SARS-Coronavirus (SARS-CoV) is a new respiratory virus, which causes the severe acute respiratory syndrome (SARS) in humans. During the first SARS epidemic that started in November 2002 in Guangdong, China, the virus was rapidly spread and infected more than 8000 people worldwide; about 800 patients died, i.e. an overall fatality rate of 9.6% was observed. Due to the absence of effective drugs or a vaccine, control of the disease relies on rapid detection of cases and isolation of patients. As the virus still remains in animal reservoirs and may reemerge there is still an urgent need for rapid development of a safe and effective vaccine.
The virus was first identified in March 2003 following isolation in Vero cells, i.e. the cell line that is employed for Baxter´s serum and protein-free cell culture technology. Based on this, the National Institute of Health (USA) and Baxter signed a contract for the development of an inactivated, whole virus SARS-CoV candidate vaccine and delivery of vaccine for phase I/II clinical studies.
A clinical isolate of SARS-CoV provided by the Centers of Disease Control (USA) has been biologically cloned by plaque purification and used as seed virus for the production of high titer SARS-CoV employing our serum and protein-free Vero cell technology. A highly purified, double-inactivated whole virus vaccine preparation was developed using a process similar to that for the Vero cell derived influenza vaccine. Preclinical studies demonstrate that the candidate vaccine is well-tolerated and highly immunogenic. Mice, guinea pigs and rats that have been immunized with this candidate vaccine preparation developed very high antibody titers against the SARS-CoV S-protein (this protein mediates attachment to the host cell receptor). More important, high titers of neutralizing antibodies that protected mice against intranasal challenge with live SARS-CoV were induced. A clear correlation between antibody titer, neutralization activity and protection could be demonstrated.
After completion of preclinical studies, the NIH will conduct phase I/II clinical studies in humans for evaluation of safety and immunogenicity of our SARS-CoV candidate vaccine.
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