Efficacy of heat‐killed and formalin‐killed vaccines against Tilapia tilapinevirus in juvenile Nile tilapia (Oreochromis niloticus)

Abstract

Tilapia tilapinevirus (also known as tilapia lake virus, TiLV) is considered to be a new threat to the global tilapia industry. The objective of this study was to develop simple cell culture-based heat-killed (HKV) and formalin-killed (FKV) vaccines for the prevention of disease caused by TiLV. The fish were immunized with 100 µl of either HKV or FKV by intraperitoneal injection with each vaccine containing 1.8 × 10 6 TCID 50-inactivated virus. A booster vaccination was carried out at 21-day postvaccination (dpv) using the same protocol. The fish were then challenged with a lethal dose of TiLV at 28 dpv. The expression of five immune genes (IgM, IgD, IgT, CD4 and CD8) in the head kidney and spleen of experimental fish was assessed at 14 and 21 dpv and again after the booster vaccination at 28 dpv. TiLV-specific IgM responses were measured by ELISA at the same time points. The results showed that both vaccines conferred significant protection, with relative percentage survival of 71.3% and 79.6% for HKV and FKV, respectively. Significant up-regulation of IgM and IgT was observed in the head kidney of fish vaccinated with HKV at 21 dpv, while IgM, IgD and CD4 expression increased in the head kidney of fish receiving FKV at the same time point. After booster vaccination, IgT and CD8 transcripts were significantlyThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Immunization of Nile tilapia (Oreochromis niloticus) Broodstock With Tilapia Lake Virus (TiLV) Inactivated Vaccines Elicits Protective Antibody and Passive Maternal Antibody Transfer

“…In our previous study, vaccination of tilapia juveniles with HKV and FKV resulted in a significant increase in systemic TiLV-specific IgM and high level of protection against TiLV challenge (RPS = 71.3% to 79.6%) [20]. However, persistence of specific antibody was not evaluated.…”

“…Most recently, water-based inactivated vaccines prepared with heatkilled or formalin-killed TiLV were shown to provide good levels of protection in juvenile tilapia, with RPS of 71.3% and 79.6%, respectively [20]. It has also been reported that TiLV vaccines can induce both humoral immunity and cell mediated immunity [18][19][20].…”

Immunization of Nile Tilapia (Oreochromis niloticus) Broodstock with Tilapia Lake Virus (TiLV) Inactivated Vaccines Elicits Protective Antibody and Passive Maternal Antibody Transfer

“…The TiLV inactivated vaccines were prepared as described previously by Mai et al (2021). Briefly, TiLV strain TH-2018-K, which was isolated from Nile tilapia during a TiLV outbreak in Thailand in 2018 [20], was propagated on E11 cells, in Leibovitz's L15 medium (Sigma, Saint Louis, MO, USA) containing 5% fetal bovine serum, until a cytopathic effect (CPE) of approximately 80% of the cell monolayer was achieved.…”

“…The TiLV inactivated vaccines were prepared as described previously by Mai et al (2021). Briefly, TiLV strain TH-2018-K, which was isolated from Nile tilapia during a TiLV outbreak in Thailand in 2018 [20], was propagated on E11 cells, in Leibovitz's L15 medium (Sigma, Saint Louis, MO, USA) containing 5% fetal bovine serum, until a cytopathic effect (CPE) of approximately 80% of the cell monolayer was achieved. The supernatant containing the virus was collected and clarified to remove cell debris, by centrifuging at 4500× g for 5 min at 4 • C. Virus concentration was determined using 50% tissue culture infectious dose (TCID 50 /mL) [30].…”

“…Most recently, water-based inactivated vaccines prepared with heat-killed or formalin-killed TiLV were shown to provide good levels of protection in juvenile tilapia, with RPS of 71.3% and 79.6%, respectively [20]. It has also been reported that TiLV vaccines can induce both humoral immunity and cell mediated immunity [18][19][20].…”