Adoptive transfer of sensitized leukocytes confers partial protection against herpesviral hematopoietic necrosis (HVHN) in ginbuna crucian carp Carassius auratus langsdorfii immunized with a live attenuated vaccine

Hiroaki, Saito and Lau, Lik Ming and Minami, Shungo and Manami, Yuguchi and Aiko, Shitara and Hidehiro, Kondo and Goshi, Kato and Motohiko, Sano (2023) Adoptive transfer of sensitized leukocytes confers partial protection against herpesviral hematopoietic necrosis (HVHN) in ginbuna crucian carp Carassius auratus langsdorfii immunized with a live attenuated vaccine. Developmental & Comparative Immunology, 148. p. 105001. ISSN 1879-0089

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Abstract

A live attenuated vaccine was developed against HVHN of goldfish, caused by cyprinid herpesvirus-2 (CyHV-2). However, the mechanism of immunity acquired after vaccination remains unknown. The objectives of this study are to identify susceptible hosts’ immune responses and investigate the role of adoptive transferred sensitized leukocytes in protection against HVHN using the susceptible isogenic ginbuna. Goldfish and ginbuna (Wakin and S3n strain, respectively; BW 8 g) were vaccinated by the showering vaccination method (1:100 diluted vaccine; holding fish on the net for 10 s). Vaccinated fish were challenged with a virulent CyHV-2 by immersion after 21 days and the mortality was recorded. Meanwhile, the trunk-kidney and spleen leukocytes were isolated to determine CD8a+ lymphocyte dynamics. Antibody titer in serum was determined by ELISA using purified virus particles. In the adoptive transfer experiment, pooled whole trunk-kidney and spleen leukocytes of the vaccinated donor ginbuna (n=14) after 55 days were intraperitoneally injected (3.5 x 10^6 cells/fish) into naïve recipient ginbuna (n=10). The serum of donor ginbuna was collected for ELISA. After one day, the donor and recipient ginbuna were challenged with a virulent CyHV-2. The vaccine was effective in both fish species against CyHV-2 challenge considering the increase of CD8a+ lymphocytes and ELISA antibody titer. The adoptive transfer experiment showed survival rate of donor, recipient and infected-control ginbuna at 80%, 40%, and 0%, respectively. Donor ginbuna had low seropositivity before CyHV-2 challenge. These results suggest that humoral and cell-mediated immunity play significant roles in the protective immunity induced by the vaccine.

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