Therapeutic effects of IL-6 and BAFF fusion protein eukaryotic expression plasmid on animal model of Sj?gren′s syndrome / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the effects of a eukaryotic expression plasmid for IL-6 and B-cell activating factor (BAFF) fusion protein on the histopathological changes in salivary and lacrimal glands of non-obese diabetic (NOD) mice with Sj?gren′s syndrome and to elucidate the possible therapeutic mechanism of IL-6/BAFF fusion protein eukaryotic expression plasmid in NOD mice.Methods:The eukaryotic expression plasmid for IL-6/BAFF fusion protein was constructed. After transfecting CHO cells with the plasmid, the expression of IL-6/BAFF fusion protein was detected by Western blot. BALB/c mice were injected with the plasmid every two weeks for three times and the titers of anti-IL-6 and anti-BAFF antibodies were measured by ELISA. Twenty-one NOD mice were randomly divided into three groups (control group, empty vector group and therapy group) by numerical table method. The mice in the therapy group were injected with the IL-6/BAFF fusion protein eukaryotic expression plasmid once a week for six times and the mice in the empty vector group were injected with empty plasmid. The levels of anti-IL-6 and anti-BAFF antibodies as well as cytokines (IL-6, BAFF, INF-γ, IL-10 and IL-17A) in mouse serum samples were detected by ELISA. The proportions of Th17, Treg, Th1 and Th2 cells in mouse splenocytes were measured by flow cytometry. Focal lymphocyte infiltration and pathological changes in the lacrimal and salivary glands of mice were observed under light microscopy after HE staining.Results:The eukaryotic expression plasmid for IL-6/BAFF fusion protein increased the levels of anti-IL-6 and anti-BAFF antibodies in the serum of BALB/c mice ( P<0.05). The levels of anti-IL-6 and anti-BAFF antibodies in the serum of NOD mice in the therapy group increased ( P<0.01), while the expression of IL-6, BAFF, INF-γ, IL-10 and IL-17A in NOD mice in the therapy group was lower than that in the control group and the empty vector group ( P<0.05). The percentages of Treg and Th2 cells in the splenocytes of NOD mice increased after treatment ( P<0.05). Moreover, the eukaryotic expression plasmid for IL-6/BAFF fusion protein significantly improved the irregular size and morphology of glandular vesicles in the lacrimal and salivary glands, reduced the ductal dilatation and decreased the focal lymphocyte infiltration in NOD mice. Conclusions:The eukaryotic expression plasmid for IL-6/BAFF fusion protein induced the production of anti-IL-6 and anti-BAFF antibodies, decreased the expression of inflammatory cytokines, regulated the balance of Th17/Treg and Th1/Th2 cells, improved the irregular alveolar structure and ductal dilation in the lacrimal and salivary glands and reduced the focal lymphocyte infiltration in NOD mice. This study showed that eukaryotic expression plasmid for IL-6/BAFF fusion protein might serve as a potential target for therapeutic targeting of T and B cells.