Draco’s magic spells death for viruses
It’s being called the greatest discovery since penicillin, a Light Sabre-like experimental drug that destroys all viruses that infect and kill.Updated: Aug 13, 2011 23:17 IST
It’s being called the greatest discovery since penicillin, a Light Sabre-like experimental drug that destroys all viruses that infect and kill. If it indeed works half as well as expected, this drug could abort killer infections — such as HIV that causes AIDS, influenza, dengue, polio, jaundice, measles, rabies, among others — before they get a chance to wreck havoc inside the body.
In theory, the drug — double-stranded RNA (dsRNA) activated caspase oligomeriser, with the rather cool acronym of DRACO — homes in on cells infected with viruses of all types and makes them self-destruct.
In lab tests on rats, DRACO killed 15 viruses. And it did so without harming healthy cells around them. Apart from shielding against viruses that raise fears of bioterrorism, such as Ebola and smallpox, DRACO would help stop most emerging epidemics, which are almost always viral in origin, be it the Spanish Flu of 1917 that killed 20 million people within a year, to H1N1 (swine flu) of 2009 that cost the world many more millions to contain.
These infections quickly spiral out of control because of a virus’ quicksilver ability to mutate and evade existing drugs with ease. This forces pharmaceutical companies to introduce different drugs and vaccines each year that work against that one specific virus, virus strain or family that is causing infection that year.
For the past five decades, the standard treatment has been to use preventive vaccines, and, if that fails, then using prescription drugs to treat the infection caused by a specific virus, such as oseltamivir and zanamivir to treat H1N1 (swine flu).
The new drug DRACO targets a molecule common to all virus-infected cells. Nearly every virus generates strings of double-stranded RNA longer than 30 base pairs to duplicate itself and take control of the host cell. The immune arsenal within human cells includes a protein that exploits this viral characteristic. Todd Rider of the Massachusetts Institute of Technology’s Lincoln Laboratory in the US made the drug by combining this protein with another from the immune system.
When a sentinel enzyme called protein kinase R (PKR) finds double-stranded RNA longer than 23 base pairs inside a cell, it binds to the RNA, blocks the production of viral proteins and activates the cell’s defences. Most viruses can evade PKR. So Rider and his team attached PKR to a protein called apoptotic protease activating factor 1 (APAF-1), which releases destructive enzymes to trigger cell suicide before the virus takes over.
Even if virus fragments escape the destroyed cell, they do so minus the protein cover needed to help them travel between cells, which keeps the surrounding healthy tissue free of infection.
There are some challenges, such as DRACO being too large a protein to enter cells with ease. Also, the way the drug functions would make it effective only in very early stages of infection.
In advanced viral infections, destroying all infected cells could lead to organ failure, as may happen if the infected cells are the hepatocyte cells in the liver. In children, people over 65 years and those with compromised immunities — such as people with HIV or liver disease -- the generalised weakness induced by mass cell death could heighten sickness and cause death. The drug would also not work against viruses have evolved ways to conceal their double-stranded RNA.
It’s way too early to uncork the bubbly, but DRACO’s the closest the world’s got to a blueprint of a medical nuke to obliterate viruses, which killed far more people in the last century than the two world wars. It’s effectiveness can only be tested over time because viruses, like bacteria, have a way of staying a step ahead of new and newer prescription medication.
First Published: Aug 13, 2011 23:15 IST