Glycoprotein gD of MDV lacks functions typical for alpha-herpesvirus gD homologues

Glycoprotein D (gD) belongs to family of conserved structural proteins of a lpha-herpesviruses. During productive infection of cells by herpes simplex virus 1 (HSV-1) go has several important functions, is involved in virus pe netration to and release from infected cells and is one of main targets of neutralizing antibodies. Similar functions are shared also by other alpha-h erpesvirus go homologues, Surprisingly, in previous studies it was found th at MDV go expression could not be detected during infection in vitro using immunological methods. In this study we have analyzed expression of MDV go and its biological consequences. In vitro expression using rabbit reticuloc yte lysate and/or overexpression in transfected cells showed that the secon d ATG codon is required for synthesis of mature, glycosylated gD. In additi on, it was found that go we overexpression is neither toxic for transfected cells nor is involved in membrane fusion. After MDV infection of a proprie tary cell line stably transfected with plasmid overexpressing MDV gD, no vi ral particles could be found in culture. On the other hand, cells overexpre ssing the MDV go were sensitive to,MDV infection in similar way as parental , non-transfected cells. From our study and results of Ether authors we pro pound the following conclusions: (i) MDV go expression is blocked during in vitro infection at transcription level; (ii) MDV go is lacking many import ant functions characteristic for other alpha-herpesvirus gD homologues; (ii i) overexpression of single MDV go does not result in production of mature infectious MDV particles.