Enhanced bath immersion vaccination through microbubble treatment in the cyprinid loach

The protective effect of inactivated Flavobacterium columnare vaccine in grass carp (Ctenopharyngodon idellus)

Flavobacterium columnare, which causes columnaris disease, is responsible for significant mortality in grass carp. Vaccination is a safe and effective measure to combat this disease, and this study aimed to investigate the immune protective effects of different treatments using an inactivated F. columnare vaccine. The vaccine was prepared by inactivating the bacteria with 0.05% formaldehyde at 4°C for 24 hours. The experiments involving grass carp were divided into two parts. In Experiment 1, the immune effects of two isolates, JX-01 (genomovar I) and MU-04 (genomovar II), were compared, along with the impact of white oil adjuvant and the number of immunizations. The results showed that when the white oil adjuvant was used as a booster, the relative percent survival (RPS) of the JW2 group and MW2 group after 8 weeks of the first immunization was 34% and 61%, respectively. In Experiment 2, only the MU-04 (genomovar II) isolate was used as an antigen, with the white oil adjuvant as a booster. The effects of different doses (CFU=10⁸, 10⁷, and 10⁶ bacteria/mL) on immune responses were compared, and the RPS values in the MW6, MW7, and MW8 groups after 4 weeks of the first immunization were found to be 38%, 57%, and 71%, respectively. Furthermore, in the cross-antigen protection experiment, the MW2 group exhibited an RPS of 55% against the JX-01 isolate, which was significantly higher than the control group (33%). These findings suggest that an inactivated vaccine comprising an appropriate antigen isolate when administered with a white oil adjuvant as a booster, can provide effective protection in grass carp.

Microbubbles in Food Technology

Microbubbles are largely unused in the food industry yet have promising capabilities as environmentally friendly cleaning and supporting agents within products and production lines due to their unique physical behaviors. Their small diameters increase their dispersion throughout liquid materials, promote reactivity because of their high specific surface area, enhance dissolution of gases into the surrounding liquid phase, and promote the generation of reactive chemical species. This article reviews techniques to generate microbubbles, their modes of action to enhance cleaning and disinfection, their contributions to functional and mechanical properties of food materials, and their use in supporting the growth of living organisms in hydroponics or bioreactors. The utility and diverse applications of microbubbles, combined with their low intrinsic ingredient cost, strongly encourage their increased adoption within the food industry in coming years.

Chitosan and anisodamine enhance the immersion immune efficacy of inactivated Elizabethkingia miricola vaccine in black spotted frogs

Black spotted frogs have rich nutrition and delicious meat, and its market consumption has increased year by year. However, outbreaks of the diseases have caused huge losses to the breeding industry. The crooked head disease caused by Elizabethkingia miricola (E. miricola) is highly contagious and lethal, and there is no effective treatment method. Vaccination is the most promising strategy to prevent infectious diseases. Immersion vaccination has attracted many researchers because of its simplicity of operation in preventing infectious diseases. In addition, immersion vaccines can be more effective when used with adjuvants. In this study, we prepared inactivated E. miricola with 0.3% formaldehyde, and the black spotted frogs were vaccinated by soaking in inactivated E. miricola vaccine, anisodamine + vaccine mixture, β-glucan + vaccine mixture, chitosan + vaccine mixture for 60 min. PBS was used as a control. After being challenged by E. miricola, the survival rate of anisodamine + vaccine (57%) and chitosan + vaccine group (63%) was significantly higher than that of the control group (17%). By analyzing pathological sections, we found that the chitosan + vaccine and anisodamine + vaccine groups protected the brain, eye, liver and kidney tissues of the black spotted frogs compared to the control group, which was consistent with the trend of survival rate. In addition, chitosan + vaccine and anisodamine + vaccine groups had better effects on LZM, TSOD and C3 in serum than control group. Meanwhile, the numbers of the percentage of leukocytes/haemocytes in the peripheral blood of immunized black spotted frogs increased. The anisodamine + vaccine group (5.3%) and chitosan + vaccine (5.38%) group were significantly higher than the blank control group (2.24%), which indicate that the two groups induced a more significant immune response and were more resistant to bacterial invasion. The tissue bacterial loads in liver, brain, kidney and eye were significantly lower in the anisodamine + vaccine and chitosan + vaccine groups than that of the control group. This study explored and demonstrated the good efficiency of chitosan and anisodamine as adjuvants for immunization by immersion and provided a reference for improving the efficiency of immunization by immersion.

A meta-analysis of impacts of immune response and infection on oxidative status in vertebrates

Inferring from patterns observed in biomedical research, ecoimmunological theory predicts that oxidative stress is a ubiquitous physiological cost that contributes to generating variation in immune function between individuals or species. This prediction is, however, often challenged by empirical studies testing the relationship between immune response or infection and oxidative status markers. This points out the importance of combining ecological immunology and oxidative stress ecology to further our understanding of the proximate causes and fitness consequences of individual variation in health, and adaptability to natural and anthropogenic environmental changes. I reviewed evidence and performed phylogenetic meta-analyses of changes in oxidative status markers owing to either injection of an antigen or infection in captive and free-living vertebrates (141 studies, 1262 effect sizes, 97 species). The dataset was dominated by studies on fish, birds and mammals, which provided 95.8% of effect sizes. Both antigen injection and parasite exposure were associated with changes of oxidative status. There were significant effects of taxonomic class and experimental environment (captivity vs. wild). In contrast with my predictions, age category (young vs. adult), study design (correlational vs. experimental) and proxies of pace of life (clutch size, litter size, and body mass; for birds and mammals only) were negligible in this dataset. Several methodological aspects (type of immunostimulant, laboratory assay, tissue analysed) showed significant effects on both strength and direction of effect. My results suggest that alterations of oxidative status are a widespread consequence of immune function across vertebrates. However, this work also identified heterogeneity in strength and direction of effect sizes, which suggests that immune function does not necessarily result in oxidative stress. Finally, this work identifies methodological caveats that might be relevant for the interpretation and comparability of results and for the application in conservation programs.

Pre-treatment of Nile tilapia (Oreochromis niloticus) with ozone nanobubbles improve efficacy of heat-killed Streptococcus agalactiae immersion vaccine

Nanobubble technology has shown appealing technical benefits and potential applications in aquaculture. We recently found that treatment with ozone nanobubbles (NB-O₃) activated expression of several immune-related genes leading to effective response to subsequent exposure to fish pathogens. In this study, we investigated whether pre-treatment of Nile tilapia (Oreochromis niloticus) with NB-O₃ can enhance specific immune responses and improve efficacy of immersion vaccination against Streptococcus agalactiae. Spleen and head kidney of fish in the vaccinated groups showed a substantial upregulation in expression levels of pro-inflammatory cytokine genes (IL-1β, TNF-α, IL-6) and immunoglobulin classes (IgM, IgD, IgT) compared with the unvaccinated control groups. The mRNA transcript of pro-inflammatory cytokine genes was greatest (approx. 2.8-3.3 folds) on day 7 post-vaccination, whereas the relative expression of immunoglobulin genes was greatest (approx. 3.2-4.1 folds) on day 21 post-immunization. Both systemic and mucosal IgM antibodies were elicited in vaccinated groups. As the result, the cumulative survival rate of the vaccinated groups was found to be higher than that of the unvaccinated groups, with a relative percent survival (RPS) ranging from 52.9 to 70.5%. However, fish in the vaccinated groups that received pre-treatment with NB-O₃, bacterial antigen uptakes, expression levels of IL-1β, TNF-α, IL-6,IgM, IgD, and IgT, as well as the specific-IgM antibody levels and percent survival, were all slightly or significantly higher than that of the vaccinated group without pre-treatment with NB-O₃. Taken together, our findings suggest that utilizing pre-treatment with NB-O₃ may improve the immune response and efficacy of immersion vaccination in Nile tilapia.

Fundamentals of Fish Vaccination

Fish health management has become a critical component of disease control and is invaluable for improved harvests and sustainable aquaculture. Vaccination is generally accepted as the most effective prophylactic measure for fish disease prevention, on environmental, social, and economic grounds. Although the historical approach for developing fish vaccines was based on the principle of Louis Pasteur's "isolate, inactivate and inject," but their weak immunogenicity and low efficacies in many cases, have shifted the focus of fish vaccine development from traditional to next-generation technologies. However, before any fish vaccine can be successfully commercialized, several hurdles need to be overcome regarding the production cost, immunogenicity, effectiveness, mode of administration, environmental safety, and associated regulatory concerns. In this context, the chapter summarises the basic aspects of fish vaccination such as type of vaccine, modalities of vaccine delivery, the immunological basis of fish immunization as well as different challenges associated with the development process and future opportunities.

Pseudo-Laminarization of Mixed Microbubble Water and Complex Fluids in Capillary Flows

Symmetry in fluid flow is determined by external factors such as magnetic or electric fields. Owing to the electrical properties of fluids, liquids containing fine bubble or ionic surfactant molecules differ from the normal fluid flow. Therefore, the pressure drop and frictional coefficient in a pipe are measured and estimated for water alone, for mixed microbubble water (MB), and for complex fluids (anionic surfactant solution and polymer solution) in capillary flow with constant flow rate. For water alone, good agreement is obtained between the experimental and theoretical values for laminar Hagen–Poiseuille flow and the Blasius expression in turbulent flow. For the MB, pseudo-laminarization is suggested up to a Reynolds number of 4.2×103. Both the anionic surfactant solution and the polymer solution exhibit the same tendency as that of the MB. In explaining these behaviors, elasticity and electrical interaction are discussed, and electrical interaction on the capillary wall is strongly suggested to be a contributing factor. Additionally, surface tension is investigated and supports the discussion.

An effective live attenuated vaccine against Aeromonas veronii infection in the loach (Misgurnus anguillicaudatus)

Aeromonas veronii is a major pathogenic bacterium in humans and animals. When it causes outbreaks, there are enormous economic losses to the aquaculture industry. An effective live attenuated vaccine strain, ΔhisJ, was obtained in our previous studies by gene knockout in Aeromonas veronii TH0426 using the suicide vector pRE112. Here, we evaluated whether the live attenuated vaccine ΔhisJ was suitable for prevention of Aeromonas veronii infection by injection and immersion in loaches. Compared with that of the TH0426 wild-type strain, the virulence of the live vaccine was significantly weakened. Vaccine safety assessment results also indicated that 1 × 10⁷ CFU/mL live vaccine was safe and did not induce clinical symptoms or obvious pathological changes. Additionally, after challenging loaches with Aeromonas veronii TH0426, the relative percent survival of the IN3 injection group was 65.66%, and that of the IM group was 50.78%. Our data show that the live attenuated vaccine ΔhisJ can improve the immune protection rate of loaches. Furthermore, increased enzyme activity parameters (SOD, LZM, ACP, and AKP) in the skin mucus, increased enzyme activity parameters (SOD, LZM, ACP, AKP, and GPx) in the serum, increased specific IgM antibodies and cytokine IL-1β contents in the serum, and increased cytokine (IL-15, pIgR, IL-1β, and TNF-α) expression in the liver and spleen were observed. These data are the first to indicate that the live attenuated vaccine ΔhisJ is suitable for the development of a safe and effective vaccine against Aeromonas veronii infection in loach aquaculture.

β-glucan and anisodamine can enhance the immersion immune efficacy of inactivated cyprinid herpesvirus 2 vaccine in Carassius auratus gibelio

As one of the most important fish in freshwater aquaculture, gibel carp (Carassius auratus gibelio) is easily susceptible to Cyprinid herpesvirus 2 (CyHV-2). Immersion vaccination has attracted many researchers due to its simple operation in preventing infectious diseases. However, the unavoidable disadvantage is that the immersion vaccine must be used with adjuvants to get a better performance. In this study, gibel carps were vaccinated by a 60 min bath in a β-propiolactone-inactivated Cyprinid herpesvirus 2, mixed with DTT, β-glucan, anisodamine and scopolamine, respectively. After immunization, the fishs were challenged by CyHV-2 in 2 weeks. By analyzing pathological section, we found that β-glucan, anisodamine and scopolamine groups protected the gibel carp compared to the control group, which was consistent with the trend of survival rate. Specifically, β-glucan group in serum appeared best on lysozyme, TSOD and complement C3. Real time quantitative RT-PCR results demonstrated that in both spleen and head kidney tissues, mRNA expressions of typical Th1 immune response cytokines IL-2 and IFN-γ2 in β-glucan group and anisodamine group were significantly higher than other groups and the level of immunoglobulins related to systemic immunity (IgM) and mucosal immunity (IgZ) were also enhanced in the immune period. DTT group slightly affected immune gene and serum enzyme activity, while did not show an adjuvant effect on survival rate. In addition, four adjuvant groups could obviously inhibit CyHV-2 replication. This study explored and proved the good efficiency of β-glucan or anisodamine as immersion immune adjuvant and also provided reference for improving the efficiency of immersion immunity.

Review on Immersion Vaccines for Fish: An Update 2019

Immersion vaccines are used for a variety of aquacultured fish to protect against infectious diseases caused by bacteria and viruses. During immersion vaccination the antigens are taken up by the skin, gills or gut and processed by the immune system, where the resulting response may lead to protection. The lack of classical secondary responses following repeated immersion vaccination may partly be explained by the limited uptake of antigens by immersion compared to injection. Administration of vaccines depends on the size of the fish. In most cases, immersion vaccination is inferior to injection vaccination with regard to achieved protection. However, injection is problematic in small fish, and fry as small as 0.5 gram may be immersion vaccinated when they are considered adaptively immunocompetent. Inactivated vaccines are, in many cases, weakly immunogenic, resulting in low protection after immersion vaccination. Therefore, during recent years, several studies have focused on different ways to augment the efficacy of these vaccines. Examples are booster vaccination, administration of immunostimulants/adjuvants, pretreatment with low frequency ultrasound, use of live attenuated and DNA vaccines, preincubation in hyperosmotic solutions, percutaneous application of a multiple puncture instrument and application of more suitable inactivation chemicals. Electrostatic coating with positively charged chitosan to obtain mucoadhesive vaccines and a more efficient delivery of inactivated vaccines has also been successful.