycans, that are present on the gp120 protein. A future vaccine utilizing glycans can better negate HIV strains.
“We found that the vaccine that gave partial protection in the RV 144 trial had very little of the kind of carbohydrate required to bind these antibodies.” Explained Phil Berman (the lead researcher).
Which is why researchers modified gp120’s epitopes—the structures antibodies are attracted to—to contain more carbohydrate-based glycans. The carbohydrate-rich epitopes then became a favorite target of HIV-preventing antibodies. This novel method that guides antibodies to glycans will lead to a more effective AIDS vaccine.
“By building on an existing vaccine concept, rather than developing a new one from scratch, we can save millions of dollars and years of time getting the new vaccine into the clinic.” Berman noted in a press statement. (You can read a more comprehensive overview here)