Investigation of IL-35 and IL-39, New Members of the IL-12 Family, in Different Clinical Presentations of Brucellosis

Brucellosis is significantly influenced by the interactions between the causative Brucella bacteria and host immunity. Recently identified cytokines have been described for their immunomodulatory effects in numerous inflammatory, autoimmune and infectious diseases. Some of them are new members of cytokine superfamilies, including several members of the IL-12 superfamily (IL-35, IL-39). The major purpose of the present study was to investigate the role of these new immunomodulatory cytokines in Brucella infections. The levels of IL-35 and IL-39 in the serum of 40 acute and 40 chronic brucellosis patients and 40 healthy controls were measured by ELISA. The mRNA levels of IL-35 and IL-39 in PBMCs were detected by RT-qPCR. Both IL-35 and IL-39 serum concentrations were significantly higher in healthy control subjects than in brucellosis patients, and IL-35 and IL-39 serum levels of chronic brucellosis patients were higher than those of acute cases. It was also found that the expression of Ebi3/IL-12A (IL-35 genes) and Ebi3/IL-23A (IL-39 genes) was upregulated in chronic brucellosis patients compared to healthy controls. Moreover, the expression of the Ebi3/IL-12A and Ebi3/IL-23A genes was lower in patients with acute brucellosis than in patients with chronic brucellosis. Overall, this study showed that IL-35 and IL-39 are positively correlated in brucellosis and significantly decreased during the disease. Significantly lower levels of IL-35 and IL-39 in acute brucellosis than in chronic brucellosis and healthy controls suggest that these cytokines may play a key role in suppressing the immune response to brucellosis and its progression to chronicity.