Immune Responses and Protective Efficacy of a Formalin-Killed Francisella Noatunensis Subsp. Orientalis Vaccine Evaluated through Intraperitoneal and Immersion Challenge Methods in Oreochromis Niloticus

Abstract

Francisella noatunensis subsp. orientalis (Fno), an intracellular bacterium, causes systemic granulomatous diseases, resulting in high mortality and huge economic losses in Taiwanese tilapia farming. In this study, we tested the efficacy of a formalin-killed Fno vaccine in cultured tilapia. Fno was isolated from diseased tilapia, inactivated with formalin, and mixed with the mineral oil base adjuvant (MontanideTM ISA 763 AVG). A total of 300 tilapia were divided into two groups. The experimental group was intraperitoneally injected with 0.1 mL of vaccine, which was substituted with phosphate-buffered saline (PBS) in the control group. A booster was administered at 2 weeks post-immunization. Tilapia were challenged at 6 weeks post primary immunization by intraperitoneal (IP) injection and immersion methods. Mortality was recorded at 21 and 60 days. The results revealed that the vaccine induced a greater antibody titer and led to 71% and 76% of relative percent survival (RPS) after the IP and immersion challenge. The transcripts of proinflammatory cytokines and immune-related genes, including interleukin-1β (IL-1β), tumor necrosis factor alpha (TNFα), C-X-C motif chemokine ligand 8 (CXCL8), and interleukin-17C (IL-17C), were significantly upregulated after vaccination. Additionally, vaccinated fish had lower bacterial loads in the blood and lower granuloma intensities in the kidney, spleen, liver, and gill than control fish. The results in this study demonstrate that the inactivated Fno vaccine could be an essential resource in Taiwanese tilapia farming.

Dietary supplementation of fish protein hydrolysate in high plant protein diets modulates growth, liver and kidney health, and immunity of barramundi ( Lates calcarifer )

“…The fish challenged with the IP injection showed a higher mortality over those exposed to the immersion challenge as the direct injection bypasses the first line of defence, including mucus and skin, with direct access to the organs of predilection. However, in the immersion challenge, bacteria need to penetrate the mucosal surfaces and skin before entering the system (Pulpipat et al, 2020). Therefore, the immersion challenge is less effective than the intraperitoneal challenge in terms of the manifestation of disease and mortality.…”

Optimization of immunization procedure for SWCNTs‐based subunit vaccine with mannose modification against spring viraemia of carp virus in common carp

“…Furthermore, previous study has proved that the targeted nanovaccine delivery system constructed by modifying the SVCV antigen G protein with mannose, and then, conjugating SWCNTs can effectively improve immune protection effect after immersion immunization in common carp (Zhang et al, 2020). A number of factors should be consideration, for instance, vaccine dose, immunization time, fish size or age, adjuvant and immunization density (Bøgwald & Dalmo, 2019;Pulpipat et al, 2020). However, there have been few reports on the optimization of the programme of immersion immunity.…”

State-of-the-Art Vaccine Research for Aquaculture Use: The Case of Three Economically Relevant Fish Species

“…The vaccine formulated by Pulpipat et al [ 44 ] shares the methodological features of the previous two, namely, inactivation method and adjuvant; what differed was the strain (AOD104086, IP-delivered at a concentration of 10 8 CFU/fish) and the challenge routes (IP and immersion). This bacterin proved efficacious in (i) stimulating a specific IgM response, which at 2 and 6 WPV was higher in treated than control fish, and the expression of genes related to innate immunity in both spleen and kidney; (ii) protecting fish in two comparative challenge experiments that induced a similar mortality time-course; and (iii) lowering the blood bacterial concentration as well as spleen and kidney granuloma formation, regardless of the challenge route.…”