Background and aims Viral myocarditis is an inflammatory pathology of the myocardium that involves innate immune responses, especially those involving neutrophils. However, strategies targeting neutrophils to alleviate inflammation have not achieved complete success. Alpha lipoic acid (ALA), a natural organosulfur compound, has the capacity to modulate immune cell behavior. This study aimed to investigate whether ALAs can regulate innate immunity to provide protection against coxsackievirus B3 (CVB3)-induced myocarditis. Methods and results Abdominal administration of ALA improved cardiac dysfunction and reduced mortality in a CVB3-induced mouse model of myocarditis (VM). ALA treatment induced neutrophils and inhibited Ly6C hi pro-inflammatory macrophages, favoring a reparatory environment in the myocardium. However, depleting neutrophils with anti-Ly6G antibodies increased Ly6C hi pro-inflammatory macrophage recruitment in blood and heart in ALA-treated VM mice. Further flow cytometry analysis indicated that ALA promoted Ym-1 expression of neutrophils. Blocking Ym-1 significantly reversed ALA-mediated cardiac reparative macrophages infiltration and cardiac function improvement post-VM. Recombinant Ym-1 drives macrophages toward a reparative phenotype and attenuates CVB3-induced viral myocarditis. Mechanistically, ALA reprogrammed neutrophil metabolic patterns, leading to increased production of the metabolite acetyl-CoA, thereby increasing the transcription of Ym-1 by promoting STAT6 acetylation. Conclusions ALA protects against VM by activating metabolic reprogramming/STAT6 acetylation/Ym-1 axis in neutrophils. These results highlight the heterogeneity of neutrophils and suggest that ALA might represent a feasible strategy to improve the prognosis of VM patients.
The induction of a robust CD8 + T cell response is critical for the success of an antiviral vaccine. In this study, we incorporated a STING agonist (SA) 2′3’-cGAMP into a previously developed exosome-based CVB3 viral myocarditis vaccine (Exo-VP1) to enhance its ability to induce CD8 + T cell responses and immunoprotection. Our results showed that compared to free SA adjuvant, exosome-mediated co-delivery (Exo SA -VP1) significantly enhanced SA uptake by dendritic cells (DCs) and more potently stimulated DC maturation. Immunization of mice showed that the Exo SA -VP1 vaccine-induced higher levels of CVB3-specific T cell proliferation and cytotoxicity, significantly increased the percentage of IFN-γ + CD8 + rather than CD4 + T cells, effectively reduced cardiac viral loads, attenuated myocarditis and improved survival in mice compared to the previous Exo-VP1 vaccine. Further investigation showed that Exo SA -VP1 significantly increased both the percentage and antigen cross-presentation capacity of splenic CD8 + DCs. Depletion of these CD8 + DCs by cytochrome C administration nearly abolished the advantage of Exo SA -VP1 in dominantly inducing IFN-γ + CD8 + cytotoxic T lymphocyte (CTL) production in immunized mice. Taken together, our results demonstrated the potential of Exo SA -VP1 as a promising candidate for anti-CVB3 vaccines and provide insights into immune-enhancing strategies aiming at augmenting antigen cross-presentation by DCs and enhancing potent CTL responses.
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