A New RNA-Based Adjuvant Enhances Virus-Specific Vaccine Responses by Locally Triggering TLR- and RLH-Dependent...

Area of Science:

• Immunology
• Vaccinology
• Molecular Biology

Background:

• Adjuvants are crucial for enhancing vaccine efficacy.
• RNAdjuvant is a novel, uncapped, noncoding ssRNA adjuvant with polyU repeats, stabilized by a cationic peptide.
• It is designed to induce a Th1-shift in immune responses.

Purpose of the Study:

• To evaluate the adjuvant properties of RNAdjuvant in combination with influenza and vesicular stomatitis virus vaccines.
• To investigate the immune mechanisms underlying RNAdjuvant's effects.
• To assess the safety and tolerability profile of RNAdjuvant.

Main Methods:

• Vaccination of mice with influenza subunit vaccine or vesicular stomatitis virus-like particles with or without RNAdjuvant.
• Analysis of antibody isotypes (IgG1, IgG2b/c) and virus-neutralizing activity in sera.
• Assessment of dendritic cell activation markers and type I interferon (IFN-I) production.
• Evaluation of adjuvant effects in MyD88-/- and MyD88-/-Cardif-/- mice to determine the role of TLR and RIG-I-like helicase signaling.

Main Results:

• RNAdjuvant significantly enhanced virus-specific IgG1 and promoted IgG2b/c production, indicating a Th1-shift.
• Vaccination with RNAdjuvant conferred virus-neutralizing antibody responses and protection against lethal infection.
• RNAdjuvant induced dendritic cell activation and IFN-I production, dependent on TLR7 signaling.
• Augmented vaccine responses required concurrent TLR and RIG-I-like helicase signaling, as shown in MyD88-/-Cardif-/- mice.

Conclusions:

• RNAdjuvant effectively enhances vaccine-induced humoral immunity and Th1 responses.
• The adjuvant effect relies on a combination of TLR and RIG-I-like helicase signaling pathways.
• RNAdjuvant exhibits a favorable safety profile with localized IFN-I induction and no systemic effects.