Antibody profile in symptomatic/asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected Saudi persons

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected persons could be symptomatic or asymptomatic. Asymptomatic and symptomatic patients can transmit SARS-CoV-2. This study aimed to study the humoral immune response in Saudis who are Covid-19 symptomatic and asymptomatic patients. We created three types of enzyme-linked immunosorbant assays (ELISAs) to reveal IgG and IgM antibodies (Abs) against SARS-CoV-2. The developed ELISAs were designed to detect Abs against SARS-CoV-2 N, S and N + S proteins. A number of Covid-19 symptomatic (1 5 3) and asymptomatic (84) RT–PCR-confirmed patient sera were used to evaluate the ELISAs and to determine the IgG and IgM antibody profile in those patients. The sensitivity and specificity of these ELISAs were evaluated using pre-Covid-19 pandemic serum samples. The results revealed the existence of anti-SARS-CoV-2 IgG and IgM Abs in Covid-19 symptomatic and asymptomatic Saudi persons. The use of SARS-CoV-2 N and S proteins in the same ELISA greatly increased the detectability of infection. In conclusion, the Covid-19 symptomatic and asymptomatic Saudi persons demonstrated both IgG and IgM antibody profile with higher titer in symptomatic patients. The use of N + S proteins as antibody capture antigens greatly increased the ELISA sensitivity.     

Glycogen synthase kinase-3: A putative target to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic

The coronavirus disease 19 (COVID-19) outbreak caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) had turned out to be highly pathogenic and transmittable. Researchers throughout the globe are still struggling to understand this strain's aggressiveness in search of putative therapies for its control. Crosstalk between oxidative stress and systemic inflammation seems to support the progression of the infection. Glycogen synthase kinase-3 (Gsk-3) is a conserved serine/threonine kinase that mainly participates in cell proliferation, development, stress, and inflammation in humans. Nucleocapsid protein of SARS-CoV-2 is an important structural protein responsible for viral replication and interferes with the host defence mechanism by the help of Gsk-3 protein. The viral infected cells show activated Gsk-3 protein that degrades the Nuclear factor erythroid 2-related factor (Nrf2) protein, resulting in excessive oxidative stress. Activated Gsk-3 also modulates CREB-DNA activity, phosphorylates NF-​κB, and degrades β-catenin, thus provokes systemic inflammation. Interaction between these two pathophysiological events, oxidative stress, and inflammation enhance mucous secretion, coagulation cascade, and hypoxia, which ultimately leads to multiple organs failure, resulting in the death of the infected patient. The present review aims to highlight the pathogenic role of Gsk-3 in viral replication, initiation of oxidative stress, and inflammation during SARS-CoV-2 infection. The review also summarizes the potential Gsk-3 pathway modulators as putative therapeutic interventions in combating the COVID-19 pandemic.     

值得关切的严重急性呼吸综合征冠状病毒2型变异株

自2019年12月2019冠状病毒病暴发流行以来,严重急性呼吸综合征冠状病毒 2 型已经产生了1万个以上的变异株。其中有些可能获得更强的传染性,有的致病性得以提高,有的或许不能被现有的检测试剂检测出来,还有的也许能够逃逸疫苗的免疫保护作用。世界卫生组织于2021年5月31日发布了针对这些变异株的新的命名系统。本文对当前世界上流行较广的4个变异株进行综述,包括最近在广州市引起小暴发的δ变异株。     

免疫系统：严重急性呼吸综合征冠状病毒2型感染后的一把双刃剑

免疫系统是人体内的一把双刃剑,它一方面能清除侵染的各类病原体,但另一方面其异常调控又能在人体中引发各类免疫性疾病,甚至导致死亡。本文将简要讨论人体免疫系统与新的冠状病毒﹝即严重急性呼吸综合征冠状病毒2型(severe acute respiratory syndrome coronavirus 2,SARS-CoV-2)〕感染的相互关系。一方面免疫系统能全方位地预防病毒感染,进化出一整套从分子到细胞、从短期到长期的病毒清除机制;另一方面,免疫系统又可能引发“细胞因子风暴”,给SARS-CoV-2的感染患者带来负面作用。本文还将讨论受到广泛关注的免疫相关的治疗策略,着重探讨抗体依赖的增强效应(antibody-dependent enhancement, ADE)可能给疫苗研发带来的困难与挑战。     

A preliminary study on serological assay for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 238 admitted hospital patients

In this study, we aimed to evaluate the diagnostic value of serological assay for SARS-CoV-2. A newly-developed ELISA assay for IgM and IgG antibodies against N protein of SARS-CoV-2 was used to screen the serums of 238 admitted hospital patients between February 6 and February 14, 2020 with confirmed or suspected SARS-CoV-2. SARS-CoV-2 RNA was detected on pharyngeal swab specimens using real time RT-PCR. 194 (81.5%) of the serums were detected to be antibody (IgM and/or IgG) positive, significantly higher than the positive rate of viral RNA (64.3%). There was no difference in the positive rate of antibodies between the confirmed patients (83.0%, 127/153) and the suspected patients (78.8%, 67/85), whose nucleic acid tests were negative. The antibody positive rates were very low in the first five days after initial onset of symptoms, and then rapidly increased as the disease progressed. After 10 days, the antibody positive rates jumped from below 50% to over 80%. However, the positive rates of viral RNA maintained above 60% in the first 11 days after initial onset of symptoms, and then rapidly decreased. Overall, the suspected patients were most likely infected by SARS-CoV-2. Before the 11th day after initial onset of symptoms, nucleic acid test is key for confirmation of viral infection. The combination of serological assay can greatly improve the diagnostic efficacy. After the 11th day post-disease onset, the diagnosis for viral infection should be majorly dependent on serological assay.     

Modeling the early events of severe acute respiratory syndrome coronavirus infection in vitro

The clinical picture of severe acute respiratory syndrome (SARS) is characterized by pulmonary inflammation and respiratory failure, resembling that of acute respiratory distress syndrome. However, the events that lead to the recruitment of leukocytes are poorly understood. To study the cellular response in the acute phase of SARS coronavirus (SARS-CoV)-host cell interaction, we investigated the induction of chemokines, adhesion molecules, and DC-SIGN (dendritic cell-specific ICAM-3-grabbing nonintegrin) by SARS-CoV. Immunohistochemistry revealed neutrophil, macrophage, and CD8 T-cell infiltration in the lung autopsy of a SARS patient who died during the acute phase of illness. Additionally, pneumocytes and macrophages in the patient's lung expressed P-selectin and DC-SIGN. In in vitro study, we showed that the A549 and THP-1 cell lines were susceptible to SARS-CoV. A549 cells produced CCL2/monocyte chemoattractant protein 1 (MCP-1) and CXCL8/interleukin-8 (IL-8) after interaction with SARS-CoV and expressed P-selectin and VCAM-1. Moreover, SARS-CoV induced THP-1 cells to express CCL2/MCP-1, CXCL8/IL-8, CCL3/MIP-1alpha, CXCL10/IP-10, CCL4/MIP-1beta, and CCL5/RANTES, which attracted neutrophils, monocytes, and activated T cells in a chemotaxis assay. We also demonstrated that DC-SIGN was inducible in THP-1 as well as A549 cells after SARS-CoV infection. Our in vitro experiments modeling infection in humans together with the study of a lung biopsy of a patient who died during the early phase of infection demonstrated that SARS-CoV, through a dynamic interaction with lung epithelial cells and monocytic cells, creates an environment conducive for immune cell migration and accumulation that eventually leads to lung injury.     

Lethal infection of K18-hACE2 mice infected with severe acute respiratory syndrome coronavirus

The severe acute respiratory syndrome (SARS), caused by a novel coronavirus (SARS-CoV), resulted in substantial morbidity, mortality, and economic losses during the 2003 epidemic. While SARS-CoV infection has not recurred to a significant extent since 2003, it still remains a potential threat. Understanding of SARS and development of therapeutic approaches have been hampered by the absence of an animal model that mimics the human disease and is reproducible. Here we show that transgenic mice that express the SARS-CoV receptor (human angiotensin-converting enzyme 2 [hACE2]) in airway and other epithelia develop a rapidly lethal infection after intranasal inoculation with a human strain of the virus. Infection begins in airway epithelia, with subsequent alveolar involvement and extrapulmonary virus spread to the brain. Infection results in macrophage and lymphocyte infiltration in the lungs and upregulation of proinflammatory cytokines and chemokines in both the lung and the brain. This model of lethal infection with SARS-CoV should be useful for studies of pathogenesis and for the development of antiviral therapies.     

Mosaic evolution of the severe acute respiratory syndrome coronavirus

Severe acute respiratory syndrome (SARS) is a deadly form of pneumonia caused by a novel coronavirus, a viral family responsible for mild respiratory tract infections in a wide variety of animals including humans, pigs, cows, mice, cats, and birds. Analyses to date have been unable to identify the precise origin of the SARS coronavirus. We used Bayesian, neighbor-joining, and split decomposition phylogenetic techniques on the SARS virus replicase, surface spike, matrix, and nucleocapsid proteins to reveal the evolutionary origin of this recently emerging infectious agent. The analyses support a mammalian-like origin for the replicase protein, an avian-like origin for the matrix and nucleocapsid proteins, and a mammalian-avian mosaic origin for the host-determining spike protein. A bootscan recombination analysis of the spike gene revealed high nucleotide identity between the SARS virus and a feline infectious peritonitis virus throughout the gene, except for a 200- base-pair region of high identity to an avian sequence. These data support the phylogenetic analyses and suggest a possible past recombination event between mammalian-like and avian-like parent viruses. This event occurred near a region that has been implicated to be the human receptor binding site and may have been directly responsible for the switch of host of the SARS coronavirus from animals to humans.     

Molecular biology of severe acute respiratory syndrome coronavirus

The worldwide epidemic of severe acute respiratory syndrome (SARS) in 2003 was caused by a novel coronavirus called SARS-CoV. Coronaviruses and their closest relatives possess extremely large plus-strand RNA genomes and employ unique mechanisms and enzymes in RNA synthesis that separate them from all other RNA viruses. The SARS epidemic prompted a variety of studies on multiple aspects of the coronavirus replication cycle, yielding both rapid identification of the entry mechanisms of SARS-CoV into host cells and valuable structural and functional information on SARS-CoV proteins. These recent advances in coronavirus research have important implications for the development of anti-SARS drugs and vaccines.     

Quaternary structure of the severe acute respiratory syndrome (SARS) coronavirus main protease

SARS (severe acute respiratory syndrome) has been one of the most severe viral infectious diseases last year and still remains as a highly risky public health problem around the world. Exploring the types of interactions responsible for structural stabilities of its component protein molecules constitutes one of the approaches to find a destabilization method for the virion particle. In this study, we performed a series of experiments to characterize the quaternary structure of the dimeric coronavirus main protease (M(pro), 3CL(pro)). By using the analytical ultracentrifuge, we demonstrated that the dimeric SARS coronavirus main protease exists as the major form in solution at protein concentration as low as 0.10 mg/mL at neutral pH. The enzyme started to dissociate at acidic and alkali pH values. Ionic strength has profound effect on the dimer stability indicating that the major force involved in the subunit association is ionic interactions. The effect of ionic strength on the protease molecule was reflected by the drastic change of electrostatic potential contour of the enzyme in the presence of NaCl. Analysis of the crystal structures indicated that the interfacial ionic interaction was attributed to the Arg-4...Glu-290 ion pair between the subunits. Detailed examination of the dimer-monomer equilibrium at different pH values reveals apparent pK(a) values of 8.0 +/- 0.2 and 5.0 +/- 0.1 for the Arg-4 and Glu-290, respectively. Mutation at these two positions reduces the association affinity between subunits, and the Glu-290 mutants had diminished enzyme activity. This information is useful in searching for substances that can intervene in the subunit association, which is attractive as a target to neutralize the virulence of SARS coronavirus.     

Tea crude extracts effectively inactivate severe acute respiratory syndrome coronavirus 2

It is well known that black and green tea extracts, particularly polyphenols, have antimicrobial activity against various pathogenic microbes including viruses. However, there is limited data on the antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged rapidly in China in late 2019 and which has been responsible for coronavirus disease 2019 (COVID-19) pandemic globally. In this study, 20 compounds and three extracts were obtained from black and green tea and found that three tea extracts showed significant antiviral activity against SARS-CoV-2, whereby the viral titre decreased about 5 logs TCID₅₀ per ml by 1·375 mg ml⁻¹ black tea extract and two-fold diluted tea bag infusion obtained from black tea when incubated at 25°C for 10 s. However, when concentrations of black and green tea extracts were equally adjusted to 344 µg ml⁻¹, green tea extracts showed more antiviral activity against SARS-CoV-2. This simple and highly respected beverage may be a cheap and widely acceptable means to reduce SARS-CoV-2 viral burden in the mouth and upper gastrointestinal and respiratory tracts in developed as well as developing countries.     

Hosting the severe acute respiratory syndrome coronavirus: specific cell factors required for infection

As with all viruses, the severe acute respiratory syndrome coronavirus (SARS-CoV) utilizes specific host cell factors during its infection cycle. Some of these factors have been identified and are now increasingly scrutinized as targets to intervene with infection. In this brief review, we describe the current understanding of how the SARS-CoV is able to use the cellular machinery for its replication.     

Antibodies at work in the time of severe acute respiratory syndrome coronavirus 2

In view of devastating effects of COVID-19 on human life, there is an urgent need for the licened vaccines or therapeutics for the SARS-CoV-2 infection. Age-old passive immunization with protective antibodies to neutralize the virus is one of the strategies for emergency prophylaxis and therapy for coronavirus disease 2019 (COVID-19). In this review, the authors discuss up-to-date advances in immune-based therapy for COVID-19. The use of convalescent plasma therapy as the first line of defense to treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been established, with encouraging results. Monoclonal antibodies (mAbs) that bind to the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein or block the interaction between SARS-CoV-2 RBD and the human angiotensin-converting enzyme 2 receptor have been found to be very promising as a countermeasure for tackling the SARS-CoV-2 infection, and clinical trials are underway. Considering the counterproductive antibody-dependent enhancement of the virus, mAbs therapy that is safe and efficacious, even in people with underlying conditions, will be a significant breakthrough. In addition, emerging immunotherapeutic interventions using nanobodies and cellular immunotherapy are promising avenues for tackling the COVID-19 pandemic. The authors also discuss the implication of mAbs as mediators of cytokine storm syndrome to modify the immune response of COVID-19 patients, thus reducing the fatality rate of COVID-19 infection.     

Characterization of severe acute respiratory syndrome coronavirus membrane protein

The coronavirus membrane protein (M) is the key player in the assembly of virions at intracellular membranes between endoplasmic-reticulum and Golgi-complex. Using a newly established human monoclonal anti-M antibody we detected glycosylated and nonglycosylated membrane-associated M in severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infected cells and in purified virions. Further analyses revealed that M contained a single N-glycosylation site at asparagine 4. Recombinant M was transported to the plasma membrane and gained complex-type N-glycosylation. In SARS-CoV infected cells and in purified virions, however, N-glycosylation of M remained endoglycosidase H-sensitive suggesting that trimming of the N-linked sugar side chain is inhibited.     

严重急性呼吸综合征冠状病毒2 Omicron变异株研究进展

世界卫生组织(World Health Organization, WHO)于2021年11月26日将首次在南非报告的新型冠状病毒 B．1.1.529 变异株列为受关注变种(variant of concern, VOC),并将其命名为奥密克戎(Omicron)。该变异株存在约50个突变,仅在刺突蛋白区域就有至少30个突变,远远超过其他流行株的突变位点数量。根据对突变位点的分析以及初步实验证实,该毒株可能具有极强的传染性以及免疫逃逸能力。Omicron变异株会怎样影响新冠疫情的走向引起了各国的广泛关注,本文将从Omicron变异株的基本特征、检测、致病性、传染性、免疫逃逸等方面进行综述。     

Significant role of host sialylated glycans in the infection and spread of severe acute respiratory syndrome coronavirus 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been transmitted across all over the world, in contrast to the limited epidemic of genetically- and virologically-related SARS-CoV. However, the molecular basis explaining the difference in the virological characteristics among SARS-CoV-2 and SARS-CoV has been poorly defined. Here we identified that host sialoglycans play a significant role in the efficient spread of SARS-CoV-2 infection, while this was not the case with SARS-CoV. SARS-CoV-2 infection was significantly inhibited by α2-6-linked sialic acid-containing compounds, but not by α2–3 analog, in VeroE6/TMPRSS2 cells. The α2-6-linked compound bound to SARS-CoV-2 spike S1 subunit to competitively inhibit SARS-CoV-2 attachment to cells. Enzymatic removal of cell surface sialic acids impaired the interaction between SARS-CoV-2 spike and angiotensin-converting enzyme 2 (ACE2), and suppressed the efficient spread of SARS-CoV-2 infection over time, in contrast to its least effect on SARS-CoV spread. Our study provides a novel molecular basis of SARS-CoV-2 infection which illustrates the distinctive characteristics from SARS-CoV.     

Construction of a severe acute respiratory syndrome coronavirus infectious cDNA clone and a replicon to study coronavirus RNA synthesis

The engineering of a full-length infectious cDNA clone and a functional replicon of the severe acute respiratory syndrome coronavirus (SARS-CoV) Urbani strain as bacterial artificial chromosomes (BACs) is described in this study. In this system, the viral RNA was expressed in the cell nucleus under the control of the cytomegalovirus promoter and further amplified in the cytoplasm by the viral replicase. Both the infectious clone and the replicon were fully stable in Escherichia coli. Using the SARS-CoV replicon, we have shown that the recently described RNA-processing enzymes exoribonuclease, endoribonuclease, and 2'-O-ribose methyltransferase were essential for efficient coronavirus RNA synthesis. The SARS reverse genetic system developed as a BAC constitutes a useful tool for the study of fundamental viral processes and also for developing genetically defined vaccines.     

Smoking enhances the expression of angiotensin-converting enzyme 2 involved in the efficiency of severe acute respiratory syndrome coronavirus 2 infection

Smoking is one of the risk factors most closely related to the severity of coronavirus disease 2019 (COVID-19). However, the relationship between smoking history and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infectivity is unknown. In this study, we evaluated the ACE2 expression level in the lungs of current smokers, ex-smokers, and nonsmokers. The ACE2 expression level of ex-smokers who smoked cigarettes until recently (cessation period shorter than 6 months) was higher than that of nonsmokers and ex-smokers with a long history of nonsmoking (cessation period longer than 6 months). We also showed that the efficiency of SARS-CoV-2 infection was enhanced in a manner dependent on the angiotensin-converting enzyme 2 (ACE2) expression level. Using RNA-seq analysis on the lungs of smokers, we identified that the expression of inflammatory signaling genes was correlated with ACE2 expression. Notably, with increasing duration of smoking cessation among ex-smokers, not only ACE2 expression level but also the expression levels of inflammatory signaling genes decreased. These results indicated that smoking enhances the expression levels of ACE2 and inflammatory signaling genes. Our data suggest that the efficiency of SARS-CoV-2 infection is enhanced by smoking-mediated upregulation of ACE2 expression level.