Who knew the secret to developing an HIV vaccine would be lying in the immune system of a cow?

“From the early days of the epidemic, we have recognized that HIV is very good at evading immunity, so exceptional immune systems that naturally produce broadly neutralizing antibodies to HIV are of great interest — whether they belong to humans or cattle,” Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, told BBC News this week.

Fauci’s comments came in response to recent research conducted by the International AIDS Vaccine Initiative and the Scripps Research Institute in which they tested an HIV vaccine on cows, revealing surprising and promising results.

One of the biggest challenges of combating HIV is its ability to mutate every time a person’s immune system finds a way of attacking the virus. Despite this, a small number of people living with the virus eventually develop “broadly neutralizing antibodies” after years of infection. These antibodies attack parts of the virus that it cannot mutate.

It's believed that a vaccine that could train the immune system to make broadly neutralizing antibodies would help prevent people from contracting the virus.

For the first time in immunization research, cows were able to rapidly produce this special type of antibody that neutralizes HIV. Researchers now suggest that cows possess evolved immune systems due to their complex, bacteria-packed digestive system.

The results, published in the science journal Nature, showed the cow’s antibodies could neutralize 20 percent of HIV strains within 42 days. By 381 days, they could neutralize 96 percent of strains tested in the lab. The U.S. National Institutes of Health said the findings were of “great interest.”

“The potent responses in this study are remarkable,” said Dr. Dennis Burton, a researcher on the project. “Unlike human antibodies, cattle antibodies are more likely to bear unique features and gain an edge over HIV.”

Dr. Devin Sok, another researcher on the project, agrees. “The response blew our minds,” Sok told BBC. “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,” said Sok. “Who would have thought cow biology was making a significant contribution to HIV.”