Iowa State University researchers say they have discovered how the Ebola Virus is able to elude the immune response of host cells that it invades. The problem has stumped scientists for many years, and in a new study published in Nature Structural and Molecular Biology, the Iowa team says that host cells can't recognize and respond to the virus because of a dirty little trick it plays.

When most viruses invade cells, they begin producing RNA in order to replicate. In response,  the healthy host cells activate anti-viral defenses that halt replication and eventually help clear the viral infections

A viral protein involved in immune suppression called VPN35 actually masks the replicating viral ribonucleic acid (RNA), so the cells don't recognize that there is an invading virus. One of the reasons Ebola, in particular the strain isolated from Zaire, is so deadly is that the host cells don't have any immune response when the virus enters the cell.

During the study, researchers focused on a specific part of the Zaire Ebola VP35 protein that looked unusual. As testing results came in, they found that the suspect region of the protein was binding with, or neutralizing, the part of the host cell that triggers the immune system in the cell.

"The interesting thing about the Ebola virus is that it doesn't let cells even get started to defend themselves," co-author Gaya K Amarasinghe explained. "This hides the (viral) RNA from being recognized by the host cell. This is a powerful immune evasion mechanism."







Citation:
Daisy W Leung et al., 'Structural basis for dsRNA recognition and interferon antagonism by Ebola VP35', Nature Structural and Molecular Biology, January 2010; doi:10.1038/nsmb.1765