SA RESEARCHERS UNLOCK POSSIBLE KEY TO AIDS VACCINE

Two South African women may have helped unlock the key to a vaccine to rid the world of one its deadliest epidemics, according to new research released by South African HIV experts.

In 2005, an HIV-negative woman from the city of Durban enrolled in a study of acute HIV infection conducted by the Centre for the AIDS Programme of Research in South Africa (CAPRISA). Two years later, another HIV-negative woman in her early 20s, living in the rural township of Vulindlela, joined CAPRISA’s ground-breaking trial of the efficacy of an antiretroviral-based vaginal microbicide to prevent HIV infection. 

Both women eventually contracted the virus and were placed on treatment. However, because they were part of large-scale clinical trials, researchers were able to follow them for years, discovering in the process that their bodies produce rare antibodies found in only one out of every five HIV patients, according to research published in the 21 October online edition of the journal Nature Medicine.

Antibodies

Everyone with HIV produces antibodies to the virus, but in most people these antibodies react only to the particular strain of HIV acquired. Wide variation in strains of HIV, caused by the virus’s ability to mutate, has been the biggest roadblock to vaccine development.

“HIV mutates incredibly fast, more so than perhaps any other virus,” lead researcher Penny Moore told IRIN/PlusNews. “The virus that infects one person is very different from the virus that infects another.”

The women studied by CAPRISA, however, produced what are called “broadly neutralizing antibodies”, which can kill a wide range of HIV types across different individuals, overcoming regional variations in the virus. Antibodies taken from these women killed up to 88 percent of all types of HIV found worldwide, according to the study.

While broadly neutralizing antibodies were discovered three years ago, CAPRISA’s research is the first to uncover at least one way in which these antibodies work.

According to the study, the virus formed a layer of sugars to protect itself from the common, strain-specific antibodies of the two women. However, this layer of sugar proved to be what Moore calls the virus’s “Achilles heel.” The women were then able to produce broadly neutralizing antibodies that targeted and bonded with specific sugars, blocking the virus from infecting healthy cells.

According to CAPRISA director Salim Abdool Karim, these antibodies could be the key to developing an HIV vaccine.

“The holy grail of HIV prevention is a safe, effective HIV vaccine,” he told IRIN/PlusNews. “This discovery provides new clues on how vaccines could be designed to elicit broadly neutralizing antibodies.”

Researchers caution that a vaccine based on these antibodies is still years away and may come to consist of a series of different vaccines mimicking HIV infection, its progression and the body’s response. “[We’d want to see] if we could trick immune system to go through the same arms race it went through in these two women, without HIV infection,” Moore said.

The study was co-funded by the US government and South Africa’s Ministry of Science and Technology. While the South African government has not decided to patent this discovery, it is in the process of securing patents on CAPRISA’s tenofovir-based microbicide. If the microbicide is successful in follow-up trials, the government plans to begin local production of its active ingredient to ensure affordability and reduce dependence on foreign importers.

A legacy

At the Johannesburg launch of the research, South African Health Minister Aaron Motsoaledi congratulated researchers and acknowledged the women’s contributions.

“I wish to thank these women for allowing their experiences to be studied for the benefit of all us,” he told IRIN/PlusNews. “Sometimes, we forget about [study participants], but I think they are also scientists in one way or another. Without contributions like theirs, even the best idea cannot be tested.”

Unfortunately, the women’s antibodies have not delayed disease progression. One woman is doing well with HIV treatment, living with her partner and HIV-negative children in Durban. But the woman from Vulindlela died of extensively drug-resistant tuberculosis (XDR-TB) about a year ago, according to Karim, whose team hospitalized her for treatment.

XDR-TB is resistant to the most commonly used first-line TB drugs and at least half of the mostly commonly used second-line drugs. TB is the leading killer of HIV-positive people globally, and is one of South Africa’s leading causes of death.

“Such are the challenges we deal with on a daily basis in our country with HIV patients,” said Karim. “But her specimens, her virus, continue to inform our work and enable us to understand [HIV] so, in many ways, she’s left a lasting legacy.”

“Of the 34 million people living with HIV globally, two-thirds are in sub-Saharan Africa,” he added. “This is an African problem and… it’s unlikely that we’ll be able to eradicate this epidemic without a vaccine.”