Severe acute respiratory syndrome coronavirus infection in vaccinated ferrets

BACKGROUND: Development of vaccines to prevent severe acute respiratory syndrome (SARS) is limited by the lack of well-characterized animal models. Previous vaccine reports have noted robust neutralizing antibody and inflammatory responses in ferrets, resulting in enhanced hepatitis. METHODS: We evaluated the humoral immune response and pathological end points in ferrets challenged with the Urbani strain of SARS-associated coronavirus (SARS-CoV) after having received formalin-inactivated whole-virus vaccine or mock vaccine. RESULTS: Humoral responses were observed in ferrets that received an inactivated virus vaccine. Histopathological findings in lungs showed that infection of ferrets produced residual lung lesions not seen in both mock and vaccinated ferrets. SARS-CoV infection demonstrated bronchial and bronchiolar hyperplasia and perivascular cuffing in ferret lung tissue, as seen previously in infected mice. No evidence of enhanced disease was observed in any of the ferrets. All of the ferrets cleared the virus by day 14, 1 week earlier if vaccinated. CONCLUSIONS: The vaccine provided mild immune protection to the ferrets after challenge; however, there was no evidence of enhanced liver or lung disease induced by the inactivated whole-virus vaccine. The ferret may provide another useful model for evaluating SARS vaccine safety and efficacy.     

Potent neutralization of severe acute respiratory syndrome (SARS) coronavirus by a human mAb to S1 protein that blocks receptor association

Effective prophylaxis and antiviral therapies are urgently needed in the event of reemergence of the highly contagious and often fatal severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) infection. We have identified eight recombinant human single-chain variable region fragments (scFvs) against the S1 domain of spike (S) protein of the SARS-CoV from two nonimmune human antibody libraries. One scFv 80R efficiently neutralized SARS-CoV and inhibited syncytia formation between cells expressing the S protein and those expressing the SARS-CoV receptor angiotensin-converting enzyme 2 (ACE2). Mapping of the 80R epitope showed it is located within the N-terminal 261-672 amino acids of S protein and is not glycosylation-dependent. 80R scFv competed with soluble ACE2 for association with the S1 domain and bound S1 with high affinity (equilibrium dissociation constant, Kd=32.3 nM). A human IgG1 form of 80R bound S1 with a 20-fold higher affinity of 1.59 nM comparable to that of ACE2 (Kd=1.70 nM), and neutralized virus 20-fold more efficiently than the 80R scFv. These data suggest that the 80R human monoclonal antibody may be a useful viral entry inhibitor for the emergency prophylaxis and treatment of SARS, and that the ACE2-binding site of S1 could be an attractive target for subunit vaccine and drug development.     

Severe Acute Respiratory Syndrome

Severe acute respiratory syndrome (SARS) is a newly emerged infection that is caused by a previously unrecognized virus - a novel coronavirus designated as SARS-associated coronavirus (SARS-CoV). From November 2002 to July 2003 the cumulative number of worldwide cases was >8000, with a mortality rate of close to 10%. The mortality has been higher in older patients and those with co-morbidities. SARS has been defined using clinical and epidemiological criteria and cases are considered laboratory-confirmed if SARS coronavirus is isolated, if antibody to SARS coronavirus is detected, or a polymerase chain reaction test by appropriate criteria is positive. At the time of writing (24 May 2004), no specific therapy has been recommended. A variety of treatments have been attempted, but there are no controlled data. Most patients have been treated throughout the illness with broad-spectrum antimicrobials, supplemental oxygen, intravenous fluids, and other supportive measures. Transmission of SARS is facilitated by close contact with patients with symptomatic infection. The majority of cases have been reported among healthcare providers and family members of SARS patients. Since SARS-CoV is contagious, measures for prevention center on avoidance of exposure, and infection control strategies for suspected cases and contacts. This includes standard precautions (hand hygiene), contact precautions (gowns, goggles, gloves) and airborne precautions (negative pressure rooms and high efficiency masks). In light of reports of new cases identified during the winter of 2003-4 in China, it seems possible that SARS will be an important cause of pneumonia in the future, and the screening of outpatients at risk for SARS may become part of the pneumonia evaluation.     

Antibody response of patients with severe acute respiratory syndrome (SARS) targets the viral nucleocapsid

The recent outbreak of severe acute respiratory syndrome (SARS) provided an opportunity to study the antibody response of infected individuals to the causative virus, SARS coronavirus. We examined serum samples obtained from 46 patients with SARS, 40 patients with non-SARS pneumonia, and 38 healthy individuals, by use of Western blotting (WB), enzyme-linked immunoassay (ELISA), and immunofluorescence assay, using both native and bacterially produced antigens of the virus. We found a highly restricted, immunoglobulin G-dominated antibody response in patients with SARS, directed most frequently (89% by ELISA) and predominantly at the nucleocapsid. Almost all of the subjects without SARS had no antinucleocapsid antibodies. The spike protein was the next most frequently targeted, but only 63% of the patients (by ELISA) responded. Other targets of the response identified by use of WB included antigens of 80 and 60 kDa. Several nonstructural proteins cloned were not antigenic, and the culture-derived nucleocapsid appeared to be specifically degraded.     

Liver injury during highly pathogenic human coronavirus infections

The severe acute respiratory syndrome coronavirus 2 (SARS‐Cov‐2), the pathogen of 2019 novel coronavirus disease (COVID‐19), has posed a serious threat to global public health. The WHO has declared the outbreak of SARS‐CoV‐2 infection an international public health emergency. Lung lesions have been considered as the major damage caused by SARS‐CoV‐2 infection. However, liver injury has also been reported to occur during the course of the disease in severe cases. Similarly, previous studies have shown that liver damage was common in the patients infected by the other two highly pathogenic coronavirus – severe acute respiratory syndrome coronavirus (SARS‐CoV) and the Middle East respiratory syndrome coronavirus (MERS‐CoV), and associated with the severity of diseases. In this review, the characteristics and mechanism of liver injury caused by SARS‐CoV, MERS‐CoV as well as SARS‐CoV‐2 infection were summarized, which may provide help for further studies on the liver injury of COVID‐19.     

SARS‐CoV‐2 infection in patients with a normal or abnormal liver

Severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2), a novel coronavirus causing coronavirus disease 19 (COVID‐19), with an estimated 22 million people infected worldwide so far although involving primarily the respiratory tract, has a remarkable tropism for the liver and the biliary tract. Patients with SARS‐CoV‐2 infection and no antecedent liver disease may display evidence of cytolytic liver damage, proportional to the severity of COVID‐19 but rarely of clinical significance. The mechanism of hepatocellular injury is unclear and possibly multifactorial. The clinical impact of SARS‐CoV‐2 infection in patients with underlying chronic liver disease, a cohort whose global size is difficult to estimate, has been assessed appropriately only recently and data are still evolving. Patients with cirrhosis are at higher risk of developing severe COVID‐19 and worse liver‐related outcomes as compared to those with non‐cirrhotic liver disease. OLT patients have an intermediate risk. Specific interventions in order to reduce the risk of transmission of infection among this high‐risk population have been outlined by international societies, together with recommendations for modified treatment and follow‐up regimens during the COVID‐19 pandemic. When a vaccine against SARS‐CoV‐2 becomes available, patients with fibrotic liver disease and those with OLT should be considered as prime targets for prophylaxis of COVID‐19, as all other highly susceptible subjects.     

Ferrets as a transmission model for influenza: sequence changes in HA1 of type A (H3N2) virus

Ferrets were used as an animal model to study whether controlled transmission of type A influenza is similar to human transmission when sequence changes in HA1 are used as the outcome. Ferrets were infected initially with A/Sydney/5/97 (H3N2) or A/LA/1/87 (H3N2) intranasally, and transmission chains were established by housing infected ferrets with noninfected ferrets with no influenza antibody titer against the infecting virus. Ferrets infected with A/Sydney were seronegative for A/Sydney and A/LA; ferrets infected with A/LA were seronegative for A/LA but had hemagglutination inhibition titers against A/Sydney. Titers of naturally transmitted influenza were higher than those after direct intranasal infection, but lymphocyte counts from nasal washes diminished with transmission. Ferrets infected with A/LA had 2 amino acid differences in HA1 after transmission through 5 ferret cohorts, but those infected with A/Sydney had none. The results show the value of the ferret model. A/LA resembled the transmission of influenza in humans when under antibody pressure.     

Postexposure immunoprophylaxis of primary isolates by an antibody to HIV receptor complex

mAb B4 is a monoclonal antibody directed against HIV receptor complex. The antibody had broad neutralizing activity against HIV and provided postexposure prophylaxis to hu-peripheral blood leukocyte (PBL)-severe combined immunodeficient mice and chimpanzees. B4 recognized a complex receptor site for HIV on the T cell surface that includes CD4 and also may be influenced by interaction with HIV coreceptors. mAb B4 preferentially neutralized primary HIV-1 isolates compared with T cell line-adapted strains, including syncytium-inducing and non-syncytium-inducing phenotypes, representatives from HIV-1 subtypes A-G, as well as HIV-2, simian immunodeficiency virus, and chimeric simian/human immunodeficiency virus (SHIV). Neutralization was demonstrated in both pre- and postinfection models. The administration of mAb B4 after infectious challenge totally interrupted the infection of hu-PBL-severe combined immunodeficient mice by PBL-grown HIV-1 and the infection of chimpanzees by chimp-adapted HIV-1. This mode of protection suggested that the anti-HIV receptor antibody is efficacious for prophylaxis after exposure to HIV and for prevention of maternal transmission and may be an effective antiretroviral agent for treatment.     

The potential of targeted antibody prophylaxis in SARS outbreak control: a mathematic analysis

BACKGROUND: Severe acute respiratory syndrome (SARS) coronavirus-like viruses continue to circulate in animal reservoirs. If new mutants of SARS coronavirus do initiate another epidemic, administration of prophylactic antibodies to risk groups may supplement the stringent isolation procedures that contained the first SARS outbreak. METHOD: We developed a mathematical model to investigate the effects of hospital admission and targeted antibody prophylaxis on the reproduction number R, defined as the number of secondary cases generated by an index case, during different SARS outbreak scenarios. RESULTS: Assuming a basic reproduction number R(0)=3, admission of patients to hospital within 4.3 days of symptom onset is necessary to achieve outbreak control without the need to further reduce community-based transmission. Control may be enhanced by providing pre-exposure prophylaxis to contacts of hospitalized patients, and through contact tracing and provision of post-exposure prophylaxis. Antibody prophylaxis may also be employed to reduce R below one and thereby restrict outbreak size and duration. CONCLUSIONS: Patient isolation alone can be sufficient to control SARS outbreaks provided that the time from onset to admission is short. Antibody prophylaxis as supplemental measure generally allows for containment of higher R(0) values and restricts both the size and duration of an outbreak.     

Influenza virus aerosol exposure and analytical system for ferrets

Understanding the transmission ability of newly emerging influenza viruses is central to the development of public health preparedness and prevention strategies. Animals are used to model influenza virus infection and transmission, but the routinely used intranasal inoculation of a liquid virus suspension does not reflect natural infection. We report the development of an inoculation method that delivers an influenza virus aerosol inoculum to ferrets and the characterization of size distribution and viable virus present in aerosols shed from infected ferrets during normal breathing and sneezing. By comparing virus deposition, infectivity, virulence, and transmissibility among animals inoculated intranasally or by aerosols with a human (H3N2) or avian (H5N1) influenza virus, we demonstrate that aerosol inoculations more closely resemble a natural, airborne influenza virus infection and that viable virus is measurable in droplets and droplet nuclei exhaled by infected ferrets. These methods will provide improved risk assessment of emerging influenza viruses that pose a threat to public health.     

Prevalence of subclinical infection by the SARS coronavirus among general practitioners in Hong Kong

Eight general practitioners had severe acute respiratory distress syndrome (SARS) in Hong Kong during the epidemic, and others may have been infected by the SARS coronavirus without developing the full syndrome. We conducted a serological and questionnaire survey to determine the prevalence of subclinical infection by SARS coronavirus among general practitioners in Hong Kong. Participants had to be doctors actively practising in family medicine and who did not have SARS. Approximately 3200 general practitioners were invited to participate and the results of 574 were eligible for analysis. 29 samples were tested positive by enzyme-linked immunosorbent assay, but all these samples had titre < 25 by immunoflorescence assay. The prevalence for seropositivity was thus 0% (95% CI, 0.0%-0.6%). This finding documents the lack of subclinical infection by SARS coronavirus in an at-risk group in the community.     

Control of coronavirus infection through plasmacytoid dendritic-cell-derived type I interferon

This study demonstrates a unique and crucial role of plasmacytoid dendritic cells (pDCs) and pDC-derived type I interferons (IFNs) in the pathogenesis of mouse coronavirus infection. pDCs controlled the fast replicating mouse hepatitis virus (MHV) through the immediate production of type I IFNs. Recognition of MHV by pDCs was mediated via TLR7 ensuring a swift IFN-alpha production following encounter with this cytopathic RNA virus. Furthermore, the particular type I IFN response pattern was not restricted to the murine coronavirus, but was also found in infection with the highly cytopathic human severe acute respiratory syndrome (SARS) coronavirus. Taken together, our results suggest that rapid production of type I IFNs by pDCs is essential for the control of potentially lethal coronavirus infections.     

Immunological detection of severe acute respiratory syndrome coronavirus by monoclonal antibodies

In order to establish immunological detection methods for severe acute respiratory syndrome coronavirus (SARS-CoV), we established monoclonal antibodies directed against structural components of the virus. B cell hybridomas were generated from mice that were hyper-immunized with inactivated SARS-CoV virion. By screening 2,880 generated hybridomas, we established three hybridoma clones that secreted antibodies specific for nucleocapsid protein (N) and 27 clones that secreted antibodies specific for spike protein (S). Among these, four S-protein specific antibodies had in vitro neutralization activity against SARS-CoV infection. These monoclonal antibodies enabled the immunological detection of SARS-CoV by immunofluorescence staining, Western blot or immunohistology. Furthermore, a combination of monoclonal antibodies with different specificities allowed the establishment of a highly sensitive antigen-capture sandwich ELISA system. These monoclonal antibodies would be a useful tool for rapid and specific diagnosis of SARS and also for possible antibody-based treatment of the disease.     

Role of tyrosine kinase inhibitor in chronic myeloid leukemia patients with SARS-CoV-2 infection: A narrative Review

Severe acute respiratory syndrome (SARS) caused by a novel coronavirus-2 (CoV-2), also known as COVID-19, has spread rapidly worldwide since it is recognized as a public health emergency and has now been declared a pandemic on March 11, 2020, by the World Health Organization.The genome of SARS-CoV-2 comprises a single-stranded positive-sense RNA approximately 27 to 30 kb in size. The virus is transmitted through droplets from humans to humans. Infection with the SARS virus varies from asymptomatic to lethal, such as fever, cough, sore throat, and headache, but in severe cases, pneumonia and acute respiratory distress syndrome.Recently, no specific and effective treatment has been recommended for patients infected with the SARS virus. However, several options can be investigated to control SARS-CoV-2 infection, including monoclonal antibodies, interferons, therapeutic vaccines, and molecular-based targeted drugs.In the current review, we focus on tyrosine kinase inhibitor management and their protective role in SARS-CoV-2 patients with chronic myelogenous leukemia.     

COVID-19 and the liver: What do we know after six months of the pandemic?

Despite liver injury in patients infected with severe acute respiratory syndrome (SARS) coronavirus (CoV)-2 (SARS-CoV-2) is associated with prolonged hospitalization, and liver dysfunction is mainly described in patients with severe viral disease. How liver abnormalities may affect virus infection is still unknown. Improved understanding of host genetics, lifestyle, underlying comorbidities and adequate follow-up of patients with liver damage are critical in the new scenario of the pandemic virus.     

Modeling Within-Host Dynamics of SARS-CoV-2 Infection: A Case Study in Ferrets

The pre-clinical development of antiviral agents involves experimental trials in animals and ferrets as an animal model for the study of SARS-CoV-2. Here, we used mathematical models and experimental data to characterize the within-host infection dynamics of SARS-CoV-2 in ferrets. We also performed a global sensitivity analysis of model parameters impacting the characteristics of the viral infection. We provide estimates of the viral dynamic parameters in ferrets, such as the infection rate, the virus production rate, the infectious virus proportion, the infected cell death rate, the virus clearance rate, as well as other related characteristics, including the basic reproduction number, pre-peak infectious viral growth rate, post-peak infectious viral decay rate, pre-peak infectious viral doubling time, post-peak infectious virus half-life, and the target cell loss in the respiratory tract. These parameters and indices are not significantly different between animals infected with viral strains isolated from the environment and isolated from human hosts, indicating a potential for transmission from fomites. While the infection period in ferrets is relatively short, the similarity observed between our results and previous results in humans supports that ferrets can be an appropriate animal model for SARS-CoV-2 dynamics-related studies, and our estimates provide helpful information for such studies.     

Intranasal Administration of Maleic Anhydride-Modified Human Serum Albumin for Pre-Exposure Prophylaxis of Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of pediatric viral respiratory tract infections. Neither vaccine nor effective antiviral therapy is available to prevent and treat RSV infection. Palivizumab, a humanized monoclonal antibody, is the only product approved to prevent serious RSV infection, but its high cost is prohibitive in low-income countries. Here, we aimed to identify an effective, safe, and affordable antiviral agent for pre-exposure prophylaxis (PrEP) of RSV infection in children at high risk. We found that maleic anhydride (ML)-modified human serum albumin (HSA), designated ML-HSA, exhibited potent antiviral activity against RSV and that the percentages of the modified lysines and arginies in ML- are correlated with such anti-RSV activity. ML-HSA inhibited RSV entry and replication by interacting with viral G protein and blocking RSV attachment to the target cells, while ML-HAS neither bound to F protein, nor inhibited F protein-mediated membrane fusion. Intranasal administration of ML-HSA before RSV infection resulted in significant decrease of the viral titers in the lungs of mice. ML-HSA shows promise for further development into an effective, safe, affordable, and easy-to-use intranasal regimen for pre-exposure prophylaxis of RSV infection in children at high risk in both low- and high-income countries.     

Respiratory syncytial virus infection: clinical features, management, and prophylaxis

Respiratory syncytial virus (RSV) infects almost all children by two years of age, resulting in a large number of hospital admissions in infants. Reactive airway disease is more common after RSV infection, even in previously healthy children. Management of the acute infection is supportive, but preliminary evidence suggests surfactant administration to ventilated infants may be of benefit. Whether ribavirin or corticosteroids reduce respiratory morbidity after RSV infection remains controversial. Immunoprophylaxis reduces RSV admissions, Palivizumab, a humanized monoclonal antibody, is a more cost-effective prophylaxis than RSV immune globulin. Nevertheless, the cost of prophylaxis, unless only given to very high-risk infants, exceeds savings made in reducing admissions.