It targets specific cells exactly where the virus enters the body, stimulating them to generate an immune response so the virus can’t take hold.
If the strategy bears out, the vaccine will be a single dose and last a lifetime, says Marie-Claire Gauduin, PhD, assistant scientist at Texas Biomedical Research Institute.
“Many other HIV vaccines try to block the infection when the virus is already in,” she says. “Here we try not to be infected to begin with,” Gauduin tells Take Part.
About 33 million people worldwide are living with HIV/AIDS, according to estimates by the Joint United Nations Programme on HIV/AIDS. Most do not know it. The new vaccine, if perfected, could be given to children at puberty to stem this toll, Gauduin says.
Most new cases of HIV infections worldwide are transmitted by sexual intercourse through outer layers of cells known as epithelial cells. These line the surfaces of structures throughout the body.
The target of the new vaccine is the mucosal layers of the epithelium in the genital and rectal areas, where the virus typically enters.
“We are targeting the basal layer, the lower layer of epithelial stem cells,” she says. These stem cells divide and differentiate into specialized cell types.
The vaccine stays put in the epithelial stem cells, she says. Next, antigens that recognize the virus are produced. “These antigens stimulate your immune response to fight the virus,” she says.
“The virus will be recognized at the site of entry,” she says. “The virus won’t get to the blood stream is the hope.”
What makes it long lasting, she says, is the initial targeting of the stem cells. “Once the epithelial stem cell gets the message to stimulate your immune response, it will do so constantly,’’ she says, so the virus will be recognized long term.
Gauduin and her colleagues recently filed for a patent on the approach.
The vaccine, of course, is years from clinical practice, she says. “We have a lot of work to do,” she tells Take Part. Primate studies may start in early 2013. Human trials may begin as early as 2015.
Currently, other HIV vaccine approaches can’t deliver the antibody production for long periods of time. So the protection is weak and temporary, Gauduin says.
“It looks very interesting, certainly a great idea,” say Yegor Voronin, PhD, science officer for Global HIV Vaccine Enterprise, an alliance devoted to developing a preventive HIV vaccine.
The approach makes sense to scientists like him. “Epithelial cells don’t live very long,’’ he says. “They are continuously shed off. They are trying to affect the stem cells that produce epithelial cells. As the stem cells differentiate into epithelial cells, that is when they start producing the antigen.”
“It’s very early stages,” he says. “It’s an excellent idea. Whether it will work–who knows?”
Many other attempts have not panned out, he says.
One important as-yet unanswered question, he says, is whether the vaccine could cause some sort of health problem “and you have the antigen being expressed continuously.” He asks: “How are you going to turn that off?”
Much safety testing, among other research, will be needed, he says.
As with other vaccines under development, he says a wait-and-see stance is best. “At this point, it’s just way too early to tell.”