Prefusion-specific glycoprotein B human antibodies protect against neonatal HSV-2 infection

Herpes simplex virus (HSV) can cause severe perinatal viral infections, leading to mortality or long-term neurological disability1,2. To date, antivirals have limited efficacy, and no vaccines are approved3,4. HSV entry requires the coordinated action of multiple viral glycoproteins. Glycoprotein B (gB), the most conserved glycoprotein among herpesviruses, mediates membrane fusion by undergoing a conformational transition from a metastable prefusion state to a stable postfusion state5. Potently neutralizing human antibodies targeting prefusion-specific epitopes have been identified for many virus families6-10, however, such antibodies for human herpesviruses are currently limited to an alpaca-derived nanobody and a murine monoclonal antibody11,12. In this study, we used stabilized HSV-2 prefusion gB and LIBRA-seq single-cell sequencing technology13 to probe B cells from HSV-2 seropositive and healthy human donors, resulting in the isolation of four prefusion-specific and two prefusion-preferring human antibodies. Cryo-EM studies revealed that the four prefusion-specific antibodies bind distinct epitopes on prefusion gB and exhibit different mechanisms of prefusion specificity. Two antibodies, 5-18 and 3-6, showed potent cross-neutralizing activity against HSV-1 and HSV-2 and conferred protection in a neonatal mouse model of HSV-2 infection. These findings highlight the molecular and structural determinants of HSV-2 prefusion gB recognition by human antibodies and demonstrate the translational potential of prefusion-specific gB antibodies.