A potential treatment to combat infection with the deadly Ebola virus has shown promising results in a study of monkeys.
The haemorrhagic fever is one of the most virulent diseases known. Its death rate is about 80 per cent in humans and 99.9 per cent in rhesus macaques. There is currently no specific treatment or cure.
But a preliminary study by US scientists has revealed that giving infected monkeys a shot of an anti-blood-clotting protein saved a third of their lives. Tom Geisbert, at the US Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland, led the study and calls the results 鈥渞eally exciting鈥�.
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鈥淪ome compounds have worked in rodents but nothing worked in monkeys. We were not expecting them to survive,鈥� he told 快猫短视频. 鈥淵ou are going from nothing to at least some hope of a treatment.鈥�
The protein, called rNAPc2, works by slowing the formation of the blood clots caused by Ebola. This helps because the virus sends the clotting process into overdrive. Although Ebola is known to cause profuse bleeding, in many cases it is clot-related organ failure that causes death.
Geisbert believes rNAPc2 gave the monkeys enough time for their immune systems to fight back against the virus. 鈥淲e got them through that critical window. The monkeys survived long enough so it tipped the balance in favour of the host.鈥�
Lost balance
One of the Ebola virus鈥檚 key targets are special immune cells called macrophages. This causes the body鈥檚 macrophages to over produce 鈥渢issue factors鈥�, which in turn cause clotting.
鈥淭he host鈥檚 constantly trying to keep a balance between clotting and breaking down clots,鈥� explains Geisbert, a virologist. 鈥淲hat happens with Ebola is that the host loses the ability to control that.鈥�
Ebola鈥檚 effects vary from host to host. But in rhesus macaques it causes lots of small 鈥渕icroclots鈥� and can cause organs such as the liver to clog up with an insoluble protein called fibrin. The compound rNAPc2 slows down the formation of fibrin.
Geisbert and colleagues infected 12 monkeys with Ebola. Nine were given shots of rNAPc2 either 10 minutes later or 24 hours later. The others were given a saline control, and controls from older experiments were also used for comparison.
Three of the treated monkeys survived and were still alive and healthy 12 months later. The six treated monkeys which died lived longer than untreated monkeys 鈥� 12 days on average compared with eight days.
Compassionate protocol
Geisbert believes rNAPc2 could be a useful treatment in combination with a drug to target the virus itself. He hopes similar benefits might be seen in humans, although he cautions that scientists鈥� knowledge on the disease in humans is limited.
The World Health Organization has expressed an interest in using rNAPc2 under a 鈥渃ompassionate鈥� protocol for future human outbreaks in the Democratic Republic of Congo, he says. The latest outbreak there started on 31 October and has killed 29 people and infected 48 others.
The drug could also be useful in treating the other viral haemorrhagic fevers seen around the world, says the team. For example, over 1000 people have been infected during an outbreak of haemorrhagic fever with renal syndrome in Kazakhstan and Russia in 2003.
Journal reference: The Lancet (vol 362, p 1953)