Structure-based design of soluble prefusion-stabilized herpes simplex virus type 2 glycoprotein B antigens.

Herpes simplex virus type 2 (HSV-2) infection causes recurrent genital herpes throughout life, yet no vaccines have been approved. Glycoprotein B (gB) is a class III fusion protein that mediates HSV-2 entry by transitioning from a metastable prefusion conformation to a stable postfusion conformation. Here, using structure-based design, we stabilize HSV-2 gB in its prefusion conformation. A 2.8 Å resolution cryo-EM structure reveals a closed state of prefusion gB, which differs from recently published open states. Vaccination of mice with protein subunit and mRNA-based vaccines of pre- and postfusion gB variants elicits robust humoral and cellular responses. Although prefusion stabilization of gB does not improve neutralizing antibody titers relative to the postfusion construct, prefusion gB elicits antibodies exhibiting higher FcγR-mediated effector activities. Collectively, these findings reveal insights into prefusion gB conformational dynamics, provide stabilized reagents for studying gB-directed immune responses, and inform HSV-2 vaccine design.