A Multiepitope Intranasal Adenoviral Vaccine Induces Robust Mucosal Immunity and Protection against SARS‑CoV‑2

Area of Science:

• Immunology
• Vaccinology
• Virology

Background:

• Current COVID-19 vaccines targeting Spike protein are less effective against emerging SARS-CoV-2 variants of concern.
• Next-generation vaccines are needed for broad, variant-independent protection against SARS-CoV-2.
• Adenoviral vectors offer a platform for delivering conserved viral antigens.

Purpose of the Study:

• To evaluate a heterologous intranasal prime-boost vaccination strategy using adenoviral vectors.
• To assess the efficacy of constructs expressing Spike S1 subunit combined with full-length or multiepitope membrane (M) and nucleocapsid (N) proteins.
• To enhance antigen-specific T-cell responses using an autophagy-inducing peptide (AIP-C5).

Main Methods:

• Intranasal prime-boost vaccination in mice using bovine and chimpanzee adenoviral vectors expressing SARS-CoV-2 antigens.
• Formulations included Spike S1 subunit with either full-length M and N proteins or M and N-derived multiepitope constructs.
• Evaluation of humoral and cellular immune responses, neutralizing antibody titers, and protection against viral challenge.

Main Results:

• The multiepitope construct (Ad-S1+Epi/N+Epi/M) induced robust S1, N, and M-specific immunity, comparable or superior to the full-length construct.
• All S1-containing formulations generated high neutralizing antibody titers against Omicron B.1.1.529 and BA.2.86 variants.
• Intranasal immunization with S1-expressing vectors provided near-complete protection against BA.2.86 challenge in K18-hACE2 mice, with undetectable viral loads.

Conclusions:

• An intranasal multiepitope adenoviral vaccine incorporating conserved SARS-CoV-2 antigens induces robust mucosal, humoral, and cellular immune responses.
• This vaccination strategy confers significant protection against SARS-CoV-2 challenge.
• Adenoviral vector-based intranasal vaccines represent a promising approach for next-generation COVID-19 vaccines.