Elevated Levels of Serum Interleukin-37 in Chronic Hepatitis B in Comparison with the Spontaneously Cleared and Healthy Control Groups

<b><i>Background:</i></b> Interleukin-37 (IL-37) can prevent liver damage and may be an important candidate for use as a novel therapeutic tool in hepatitis B virus (HBV) infection. This study aimed to evaluate the serum levels of IL-37 in individuals with chronic HBV (CHB) infection, those who spontaneously cleared (SC) HBV infection, compared with healthy control (HC) subjects. <b><i>Materials and Methods:</i></b> This case-control study included 30 patients with CHB (17 males, 13 females; mean age, 50.13 ± 14.51), 30 subjects with SC HBV infection (16 males, 14 females; mean age, 51.50 ± 16.85), and 42 HC subjects (22 males, 20 females; mean age, 53.52 ± 14.44). Blood samples were collected, and then serum IL-37 levels were measured using an enzyme-linked immunosorbent assay kit. <b><i>Results:</i></b> Our results showed that serum IL-37 levels were significantly higher in the CHB (96.99 ± 13.39 pg/mL) than in the HC group (37.85 ± 2.99 pg/mL, <i>p</i> = 0.02). No statistically significant differences were found in IL-37 serum levels between CHB group and SC group (91.93 ± 17.11 pg/mL, <i>p</i> = 0.43). Correlation analysis showed a significant negative correlation between serum IL-37 levels and age in SC subjects (<i>p</i> = 0.02, <i>R</i> = -0.42). <b><i>Conclusion:</i></b> Our results suggest that increased production of IL-37 may biologically act as a negative feedback loop to attenuate the release of pro-inflammatory cytokines and subsequently alleviate disease symptoms in CHB. The negative correlation between the cytokine and age may indicate that higher levels of IL-37 in younger individuals may lead to the spontaneous clearance of HBV.