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The vaccine tested by the Step Study so named because it's seen as the next step forward on the long path to success takes a different approach. To make the vaccine, Merck's researchers replicated three individual genes from the HIV virus. Everyone involved with the study emphasizes repeatedly that the vaccine is notmade of a weakened or killed form of the virus, which means there is no chance that a volunteer can be infected with HIV by the vaccine. The three HIV genes used could not recombine to form an intact virus, and could not replicate to spread through the body.
The genetically engineered HIV genes are inserted in a disabled form of the common cold virus, which delivers them to cells in the human body. Those cells then manifest signs that they contain foreign proteins, triggering a response in the body's "Killer T" cells, the white blood cells that patrol the body looking for infections and attacking infected cells. Researchers hypothesize that the Merck vaccine will train Killer T cells to recognize HIV-infected cells so that if a real infection occurs, the body can mount an immediate shock-and-awe attack. "This is a completely new approach," says Jonathan Fuchs, director of vaccine trials at the city's Department of Public Health. "We're very excited about this particular product."
A small preliminary trial showed very promising results. Volunteers were given the vaccine, and 75 percent of participants had what the doctors call a "robust immune response"; blood tests revealed that those participants' Killer T cells recognized and responded to the HIV virus. That rate of success is on par with the rate of immune response in tests of the smallpox vaccine (one of the great success stories of modern medicine). Now, in this "proof of concept" study, researchers will learn whether that robust immune response will be enough to protect men like Trang from acquiring the virus.
There's one other possibility that the Step Study will test if the vaccine doesn't prevent infection, it might still teach the body how to fight the virus, and slow its spread through the body's cells. That raises the possibility that infected people might delay the need for antiviral drugs, and that they might live better, longer lives, as the body fights back naturally against the virus. Researchers hope to have the first answers to these questions in late 2007 or early 2008.
San Francisco is just one of 25 sites that are testing the Merck vaccine; other trials are ongoing throughout North and South America, the Caribbean, and Australia. Researchers hope to enroll a total of 3,000 volunteers around the globe, with other sites using heterosexual men or women as study subjects. San Francisco, with its complement of gay male test subjects, is leading the pack in recruitment with almost 100 volunteers so far, and public health officials are hoping to recruit another 50 before the end of the year.
The team advertises everywhere from the Bay Area Reporterto Craigslist. But Eduardo Lucio Villalon, another volunteer, has proven to be one of the most valuable advocates for the vaccine research team. Lucio Villalon and his partner have a nonmonogamous relationship, but he says they're both very careful. "We don't take risks, we don't take drugs," he says. The virus could get to them only if there's an accident, and a condom breaks.
The odds are good that Lucio Villalon's diligent precautions will protect him, and he won't be infected regardless of whether or not he has received the vaccine. But he's helping the study in another way, by serving as a very informal recruiter. First, he convinced his partner to sign up. Now, he promotes the study when he goes out on Saturday nights. "I try to tell my sex partners about it beforehand. I say, just so you know, I'm participating in this HIV vaccine study, and if you're HIV-negative, you should think about enrolling, too." So far, two casual sex partners have joined in.
"Whether it's going to be the vaccine or not, we will be participants in the effort to find a vaccine for HIV," Lucio Villalon says. Like other volunteers, he's proud to do his part, and hopes to bring the story of AIDS to a full circle: The epidemic exploded in San Francisco's bathhouses 25 years ago, and the greatest hope to end its spread might be discovered by the fellows dancing the night away at the End Up.