Researchers at the University of Maryland (UMD) and Duke University have designed a vaccine candidate that could help protect against HIV. Their work was published last week in Cell Chemical Biology.
"An obstacle to creating an effective HIV vaccine is the difficulty of getting the immune system to generate antibodies against the sugar shield of multiple HIV strains," said Lai-Xi Wang, a professor of chemistry and biochemistry at UMD. "Our method addresses this problem by designing a vaccine component that mimics a protein-sugar part of this shield."
To create a vaccine, Wang and his collaborators focused on a protein fragment from gp120, a protein that covers HIV like a protective envelope. The gp120 protein they chose was common among the different HIV strains. They then used synthetic chemistry to combine that gp120 fragment with a sugar molecule that was also shared among the HIV strains, to mimic the sugar shield on the HIV envelope.
After it was created, they injected the protein-sugar vaccine candidate into rabbits and found that the rabbits' immune systems produced antibodies that physically bound to gp120 found in four dominant strains of HIV in circulation today. When they injected the vaccine with just the protein fragment and no sugar group, only antibodies that against one HIV strain developed.
Although the rabbits' antibodies bound to gp120, they did not prevent the live HIV for infecting cells. Wang noted that it usually takes humans two years to build immunity against HIV and their animal study only lasted two months.
"We have not hit a home run yet," Wang said. "But the ability of the vaccine candidate to raise substantial antibodies against the sugar shield in only two months is encouraging; other studies took up to four years to achieve similar results. This means that our molecule is a relatively strong inducer of the immune response."
The group's next steps are to conduct a longer-term study with other vaccine candidates, figure out what areas of gp120 the antibodies are binding to and how to increase the antibodies' effectiveness at neutralizing HIV.
Image: An artist's rendition of HIV (foreground). The knobs (purple) covering the virus are sugar-protein molecules, including gp120, that shield the rest of the virus (pink). Image courtesy of National Cancer Institute.