Deficiency of IL-20 receptor subunit A decreases enterovirus A71 lethality of mice with increases of M1 macrophage polarization and cytokine

SHUN-HUA CHEN^1*Cheng-Huei Hung²Yi-Ling Hsiao²Yi-Ping Tsai¹Ming-Shi Chang³Ching-Chuan Liu⁴Li-Chiu Wang^5*

• ¹Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
• ²Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
• ³Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
• ⁴Department of Pediatrics, National Cheng Kung University Hospital, Tainan City, Taiwan
• ⁵National Chung Hsing University Department of Post-Baccalaureate Medicine, Taichung, Taiwan

Introduction: Enterovirus A71 (EV-A71) can cause fatality in patients with increases of cytokines, IL-10, IL-12, and IFN-γ, which are mutually regulated. IFN-γ is induced to protect mice from EV-A71 infection, but its regulation remains elusive. The IL-10 family cytokines, IL-19, IL-20, and IL-24, which signal through the two-subunit receptor complex with IL-20RA as one subunit, are designated as IL-20RA cytokines. IL-20RA cytokines are shown to regulate IFN-γ and IL-10 in vitro. We designated this study to address the internation and role of IL-20RA cytokines in viral infections in vivo, which remain unknown. Methods: Plasma from heathy donors or EV-A71-infected patients were used to detect IL-20RA cytokines. Wild-type (WT) mice and IL-20RA knockout (IL-20RA-/-) mice as well as T cells and macrophages isolated from mice were used for study. Results: In plasmas, IL-19 was detected in healthy controls, and EV-A71 infection increased the IL-19 level of infected patients. In sera of WT mice, IL-20RA cytokines, but not IL-10, IL-12, and IFN-γ, were detected in mock-infected mice, and EV-A71 infection significantly and slightly enhanced IL-19 and IL-20 levels, respectively. Compared to WT mice, IL-20RA-/- mice were resistant to EV-A71 infection with reduced viral loads in peripheral organs, such as the spleen. In sera of infected mice, IL-20RA deficiency sequentially reduced the IL-10 level, but increased IL-12 and IFN-γ levels. Abundant T cells expressed IL-10 in splenocytes of infected WT mice. Abundant macrophages expressed IL-12 and IFN-γ in splenocytes of infected IL-20RA-/- mice. Notably, IL-20RA deficiency reduced M2 macrophages, but increased M1 macrophages, in splenocytes of infected mice. In vitro study using leukocytes isolated from WT mice confirmed that treatment with IL-19 or IL-20, but not IL-24, increased IL-10 production in CD4 T cells, but reduced IL-12 production in macrophages. Discussion: EV-A71 infection enhances IL-20RA cytokines, which increase viral loads to aggravate virus-induced diseases in WT mice with an elevated axis of T cell-IL-10-M2 macrophage to suppress the protective axis of M1 macrophage-IL-12- macrophage-IFN-γ, in a novel mechanism unreported before.