Sang Wha Kim

Efficacy of PLGA microparticle-encapsulated formalin-killed Aeromonas hydrophila cells as a single-shot vaccine against A. hydrophila infection

Control and prevention of disease is a high priority in aquaculture, and vaccination is important to prevent outbreaks. Here, poly(d,l-lactide-co-glycolic acid) (PLGA) microparticles (MPs) approximately 36μm in diameter were used to encapsulate and deliver Aeromonas hydrophila formalin-killed cells (FKC) as an antigen, and the innate and adaptive immune responses of cyprinid loaches and common carp were assessed following vaccination. The antigen was confirmed to be well encapsulated by scanning electron microscopy analysis of PLGA MP sections. Blood and head kidney specimens were collected and analyzed for bacterial agglutination activity and relative mRNA expression of immune-related genes (IL-1β, IL-10, TNF-α, lysozyme C, TGF-β, and IgM) at 2, 4, 6, and 8weeks post vaccination (wpv). For both fish species, the curve of antibody titer over time was shallower in the PLGA group than the FKC group. These titers in loaches and carp were very similar in the two vaccination groups until 8 and 6 wpv, respectively, but differences were subsequently noted in both species until the end of experiment. Loaches and carp were then challenged with A. hydrophila at 12 and 20 wpv, and 10 and 14 wpv, respectively, and relative survival rates were calculated. For both species, the PLGA groups demonstrated higher survival rates at all time points. Relative expression of IL-1β and TNF-α mRNA was significantly upregulated in the PLGA group at 2 and 4 wpv. Moreover, PLGA-MP vaccination increased relative mRNA levels of lysozyme C and IgM, which were significantly higher than those observed with FKC treatment at 2 wpv and 4, 6, and 8 wpv, respectively. In conclusion, PLGA-MP vaccines have the potential to induce longer and more potent immune responses than FKCs alone, and protect both cyprinid loaches and common carp with greater efficiency.

Effects of algal toxin okadaic acid on the non-specific immune and antioxidant response of bay scallop (Argopecten irradians)

&NA; Okadaic acid (OA) is produced by dinoflagellates during harmful algal blooms and is a diarrhetic shellfish‐poisoning (DSP) toxin. This toxin is particularly problematic for bivalves that are cultured for human consumption. This study aimed to reveal the effects of exposure to OA on the non‐specific immune responses of bay scallop, Argopecten irradians. Various immunological parameters (superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (ALP), lysozyme activities, and total protein level) were assessed in the hemolymph of bay scallops at 3, 6, 12, 24, and 48 h post‐exposure (hpe) to different concentrations (50, 100, and 500 nM) of OA. Moreover, the expression of immune system‐related genes (MnSOD, PrxV, PGRP, and BD) was also measured. Results showed that SOD and ACP activities were decreased between 12 and 48 hpe. The ALP, lysozyme activities, and total protein levels were also modulated after exposure to different concentrations of OA. The expression of immune‐system‐related genes was also assessed at different time points during the exposure period. Overall, our results suggest that the exposure to OA had negative effects on the antioxidant and non‐specific immune responses, and even disrupted the metabolism of bay scallops, making them more vulnerable to environmental stress‐inducing agents; they provide a better understanding of the response status of bivalves against DSP toxins. HighlightsEffect of okadaic acid (OA) on the bay scallop was investigated.Cytokine responses of bay scallop were altered by OA.Immune and antioxidant responses to OA were time and concentration‐dependent.

Complete Genome Sequence of a Bacteriophage, pVco-5, That Infects Vibrio coralliilyticus, Which Causes Bacillary Necrosis in Pacific Oyster (Crassostrea gigas) Larvae

ABSTRACT We report here the complete genome sequence of the Vibrio coralliilyticus-specific phage pVco-5, a double-stranded DNA virus isolated from an oyster hatchery tank. Vibrio coralliilyticus causes bacillary necrosis in marine bivalve larvae; hence, phage pVco-5 could be used to prevent V. coralliilyticus infections in these larvae.

Concentration-dependent reduction of planktonic- and biofilm-state Vibrio alginolyticus by the bacteriophage pVa-21

There is an increasing emergence of antibiotic-resistant Vibrio alginolyticus, a zoonotic pathogen that causes mass mortality in aquatic animals as well as human infection; therefore, there is a demand for alternatives to antibiotics for treatment and prevention of infections caused by this pathogen. One possibility is through the exploitation of bacteriophages. In the present study, the bacteriophage pVa-21 belonging to Myoviridae, was isolated and characterized as a candidate biocontrol agent against V. alginolyticus. Its morphology, host range and infectivity, growth characteristics, planktonic or biofilm lytic property, stability under various conditions, and genome were investigated. Its latent period and burst size were estimated to be approximately 70 min and 58 plaque-forming units/cell, respectively. In addition, phage pVa-21 could inhibit bacterial growth both in the planktonic and biofilm state. Furthermore, phylogenetic and genome analyses revealed that the phage is closely related to ‘phiKZ-like phages’ and can be classified as a new member of the phiKZ-like phages that infect bacteria belonging to the family Vibrionaceae.

Corrigendum: Therapeutic Effect of Intestinal Autochthonous Lactobacillus reuteri P16 Against Waterborne Lead Toxicity in Cyprinus carpio

[This corrects the article DOI: 10.3389/fimmu.2018.01824.].

Isolation of a zoonotic pathogen Aeromonas hydrophila from freshwater stingray (Potamotrygon motoro) kept in a Korean aquarium with ricefish (Oryzias latipes)

In the present study, Aeromonas (A.) hydrophila was isolated from a captive-bred adult freshwater stingray (Potamotrygon motoro) reared at a commercial aquarium in Korea. The stingray had bites on its fins, hemorrhages on the ventral part, and congested internal organs. A bacterium was isolated from kidney and subsequently identified as A. hydrophila. Based on phylogenetic analysis results, the isolate in the present study (SNUAh-LA1) was most closely related to A. hydrophila AH10 (China) and A. hydrophila AKR1 (Korea). It is most likely that the pathogen infection resulted from Potamotrygon motoro cohabiting with ricefish (Oryzias latipes).