Immunogenicity of Varicella-Zoster Virus Glycoprotein E Formulated with Lipid Nanoparticles and Nucleic Immunostimulators in Mice

Abstract

Theoretically, the subunit herpes zoster vaccine Shingrix^TM could be used as a varicella vaccine that avoids the risk of developing shingles from vaccination, but bedside mixing strategies and the limited supply of the adjuvant component QS21 have made its application economically impracticable. With lipid nanoparticles (LNPs) that were approved by the FDA as vectors for severe acute respiratory syndrome coronavirus 2 vaccines, we designed a series of vaccines efficiently encapsulated with varicella-zoster virus glycoprotein E (VZV-gE) and nucleic acids including polyinosinic-polycytidylic acid (Poly I:C) and the natural phosphodiester CpG oligodeoxynucleotide (CpG ODN), which was approved by the FDA as an immunostimulator in a hepatitis B vaccine. Preclinical trial in mice showed that these LNP vaccines could induce VZV-gE IgG titers more than 16 times those induced by an alum adjuvant, and immunized serum could block in vitro infection completely at a dilution of 1:80, which indicated potential as a varicella vaccine. The magnitude of the cell-mediated immunity induced was generally more than 10 times that induced by the alum adjuvant, indicating potential as a zoster vaccine. These results showed that immunostimulatory nucleic acids together with LNPs have promise as safe and economical varicella and zoster vaccine candidates.

Keywords: CpG ODN (CpG oligodeoxynucleotide); Poly I:C (polyinosinic-polycytidylic acid); cell-mediated immunity; chickenpox; herpes zoster; herpesvirus 3; human; humoral immunity; lipid nanoparticle; nucleic acid immunostimulator; shingles; varicella.

Figure 1

Characterization of LNP vaccines. (A) gE concentration; (B) gE encapsulation efficiency; (C) Nucleic acid immunostimulator concentration; (D) Nucleic acid immunostimulator encapsulation efficiency; (E) Diameters tested by a size analyzer; (F) Polydispersity index of LNPs. **** p < 0.0001. ns, no significant difference.

Figure 2

Humoral immune responses. (A) gE-specific IgG titers; (B) gE-specific IgG1 titers; (C) gE-specific IgG2a titers; (D) IgG1/IgG2a ratios; (E) Neutralizing effects of serum from LNP-BW006+2395-gE-immunized mice. Scale bar, 2000 μm. ** p < 0.01. ns, no significant difference.

Figure 3

Enzyme-linked immunospot (ELISPOT) assay performed with splenocytes. (A) IFN-γ-producing splenocytes after gE stimulation; (B) IFN-γ-producing splenocytes after pooled peptide stimulation; (C) IL-2-producing splenocytes after gE stimulation; (D) IL-2-producing splenocytes after pooled peptide stimulation. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001. ns, no significant difference. ELISPOT numbers were compared using one-way analysis of variance (ANOVA) followed by Dunnett’s multiple comparisons test with the LNP-BW006+2395-gE group used as the control.