title: Genome sequence analysis of in vitro and in vivo phenotypes of Bunyamwera and Ngari virus isolates from northern Kenya.
abstract: Biological phenotypes of tri-segmented arboviruses display characteristics that map to mutation/s in the S, M or L segments of the genome. Plaque variants have been characterized for other viruses displaying varied phenotypes including attenuation in growth and/or pathogenesis. In order to characterize variants of Bunyamwera and Ngari viruses, we isolated individual plaque size variants; small plaque (SP) and large plaque (LP) and determined in vitro growth properties and in vivo pathogenesis in suckling mice. We performed gene sequencing to identify mutations that may be responsible for the observed phenotype. The LP generally replicated faster than the SP and the difference in growth rate was more pronounced in Bunyamwera virus isolates. Ngari virus isolates were more conserved with few point mutations compared to Bunyamwera virus isolates which displayed mutations in all three genome segments but majority were silent mutations. Contrary to expectation, the SP of Bunyamwera virus killed suckling mice significantly earlier than the LP. The LP attenuation may probably be due to a non-synonymous substitution (T858I) that mapped within the active site of the L protein. In this study, we identify natural mutations whose exact role in growth and pathogenesis need to be determined through site directed mutagenesis studies.
authors.affiliation: Human Health Division, International Centre of Insect Physiology and Ecology, Nairobi, Kenya; Zoonoses Research Unit, Department Medical Virology, University of Pretoria, Pretoria, South Africa; Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya.
authors.forename: Collins
authors.initials: C
authors.lastname: Odhiambo
authors.affiliation: Zoonoses Research Unit, Department Medical Virology, University of Pretoria, Pretoria, South Africa.
authors.forename: Marietjie
authors.initials: M
authors.lastname: Venter
authors.affiliation: Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya.
authors.forename: Konongoi
authors.initials: K
authors.lastname: Limbaso
authors.affiliation: Zoonoses Research Unit, Department Medical Virology, University of Pretoria, Pretoria, South Africa.
authors.forename: Robert
authors.initials: R
authors.lastname: Swanepoel
authors.affiliation: Human Health Division, International Centre of Insect Physiology and Ecology, Nairobi, Kenya; Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya; Division of Emerging Infectious Disease, United States Army Medical Research Unit, Nairobi, Kenya.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Sang
mesh_terms: D000818:Animals; D002042:Bunyamwera virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D014644:Genetic Variation; D016679:Genome, Viral; D006801:Humans; D007630:Kenya; D051379:Mice; D010641:Phenotype; D017423:Sequence Analysis, RNA