Systematic evaluation of HSV-1 Δ34.5Δ47 as a dual-function platform for attenuated HSV-1 vaccine and heterologous antigen delivery.

Herpes simplex virus type 1 (HSV-1) causes lifelong latent infection and is associated with severe diseases, including herpes simplex encephalitis, neonatal herpes, and no licensed vaccine is currently available for this pathogen. Here, we systematically evaluated an attenuated HSV-1 platform with deletions in ICP34.5 and ICP47 genes (HSV-1 Δ34.5Δ47) for application as a dual-function vaccine. This construct, generated by BAC-galK recombination, showed attenuated replication in vitro. Notably, it elicited robust humoral and cellular immune responses in mice, and provided complete protection against lethal challenge with virulent HSV-1 McKrae strain through both corneal and genital tract infection routes. To assess its utility for heterologous antigen delivery, we engineered a recombinant HSV-1 Δ34.5Δ47-N, which expresses the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein. This recombinant virus retained the protective efficacy against HSV-1 and induced robust N-specific immune responses. Passive serum transfer and in vivo T-cell depletion studies demonstrated that humoral immunity was sufficient to mediate protective immunity against HSV-1 challenge. Safety assessment revealed no detectable viral mRNA or pathological lesions in the brains of immunized animals. These findings support HSV-1 Δ34.5Δ47 as a safe and versatile platform for both HSV-1 prophylaxis and heterologous antigen delivery.