title: Characterization of monoclonal antibody-escape mutants of tick-borne encephalitis virus with reduced neuroinvasiveness in mice.
abstract: Escape mutants of tick-borne encephalitis (TBE) virus were selected using neutralizing monoclonal antibodies (MAbs) that react with three different and previously unrecognized epitopes in the envelope protein E of TBE virus. Two of these variants (V-IC3 and V-IE3) exhibited a significantly reduced reactivity with their selecting MAbs, as determined by ELISA, whereas with one variant (V-IO3), reactivity was completely unchanged. Comparative sequence analyses demonstrated that each of the variants differed from the wild-type virus by a single amino acid substitution located at exposed positions within domains I, II and III of protein E. In the mouse model, all three mutants were still neuro-virulent but exhibited a significantly reduced neuro-invasiveness after subcutaneous inoculation. Virus replication, however, was sufficient to induce a specific antibody response. The observed alterations in virulence properties were not associated with reduced growth rates in vertebrate cell cultures, but one variant (V-IE3) exhibited a small plaque phenotype. The mutation of variant V-IO3 resulted in a temperature-sensitive phenotype and a significant elevation of the pH-threshold of the conformational change necessary for fusion activity.
authors.affiliation: Institute of Virology, University of Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Holzmann
authors.forename: K
authors.initials: K
authors.lastname: Stiasny
authors.forename: M
authors.initials: M
authors.lastname: Ecker
authors.forename: C
authors.initials: C
authors.lastname: Kunz
authors.forename: F X
authors.initials: FX
authors.lastname: Heinz
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral / Q000096:biosynthesis* / Q000097:blood; D001483:Base Sequence; D002642:Chick Embryo; D004669:Encephalitis Viruses, Tick-Borne / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity*; D004797:Enzyme-Linked Immunosorbent Assay; D014644:Genetic Variation; D051379:Mice; D008969:Molecular Sequence Data; D009420:Nervous System / Q000821:virology*; D009500:Neutralization Tests; D010641:Phenotype; D017354:Point Mutation; D012367:RNA, Viral / Q000737:chemistry / Q000302:isolation & purification; D013696:Temperature; D014759:Viral Envelope Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D010948:Viral Plaque Assay; D014774:Virulence
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D012367:RNA, Viral; D014759:Viral Envelope Proteins; C065696:glycoprotein E, Flavivirus