For years scientists have grappled with the challenge of how to develop a vaccine for AIDS.  On September 3, researchers came one step closer to attaining this goal. Scientists have found two antibodies that may be the keys to developing an HIV vaccine.

HIV is a virus that mutates rapidly with many different forms, or “strains,” infecting people worldwide. Since it is always changing, researchers have experienced difficulty in developing a vaccine that can work against its various strains. The newly discovered antibodies are known as broadly neutralizing antibodies because they have the ability to target many different strains of HIV.

Antibodies are protein molecules manufactured by the body’s immune system to mark and neutralize pathogens in the body for destruction. Pathogens are agents such as bacteria, fungi, and viruses that cause disease. Antibodies detect pathogens by identifying molecules on the surface of the invading species.  These surface molecules on pathogens are known as antigens. Normally, an antibody can only bond to one specific antigen.

In this case, the two broadly neutralizing antibodies correspond to an antigen known as viral glycoprotein gp120, which is an antigen that seems to remain the same even as HIV mutates. Previously, scientists had overlooked this antigen as a possible breach in HIV’s defense system.

In order to find these broadly neutralizing antibodies, which are developed within some HIV-positive people over time, researchers screened serum from 1,800 HIV-positive people from Thailand, Australia, United Kingdom, United States, and a number of sub-Saharan African countries. During the study, the first antibody (known as PG9) neutralized 127 of 162 viruses, and the second antibody (known as PG16) neutralized 119 of 162 viruses. Moreover, PG9 and PG16 were exceedingly more potent than the four control antibodies that were used.

The broad neutralizing capabilities of the PG9 and PG16 antibodies indicate that a future vaccine may provide protection against many different strains of HIV. Before a vaccine can be developed, however, researchers will closely study the molecular structure of the antibodies and will also examine how they bind to the virus. After this, researchers can work towards developing a vaccine that may hold the key to fighting HIV.

For more information, please see the study in Science (abstract).