Keywords :
Adjuvants, Immunologic/metabolism; Amino Acid Sequence; Animals; Antibodies, Monoclonal/immunology; Antigenic Modulation; Cell Line; Female; Genome, Viral; Herpesviridae Infections/immunology; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Mutation; Neutralization Tests; Plant Lectins/metabolism; Polysaccharides/chemistry/metabolism; Rhadinovirus/chemistry/genetics/metabolism; Sequence Alignment; Viral Envelope Proteins/genetics/immunology; Virion/genetics/metabolism; Virus Replication
Abstract :
[en] Herpesviruses characteristically transmit infection from immune hosts. Although their success in escaping neutralization by pre-formed antibody is indisputable, the underlying molecular mechanisms remain largely unknown. Glycoprotein B (gB) is the most conserved component of the herpesvirus entry machinery and its N terminus (gB-NT) is a common neutralization target. We used murid herpesvirus-4 to determine how gB-NT contributes to the virus-antibody interaction. Deleting gB-NT had no obvious impact on virus replication, but paradoxically increased virion neutralization by immune sera. This reflected greater antibody access to neutralization epitopes on gH/gL, with which gB was associated. gB-NT itself was variably protected against antibody by O-linked glycans; on virions from epithelial cells it was protected almost completely. gB-NT therefore provides a protective and largely protected cover for a vulnerable part of gH/gL. The conservation of predicted glycosylation sites in other mammalian herpesvirus gB-NTs suggests that this evasion mechanism is widespread. Interestingly, the gB-NT glycans that blocked antibody binding could be targeted for neutralization instead by a lectin, suggesting a means of therapeutic counterattack.
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