Stanford researchers share their progress at International AIDS Conference
Use of generic drugs among topics discussed in Bangkok
BY MITZI BAKER
New methods of detecting and treating HIV/AIDS were among the topics discussed by researchers at the School of Medicine during the 15th International AIDS Conference last week in Bangkok. They were among the 15,000 participants who discussed the challenges the world faces in trying to halt the spread of the disease. Following are summaries of four topics presented by Stanford scientists.
Detecting HIV in breast milk
Researchers David Katzenstein and Yvonne (Bonnie) Maldonado have found two effective methods of testing breast milk for the presence of HIV, offering hope in the effort to stem the tide of mother-to-child transmission of the virus.
More than 90 percent of the 1 million children infected annually by HIV receive the virus from their mothers. Where breastfeeding is the norm, breast milk accounts for more than one-third of all transmissions.
Katzenstein and Maldonado tried two techniques never before used to detect HIV in breast milk. One method, the polymerase chain reaction or PCR, has been used for years to detect HIV in blood. The second technique was branched DNA signal amplification, a newly approved method of directly detecting the level of HIV in the blood. The researchers found that both methods work, but that PCR was more sensitive.
“We wanted to see if we could use cutting-edge, Silicon Valley technology and apply it to Africa to reduce the transmission of HIV from mother to child,” said Katzenstein, MD, associate professor of infectious diseases and geographic medicine.
He and Maldonado, MD, associate professor of pediatrics and director of Stanford’s pediatric AIDS program, are working on a larger study in which at-risk babies are given the drug nevirapine and breastfed for only six months. In a pilot study, this approach reduced the transmission rate to less than 1 percent.
Use of generic antiretroviral drugs
Generic antiretroviral AIDS medications are a viable therapy for patients who previously have taken short courses of other drugs, according to a study by researchers from Stanford, Zimbabwe and Spain.
Generic antiretrovirals, which cost much less than their brand-name counterparts, could make it easier for larger numbers of patients to receive the medications in developing countries. Also, as short-course therapies become more common – for instance, to reduce mother-to-child transmission – researchers need to know if these brief therapies affect future response to the full highly active antiretroviral therapy, known as HAART.
“There is still a paradox between drugs available and accessible,” said Katzenstein, who led the study. “Generic drugs are not recognized by the FDA and the U.S. government as acceptable.”
Katzenstein’s team started 29 patients on a generic form of HAART after the patients had already taken either a single dose of nevirapine or a short course of AZT. After 16 weeks, the researchers found that pre-exposure to the other single therapies did not appear to influence the positive response to HAART.
Interrupting antiretroviral therapy
Can HIV-positive patients go on and off treatment without aggravating their condition? Researchers found that half the patients in a small study were able to live medication-free for more than a year without developing AIDS-related illnesses.
The idea of “pulsed therapy,” or going on and off treatment, is an intriguing one. If half the drugs could still provide patients with a healthy quality of life, then twice as many people could be treated for the same cost while being exposed to fewer toxic side effects from the drugs.
The Stanford AIDS Clinical Trials Group interrupted the therapy of 47 HIV-positive patients who had just taken their first round of potent antiretroviral therapy. During the initial round of therapy, half of the patients were also given IL-2, a drug that helps the body produce immune cells that fight the virus.
The researchers found that although the viral counts went up after the interruption of treatment, at least half of the patients were able to remain off the therapy for more than a year, with their immune-cell levels remaining at acceptable levels and no AIDS-related illnesses developing. The IL-2, which can be expensive, did not provide any lasting benefits to this strategy.
“Very few studies have asked how long it is safe to stay off the drug,” Katzenstein said. “This study was much more realistic about how to spare drug over time.”
Database for differentiating HIV subtypes
A new database containing HIV sequences from infected patients throughout the world will help researchers and physicians decipher the differences between the various subtypes of the virus and determine which drugs will be most effective at treating each subtype.
Most knowledge of HIV drugs is based on subtype B, which is most prevalent in North America, western Europe and Australia. However, the majority of people with HIV are infected with non-B subtypes. Researchers need to know whether data gathered for subtype B applies to the other subtypes.
Katzenstein, along with researchers Robert Shafer and Rami Kantor, spearheaded an international collaboration of 12 countries to collect and analyze HIV sequences from people infected with non-B subtypes to tease apart the differences. Knowing the sequence of HIV that a person is carrying can determine which drugs will be most effective.
The group has compiled the largest data set that includes all of the known subtypes. The data is intended to be publicly available via the Internet to serve as a reference and as a watch list for resistance-surveillance programs and epidemiological studies.
“We are putting this data together so that if someone anywhere in the world could upload one sequence, they could immediately view it in the context of all the other sequences,” said Shafer, MD, assistant professor of infectious diseases and geographic medicine.
So far, the group has found that most of the resistance mutations seen in subtype B also exist for non-B – giving reassurance of the effectiveness of treatments that have already been developed, said Kantor, MD, research fellow in infectious diseases and geographic medicine.