Complexes of Ag and ZnO nanoparticles with BBR for enhancement of gastrointestinal antibacterial activity through the impacts of size and composition.

This study introduces the bioformulations of Ag/BBR and ZnO/BBR complexes against pathogenic bacteria in the gastrointestinal tract. Without the use of toxic reduction agents, Ag and ZnO NPs were prepared using an electrochemical method and then facially mixed with BBR solution to form Ag/BBR and ZnO/BBR complexes. BBR molecules are strongly conjugated with Ag and ZnO NPs through coordinated bonding and electrostatic interaction. As a result, the presence of BBR significantly influenced the nanoparticle growth, resulting in the formation of core/shell structured Ag/BBR and ZnO/BBR NPs with small particle sizes. The antibacterial test showed that BBR, Ag, or ZnO components all contributed to the increase of antibacterial ability of Ag/BBR and ZnO/BBR NPs against both methicillin-resistant Staphylococcus aureus (MRSA) and Salmonella enteritidis (S. enteritidis). The bactericidal ability of Ag/BBR and ZnO/BBR complexes against MRSA was exhibited even at a concentration of four-fold dilution (corresponding to 1.25 g L-1 of BBR and 46.25 mg L-1 of Ag) and two-fold dilution (corresponding to 2.5 g L-1 of BBR and 10 mg L-1 of ZnO), respectively, while that of the Ag/BBR complex against S. enteritidis showed at a concentration of two-fold dilution corresponding to 2.5 g L-1 of BBR and 92.5 mg L-1 of Ag. The results obtained in this study support that Ag/BBR and ZnO/BBR complexes can be potential therapeutic agents against gastrointestinal infections.

α-Enolase as a novel vaccine candidate against Streptococcus dysgalactiae infection in cobia (Rachycentron canadum L.).

Streptococcus dysgalactiae is an important pathogenic bacterium that has caused economic loss for the cobia industry in Taiwan, ROC. This study presents a highly effective subunit vaccine composed of a moonlight protein, α-enolase, for the prevention of S. dysgalactiae infection. First, α-enolase was cloned, transformed, and expressed in E. coli for production of recombinant protein. Then, the protective efficacies of α-enolase recombinant protein were evaluated in combination with either a pro-inflammatory cytokine, TNF-α, or an oil adjuvant, ISA 763 AVG. The results showed that the combination of α-enolase and ISA 763 AVG was highly protective (RPS = 88.89%), while a negative effect was found in the group immunised with α-enolase adjuvanted with TNF-α (RPS = 22.22%). A further study was conducted with double dose of ISA 763 AVG, which led to an increased RPS value of 97.37%. Moreover, immunised cobia exhibited significantly greater lysozyme activity, antibody responses, and expression of certain immune-related genes post-challenge. Altogether, our results demonstrated that a combination of α-enolase recombinant protein with ISA 763 AVG adjuvant is a promising vaccine that can be employed for protection of cobia against S. dysgalactiae infection.

Identification of protective protein antigens for vaccination against Streptococcus dysgalactiae in cobia (Rachycentron canadum).

Streptococcus dysgalactiae is considered a causative agent of severe infection and economic loss for the cobia industry in Taiwan. In this study, protective antigens of this pathogenic bacterium were identified and screened in cobia (Rachycentron canadum). Outer surface proteins (OMPs) of this pathogen were extracted using mutanolysin digestion. Immunogenic targets were detected by western blot and then subjected to peptide sequencing using NanoLC-MS/MS. Two surface proteins, namely phosphoenolpyruvate protein phosphotransferase (PtsA) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), showed strong reactions with cobia antisera against S. dysgalactiae. Recombinant proteins were produced in Escherichia coli cells and their protective efficacies were investigated in cobia. Fish immunised with recombinant proteins, rPtsA + ISA (ISA 763 AVG) and rGAPDH + ISA, elicited higher levels of specific antibody responses against the recombinant proteins and had high levels of lysozyme activity. Notably, vaccinated fish were protected from lethal challenge with relative percentage of survival (RPS) values for rPtsA + ISA and rGAPDH + ISA groups being 91.67% and 83.33%, while 0% RPS value was found in both ISA injected and control groups. The results presented in the study demonstrate that the GAPDH and PtsA are promising vaccine candidates for preventing S. dysgalactiae disease in cobia.

A formalin-inactivated vaccine provides good protection against Vibrio harveyi infection in orange-spotted grouper (Epinephelus coioides).

Vibrio harveyi is one of the most common threats to farmed grouper, so considerable efforts are in practice to control the pathogen. This study presents a highly effective vaccine against V. harveyi in the orange-spotted grouper with the help of a single intraperitoneal immunization. The vaccine candidate was in form of whole, formalin-inactivated V. harveyi cells combined with a metabolizable ISA763 AVG adjuvant. Our results indicated that the vaccine triggered a remarkably higher expression level of interleukin (IL)-1ß, IL-6, IL-8, and IL-10 in the groupers' kidneys and spleens, as recorded after 1 and 3 days of immunization. Antibody titers were significantly elevated in the vaccinated fish. A pivotal observation was that the vaccine highly protected the grouper from a homologous V. harveyi strain challenge with relative percentage survival values of 100% and 91.7% at 6 and 12 weeks post-immunization, respectively. Vaccinated fish also demonstrated strong cross-protection against a heterologous bacterial isolate challenge. Therefore, the inactivated V. harveyi vaccine is a promising candidate that could stimulate good immune responses and confer remarkable protection in farmed groupers.