Washington: In what could be called as a breakthrough study, monkeys infected with the deadly Ebola virus have been treated successfully-a feat that could possibly bring humans a step closer to a cure.
According to a new study, a team of scientists used special gene-silencing drugs to selectively "knock out" viral proteins in Chinese rhesus macaques infected with a lethal dose of the Zaire Ebola virus.
Zaire is the most virulent strain of Ebola-90 percent of infected people die during outbreaks.
Ebola spreads via bodily fluids or tainted needles and razors, and it`s highly contagious.
Infections in humans and other primates typically cause acute fever and headaches, followed by uncontrollable bleeding from the body`s openings. Shock from heavy internal and external bleeding usually proves fatal.
"Ebola is not only of interest because it can cause high mortality, but also because it can be used as a bioterror weapon," National Geographic quoted study leader Thomas Geisbert, a virologist at Boston University, as saying.
"There are a lot of groups working on preventive vaccines, but this is the first time someone has developed a post-exposure treatment," he added.
The researchers used drugs based on synthetic versions of small interfering RNA, or siRNA, a type of molecule in the body that can interfere with the expression of particular genes. (Get a genetics overview.)
Since genes are the codes the body uses to make proteins, interfering with specific viral genes should stop production of proteins the Ebola virus needs to survive.
"We specifically targeted the L protein, as it kick-starts virus replication. If you knock out that protein, you can really inhibit the ability of the virus to replicate," said Geisbert.
The team also targeted the VP24 and VP35 proteins, which are involved in disabling an infected host`s immune response.
Seven of the nine monkeys in the study received the same amount of the drug over a six-day period.
Three of the seven monkeys got the drug every other day, while four received it daily.
One monkey in each group served as a control animal and didn`t receive the drug.
On analysing the treated monkeys, it was found that ten days after having been infected with Ebola, the first group of monkeys had very low levels of the virus in their blood.
Researchers could not detect the virus at all in the group that had received daily doses.
"The siRNAs inhibited the replication of the virus and completely protected the monkeys against death from hemorrhagic fever. This has never been done before," noted Geisbert.
Geisbert thinks the real novelty of the study-is that the scientists were able to deliver the drug to infected cells, which can be a challenge, because synthetic siRNA drugs can activate the body`s immune system, triggering inflammation.
To ferry the drug into cells while preventing unwanted side effects, the researchers packed the drug inside fat molecules.
"This capability offers a therapeutic option that has been lacking with certain hemorrhagic fever viruses that have a high level of mortality associated with infections," said Anthony Sanchez, an Ebola researcher at the US Centers for Disease Control and Prevention.
"The interesting part of the technique is that the [siRNA drug] can be quickly synthesized for a specific strain of Ebola virus. Thus, if a new strain suddenly appears, whether in Africa or in another region of the world, a therapeutic solution can be quickly generated and deployed for use," added Sanchez.
In a commentary on the study, Heinz Feldmann of the U.S. National Institute of Allergy and Infectious Diseases wrote that the new work is "long overdue and should be considered a milestone in what has been a difficult and frustrating specialty of filovirus research."