Ebola virus: »Present significant challenges for vaccine development«

© WHO

afrol News, 18 November - Human safety testing of an investigational Ebola vaccine began today, according to the US pharmaceutical company Vical Inc. Tests stated after the company has secured a license to market the promising vaccine, which may allow health personal to contain Ebola outbreaks quickly.

Vical announced today that the California-based company had secured a nonexclusive license from the US National Institutes of Health to proprietary gene sequences used in a DNA vaccine for Ebola

The license gives Vical the right to commercialise the vaccine if it is successfully developed and approved for marketing by US authorities, the company says. Human safety testing of the investigational Ebola vaccine also began today using clinical supplies manufactured by Vical.

Vijay Samant, the company's President, said he was pleased to secure commercialisation rights for the Ebola vaccine "as we continue to support its development through optimisation and manufacturing."

- Emerging diseases such as West Nile Virus, Ebola and SARS present significant challenges for vaccine development because they are often rapidly-spreading and potentially life-threatening, added Mr Samant.

The technology presented by Vical further lowered potential safety risk for those involved in the vaccine's development and testing, because the vaccine didn't contain the Ebola virus itself. The vaccine is based on a sequence of DNA from the Ebola virus.

Vaccines traditionally have used the entire bacteria or virus, which is normally killed or weakened before it is injected into the body. There, it serves as a blueprint for the immune system to recognise hostile invaders. A DNA vaccine relies on a strong immune response to the DNA sequence of the virus, which it later recognises on the Ebola virus. The DNA sequence itself is totally harmless for the human body.

The research on an Ebola vaccine so far has mostly been based on collaboration between teams of scientists at the Dale and Betty Bumpers Vaccine Research Centre and the US Army Medical Research Institute of Infectious Diseases. In August this year, the US scientists announced they had made a breakthrough in the development of a vaccine.

Until then, first generation Ebola vaccines had only worked on rodents, but totally failed on primates. This year, however, scientists said they had finally developed a fast-acting Ebola vaccine that protects monkeys after a single shot.

Although Vical expects its vaccine to offer longer-term protection against the virus, scientists do not expect that large-scale vaccination programmes will be the result of a future vaccine. As the Ebola virus is believed to reside in an animal host - probably monkeys - between human outbreaks, it would be impossible to eradicate.

It is anticipated that the vaccine is best used to block the spread of an outbreak that has already started by using a strategy known as "ring vaccination". This involves vaccinating persons close to those already infected, as to protect them from the virus and to create an effective barrier against its further spread.

An outbreak usually occurs when human come in touch with infected animals. In Central Africa, where bush meat is often an essential part of the diet, this may happen when carelessly treating dead monkeys or eating meat that has not been sufficiently fried. When transferred to humans, the virulent virus spreads rapidly from person to person.

Three of the four identified strains of Ebola virus have caused disease in humans: Ebola-Zaire, Ebola-Sudan, and Ebola-Côte d'Ivoire. The fourth, Ebola-Reston, has caused disease in nonhuman primates, but not in humans.

There is currently no specific treatment for the disease, which is often characterised by the sudden onset of fever, weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, limited kidney and liver functions, and both internal and external bleeding.

Outbreaks have been registered since the 1970s and are occurring at a growing paste. Most frequently, Ebola outbreaks occur in Congo Brazzaville, Gabon, Congo Kinshasa and Uganda. There is currently an Ebola outbreak in Congo Brazzaville, which already has claimed more than 10 lives.

By staff writer

© afrol News

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