In-Vitro Inactivation of Sabin-Polioviruses for Development of Safe and Effective Polio Vaccine

Figures

• 

  Figure 1. Inactivation kinetics of the three PV serotypes using different inactivating agents. Viral infectivity titers of the aliquots were determined by titration using Hep-2c cells in tissue culture microtiter plates. Each point is the average of two independent tests to measure the virus titer after a specific exposure time to the inactivating agent tested using tissue culture technique and expressed as log10CCID50/mL and the error bars show the standard deviation (SD). The curves are fitted using non linear regression of the data. PV1 is represented as squares, PV2 as circles and PV3 as triangles. The method limit of detection (0.5 log CCID50/mL) is indicated by horizontal dashed line also symbols below LOD indicate no detected CPE at those time points. (a–c) Effect of HCHO on the infectivity titers of PV 1, 2 and 3 respectively; (d–f) Effect of H2O2 on the infectivity titers of PV 1, 2 and 3 respectively; (g–i) Effect of ascorbic acid on the infectivity titers of PV 1, 2 and 3 respectively and (j–l) Effect of EGCG on the infectivity titers of PV 1, 2 and 3 respectively.

• 

  Figure 2. Retention of D-antigens of the three PV serotypes following inactivation by different inactivating agents determined using ELISA. Each column represents the mean absorbance values obtained from the different inactivated vaccine preparations when tested at the end of inactivation period. Two untreated control groups of polioviruses one kept at 35 °C (UT35) and the other at 2–8 °C (UT2-8) were tested as well. The error bars represent the standard deviation (SD). The capped lines represent the compared groups and the numbers written above the capped lines are the p-values. (a) PV1 results, (b) PV2 results and (c) PV3 results.

• 

  Figure 3. Immune response to the inactivated trivalent bulks in rats’ sera IgG antibodies were determined by ELISA. Serial two fold dilutions of sera obtained from rats immunized with one of the four vaccine preparations (HCHO, H2O2, AA or EGCG) and the sera of unimmunized control group (NC). Data is the mean absorbance of duplicate wells and error bars show the standard deviation (SD). Cut-off value is mean absorbance of diluent control +2 SD and is represented by a horizontal dashed line. The capped lines represent the compared groups and the numbers written above the capped lines are the p-values. (a) PV1 results, (b) PV2 results and (c) PV3 results.

• 

  Figure 4. Sabin viruses neutralizing antibodies against PV serotypes. Titers of neutralizing antibodies obtained from each group of rat sera after immunization with one of the four vaccine preparations were tested via tissue culture technique. Titers are expressed as reciprocals. The test was performed in triplicate for each serotype and the geometric mean titers (GMT) are represented by horizontal lines. The capped lines represent the compared groups and the numbers written above the capped lines are the p-values. (a) PV1, (b) PV2 and (c) PV3.