Kaisernetwork.org (Washington, DC)
25 March 2008
Science & Medicine
Trials of NIH HIV Vaccine Candidate Scaled Down After Failure of Merck Vaccine
[Mar 25, 2008]
Trials of NIH's Vaccine Research Center's HIV vaccine candidate will be scaled down after the recent failure of a Merck HIV vaccine candidate, Bloomberg reports (Lauerman, Bloomberg, 3/24). Merck in September 2007 announced it had halted a large-scale clinical trial of its experimental HIV vaccine after the drug failed to prevent HIV infection in participants or prove effective in delaying the progression of the virus to AIDS. The vaccine candidate also might have put some trial participants at an increased risk of HIV (Kaiser Daily HIV/AIDS Report, 3/21).
The VRC candidate, called PAVE-100, is similar to the Merck vaccine in that both stimulate CD4+ T cells against HIV and both contain the cold virus adenovirus-5. Researchers in the Merck trial found that men who received that vaccine were at an increased risk of contracting HIV if they had a high immunity to adenovirus-5 when they enrolled in the trial. Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases, said that the VRC trial will not enroll anyone with high immunity to the cold virus. According to Bloomberg, this could rule out nine in every 10 potential study participants in Africa. In addition, the trial will require that men be circumcised, according to Wayne Koff, senior vice president for research and development at the International AIDS Vaccine Initiative.
VRC initially planned to enroll 8,500 people in the U.S. and Africa in the trial but now plans to enroll only 2,000. In addition, IAVI on Monday announced plans to pull out of the VRC trial. Koff said the group had planned to enroll 1,000 people in Africa in the new trial but pulled out because it believes that human trials of HIV vaccine candidates should be small and aim to design better vaccine candidates than those currently in development. Koff said that there is not a "clear understanding of why" the Merck trial failed, adding that IAVI believes there is "a safety unknown" in the new VRC trial.
The new vaccine has features that could make it more effective than the Merck vaccine, according to Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition. PAVE-100 uses DNA that researchers hope will induce cells to produce vaccine-like proteins to generate a protective immune response against HIV. Researchers also are hoping that the cold virus in PAVE-100 will cause a stronger immune response than the cold virus in the Merck vaccine. According to Warren, HIV vaccine trials in the immediate future should focus on answering questions about how such vaccines work as opposed to whether they can prevent HIV transmission. He added that there is "certainly something to learn by advancing PAVE-100."
According to Bloomberg, some researchers have said that the failure of the Merck vaccine has set back HIV vaccine research for years, and many researchers are questioning new trials. The AIDS Healthcare Foundation recently called for all HIV vaccine research to be stopped. NIAID on Tuesday is expected to hold a meeting with HIV/AIDS researchers to discuss its $497 million HIV vaccine research program. Bruce Walker, a researcher at Harvard Medical School, said the NIAID meeting will aim "to stop and take stock" of HIV vaccine development following the "unanticipated result" of the Merck trials (Bloomberg, 3/24).
Link to this story.
Genetic Variations Might Be Causing Mutations to HIV, Making It Less Potent, Study Says
[Mar 25, 2008]
Genetic variations that might help people newly diagnosed with HIV control their viral loads also could be causing a mutation in the virus that makes it less potent, according to a study published Friday in PLoS Pathogens, Reuters reports.
Some people have versions of an immune system gene, called HLA, that are "known to force HIV to tolerate mutations that damage its ability to reproduce," according to Carolyn Williamson of the Centre for the AIDS Programme of Research in South Africa and colleagues. The weakened virus also means lower viral loads and slower disease progression in people with beneficial versions of HLA, according to Reuters. The researchers found that the weakened virus might be transmitted to and act in the same way in other people, even if they do not have the HLA variation, Williamson said.
The researchers followed 21 women in South Africa who recently contracted a weakened strain of HIV. The women did not have the beneficial HLA variation, according to Reuters. The researchers followed the women for between one to three years, Reuters reports. The researchers found the women had much lower viral loads, compared with people carrying a strain of HIV that had not mutated to a weakened state. The researchers also found that while the women's viral loads decreased, their CD4+ T cell counts increased. "It is pretty well established if you have certain HLA genes, you are better off," Williamson said, adding, "It is very likely that the virus in the people who did not have the HLA gene came from individuals who did."
According to Williamson, the "significant difference to other studies is that this is showing the actual benefit is due to the genetic composition of the virus." She added that the findings show "a survival advantage with a virus containing specific genetic signatures associated with lower replication."
The researchers have not studied the women to see how much slower they progress to AIDS but noted the findings could help researchers looking for an effective vaccine through an improved understanding of why some people living with the virus survive longer (Kahn, Reuters, 3/20).
The study is available online.
Link to this story.
Politics and Policy
Houston Chronicle Examines U.S. HIV/AIDS-Related Travel Restrictions
[Mar 25, 2008]
The Houston Chronicle on Sunday examined U.S. HIV/AIDS-related travel restrictions for visitors and immigrants. According to the Chronicle, the U.S. is one of 13 countries -- including Armenia, Iraq and Qatar -- that has such restrictions (Carroll, Houston Chronicle, 3/23). A regulation included in a 1993 amendment to the Immigration and Nationality Act only permits HIV-positive foreigners to obtain visas to enter the U.S. under limited circumstances. The regulation also requires HIV-positive foreigners to obtain waivers from the Department of Homeland Security before they can receive visas.
Draft rules proposed by the Homeland Security Department that would change U.S. HIV-related travel rules have not been finalized. Some advocates and Democrats have objected to the proposed rules, saying that the rules do not improve the situation (Kaiser Daily HIV/AIDS Report, 3/12).
The Senate Foreign Relations Committee earlier this month approved a President's Emergency Plan for AIDS Relief reauthorization bill (S 2731), which includes a provision that would lift some of the travel restrictions, the Chronicle reports. Rep. Barbara Lee (D-Calif.) has sponsored a House version of the amendment.
Although the provision is attached to the PEPFAR reauthorization bill, supporters are cautiously optimistic, the Chronicle reports. If the provision is approved, HHS will then need to decide whether HIV/AIDS should remain on a list of diseases preventing entry into the country, according to the Chronicle. HHS officials did not return calls seeking comment on the issue.
According to the State Department, 938 immigration applicants were denied admission to the U.S. in 2007 because of a communicable disease; however, 478 of the applicants later received waivers and were permitted entry. A breakdown of the applicants' diseases was not available, according to Steven Royster, a State Department spokesperson. According to the Chronicle, the U.S. requires HIV tests only for people who plan to immigrate permanently, but short-term visitors are asked whether they have a communicable disease during the visa application process.
Supporters of the amendment have said a repeal of the travel ban is overdue. "There is no scientific basis whatsoever for the travel ban, and there never has been," Mark Kline, head of retrovirology at Baylor College of Medicine and director of the school's AIDS International Training and Research Program, said. He added that the travel ban was a "political decision." In addition, the ban has led to a U.S. boycott by some HIV/AIDS advocacy and research groups, and International AIDS Society conferences have not been held in the U.S. since Congress passed the travel restrictions.
Be the first to Write a Comment!
AllAfrica aggregates and indexes content from over 125 African news organizations, plus more than 200 other sources, who are responsible for their own reporting and views. Articles and commentaries that identify allAfrica.com as the publisher are produced or commissioned by AllAfrica.
