Antibodies that recognise HIV and prevent it from infecting cells are a crucial element of immunity to the virus, but so far researchers have not been able to achieve this with vaccines. This is partly because the virus is highly skilled at escaping from antibodies by changing the appearance of its outer coating.
It has been known for some time that some HIV-infected people naturally develop antibodies that recognise many different types of the virus. Over the past five years, researchers from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) have been studying HIV-infected people to understand the mechanism behind how these individuals are able to generate such broadly neutralising antibodies.
The team focused on two women in particular and found that their antibodies recognised a specific feature of the outer coat of the virus that was not present in the virus that they were initially infected with. The virus seemed to have changed its coat in response to antibodies that were produced earlier in the infection to try to escape immune attack; however, this shift revealed a vulnerability that enabled the women to produce more powerful antibodies that are capable of killing many different HIV types from around the world.
Dr Penny Moore, a Wellcome Trust Intermediate Fellow in Public Health and Tropical Medicine and lead author of the study, said: “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 neutralising antibodies arise.”
Professor Salim Abdool Karim, Director of CAPRISA, said: “Broadly neutralising antibodies are considered to be the key to making an AIDS vaccine. This discovery provides new clues on how vaccines could be designed to elicit broadly neutralising antibodies.”
The study was published this week in the journal ‘Nature Medicine’.
Image: A glass sculpture of HIV. Credit: Luke Jerram.
Moore PL et al. Evolution of an HIV glycan-dependent broadly neutralising antibody epitope through immune escape. Nat Med 2012 (epub ahead of print).