Journal of Vaccine Research 2024, Vol.14, No.4, 157-169 http://medscipublisher.com/index.php/jvr 162 Figure 1 cGAMP MPs provide long term protection against lethal influenza challenge (Adapted from Junkins et al., 2018) Note: Note: In experiments involving mice vaccinated with cGAMP MPs and soluble cGAMP, the results showed that mice receiving cGAMP MPs maintained strong body weight and complete protection even after seven months, whereas the control and other groups exhibited poorer outcomes. This indicates that cGAMP MPs not only provide long-lasting immune protection but also significantly enhance vaccine efficacy (Adapted from Junkins et al., 2018). 5.2 Delivery platforms The development of effective delivery platforms is essential for the success of adjuvants, as these platforms ensure that the adjuvants and antigens are delivered to the appropriate cells in the immune system. Nanoparticle-based delivery systems have gained attention due to their ability to mimic pathogen-associated molecular patterns (PAMPs), enhancing both innate and adaptive immune responses. For instance, nanoparticle vaccines based on bacteriophage T4 have shown potential in eliciting strong immune responses without the need for additional adjuvants, suggesting that these platforms could be used to deliver conserved influenza antigens (Tao et al., 2019). Moreover, recent studies have demonstrated that nanoparticle size and surface coating significantly influence the uptake and processing of antigens by dendritic cells, which are critical for initiating immune responses (Chang et al., 2017). These findings underscore the importance of optimizing delivery platforms to enhance the efficacy of molecular adjuvants and the overall vaccine formulation. 5.3 AS03 and other adjuvants AS03, an oil-in-water emulsion adjuvant, has been widely studied and used in influenza vaccines, particularly during the H1N1 pandemic. This adjuvant is known for its ability to enhance both humoral and cellular immune responses, making it a key component in the development of more effective influenza vaccines. Studies have shown that AS03 significantly boosts the production of antibodies, including those against conserved epitopes such as the hemagglutinin (HA) stem, which is critical for cross-protection against various influenza strains. Furthermore, AS03 has been shown to modulate early innate immune responses, including the activation of interferon and JAK-STAT signaling pathways, which are crucial for a robust adaptive immune response (Howard et al., 2019). Additionally, AS03's ability to enhance the immunogenicity of low-dose vaccines makes it an attractive option for dose-sparing strategies, which are particularly valuable in pandemic settings (Yam et al., 2015). Beyond AS03, other adjuvants such as MF59, QS-21, and CpG oligodeoxynucleotides are also being explored for their potential to improve influenza vaccine efficacy. These adjuvants offer different mechanisms of action, such
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