ABSTRACT
Objective:To develop a new method based on neuraminidase (NA) activity for detec-ting virus titers of cell culture-based influenza vaccines and preliminarily analyze its application.Methods:Reaction conditions including the substrate concentration for enzymatic reaction, stop solution, the number of initially infected target cells and cell lysis buffer were optimized. The titers of cell culture-based influenza vaccine strains were detected by the established method and the results were compared with those by the traditional viral titration test.Results:The optimal substrate concentration for enzymatic reaction was 25 μmol/L, and the optimal stop solution was 0.2 mol/L Na 2CO 3. In the detection of NA activity in infected cells, the maximum relative fluorescence value was obtained by infecting 4×10 4 cells/well with influenza virus for 48 h and using 0.5% TritonX-100 for lysis. The developed method showed no significant differences with the traditional virus titration test in detecting the titers of four batches of influenza vaccine virus strains ( P>0.05), indicating that the two methods had a good consistency. Conclusions:This study established a new method based on NA activity to detect virus titers of cell culture-based influenza vaccines. The method could be used for the detection of virus strains used in the production of cell cultured-based influenza vaccines.
ABSTRACT
Objective To establish a method for rapid preparation of antiserum against influenza virus (H7N9) hemagglutinin,and to study the possibility of using it in single radial immunodiffusion (SRID) assay for quantitative detection of antigen in H7N9 influenza vaccine.Methods Hemagglutinin proteins expressed in eukaryotic cells were used to immunize sheep.Serum samples were collected to detect antibody titers by ELISA and double immunodiffusion assay.Different concentrations of antiserum were used in SRID assay to get the optimized concentration.Results After 4 times of immunization,the antiserum titers achieved 1 ∶ 1 000 000 and 1 ∶ 32 as indicated by ELISA and double immunodiffusion assay,respectively.The antiserum could form a clear precipitation line in SRID assay.The detection of antigen in the range of 10 to 40 μg/ml showed good linearity in the standard curve.The antigen titers in six batches of H7N9 vaccine detected by this SRID assay were identical with those by SDS-PAGE assay.Conclusion The antiserum against H7N9 hemagglutinin for SRID assay was developed successfully,and could be used as a reagent for the quantitative detection of antigen in H7N9 influenza vaccine.
ABSTRACT
Objective To study the possibility of using heterogeneous antiserum in single radial immunodiffusion (SRID) for quantitative detection of HA in H7N9 influenza vaccine product when H7N9-specific antiserum is not available in order to establish a testing method for the detection of H 7N9 antigen in any urgent situation.Methods Antisera specific for H7N1, H7N2, H7N3 and H7N7 were obtained from NIBSC and used for SRID assay .Amino acid sequences of hemagglutinins were comparatively analyzed be-tween H7N9 virus and other viruses used to prepare heterogeneous antiserum .The titers of antisera against H7N9 and their homogenous antigens were detected by double immunodiffusion method .Based on the results of homology analysis and cross-reaction, a suitable antiserum was selected and its applicability was further validated by the SRID assay using H7N9 antigen.Results Influenza A virus subtype H7N3 that used for preparation of 07/278 antiserum showed the highest HA homology with H7N9 (97.14%).The titer of 07/278 antiserum against H7N9 antigen was 1 ∶8 as detected by double immunodiffusion assay .The H7N9 anti-gen and the 07/278 antiserum could form a clear precipitation line in SRID assay .The detection of H7N9 antigen in the range of 10 to 40μg/ml showed a good linearity in the standard curve .Conclusion The 07/278 antiserum from NIBSC can be used as an alternative reagent for the quantitative detection of hemaggluti -nin in H7N9 influenza virus vaccine .