Development of a live attenuated vaccine candidate against herpesviral hematopoietic necrosis of goldfish

Effect of temperature on the protective efficacy of a live attenuated vaccine against herpesviral haematopoietic necrosis in goldfish

“…The goldfish fin derived RyuF‐2 cell line was used to propagate the P7‐P8 vaccine strain (Saito et al., 2022), the virulent virus CyHV‐2 SaT‐1 for virus challenge, and the virus particle for enzyme‐linked immunosorbent assay (ELISA). The cells were cultured at 25°C in Medium 199 (M199; Sigma) supplemented with 5% foetal bovine serum (Sigma), 100 U/mL penicillin, and 100 μg/mL streptomycin (Sigma) (Shibata et al., 2015).…”

“…Each group consisted of a non‐infected control ( n = 20), sampling ( n = 27) and vaccination ( n = 20) group. The goldfish in the sampling and vaccination groups were vaccinated using the showering method (1:100 diluted vaccine solution, 3 mL/20 goldfish, held on a net for 10 s; Saito et al., 2024). The infected control group ( n = 20) was maintained at 25°C throughout the experiment.…”

“…The DNA was dissolved in 50 μL TE buffer (10 mM Tris–HCl, 0.1 mM EDTA; pH 7.4) and stored at −80°C. The virus DNA copy number was measured by TaqMan quantitative PCR (qPCR) as described previously (Goodwin et al., 2006; Saito et al., 2022) using the QuantStudio 3 Real‐time PCR system (Applied Biosystems). The reactions using Premix Ex Taq™ Probe qPCR (Takara) were run at 95°C for 30 s, followed by 40 cycles at 95°C for 5 s and 60°C for 20 s, and a final incubation at 50°C.…”

“…Previously, we developed a live attenuated vaccine (P7‐P8 vaccine strain) against HVHN in goldfish (Saito et al., 2022). This vaccine exhibited high protective efficacy against virulent CyHV‐2 challenge and has the potential for practical application in goldfish farms in Japan.…”

“…We conducted additional studies into the showering vaccination method, which is effective against virulent virus strains, various modes of infection, and different goldfish varieties. This method significantly reduced vaccination cost, time, and volume of waste vaccine solution (Saito et al., 2024). All of the vaccination and virus challenge experiments were done at 25°C (Saito et al., 2022, 2024), which is the predominant temperature observed for this disease (Ito & Maeno, 2014); however, the effect of water temperature during the vaccination period on efficacy has not been investigated so far.…”