Innovative use of gram-positive enhancer matrix particles and affinity peptides in a vaccine against Coxsackievirus B3.

Viral myocarditis (VM) is an inflammatory disease posing a serious threat to public health, with various viral pathogens contributing to its pathogenesis. Coxsackievirus B3 (CVB3) is the most frequently implicated causative agent and has been extensively studied because of its high prevalence and severity. No specific therapeutic interventions for VM exist, and vaccine development has encountered substantial challenges. Therefore, we aimed to develop a novel CVB3 mucosal vaccine as a preventive strategy against VM. Gram-positive enhancer matrice (GEM) particles serve as innovative mucosal vaccine adjuvants and antigen delivery systems that enhance antigen immunogenicity by facilitating effective mucosal immune responses. In this study, GEM particle display technology was used to develop two novel CVB3 vaccines: (1) a GEM particle-based vaccine displaying the CVB3 capsid protein VP1 via a PA anchor protein (GEM-PA-VP1), and (2) a GEM particle-based vaccine displaying VP1 via the FcSP peptide (GEM-Fc-VP1). Both GEM-PA-VP1 and GEM-Fc-VP1 vaacines significantly elevated levels of specific IgG, IgG1, IgG2a, sIgA and neutralizing antibodies in a mouse model, along with enhanced secretion of Th1- and Th2-associated cytokines, compared to controls. Notably, GEM-Fc-VP1 demonstrated superior immunogenicity compared with that of GEM-PA-VP1, evidenced by higher antibody titres and cytokine responses. In challenge protection experiments, both vaccines significantly improved survival rates, reduced myocardial enzyme levels, and decreased inflammatory cell infiltration in myocardial tissue, with GEM-Fc-VP1 exhibiting greater efficacy. These findings establish a foundation for the development of a safe and effective CVB3 candidate vaccine and provide novel insights into the potential of peptide-mediated subunit vaccine approaches.