Placenta as a site of HEV replication and inflammatory cytokines modulating the immunopathogenesis of HEV in pregnant women

Abstract

Viral hepatitis E is an under-estimated clinical entity with high mortality (20%-30%), especially in the third trimester of pregnancy. As complications due to hepatitis E virus (HEV) in pregnancy is much greater, it is hypothesized that HEV may cross the placenta and replicate in placental tissues even weeks after clearance from the blood, and cytokines may play a role in the immunopathogenesis of HEV in pregnancy. A total of 12 pregnant women with features of acute viral hepatitis/ acute liver failure and positive for either HEV-immunoglobulin M (IgM)/HEV-RNA and 30 pregnant women negative for HEV RNA/IgM/immunoglobulin G were enrolled as study subjects and healthy controls, respectively. Following delivery, 5 ml blood was collected from the mother for HEV-RNA. Replicative RNA and viral load in placental tissue were detected through Real-Time PCR. Placental tissues from the maternal/fetal sides were stained for HEV antigen using HEV-open reading frame-2 antibody by immunohistochemistry (IHC) and for histopathological changes by haematoxylin and eosin. Plasma samples were tested for interleukin (IL)-1β and IL-18 cytokine levels using Duo-R&D ELISA kit, whereas peripheral blood mononuclear cells were used to study the inflammasomes and IL-1β and IL-18 cytokine genes expression.Of the 10 HEV RNA-positive sera, 9 had HEV RNA either in the maternal/fetal side of the placenta with the mean viral load of 137.4 IU/ml. Of the 10 HEV RNA-positive pregnant women, stillbirth in two and fetal and maternal death in one case was reported. IHC revealed strong brownish cytoplasmic staining (HEV antigen) in cytotrophoblasts and syncytiotrophoblast cells in positive samples. The maternal/fetal side of the infected placenta showed irregular intervillous fibrin deposition as well as tissue necrosis. The mean levels of IL-1β and IL-18 cytokines in serum of infected subjects were significantly higher than the healthy controls (17.31 ± 4.462 vs. 8.85 ± 4.36 pg/ml; p < 0.0001*** and 2275 ± 536.9 vs. 1085 ± 531.7 pg/ml; p < 0.0001***), respectively. Detecting replicative HEV RNA and HEV antigen in placental tissues indicated the extra-hepatic replication of HEV. Furthermore, placental tissue necrosis and significant rise of cytokine levels in

Deregulation of immune response contributing to fulminant hepatitis in HEV infected pregnant women

“…P‐ALF presents lower counts of CD4 + T cells and higher counts of CD8 + T cells compared to other etiology induces ALF in pregnant women, indicating the involvement of T cells in hepatic damage 10 . Complemental clinical investigation revealed that the cytokine levels, such as TNF‐α, IL‐6, and IFN‐γ, are higher in P‐ALF than in P‐nHEV, which are positively correlated to adverse outcomes 9,18 . Taken together, these investigations suggest that both inadequate immune responses and overactive inflammatory response after HEV infection lead to a poor prognosis in pregnant women.…”

“…10 Complemental clinical investigation revealed that the cytokine levels, such as TNF-α, IL-6, and IFN-γ, are higher in P-ALF than in P-nHEV, which are positively correlated to adverse outcomes. 9,18 Taken together, these investigations suggest that both inadequate immune responses and overactive inflammatory response after HEV infection lead to a poor prognosis in pregnant women.…”

“…17 Furthermore, interferon (IFN) response in placental cells is reported to be weaker than in hepatocytes during genotype 1 HEV infection, suggesting that genotype 1 HEV might be able to evade the early antiviral response in a certain amount of pregnant women and cause an adverse consequence. 18 These investigations point towards the possibility that pregnant women infected with HEV may trigger more extensive immune responses. Our results showed that the immune responses after HEV infection are similar between pregnant and non-pregnant population.…”

“…A shift from a Th1‐dominated immune response to a Th2‐dominated response, known as a “Th2 bias,” had been proposed during pregnancy, which was found to be more prominent in genotype 1 HEV infected pregnant women 17 . Furthermore, interferon (IFN) response in placental cells is reported to be weaker than in hepatocytes during genotype 1 HEV infection, suggesting that genotype 1 HEV might be able to evade the early antiviral response in a certain amount of pregnant women and cause an adverse consequence 18 . These investigations point towards the possibility that pregnant women infected with HEV may trigger more extensive immune responses.…”