Civets Are Equally Susceptible to Experimental Infection by Two Different Severe Acute Respiratory Syndrome Coronavirus Isolates

Abstract

Severe acute respiratory syndrome (SARS) was caused by a novel virus now known as SARS coronavirus (SARS-CoV). The discovery of SARS-CoV-like viruses in masked palm civets (Paguma larvata) raises the possibility that civets play a role in SARS-CoV transmission. To test the susceptibility of civets to experimental infection by different SARS-CoV isolates, 10 civets were inoculated with two human isolates of SARS-CoV, BJ01(with a 29-nucleotide deletion) and GZ01 (without the 29-nucleotide deletion). All inoculated animals displayed clinical symptoms, such as fever, lethargy, and loss of aggressiveness, and the infection was confirmed by virus isolation, detection of viral genomic RNA, and serum-neutralizing antibodies. Our data show that civets were equally susceptible to SARS-CoV isolates GZ01 and BJ01.Severe acute respiratory syndrome (SARS) first appeared in Guangdong, China, in November 2002, and it subsequently spread to many parts of the world, making it the first major infectious disease outbreak of the 21st century (8,13,19). The etiological agent was a newly emerged and previously unrecognized coronavirus, now known as SARS coronavirus (SARSCoV) (2,3,(5)(6)(7)12), which is classified within the order Nidovirales, family Coronaviridae, genus Coronavirus (9,14,15). Epidemiological data obtained from the early stage of the SARS outbreak suggest an animal origin for SARS-CoV, although the reservoir host has yet to be identified (11,(20)(21)(22). The isolation of SARS-CoV-like viruses in masked palm civets and the relationship of their genomic sequences with those of viruses isolated from humans (1, 4) raise the possibility that civets play a role in SARS-CoV transmission to the human population. A striking difference between the vast majority of SARS-CoV genomes from humans and those from civets is the presence in the latter of an additional 29-nucleotide (nt) sequence 246 nt upstream of the start codon of the N gene. Only human SARS-CoV isolated from the earliest stage of the outbreak contains this same 29-nt additional sequence (1). In other words, most human SARS-CoV isolates had a 29-nt deletion in this region of the genome. Thus, while it is clear that SARS-CoV with and without the 29-nt deletion can replicate in humans, the influence of the 29-nt deletion on the capacity of the virus to replicate in civets has not been determined. Here we show that civets are equally susceptible to experimental infection with two different human SARS-CoV isolates, one containing and the other lacking the 29-nt sequence, and that all animals display clinical signs during the early stage of infection.SARS-CoV isolates GZ01 and BJ01 used in this study were originally isolated in Vero E6 cells at the Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences, Beijing, China, and were propagated in Vero E6 cells for two additional passages at our institute in Harbin to generate virus stocks with titers of 10 6 50% tissue culture infective doses (TCID 50 )/ml. BJ01 has the 29-nt deletion found in most hu...

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An immunosuppressed Syrian golden hamster model for SARS-CoV infection

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