The herpes simplex viruses types 1 and 2 (HSV-1 and HSV-2), also known as human herpesvirus types 1 and 2, are important human pathogens belonging to the subfamily alphaherpesviridae of the family herpesviridae. HSV is the cause of severe and even life-threatening disseminated infections in immunologically deficient individuals and infants. HSV-1 and HSV-2 possess at least seven different glycoproteins labelled gB, gC, gD, gE, gG, gH and gI. The existence of two additional glycoproteins is deduced from the the nucleotide sequence of the gD gene. . Glycoproteins B, D and H are essential for infection by HSV. The role of gD in the viral replication cycle has been partly elucidated by analysis of the effects of its removal and its blockade.