A step towards developing an HIV vaccine
Cows can save humanity from HIV, scientists say
Injection of "dummies" of the immunodeficiency virus forced the immunity of cows to develop a whole set of antibodies neutralizing 96% of HIV varieties, which opens the way for the creation of a vaccine against this virus, according to an article published in the journal Nature (Sok et al., Rapid elicitation of broadly neutralizing antibodies to HIV by immunization in cows).
"The unusually strong immune response of cows to viral particles was a very surprising thing for us, given how little time they needed to produce universal antibodies. Unlike their human counterparts, cow antibodies were more often arranged in a unique way and coped better with even the most complex "dummies" of the virus," says Dennis Burton from the Scripps Research Institute in La Jolla (in a press release, NIH–supported scientists elicit broadly neutralizing antibodies to HIV in calves – VM).
The immunodeficiency virus penetrates into human cells using a set of several proteins on the surface of its shell. Their structure and the structure of the hydrocarbon "shield" protecting them changes with each new generation of HIV, which forces the immune system to produce a new set of antibodies. In the overwhelming majority of cases, the virus becomes the winner in this "arms race", and the same feature prevents scientists from creating a vaccine or vaccination against HIV.
As immunologists explain, 3-4 years after HIV infection, the human immune system often begins to synthesize so-called broad-spectrum antibodies (broadly neutralizing antibodies, bNAbs), capable of neutralizing several varieties of the virus at once. This does not help the body much, since by this time the virus will already have time to penetrate deeply into all the tissues of the body and go into the chronic stage.
Burton and a number of other virologists have long been trying to "transplant" this process into uninfected animal cells, adapting them for mass production of a large set of bNAbs, and creating a vaccine that can train the immune system to fight all types of HIV before infection occurs.
Interaction of one of the bNAbs with the HIV envelope (Scharf et al., 2015) – VM.
As Burton notes, past experiments that scientists conducted on mice with a "human" immune system and ordinary monkeys ended in failure, and therefore scientists began to look for other methods of creating vaccines that force the body to produce "universal" antibodies to HIV.
In parallel, virologists tested how the immune systems of other animals, rarely used in experiments, would react to injections of the HIV "dummy" created by them, consisting of analogues of the Env protein, the basis of the immunodeficiency virus envelope.
Conducting similar experiments on calves, Burton and his colleagues noticed that their bodies began to produce bNAbs literally 1-2 months after the start of injections. After studying their structure, scientists came to the conclusion that some of these antibodies combined with HIV no worse than the highest-quality human bNAbs do. The best of them, NC-Cow 1, can single-handedly destroy about 70% of the known varieties of the immunodeficiency virus.
A set of such antibodies, which scientists have grown in cows for a year, was able to neutralize about 96% of HIV strains, which is a big step forward in the development of a vaccine against the main disease of the 20th and 21st centuries.
Why did the immunity of calves cope with this task better than the body of humans, mice and monkeys? According to scientists, this is due to two things – the fact that it does not look like our immune system, and the fact that cows constantly have to fight infections when digesting food and protect their intestines from the penetration of microflora microbes into body tissues.
These differences, for example, may explain why some chains of amino acids critical for HIV neutralization are noticeably longer in cow antibodies than in their human counterparts. Further experiments with animals and antibodies, scientists hope, will help us understand how human immunity can be made to work in a similar way, and how cow antibodies can be made safe for medical use.
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21.07.2017