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Good News on Fast Tracked Ebola Vaccine

The current Ebola outbreak is the worst the world has ever seen with 22,000 infections and 9,000 deaths recorded so far. The epidemic has affected six West African nations with Guinea, Sierra Leone and Liberia among the worst hit. With a mortality rate between 50% and 90%, the virus spreads through the human population with devastating consequences. But the first batch of an experimental vaccine— now being sent to Liberia—offers fresh hope to control the disease. This is one of many human trials set to take place in 2015, a process that would not have been possible without animal research.

Ebola is a viral disease that is transmitted to people from wild animals. The virus is thought to exist naturally in some fruit bats and can be transmitted to humans through bodily fluids of infected animals or through the consumption of ‘bush meat.’ Once the virus is introduced to the human population it spreads through direct contact with bodily fluids of infected people. Symptoms such as fever and bleeding from orifices can be seen after four to ten days.

The epidemic was declared a Public Health Emergency of International Concern last year by the World Health Organization (WHO) as the disease has severely impacted both rural and urban areas in West Africa. While there are currently no proven treatments or vaccines for Ebola WHO has fast tracked a number of products including two candidate vaccines and two antiviral drugs.

“We are supporting all vaccine research and development through information sharing, networking and arranging regular meetings, where we bring researchers, developers, manufacturers, regulators, clinicians, policymakers and other interested parties together to find best ways to expedite the research, testing and licensing of vaccines,” says WHO spokesperson Margaret Harris.

There are two vaccine candidates currently undergoing human trials. The first is being developed by GlaxoSmithKline (GSK) in collaboration with the United States National Institutes for Health (cAd3-ZEBOV vaccine). 300 vials of the vaccine have just been sent to Liberia today on a Brussels Airlines flight. The other vaccine is being produced by NewLink Genetics and Merck Vaccines USA, in collaboration with Health Canada (rVSV-ZEBOV vaccine).

These trials will test for both safety and the vaccine’s capacity to induce an immune response on a larger scale, to have the best possible impact on the affected population including vulnerable members of the community such as children, the elderly, and persons living with HIV.

Harris tells EARA, “There are challenges to implementing wide-scale trials, such as enrolling larger numbers, finding appropriate populations and managing public concerns and perceptions about the nature, safety and purpose of vaccines.”

The vaccines were first tested on non-human primates, who developed both antibody and T cell responses that protected them against disease when they were later challenged with the Ebola virus.

“All the vaccines that have moved into human trials have shown great efficacy when tested in non-human primates,” says Harris, “Therefore, our evidence of efficacy of these vaccine candidates depend on non-human primates.”

There are currently no treatments for the Ebola virus; those affected are given supportive care-rehydration with oral or intravenous fluids to improve their systems. While WHO continues to test and develop treatments, our best hopes may lie with the experimental drug ZMapp that treated two American aid workers under the ‘compassionate-use’ doctrine.

ZMapp is a cocktail of three antibodies that was first developed through research in mice. Researchers exposed mice with the Ebola virus and the antibodies generated within the mice’s blood were extracted. To produce the drug in large volumes, a gene from the modified mice antibodies were introduced to the leaves of tobacco plants, which were then harvested.

“These anti-viral antibodies act by binding and neutralising the Ebola virus and can also trigger killing of infected cells by the immune system,” says Larry Zeitlin, president of Mapp Biopharmaceutical.

Zeitlin led a team of researchers to test the drug on rhesus macaques, where 18 were given three doses of the drug. One dose was administrated three days after they were infected with the virus, another after four, and the final group after five days. The monkeys that received the virus—irrespective of when—survived; the three monkeys that were not treated died.

“We tested on macaques as it’s believed to be the model most representative of the course of human disease for filoviruses like Ebola,” says Zetilin.

He tells EARA that after these promising results, the drug will soon undergo human trials.

Coupled with education programmes and the build-up of medical infrastructure, vaccines and an effective treatment is hoped to halt the rapid spread of the disease in West Africa. But, on the road to finding safe vaccines and treatments to Ebola, there are currently no alternatives to animal research. Simply put, finding an effective vaccine would not have been possible without animal research.

The Ebola epidemic highlights the need for animal research to continue the progression of modern medicine.

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