Characteristics Of T Cell Immunity In Chronic Hepatitis B Virus-infected Mothers Who Received Antiviral Intervention During Pregnancy

Background and AimsMother-to-child transmission(MTCT)is the most major transmission mode of hepatitis B virus(HBV)in China,and blocking MTCT is the key to eliminating hepatitis B.The clinical guidelines recommend that in the third trimester of pregnancy(gestational 24-28 weeks),chronic HBV-infected pregnant women with a high viral load(2×106IU/ml)should be treated with telbivudine or tenofovir as an intervention to reduce the incidence of MTCT.More and more clinical studies have proved that antiviral intervention during pregnancy was an effective and safe measure to block MTCT.However,some important issues related to antiviral intervention remain to be clarified.Firstly,the process of HBV infection and the outcome of the disease mainly depend on the interaction of viral factors and the host’s immune function,and whether antiviral intervention during pregnancy will affect the mother’s immune system?Secondly,it has been shown that a portion of mothers with antiviral intervention during pregnancy achieved HBeAg seroconversion over one year after delivery.What are the characteristics of HBV serology and immunology in mothers who achieved postpartum HBeAg seroconversion?Thirdly,some mothers with antiviral intervention during pregnancy will experience ALT flare after delivery.What is the immunological mechanism accounting for it?Method:Firstly,we performed a study by enrolling 49 HBsAg+/HBeAg+pregnant women at delivery,including 34 received antiviral intervention(intervention mothers)and 15 did not(non-intervention mothers),to analyzed whether antiviral interventions in the third trimester would affect maternal T cell immunity;And then we compared the differences of the phenotypes and functions of T cells between 20 intervention mothers and 6 non-intervntion mothers at the two follow-up points including at 6-8 weeks postpartum and 15-18 weeks postpartum,we investigated whether the effect of antiviral intervention on maternal T cells was reversible;Additional 20 HBsAg+/HBeAg+mothers with antiviral intervention were prospectively followed up during pregnancy and postpartum.Virological and serological indicators were observed,and phenotypes and functions of T lymphocytes were analysed by flow cytometry.Results:1.We found that Treg(CD4-+ CD25+Foxp3+)frequency in intervention mothers was significantly higher than that in non-intervention mothers at delivery(p=0.002).Compared to non-intervention mothers,the expression of activation molecules in CD4+T cells(CD69 and HLADR)obviously increased in the intervention mothers(p=0.039,p=0.026),but no similar expression was found in CD8+T cells.The expression of other phenotypes(CD62L,CD45RA,CXCR5,CD38,CTLA-4 and PD-1)showed no significant difference in CD4+T cells or CD8+T cells between the intervention and non-intervention mothers.Under anti-CD3/anti-CD28 stimulation,CD4+T cells from intervention mothers reduced the ability to secrete IFN-y and IL-21(p=0.005,p=0.043),and increased the ability to secrete Th2-type cytokines IL-10 and IL-4(p=0.040,p<0.001).For CD8+ T cells,the intervention mothers attenuated the secretion of IFN-y(p=0.028),but enhanced the ability to secrete IL-10 and IL-4(p=0.032,p= 0.011).2.Treg frequency in the intervention mothers was positively correlated with the frequency of CD4+IFN-y+T cells,CD4+IL-10+T cells or CD8+ IFN-γ+T cells respectively(p=0.027,r-0.386;p=0.014,r=0.425;p=0.040,r=0.354),and negatively correlated with the level of maternal HBsAg or HBeAg(p=0.0001,r=0.613;p=0.007,r=-0.451).3.At 6-8 weeks postpartum or at 15-18 weeks postpartum(after discontinuation of antiviral intervention),there was no significant difference in Treg frequency between the intervention mothers and the non-intervention mothers(p=0.882,p=0.614).Similarly,there was no significant difference in the ability of T cells of the two groups to secrete Th1 cytokines(IFN-y,TNF-α,IL-2)or Th2 cytokines(IL-10,IL-4)between the two groups at the two postnatal follow-up points(p>0.05).4.The level of HBsAg,HBeAg or HBV DNA in intervention mothers achieving postpartum HBeAg seroconversion(SC mothers)were lower than mothers without postpartum HBeAg seroconversion(NSC mothers).Notably,the levels of HBsAg in SC mothers were significantly lower than NSC mothers at all follow-up points.Dynamic change in Treg frequency was distinct in HBV-infected mothers with or without HBeAg seroconversion postpartum.SC mothers had a dynamic change of"increasing during antiviral intervention and decreasing after withdrawal of antiviral intervention",while dynamic change of Treg in NSC mothers exhibited a feature of"decreasing during antiviral intervemtion and increasing after withdrawal of antiviral intervention ".5.Compared with intervention mothers without ALT-flare(keep ALT<2×ULN after delivery;non-ALT-flare mothers)at postpartum,mothers with postpartum ALT-flare(experienced ALT≥2×ULN after delivery;ALT-flare mothers)had a lower Treg frequency before antiviral therapy,but no significant difference were found at subsequent follow-ups,including one month after antiviral intervention,delivery,6-8 weeks postpartum,and 15-18 weeks postpartum;Compared to non-ALT-flare mothers,CD4+ T cells or CD8+ T cells in ALT-flare mothers secreted more proinflammatory cytokines(IFN-y,IL21,IL2),and secreted less anti-inflammatory cytokines(IL10)before,during and after antiviral therapy.Conclusions:1.Antiviral intervention during pregnancy increased maternal Treg frequency,promotes maternal Th2 responses and suppresses maternal Thl responses at delivery,and the effects of antiviral intervention on maternal T cells was reversible after discontinuation of antiviral intervention.2.At delivery,the frequency of Treg in intervention mothers was positively correlated with IFN-y or IL10-secreting T cells;and maternal Treg frequency was negatively correlated with the level of maternal HBsAg and HBeAg.3.Dynamic changes in Treg frequency was distinct among intervention mothers with or without HBeAg seroconversion postpartum.Treg in mothers who achieved postpartum HBeAg seroconversion displayed a feature of increase during pregnancy and decrease postpartum.4.Postpartum ALT flare was related to the immunity of intervention mothers.The secretion of pro-inflammatory immunity was enhanced,while that of anti-inflammatory immunity was weakened,thus causing postpartum ALT flares.