Rise in broadly cross-reactive adaptive immunity against human β-coronaviruses in MERS-recovered patients during the COVID-19 pandemic

To develop a universal coronavirus (CoV) vaccine, long-term immunity against multiple CoVs, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, Middle East respiratory syndrome (MERS)-CoV, and future CoV strains, is crucial. Following the 2015 Korean MERS outbreak, we conducted a long-term follow-up study and found that although neutralizing antibodies and memory T cells against MERS-CoV declined over 5 years, some recovered patients exhibited increased antibody levels during the COVID-19 pandemic. This likely resulted from cross-reactive immunity induced by SARS-CoV-2 vaccines or infections. A significant correlation in antibody responses across various CoVs indicates shared immunogenic epitopes. Two epitopes-the spike protein's stem helix and intracellular domain-were highly immunogenic after MERS-CoV infection and after SARS-CoV-2 vaccination or infection. In addition, memory T cell responses, especially polyfunctional CD4+ T cells, were enhanced during the pandemic, correlating significantly with MERS-CoV spike-specific antibodies and neutralizing activity. Therefore, incorporating these cross-reactive and immunogenic epitopes into pan-CoV vaccine formulations may facilitate effective vaccine development.

A natural variation in the RNA polymerase of severe fever with thrombocytopenia syndrome virus enhances viral replication and in vivo virulence

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease with high mortality in Eastern Asia. The disease is caused by the SFTS virus (SFTSV), also known as Dabie bandavirus, which has a segmented RNA genome consisting of L, M, and S segments. Previous studies have suggested differential viral virulence depending on the genotypes of SFTSV; however, the critical viral factor involved in the differential viral virulence is unknown. Here, we found a significant difference in viral replication in vitro and virulence in vivo between two Korean isolates belonging to the F and B genotypes, respectively. By generating viral reassortants using the two viral strains, we demonstrated that the L segment, which encodes viral RNA-dependent RNA polymerase (RdRp), is responsible for the enhanced viral replication and virulence. Comparison of amino acid sequences and viral replication rates revealed a point variation, E251K, on the surface of RdRp to be the most significant determinant for the enhanced viral replication rate and in vivo virulence. The effect of the variation was further confirmed using recombinant SFTSV generated by reverse genetic engineering. Therefore, our results indicate that natural variations affecting the viral replicase activity could significantly contribute to the viral virulence of SFTSV.

Epigenetic alterations of the BDNF gene in combat-related post-traumatic stress disorder

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays a crucial role in modulating resilience and vulnerability to stress. The aim of this study was to investigate whether epigenetic regulation of the BDNF gene is a biomarker of post-traumatic stress disorder (PTSD) development among veterans exposed to combat in the Vietnam War.

METHODS

Using the Clinician-Administered PTSD Scale, combat veterans were grouped into those with (n = 126) and without (n = 122) PTSD. DNA methylation levels at four CpG sites within the BDNF promoter I region were quantified in the peripheral blood using pyrosequencing. The effects of BDNF DNA methylation levels and clinical variables on the diagnosis of PTSD were tested using binary logistic regression analysis.

RESULTS

Subjects with PTSD showed a higher DNA methylation of four CpG sites at the BDNF promoter compared with those without PTSD. High methylation levels at the BDNF promoter CpG site, high combat exposure, and alcohol problems were significantly associated with PTSD diagnosis.

CONCLUSIONS

This study demonstrated an association between higher DNA methylation of the BDNF promoter and PTSD diagnosis in combat-exposed individuals. Our findings suggest that altered BDNF methylation may be a valuable biomarker of PTSD after trauma exposure.

The ribonuclease L-dependent antiviral roles of human 2',5'-oligoadenylate synthetase family members against hepatitis C virus

The latent ribonuclease RNase L and the interferon-inducible 2',5'-oligoadenylate synthetase (OAS) have been implicated in the antiviral response against hepatitis C virus (HCV). However, the specific roles of these enzymes against HCV have not been fully elucidated. In this study, a scarce endogenous expression and RNA degrading activity of RNase L in human hepatoma Huh7 cells enabled us to demonstrate the antiviral activity of RNase L against HCV replication through the transient expression of the enzyme. The antiviral potential of specific members of the OAS family was further examined through overexpression and RNA interference approaches. Our data suggested that among the members of the OAS family, OAS1 p46 and OAS3 p100 mediate the RNase L-dependent antiviral activity against HCV.

Nonstructural 5A protein activates beta-catenin signaling cascades: implication of hepatitis C virus-induced liver pathogenesis

BACKGROUND/AIMS

The nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) has been implicated in HCV-induced liver pathogenesis. Wnt/beta-catenin signaling has also been involved in tumorigenesis. To elucidate the molecular mechanism of HCV pathogenesis, we examined the potential effects of HCV NS5A protein on Wnt/beta-catenin signal transduction cascades.

METHODS

The effects of NS5A protein on beta-catenin signaling cascades in hepatic cells were investigated by luciferase reporter gene assay, confocal microscopy, immunoprecipitation assay, and immunoblot analysis.

RESULTS

beta-Catenin-mediated transcriptional activity is elevated by NS5A protein, in the context of HCV replication, and by infection of cell culture-produced HCV. NS5A protein directly interacts with endogenous beta-catenin and colocalizes with beta-catenin in the cytoplasm. NS5A protein inactivates glycogen synthase kinase 3beta and increases subsequent accumulation of beta-catenin in HepG2 cells. beta-Catenin was also accumulated in HCV patients' liver tissues. In addition, the accumulation of beta-catenin in HCV replicon cells requires both activation of phosphatidylinositol 3-kinase and inactivation of GSK3beta.

CONCLUSIONS

NS5A activates beta-catenin signaling cascades through increasing the stability of beta-catenin. This modulation is accomplished by the protein interplay between viral and cellular signaling transducer. These data suggest that NS5A protein may directly be involved in Wnt/beta-catenin-mediated liver pathogenesis.

PKR protein kinase is activated by hepatitis C virus and inhibits viral replication through translational control

Hepatitis C virus (HCV) infection is currently treated with IFNalpha-based therapy but little is known how IFNalpha inhibits HCV replication. We show here that HCV JFH1 infection of human hepatoma Huh-7 cells leads to the activation of IFN-inducible protein kinase PKR and phosphorylation of the translation initiation factor eIF2alpha. Compared to a control cell HCV replication was significantly elevated in a PKR-knockdown cell, giving rise to a 10-fold higher viral titer, and was less sensitive to IFNalpha treatment. Conversely, transient expression of PKR inhibited HCV replication in a kinase-dependent manner with concomitant increase of eIF2alpha phosphorylation. Further, expression of a phospho-mimetic eIF2alpha mutant moderately inhibited HCV replication. Together, these results demonstrate that PKR is activated by HCV infection and plays a critical antiviral role through inhibition of viral protein translation.

Hepatitis C virus NS2 protein activates cellular cyclic AMP-dependent pathways

Chronic infection of the hepatitis C virus (HCV) leads to liver cirrhosis and cancer. The mechanism leading to viral persistence and hepatocellular carcinoma, however, has not been fully understood. In this study, we show that the HCV infection activates cellular cAMP-dependent pathways. Expression of a luciferase reporter gene controlled by a basic promoter with the cAMP response element (CRE) was significantly elevated in human hepatoma Huh-7 cells infected with the HCV JFH1. Analysis with viral subgenomic replicons indicated that the HCV NS2 protein is responsible for the effect. Furthermore, the level of cellular transcripts whose stability is known to be regulated by cAMP was specifically reduced in cells harboring NS2-expressing replicons. These results allude to the HCV NS2 protein having a novel function of regulating cellular gene expression and proliferation through the cAMP-dependent pathway.

Attenuated expression of interferon-induced protein kinase PKR in a simian cell devoid of type I interferons

The interferon-induced, double-stranded RNA (dsRNA)-dependent protein kinase PKR plays a key role in interferon-mediated host defense against viral infection, and is implicated in cellular transformation and apoptosis. We have isolated a cDNA of simian PKR encoding a product with 83% amino acid identity to the human homolog and showed that PKR expression is significantly attenuated in the Vero E6 African green monkey kidney cells devoid of type I interferon genes. A variant form of PKR lacking the exon 12 in the kinase domain is produced in these cells, presumably from an alternatively spliced transcript. Unlike wild type PKR, the variant protein named PKR-DE12 is incapable of auto-phosphorylation and phosphorylation of eIF2-a, indicating that the kinase sub-domains III and IV embedded in exon 12 are indispensable for catalytic function. PKR-DE12 had no dominant negative effect but was weakly phosphorylated in trans by wild type PKR.

Soochong virus: An antigenically and genetically distinct hantavirus isolated fromApodemus peninsulae in Korea

Hantaan (HTN) virus, the etiologic agent of clinically severe hemorrhagic fever with renal syndrome (HFRS), was first isolated in 1976 from lung tissue of a striped-field mouse (Apodemus agrarius) captured in Songnae-ri, Gyeonggi Province, Republic of Korea. Found primarily in mountainous areas, the Korean field mouse (A. peninsulae) is the second-most dominant field rodent species found throughout Korea. A new hantavirus, designated Soochong (SOO), was isolated in Vero E6 cells from four A. peninsulae captured in August 1997 at Mt. Gyebang in Hongcheon-gun, Mt. Gachil, Inje-gun, Gangwon Province, and in September 1998 at Mt. Deogyu, Muju-gun, Jeollabuk Province. The entire S, M, and L genomic segments of SOO virus, amplified by RT-PCR from lung tissues of seropositive A. peninsulae and from virus-infected Vero E6 cells, diverged from HTN virus (strain 76-118) by 15.6%, 22.8%, and 21.7% at the nucleotide level and 3.5%, 9.5%, and 4.6% at the amino acid level, respectively. Phylogenetic analyses of the nucleotide and deduced amino acid sequences, using the maximum parsimony and neighbor-joining methods, indicated that SOO virus was distinct from A. agrarius-borne HTN virus. SOO virus shared a common ancestry with Amur virus from Far East Russia, as well as with H5 and B78 hantaviruses, previously isolated from HFRS patients in China. Cross-focus-reduction neutralizating antibody tests showed that SOO virus, which is the first hantavirus isolated in cell culture from A. peninsulae, could be classified as a new hantavirus serotype.

A dominant antigenic region of the hantaan virus nucleocapsid protein is located within a amino-terminal short stretch of hydrophilic residues

The nucleocapsid (N) protein of the Hantaan virus (HTNV) is a major viral antigen that induces a strong antibody response during the acute phase of infection. By immunoblot analyses of the recombinant N proteins using human sera of the hemorrhagic fever with renal syndrome (HFRS), we have confirmed previous finding by other investigators of the presence of a highly antigenic region near the amino terminus of the HTNV N protein. We have further located the antigenic region within a short stretch of hydrophilic sequences between the 26 and the 46th amino acid residues. The recombinant glutathione S-transferase fusion proteins containing this region was expressed as a soluble form in a large quantity in Escherichia coli, and purified by a single-step affinity chromatography. The recombinant antigen also showed a similar, but a weaker reactivity with human antisera to Seoul virus (SEOV), the virus most closely related to HTNV.

Strain differences in the expression of corticotropin-releasing hormone immunoreactivity in nerves that supply the spleen and thymus

The existence of nerve fibers containing corticotropin-releasing hormone (CRH) immunoreactivity in primary and secondary lymphoid organs from three strains of young adult male rats was examined. Spleens and thymuses from Fischer 344 (F344), Sprague-Dawley (SD) and Lewis (LEW) rats were prepared for immunocytochemistry using antisera directed against CRH. In F344 and SD rats, we were unable to demonstrate CRH-immunoreactive nerves in either the thymus or the spleen. Despite the lack of CRH-containing nerves, CRH immunoreactivity was present in pleotropic cells in the septum, cortex and medulla of the thymus, and in the red and white pulp of spleens from F344 and SD rats. In contrast, CRH+ nerves were found in thymuses and spleens from LEW rats. CRH+ nerves coursed in the interlobular septa, capsule, cortex and medulla of the LEW rat thymus. Large CRH-immunoreactive nerve bundles were present in the hilar region of the LEW rat spleen, and individual CRH+ fibers coursed in the capsule, trabeculae, red pulp, venous sinuses and marginal zone of the white pulp of the spleen. These findings indicate strain differences in neurotransmitter-specific nerves that innervate the rat spleen and thymus under basal conditions.

Apoptosis is induced by hantaviruses in cultured cells

Hantaviruses replicate in primary and cultured animal cells with little or no cytopathic effect. We report here that the cultured Vero E6 cells infected by the Hantaan or by the Prospect Hill viruses exhibited characteristic features of apoptosis, including condensation and segmentation of nuclei and internucleosomal cleavage of nuclear DNA. Apoptosis was not seen in the cells adsorbed by UV-inactivated virus, indicating that the viral replication is required for the induction of apoptosis. Furthermore, level of the proto-oncogenic Bcl-2 protein was significantly reduced, whereas its mRNA level remained unchanged in Hantaan virus-infected cells, suggesting possible involvement and posttranscriptional regulation of this antiapoptotic protein in the process.