Evaluation of Formalin-Inactivated Vaccine Efficacy against Red Seabream Iridovirus (RSIV) in Laboratory and Field Conditions.

Red seabream iridovirus (RSIV) is a major cause of marine fish mortality in Korea, with no effective vaccine available since its first occurrence in the 1990s. This study evaluated the efficacy of a formalin-killed vaccine against RSIV in rock bream under laboratory and field conditions. For the field trial, a total of 103,200 rock bream from two commercial marine cage-cultured farms in Southern Korea were vaccinated. Farm A vaccinated 31,100 fish in July 2020 and monitored them for 18 weeks, while farm B vaccinated 30,700 fish in August 2020 and monitored them for 12 weeks. At farm A, where there was no RSIV infection, the vaccine efficacy was assessed in the lab, showing a relative percentage of survival (RPS) ranging from 40% to 80%. At farm B, where natural RSIV infections occurred, cumulative mortality rates were 36.43% in the vaccinated group and 80.32% in the control group, resulting in an RPS of 54.67%. The RSIV-infectious status and neutralizing antibody titers in serum mirrored the cumulative mortality results. This study demonstrates that the formalin-killed vaccine effectively prevents RSIV in cage-cultured rock bream under both laboratory and field conditions.

Effects on viral suppression and the early-immune expression of ribavirin against spring viremia of carp virus in vitro.

Spring viremia of carp virus (SVCV) is a globally distributed virus that causes severe clinical symptoms and high mortality in fish belonging to the families Cyprinidae and Siluridae. To protect the host against viral infection, understanding the relatedness between viral susceptibility and antiviral mechanisms must be crucial. Thus, we evaluated the viral suppression efficacy of ribavirin by measuring the transcription levels of viral and immune genes in vitro. The results showed that following ribavirin treatment after SVCV infection (MOI 0.1), ribavirin inhibited SVCV replication in epithelioma papulosum cyprini (EPC) cells and completely inhibited viral gene (G and N) expression at concentrations above 10 µg/mL at 48 h post-infection. Ribavirin does not directly damage SVCV particles but inhibits early viral replication. In the absence of SVCV infection, the immunological dynamics triggered by ribavirin resulted in upregulated pattern recognition receptors and proinflammatory cytokine-related genes (i.e., PI3K, MYD88, IRAK1, RIG-І, MAVS, Mx1, TNF-α, and NF-κB). Furthermore, EPC cells treated with ribavirin following SVCV infection showed upregulation of PI3K, MYD88, IRAK1, RIG-І, TNF-α, and NF-κB genes within 24 h post-SVCV infection, suggesting that ribavirin positively inhibits the SVCV infection in vitro.

Diagnostic performance of cross-priming amplification-based lateral flow assay (CPA-LFA) and real-time PCR for koi herpesvirus (KHV) detection.

Epizootics of Koi herpesvirus (KHV) cause mass mortality in koi carp (Cyprinus rubrofuscus) and common carp (Cyprinus carpio) worldwide. Rapid and accurate virus detection technology is crucial for preventing pathogen spread and minimizing damage. Although several diagnostic assays have been developed for KHV, the analytical and diagnostic performance of the detection methods has not been evaluated. In this study, we developed and validated the diagnostic performance of two molecular diagnostic assays, cross-priming amplification-based lateral flow assay (CPA-LFA) and TaqMan probe-based real-time polymerase chain reaction (PCR). To detect KHV, primers and probe were designed based on the thymidine kinase (TK) genes. The detection limits of developed CPA-LFA and real-time PCR assays were determined to be 675.69 copies/µL and 8.384 copies/µL, respectively. The diagnostic sensitivity and specificity of the developed assay were determined using fish samples (n = 179). CPA-LFA was found to be 93.67% and 100%, respectively, and real-time PCR was found to be 100% and 100%, respectively. Therefore, the newly developed CPA-LFA and real-time PCR assays accurately and rapidly detect KHV. CPA-LFA is particularly suitable for point-of-care diagnosis because of its simple diagnostic process, and real-time PCR analysis is most suitable for precise diagnosis because it can detect low viral loads.

Far-field radiation of photonic crystal organic light-emitting diode.

Utilizing the near- to far-field transformation based on the 3-D finite difference time domain (FDTD) method and Fourier transformation, the far-field profile of a photonic crystal organic light emitting diode is studied to understand the viewing angle dependence. The measured far-field profiles agree well with those of the simulation. The enhancement of the extraction efficiency in excess of 60% is observed for the optimized photonic crystal pattern.

High quality-factor whispering-gallery mode in the photonic crystal hexagonal disk cavity.

We study whispering-gallery-like modes in photonic crystal air-bridge slab micro-cavities having H2 defects using finite-difference time-domain calculations. The defect geometry is optimized to increase the quality factor (Q) of the H2-cavity whispering-gallery mode (WGM). By symmetrically distributing 12 nearest neighbor holes around the defect and controlling size of holes, it is possible to drastically increase the Q of >10(5) while preserving effective mode volume of the order of the cubic wavelength in material. In addition, we investigate the effect of a dielectric circular post located around the center of the H2 cavity. This post can act as current and heat flow paths that promise electrically-pumped thermally-stable lasing operation. It is interesting to observe that the introduction of the post structure increases the Q of the WGM up to 4x10(5) and the high Q >10(5) is still maintained even with large post size. Although diffractive out-coupling through the post is increased, radiated power outside the post is suppressed, which leads to large enhancement of the Q of the H2-cavity WGM.

Coupling of small, low-loss hexapole mode with photonic crystal slab waveguide mode.

Coupling characteristics between the single-cell hexapole mode and the triangular-lattice photonic crystal slab waveguide mode is studied by the finite-difference time-domain method. The single-cell hexapole mode has a high quality factor (Q) of 3.3Chi106 and a small modal volume of 1.18(lambda/n)3. Based on the symmetry, three representative types of coupling geometries (shoulder-couple, butt-couple and side-couple structures) are selected and tested. The coupling efficiency shows strong dependence on the transverse overlap of the cavity mode and the waveguide mode over the region of the waveguide. The shoulder-couple structure shows best coupling characteristics among three tested structures. For example, two shouldercouple waveguides and a hexapole cavity result in a high performance resonant-tunneling-filter with Q of 9.7Chi105 and transmittance of 0.48. In the side-couple structure, the coupling strength is much weaker than that of the shoulder-couple structure because of the poor spatial overlap between the mode profiles. In the direct-couple structure, the energy transfer from the cavity to the waveguide is prohibited because of the symmetry mismatch and no coupling is observed.