Efficacy of Different Routes of Formalin-Killed Vaccine Administration on Immunity and Disease Resistance of Nile Tilapia (Oreochromis niloticus) Challenged with Streptococcus agalactiae

Abstract

Vaccines prepared from formalin-killed Streptococcus agalactiae were administered to Nile tilapia (Oreochromis niloticus) via three different routes: immersion in a water-based vaccine, injection with an oil-based vaccine, and as a water-based oral vaccine. All vaccination treatments increased lysozyme and peroxidase activity in skin mucus of Nile tilapia by 1.2- to 1.5-fold compared to their activities in unvaccinated control fish. Likewise, alternative complement, phagocytosis, and respiratory burst activities in the blood serum of the vaccinated fish were 1.2- to 1.5-times higher than in the unvaccinated fish. In addition, the expression transcripts of interleukin-1 (IL-1), interleukin-8 (IL-8), and lipopolysaccharide-binding protein (LBP) were 2.3- to 2.9-fold higher in the vaccinated fish compared to those in the unvaccinated control. The unvaccinated fish challenged with Streptococcus agalactiae had a survival rate of 25% compared to a survival rate of 78–85% for the vaccinated fish. The differences between the unvaccinated and vaccinated fish were all statistically significant, but there was no significant difference in any of the indicators of immunity between the three vaccinated groups. Collectively, these results confirm that vaccination with formalin-killed Streptococcus agalactiae significantly improved the resistance of Nile tilapia to infection by the pathogen. Overall, the efficacy of oral administration of the vaccine was comparable to that of vaccine administered via injection, indicating that oral vaccination is a viable cost-effective alternative to administering vaccines by injection.

Evaluation of Flathead Grey Mullets (Mugil cephalus) Immunization and Long-Term Protection against Vibrio harveyi Infection Using Three Different Vaccine Preparations

“…These results correlate to the levels of antibody production in each of the vaccinated groups, where the fish immunized with the heat-killed bacteria emulsified in adjuvant presented significantly higher levels of antibodies throughout the 14 months of the experiment, compared to the fish immunized with the heat-killed bacteria + PBS. Many studies have been conducted toward the improvement of vaccine performance such as capturing the antigens in liposomes, or the addition of adjuvants to lead to better immunomodulation and increase protection [16,[41][42][43]. Adjuvants are essential elements that increase the efficacy of vaccination practices through many different actions such as stimulators of immune responses [30,44].…”

First Investigation of the Optimal Timing of Vaccination of Nile Tilapia (Oreochromis niloticus) Larvae against Streptococcus agalactiae

“…Various studies have reported the development of effective vaccines against S. agalactiae infection in Nile tilapia [ 13 , 30 , 31 , 32 , 33 ]. The results obtained for most developed vaccines showed that they were very effective in the laboratory [ 34 , 35 , 36 ] and on the field-trial scale [ 37 , 38 , 39 ], but most of those studies relied on injection methods [ 40 , 41 , 42 ]. This vaccination route was subsequently found to be impractical and unacceptable for field application in many fish species.…”

Immunopathological and Comparative Study of Concanavalin- A and Streptococcus lyophilized Antigen in Immunized Rats

“…The S.pyogenes antigen was prepared according to (Nguyen et al, 2022), then lyophilized and measured the protein concentration by Biuret method (Randox Lab). It was kept under 4 o C in a refrigerator until use as antigen in experimental rats, when used re-suspended by adding 2 ml of Phosphate buffer saline PBS to 2 gm of dry lyophilized antigen to make stock solution according to (Rafeek et al, 2021).…”