Dataset Information

An Avirulent Largemouth Bass Birnavirus Vaccine Candidate Protects Largemouth Bass against Birnavirus Infection.

ABSTRACT:

Background

Largemouth bass birnavirus (LBBV) disease outbreaks in largemouth bass fingerlings lead to high mortality in China. Therefore, the development of immersion immunization strategies is paramount.

Methods

An avirulent LBBV strain was screened using a fish challenge assay. The proliferation dynamics of the avirulent strain were determined in vitro and in vivo. The efficacy of the avirulent vaccine was evaluated using immune gene expression, viral load, and a virus challenge, and the safety was also assessed using a reversion to virulence test.

Results

An avirulent virus strain, designated as largemouth bass birnavirus Guangdong Sanshui (LBBV-GDSS-20180701), was selected from five fish birnavirus isolates. The proliferation peak titer was 109.01 TCID50/mL at 24 hpi in CPB cells and the peak viral load was 2.5 × 10⁴ copies/mg at 4 dpi in the head kidneys and spleens of largemouth bass. The largemouth bass that were immersed within an avirulent vaccine or injected with an inactivated vaccine were protected from the virulent LBBV challenge with a relative percent survival (RPS) of 75% or 42.9%, respectively. The expression levels of IL-12, MHCI, MHCII, CD8, CD4, and IgM in the avirulent group were significantly upregulated at a partial time point compared to the inactivated vaccine group. Moreover, the viral load in the avirulent vaccine group was significantly lower than those in the inactivated vaccine group and control group using real-time PCR.

Conclusions

LBBV-GDSS-20180701 is a potential live vaccine candidate against LBBV disease.

SUBMITTER: Fu X

PROVIDER: S-EPMC10747726 | biostudies-literature | 2023 Nov

REPOSITORIES: biostudies-literature

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Publications

An Avirulent Largemouth Bass Birnavirus Vaccine Candidate Protects Largemouth Bass against Birnavirus Infection.

Fu Xiaozhe X Luo Mingju M Lin Qiang Q Liang Hongru H Niu Yinjie Y Luo Xia X Ma Baofu B Li Ningqiu N

Vaccines 20231122 12

<h4>Background</h4>Largemouth bass birnavirus (LBBV) disease outbreaks in largemouth bass fingerlings lead to high mortality in China. Therefore, the development of immersion immunization strategies is paramount.<h4>Methods</h4>An avirulent LBBV strain was screened using a fish challenge assay. The proliferation dynamics of the avirulent strain were determined in vitro and in vivo. The efficacy of the avirulent vaccine was evaluated using immune gene expression, viral load, and a virus challenge ...[more]

PMID: 38140144

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Project description:Largemouth bass (Micropterus salmoides) is an important and fast-growing aquaculture species in China. In 2017, an epidemic associated with severe mortality occurred in fingerlings of largemouth bass in Guangdong, China. The causative pathogen was identified and named as largemouth bass Birnavirus (LBBV) by virome analysis, viral isolation, electron microscopy, genome sequencing, Western blot, indirect immunofluorescence, experimental challenge, and so on. Virome sequencing results showed that the relative abundance reads related to the family Birnaviridae were the highest, occupied ∼25% of the total viral reads. Electron microscopy revealed large numbers of nonenveloped virus particles in the spleen of diseased fish with a diameter of about 53 nm. LBBV was isolated and propagated in Chinese perch brain cells and induced a typical cytopathic effect. LBBV was stable to chloroform, heat, and 5-bromo-2'-deoxyuridine, but sensitive to acid (pH 3.0). The complete genome of LBBV was comprised of segment A with a size 3525 bp and segment B with a size 2737 bp. Phylogenetic analysis basing on RdRp and VP2 protein sequences revealed that LBBV were clustered into one clade with Lates calcarifer Birnavirus (LCBV), sharing 98.7% or 91.9% sequence identity with LCBV, respectively, but only sharing 59.7% and 52.7% sequence identity with Blosnavirus, suggesting that LBBV and LCBV probably belonged to a new genus. Challenge experiments results indicated that clinical disease symptoms similar to those observed naturally were replicated and the cumulative mortality reached 100% at 3 dpi by i.p. injection. The investigation of prevalence of LBBV infection showed that 41.5% (17/41) sample pools collected from diseased ponds was positive during 2017-2020, indicating that an emerging outbreak of this disease may be spreading within the largemouth bass in China. Above results confirmed that LBBV is a novel Birnavirus associated with massive mortality for fingerlings of largemouth bass. This provides a basis for prevention and control of this emerging viral disease. IMPORTANCE Pathogen isolation and identification are vital for emerging infectious outbreaks. Here we report the isolation, determination and characterization of a novel largemouth bass Birnavirus (LBBV) associated with massive mortality in largemouth bass. And genome of LBBV is determined and analyzed. Based on phylogenetic and alignment analysis of genome, we suggest LBBV belongs to a new genus (designated as Perbirnavirus genus) in Birnaviridae family. Our findings will provide a basis for the further study on prevention and control of this emerging viral disease.

Project description:IntroductionNocardia seriolae adversely impacts a diverse range of fish species, exhibiting significant pathogenic characteristics that substantially impede the progress of aquaculture. N. seriolae infects in fish has a long incubation period, and clinical symptoms are not obvious in the early stages. There is presently no viable and eco-friendly approach to combat the spread of the disease. According to reports, N. seriolae primarily targets macrophages in tissues after infecting fish and can proliferate massively, leading to the death of fish. Interferon-gamma (IFN-γ) is a crucial molecule that regulates macrophage activation, but little is known about its role in the N. seriolae prevention.MethodsIFN-γ was first defined as largemouth bass (Micropterus salmoides, MsIFN-γ), which has a highly conserved IFN-γ characteristic sequence through homology analysis. The recombinant proteins (rMsIFN-γ) were obtained in Escherichia coli (E. coli) strain BL21 (DE3). The inflammatory response-inducing ability of rMsIFN-γ was assessed in vitro using monocytes/macrophages. Meanwhile, the protective effect of MsIFN-γ in vivo was evaluated by N. seriolae infection largemouth bass model.ResultsIn the inflammatory response of the monocytes/macrophages activated by rMsIFN-γ, various cytokines were significantly increased. Interestingly, interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-a) increased by 183- and 12-fold, respectively, after rMsIFN-γ stimulation. rMsIFN-γ improved survival by 42.1% compared with the control. The bacterial load in the liver, spleen and head kidney significantly decreased. rMsIFN-γ was also shown to better induce increased expression of IL-1β, TNF-α, hepcidin-1(Hep-1), major histocompatibility complex I (MHCI), and MHC II in head kidney, spleen and liver. The histopathological examination demonstrated the transformation of granuloma status from an early necrotic foci to fibrosis in the infection period. Unexpectedly, the development of granulomas was successfully slowed in the rMsIFN-γ group.DiscussionThis work paves the way for further research into IFN-γ of largemouth bass and identifies a potential therapeutic target for the prevention of N. seriolae.

Dataset Information

An Avirulent Largemouth Bass Birnavirus Vaccine Candidate Protects Largemouth Bass against Birnavirus Infection.

Background

Methods

Results

Conclusions

Publications

An Avirulent Largemouth Bass Birnavirus Vaccine Candidate Protects Largemouth Bass against Birnavirus Infection.

Similar Datasets

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