An Interleukin 12 Adjuvanted Herpes Simplex Virus 2 DNA Vaccine Is More Protective Than a Glycoprotein D Subunit Vaccine in a High-Dose Murine Challenge Model

Vaccination is a proven intervention against human viral diseases; however, success against Herpes Simplex Virus 2 (HSV-2) remains elusive. Most HSV-2 vaccines tested in humans to date contained just one or two immunogens, such as the virion attachment receptor glycoprotein D (gD) and/or the envelope fusion protein, glycoprotein B (gB). At least three factors may have contributed to the failures of subunit-based HSV-2 vaccines. First, immune responses directed against one or two viral antigens may lack sufficient antigenic breadth for efficacy. Second, the antibody responses elicited by these vaccines may have lacked necessary Fc-mediated effector functions. Third, these subunit vaccines may not have generated necessary protective cellular immune responses. We hypothesized that a polyvalent combination of HSV-2 antigens expressed from a DNA vaccine with an adjuvant that polarizes immune responses toward a T helper 1 (Th1) phenotype would compose a more effective vaccine. We demonstrate that delivery of DNA expressing full-length HSV-2 glycoprotein immunogens by electroporation with the adjuvant interleukin 12 (IL-12) generates substantially greater protection against a high-dose HSV-2 vaginal challenge than a recombinant gD subunit vaccine adjuvanted with alum and monophosphoryl lipid A (MPL). Our results further show that DNA vaccines targeting optimal combinations of surface glycoproteins provide better protection than gD alone and provide similar survival benefits and disease symptom reductions compared with a potent live attenuated HSV-2 0ΔNLS vaccine, but that mice vaccinated with HSV-2 0ΔNLS clear the virus much faster. Together, our data indicate that adjuvanted multivalent DNA vaccines hold promise for an effective HSV-2 vaccine, but that further improvements may be required.