Co-immunization with recombinant S5196–272 and S6200–317 proteins for enhanced protective antibody response against Tilapia lake virus in Nile tilapia, Oreochromis niloticus (Linnaeus, 1758)

Abstract

Importance of the work: Co-immunization with recombinant S5196–272 and S6200–317 proteins
enhances protective immunity and provides insights for future TiLV vaccine development.
Objectives: To evaluate the vaccine potential of combined S5196–272 and S6200–317 compared to
individual immunization.
Materials and Methods: A sample of Nile tilapia was divided into three main groups: immunized
with S5196–272 and S6200–317 individually, or co-immunized. Antibody responses were measured
weekly using enzyme-linked immunosorbent assay, with virus neutralization being assessed using
a methylthiazolyldiphenyl-tetrazolium bromide (MTT) cell viability assay. A viral challenge test
was conducted to determine the relative percentage of survival (RPS).
Results: Co-immunization of the fish with S5196–272 and S6200–317 resulted in a synergistic effect,
leading to the higher production of S6200–317-specific antibodies than for immunization with S6200–317
alone. A significant increase in serum antibody levels was observed from 7 d, 21 d, 28 d and
35 d post-co-immunization. In contrast, S5196–272-specific antibodies were generated at consistently
high levels following both individual and co-immunization. The MTT cell viability assay findings
demonstrated that antibodies from the co-immunization group had the highest virus-neutralizing
effect (87.22% viability). Furthermore, the viral challenge assay revealed that the co-immunization
group had the highest RPS (57.14%), whereas individual immunization provided no protection
effect against TiLV infection.
Main finding: Co-immunization with S5196–272 and S6200–317 induced a synergistic antibody response
and provided effective protection against TiLV in Nile tilapia.