Differential Activation of NLRP3, AIM2, and IFI16 Inflammasomes in Humans with Acute and Chronic Hepatitis B

Abstract

Nod-like receptor protein 3 (NLRP3), absent in melanoma 2 (AIM2), and interferon gamma inducible protein 16 (IFI16) are innate immune sensors for intracellular microbes, which can be activated by various dangerous signals and subsequently lead to caspase-1 (CASP1) activation and the maturation cleavage of effector molecules pro-IL-1β and pro-IL-18. Their roles in immunopathology of acute and chronic hepatitis B virus (HBV) infection are still unclear. In this study, we first investigated the activation of NLRP3, AIM2, and IFI16 inflammasomes in peripheral blood mononuclear cells (PBMCs) from patients infected with acute hepatitis B (AHB) and chronic hepatitis B (CHB) by quantitative real-time PCR and enzyme-linked immunosorbent assay. We next analyzed the impact of hepatitis B e antigen (HBeAg) on activation of AIM2 and IFI16 inflammasomes in PBMCs of CHB patients stimulated in vitro with AIM2 and IFI16 agonist ligands, poly (dA:dT) and VACA-70mer, respectively. The results showed that the mRNA expression levels of AIM2, IFI16, and CASP1 in PBMCs from AHB and CHB patients were both upregulated. Furthermore, the mRNA levels of AIM2 and IFI16 in CHB patients were significantly positively correlated with serum HBV loads. However, only in patients with AHB there was elevation of serum IL-1β and IL-18. There was no activation of NLRP3, AIM2, and IFI16 inflammasomes in CHB patients. Stimulation of PBMCs of CHB patients in vitro with poly (dA:dT) and VACA-70mer induced the activation of AIM2 and IFI16 inflammasomes, respectively. This ligand-induced activation was suppressed by HBeAg. Our results suggest that there exists activation of the AIM2 and IFI16 inflammasomes, but not the NLRP3 inflammasome, in AHB, and the activation of the AIM2 and IFI16 inflammasomes can be inhibited by HBeAg in CHB, which may contribute to HBV-induced immunotolerance.