Important note: Information in this article was accurate in 2005. The state of the art may have changed since the publication date.
Bay Area Reporter - October 6, 2005
Matthew S. Bajko, m.bajko@ebar.com
The vaccine uses a weakened cold virus, adenovirus 5 (ad5), which can neither reproduce itself nor give a person a cold, to deliver synthetic genetic information about HIV to the body's immune system, with the hope of training a person's immune system to fight off HIV if he is ever exposed. A person cannot acquire HIV from the vaccine.
While it remains to be seen if the vaccine, called MRKAd5, will prove to be an effective tool against HIV, researchers have discovered that it produces a stronger-than-expected immune response in those people who have antibodies to the cold virus. Due to the findings, researchers are now doubling enrollment in the vaccine trial to 3,000 people throughout North and South America, the Caribbean, and Australia.
In San Francisco, researchers are focusing on gay and bisexual men, and now are recruiting 100 men for the study. To date, 31 men have enrolled in the Step study. The Wall Street Journal first reported on the findings and expansion of the vaccine trial September 23.
"In past Merck studies, people who had this type of cold didn't have a strong response to the vaccine. Initially, the Step study was designed just for people who were never exposed to this type of cold. If people already have an immune response to this cold, they might fight off the vaccine before it gets to train the immune system," said Susan Buchbinder, the lead investigator for the San Francisco leg of the trial. "What these earlier studies of this vaccine showed is that even people who had high antibodies against the vaccine are still generating a strong immune response. It is good news; it may protect a broader population than we had initially hoped for."
The Step study is the first vaccine to progress to an efficacy trial in the U.S. in years. It is looking to see if the immune response in HIV-negative people given the vaccine will help them to remain negative, or if they become HIV-positive, remain healthy for a longer period of time. Some people receive a placebo, while others the vaccine.
"We don't know yet if that immune response will protect people. Scientists think this immune response is what we need but we don't know if that is true or is enough to protect people," said Buchbinder. "This vaccine is the first vaccine to generate this type of immune response. I think what is really exciting about the Step study is this is the most promising vaccine we have had to date."
Despite the controversies surrounding other trials, such as the failed Vaxgen study and Tenofovir, a once-a-day pill that may prevent HIV, the Step study has been positively received. It is also testing the reach of Internet marketing in finding study volunteers. San Francisco-based ISIS, the Internet Sexuality Information Services company, produced bus ads that went up last month and developed the Web site www.SFisready.org to help recruit people for the trial.
"It is the first time we have used a Web site for vaccine trial recruitment. The community has been responding very well," said Tom Kennedy, ISIS director of health communications.
From learning about the vaccine trial for his work, Kennedy, 39, decided to become a participant and joined the Step study in June. It is his first time enrolling in such a trial.
"I've been terrified by the AIDS epidemic my whole life. I've managed to stay negative through a lot of hard work and a lot of good luck," he said. "Yet this is another way I thought I could make a contribution for our community in hopes this would be the HIV vaccine that would work or in hopes whatever information comes out of this trial leads to an effective preventive vaccine."
He has had two injections so far, with no negative side effects, said Kennedy, who does not know if he is receiving the placebo or the vaccine.
"At this point I am not worried," he said.
Nor has he changed his behavior or belief in the need to practice safe sex due to becoming a study participant, said Kennedy.
"I don't know if it works or not, so no, it has not changed my behavior. I am still safe," he said.
Results from the Step Study will not be known until 2008, at the earliest. Anyone interested in joining the study can call (415) 554-9068.
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