Antibody evasion by a gammaherpesvirus O-glycan shield

All gammaherpesviruses encode a major glycoprotein homologous to the epstein-barr virus gp350. these glycoproteins are often involved in cell binding,and some provide neutralization targets. however,the capacity of gammaherpesviruses for long-term transmission from immune hosts implies that in vivo neutralization is incomplete. in this study,we used bovine herpesvirus 4 (bohv-4) to determine how its gp350 homolog - gp180 - contributes to virus replication and neutralization. a lack of gp180 had no impact on the establishment and maintenance of bohv-4 latency,but markedly sensitized virions to neutralization by immune sera. antibody had greater access to gb,gh and gl on gp180-deficient virions,including neutralization epitopes. gp180 appears to be highly o-glycosylated,and removing o-linked glycans from virions also sensitized them to neutralization. it therefore appeared that gp180 provides part of a glycan shield for otherwise vulnerable viral epitopes. interestingly,this o-glycan shield could be exploited for neutralization by lectins and carbohydrate-specific antibody. the conservation of o-glycosylation sites in all gp350 homologs suggests that this is a general evasion mechanism that may also provide a therapeutic target. © 2011 machiels et al.