Studies On The Immune Evaluation Of Inactivated SARS-CoV Experimental Vaccine And The Screening Of Antiviral Drugs In Vitro

Objective: To evaluate the immune response and produce the high-titter anti-SARS sera in rabbit after immunized with inactivated SARS-CoV experimental vaccine, and screen effective antiviral drugs in vitro.Methods: The rabbits were hypodermically immunized three times with F69 of SARS-CoV inactivated vaccine, and sets of rabbit sera were collected before immunization and every week after the first immunization. The specific IgG antibody was assayed by indirect ELISA, the neutralizing antibody was determined by microneutralization test, and the conjugation capacity of different antigenic recombination proteins (S1, S2, S3, S4, N, M, 3CL) of SARS-CoV to the specific antibody was assayed by SARS-CoV protein microassay. The histopathological changes of constitution in rabbits were detected; and the SARS-CoV specific anti-serum was purified according to the method of octanoic acid-ammonium sulfate salting out and DEAE ion exchange chromatography. Some natural compounds were systematically screened for active antiviral drugs by antiviral model in vitro.Results: The serological results showed that, the inactivated SARS-CoV experimental vaccine could fast induce the generation of specific IgG antibody and neutralizing antibody in rabbits, and the antibodies maintained a high level for a long time. Titers of IgG antibody and neutralizing antibody varied regularly, with a peak titer of more than 1:25600 and 1:2560, respectively. However, the levels of antibodies induced by different antigenic proteins of SARS-CoV were different, the best was by S2 protein. The histopathological results showed the interstitial pneumonia in the immunized rabbits which were similar with that of SARS patients, but no other significant changes were found in other tissues. Rabbit anti-serum were purified and identified, the purity of IgG antibody was up to 90 percent, and the activity remained well. With the systematic screening on some natural compounds, Cepharanthine and Grapefruit seed extract (GSE) showed strong inhibiting activity to SARS-CoV, the IC50 of therapeutics was 6.00g/mL and 1:50000, respectively.Conclusion: The achievement of our serological and histopathological experiments are benefit for further studies on the immune evaluation of the inactivated SARS-CoV vaccines in primate animals and on the clinical application; and the data of pharmacodynamic tests is benefit to antiviral drugs development. Undoubtedly, Both of the researches are great helpful for the prevention and control of viral diseases such as SARS.