Rapid diagnosis of a coronavirus associated with severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is a recently emerged disease associated with pneumonia in infected patients (1). The disease is unusual in its severity, and patients suffering from this disease do not respond to empirical antimicrobial treatment for acute communityacquired typical or atypical pneumonia (2). By the end of March 2003, a cumulative total of 1622 cases and 58 deaths had been reported from 13 countries (3). The disease is highly infectious, and attach rates �56 % have been reported in healthcare workers caring for SARS patients (2). Recently, we identified a novel virus in the family Coronaviridae in SARS patients (4). Of patients from whom paired acute and convalescent sera were available, all had seroconverted or had a greater than fourfold increase in antibody titer to this novel virus (4), suggesting that i

Chemokine up-regulation in SARS-coronavirus–infected, monocyte-derived human dendritic cells

Lymphopenia and increasing viral load in the first 10 days of severe acute respiratory syndrome (SARS) suggested immune evasion by SARS-coronavirus (CoV). In this study, we focused on dendritic cells (DCs) which play important roles in linking the innate and adaptive immunity. SARS-CoV was shown to infect both immature and mature human monocyte-derived DCs by electron microscopy and immunofluorescence. The detection of negative strands of SARS-CoV RNA in DCs suggested viral replication. However, no increase in viral RNA was observed. Using cytopathic assays, no increase in virus titer was detected in infected DCs and cell-culture supernatant, confirming that virus replication was incomplete. No induction of apoptosis or maturation was detected in SARS-CoV–infected DCs. The SARS-CoV–infected DCs showed low expression of antiviral cytokines (interferon α [IFN-α], IFN-β, IFN-γ, and interleukin 12p40 [IL-12p40]), moderate up-regulation of proinflammatory cytokines (tumor necrosis factor α [TNF-α] and IL-6) but significant up-regulation of inflammatory chemokines (macrophage inflammatory protein 1α [MIP-1α], regulated on activation normal T cell expressed and secreted [RANTES]), interferon-inducible protein of 10 kDa [IP-10], and monocyte chemoattractant protein 1 [MCP-1]). The lack of antiviral cytokine response against a background of intense chemokine up-regulation could represent a mechanism of immune evasion by SARS-CoV

Cytokine Responses in Severe Acute Respiratory Syndrome Coronavirus-Infected Macrophages In Vitro: Possible Relevance to Pathogenesis

The pathogenesis of severe acute respiratory syndrome (SARS) remains unclear. Macrophages are key sentinel cells in the respiratory system, and it is therefore relevant to compare the responses of human macrophages to infections with the SARS coronavirus (SARS-CoV) and other respiratory viruses. Primary human monocyte-derived macrophages were infected with SARS-CoV in vitro. Virus replication was monitored by measuring the levels of positive- and negative-strand RNA, by immunofluorescence detection of the SARS-CoV nucleoprotein, and by titration of the infectious virus. The gene expression profiles of macrophages infected with SARS-CoV, human coronavirus 229E, and influenza A (H1N1) virus were compared by using microarrays and real-time quantitative reverse transcriptase PCR. Secreted cytokines were measured with an enzyme-linked immunosorbent assay. SARS-CoV initiated viral gene transcription and protein synthesis in macrophages, but replication was abortive and no infectious virus was produced. In contrast to the case with human coronavirus 229E and influenza A virus, there was little or no induction of beta interferon (IFN-β) in SARS-CoV-infected macrophages. Furthermore, SARS-CoV induced the expression of chemokines such as CXCL10/IFN-γ-inducible protein 10 and CCL2/monocyte chemotactic protein 1. The poor induction of IFN-β, a key component of innate immunity, and the ability of the virus to induce chemokines could explain aspects of the pathogenesis of SARS