First characterization of a teleost Epstein-Barr virus-induced gene 3 (EBI3) reveals a regulatory effect of EBI3 on the innate immune response of peripheral blood leukocytes

Epstein-Barr virus-induced gene 3 (EBI3) encodes a protein that in mammals is known to be a subunit of interleukin (IL)-27 and IL-35, both which regulate cytokine production and inflammatory response. To date, no studies on fish EBI3 have been documented. In this work, we report the identification of an EBI3 homologue, CsEBI3, from tongue sole (Cynoglossus semilaevis) and analysis of its expression and biological effect. CsEBI3 is composed of 245 amino acid residues and possesses a Fibronectin type 3 (FN3) domain that is preserved in lower and higher vertebrates. Expression of CsEBI3 was detected in a wide range of tissues, in particular those of immune relevant organs, and upregulated in a time-dependent manner by experimental challenge with bacterial and viral pathogens. Bacterial infection of peripheral blood leukocytes (PBL) enhanced CsEBI3 expression and caused extracellular secretion of CsEBI3. Purified recombinant CsEBI3 (rCsEBI3) stimulated the respiratory burst activity of PBL and upregulated the expression of IL-1β, IL-8, Myd88, interferon-induced gene 15, CD28, and chemokines. In contrast, rCsEBI3M, a mutant CsEBI3 that lacks the FN3 domain failed to activate PBL and induced much weaker expression of the immune genes. Treatment of PBL with rCsEBI3, but not with the mutant rCsEBI3M, enhanced cellular resistance against bacterial invasion, whereas antibody blocking of CsEBI3 on PBL significantly reduced cellular resistance against bacterial infection. Taken together, these results indicate for the first time that a teleost EBI3 possesses immunoregulatory property in a manner that is dependent on the conserved FN3 domain, and that CsEBI3 is involved in the innate immune defense of PBL against microbial pathogens.

Epstein-Barr virus-induced gene 3-deficiency leads to impaired antitumor T-cell responses and accelerated tumor growth

Epstein-Barr virus-induced gene 3 (EBI3) encoded protein can form heterodimers with IL-27P28, and IL-12P35 to form IL-27, and IL-35. However, IL-27 stimulates, whereas IL-35 inhibits antitumor T-cell responses. IL-27 also limits the Foxp3⁺ regulatory T cell (Treg) population, whereas IL-35 has been shown to expand Tregs and foster Treg suppressive functions. It remains unclear which group of forces are dominant during antitumor T-cell responses. In this study, we evaluated the tumor growth and antitumor T-cell responses in EBI3-deficient mice that lack both IL-27 and IL-35. We found that injecting B16 melanoma cells into EBI3-deficient C57BL/6 mice, or J558 plasmacytoma cells into EBI3-deficient BALB/c mice resulted in significantly increased tumor growth relative to those implanted in wild-type control mice. Tumors from EBI3-deficient mice contained significantly decreased proportions of CD8⁺ T cells and increased proportions of CD4⁺FoxP3⁺ Treg cells as compared to those from EBI3-intact mice. Tumor-infiltrating T cells from EBI3-deficient mice were impaired in their capacity to produce IFNγ. Phenotypically, Tregs from EBI3-deficient mice were highly suppressive and produced IL-10 in the tumor microenvironment. Depletion of Tregs or inactivation of the IL-10 pathway significantly abrogated tumor growth enhancement in Ebi3^-/- mice. Finally, we showed that Ebi3^-/- mice administered a melanoma vaccine failed to mount a CD8⁺ T-cell response and the vaccine failed to confer tumor rejection in EBI3-deficient mice. Taken together, these results suggest that Ebi3^-/- mice show a phenotype of IL-27-deficiency rather than IL-35-deficiency during anti-tumor T-cell responses. Thus, our results suggest that endogenous IL-27 is critical for both spontaneous and vaccine-induced antitumor T-cell responses.

Expression of Epstein-Barr virus-induced gene 3 in cervical cancer: Association with clinicopathological parameters and prognosis

Epstein-Barr virus-induced gene 3 (EBI3) encodes a secretory glycoprotein, and has previously been identified as upregulated in a series of cancers. However, the clinical significance of EBI3 in cervical cancer and the potential of EBI3 as a therapeutic target for this disease have not been elucidated. In the present study, EBI3 expression was analyzed by immunohistochemistry in 90 clinicopathologically characterized cervical cancer tissue samples. The association between EBI3 expression and survival of patients with cervical cancer was also analyzed. The expression level of EBI3 in cervical cancer tissues was found to be significantly increased compared with the expression levels in the normal squamous epithelium. In addition, EBI3 expression was significantly correlated with the clinical stage and size of tumors (P<0.05). Furthermore, the presence of EBI3 expression was associated with a poor prognosis compared with patients without EBI3 expression. Multivariate analysis revealed that EBI3 expression was an independent predictor of overall survival (hazard ratio, 4.032; 95% confidence interval, 1.538-7.436; P=0.035). To the best of our knowledge, the present results indicate for the first time that EBI3 expression is significantly associated with the progression and poor prognosis of cervical cancer. EBI3 may be a potential prognostic marker and a therapeutic target in cervical cancer.

Downregulation of Epstein-Barr virus-induced gene 3 is associated with poor prognosis of hepatocellular carcinoma after curative resection

Epstein-Barr virus-induced gene 3 (EBI3) encodes a secretory glycoprotein, and has previously been identified as upregulated in various types of tumors. The presnet study examined the clinical significance of EBI3 expression for predicting tumor recurrence and survival after resection in hepatocellular carcinoma (HCC). EBI3 expression in various HCC cell lines and in 20 pairs of tumor and peritumor tissue samples were detected using western blot analysis. Immunohistochemical staining using tissue microarray with 312 samples from randomly selected patients with HCC who underwent surgery. Survival analysis was performed using univariate and multivariate analyses. EBI3 protein level was higher in L-02 cells and in peri-tumor tissues compared with tumor tissues. Immunohistochemical staining of EBI3 was reduced in HCC tissues in comparison with adjacent normal tissues and significantly associated with tumor invasive characteristics, including tumor thrombus, poor differentiation and large size. Notably, the results suggested that EBI3 was a predictor for tumor recurrence and patient survival, and multivariate analysis indicated EBI3 to be an independent prognostic factor. Even in early-stage disease, low EBI3 expression was also independently associated with increased tumor recurrence and shortened survival. Downregulation of EBI3 in HCC indicated aggressive tumor behaviors and predicted a more severe clinical outcome, which suggests that EBI2 may be a useful biomarker to identify patients at high risk of post-operative recurrence.

Epstein-Barr virus-induced gene 3 (EBI3) single nucleotide polymorphisms and their association with central obesity and risk factors for cardiovascular disease: The GEA study

Obesity, a chronic low-grade inflammation metabolic abnormality, is related to high proinflammatory cytokines concentrations. Epstein-Barr virus-induced gene 3 (EBI3) encodes for the EBI3 beta subunit that constitutes interleukin (IL) 27 and 35. Our objective was to assess the association of three EBI3 single nucleotide polymorphisms (SNPs) with the presence of central obesity in a group of Mexican subjects. The rs428253, rs4740, and rs4905 EBI3 SNPs were genotyped in 1323 individuals (1092 central obese and 231 non-central obese). We also analyzed IL-6, IL-27, and IL-35 concentrations. Under different models, the rs4740 (OR = 0.384, P_recessive = 0.010; OR = 0.404, P_{codominant 2} = 0.019) and rs4905 (OR = 0.380, P_recessive = 0.009; OR = 0.404, P_{codominant 2} = 0.018) were related with a low risk of central obesity. In central obese subjects, the SNPs were related to lower risk of hypoalphalipoproteinemia (rs4740) and with high IL-6 concentrations (rs428253, rs4740, and rs4905), whereas in non-central obese individuals, the rs428253 was related with low risk of increased visceral abdominal fat and hypertriglyceridemia. Interleukin-6, IL-27 and IL-35 concentrations were similar in both groups and no relation was noticed with the studied genotypes. Our results suggest an association of EBI3 SNPs with a low risk of central obesity and with a few risk factors for cardiovascular disease in individuals with and without central obesity.