The US5 Open Reading Frame of Herpes simplex Virus Type 1 Does Encode a Glycoprotein (gJ)

Abstract

Based on sequence analysis, the protein encoded by the US5 open reading frame (ORF) of herpes simplex virus type 1 (HSV-1) was predicted to contain an N-glycosylation site and was given the designation of glycoprotein J (gJ). However, the US5 gene product has not been identified and the identity of gJ as a glycoprotein has not been confirmed. We have cloned and expressed the DNA encoding the complete sequence of the US5 ORF, using a baculovirus expression system. Western blotting, using polyclonal antibody raised against synthetic US5 peptides, revealed two major baculovirus-US5-expressed protein bands with apparent molecular weights of 16–17 and 10 kD. The recombinant US5 was found on the membrane of Spodoptera frugiperda cells and was susceptible to tunicamycin, endoglycosidase H, glycosidase F and partially resistant to endoglycosidase F. Vaccination of mice with baculovirus-expressed US5 did not induce a neutralizing antibody to HSV-1 or provide protection against lethal HSV-1 challenge. However, serum from these vaccinated mice was able to recognize US5 in purified HSV-1 virions by Western blot analyses and on the surface of HSV-1-infected cells by immunofluorescence. These findings establish that US5 does encode a glycoprotein and confirm the appropriateness of naming the US5 gene product gJ.