Cow antibodies may be key to effective AIDS vaccine

Barsaba Taglieri
Luglio 21, 2017

In the last few years, researchers have discovered that broadly neutralizing antibodies against HIV tended to be large, unruly proteins.

In people infected with HIV who develop broadly neutralizing antibodies, this antibody region - called HCDR3 - has about 30 amino acids, about twice as long as what is usual for human antibodies.

Scientists may be one step closer to developing a cure for HIV, new research suggests.

Scientists working on HIV vaccine development could use these findings try and promote human immune system's development of long HCDR3 loops.

FLICKR, LESZEK LESZCZYNSKIScientists have long sought an HIV vaccine that would elicit the production of broadly neutralizing antibodies, which are thought to be key to stopping a wide range of viral strains.

This is when researchers at the International Aids Vaccine Initiative and the Scripps Research Institute tried immunising cows.

"The response blew our minds", Dr Devin Sok, one of the researchers, told the BBC News website.

In the study now published in the journal Nature, scientists have worked with cattle, as they hoped that their immune system - which has unique features - would react strongly to HIV immunogens (proteins created to mimic the surface of the virus).

Dr Sok added: "It was just insane how good it looked, in humans it takes three-to-five years to develop the antibodies we're talking about".

"This is really important because we hadn't been able to do it period".

Smider and colleagues took serum - blood with the cells removed, leaving antibodies behind - from four immunized cows and tested it against different types of HIV virus in a test tube.

All four animals appeared to develop broadly neutralising antibodies quite quickly after immunisation, 35 to 50 days later. "The unresolved challenge is how to make humans respond more like cows", said Robin Shattock, Head of Mucosal Infection and Immunity at Imperial College London, who was not involved with the study. "Unlike human antibodies, cattle antibodies are more likely to bear unique features and gain an edge over complicated HIV immunogens".

Unusually for human antibodies, the broadly neutralising ones have a long and loopy structure.

"Less convincing is the potential use of cow antibodies for treatment - humans would recognise these as foreign and so make a response against the antibody itself". Cattle and other ruminant animals have multi-chambered stomachs and a robust population of bacteria in their digestive tracts to help break down a diet of tough grasses. However, these bacteria can pose an infection risk if they escape the gut, so cattle with a versatile mechanism for producing potent antibodies would greatly benefit from the increased protection. "It might be possible to use cow antibodies externally - applied to mucosal surfaces - oral, vaginal, rectal to prevent HIV, but there are now better strategies that are already available - such as pre-exposure prophylaxis", Shattock said.

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