title: Functional Characterization of Adaptive Mutations during the West African Ebola Virus Outbreak.
abstract: The Ebola virus (EBOV) outbreak in West Africa started in December 2013, claimed more than 11,000 lives, threatened to destabilize a whole region, and showed how easily health crises can turn into humanitarian disasters. EBOV genomic sequences of the West African outbreak revealed nonsynonymous mutations, which induced considerable public attention, but their role in virus spread and disease remains obscure. In this study, we investigated the functional significance of three nonsynonymous mutations that emerged early during the West African EBOV outbreak. Almost 90% of more than 1,000 EBOV genomes sequenced during the outbreak carried the signature of three mutations: a D759G substitution in the active center of the L polymerase, an A82V substitution in the receptor binding domain of surface glycoprotein GP, and an R111C substitution in the self-assembly domain of RNA-encapsidating nucleoprotein NP. Using a newly developed virus-like particle system and reverse genetics, we found that the mutations have an impact on the functions of the respective viral proteins and on the growth of recombinant EBOVs. The mutation in L increased viral transcription and replication, whereas the mutation in NP decreased viral transcription and replication. The mutation in the receptor binding domain of the glycoprotein GP improved the efficiency of GP-mediated viral entry into target cells. Recombinant EBOVs with combinations of the three mutations showed a growth advantage over the prototype isolate Makona C7 lacking the mutations. This study showed that virus variants with improved fitness emerged early during the West African EBOV outbreak.
  
  
  OBJECTIVE
  The dimension of the Ebola virus outbreak in West Africa was unprecedented. Amino acid substitutions in the viral L polymerase, surface glycoprotein GP, and nucleocapsid protein NP emerged, were fixed early in the outbreak, and were found in almost 90% of the sequences. Here we showed that these mutations affected the functional activity of viral proteins and improved viral growth in cell culture. Our results demonstrate emergence of adaptive changes in the Ebola virus genome during virus circulation in humans and prompt further studies on the potential role of these changes in virus transmissibility and pathogenicity.
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.|German Center for Infection Research, Site Gießen-Marburg-Langen, Marburg, Germany.
authors.forename: Erik
authors.initials: E
authors.lastname: Dietzel
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.
authors.forename: Gordian
authors.initials: G
authors.lastname: Schudt
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.|German Center for Infection Research, Site Gießen-Marburg-Langen, Marburg, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Krähling
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany.|German Center for Infection Research, Site Gießen-Marburg-Langen, Marburg, Germany.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Matrosovich
authors.affiliation: Institute of Virology, Philipps University Marburg, Marburg, Germany becker@staff.uni-marburg.de.|German Center for Infection Research, Site Gießen-Marburg-Langen, Marburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Becker
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000354:Africa, Western / Q000453:epidemiology; D019943:Amino Acid Substitution; D002460:Cell Line; D004261:DNA Replication; D004196:Disease Outbreaks; D029043:Ebolavirus / Q000145:classification / Q000235:genetics*; D016679:Genome, Viral; D019142:Hemorrhagic Fever, Ebola / Q000453:epidemiology* / Q000821:virology*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D010802:Phylogeny; D011487:Protein Conformation; D014158:Transcription, Genetic; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication
chemical_list: D014759:Viral Envelope Proteins; D014764:Viral Proteins
keywords: Ebola virus; West Africa; adaptive mutations; glycoprotein; zoonotic infections