Detection of cyprinid herpesvirus 1 (CyHV-1) in barbel (Barbus barbus): First molecular evidence for the presence of CyHV-1 in fish other than carp (Cyprinus carpio)

Development of multi epitope subunit vaccines against emerging carp viruses Cyprinid herpesvirus 1 and 3 using immunoinformatics approach

Cyprinid herpesvirus is a causative agent of a destructive disease in common and koi carp (Cyprinus carpio), which leads to substantial global financial losses in aquaculture industries. Among the strains of C. herpesvirus, C. herpesvirus 1 (CyHV-1) and C. herpesvirus 3 (CyHV-3) are known as highly pathogenic to carp fishes in Europe, Asia, and Africa. To date, no effective vaccine has been developed to combat these viruses. This study aimed to develop unique multi-epitope subunit vaccines targeting the CyHV-1 and CyHV-3 using a reverse vaccinology approach. The study began with a comprehensive literature review to identify the most critical proteins, which were then subjected to in silico analyses to predict highly antigenic epitopes. These analyses involved assessing antigenicity, transmembrane topology screening, allergenecity, toxicity, and molecular docking approaches. We constructed two multi-epitope-based vaccines incorporating a suitable adjuvant and appropriate linkers. It revealed that both the vaccines are non-toxic and immunogenic. The tertiary structures of the vaccine proteins were generated, refined, and validated to ensure their suitability. The binding affinity between the vaccine constructs and TLR3 and TLR5 receptors were assessed by molecular docking studies. Molecular dynamics simulations indicated that vaccine construct V1 exhibited greater stability with both TLR3 and TLR5 based on RMSD analysis. Hydrogen bond analysis revealed a stronger binding affinity between the vaccine constructs and TLR5 compared to TLR3. Furthermore, MM-PBSA analysis suggested that both vaccine constructs exhibited a better affinity for TLR5. Considering all aspects, the results suggest that in silico development of CyHV vaccines incorporating multiple epitopes holds promise for management of diseases caused by CyHV-1 and CyHV-3. However, further in vivo trials are highly recommended to validate the efficacies of these vaccines.

Partial genetic characterisation of a novel alloherpesvirus detected by PCR in a farmed wels catfish (Silurus glanis)

By a broad-range PCR, we detected a novel herpesvirus (HV) in the specimen of a wels catfish (Silurus glanis) presenting disseminated, carp pox-like dermal lesions all over its body. The sequence analysis of the 463-bp PCR product from the viral DNA polymerase gene indicated the presence of a hitherto unknown virus, a putative member of the family Alloherpesviridae in the sample. Another PCR, targeting the terminase gene of fish HVs, provided an additional genomic fragment of over 1,000 bp. Surprisingly, the sequence of a co-amplified, off-target PCR product revealed its origin from a putative gene homologous to ORF87 and ORF45 of cyprinid HVs and anguillid herpesvirus 1 (AngHV-1), respectively. With specific primers, designed according to the genomic maps of the cyprinid and anguillid HVs, a genomic fragment of 15 kb was also amplified and sequenced by primer walking. In phylogeny inferences, based on several genes, the putative wels catfish HV clustered closest to various cyprinid HVs or to AngHV-1. The novel virus, named as silurid herpesvirus 2, represents a distinct species in the genus Cyprinivirus. However, its association with the skin disease remains unclear.

Detection of Carp pox virus (CyHV-1) from koi (Cyprinus carpio L.) in Iran; clinico-pathological and molecular characterization

Cyprinid herpesvirus 1 (CyHV-1) is the causative agent of carp pox characterized by epidermal papillomas in common carp and other cyprinids. In this study, we identified CyHV-1 in koi (Cyprinus carpio) from Iran in 2017 and 2019, showing clinical signs of the carp pox disease. Histopathology showed severe epidermal hyperplasia and the absence of club and goblet cells. Degenerative changes, including spongiosis and single-cell necrosis, were also observed. Keratinocyte dysplasia and a moderate lymphocytic infiltration were observed within the epidermis. PCR of the extracted DNA from skin lesions of affected koi from both outbreaks showed CyHV-1 specific TK amplicons, with high sequence identity (above 99%) among themselves and with other CyHV-1 isolates belong to Cluster I, as well as show 97% similarity to Cluster II isolates. To the best of our knowledge, this is the first report of Carp pox disease (CyHV-1) of koi in Iran and the Middle East.