Protection against herpes simplex virus type 2 infection in a neonatal murine model using a trivalent nucleoside-modified mRNA in lipid nanoparticle vaccine

Abstract

Neonatal herpes is a dreaded complication of genital herpes infection in pregnancy. We recently compared two vaccine platforms for preventing genital herpes in female mice and guinea pigs and determined that HSV-2 glycoproteins C, D and E expressed using nucleoside-modified mRNA in lipid nanoparticles provided better protection than the same antigens produced as baculovirus proteins and administered with CpG and alum. Here we evaluated mRNA and protein immunization for protection against neonatal herpes. Female mice were immunized prior to mating and newborns were infected intranasally with HSV-2. IgG binding and neutralizing antibody levels in mothers and newborns were comparable using the mRNA or protein vaccines. Both vaccines protected first and second litter newborns against disseminated infection based on virus titers in multiple organs. We conclude that both vaccines are efficacious at preventing neonatal herpes, which leaves the mRNA vaccine as our preferred candidate based on better protection against genital herpes.

Keywords: Genital herpes; Herpes simplex virus type 2; Maternal antibody; Neonatal herpes; Neutralizing antibody; Trivalent nucleoside-modified mRNA vaccine in lipid nanoparticles.

Graphical abstract

Fig. 1

Survival curves, colostrum and serum antibody titers. (A) Pups born to unimmunized dams were infected IN on PND 3 with media (n = 4 from one litter) or HSV-2 at 10⁴ PFU (n = 6 from three litters); 10³ PFU (n = 11 from two litters); or 10² PFU (n = 22 from four litters). (B) Pup colostrum gD2 IgG ELISA titers on PND 6 in neonates born to dams immunized with Poly(C) RNA, mRNA or protein (n = 10 pups for Poly(C) from three litters, n = 12 for trivalent mRNA from four litters, and n = 13 for trivalent protein from two litters). P values comparing Poly(C) RNA with trivalent mRNA or trivalent protein were calculated by the two-tailed Mann-Whitney test; ****p < 0.0001. Comparing mRNA with protein, P = 0.4667. (C) Neutralizing antibody titers in colostrum on PND 6 (n = 6 for Poly(C) RNA from two litters, n = 8 for trivalent mRNA from three litters, and n = 8 for trivalent protein from two litters). (D) Dam and pup serum ELISA gC2, gD2 and gE2 IgG. (E) HSV-2 serum neutralizing endpoint titers in PND 3 and PND 6–7 litters and their dams. The left panel is dams and their first-generation litters, while the right panel is dams and their second-generation litters. In (B-E) circles represent dams and squares pups. In (B and C) each symbol represents an individual animal and pups from the same litter are identified by the same filled, open or partially-filled symbol. Litter size in (D and E) is noted above the pup symbols. Blood from pups of the same litter were pooled.

Fig. 2

Organ virus titers of first and second litters on post-infection day 3. (A) First generation pups; n = 3 litters for Poly(C), n = 3 for mRNA, and n = 2 for protein. (B) Second generation pups; n = 1 litter for Poly(C), n = 3 for mRNA, and n = 3 for protein. Each symbol represents an individual organ from one pup. Pups with positive virus titers from the same litter are identified using the same filled, open or partially-filled symbol.