December 16, 2002
Purdue research hints that birds could spread Ebola virus
WEST LAFAYETTE, Ind. Ebola shares a closer relationship with several bird viruses than was previously thought, bolstering the case for a common ancestor and hinting that birds might carry the deadly virus, a Purdue University research team reports.
David Sanders and his research group have discovered that the outer protein shell of Ebola has a biochemical structure similar to several retroviruses carried by birds. As scientists had known previously of genetic similarity among the viruses, this discovery makes a common evolutionary origin even more likely. It also suggests that Ebola could be spread to human populations by birds as well.
"We knew these viruses were inwardly similar, and now we see their outer similarity as well," said Sanders, associate professor of biological sciences in Purdue's School of Science. "While bird transmission of Ebola is by no means certain, the resemblance among all these viruses should encourage health officials to be on guard for it."
The research appears in Sunday's (12/15) Journal of Virology. Two contributors to the group's research are Scott Jeffers, a graduate student in Sanders' laboratory, and Anthony Sanchez, an Ebola virus expert at the Centers for Disease Control.
Since its discovery in 1976, Ebola has been responsible for hundreds of deaths in central Africa. Though the source of the virus in nature remains unknown, both humans and monkeys appear susceptible. Death rates of between 50 percent and 90 percent are common during outbreaks.
"Ebola is one of the viruses with which the U.S. agencies in charge of biodefense are most concerned," Sanders said. "Identification of its natural hosts should be a priority."
This research was sponsored by the Cystic Fibrosis Foundation and the Purdue Research Foundation.
Writer: Chad Boutin, (765) 494-2081, firstname.lastname@example.org
Source: David A. Sanders, (765) 494-6453, email@example.com
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Covalent Modifications of the Ebola Virus Glycoprotein
Scott A. Jeffers, David Avram Sanders, and Anthony Sanchez
The roles of the covalent modifications of the Ebola virus glycoprotein (GP) and the significance of the sequence identity between filovirus and avian retrovirus glycoproteins were investigated through biochemical and functional analyses of mutant GPs. The expression and processing of mutant GPs with altered N-linked glycosylation, substitutions for conserved cysteine residues, or a deletion in the region of O-glycosylation were analyzed, and viral entry capacities were assayed through use of pseudotyped retroviruses. Cys-53 was the only GP1 cysteine residue whose replacement resulted in efficient secretion of GP1 and it is therefore proposed that it participates in the formation of the only disulfide bond linking GP1 to GP2. We propose a complete cystine-bridge map for the filovirus glycoproteins based upon our analysis of mutant Ebola virus GPs. The effect of replacement of the conserved cysteines in the membrane-spanning region of GP2 was found to depend on the nature of the substitution. Mutations in conserved N-linked glycosylation sites proved generally, with a few exceptions, innocuous. Deletion of the O-glycosylation region increased glycoprotein processing, incorporation into retrovirus particles and viral transduction. Our data support a common evolutionary origin for the glycoproteins of Ebola virus and avian retroviruses and have implications for gene transfer mediated by Ebola virus glycoprotein-pseudotyped retroviruses.