Production and characterization of monoclonal antibodies against mandarinfish ranavirus and first identification of pyloric caecum as the major target tissue

Abstract

Mandarinfish ranavirus (MRV), also known as a variant of largemouth bass virus (LMBV), is an emerging pathogen in mandarinfish aquaculture. In this study, monoclonal antibodies (mAbs) against MRV were produced and characterized, and 7 mAbs were obtained through Western blotting screening and all 7 mAbs specifically recognized MRV/LMBV but not several piscine iridoviruses as ISKNV, GIV and TFV. By LC MS/MS analysis, the recognized viral proteins by seven mAbs were identified as MRV‐pORF47L, MRV‐pORF55R, MRV‐pORF57L, MRV‐pORF77L and MRV‐pORF78L, respectively, and all five viral proteins are late expression structural proteins by Western blotting. Based on mAb 1C4, immuno‐histochemistry and immuno‐histo‐fluorescence were performed to re‐assess the tissue tropism of MRV. The result showed that abundant reactive signals were observed in infected spleen, kidney as well as intestine and pyloric caecum. Real‐time quantitative PCR also demonstrated that spleen as well as pyloric caecum and intestines are the major target tissue upon MRV infection. In infected intestines and pyloric caecum, numerous enlarged, multinucleated cells with intracytoplasmic inclusions were identified as the target cells of MRV, suggesting that MRV serves as a digestive tract pathogen to mandarinfish, which may explain why acute infection of MRV can cause the typical clinicopathology featured by severe ascites.

Peripheral B Lymphocyte Serves as A Reservoir for The Persistently Covert Infection of MandarinfishSiniperca chuatsiRanavirus

“…Specifically, ranaviruses can be classified into two subclasses: FV3 cluster in the ALRV subclass, primarily infecting amphibians and reptiles, and MRV cluster in LMBV-Like, which alongside GIV-like, only infects bony fish (5). At genomic level, the ALRV subclass genome is approximately 105 kb (1,58), the GIV genome is about 140 kb (59), and the MRV genome is only about 98kb (3,4). Notably, the homology between MRV and ALRV main capsid protein is only 84%.…”

“…Iridovirus is a large viral family, with a linear double-stranded DNA (dsDNA), genome sizes ranging from 98 kb to 220 kb and encoding open reading frames (ORFs) ranging from 98 to 221 (1)(2)(3)(4).…”

“…Iridovirus is a large viral family, with a linear double-stranded DNA (dsDNA), genome sizes ranging from 98 kb to 220 kb and encoding open reading frames (ORFs) ranging from 98 to 221(1-4). The Iridoviridae family can be divided into two subfamilies, namely, Alphairidovirinae and Betairidovirinae , and also are referred to vertebrate iridovirus (VI) and invertebrate iridovirus (IVI), respectively(2).…”

“…The known sensitive natural hosts of MRV/LMBV include largemouth bass ( Micropterus salmoides )(9, 10), koi carp ( Cyprinus carpio )(11), barcoo grunter ( Scortum barcoo )(12), two tropical ornamental fish, Doctor fish ( Labroides dimidatus ) and Guppy ( Poecilia reticulata )(13) as well as mandarinfish ( Siniperca chuatsi )(3, 14, 15). In mandarinfish, MRV infection generally manifests in two distinctive clinical phenotypes: acute and chronic(4, 14, 15). During acute infection, morbidity generally occurs at 2-4 days post-infection, and is characterized by vomiting and then severe ascites syndrome(15).…”

The Inactivated ISKNV-I Vaccine Confers Highly Effective Cross-Protection against Epidemic RSIV-I and RSIV-II from Cultured Spotted Sea Bass Lateolabrax maculatus

“…Members of the family Iridoviridae are large, icosahedral viruses, containing circular, double-stranded DNA genomes with sizes ranging from 98.6 kb to 212 kb, consisting of 97 to 211 open reading frames (ORFs) and causing severe systemic diseases resulting in significant economic and environmental effects worldwide ( 1 – 4 ). According to the latest release of the International Committee on Taxonomy of Viruses ( https://talk.ictvonline.org/taxonomy/ ), the family Iridoviridae is composed of seven genera.…”