We have shown previously that herpes simplex virus type 1 (HSV-1) glycoprotein H (gH) expressed by a baculovirus recombinant is transported to the cell surface in the absence of other HSV-1 gene products, and that the expressed gH has an apparent Mr similar to that of authentic HSV-1 gH. We report here that antibodies raised in mice to this baculovirus-expressed gH neutralize the infectivity of HSV-1 in vitro; this neutralizing activity was not complement-dependent. Mice vaccinated with gH also developed delayed type hypersensitivity (DTH) to HSV-1. This is the first report of expressed HSV-1 gH inducing neutralizing antibody or DTH responses in vaccinated animals. In contrast to the gH expressed in mammalian systems, the ability of this baculovirus-expressed gH to induce a neutralizing antibody response may be due to the inability of the mammalian expression system to transport gH to the cell surface. Despite inducing anti-HSV-1 neutralizing antibody and DTH responses, vaccination of mice with gH did not protect the mice against lethal intraperitoneal challenge with HSV-1.