Scientists may be one step closer to developing a cure for HIV, new research suggests.
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.
'Unlike human antibodies, cattle antibodies are more likely to bear unique features and gain an edge over HIV'.
Dr Burton, a lead author on the study and director of the NIH's Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery commented "A minority of people living with HIV produce bNAbs, but only after a significant period of infection, at which point virus in their body has already evolved to resist these defenses". In a first for any animal, including humans, four cows injected with a type of HIV protein rapidly produced powerful antibodies against the virus, researchers report.
The study was carried out by researchers at the International Aids Vaccine Initiative and the Scripps Research Institute.
Previous studies showed that cattle antibodies also feature extra-long loops that might access hard to reach epitopes where human antibodies can not.
When infected with the HIV virus, humans can not produce the required antibodies to kill it, which is why the HIV vaccine has been a challenge to develop.
The virus uses fences of sugars on its surface to protect vulnerable sites, and only antibodies with long "arm-like loops" are able to circumvent this barrier and get in.
Researchers immunized cows with an immunogen known as BG505 SOSIP, which closely mimics the protein target. Immunization with this immunogen in macaques, guinea pigs, and rabbits was both encouraging and discouraging - it has elicited very good antibodies against one strain of the virus, but failed to elicit antibodies capable of overcoming HIV's global diversity - until now.
An unlikely hero has emerged in the quest to fight HIV: the cow. In comparison, it takes HIV-positive humans multiple years to develop comparable responses, and only 5-15 per cent even develop them at all. But these findings illuminate a new goal for HIV vaccine researchers: by increasing the number of human antibodies with long loops, we might have an easier chance of eliciting protective bnAbs by vaccination. "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.
Of course cows can not be infected with HIV, but the results of the study did confirm the team's speculation that the long-arm loops are key.
"Scientific innovations like this are what propel the field forward", said IAVI CEO Mark Feinberg. For the small percentage of people estimated to develop these antibodies after a natural infection, it can take several years.