Predicting post partum hepatitis B virus flares using innate immune biomarkers.

Abstract

Aim: To examine innate immune function in chronically infected HBV pregnant women during and after pregnancy and correlate it with post-partum hepatic flares, +/- antiviral medications used to prevent vertical transmission. Background(s): Maternal tolerance to fetal antigens, gives way, post partum to immune system reconstitution and consequently in HBV infection to immune mediated hepatic flares., which can be life threatening to the mother. The characteristics of these immune changes and their impact and association with a variety of innate immunological and virological parameters is not well established. Method(s): Plasma and PBMCs were collected from patients at two sites at 5 different time points; first half of pregnancy, 3rd Trimester, 6 weeks post partum, 3 months post partum and 1 year post partum. TLR expression was measured on monocytes, NK cells and NK T cells by flow cytometry. PBMCs were also stimulated with TLR ligands LPS (TLR4), Pam3Cys (TLR2), CpG2006 (TLR9), PolyI:C (TLR3), R848 (TLR7/8) and assayed for cytokines by ELISA. NK cells (CD56 bright and 107A expresssion) were also examined to see if they are activated and able to kill hepatocytes using a TRAIL mediated mechanism. HBV viral load, quantitative HBeAg and HBsAg were also done at each timepoint. Result(s): 127 women were recruited 23% were HbeAg positive and 28% had a hepatitis flare (>2 ULN). Our results of 101 patients demonstrate elevated TLR2 expression in both monocytes (p < 0.02) and NK cells (p < 0.01) with increased specific TLR2 (P < 0.04) cytokine production, occurring in the third trimester in patients who developed post partum flares, with and without an increase in viral load. Activated NK cells overexpressed TRAIL and conditioned media from these patients caused caspase associated apoptosis of both hepatic cell lines and primary hepatocytes. Conclusion(s): These data demonstrate the importance of innate immune responses in relation to pregnancy-associated HBV flares. Cytokines may be driven by various TLRs and in turn activate TRAIL mediated mechanisms of apoptosis of hepatocytes leading to fibrosis. These results can also help elucidate the underlying mechanisms of HBV flares and serve as a model for dynamic alterations in ALT elevations and liver inflammation of HBVassociated flares in general.