Acute Respiratory Syndrome-associated Coronavirus Infection Research Articles

Dynamic innate immune responses of human bronchial epithelial cells to severe acute respiratory syndrome-associated coronavirus infection.

Human lung epithelial cells are likely among the first targets to encounter invading severe acute respiratory syndrome-associated coronavirus (SARS-CoV). Not only can these cells support the growth of SARS-CoV infection, but they are also capable of secreting inflammatory cytokines to initiate and, eventually, aggravate host innate inflammatory responses, causing detrimental immune-mediated pathology within the lungs. Thus, a comprehensive evaluation of the complex epithelial signaling to SARS-CoV is crucial for paving the way to better understand SARS pathogenesis. Based on microarray-based functional genomics, we report here the global gene response of 2B4 cells, a cloned bronchial epithelial cell line derived from Calu-3 cells. Specifically, we found a temporal and spatial activation of nuclear factor (NF)κB, activator protein (AP)-1, and interferon regulatory factor (IRF)-3/7 in infected 2B4 cells at 12-, 24-, and 48-hrs post infection (p.i.), resulting in the activation of many antiviral genes, including interferon (IFN)-β, -λs, inflammatory mediators, and many IFN-stimulated genes (ISGs). We also showed, for the first time, that IFN-β and IFN-λs were capable of exerting previously unrecognized, non-redundant, and complementary abilities to limit SARS-CoV replication, even though their expression could not be detected in infected 2B4 bronchial epithelial cells until 48 hrs p.i. Collectively, our results highlight the mechanics of the sequential events of antiviral signaling pathway/s triggered by SARS-CoV in bronchial epithelial cells and identify novel cellular targets for future studies, aiming at advancing strategies against SARS.

Severe Acute Respiratory Syndrome–Associated Coronavirus Infection in Toronto Children: A Second Look

During the severe acute respiratory syndrome outbreak of 2003, there was an impetus to provide clinical information to the medical community in a timely manner. Accordingly, a preliminary report of our experience of suspected severe acute respiratory syndrome-associated coronavirus infections in children was published without microbiological findings. This report provides an update on pediatric severe acute respiratory syndrome-associated coronavirus infections in Toronto, Ontario, Canada, that includes microbiological findings. All of the children admitted to the Hospital for Sick Children between March 14 and June 15, 2003, with suspect severe acute respiratory syndrome-associated coronavirus infection were included. A proven case was defined as one that fulfilled the clinical criteria for suspect severe acute respiratory syndrome-associated coronavirus infection and demonstrated a serologic response to severe acute respiratory syndrome-associated coronavirus. Serology results, from a neutralizing antibody assay, were considered positive if the sera inhibited the development of a severe acute respiratory syndrome-associated coronavirus-specific cytopathic effect at a dilution of > or =1:8. Neutralizing antibody to severe acute respiratory syndrome-associated coronavirus was demonstrated in 8 of 25 children admitted with suspect severe acute respiratory syndrome-associated coronavirus infection. In 3 of these 8 children, severe acute respiratory syndrome-associated coronavirus was also detected by reverse-transcription polymerase chain reaction in the stool. All 8 had documented exposure to > or =1 severe acute respiratory syndrome-associated coronavirus-infected adults residing in the same household. Exposure that was limited to visiting a Toronto hospital at which severe acute respiratory syndrome-associated coronavirus-infected patients were admitted or travel from a country in which severe acute respiratory syndrome had been reported did not result in documented infection in any of our cases. On the basis of our clinical case definition, 6 of 8 microbiologically confirmed case had been classified as having probable severe acute respiratory syndrome-associated coronavirus infection. Clinical disease was mild, nonspecific, and self-limited and was indistinguishable from that reported with other common respiratory viruses. The factor most strongly associated with severe acute respiratory syndrome-associated coronavirus infection in Toronto children was a history of close contact with an adult severe acute respiratory syndrome-associated coronavirus case. This serves to reinforce the importance of routinely obtaining a thorough epidemiologic travel and exposure history for all subjects with suspected infectious diseases.

Inhibition of Severe Acute Respiratory Syndrome-Associated Coronavirus Infection by Equine Neutralizing Antibody in Golden Syrian Hamsters

Equine anti-severe acute respiratory syndrome-associated coronavirus F(ab')(2) has been verified to protect mice from infection with severe acute respiratory syndrome-associated coronavirus (SARS-CoV). However, before potential clinical application, the antibody needs to be tested in as many animal models as possible to ensure its safety and efficiency. In this study, after verification by various methods that the golden Syrian hamster constitutes a model susceptible to SARS-CoV infection, we confirmed that the antibody could protect animals completely from SARS-CoV infection in the preventive setting. More importantly, the antibody could reduce viral titers or copies by approximately 10(3)- to 10(4)-fold in animal lung after virus exposure, compared with negative control. These data provide further evidence to warrant clinical studies of this antibody in the treatment and prevention of SARS.

Antibody Avidity Maturation during Severe Acute Respiratory Syndrome–Associated Coronavirus Infection

The maturation of virus-specific immunoglobulin G avidity during severe acute respiratory syndrome–associated coronavirus infection was examined. The avidity indices were low (mean ± SD, 30.8% ± 11.6%) among serum samples collected ⩽50 days after fever onset, intermediate (mean ± SD, 52.1% ± 14.1%) among samples collected between days 51 and 90, and high (mean ± SD, 78.1% ± 8.0%) among samples collected after day 90. Avidity indices of 40% and 55% could be considered as cutoff values for determination of recent (⩽50 days) and past (>65 days) infection, respectively. Measurement of antibody avidity can be used to differentiate primary infection from reexposure and to assess humoral responses to candidate vaccines

Low prevalence of subclinical severe acute respiratory syndrome-associated coronavirus infection among hospital healthcare workers in Hong Kong

We recruited 688 hospital healthcare workers who cared for patients with severe acute respiratory syndrome (SARS) and did not develop the disease in the Hong Kong outbreak in 2003. A questionnaire survey was conducted and serum samples were collected for SARS-associated coronavirus (SARS-CoV) antibody. The high-risk procedures performed and the types of unprotected exposures were recorded for analysis. Only 1 asymptomatic nurse had positive serological test. The result demonstrates the low rate of subclinical SARS-CoV infection in hospital healthcare workers and that the infection control practice against SARS in Hong Kong's hospitals during the outbreak was highly effective.

Resolution of primary severe acute respiratory syndrome-associated coronavirus infection requires Stat1.

Intranasal inhalation of the severe acute respiratory syndrome coronavirus (SARS CoV) in the immunocompetent mouse strain 129SvEv resulted in infection of conducting airway epithelial cells followed by rapid clearance of virus from the lungs and the development of self-limited bronchiolitis. Animals resistant to the effects of interferons by virtue of a deficiency in Stat1 demonstrated a markedly different course following intranasal inhalation of SARS CoV, one characterized by replication of virus in lungs and progressively worsening pulmonary disease with inflammation of small airways and alveoli and systemic spread of the virus to livers and spleens.

Neutralizing antibodies in patients with severe acute respiratory syndrome-associated coronavirus infection.

Background. Severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV) is the principal etiologic agent of SARS. We analyzed serum samples obtained from 623 patients with SARS in Beijing, to determine whether infection with SARS-CoV can elicit neutralizing antibodies (NAbs). Methods. We developed a highly sensitive and safe neutralization assay using the SARS-CoV pseudotyped virus and used this assay to determine the titers of the NAbs in serum samples from patients with SARS. Results. We found that 85.9% of serum samples contained NAbs against SARS-CoV and that most of the NAb activities could be attributed to immunoglobulin G. The NAbs became detectable first at 5–10 days after the onset of symptoms, and their levels peaked at 20–30 days and then were sustained for >150 days. The serum samples could neutralize the pseudotype particles bearing the spike glycoproteins from different SARS-CoV strains, suggesting that the NAbs to SARS-CoV were broadly reactive. Conclusions. NAbs to SARS-CoV are broadly elicited in patients with SARS and, according to their kinetics, may correlate with viral load during the early stages of the disease. These results suggest that it is possible to develop effective vaccines against SARS and that NAbs provide a potential strategy for treating patients with SARS.

The spectrum of severe acute respiratory syndrome-associated coronavirus infection.

Whether subclinical or atypical presentations of severe acute respiratory syndrome (SARS) occur and whether clinical judgment is accurate in detecting SARS are unknown. To describe the spectrum of SARS coronavirus infection in a large outbreak and to compare diagnoses based on clinical judgment with the SARS coronavirus test. Secondary analysis of prospectively collected clinical data and archived serum. A SARS screening clinic of a university hospital in the New Territories of Hong Kong. 1221 patients attending the clinic between 12 March 2003 and 12 May 2003. SARS coronavirus serology. 145 of 553 (26%) patients had serologic evidence of SARS coronavirus infection. Of 910 patients who were managed without hospitalization, only 6 had serologic evidence of SARS. Five of the six patients had normal chest radiographs, and four had symptoms such as myalgia, chills, coughing, and feeling feverish. With the SARS coronavirus serologic test as the gold standard, the clinical diagnosis of probable SARS at hospitalization had a sensitivity of 0.96 (95% CI, 0.91 to 0.98) and a specificity of 0.96 (CI, 0.92 to 0.97). Follow-up serologic samples were not obtained from almost half of the patients because they declined further testing. Some people living in the community who were infected but who had minor or no symptoms might not have visited the clinic. There is little evidence of widespread subclinical or mild forms of SARS coronavirus infection. Clinical diagnoses during the outbreak were reasonable and resulted in appropriate triaging.

Severe acute respiratory syndrome-associated coronavirus infection.

Whether severe acute respiratory syndrome–associated coronavirus (SARS-CoV) infection can be asymptomatic is unclear. We examined the seroprevalence of SARS-CoV among 674 healthcare workers from a hospital in which a SARS outbreak had occurred. A total of 353 (52%) experienced mild self-limiting illnesses, and 321 (48%) were asymptomatic throughout the course of these observations. None of these healthcare workers had antibody to SARS CoV, indicating that subclinical or mild infection attributable to SARS CoV in adults is rare.

Enteric involvement of severe acute respiratory syndrome-associated coronavirus infection

Background & Aims : Severe acute respiratory syndrome (SARS) is a recently emerged infection from a novel coronavirus (CoV). Apart from fever and respiratory complications, gastrointestinal symptoms are frequently observed in patients with SARS but the significance remains undetermined. Herein, we describe the clinical, pathologic, and virologic features of the intestinal involvement of this new viral infection. Methods : A retrospective analysis of the gastrointestinal symptoms and other clinical parameters of the first 138 patients with confirmed SARS admitted for a major outbreak in Hong Kong in March 2003 was performed. Intestinal specimens were obtained by colonoscopy or postmortem examination to detect the presence of coronavirus by electron microscopy, virus culture, and reverse-transcription polymerase chain reaction. Results : Among these 138 patients with SARS, 28 (20.3%) presented with watery diarrhea and up to 38.4% of patients had symptoms of diarrhea during the course of illness. Diarrhea was more frequently observed during the first week of illness. The mean number of days with diarrhea was 3.7 ± 2.7, and most diarrhea was self-limiting. Intestinal biopsy specimens obtained by colonoscopy or autopsy showed minimal architectural disruption but the presence of active viral replication within both the small and large intestine. Coronavirus was also isolated by culture from these specimens, and SARS-CoV RNA can be detected in the stool of patients for more than 10 weeks after symptom onset. Conclusions : Diarrhea is a common presenting symptom of SARS. The intestinal tropism of the SARS-CoV has major implications on clinical presentation and viral transmission.

Enteric involvement of severe acute respiratory syndrome-associated coronavirus infection.

Severe acute respiratory syndrome (SARS) is a recently emerged infection from a novel coronavirus (CoV). Apart from fever and respiratory complications, gastrointestinal symptoms are frequently observed in patients with SARS but the significance remains undetermined. Herein, we describe the clinical, pathologic, and virologic features of the intestinal involvement of this new viral infection. A retrospective analysis of the gastrointestinal symptoms and other clinical parameters of the first 138 patients with confirmed SARS admitted for a major outbreak in Hong Kong in March 2003 was performed. Intestinal specimens were obtained by colonoscopy or postmortem examination to detect the presence of coronavirus by electron microscopy, virus culture, and reverse-transcription polymerase chain reaction. Among these 138 patients with SARS, 28 (20.3%) presented with watery diarrhea and up to 38.4% of patients had symptoms of diarrhea during the course of illness. Diarrhea was more frequently observed during the first week of illness. The mean number of days with diarrhea was 3.7 +/- 2.7, and most diarrhea was self-limiting. Intestinal biopsy specimens obtained by colonoscopy or autopsy showed minimal architectural disruption but the presence of active viral replication within both the small and large intestine. Coronavirus was also isolated by culture from these specimens, and SARS-CoV RNA can be detected in the stool of patients for more than 10 weeks after symptom onset. Diarrhea is a common presenting symptom of SARS. The intestinal tropism of the SARS-CoV has major implications on clinical presentation and viral transmission.