Validation of γ-radiation and ultraviolet as a new inactivators for foot and mouth disease virus in comparison with the traditional methods

Aim: The present work deals with different methods for foot and mouth disease virus (FMDV) inactivation for serotypes O/pan Asia, A/Iran05, and SAT-2/2012 by heat, gamma radiation, and ultraviolet (UV) in comparison with the traditional methods and their effects on the antigenicity of viruses for production of inactivated vaccines. Materials and Methods: FMDV types O/pan Asia, A/Iran05, and SAT-2/2012 were propagated in baby hamster kidney 21 (BHK21) and titrated then divided into five parts; the first part inactivated with heat, the second part inactivated with gamma radiation, the third part inactivated with UV light, the fourth part inactivated with binary ethylamine, and the last part inactivated with combination of binary ethylamine and formaldehyde (BEI+FA). Evaluate the method of inactivation via inoculation in BHK21, inoculation in suckling baby mice and complement fixation test then formulate vaccine using different methods of inactivation then applying the quality control tests to evaluate each formulated vaccine. Results: The effect of heat, gamma radiation, and UV on the ability of replication of FMDV "O/pan Asia, A/Iran05, and SAT-2/2012" was determined through BHK cell line passage. Each of the 9 virus aliquots titer 108 TCID50 (3 for each strain) were exposed to 37, 57, and 77°C for 15, 30, and 45 min. Similarly, another 15 aliquots (5 for each strain) contain 1 mm depth of the exposed samples in petri-dish was exposed to UV light (252.7 nm wavelength: One foot distance) for 15, 30, 45, 60, and 65 min. Different doses of gamma radiation (10, 20, 25, 30, 35, 40, 45, 50, 55, and 60 KGy) were applied in a dose rate 0.551 Gy/s for each strain and repeated 6 times for each dose. FMDV (O/pan Asia, A/Iran05, and SAT-2/2012) were inactivated when exposed to heat ≥57°C for 15 min. The UV inactivation of FMDV (O/pan Asia and SAT-2) was obtained within 60 min and 65 min for type A/Iran05. The ideal dose for inactivation of FMDV (O/pan Asia, A/Iran05, and SAT-2/2012) with gamma radiation were 55-60 and 45 kGy, respectively. Inactivation of FMDV with binary was 20, 24 and 16 hr for O/pan Asia, A/Iran05, and SAT-2/2012, respectively while inactivation by (BEI+FA) was determined after 18, 19 and 11 hr for O/pan-Asia, A/Iran 05, and SAT-2/2012, respectively. The antigenicity of control virus before inactivation was 1/32, it was not changed after inactivation in case of gamma radiation and (BEI+FA) and slightly decrease to 1/16 in case of binary and declined to 1/2, 1/4 in case of heat and UV inactivation, respectively. The immune response induced by inactivated FMD vaccines by gamma radiation and (BEI+FA) lasted to 9 months post-vaccination, while the binary only still up to 8 months post-vaccination but heat and UV-inactivated vaccines were not effective. Conclusion: Gamma radiation could be considered a good new inactivator inducing the same results of inactivated vaccine by binary with formaldehyde (BEI+FA)

Comparative study on the immunopotentiator effect of ISA 201, ISA 61, ISA 50, ISA 206 used in trivalent foot and mouth disease vaccine

Aim: A comparison study was conducted to explore the best internationally available adjuvant that could be used in production of a highly potent foot and mouth disease (FMD) vaccine, that could stimulate a strong immune response and possibly give greater protection against FMD. Materials and Methods: Four experimental batches of trivalent FMD vaccine were prepared with different available oil adjuvants which included Montanide ISA 201, 206, 61 and 50. Results: The results indicated that vaccines emulsified using Montanide ISA 201 and Montanide ISA 206 adjuvants elicited a protective humoral immune response from the 2nd week postvaccination (WPV) as for ISA 201 with serum neutralization test (SNT) and enzyme-linked immune sorbent assay (ELISA) antibody titers of 1.62±0.047a and 1.8±0.049a, 1.59±0.076a and 1.836±0.077a, and 1.71±0.06b and 1.96±0.074b for serotypes O, A, SAT2, respectively, and for ISA 206 at SNT and ELISA antibody titers of 1.5±0.082a and 1.84±0.084a, 1.56±0.037a and 1.818±0.052a, and 1.5±0.106a,b and 1.81±0.104a,b for FMD virus serotypes O, A and SAT2, respectively. For ISA 61 and ISA 50, the protective antibody titer appeared in the 3rd WPV. In the ISA 61 FMD vaccine, SNT and ELISA titer were 1.59±0.076a and 1.9±0.094a, 1.53±0.056a and 1.83±0.070a, and 1.5±0.082a and 1.84±0.094a for serotypes O, A and SAT2, respectively, and in the case of ISA 50 FMD vaccine, the SNT, and ELISA titer were recorded for serotypes O, A and SAT2 respectively, 1.59±0.037a and 1.8±0.030a, 1.68±0.056a,b and 1.916±0.065a,b, and 1.65±0.082a and 1.9±0.09a. On estimating the cellular immune response, the highest delta optical density levels for ISA 201 (0.395-0.460) and ISA 206 (0.375-0.428) were observed on 14 and 21 days post vaccination (DPV) respectively, while the highest levels of lymphoproliferation for ISA 61 (0.375-0.455) and ISA 50 (0.411-0.430) were on 21 and 28 DPV, respectively. Conclusion: The duration of immunity from Montanide ISA oils (201, 206, 61 and 50) FMD vaccines is a long-lived immunity which ranged between 32 and 38 weeks post vaccination but the Montanide ISA 201 FMD vaccine is superior to the others in the rapid cellular immune response of the vaccinated animals which showed its highest level within 14 days post vaccination