The Role Of Inflammasomes And DNA Sensors In Human Acute And Chronic Hepatitis B Virus Infection

BackgroundThe rate of chronicity after acute HBV infection is over 90%among children less than 1 year and is below 5%among infected adults.Therefore,whether or not acute HBV infection develops into chronicity is most closely related to the age of the infected person or the immune status of the host at that time.Numerous previous studies have shown that CD8+T lymphocyte-centered cytokine immunity and cytotoxicity play a central role in controlling the immune response to acute HBV infection.In contrast,research with respect to the role of innate immunity in HBV infection has been neglected.The canonical inflammasome is a protein complex composed of a pathogen sensor NLR or ALR,an adaptor molecule ASC and an effector enzyme caspase-1.Activation of inflammasomes promotes the maturation and release of IL-1β and IL-18,thus constituting the only IL-1β production pathway in vivo.Among the cytokines and interferons with antiHBV effects,IL-1β showed the strongest anti-HBV effects in vitro.At present,there are few studies on the roles of inflammasomes in HBV infection.Intracellular DNA sensors are responsible for recognizing cytoplasmic or nuclear exogenous DNA.When binding to foreign DNA,these DNA receptors activate the STING-TBK1-IRF3 pathway and induce the expression of type Ⅰ interferons and other cytokines,thus playing an important role in antiviral responses.There is much debate about whether HBV can be recognized by intracellular DNA sensors or HBV can actively evade the recognition pathway.Based on the above problems,we carried out relevant clinical studies to explore the immunopathological roles of inflammasomes and DNA sensors-STING pathways in acute and chronic HBV infection.AimsTo study the activation of inflammasomes in acute and chronic HBV infection and the possible mechanism that affects the activation,and the activation of DNA receptorSTING pathway and the effect of HBV infection on the activation of this signal pathway.Methods1.The expression levels of NLRP3,AIM2 and IFI16 inflammasome components in PBMCs from chronic hepatitis B patients(CHB),acute hepatitis B patients(AHB)and healthy controls(HC)were quantitatively analyzed by qPCR and ELISA,and their correlations with HBV infection were analyzed.PBMCs from CHB group were stimulated in vitro with inflammasome agonists,and the effect of HBeAg on activation of the signal pathway was analyzed.2.The expression levels of DNA sensors,STING and IFN-β mRNA in PBMCs from patients with AHB and chronic HBV infection at different clinical stages were quantitatively analyzed by qPCR.PBMCs were isolated into monocytes and nonmonocytes by immunomagnetic beads in vitro,and quantitative analysis by qPCR was performed to identify the cell sources of up-regulated DNA sensors.PBMCs and monocytes were stimulated by ligands in vitro，and activation profiles of the DNA sensor-STING pathway in HC,AHB and CHB groups were analyzed.Results1.The mRNA expression levels of IFI16,AIM2 and CASP1 in PBMCs were significantly upregulated in CHB and AHB group,while IL-1β and IL-18 were significantly upregulated only in AHB group.The mRNA expression levels of AIM2 and IFI16 in CHB group were significantly positively correlated with serum HBV DNA levels,while the IFI16 mRNA expression level was significantly negatively correlated with HBeAg level in CHB patients.The mRNA expression levels of AIM2,NLRP3 and CASP1 in PBMCs from CHB patients stimulated by Poly(dA:dT)or VACV ds 70mer with or without HBeAg did not change significantly,but the expression levels of IL-1β decreased significantly stimulated with HBeAg.2.IFI16 was significantly upregulated in AHB and CHB group,while STING was upregulated in all groups with chronic HBV infection.IFI16 was mainly expressed in CD14+monocytes,and the IFI16 mRNA expression level in CD14+monocytes from AHB group and CHB group was significantly higher than that in HC group.Both in PBMCs and monocytes stimulated by VACV ds 70mer,the mRNA expression levels of IFI16,STING and IFN-β in CHB group were significantly lower than those in HC group.ConclusionsHBV may be recognized by AIM2 and IFI16 in PBMCs and may also inhibit immune activation after innate immune recognition.