Immunization with Herpes Simplex Virus Nanoparticles Targeting Both Attachment and Fusion Protect Against Infection.

Herpes simplex virus 2 (HSV-2) is associated with genital ulcers, neonatal encephalitis, increased risk of HIV infection, and dementia. There is no licensed HSV-2 vaccine. We developed nanoparticles displaying the HSV-2 attachment protein gD and fusion mediation protein complex gH/gL. Immunization of mice and non-human primates elicited high levels of neutralizing antibodies. Vaccination conferred robust protection in mice, preventing disease and nearly eliminating infection and shedding following HSV-2 challenge. While gD induced high neutralizing antibody titers, gH/gL contributed substantially to protection despite lower neutralization titers. Instead, gH/gL immunization generated strong fusion-blocking responses which were an important correlate of protection, showing that standard neutralization assays incompletely capture the importance of fusion-blocking activity. These findings demonstrate that targeting both HSV-2 attachment and fusion elicit complementary mechanisms for protection from infection and that neutralizing antibody alone may be insufficient for protection. Overall, these results present an innovative strategy for an HSV-2 vaccine.