Remote Amazon tribe found to naturally produce antibodies against the rabies virus

Some people from a remote tribe in the Amazon rainforest naturally produce antibodies against the rabies virus, a discovery which has baffled researchers.

It was previously thought that developing an antibody to the rabies virus would be impossible without vaccination. However, blood samples from 63 people in Peru revealed that seven of them were found to have antibodies that could fight a rabies infection. Only one of these had been given a rabies vaccine, with the other six presenting a medical mystery to the researchers.

Around 55,000 people worldwide die from rabies each year, and it is fatal to nearly everyone who doesn’t get vaccinated after exposure. Lead study researcher Amy Gilbert, a researcher for the Centers for Disease Control and Prevention said: "By and large, most folks have not presumed that humans provide an antibody response to clear the virus.

"If you were going to look for such a thing… this is where you would find it."

There is a high incidence of rabies in the Amazon rainforest, and researchers were in the area to better understand the disease. Peru has many infected vampire bats, which have bites so sharp, yet so small, that the person who gets bitten may not even realise it.

One hypothesis on the unusual results is that some of the people trialled could have developed immunity by receiving tiny amounts of the rabies virus from bat bites, never becoming so severely infected that their central nervous systems were affected. Dr Bruce Hirsch, who researches infectious diseases at North Shore University Hospital in Manhasset, US, believes the antibodies could be a result of such "abortive infections," which happen when a virus enters the body but dies before multiplying significantly.

An infection such as this may be able to function as a vaccine does, in that people are infected with a harmless form of the virus which prompts an immune response that creates protective antibodies against the stronger form.

However, the researchers explain that this is just one hypothesis, and further work will be needed to understand the anomaly.

Posted by Ben Evans