Researchers have struggled over the years to find a cure for AIDS, and while an effective HIV vaccine has eluded them thus far they are still making progress. But now new research finds that llamas, of all things, may hold the key to combating this fatal disease.
Specifically, a combination of antibodies from llamas can destroy - or neutralize - a wide range of circulating HIV viruses, researchers reported in the journal PLOS Pathogens.
Antibodies in most mammals are relatively large proteins, and scientists surmise that this bulkiness is why neutralizing antibodies are so rare. Not to mention that the CD4 receptor on virus cells that most developing vaccines target is exceptionally narrow. However, llamas are the exception to the rule. These pack animals produce the four-chain antibodies common among all mammals, but they also produce smaller ones made up of only two of the four chains, making them less cumbersome.
During the study, Laura McCoy led an international team of researchers in testing the immune response in llamas against HIV, which causes AIDS. Previous research had identified one particular HIV neutralizing llama antibody, and in this new study a total of three new neutralizing antibodies were found. And while separately the four virus-destroying antibodies target different parts of HIV's CD4-binding site, together they are more effective.
A combination of these antibodies, rather than interfering with each other, successfully neutralized all of the 60 different HIV strains tested.
To better understand how llamas hold the key to fighting the virus, McCoy and her colleagues sequenced several copies of their antibody-coding genes from blood cells, which they collected after the first set of immunizations and after a further four rounds of vaccination. They also looked at these same genes in seven of the llamas that weren't vaccinated.
To their surprise, the neutralizing antibodies were generated as immune cells repeatedly encountered the vaccine and responded by maturing specific antibodies that can recognize and target it.
And while these results are encouraging in the fight against AIDS, unfortunately these antibodies are only present at low concentrations in the blood, and so don't qualify as a protective HIV vaccine.
Nonetheless, "our results show that immunization can induce potent and broadly neutralizing antibodies in llamas with features similar to human antibodies and provide a framework to analyze the effectiveness of immunization protocols," the authors wrote.
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