Systemic and mucosal immune responses in red tilapia (Oreochromis sp.) following immersion vaccination with a chitosan polymer-based nanovaccine against Aeromonas veronii.

A mucoadhesive chitosan polymer-based nanoplatform has been increasingly recognized as an effective mucosal vaccine delivery system for fish. The present study aimed to investigate the effectiveness of immersion vaccination with a chitosan polymer-based nanovaccine to elicit an immune response in serum and mucus of red tilapia and evaluate its protective efficacy after immersion challenge with a heterogenous strain of Aeromonas veronii UDRT09. Six hundred red tilapia (22 ± 1.8 g) were randomly allocated into four experimental groups: control, empty-polymeric nanoparticle (PC), formalin-killed vaccine (FKV), and chitosan polymer-based nanovaccine (CS-NV) in triplicate. The specific IgM antibody levels and their bactericidal activity were assessed in serum and mucus for 28 days after immersion vaccination and followed by immersion challenge with A. veronii. The immersion vaccine was found to be safe for red tilapia, with no mortalities occurring during the vaccination procedure. The specific IgM antibody levels and bactericidal activity against A. veronii in both serum and mucus were significantly higher in red tilapia vaccinated with CS-NV compared to the FKV and control groups at all time points. Furthermore, the serum lysozyme activity, ACH50, and total Ig levels demonstrated a significant elevation in the groups vaccinated with CS-NV compared to the FKV and control groups. Importantly, the Relative Percentage Survival (RPS) value of the CS-NV group (71 %) was significantly higher than that of the FKV (15.12 %) and PC (2.33 %) groups, respectively. This indicates that the chitosan polymer-based nanovaccine platform is an effective delivery system for the immersion vaccination of tilapia.

Development of a bivalent mucoadhesive nanovaccine to prevent francisellosis and columnaris diseases in Nile tilapia (Oreochromis niloticus).

The occurrence of francisellosis caused by Francisella orientalis sp. nov. (Fo) and columnaris disease caused by Flavobacterium oreochromis (For) is negatively impacting Nile tilapia (Oreochromis niloticus) production, especially when high stocking densities are used. A new and innovative bivalent mucoadhesive nanovaccine was developed in this study for immersion vaccination of tilapia against francisellosis and columnaris disease. It was shown to have the potential to improve both innate and adaptive immunity in vaccinated Nile tilapia. It increased innate immune parameters, such as lysozyme activity, bactericidal activity, phagocytosis, phagocytic index, and total serum IgM antibody levels. Additionally, the vaccine was effective in elevating specific adaptive immune responses, including IgM antibody levels against Fo and For vaccine antigens and upregulating immune-related genes IgM, IgT, CD4+, MHCIIα, and TCRß in the head kidney, spleen, peripheral blood leukocytes, and gills of vaccinated fish. Furthermore, fish vaccinated with the mucoadhesive nanovaccine showed higher survival rates and relative percent survival after being challenged with either single or combined infections of Fo and For. This vaccine is anticipated to be beneficial for large-scale immersion vaccination of tilapia and may be a strategy for shortening vaccination times and increasing immune protection against francisellosis and columnaris diseases in tilapia aquaculture.

Chitosan-polymer based nanovaccine as promising immersion vaccine against Aeromonas veronii challenge in red tilapia (Oreochromis sp.).

Red tilapia (Oreochromis sp.), one of the important freshwater fish species in fish farming in Thailand, has for long been suffering from a serious bacterial disease named epizootic ulcerative syndrome and hemorrhagic septicemia. The disease is mainly caused by Aeromonas veronii. Vaccine is proposed to be a major impact tool for sustainable control and prevention strategies. Vaccination by immersion has many benefits over injection. However, the conventional immersion method suffers from a low potency due to the inefficient uptake of antigens across mucosal tissue. Here, we developed a chitosan-polymer based nanovaccine together with an efficient delivery vehicle to enhance the immunogenicity of immersion vaccination, increasing bioavailability and inducing local immune responses during transit to mucosal inductive immune sites. The physiochemical properties of nanovaccine, which was modified on surface particle by using a mucoadhesive polymer, were assessed for size, zeta potential, and particle distribution. Our study demonstrated by SEM image and microscopic fluorescence image that nanovaccine greatly increased the binding and penetrating ability into gills when compared with formalin killed vaccine. The nano-sized particles were well dispersed in water and trapped in core nanoparticle as confirmed by TEM image. The efficacy of vaccine was performed by immersion challenge with virulent A.veronii after 30 days post vaccination in tilapia. The result revealed a high level of mortality in the control, empty-polymeric nanovaccine and formalin killed bacterin vaccine groups. A high relative percentage survival (RPS) of vaccinated fish was noted with chitosan-polymer based nanovaccine. Our studies indicated that this chitosan-polymer based nanovaccine derived from cell fragments and supernatant was the improved version of the conventional formalin killed vaccine. The chitosan polymer based particle could increase the efficacy of nanovaccine toward the target mucosal membrane and enhance protection against A. veronii infection in red tilapia.

The spread of Vibrio parahaemolyticus in tissues of the Pacific white shrimp Litopenaeus vannamei analyzed by PCR and histopathology.

V. parahaemolyticus are bacteria that cause the Acute Hepatopancreatic Necrosis Disease (AHPND), or Early Mortality Syndrome (EMS), in shrimp. To further understand the pathogenesis mechanisms of V. parahaemolyticus infection in shrimp, the spreading of this bacterium in various tissues was investigated. The spread of infection in shrimp that were exposed to seawater bacteria was studied by PCR and histopathology at 1 min, 1, 6, 12, 24, 48 and 72 h after exposure. The PCR results showed that V. parahaemolyticus was at its most widespread at 6 h after exposure, at which point V. parahaemolyticus was found in the gills, hepatopancreas, intestine, muscles, and hemolymph. However, examinations after 6 h of infection found only small amounts of V. parahaemolyticus in hepatopancreas and intestines. Histopathology of the hepatopancreas showed abnormalities on gross examination at 1 min-72 h after exposure. This study indicates that V. parahaemolyticus can spread quickly by using the hepatopancreas as the target tissue. After 6 h of infection, V. parahaemolyticus was eliminated by immune system while their toxins still caused damage to shrimp tissues.

Addressing Nanovaccine Strategies for Tilapia.

Tilapia is the world's most extensively farmed species after carp. It is an attractive species for aquaculture as it grows quickly, reaching harvest size within six to seven months of production, and provides an important source of food and revenue for many low-income families, especially in low- to middle-income countries. The expansion of tilapia aquaculture has resulted in an intensification of farming systems, and this has been associated with increased disease outbreaks caused by various pathogens, mostly bacterial and viral agents. Vaccination is routinely used to control disease in higher-value finfish species, such as Atlantic salmon. At the same time, many tilapia farmers are often unwilling to vaccinate their fish by injection once the fish have been moved to their grow-out site. Alternative vaccination strategies are needed to help tilapia farmers accept and use vaccines. There is increasing interest in nanoparticle-based vaccines as alternative methods for delivering vaccines to fish, especially for oral and immersion administration. They can potentially improve vaccine efficacy through the controlled release of antigens, protecting antigens from premature proteolytic degradation in the gastric tract, and facilitating antigen uptake and processing by antigen-presenting cells. They can also allow targeted delivery of the vaccine at mucosal sites. This review provides a brief overview of the bacterial and viral diseases affecting tilapia aquaculture and vaccine strategies for farmed tilapia. It focuses on the use of nanovaccines to improve the acceptance and uptake of vaccines by tilapia farmers.

Effects of Mangosteen (Garcinia mangostana) Peel Extract Loaded in Nanoemulsion on Growth Performance, Immune Response, and Disease Resistance of Nile Tilapia (Oreochromis niloticus) against Aeromonas veronii Infection.

Nanotechnology can enhance nutrient delivery and bioavailability; hence, it has recently been considered the most practical alternative technology for nutritional supplements and disease control in fish farming. The present study was designed to evaluate the effects of mangosteen peel extract loaded in nanoemulsion (MSNE) on the inhibition of A. veronii (in vitro) and in vivo growth performance, serum biochemical parameters, the immune response, and the disease resistance of Nile tilapia (Oreochromis niloticus) against A. veronii challenge. The particle size, polydispersity index, and particle surface charge of MSNE were 151.9 ± 1.4 nm, >0.3, and -30 mV, respectively. Furthermore, MSNE, mangosteen peel extract (MPE), and nanoemulsion (NE) improved the antimicrobial activity against A. veronii. Fish fed MSNE, MPE, and NE-supplemented diets had a significantly lower (p < 0.05) feed conversion ratio (FCR) and higher specific growth rate (SGR) than fish fed the control diet. Furthermore, the MSNE had significantly higher serum glucose and protein levels than the control group in Nile tilapia. Total immunoglobulin, serum lysozyme, alternative complement activity, and survival of Nile tilapia fed with MSNE were significantly higher (p < 0.05) than the control diet. Therefore, MSNE has the potential to be employed as a supplement in sustainable Nile tilapia farming.