Vaccine Research (May 2016)
Immunization of Litopenaeus vannamei shrimp against white spot syndrome virus (WSSV) by gamma-irradiated WSSV plus Vibrio paraheomolyticus
Abstract
Introduction: White spot syndrome virus (WSSV) is one of the most deadly infectious pathogens of the shrimp culture industry. Neither effective vaccines nor efficient treatments are currently available for this disease. Vibrio species are well known dominant bacterial pathogens in the shrimp ponds. As facultative pathogenic bacteria, it is possible that Vibrio spp. along with WSSV to co-infect the shrimp species such as Litopenaeus vannamei. The aim of this study was to investigate the co-administration of gamma-irradiated Vibrio paraheomolyticus as a kind of probiotic and immune-stimulator with gamma-irradiated and inactivated WSSV as an intramuscular vaccine for protection of L. vannamei against WSSV infection. Methods: WSSV was isolated from the infected shrimp samples and multiplied in Astacus leptodactylus crayfish. Titration of WSSV was obtained in post-larvae as 105.4 LD50/ml. The virus was irradiated where D10 value and optimum dose of gamma ray were calculated to be 2.56 and 15 kGy, respectively. The gamma-irradiated WSSV samples, named GI-WSSV were used as a vaccine to immunize L. vannamei shrimps. The freeze-dried V. paraheomolyticus cultures, inactivated by gamma ray (8 kGy) were named GI-V.P and used as a probiotic. Results: Protective dose50 was calculated as 5.61 and 7.94 for the shrimp groups which were vaccinated by GI–WSSV vaccine and GI-WSSV vaccine + GI-V.P, respectively. Calculated RPS values were 73.3%, 86.66% and 26.66% for the GI-WSSV vaccine, GI-WSSV + GI-V.P and isolated probiotic groups, respectively. Significant differences in cumulative mortalities were observed between the vaccination groups and the positive control group (P 0.05). Conclusion: GI-WSSV vaccine can induce immune responses in shrimps infected with WSSV and probiotic GI-V.P enhances these responses.
