Coxsackievirus B1 (CVB1), a member of the enterovirus B species, is a common cause of acute and chronic myocarditis, dilated cardiomyopathy, and purulent meningitis. However, there is currently no vaccine against CVB1. In June 2023, researchers from Tampere University published an article in Research Square comparing the structure and immunogenicity of CVB1 virus-like particles (VLPs) and inactivated whole-virus vaccine candidates, and exploring the potential of epigallocatechin-3-gallate (EGCG) as a vaccine adjuvant.

Production of CVB1-VLPs and Inactivated Vaccines

CVB1 belongs to six serotypes of enterovirus. CVB infections can lead to severe consequences, especially in immunocompromised individuals. To produce CVB1-VLPs, researchers used a baculovirus transfer vector containing the CVB1 VP0-3 polyprotein and 3CD protease genes and cultured them in insect cells to produce the VLPs. Inactivated CVB1 vaccines are produced using formalin, with CVB1 isolates serving as templates for both the inactivated vaccine and VLP production.

Evaluation of EGCG as a Vaccine Adjuvant

Although VLPs may perform better than traditional vaccine production methods, their immunogenicity can be weak, often requiring adjuvants to enhance effectiveness. EGCG, a polyphenol molecule found in green tea, has been studied for its antiviral properties and potential as a vaccine adjuvant. The study found that the use of Tween 80 during VLP purification significantly improved the stability and yield of CVB1-VLPs.

The study also evaluated the effect of EGCG and formalin-inactivated CVB1 vaccines via nasal instillation, comparing them with CVB1-VLPs alone or in combination with EGCG. The results showed that formalin-inactivated CVB1 induced a balanced immune response involving humoral, mucosal, and cellular immunity, making it a promising mucosal vaccine. In contrast, when CVB1-VLPs were used alone or in combination with EGCG, immune cells could uptake the VLPs, but new mucosal adjuvants were needed to enhance their immunogenicity.

CryoEM analysis was used to compare the structures of CVB1-VLPs and formalin-inactivated CVB1 particles used for nasal vaccination. The results revealed differences between the VLPs and natural CVB1 particles, providing a structural basis for understanding immunogenicity differences. Although VLPs have relatively low immunogenicity, their stability makes them valuable for vaccine development.

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Conclusion

This study provides new insights into the development of CVB1 vaccines, emphasizing the potential of formalin-inactivated CVB1 vaccines and VLP-based vaccines in mucosal immunity and highlighting the need for new mucosal adjuvants. Additionally, the potential of EGCG as a vaccine adjuvant warrants further investigation.

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