This modified HSV gD protein is a modified protein of a herpes simplex virus (HSV) envelope glycoprotein D (gD) wherein the modified HSV gD protein is modified so that at least one of the B cell epitopes (decotopes) having low or no neutralizing antibody-inducing activity does not function as an epitope as compared to B cell epitopes present in the receptor-binding domain (RBD) in the ectodomain of wild type HSV gD.