During productive viral infection the host cell is confronted with synthesis of a vast amount of viral proteins which must be folded, quality controlled, assembled and secreted, perturbing the normal function of the endoplasmic reticulum (ER). To counteract the ER stress, cells activate specific signaling pathways, designated as the unfolded proteins response (UPR), which essentially increase their folding capacity, arrest protein translation, and degrade the excess of misfolded proteins. This cellular defense mechanism may, in turn, affect significantly the virus life-cycle. This review highlights the current understanding of the mechanisms of the ER stress activation by Human Hepatitis B virus (HBV), a deadly pathogen affecting more than 350 million people worldwide. Further discussion addresses the latest discoveries regarding the adaptive strategies developed by HBV to manipulate the UPR for its own benefits, the controversies in the field and future perspectives.

Anemia is a very common occurrence during pregnancy, with important variations during each trimester. Anemia was also considered as a risk factor for severity and negative outcomes in patients with SARS-CoV-2 infection. As the COVID-19 pandemic poses a significant threat for pregnant women in terms of infection risk and access to care, we developed a study to determine the impact of nutritional supplementation for iron deficiency anemia in correlation with the status of SARS-CoV-2 infection. In a case-control design, we identified 446 pregnancies that matched our inclusion criteria from the hospital database. The cases and controls were stratified by SARS-CoV-2 infection history to observe the association between exposure and outcomes in both the mother and the newborn. A total of 95 pregnant women were diagnosed with COVID-19, having a significantly higher proportion of iron deficiency anemia. Low birth weight, prematurity, and lower APGAR scores were statistically more often occurring in the COVID-19 group. Birth weight showed a wide variation by nutritional supplementation during pregnancy. A daily combination of iron and folate was the optimal choice to normalize the weight at birth. The complete blood count and laboratory studies for iron deficiency showed significantly decreased levels in association with SARS-CoV-2 exposure. Puerperal infection, emergency c-section, and small for gestational age were strongly associated with anemia in patients with COVID-19. It is imperative to screen for iron and folate deficiency in pregnancies at risk for complications, and it is recommended to supplement the nutritional intake of these two to promote the normal development and growth of the newborn and avoid multiple complications during pregnancy in the COVID-19 pandemic setting.

Cells replicating the human hepatitis B virus (HBV) express high levels of degradation-enhancing α-mannosidase-like proteins (EDEMs), a family of proteins involved in the endoplasmic reticulum associated degradation, one of the pathways activated during the unfolded protein response. Owing to their α-1,2 mannosidase activity, the EDEM1-3 proteins are able to process the N-linked glycans of misfolded or incompletely folded proteins, providing the recognition signal for their subsequent degradation. The HBV small (S), medium (M), and large (L) surface proteins bear an N-linked glycosylation site in the common S domain that is partially occupied in all proteins. The M protein contains an additional site in its preS2 domain, which is always functional. Here, we report that these oligosaccharides are processed by EDEMs, more efficiently by EDEM3, which induces degradation of L and S proteins, accompanied by a reduction of subviral particles production. In striking contrast, M not only is spared from degradation but its trafficking is also accelerated leading to an improved secretion. This unusual behavior of the M protein requires strictly the mannose trimming of the preS2 N-linked glycan. Furthermore, we show that HBV secretion is significantly inhibited under strong endoplasmic reticulum stress conditions when M expression is prevented by mutagenesis of the viral genome. These observations unfold unique properties of the M protein in the HBV life cycle during unfolded protein response and point to alternative mechanisms employed by EDEMs to alleviate this stress in case of necessity by promoting glycoprotein trafficking rather than degradation.

The bipotent nature of the HepaRG cell line is a unique property among human hepatoma-derived cells. Cell treatment with specific differentiation inducers results in a mixture of hepatocyte- and biliary-like cells, accompanied by upregulation of liver-specific proteins, drug metabolizing enzymes, transcription regulators, membrane receptors or innate immune response effectors. These features make the HepaRG cells a suitable and handy replacement for primary hepatocytes, to study hepatic functions in vitro. However, cell differentiation is a long, variable process, requiring special culture conditions, while the resulting mixed cell populations is usually a major drawback. This process can potentially be controlled by interface characteristics, such as substrate topography. To screen for such novel substrates, we have first developed a new HepaRG cell line, designated as HepaRG, expressing the reporter gene DsRed. The fluorescent protein was expressed in hepatocyte- and not biliary-like cells, in a differentiation dependent-manner. We have further used replicated microstructured gradients of polydimethylsiloxane (PDMS) that allow three-dimensional manipulation in vitro, to monitor HepaRG differentiation in real time. We demonstrate that this approach enables the controlled assembly of viable hepatocyte-like cells for functional studies, which can be maintained in culture without loss of differentiation. The regulated expression of the DsRed reporter proved a valuable tool not only for rapid screening of novel cell growth substrates favoring cell differentiation, but also, to enrich the hepatocyte-like cell population by fluorescence-activated cell sorting to investigate liver-specific processes in vitro.

Background: Liver cells represent an attractive source of cells for autologous regenerative medicine. The present study assesses the liver cells’ stability during in vitro expansion, as a prerequisite for therapeutic use. Results: The human liver cell cultures in this study were propagated efficiently in vitro for at least 12 passages. No significant changes in morphology, intracellular ultrastructures and characteristic markers expression were found during in vitro expansion of cells from all analyzed donors. However, expanded cells derived from male donors of >60 years old, lost the Y chromosome. Conclusion: Liver-derived cell cultures adopt a proliferative, stable mesenchymal phenotype, through an epithelial to mesenchymal transition process. The molecular and phenotypic changes of the cells during propagation are uniform, despite the heterogeneity of the different donors. Loss of Y chromosome occurs after cells’ propagation in elder male donors.

No abstract

Hepatitis B virus (HBV) is an oncogenic virus known to contribute to hepatocellular carcinoma (HCC) development through a variety of mechanisms such as activation of the innate immune response triggering inflammatory signaling in liver cells; integration of HBV-DNA into the host genome, leading to genetic modifications; the ER stress induced by accumulation of viral proteins and the modulation of signaling pathways involved in cell cycle and proliferation by viral proteins. The scientific evidence is mainly focused on its implication in hepatic cancer, but several clinical and epidemiological studies support a role for HBV in extrahepatic diseases, such as B-cell non-Hodgkin lymphoma (B-NHL) occurrence. However, the mechanistic association between the HBV infection, the onset and progression of lymphoma remains unclear at the moment.

No abstract