Murine gammaherpesvirus-68 ORF28 encodes a non-essential virion glycoprotein

Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK Correspondence Philip G. Stevenson pgs27{at}mole.bio.cam.ac.uk Murine gammaherpesvirus-68 (MHV-68) ORF28 is a gammaherpesvirus-specific gene of unknown function. Analysis of epitope-tagged ORF28 protein indicated that it was membrane-associated and incorporated into virions in N -glycosylated, O -glycosylated and unglycosylated forms. The extensive glycosylation of the small ORF28 extracellular domain – most forms of the protein appeared to be mainly carbohydrate by weight – suggested that a major function of ORF28 is to attach a variety of glycans to the virion surface. MHV-68 lacking ORF28 showed normal lytic replication in vitro and in vivo and normal latency establishment. MHV-68 ORF28 therefore encodes a small, membrane-bound and extensively glycosylated virion protein, whose function is entirely dispensable for normal, single-cycle host colonization. Present address: Department of Immunology, Department of Pathology, University of Cambridge, UK.