CCB

Electron Microscopic Observation of Infected CCB and Whole Genome Analysis of Koi Herpesvirus Isolate GY01

Cyprinid herpesvirus-3 (CyHV-3), also known as Koi herpesvirus (KHV), causes infectious and acute viremia in common and koi carp (Cyprinus carpio). In a previous study, a KHV isolate, GY1506 (KHV GY01 in GeneBank), was isolated from diseased common carp, cultured on CCB cells, and identified by PCR targeting the thymidine kinase (TK) gene and phylogenetic analysis. Further characterization and epidemiological features of this strain were studied through electron microscopy and whole-genome analysis.

Electron microscopy of CCB cells infected with KHV GY01 revealed incomplete nuclear membranes, deformed nuclei, marginalized nuclear chromosomes, and immature viruses arranged in a lattice pattern in the cytoplasm and nucleus (Fig. 1). Many mature and immature virus particles were observed. Three types of viruses were identified: hexagonal hollow structures, round capsules with dense internal substances, and clear visible structures of capsules, capsids, and cores. Viruses with or without capsules in GY01-infected CCB cells measured approximately 90nm by 110nm. A clear hexagonal virus was visible at the nuclear membrane edge (arrow). The cytoplasm protruded into a bubble (Fig. 2B).

Lactobacilli-Derived Postmetabolites are Broad-Spectrum Inhibitors of Herpes Viruses In Vitro

Herpes viruses cause significant health, social, and economic losses across vertebrates. Lactic acid bacteria (LAB) are known to protect against pathogens through their metabolic compounds. Danova et al. evaluated the inhibitory properties of nine LAB postmetabolites against HSV-1 and KHV using cytotoxicity, cytopathic effect inhibition, virucidal effect, and protective effect assessments. They aim to explore the potential of LAB postmetabolites in preventing and treating herpes diseases.

Before the antiviral experiments, the non-toxic range of each sample was determined on Madin-Darby bovine kidney (MDBK) and common carp brain (CCB) cell lines. Cytotoxicity was measured at 48 hours on MDBK cells and at 72 hours on CCB cells, following the antiviral evaluation protocol (Fig. 3). Figure 4 shows that all postbiotics were more toxic than the reference chemotherapeutic acyclovir (ACV). Cytotoxicity was slightly higher in CCB cells, likely due to 24 hours longer exposure (72 hours) compared to MDBK cells (48 hours). The Mix-sample group (S7, S8, and S9) had the lowest toxicity. S9 was the least cytotoxic, followed by S6, S3, S1, and S4. S5 and S2 showed the highest cytotoxicity (Fig. 4).