Ebola: chimp vaccine could be good for humans

If you think there is no vaccine against Ebola, you are wrong. There is at least one. But it may only ever be used to vaccinate chimpanzees.

Researchers at the University of Cambridge in the UK and the New Iberia Research Center in the US have tested the vaccine on captive chimpanzees - with success.

"It is safe and immunogenic," the researchers write in the #link:http://www.pnas.org/embargo?embargoed-uri=http%3A%2F%2Fwww.pnas.org%2Fcontent%2Fearly%2F2014%2F05%2F21%2F1316902111:journal "PNAS"# - meaning, the vaccine induces immune responses which protect the chimpanzees against Ebola.

"If somebody gave me some money and I got permission from the people in the field, I could go and vaccinate wild chimpanzees and gorillas tomorrow," researcher and lead writer Peter Walsh told DW. Walsh is also president of the NGO #link:http://apesinc.org/about-2/who-we-are/: Apes Incorporated#.

As with humans, Ebola is fatal in apes. So aside from the threat from poaching and loss of habitat, the virus poses an added threat to endangered gorillas and chimpanzees in Africa.

From monkeys to gorillas

The vaccine consists of a coat protein that surrounds the Ebola virus. It is not a functional virus, so it cannot cause infection.

"We knew it was safe before we even used it," Walsh says. "The need to do the vaccine trial was just to show people who are afraid of vaccination."

The downside of the vaccine is that the virus protein does not replicate in the body as the live virus does. It would take several shots before an chimp could acquire enough protection - which complicates things for vaccinating in the wild.

Walsh expects that the vaccine would also work on gorillas, but that has yet to be tested.

"It protected monkeys against Ebola infection. The immune response the chimpanzees had was very similar to the immune response the monkeys had. So my guess is it wouldn't cause any health problems in gorillas and it would also have a similar immune response."

According to Walsh, chances are it would also work on humans.

Human trials too expensive

And for vaccinating humans, you need a license.

To acquire a license, you need extensive human clinical trials - and they can be very expensive.

Quite often, large pharmaceutical companies often put up the cash for clinical trials.

But that is also part of the problem.

"No pharmaceutical company is going to make a profit by developing a vaccine against Ebola which is mainly affecting African villagers."

Walsh says several Ebola vaccine candidates work well in monkeys. But none of them is currently being tested in human trials.

"If this was a disease in developed countries where there was a commercial market for the product, one of these vaccines would now be licensed on the market, there is no doubt. The money would be there."

According the research database Pharmaprojects, none of its members is currently working on clinical Ebola vaccine trials. However, it does show that several US and European companies are running Ebola vaccine projects - all in preclinical trials, which tend to be much less expensive.

"The US government will pay for vaccine research, especially for vaccines against terror threats - and Ebola is a bioterror threat," Walsh says. But the government won't finance clinical trials because of the enormous costs.

Vaccinating a non-licensed vaccine

There is, though, at least one vaccine which we know of, which could be used in humans. It has only ever been tested in monkeys - officially. But it has also proved to be effective in humans.

In 2009, a researcher at the Bernhard Nocht Institute in Hamburg accidentally pricked herself with an Ebola-infected syringe.

She was treated with a vaccine brought in from the US. The substance unlicensed as it had only been tested on monkeys.

It consisted of a weakened vesicular stomatitis virus that infects cattle, horses and pigs. It was genetically engineered to contain a portion of an Ebola virus protein.

And the researcher recovered.

An end for trials with chimps?

One other thing will make Ebola vaccine development even harder in the future.

"To our knowledge, our study was the first conservation-related vaccine trial on captive chimpanzees," the authors write in "PNAS". "It may be the last."

The US is the only country that allows biomedical testing on captive chimpanzees. It is banned everywhere else. US legislation is now heading towards an end to this kind of research, so trials on captive chimpanzees may become illegal there as well.

Walsh says that would be a big mistake - not only for human patients needing drugs and vaccines, but also for conservation.

"You try to do something good for captive chimpanzees but in the process you are doing something really bad for wild chimpanzees."

To develop vaccines to protect wild apes from illnesses, researchers have to test them first on captive apes. Park rangers would never allow using a substance on protected wildlife if the substance hasn't been tested on apes in captivity, Walsh says.

But Walsh still hopes to raise the money to vaccinate African chimpanzees and gorillas against Ebola. Chances are he will manage - long before we ever see human clinical trials for the same vaccine.