Unique HIV feature might be key to new vaccine strategies — study

A recent discovery in South Africa could herald a new approach to combating HIV and AIDS and creating an AIDS vaccine.

A “unique change” in the outer covering of the human immunodeficiency virus found in two HIV-positive women enabled them to generate antibodies that can kill up to 88 percent of HIV types from around the globe, the science news website Science Daily reported.

The discovery was made during a study conducted by members of the Center for AIDS Program of Research in South Africa (CAPRISA) consortium, including scientists from Wits University, the National Institute for Communicable Diseases (NICD) in Johannesburg, University of Kwa Zulu-Natal, and the University of Cape Town.

It was the CAPRISA team who discovered the women, from South Africa’s KwaZulu-Natal province, who could make these rare antibodies.

According to Science Daily, Wits and NICD researchers Dr. Penny Moore and Professor Lunn Morris discovered that glycan, a type of sugar, on the protein coat of the virus at a specific position forms a “site of vulnerability” in the virus and “enables the body to mount a broadly neutralizing antibody response.”

It is a significant discovery, as “HIV is an especially tricky virus for vaccine developers,” said The Scientist magazine, as “HIV’s rapidly mutating genome allows it to evade immune attack by changing its appearance, preventing recognition by initially effective antibodies.”

“Understanding this elaborate game of ‘cat and mouse’ between HIV and the immune response of the infected person has provided valuable insights into how broadly neutralizing antibodies arise,” Moore said.

“We had always assumed the first virus would be special,” University of Amsterdam immunologist Hanneke Schujtemaker told The Scientist, but added that the new study now challenges this assumption.

“We were surprised to find that the virus that caused infection in many cases did not have this antibody target on its outer covering,” said Morris.

“But over time, the virus was pressured by [the] body’s immune reaction to cover itself with the sugar that formed a point of vulnerability, and so allowed the development of antibodies that hit that weak spot,” he added.

The hunt for the most effective vaccine

Scientists have long believed that “broadly neutralizing antibodies” (which defend a cell from an infectious body by neutralizing any effect it has biologically) are the key to making the perfect AIDS vaccine.

“This discovery provides new clues on how vaccines could be designed to elicit broadly neutralizing antibodies. The world needs an effective AIDS vaccine to overcome the global scourge of AIDS,” said CAPRISA director Prof. Salim Abdool Karim.

Even if the existence of these types of antibodies has been known for a while, broadly neutralizing antibodies against HIV were only identified three years ago.

The new study found one mechanism by which these antibodies can be made.

According to the Science Daily Report, the research team had to study the target of some of these antibodies, glycan, to form a site of vulnerability. “By tracing back the evolution of the virus that elicited these antibodies, this team showed that this particular weak point was absent from the virus that first infected these women,” the report said.

“[U]nder constant pressure from other less powerful antibodies that develop in all infected people, their HIV was forced to expose this vulnerability over time. This allowed the broadly neutralizing antibodies to develop,” it added.

Moore told The Scientist magazine, “This is the first time we’ve really understood that viral evolution itself shapes the antibodies that come out.”

“Being able to work out the pattern of viral evolution will help us think about designing vaccines,” she added.

Moore also told The Scientist magazine that one strategy that may prove successful could be to provide sequential immunizations with vaccines containing different epitopes (parts of antigens, which create antibodies) “mimicking what happens naturally” as the viruses evolve.

HIV in the Philippines

In a conference on Oct. 18, the Department of Health (DOH) reported that between 1984 and 2012, the Philippines recorded 10,514 cases of HIV, with 353 deaths.

The DOH also noted that the majority of these cases involved individuals aged 15 to 24.

According to the Department, more than half of the cases were identified only in the last three years. — BM, GMA News