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.

Evaluation of inactivation methods for severe acute respiratory syndrome coronavirus in noncellular blood products.

BACKGROUND: Severe acute respiratory syndrome coronavirus (SARS-CoV) has been detected in the blood of infected individuals, which may have the potential to contaminate donated blood and plasma-derived products in the event of a future outbreak. Effective methods for inactivating the SARS-CoV in protein solutions are described in this report. STUDY DESIGN AND METHODS: Heat, ultraviolet (UV) irradiation, octanoic acid, and solvent/detergent (S/D) methods were tested individually for their ability to inactivate SARS-CoV in protein solutions appropriately mimicking blood-derived products. Treated samples were tested for inactivation in a tissue culture growth assay. RESULTS: Viral inactivation by heat treatment at 60 degrees C required 15 to 30 minutes to inactivate the SARS-CoV. UVC efficiently inactivated SARS-CoV in 40 minutes, whereas UVA required the addition of psoralen to enhance inactivation of the virus. The presence of bovine serum albumin limited the ability of UVC and UVA to inactivate SARS-CoV and octanoic acid treatment does not reduce the infectivity of SARS-CoV-spiked protein solutions. S/D treatment required 2, 4, and up to 24 hours for Triton X-100, Tween 80, and sodium cholate inactivation, respectively. CONCLUSION: Heat, UVC irradiation, and S/D treatments effectively inactivate SARS-CoV, whereas octanoic acid treatment is insufficient for inactivation of the virus.

New antiviral pathway that mediates hepatitis C virus replicon interferon sensitivity through ADAR1.

While many clinical hepatitis C virus (HCV) infections are resistant to alpha interferon (IFN-alpha) therapy, subgenomic in vitro self-replicating HCV RNAs (HCV replicons) are characterized by marked IFN-alpha sensitivity. IFN-alpha treatment of replicon-containing cells results in a rapid loss of viral RNA via translation inhibition through double-stranded RNA-activated protein kinase (PKR) and also through a new pathway involving RNA editing by an adenosine deaminase that acts on double-stranded RNA (ADAR1). More than 200 genes are induced by IFN-alpha, and yet only a few are attributed with an antiviral role. We show that inhibition of both PKR and ADAR1 by the addition of adenovirus-associated RNA stimulates replicon expression and reduces the amount of inosine recovered from RNA in replicon cells. Small inhibitory RNA, specific for ADAR1, stimulated the replicon 40-fold, indicating that ADAR1 has a role in limiting replication of the viral RNA. This is the first report of ADAR's involvement in a potent antiviral pathway and its action to specifically eliminate HCV RNA through adenosine to inosine editing. These results may explain successful HCV replicon clearance by IFN-alpha in vitro and may provide a promising new therapeutic strategy for HCV as well as other viral infections.

Inactivation of the coronavirus that induces severe acute respiratory syndrome, SARS-CoV.

Severe acute respiratory syndrome (SARS) is a life-threatening disease caused by a novel coronavirus termed SARS-CoV. Due to the severity of this disease, the World Health Organization (WHO) recommends that manipulation of active viral cultures of SARS-CoV be performed in containment laboratories at biosafety level 3 (BSL3). The virus was inactivated by ultraviolet light (UV) at 254 nm, heat treatment of 65 degrees C or greater, alkaline (pH > 12) or acidic (pH < 3) conditions, formalin and glutaraldehyde treatments. We describe the kinetics of these efficient viral inactivation methods, which will allow research with SARS-CoV containing materials, that are rendered non-infectious, to be conducted at reduced safety levels.

Cytokine and chemokine gene expression after primary and secondary respiratory syncytial virus infection in cotton rats.

The induction of pro- and anti-inflammatory cytokines and chemokines was studied in the lungs of cotton rats after primary or secondary infection with respiratory syncytial virus (RSV). Increases in messenger RNA (mRNA) levels of all genes analyzed were observed during the course of primary infection. In general, mRNA expression peaked between postinfection days 1 and 4 and returned to near-normal levels by day 10. During secondary infection, the expression of some genes (i.e., interferon [IFN]-gamma and interleukin [IL]-10) began earlier, some (i.e., IL-1beta and macrophage inflammatory protein-1beta) began later, and some (i.e., IL-1beta, IL-10, growth-regulated protein, and tumor necrosis factor-alpha) showed prolonged expression, whereas 2 genes (i.e., IFN-alpha and IL-6) were not expressed. This study presents evidence of different kinetics of expression of inflammatory mediators during primary and secondary infection that likely coincide with innate and adaptive immune response and complement previous observations that emphasize the role of inflammation in the pathogenesis of RSV disease.