In a article published July 27, 2011 in the open-access magazine PLoS One, the researchers tested the drug DRACO against fifteen viruses from completely different groups. They found the drug to be effective against all 15 - including rhinoviruses (which cause the common cold), influenza (flu virus), polio, rotavirus, dengue virus (which causes dengue fever) and various types of bleeding viruses.
Few antivirals so far
The drug acts on a type of RNA that is only produced in cells that are infected by viruses. "In theory, this should work against all viruses," said Todd Rider, along with several other researchers at Lincoln Lab, the inventors of the new technology. The technique intervenes on a universal weakness of all viruses and is therefore very broad spectrum. In theory, this technique can also be used against new, unknown viruses such as the virus that caused the SARS outbreak in 2003, says Rider. This would make the substance one of the very few effective antiviral agents. For example, the few antivirals currently used against HIV are effective against a limited group of viruses. Viruses also develop resistance very quickly.
DRACOs: virus detector linked to suicide protein
Rider based his collection of drugs, DRACOs (Double-stranded RNA Activated Caspase Oligomerizers), on the existing defense mechanisms of living cells. When viruses enter a cell, they take control of the cell and turn the cell into an assembly line for viruses. During this process, viruses produce double chains of RNA (ds RNA). Every known virus forms ds-RNA at some point in its existence . RNA usually never occurs as a double chain in the human body. DS-RNA therefore immediately induces an immune response in the cell: a cascade of biochemical reactions that fight the virus. However, viruses are often able to block the immune response further down the cascade.
Rider takes a different approach. DRACO consists of a protein that binds to ds RNA, combined with another protein, caspase, that causes cells to commit suicide (apoptosis). Caspase prevents cancer and virus infection in many cases - if a cell is terminally ill, caspase causes the cell to die. When one end of DRACO binds to ds-RNA, the suicide protein on the other end of DRACO becomes active and the cell kills itself. Fellow researchers say the approach is promising. It is virtually impossible for a virus to bypass the ds-RNA phase. This underlies the entire reproductive cycle of almost all viruses (which is very remarkable, by the way). Resistance will therefore not develop quickly.
The DRACOs are also labeled, derived from natural proteins, that allow the drug to cross cell membranes and enter any human or animal cell. If no dsRNA is present, DRACO leaves the cell without damage.
Mice cured of H1N1 influenza virus
Most of the tests with DRACO were performed with human and animal cells in the laboratory, but the researchers also tested DRACO in mice that had the H1N1 influenza virus (the Mexican flu) were infected. DRACO was found not to be toxic to the mice and was found to remove the virus completely. At the moment (August 2011) the researchers are testing DRACO for more virus types in mice and they say they are achieving promising results. There are plans to conduct animal experiments on larger animals and eventually clinical trials on humans. The promises of this remedy are enormous. Tens of millions of deaths are caused by viral diseases every year. Let's hope that an effective medicine will be developed from this.