Antibody Response and Protective Capacity of Plasmid Vaccines Expressing Three Different Herpes Simplex Virus Glycoproteins

Plasmid expression vectors were constructed that contained the genes encoding herpes simplex virus 1 (HSV-1) glycoproteins C (gC), D (gD), and E (gE). Mice receiving two intramuscular injections of expression plasmid (50 microg) produced a specific HSV-1 antibody response. Mice receiving the gD plasmid were protected against a lethal intraperitoneal challenge of HSV-1 (5 x 10(4) pfu) but not against more demanding challenge doses. Protection with gC or gE plasmid vaccination could be demonstrated only if the inoculating dose of DNA was increased to 250 microg. In contrast, all mice immunized with vaccinia recombinants expressing either gC or gE survived HSV-1 challenge. Analysis of the HSV-1 antibody isotype produced by plasmid immunization revealed a response dominated by IgG2a. Combination delivery of all three glycoprotein expression plasmids provided better protection against lethal challenge, but mice receiving the combination were still not able to withstand increased challenge doses of virus.