Antibody to severe acute respiratory syndrome (SARS)-associated coronavirus spike protein domain 2 cross-reacts with lung epithelial cells and causes cytotoxicity

Impact of Annexin A2 on virus life cycles

Due to the limited size of viral genomes, hijacking host machinery by the viruses taking place throughout the virus life cycle is inevitable for the survival and proliferation of the virus in the infected hosts. Recent reports indicated that Annexin A2 (AnxA2), a calcium- and lipid-binding cellular protein, plays an important role as a critical regulator in various steps of the virus life cycle. The multifarious AnxA2 functions in cells, such as adhesion, adsorption, endocytosis, exocytosis, cell proliferation and division, inflammation, cancer metastasis, angiogenesis, etc., are intimately related to the various clinical courses of viral infection. Ubiquitous expression of AnxA2 across multiple cell types indicates the broad range of susceptibility of diverse species of the virus to induce disparate viral disease in various tissues, and intracellular expression of AnxA2 in the cytoplasmic membrane, cytosol, and nucleus suggests the involvement of AnxA2 in the regulation of the different stages of various virus life cycles within host cells. However, it is yet unclear as to the molecular processes on how AnxA2 and the infected virus interplay to regulate virus life cycles and thereby the virus-associated disease courses, and hence elucidation of the molecular mechanisms on AnxA2-mediated virus life cycle will provide essential clues to develop therapeutics deterring viral disease.

Tissue plasminogen activator receptor ANXA2 and its complementary regulator anti-inflammatory ANXA1 as prognostic indicators of inflammatory response in COVID-19 pathogenesis

COVID-19 patients demonstrating hyperactive immunologic response appear to have a severe illness with a poor prognosis. This study hypothesizes that the pro-inflammatory Annexin A2 (ANXA2) has role in COVID-19 pathogenesis. In thisobservational study, serum levels of ANXA2 along with interleukin 1 beta (IL1β), IL6, tumour necrosis factor-alpha (TNFα), and anti-inflammatory ANXA1 were determined by sandwich ELISA in 20 each control, mild, moderate, and severe COVID-19 subjects.The ANXA2 levels (130 ng/mL, p < 0.001) were significantly elevated in severe COVID-19 subjects, compared to mild, moderate and controls. Similarly, all the other pro-inflammatory biomarkers levels were also significantly correlated with disease severity (p < 0.0001). However, ANXA1 showed significantly negative correlation with disease severity (p < 0.0001). Furthermore, the pro-inflammatory ANXA2 showed utility in mortality prediction with 86% sensitivity and specificity, and 57% positive predictive value at a serum threshold of 94 ng/mL. Overall,ANXA2 and ANXA1 along with IL1β, IL6, TNFα, would be beneficial biomarkers in assessing the COVID-19 severity and mortality prediction.

Mechanistic insight into the protective and pathogenic immune-responses against SARS-CoV-2

COVID-19 is a severe respiratory illness that has emerged as a devasting health problem worldwide. The disease outcome is heterogeneous, which is most likely dependent on the immunity of an individual. Asymptomatic and mildly/moderate symptomatic (non-severe) patients likely develop an effective early immune response and clear the virus. However, severe symptoms dominate due to a failure in the generation of an effective and specific early immune response against SARS-CoV-2. Moreover, a late surge in pathogenic inflammation involves dysregulated innate and adaptive immune responses leading to local and systemic tissue damage and the emergence of severe disease symptoms. In this review, we describe the potential mechanisms of protective and pathogenic immune responses in "mild/moderate" and "severe" symptomatic SARS-CoV-2 infected people, respectively, and discuss the immune components that are currently targeted for therapeutic intervention.

A review of cytokine-based pathophysiology of Long COVID symptoms

The Long COVID/Post Acute Sequelae of COVID-19 (PASC) group includes patients with initial mild-to-moderate symptoms during the acute phase of the illness, in whom recovery is prolonged, or new symptoms are developed over months. Here, we propose a description of the pathophysiology of the Long COVID presentation based on inflammatory cytokine cascades and the p38 MAP kinase signaling pathways that regulate cytokine production. In this model, the SARS-CoV-2 viral infection is hypothesized to trigger a dysregulated peripheral immune system activation with subsequent cytokine release. Chronic low-grade inflammation leads to dysregulated brain microglia with an exaggerated release of central cytokines, producing neuroinflammation. Immunothrombosis linked to chronic inflammation with microclot formation leads to decreased tissue perfusion and ischemia. Intermittent fatigue, Post Exertional Malaise (PEM), CNS symptoms with "brain fog," arthralgias, paresthesias, dysautonomia, and GI and ophthalmic problems can consequently arise as result of the elevated peripheral and central cytokines. There are abundant similarities between symptoms in Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). DNA polymorphisms and viral-induced epigenetic changes to cytokine gene expression may lead to chronic inflammation in Long COVID patients, predisposing some to develop autoimmunity, which may be the gateway to ME/CFS.

[Importance of autoimmunity induced by SARS-CoV-2 and development of post-vaccination autoimmune diseases]

SARS-CoV-2, a virus belonging to the large family of coronavirus, aroused great interest following the outbreak of this new strain reported in 2019, in Wuhan China. Its clinical spectrum is highly variable, ranging from a self-limited disease to an acute respiratory distress syndrome with systemic clinical manifestations (COVID-19), in which the immune system plays a key role in the pathophysiology of this disease and in its severity; several studies show the prevalence of some autoimmune markers suggesting that they may lead to autoimmune states. The most important strategy worldwide to protect the population was the development of vaccines to induce immunity to severe COVID-19; however, vaccines have also been shown to have the ability to produce autoimmune states in a small percentage of the world's population; nevertheless, the best strategy remains vaccination. The aim of this review is to show the current overview of the mechanisms of SARS-CoV-2-induced autoimmunity and post-vaccination for a better understanding and identification of these in the population. Publications from 2019 to 2022 were reviewed in PubMed as the primary search source.

Anti-cardiolipin IgG autoantibodies associate with circulating extracellular DNA in severe COVID-19

Whereas the detection of antiphospholipid autoantibodies (aPL) in COVID-19 is of increasing interest, their role is still unclear. We analyzed a large aPL panel in 157 patients with COVID-19 according to the disease severity. We also investigated a potential association between aPL and extracellular DNA (exDNA, n = 85) or circulating markers of neutrophil extracellular traps (NET) such as citrullinated histones H3 (CitH3, n = 49). A total of 157 sera of patients infected by SARS-CoV-2 were collected. A large aPL panel including lupus anticoagulant, anti-cardiolipin and anti-beta-2 glycoprotein I (IgG, IgM and IgA), anti-phosphatidylethanolamine IgA, anti-prothrombin (IgG and IgM) was retrospectively analyzed according to the disease severity. We found a total aPL prevalence of 54.8% with almost half of the cases having aCL IgG. Within an extended panel of aPL, only aCL IgG were associated with COVID-19 severity. Additionally, severe patients displayed higher CitH3 levels than mild patients. Interestingly, we highlighted a significant association between the levels of aCL IgG and exDNA only in aCL positive patients with severe disease. In conclusion, we showed a significant link between aPL, namely aCL IgG, and circulating exDNA in patients with severe form of COVID-19, that could exacerbate the thrombo-inflammatory state related to disease severity.

SARS-CoV-2 infection relaxes peripheral B cell tolerance

Severe SARS-CoV-2 infection is associated with strong inflammation and autoantibody production against diverse self-antigens, suggesting a system-wide defect in B cell tolerance. BND cells are a B cell subset in healthy individuals harboring autoreactive but anergic B lymphocytes. In vitro evidence suggests inflammatory stimuli can breach peripheral B cell tolerance in this subset. We asked whether SARS-CoV-2-associated inflammation impairs BND cell peripheral tolerance. To address this, PBMCs and plasma were collected from healthy controls, individuals immunized against SARS-CoV-2, or subjects with convalescent or severe SARS-CoV-2 infection. We demonstrate that BND cells from severely infected individuals are significantly activated, display reduced inhibitory receptor expression, and restored BCR signaling, indicative of a breach in anergy during viral infection, supported by increased levels of autoreactive antibodies. The phenotypic and functional BND cell alterations significantly correlate with increased inflammation in severe SARS-CoV-2 infection. Thus, autoreactive BND cells are released from peripheral tolerance with SARS-CoV-2 infection, likely as a consequence of robust systemic inflammation.

Mechanisms of Immune Dysregulation in COVID-19 Are Different From SARS and MERS: A Perspective in Context of Kawasaki Disease and MIS-C

Coronaviruses have led to three major outbreaks to date-Severe Acute Respiratory Syndrome (SARS; 2002), Middle East Respiratory Syndrome (MERS; 2012) and the ongoing pandemic, Coronavirus Disease (COVID-19; 2019). Coronavirus infections are usually mild in children. However, a few children with MERS had presented with a severe phenotype in the acute phase resulting in progressive pneumonic changes with increasing oxygen dependency and acute respiratory distress requiring ventilatory support. A subset of children with a history of SARS-CoV-2 infection develops a multisystem hyper-inflammatory phenotype known as Multisystem Inflammatory Syndrome in Children (MIS-C). This syndrome occurs 4-6 weeks after infection with SARS-CoV-2 and has been reported more often from areas with high community transmission. Children with MIS-C present with high fever and often have involvement of cardiovascular, gastrointestinal and hematologic systems leading to multiorgan failure. This is accompanied by elevation of pro-inflammatory cytokines such as IL-6 and IL-10. MIS-C has several similarities with Kawasaki disease (KD) considering children with both conditions present with fever, rash, conjunctival injection, mucosal symptoms and swelling of hands and feet. For reasons that are still not clear, both KD and MIS-C were not reported during the SARS-CoV and MERS-CoV outbreaks. As SARS-CoV-2 differs from SARS-CoV by 19.5% and MERS by 50% in terms of sequence identity, differences in genomic and proteomic profiles may explain the varied disease immunopathology and host responses. Left untreated, MIS-C may lead to severe abdominal pain, ventricular dysfunction and shock. Immunological investigations reveal reduced numbers of follicular B cells, increased numbers of terminally differentiated CD4+T lymphocytes, and decreased IL-17A. There is still ambiguity about the clinical and immunologic risk factors that predispose some children to development of MIS-C while sparing others. Host-pathogen interactions in SARS, MERS and COVID-19 are likely to play a crucial role in the clinical phenotypes that manifest. This narrative review focuses on the immunological basis for development of MIS-C syndrome in the ongoing SARS-CoV-2 pandemic. To the best of our knowledge, these aspects have not been reviewed before.

The Swine IFN System in Viral Infections: Major Advances and Translational Prospects

Interferons (IFNs) are a family of cytokines that play a pivotal role in orchestrating the innate immune response during viral infections, thus representing the first line of defense in the host. After binding to their respective receptors, they are able to elicit a plethora of biological activities, by initiating signaling cascades which lead to the transcription of genes involved in antiviral, anti-inflammatory, immunomodulatory and antitumoral effector mechanisms. In hindsight, it is not surprising that viruses have evolved multiple IFN escape strategies toward efficient replication in the host. Hence, in order to achieve insight into preventive and treatment strategies, it is essential to explore the mechanisms underlying the IFN response to viral infections and the constraints thereof. Accordingly, this review is focused on three RNA and three DNA viruses of major importance in the swine farming sector, aiming to provide essential data as to how the IFN system modulates the antiviral immune response, and is affected by diverse, virus-driven, immune escape mechanisms.

Diet and Hygiene in Modulating Autoimmunity During the Pandemic Era

The immune system is an efficiently toned machinery that discriminates between friends and foes for achieving both host defense and homeostasis. Deviation of immune recognition from foreign to self and/or long-lasting inflammatory responses results in the breakdown of tolerance. Meanwhile, educating the immune system and developing immunological memory are crucial for mounting defensive immune responses while protecting against autoimmunity. Still to elucidate is how diverse environmental factors could shape autoimmunity. The emergence of a world pandemic such as SARS-CoV-2 (COVID-19) not only threatens the more vulnerable individuals including those with autoimmune conditions but also promotes an unprecedented shift in people's dietary approaches while urging for extraordinary hygiene measures that likely contribute to the development or exacerbation of autoimmunity. Thus, there is an urgent need to understand how environmental factors modulate systemic autoimmunity to better mitigate the incidence and or severity of COVID-19 among the more vulnerable populations. Here, we discuss the effects of diet (macronutrients and micronutrients) and hygiene (the use of disinfectants) on autoimmunity with a focus on systemic lupus erythematosus.

The majority of SARS-CoV-2-specific antibodies in COVID-19 patients with obesity are autoimmune and not neutralizing

BACKGROUND/OBJECTIVES

Obesity decreases the secretion of SARS-CoV-2-specific IgG antibodies in the blood of COVID-19 patients. How obesity impacts the quality of the antibodies secreted, however, is not understood. Therefore, the objective of this study is to evaluate the presence of neutralizing versus autoimmune antibodies in COVID-19 patients with obesity.

SUBJECTS/METHODS

Thirty serum samples from individuals who tested positive for SARS-CoV-2 infection by RT-PCR were collected from inpatient and outpatient settings. Of these, 15 were lean (BMI < 25) and 15 were obese (BMI ≥ 30). Control serum samples were from 30 uninfected individuals, age-, gender-, and BMI-matched, recruited before the current pandemic. Neutralizing and autoimmune antibodies were measured by ELISA. IgG autoimmune antibodies were specific for malondialdehyde (MDA), a marker of oxidative stress and lipid peroxidation, and for adipocyte-derived protein antigens (AD), markers of virus-induced cell death in the obese adipose tissue.

RESULTS

SARS-CoV-2 infection induces neutralizing antibodies in all lean but only in few obese COVID-19 patients. SARS-CoV-2 infection also induces anti-MDA and anti-AD autoimmune antibodies more in lean than in obese patients as compared to uninfected controls. Serum levels of these autoimmune antibodies, however, are always higher in obese versus lean COVID-19 patients. Moreover, because the autoimmune antibodies found in serum samples of COVID-19 patients have been correlated with serum levels of C-reactive protein (CRP), a general marker of inflammation, we also evaluated the association of anti-MDA and anti-AD antibodies with serum CRP and found a positive association between CRP and autoimmune antibodies.

CONCLUSIONS

Our results highlight the importance of evaluating the quality of the antibody response in COVID-19 patients with obesity, particularly the presence of autoimmune antibodies, and identify biomarkers of self-tolerance breakdown. This is crucial to protect this vulnerable population at higher risk of responding poorly to infection with SARS-CoV-2 than lean controls.

The direct and indirect effects of bioactive compounds against coronavirus

Emerging viruses are known to pose a threat to humans in the world. COVID‐19, a newly emerging viral respiratory disease, can spread quickly from people to people via respiratory droplets, cough, sneeze, or exhale. Up to now, there are no specific therapies found for the treatment of COVID‐19. In this sense, the rising demand for effective antiviral drugs is stressed. The main goal of the present study is to cover the current literature about bioactive compounds (e.g., polyphenols, glucosinolates, carotenoids, minerals, vitamins, oligosaccharides, bioactive peptides, essential oils, and probiotics) with potential efficiency against COVID‐19, showing antiviral activities via the inhibition of coronavirus entry into the host cell, coronavirus enzymes, as well as the virus replication in human cells. In turn, these compounds can boost the immune system, helping fight against COVID‐19. Overall, it can be concluded that bioactives and the functional foods containing these compounds can be natural alternatives for boosting the immune system and defeating coronavirus.

Emerging Roles of Coronavirus in Autoimmune Diseases

Virus infection can alter immune regulatory activity, and thus may be involved in the occurrence of autoimmune diseases. Recently, the pandemic of COVID-19 has posed a huge threat to public health and emerging evidence suggests that coronavirus may be implicated in the development and pathogenesis of autoimmune diseases. However, how coronavirus infection impacts the risk of autoimmune disease remains largely unknown. In this review, we focused on the association between coronavirus and autoimmunity, and elucidated the molecular mechanisms linking coronavirus exposure to autoimmunity. Additionally, we briefly introduced the role that coronavirus plays in several autoimmune diseases including multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and idiopathicthrombocytopenic purpura (ITP).

Pathology of the Brain and the Eye in Severe Acute Respiratory Syndrome Coronavirus-2-Infected Patients: A Review

BACKGROUND

Patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may present or eventually develop central nervous system and ophthalmic signs and symptoms. Varying reports have emerged regarding isolation of viral RNA from these tissue sites, as well as largely autopsy-based histopathologic descriptions of the brain and the eye in patients with COVID-19.

EVIDENCE ACQUISITION

A primary literature search was performed in literature databases such as PubMed, Google Scholar, and Cochrane Library. Keywords were used alone and in combination including the following: SARS CoV-2, COVID-19, eye, brain, central nervous system, histopathology, autopsy, ocular pathology, aqueous, tears, vitreous, neuropathology, and encephalitis.

RESULTS

The reported ophthalmic pathologic and neuropathologic findings in patients with SARS-CoV-2 are varied and inconclusive regarding the role of direct viral infection vs secondary pathology. The authors own experience with autopsy neuropathology in COVID-19 patients is also described. There is a particular paucity of data regarding the histopathology of the eye. However, it is likely that the ocular surface is a potential site for inoculation and the tears a source of spread of viral particles.

CONCLUSIONS

Additional large postmortem studies are needed to clarify the role of SARS-CoV in the ophthalmic and neuropathologic manifestations of COVID-19.

Untangling COVID-19 and autoimmunity: Identification of plausible targets suggests multi organ involvement

Underlying mechanisms of multi-organ manifestations and exacerbated inflammation in COVID-19 are yet to be delineated. The hypothesis of SARS-CoV-2 triggering autoimmunity is gaining attention and, in the present study, we have identified 28 human proteins harbouring regions homologous to SARS-CoV-2 peptides that could possibly be acting as autoantigens in COVID-19 patients displaying autoimmune conditions. Interestingly, these conserved regions are amongst the experimentally validated B cell epitopes of SARS-CoV-2 proteins. The reported human proteins have demonstrated presence of autoantibodies against them in typical autoimmune conditions which may explain the frequent occurrence of autoimmune conditions following SARS-CoV-2 infection. Moreover, the proposed autoantigens' widespread tissue distribution is suggestive of their involvement in multi-organ manifestations via molecular mimicry. We opine that our report may aid in directing subsequent necessary antigen-specific studies, results of which would be of long-term relevance in management of extrapulmonary symptoms of COVID-19.

Transcriptomic Signature Differences Between SARS-CoV-2 and Influenza Virus Infected Patients

The reason why most individuals with COVID-19 have relatively limited symptoms while other develop respiratory distress with life-threatening complications remains unknown. Increasing evidence suggests that COVID-19 associated adverse outcomes mainly rely on dysregulated immunity. Here, we compared transcriptomic profiles of blood cells from 103 patients with different severity levels of COVID-19 with that of 27 healthy and 22 influenza-infected individuals. Data provided a complete overview of SARS-CoV-2-induced immune signature, including a dramatic defect in IFN responses, a reduction of toxicity-related molecules in NK cells, an increased degranulation of neutrophils, a dysregulation of T cells, a dramatic increase in B cell function and immunoglobulin production, as well as an important over-expression of genes involved in metabolism and cell cycle in patients infected with SARS-CoV-2 compared to those infected with influenza viruses. These features also differed according to COVID-19 severity. Overall and specific gene expression patterns across groups can be visualized on an interactive website (https://bix.unil.ch/covid/). Collectively, these transcriptomic host responses to SARS-CoV-2 infection are discussed in the context of current studies, thereby improving our understanding of COVID-19 pathogenesis and shaping the severity level of COVID-19.

SARS-CoV-2 infection induces autoimmune antibody secretion more in lean than in obese COVID-19 patients

BACKGROUND/OBJECTIVES

Obesity decreases the secretion of SARS-CoV-2-specific IgG antibodies in the blood of COVID-19 patients. How obesity impacts the secretion of autoimmune antibodies in COVID-19 patients, however, is not understood. The serum of adult COVID-19 patients contains autoimmune antibodies generated in response to virus-induced tissue damage and cell death leading to the release of intracellular antigens not known to be immunogenic autoantigens. The objective of this study is to evaluate the presence of autoimmune antibodies in COVID-19 patients with obesity.

SUBJECTS/METHODS

Thirty serum samples from individuals who tested positive for SARS-CoV-2 infection by RT-PCR were collected from inpatient and outpatient settings. Of these, 15 were lean (BMI<25), and 15 were obese (BMI ≥30). Control serum samples were from 30 uninfected individuals, age-gender- and BMI-matched, recruited before the current pandemic. Serum IgG antibodies against two autoimmune specificities, as well as against SARS-CoV-2 Spike protein, were measured by ELISA. IgG autoimmune antibodies were specific for malondialdehyde (MDA), a marker of oxidative stress and lipid peroxidation, and for adipocyte-derived protein antigens (AD), markers of virus-induced cell death in the obese AT.

RESULTS

Our results show that SARS-CoV-2 infection induces anti-MDA and anti-AD autoimmune antibodies more in lean than in obese patients as compared to uninfected controls. Serum levels of these autoimmune antibodies, however, are always higher in obese versus lean COVID-19 patients. Moreover, because the autoimmune antibodies found in serum samples of COVID-19 patients have been correlated with serum levels of C-reactive protein (CRP), a general marker of inflammation, we also evaluated the association of anti-MDA and anti-AT antibodies with serum CRP and found a significant association between CRP and autoimmune antibodies in our cohort of lean and obese COVID-19 patients.

CONCLUSIONS

Our results highlight the importance of evaluating the quality of the antibody response in COVID-19 patients with obesity, particularly the presence of autoimmune antibodies, and identify biomarkers of self-tolerance breakdown. This is crucial to protect this vulnerable population that is at higher risk of responding poorly to infection with SARS-CoV-2 compared to lean controls.

Coronavirus-induced autoimmunity

The pandemic of Coronavirus disease 2019 (COVID-19), caused by a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spotlighted the link between viral infection and autoimmunity. In this review, we focus on coronavirus-induced autoimmunity based on evidence from experimental animal models, SARS-CoV infection with in vitro studies of molecular mimicry and COVID-19 with several clinical reports of autoimmune manifestations of this disease. Further studies will be needed to better characterize the role of SARS-CoV-2 in the development of autoimmunity.

A useful and sensitive marker in the prediction of COVID-19 and disease severity: Thiol

Thiol-disulphide homeostasis (TDH) is a new parameter indicating oxidative stress that plays a role in the pathogenesis of various clinical disorders. Our study planned to investigate TDH in COVID-19 patients. Age and gender-matched healthy subjects (n = 70) and COVID-19 patients (n = 144) were included in the study. In addition to the routine laboratory parameters of the groups, their native thiol (NT), total thiol (TT) and disulphide levels were measured. Primarily, we compared COVID-19 patients to the healthy control group for inflammatory parameters, NT, TT and disulphide levels. Then, COVID-19 patients were divided into two groups according to the severity of the disease as mild to moderate and severe COVID-19, and the three groups were compared with each other. Predictive value of thiol parameters in the diagnosis of COVID-19 and in the determining its severity, and its correlation with presence and duration of symptoms were investigated. Severe COVID-19 patients had lower NT and TT levels compared with healthy controls and mild to moderate patients (P < 0.001 for both). The results of ROC analysis show that the greatest AUC was IL-6 and NT (AUC = 0.97, AUC = 0.96, respectively) between control and COVID-19 patients, while it was CRP and NT (AUC = 0.85, AUC = 0.83) between mild to moderate and severe patients. A negative correlation was found between duration of symptoms of dyspnoea, cough, fever, and sore throat and NT (r = -0.45, P = 0.017, r = -0.418, P < 0.001, r = -0.131, P = 0.084, r = -0.452, P = 0.040, respectively). NT and TT levels have a strong predictive value in the diagnosis of COVID-19 and in determining disease severity. Our results support that changing TDH parameters appears to have an important role in disease pathogenesis and it can be used in clinical management of patients.

Domains and Functions of Spike Protein in Sars-Cov-2 in the Context of Vaccine Design

The spike protein in SARS-CoV-2 (SARS-2-S) interacts with the human ACE2 receptor to gain entry into a cell to initiate infection. Both Pfizer/BioNTech's BNT162b2 and Moderna's mRNA-1273 vaccine candidates are based on stabilized mRNA encoding prefusion SARS-2-S that can be produced after the mRNA is delivered into the human cell and translated. SARS-2-S is cleaved into S1 and S2 subunits, with S1 serving the function of receptor-binding and S2 serving the function of membrane fusion. Here, I dissect in detail the various domains of SARS-2-S and their functions discovered through a variety of different experimental and theoretical approaches to build a foundation for a comprehensive mechanistic understanding of how SARS-2-S works to achieve its function of mediating cell entry and subsequent cell-to-cell transmission. The integration of structure and function of SARS-2-S in this review should enhance our understanding of the dynamic processes involving receptor binding, multiple cleavage events, membrane fusion, viral entry, as well as the emergence of new viral variants. I highlighted the relevance of structural domains and dynamics to vaccine development, and discussed reasons for the spike protein to be frequently featured in the conspiracy theory claiming that SARS-CoV-2 is artificially created.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): Codon Usage and Replicative Fitness

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) codon usage, as shown by the polyprotein coding sequence, shows better translation potential in the human host when compared with human coronavirus OC43 (HCoV-OC43) codon usage. Such translational advantage might facilitate SARS-CoV-2 replication, immunogenicity, and pathogenicity, thus also accounting for the less harmful character of HCoV-OC43 infection.

Invited Review: The spectrum of neuropathology in COVID-19

There is increasing evidence that patients with Coronavirus disease 19 (COVID-19) present with neurological and psychiatric symptoms. Anosmia, hypogeusia, headache, nausea and altered consciousness are commonly described, although there are emerging clinical reports of more serious and specific conditions such as acute cerebrovascular accident, encephalitis and demyelinating disease. Whether these presentations are directly due to viral invasion of the central nervous system (CNS) or caused by indirect mechanisms has yet to be established. Neuropathological examination of brain tissue at autopsy will be essential to establish the neuro-invasive potential of the SARS-CoV-2 virus but, to date, there have been few detailed studies. The pathological changes in the brain probably represent a combination of direct cytopathic effects mediated by SARS-CoV-2 replication or indirect effects due to respiratory failure, injurious cytokine reaction, reduced immune response and cerebrovascular accidents induced by viral infection. Further large-scale molecular and cellular investigations are warranted to clarify the neuropathological correlates of the neurological and psychiatric features seen clinically in COVID-19. In this review, we summarize the current reports of neuropathological examination in COVID-19 patients, in addition to our own experience, and discuss their contribution to the understanding of CNS involvement in this disease.

A systematic review of antibody mediated immunity to coronaviruses: kinetics, correlates of protection, and association with severity

Many public health responses and modeled scenarios for COVID-19 outbreaks caused by SARS-CoV-2 assume that infection results in an immune response that protects individuals from future infections or illness for some amount of time. The presence or absence of protective immunity due to infection or vaccination (when available) will affect future transmission and illness severity. Here, we review the scientific literature on antibody immunity to coronaviruses, including SARS-CoV-2 as well as the related SARS-CoV, MERS-CoV and endemic human coronaviruses (HCoVs). We reviewed 2,452 abstracts and identified 491 manuscripts relevant to 5 areas of focus: 1) antibody kinetics, 2) correlates of protection, 3) immunopathogenesis, 4) antigenic diversity and cross-reactivity, and 5) population seroprevalence. While further studies of SARS-CoV-2 are necessary to determine immune responses, evidence from other coronaviruses can provide clues and guide future research.

Lymphopenia an important immunological abnormality in patients with COVID-19: Possible mechanisms

The lymphopenia as a major immunological abnormality occurs in the majority of severe COVID-19 patients, which is strongly associated with mortality rate. A low proportion of lymphocytes may express the main receptor for SARS-CoV-2, called angiotensin-converting enzyme 2 (ACE2). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can also use ACE2-independent pathways to enter lymphocytes. Both SARS-CoV-2- and immune-mediated mechanisms may contribute to the occurrence of lymphopenia through influencing the lymphocyte production, survival or tissue re-distribution. The metabolic and biochemical changes can also affect the production and survival of lymphocytes in COVID-19 patients. Lymphopenia can cause general immunosuppression and promote cytokine storm, both of them play an important role in the viral persistence, viral replication, multi-organ failure and eventually death. Here, a comprehensive view concerning the possible mechanisms that may lead to the lymphocyte reduction in COVID-19 patients is provided, while highlighting the potential intervention approaches to prevent lymphopenia.

Understanding immunopathological fallout of human coronavirus infections including COVID-19: Will they cross the path of rheumatologists?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causing coronavirus disease 2019 (COVID-19) is the biggest pandemic of our lifetime to date. No effective treatment is yet in sight for this catastrophic illness. Several antiviral agents and vaccines are in clinical trials, and drug repurposings as immediate and alternative choices are also under consideration. Immunomodulatory agents like hydroxychloroquine (HCQ) as well as biological disease-modifying anti-rheumatic drugs (bDMARDs) such as tocilizumab and anakinra received worldwide attention for treatment of critical patients with COVID-19. This is of interest to rheumatologists, who are well versed with rational use of these agents. This brief review addresses the understandings of some of the common immunopathogenetic mechanisms in the context of autoimmune rheumatic diseases like systemic lupus erythematosus (SLE) and COVID-19. Apart from demographic comparisons, the role of type I interferons (IFN), presence of antiphospholipid antibodies and finally mechanism of action of HCQ in both the scenarios are discussed here. High risks for fatal disease in COVID-19 include older age, metabolic syndrome, male gender, and individuals who develop delayed type I IFN response. HCQ acts by different mechanisms including prevention of cellular entry of SARS-CoV-2 and inhibition of type I IFN signaling. Recent controversies regarding efficacy of HCQ in management of COVID-19 warrant more studies in that direction. Autoantibodies were also reported in severe acute respiratory syndrome (SARS) as well as in COVID-19. Rheumatologists need to wait and see whether SARS-CoV-2 infection triggers development of autoimmunity in patients with COVID-19 infection in the long run.

SARS-CoV-2: A Piece of Bad News

A shocking third species emerged from a family of coronaviruses (CoV) in late 2019 following viruses causing SARS (Severe Acute Respiratory Syndrome-CoV) in 2003 and MERS (Middle East Respiratory Syndrome-CoV) in 2012; it's a novel coronavirus now called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; formerly called 2019-nCoV). First emerging in China, it has spread rapidly across the globe, giving rise to significant social and economic costs and imposing severe strain on healthcare systems. Since many attempts to control viral spread has been futile, the only old practice of containment including city lockdown and social distancing are working to some extent. Unfortunately, specific antiviral drugs and vaccines remain unavailable yet. Many factors are encountered to play essential roles in viral pathogenesis. These include a broad viral-host range with high receptor binding affinity to various human tissues, viral adaptation to humans, a high percentage of asymptomatic but infected carriers, prolonged incubation, and viral shedding periods. There are also a wide variety of pulmonary and extrapul-monary tissue damage mechanisms including direct cell injury or immune-mediated damages involving the immune cells, upregulation of proinflammatory cytokines, and antibody dependent enhancement that can result in multi-organ failure. In this article, we summarise some evidence on the various steps in SARS-CoV-2 pathogenesis and immune evasion strategies to assess their contribution to our understanding of unresolved problems related to SARS-CoV-2 prevention, control, and treatment protocols.

Clinical and Autoimmune Characteristics of Severe and Critical Cases of COVID-19

In this study we report on the clinical and autoimmune characteristics of severe and critical novel coronavirus pneumonia caused by severe acute respiratory syndrome‒associated coronavirus 2 (SARS‐CoV‐2). The clinical, autoimmune, and laboratory characteristics of 21 patients who had laboratory‐confirmed severe and critical cases of coronavirus disease 2019 (COVID‐19) from the intensive care unit of the Huangshi Central Hospital, Hubei Province, China, were investigated. A total of 21 patients (13 men and 8 women), including 8 (38.1%) severe cases and 13 (61.9%) critical cases, were enrolled. Cough (90.5%) and fever (81.0%) were the dominant symptoms, and most patients (76.2%) had at least one coexisting disorder on admission. The most common characteristics on chest computed tomography were ground‐glass opacity (100%) and bilateral patchy shadowing (76.2%). The most common findings on laboratory measurement were lymphocytopenia (85.7%) and elevated levels of C‐reactive protein (94.7%) and interleukin‐6 (89.5%). The prevalence of anti‒52 kDa SSA/Ro antibody, anti‒60 kDa SSA/Ro antibody, and antinuclear antibody was 20%, 25%, and 50%, respectively. We also retrospectively analyzed the clinical and laboratory data from 21 severe and critical cases of COVID‐19. Autoimmune phenomena exist in COVID‐19 subjects, and the present results provide the rationale for a strategy of preventing immune dysfunction and optimal immunosuppressive therapy.

A systematic review of antibody mediated immunity to coronaviruses: antibody kinetics, correlates of protection, and association of antibody responses with severity of disease

The duration and nature of immunity generated in response to SARS-CoV-2 infection is unknown. Many public health responses and modeled scenarios for COVID-19 outbreaks caused by SARSCoV-2 assume that infection results in an immune response that protects individuals from future infections or illness for some amount of time. The timescale of protection is a critical determinant of the future impact of the pathogen. The presence or absence of protective immunity due to infection or vaccination (when available) will affect future transmission and illness severity. The dynamics of immunity and nature of protection are relevant to discussions surrounding therapeutic use of convalescent sera as well as efforts to identify individuals with protective immunity. Here, we review the scientific literature on antibody immunity to coronaviruses, including SARS-CoV-2 as well as the related SARS-CoV-1, MERS-CoV and human endemic coronaviruses (HCoVs). We reviewed 1281 abstracts and identified 322 manuscripts relevant to 5 areas of focus: 1) antibody kinetics, 2) correlates of protection, 3) immunopathogenesis, 4) antigenic diversity and cross-reactivity, and 5) population seroprevalence. While studies of SARS-CoV-2 are necessary to determine immune responses to it, evidence from other coronaviruses can provide clues and guide future research.

Involvement of the Nervous System in SARS-CoV-2 Infection

As a severe and highly contagious infectious disease, coronavirus disease 2019 (COVID-19) has caused a global pandemic. Several case reports have demonstrated that the respiratory system is the main target in patients with COVID-19, but the disease is not limited to the respiratory system. Case analysis indicated that the nervous system can be invaded by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and that 36.4% of COVID-19 patients had neurological symptoms. Importantly, the involvement of the CNS may be associated with poor prognosis and disease worsening. Here, we discussed the symptoms and evidence of nervous system involvement (directly and indirectly) caused by SARS-CoV-2 infection and possible mechanisms. CNS symptoms could be a potential indicator of poor prognosis; therefore, the prevention and treatment of CNS symptoms are also crucial for the recovery of COVID-19 patients.

Correlation between serum levels of anti-endothelial cell autoantigen and anti-dengue virus nonstructural protein 1 antibodies in dengue patients

We have previously shown that anti-dengue virus nonstructural protein 1 (anti-DENV NS1) antibodies cross-react with endothelial cells, and several autoantigens have been identified. This study shows that the antibody levels against these self-proteins are higher in sera from patients with dengue hemorrhagic fever (DHF) than those in control sera. Anti-protein disulfide isomerase (PDI) and anti-heat shock protein 60 (anti-HSP60) IgM levels correlated with both anti-endothelial cells and anti-DENV NS1 IgM titers. A cross-reactive epitope on the NS1 amino acid residues 311-330 (P311-330) had been predicted. We further found that there were higher IgM and IgG levels against P311-330 in DHF patients' sera than those in the control sera. In addition, correlations were observed between anti-PDI with anti-P311-330 IgM and IgG levels, respectively. Therefore, our results indicate that DENV NS1 P311-330 is a major epitope for cross-reactive antibodies to PDI on the endothelial cell surface, which may play an important role in DENV infection-induced autoimmunity.

Neutralizing human monoclonal antibodies to severe acute respiratory syndrome coronavirus: target, mechanism of action, and therapeutic potential

The emergence of Severe Acute Respiratory Syndrome Coronavirus (SARS‐CoV) led to a rapid response not only to contain the outbreak but also to identify possible therapeutic interventions, including the generation of human monoclonal antibodies (hmAbs). hmAbs may be used therapeutically without the drawbacks of chimeric or animal Abs. Several different methods have been used to generate SARS‐CoV specific neutralizing hmAbs including the immunization of transgenic mice, cloning of small chain variable regions from naïve and convalescent patients, and the immortalization of convalescent B cells. Irrespective of the techniques used, the majority of hmAbs specifically reacted with the receptor binding domain (RBD) of the spike (S) protein and likely prevented receptor binding. However, several hmAbs that can bind to epitopes either within the RBD, located N terminal of the RBD or in the S2 domain, and neutralize the virus with or without inhibiting receptor binding have been identified. Therapeutic utility of hmAbs has been further elucidated through the identification of potential combinations of hmAbs that could neutralize viral variants including escape mutants selected using hmAbs. These results suggest that a cocktail of hmAbs that can bind to unique epitopes and have different mechanisms of action might be of clinical utility against SARS‐CoV infection, and indicate that a similar approach may be applied to treat other viral infections. Copyright © 2011 John Wiley & Sons, Ltd.

Down-regulation of granulocyte-macrophage colony-stimulating factor by 3C-like proteinase in transfected A549 human lung carcinoma cells

Background

Severe Acute Respiratory Syndrome (SARS) is a severe respiratory illness caused by a novel virus, the SARS coronavirus (SARS-CoV). 3C-like protease (3CL^pro) of SARS-CoV plays a role in processing viral polypeptide precursors and is responsible of viral maturation. However, the function of 3CL^pro in host cells remains unknown. This study investigated how the 3CL^pro affected the secretion of cytokines in the gene-transfected cells.

Results

From immunofluorescence microscopy, the localization of c-myc tagged 3CL^pro was detected both in the cytoplasm and nucleus of transfected A549 cells. Expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) was significantly decreased in 3CL^pro-transfected cells by both RT-PCR and ELISA, but without changes in other cytokines, i.e., IL-1β, IL-6, IL-8, IL12p40, TNF-α, and TGF-β. Furthermore, the protein levels of NF-kB decreased in 3CL^pro-transfected A549 cells when compared to EGFP transfected cells.

Conclusions

Our results suggest that the 3CL^pro may suppress expression of GM-CSF in transfected A549 cells through down-regulation of NF-kB production.

Annexin A2 on lung epithelial cell surface is recognized by severe acute respiratory syndrome-associated coronavirus spike domain 2 antibodies

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection causes lung failure characterized by atypical pneumonia. We previously showed that antibodies against SARS-CoV spike domain 2 (S2) in the patient sera can cross-react with human lung epithelial cells; however, the autoantigen is not yet identified. In this study, we performed proteomic studies and identified several candidate autoantigens recognized by SARS patient sera in human lung type II epithelial cell A549. Among the candidate proteins, annexin A2, which was identified by mass spectrometry analysis and had the highest score by Mascot data search, was further characterized and investigated for its role as an autoantigen. By confocal microscopic observation, SARS patient sera and anti-S2 antibodies were co-localized on A549 cells and both of them were co-localized with anti-annexin A2 antibodies. Anti-annexin A2 antibodies bound to purified S2 proteins, and anti-S2 bound to immunoprecipitated annexin A2 from A549 cell lysate in a dose-dependent manner. Furthermore, an increased surface expression and raft-structure distribution of annexin A2 was present in A549 cells after stimulation with SARS-induced cytokines interleukin-6 and interferon-gamma. Cytokine stimulation increased the binding capability of anti-S2 antibodies to human lung epithelial cells. Together, the upregulated expression of annexin A2 by SARS-associated cytokines and the cross-reactivity of anti-SARS-CoV S2 antibodies to annexin A2 may have implications in SARS disease pathogenesis.

Proteomic Analysis of Endothelial Cell Autoantigens Recognized by Anti-Dengue Virus Nonstructural Protein 1 Antibodies

We previously showed the occurrence of autoimmune responses in dengue virus (DV) infection, which has potential implications for the pathogenesis of dengue hemorrhagic syndrome. In the present study, we have used a proteomic analysis to identify several candidate proteins on HMEC-1 endothelial cells recognized by anti-DV nonstructural protein 1 (NS1) antibodies. The target proteins, including ATP synthase β chain, protein disulfide isomerase, vimentin, and heat shock protein 60, co-localize with anti-NS1 binding sites on nonfixed HMEC-1 cells using immunohistochemical double staining and confocal microscopy. The cross-reactivity of anti-target protein antibodies with HMEC-1 cells was inhibited by NS1 protein pre-absorption. Furthermore, a cross-reactive epitope on NS1 amino acid residues 311–330 (P311–330) was predicted using homologous sequence alignment. The reactivity of dengue hemorrhagic patient sera with HMEC-1 cells was blocked by synthetic peptide P311–330 pre-absorption. Taken together, our results identify putative targets on endothelial cells recognized by anti-DV NS1 antibodies, where NS1 P311–330 possesses the shared epitope.

Recent antiviral strategies against human coronavirus-related respiratory illnesses

PURPOSE OF REVIEW

The main purpose of this review is to summarize the current research (2006-2007) concerning the development of novel anticoronaviral strategies and compounds.

RECENT FINDINGS

Recent research led to the identification of several novel agents inhibiting coronaviral replication. The most promising compounds include carbohydrate-binding agents, neutralizing antibodies and drugs targeting a coronaviral envelope protein.

SUMMARY

Although initial outbreaks of coronavirus that causes severe acute respiratory syndrome (SARS-CoV) were controlled by public health measures, the development of vaccines and antiviral agents for SARS-CoV is essential for improving control and treatment of future outbreaks. Four years after the SARS-CoV epidemic, several compounds with an anticoronaviral activity have been identified.

Pathogenetic mechanisms of severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is an acute respiratory disease with significant morbidity and mortality. While its clinical manifestations have been extensively studied, its pathogenesis is not yet fully understood. A limited number of autopsy studies have revealed that the lungs and the immune system are the organs that sustain the most severe damage. Other organs affected include the kidneys, brain, digestive tract, heart, liver, thyroid gland and urogenital tract. The primary target cells are pneumocytes and enterocytes, both cell types abundantly expressing angiotensin-converting enzyme 2 which is the main SARS-CoV receptor. Other cell types infected include the epithelial cells of renal tubules, cerebral neurons, and immune cells. The pathology of this disease results from both direct and indirect injury. Direct injury is caused by infection of the target cells by the virus. Indirect injury mainly results from immune responses, circulatory dysfunction, and hypoxia. In this review, we summarize the major pathological findings at the gross, cellular and molecular levels and discuss the various possible mechanisms that may contribute to the pathogenesis of SARS. The implications of the proposed pathogenesis for prevention, diagnosis and therapy of the disease are discussed.

Emergence of anti-red blood cell antibodies triggers red cell phagocytosis by activated macrophages in a rabbit model of Epstein-Barr virus-associated hemophagocytic syndrome

Hemophagocytic syndrome (HPS) is a fatal complication frequently associated with viral infections. In childhood HPS, Epstein-Barr virus (EBV) is the major causative agent, and red blood cells (RBCs) are predominantly phagocytosed by macrophages. To investigate the mechanism of RBC phagocytosis triggered by EBV infection, we adopted a rabbit model of EBV-associated HPS previously established by using Herpesvirus papio (HVP). The kinetics of virus-host interaction was studied. Using flow cytometry, we detected the emergence of antibody-coated RBCs, as well as anti-platelet antibodies, at peak virus load period at weeks 3 to 4 after HVP injection, and the titers increased thereafter. The presence of anti-RBCs preceded RBC phagocytosis in tissues and predicted the full-blown development of HPS. The anti-RBC antibodies showed cross-reactivity with Paul-Bunnell heterophile antibodies. Preabsorption of the HVP-infected serum with control RBCs removed the majority of anti-RBC activities and remarkably reduced RBC phagocytosis. The RBC phagocytosis was specifically mediated via an Fc fragment of antibodies in the presence of macrophage activation. Therefore, the emergence of anti-RBC antibodies and the presence of macrophage activation are both essential in the development of HPS. Our observations in this animal model provide a potential mechanism for hemophagocytosis in EBV infection.

Pathology and pathogenesis of severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is an emerging infectious viral disease characterized by severe clinical manifestations of the lower respiratory tract. The pathogenesis of SARS is highly complex, with multiple factors leading to severe injury in the lungs and dissemination of the virus to several other organs. The SARS coronavirus targets the epithelial cells of the respiratory tract, resulting in diffuse alveolar damage. Several organs/cell types may be infected in the course of the illness, including mucosal cells of the intestines, tubular epithelial cells of the kidneys, neurons of the brain, and several types of immune cells, and certain organs may suffer from indirect injury. Extensive studies have provided a basic understanding of the pathogenesis of this disease. In this review we describe the most significant pathological features of SARS, explore the etiological factors causing these pathological changes, and discuss the major pathogenetic mechanisms. The latter include dysregulation of cytokines/chemokines, deficiencies in the innate immune response, direct infection of immune cells, direct viral cytopathic effects, down-regulation of lung protective angiotensin converting enzyme 2, autoimmunity, and genetic factors. It seems that both abnormal immune responses and injury to immune cells may be key factors in the pathogenesis of this new disease.

Generation and characterization of human monoclonal neutralizing antibodies with distinct binding and sequence features against SARS coronavirus using XenoMouse

Passive therapy with neutralizing human monoclonal antibodies (mAbs) could be an effective therapy against severe acute respiratory syndrome coronavirus (SARS-CoV). Utilizing the human immunoglobulin transgenic mouse, XenoMouse, we produced fully human SARS-CoV spike (S) protein specific antibodies. Antibodies were examined for reactivity against a recombinant S1 protein, to which 200 antibodies reacted. Twenty-seven antibodies neutralized 200TCID(50) SARS-CoV (Urbani). Additionally, 57 neutralizing antibodies were found that are likely specific to S2. Mapping of the binding region was achieved with several S1 recombinant proteins. Most S1 reactive neutralizing mAbs bound to the RBD, aa 318-510. However, two S1 specific mAbs reacted with a domain upstream of the RBD between aa 12 and 261. Immunoglobulin gene sequence analyses suggested at least 8 different binding specificities. Unique human mAbs could be used as a cocktail that would simultaneously target several neutralizing epitopes and prevent emergence of escape mutants.

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

Severe acute respiratory syndrome (SARS) is caused by a coronavirus (CoV), SARSCoV. SARS-CoV belongs to the family Coronaviridae, which are enveloped RNA viruses in the order Nidovirales. Global research efforts are continuing to increase the understanding of the virus, the pathogenesis of the disease it causes (SARS), and the “heterogeneity of individual infectiousness” as well as shedding light on how to prepare for other emerging viral diseases. Promising drugs and vaccines have been identified. The milestones achieved have resulted from a truly international effort. Molecular studies dissected the adaptation of this virus as it jumped from an intermediary animal, the civet, to humans, thus providing valuable insights into processes of molecular emergence.

Autoimmune Pathogenesis in Dengue Virus Infection

The pathogenic mechanisms of dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) caused by dengue virus (DV) infection remain unresolved. Patients with DHF/DSS are characterized by several manifestations, including severe thrombocytopenia, vascular leakage, and hepatomegaly. In addition to the effect of virus load and virus variation, abnormal immune responses of the host after DV infection may also account for the progression of DHF/DSS. Actually, viral autoimmunity is involved in the pathogenesis of numerous viral infections, such as human immunodeficiency virus, human hepatitis C virus, human cytomegalovirus, herpes simplex virus, Epstein- Barr virus, and DV. In this review, we discuss the implications of autoimmunity in dengue pathogenesis. Antibodies directed against DV nonstructural protein 1 (NS1) showed cross-reactivity with human platelets and endothelial cells, which lead to platelet and endothelial cell damage and inflammatory activation. Based on these findings, we hypothesize that anti-DV NS1 is involved in the pathogenesis of DF and DHF/DSS, and this may provide important information in dengue vaccine development.

Template-based coiled-coil antigens elicit neutralizing antibodies to the SARS-coronavirus

The Spike (S) glycoprotein of coronaviruses (CoV) mediates viral entry into host cells. It contains two hydrophobic heptad repeat (HR) regions, denoted HRN and HRC, which oligomerize the S glycoprotein into a trimer in the native state and when activated collapse into a six-helix bundle structure driving fusion of the host and viral membranes. Previous studies have shown that peptides of the HR regions can inhibit viral infectivity. These studies imply that the HR regions are accessible and that agents which can interact with them may prevent viral entry. In the present study, we have investigated an approach to generate antibodies that specifically recognize the HRN and HRC regions of the SARS-CoV spike (S) glycoprotein in order to evaluate whether these antibodies can inhibit viral infectivity and thus neutralize the SARS-CoV. In this regard, we incorporated HRN and HRC coiled-coil surface residues into a de novo designed two-stranded α-helical coiled-coil template for generating conformation-specific antibodies that recognize α-helices in proteins (Lu, S.M., Hodges, R.S., 2002. J. Biol. Chem. 277, 23515–23524). Eighteen surface residues from two regions of HRN and HRC were incorporated into the template and used to generate four anti-sera, HRN1, HRN2, HRC1, and HRC2. Our results show that all of the elicited anti-sera can specifically recognize HRN or HRC peptides and the native SARS-CoV S protein in an ELISA format. Flow cytometry (FACS) analysis, however, showed only HRC1 and HRC2 anti-sera could bind to native S protein expressed on the cell surface of Chinese hamster ovary cells, i.e., the cell surface structure of the S glycoprotein precluded the ability of the HRN1 or HRN2 anti-sera to see their respective epitope sites. In in vitro viral infectivity assays, no inhibition was observed for either HRN1 or HRN2 anti-serum, whereas both HRC1 and HRC2 anti-sera could inhibit SARS-CoV infection in a dose-dependent manner. Interestingly, the HRC1 anti-serum, which was a more effective inhibitor of viral infectivity compared to HRC2 anti-serum, could only bind the pre-fusogenic state of HRC, i.e., the HRC1 anti-serum did not recognize the six-helix bundle conformation (fusion state) whereas HRC2 anti-serum did. These results suggest that antibodies that are more specific for the pre-fusogenic state of HRC may be better neutralizing antibodies. Overall, these results clearly demonstrate that the two-stranded coiled-coil template acts as an excellent presentation system for eliciting helix-specific antibodies against highly conserved viral antigens and HRC1 and HRC2 peptides may represent potential candidates for use in a peptide vaccine against the SARS-CoV.

The severe acute respiratory syndrome (SARS)

The world was shocked in early 2003 when a pandemic of severe acute respiratory syndrome (SARS) was imminent. The outbreak of this novel disease, caused by a novel coronavirus (the SARS-coronavirus), hit hardest in the Asian Pacific region, though eventually it spread to five continents. The speed of the spread of the SARS epidemic was unprecedented due to the highly efficient intercontinental transportation. An international collaborative effort through the World Health Organization (WHO) has helped to identify the aetiological agent about 1 month after the onset of the epidemic. The power of molecular biology and bioinformatics has enabled the complete decoding of the viral genome within weeks. Over 1000 publications on the phylogeny, epidemiology, genomics, laboratory diagnostics, antiviral, immunization, pathogenesis, clinical disease, and management accumulated within just 1 year. Although the exact animal reservoir of virus and how it evolved into a human pathogen are still obscure, accurate diagnosis and epidemiological control of the disease are now possible. This article reviews what is currently known about the virus and the disease.