title: Selection of antigenic variants in maedi-visna virus infection.
abstract: In order to analyse the pattern of sequence variation in maedi-visna virus (MVV) in persistently infected sheep and to answer the question of whether antigenic variants are selected in a long-term MVV infection, an 87 bp variable region in the env gene of ten antigenic variants and 24 non-variants was sequenced. Nine of the ten antigenic variants had mutations in this region, comprising 24 point mutations and a deletion of 3 bp. Twenty-three of the point mutations (96%) were non-synonymous. There was only a single mutation in this region in the 24 non-variants. A type-specific neutralizing antibody response appeared in all the sheep 2-5 months post-infection, and in most sheep more broadly reacting neutralizing antibodies appeared up to 4 years later. All the antigenic variants were neutralized by the broadly reacting sera. It is noteworthy that the antigenic variants were isolated at a time when only the type-specific antibodies were acting, before the broadly reacting antibodies appeared. The same picture emerged when molecularly cloned virus was used for infection. Three sheep were infected with a molecularly cloned virus, and of six virus isolates, one was an antigenic variant. This variant arose in the absence of broadly reacting antibodies. The results indicate that there is selection for mutants that escape neutralization.
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Valgerdur
authors.initials: V
authors.lastname: Andrésdóttir
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Robert
authors.initials: R
authors.lastname: Skraban
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Sigrídur
authors.initials: S
authors.lastname: Matthíasdóttir
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Roger
authors.initials: R
authors.lastname: Lutley
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Gudrún
authors.initials: G
authors.lastname: Agnarsdóttir
authors.affiliation: Institute for Experimental Pathology, University of Iceland, Keldur, IS-112, Reykjavík, Iceland1.
authors.forename: Hólmfrídur
authors.initials: H
authors.lastname: Thorsteinsdóttir
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000940:Antigenic Variation / Q000235:genetics* / Q000276:immunology; D002460:Cell Line; D015752:Genes, env; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D011021:Pneumonia, Progressive Interstitial, of Sheep / Q000276:immunology / Q000821:virology*; D017422:Sequence Analysis, DNA; D012756:Sheep; D013997:Time Factors; D014779:Virus Replication; D014790:Visna-maedi virus / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology
chemical_list: D000914:Antibodies, Viral