Experimental vaccine protects monkeys against Ebola for 10 months

Monkeys vaccinated with an experimental drug had developed "long-term" immunity to the Ebola virus, raising a prospect of successful human trials, scientists said, BBC reported.

The US National Institutes of Health conducted experiments that showed immunity could last at least 10 months.

Human trials of the vaccine, which got under way this week in the US would extend to the UK and Africa.

According to The World Health Organization, the outbreak had left more than 2,000 people dead in West Africa.

Several experimental treatments are now under consideration to help contain the spread of the deadly disease, including a vaccine under development by the US National Institute of Allergy and Infectious Diseases (NIAID) and pharmaceutical company GlaxoSmithKline.

The vaccine uses a genetically modified chimp virus containing components of two species of Ebola - Zaire, which is currently circulating in West Africa, and the common Sudan species.

Though the viral vaccine does not replicate inside the body, it was hoped the immune system would react to the Ebola component of the vaccine to impart immunity.

Animal research, on the basis of which the decision to start human trials was based, had been published in the journal Nature Medicine, and showed four crab-eating macaques had survived what would have been a fatal dose of Ebola virus, five weeks later.

The researchers developed the vaccine by incorporating an adenovirus found in the monkeys which was similar to the one in humans. The adenovirus known to trigger respiratory tract infections was spliced with the Ebola gene in the genetic code.

The monkeys were then administered the virus, allowing it to introduce the Ebola to target cells that would trigger the production of Ebola proteins.

The host's immune system would then recognise the proteins as foreign bodies and then fight against these structures. The theory behind the vaccine was that since the body had already encountered the ''virus'' which in this case was a spliced gene, it was prepared to fight the actual virus, if it was encountered.

According to Nancy Sullivan, lead researcher for NIAID, the new study actually used two vaccines - the first dose protected against the mononegavirus immediately and the second provided more long-term protection. Though the latter used a different strain, referred to as modified vaccine Ankara (MVA), it utilised the same gene responsible for coding the Ebola protein.