Dynamic SARS-CoV-2-Specific Immunity in Critically Ill Patients With Hypertension.

Background: The current outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses an unprecedented health crisis. The most common chronic illness among patients infected with SARS-CoV-2 is hypertension. Immune dysregulation plays an important role in SARS-CoV-2 infection and in the development of hypertension; however, the dynamic immunological characteristics of COVID-19 patients with hypertension remain largely unclear. Methods: In total, 258 hypertensive patients infected with SARS-CoV-2 were included in this study. CD38+HLA-DR+ and CD38+PD-1+ CD8+ T cells, IFNγ+CD4+ and IFNγ+CD8+ T cells, the titers of IgG, IgM, and IgA against SARS-CoV-2 spike protein, and SARS-CoV-2 throat viral loads were measured weekly over 4 weeks after the onset of symptoms. Clinical outcomes were also monitored. Findings: CD4+ T lymphopenia was observed in 100% of the severe and critical cases. Compared with the surviving patients, the patients with fatal outcomes exhibited high and prolonged expression of CD38+HLA-DR+ and CD38+PD-1+ on CD8+ T cells, low expression of SARS-CoV-2-specific IFNγ+CD4+ and IFNγ+CD8+ T cells, low titers of IgG, IgM, and IgA against SARS-CoV-2 spike protein, and high SARS-CoV-2 viral load during the illness. In the surviving patients, the viral load was significantly inversely correlated with SARS-CoV-2-specific IFNγ+CD8+and IFNγ+CD4+ T cells, IgG, IgM, and IgA. Interpretation: T lymphopenia is common in critical or severe COVID-19 cases with hypertension. Prolonged activation and exhaustion of CD8+ T cells were associated with severe disease. The delayed SARS-CoV-2-specific antibody responses may be insufficient for overcoming severe SARS-CoV-2 infection in the absence of SARS-CoV-2-specific cellular responses.

Application of antibodies against nonstructural protein 2B of dengue serotype 2 virus induced by DNA immunisation or recombinant protein NS 2B immunisation in BALB/c mice.

To investigate the structure and function of nonstructural (NS) protein 2B of the dengue serotype 2 virus (DV2) during infection, polyclonal antibodies (Abs) against DV2 NS2B were prepared by immunisation with NS2B protein or by DNA immunisation. The full-length NS2B gene was cloned and inserted into the prokaryotic expression vector pQE31, resulting in a vector, named pQE-NS2B, or into the eukaryotic expression vector pCAGGS-P7, resulting in the vector pCAG-NS2B. The pQE-NS2B vector was transfected into Escherichia coli JM109, and recombinant NS2B protein was obtained by Ni(2+)-NTA agarose affinity chromatography. Vero cells transfected with pCAG-NS2B showed that NS2B protein can be expressed in eukaryotic cells. Finally, mice were immunised with the recombinant NS2B protein or pCAG-NS2B. Anti-NS2B sera from the immunised mice could specifically react with DV2 NS2B proteins, as visualised by fluorescence staining and Western blotting. Immunisation with NS2B protein induced a higher titre of the antibody than that induced by DNA immunisation. These data indicate that our antisera against DV2 NS2B can recognise both the natural and denatured NS2B protein. Based on these results, the polyclonal Abs could be used as a tool for studying the role of NS2B in the pathogenesis of DV2.

Myosin Vc, a member of the actin motor family associated with Rab8, is involved in the release of DV2 from HepG2 cells.

OBJECTIVE: The pathogenesis of the dengue virus (DV) infection has not been well defined. We have reported that actin and Rab8 are involved in DV2 infection. Myosin Vc (Myo5c) is a novel member of the class V myosins and regulates the actin-mediated membrane trafficking associated with Rab8. In this study, the involvement of Myo5c in the release of DV2 was investigated in HpeG2 cells. METHODS: Distributions of actin, Myo5c, DV2 and Rab8 were revealed by fluorescent staining. HepG2(Myo5c-tail) cells expressing a dominant-negative mutant of Myo5c were constructed by transfection and were assessed by Western blotting. The viral titers were detected by plaque assay, and the expression of Rab8 was analyzed by flow cytometry. RESULTS: DV2 infection altered the distribution pattern of Myo5c, which might be associated with the depolymerization of actin, though colocalization rates of Myo5c with DV2 or actin were low. Furthermore, the release of DV2, but not the intracellular viral production, was reduced from HepG2(Myo5c-tail) cells. Moreover, Myo5c colocalized with Rab8 and an increase of Rab8 was associated with the decrease of the viral release caused by the Myo5c tail. CONCLUSIONS: Our data suggest that Myo5c associated with Rab8 is involved in the release of DV2 from HepG2 cells.

Entry of dengue virus serotype 2 into ECV304 cells depends on clathrin-dependent endocytosis, but not on caveolae-dependent endocytosis.

Caveolae- and clathrin-mediated endocytosis are major internalization pathways used by several pathogens; however, their distinctive roles in dengue virus (DV) entry have not been addressed. In this study, we compared the involvement of caveolae- and clathrin-mediated endocytosis in the infectious entry of DV serotype 2 (DV2) into human endothelial-like ECV304 cells. Confocal microscopy study on DV2-infected cells showed that viral antigens were co-localized with clathrin heavy chains, epidermal growth factor pathway substrate clone 15 (Eps15), and adaptin-alpha, but not with caveolin-1. Treatment with chlorpromazine, which inhibits clathrin-dependent endocytosis, led to reduced virus entry into cells, whereas treatment with nystatin, a caveolae inhibitory agent, did not. Furthermore, gene silencing of Eps15 resulted in an average of 75% reduced infection of ECV304 cells by DV2. Our results demonstrated that DV2 enters ECV304 cells by clathrin-dependent endocytosis, not by caveolae-dependent endocytosis.

Vimentin is required for dengue virus serotype 2 infection but microtubules are not necessary for this process.

The present study investigated the effect of microtubules (MTs) and vimentin during dengue virus serotype 2 (DV2) infection. Immunostaining showed that DV2 infection induced MT and vimentin reorganization. Colocalization of DV2 antigens with MTs or vimentin were often observed in ECV304 cells. MT-disrupting agents could enhance DV2 release but did not affect other steps of virus replication. In contrast, disruption of vimentin inhibited DV2 infection. Our results suggest that an MT-dependent mechanism may not be necessary for DV2 infection, and MT disruption may promote DV2 release. However, vimentin is required for DV2 infection.

Rab8, a vesicular traffic regulator, is involved in dengue virus infection in HepG2 cells.

OBJECTIVE: The pathogenesis of dengue virus (DV) has not been completely clarified. Rab8 regulates vesicular traffic from Golgi to plasma membrane where DV is matured and then delivered by exocytosis. In this study, involvement of Rab8 in DV serotype 2 (DV2) infection was investigated in HpeG2 cells. METHODS: Distributions of Rab8 and DV2, and the number of infection cells were observed by immunostaining. HepG2(Rab8AM) and HepG2(Rab8DN) cells were constructed to stably express a constitutively active mutant of Rab8 and a dominant negative mutant, respectively, which were assessed by flow cytometry. Production of infectious virions and the amounts of DV2 entry were detected by standard plaque assay. Viral RNA replication was detected by real-time RT-PCR. RESULTS: Rab8 showed high co-localization with DV2 in HpeG2 cells and the amount of DV antigen-positive cells decreased in HepG2(Rab8AM) and HepG2(Rab8DN) cells. Also, progeny virus released from those cells was drastically reduced. Infectious virions produced in cells were also significantly reduced, while the viral RNA replication was down-regulated by a different level. Furthermore, viral entry into those cells was reduced by about 80%. CONCLUSIONS: Our data suggest that the function of Rab8 is important for DV2 infection, and Rab8 may be involved in DV2 infection.

Up-regulated expression of beta3 integrin induced by dengue virus serotype 2 infection associated with virus entry into human dermal microvascular endothelial cells.

Permeability alteration of microvascular endothelia is a factor in the plasma leakage produced by dengue virus (DV) infection, and beta3 integrin plays central roles in maintaining capillary integrity and regulating vascular permeability. In this study, interaction between beta3 integrin and DV serotype 2 (DV2) was investigated using human dermal microvascular endothelial cell line-1 (HMEC-1). We reported that DV2 infection could induce high expression level of beta3 integrin, and the high fluorescence intensity of beta3 integrin antigen observed in HMEC-1 after infection showed high co-localization with DV antigen. Pre-incubation of the virus with soluble alphanubeta3 integrin could strongly inhibit DV2 entry. And about 90% of virus entry was inhibited when beta3 integrin expression level was down-regulated by RNA interference. Our data indicated that DV2 infection could induce up-regulating expression of beta3 integrin, and beta3 integrin was required for DV2 entry into HMEC-1.