Discovering a single therapy that treats four killer diseases could prove extremely useful especially as these viruses are widespread in third world countries, where a single treatment would prove economically viable and where laboratory test facilities are scarce.
Scientists at the University of Georgia's College of Veterinary Medicine, reported the blocking of a protein that helps transport viruses out of a cell keeps these four viruses from reproducing and infecting other cells.
"We believe that interfering with the Rab9 pathway interferes with the ability of the viruses to exit the cell, thereby dramatically decreasing the ability of the virus to spread rapidly and produce infection," said Thomas Hodge, research professor of infectious diseases at the veterinary college.
Rab9 is a factor required for viruses to reproduce in a cell and because these viruses depend heavily on this exit pathway, they probably would not be able to find another route out of the cell.
This suggests that Rab9 and other components of this exit pathway might be attractive targets for antiviral therapies for a variety of viruses.
Blocking Rab9 may have significant side effects, but there are people who live without Rab9, Hodge explained. Although they have metabolic problems, they are generally able to control their condition with diet and medication.
Temporarily blocking the Rab9 pathway would be unlikely to harm the body, Hodge added, because human cells tend to have backup systems that can compensate.
Most antiviral therapies target the virus itself, but viruses are quick to adapt to the body's attempts to disable them, he explained.
They can mutate rapidly and develop resistance to almost any antiviral compound. By focusing on the host cell while most scientists concentrate on the virus, Hodge and his colleagues hope to identify new ways to combat viral diseases.
Hemorrhagic fevers (Ebola, Marburg and Lassa Fever) are high priority viruses identified as bioterror threats and for which there is currently no drug available for therapy.
Infected patients are treated using antiviral drugs ribavirin, a drug commonly used in treatment of hemorrhagic fevers, that acts as an RNA mutagen on the virion particles.
A new drug therapy for Ebola haemorrhagic fever has shown early promise in laboratory studies and is currently being evaluated further at the National Institute of Health.
The drug, Cyanovirin-N (CV-N), a cyanobacterial lectin, is a potent viral entry inhibitor currently under development as a microbicide against a broad spectrum of enveloped viruses.
CV-N was originally identified as a highly active anti-HIV agent and later, as a virucidal agent against other unrelated enveloped viruses such as Ebola, and possibly other viruses.
Methods of detecting such viruses include antigen-capture enzyme-linked immunosorbent assay (ELISA) testing, IgM ELISA, polymerase chain reaction (PCR), and virus isolation. All can be used to diagnose a case of Ebola HF within a few days of the onset of symptoms.
Persons tested later in the course of the disease or after recovery can be tested for IgM and IgG antibodies; the disease can also be diagnosed retrospectively in deceased patients by using immunohistochemistry testing, virus isolation, or PCR.
Hodge's research is currently being published in the September issue of the Journal of Virology.