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Huang S, Zheng R, Kang Y, Yang L, Gao J, Liu Q, Weng S, He J, Xie J. Orange-spotted grouper IFNh response to NNV or MSRV and its potential antiviral activities. FISH & SHELLFISH IMMUNOLOGY 2024; 145:109345. [PMID: 38154761 DOI: 10.1016/j.fsi.2023.109345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 12/23/2023] [Accepted: 12/24/2023] [Indexed: 12/30/2023]
Abstract
Type I interferon (IFN) plays a crucial role in the antiviral immune response. Nervous necrosis virus (NNV) and Micropterus salmoides rhabdovirus (MSRV) are the most important viruses in cultured larvae and juveniles, causing great economic losses to fish farming. To better understand the antiviral activities and immunoregulatory role of IFN from orange-spotted grouper (Epinephelus coioides), EcIFNh was cloned from NNV infected sample. EcIFNh has an open reading frame (ORF) of 552 bp and encodes a polypeptide of 183 amino acids. Phylogenetic tree analysis showed that EcIFNh was clustered into the IFNh branch. The tissue distribution analysis revealed that EcIFNh was highly expressed in the liver and brain of healthy orange-spotted grouper. The mRNA levels of EcIFNh were significantly upregulated after poly (I:C) stimulation and NNV or MSRV infection. Furthermore, the promoter of EcIFNh was characterized and significantly activated by EcMDA5, EcMAVS, EcSTING, EcIRF3, and EcIRF7 in the luciferase activity assays. We found that EcIFNh overexpression resisted the replication of NNV and MSRV, while EcIFNh silencing facilitated NNV replication in GB cells. In addition, EcIFNh recombinant protein (rEcIFNh) enhanced the immune response by inducing the expression of ISGs in vivo and in vitro, suggesting the potential application of rEcIFNh for anti-NNV and anti-MSRV. Taken together, our research may offer the foundation for virus-IFN system interaction in orange-spotted grouper.
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Affiliation(s)
- Siyou Huang
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Rui Zheng
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yiling Kang
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Linwei Yang
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jie Gao
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Qingqing Liu
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Shaoping Weng
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Jianguo He
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Junfeng Xie
- State Key Laboratory of Biocontrol, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), China-ASEAN Belt and Road Joint Laboratory on Mariculture Technology, Guangdong Provincial Key Laboratory of Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, China.
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2
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Liang X, Liang J, Cao J, Liu S, Wang Q, Ning Y, Liang Z, Zheng J, Zhang Z, Luo J, Chen Y, Huang X, Huang Y, Qin Q, Zhou S. Oral immunizations with Bacillus subtilis spores displaying VP19 protein provide protection against Singapore grouper iridovirus (SGIV) infection in grouper. FISH & SHELLFISH IMMUNOLOGY 2023:108860. [PMID: 37257567 DOI: 10.1016/j.fsi.2023.108860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 05/28/2023] [Accepted: 05/29/2023] [Indexed: 06/02/2023]
Abstract
Disease caused by Singapore grouper iridovirus (SGIV) results in major economic losses in the global grouper aquaculture industry. Vaccination is considered to be the most effective way to protect grouper from SGIV. In this study, the spores of Bacillus subtilis (B.subtilis) WB600 were utilized as the vehicle that the VP19 protein was displayed on the spores surface. To further investigate the effect of oral vaccination, the grouper were orally immunized with B.s-CotC-19 spores. After challenged, the survival rate of grouper orally vaccinated with B.s-CotC-19 spores was 34.5% and the relative percent survival (RPS) was 28.7% compared to the PBS group. Moreover, the viral load in the tissues of the B.s-CotC-19 group was significantly lower than that of the PBS group. The histopathological sections of head kidney and liver tissue from the B.s-CotC-19 group showed significantly less histopathology compared to the PBS group. In addition, the specific IgM levels in serum in the B.s-CotC-19 group was higher than those in the PBS group. In the hindgut tissue, the immune-related gene expression detected by quantitative real-time PCR (qRT-PCR) exhibited an increasing trend in different degrees in the B.s-CotC-19 group, suggesting that the innate and adaptive immune responses were activated. These results indicated that the oral administration of recombinant B.subtilis spores was effective for preventing SGIV infection. This study provided a feasible strategy for the controlling of fish virus diseases.
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Affiliation(s)
- Xia Liang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Junjia Liang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Jinqiao Cao
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Shijia Liu
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Quan Wang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Yunshang Ning
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Zengjian Liang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Jiaying Zheng
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Zemiao Zhang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Jiayi Luo
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Yingjing Chen
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Xiaohong Huang
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China; College of Marine Sciences, South China Agricultural University, Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266000, China
| | - Yan Huang
- ZhongShan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Qiwei Qin
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China; College of Marine Sciences, South China Agricultural University, Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266000, China.
| | - Sheng Zhou
- College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, China; College of Marine Sciences, South China Agricultural University, Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, China; Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266000, China.
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Gan Z, Cheng J, Hou J, Chen S, Xia H, Xia L, Kwok KWH, Lu Y, Nie P. Tilapia dsRNA-activated protein kinase R (PKR): An interferon-induced antiviral effector with translation inhibition activity. FISH & SHELLFISH IMMUNOLOGY 2021; 112:74-80. [PMID: 33667675 DOI: 10.1016/j.fsi.2021.02.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 02/21/2021] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
The dsRNA-activated protein kinase R (PKR) is one of key antiviral effectors induced by interferons (IFNs), and its functions are largely unknown in tilapia, an important commercial fish species suffering from several viral infectious diseases. In the present study, a PKR gene named On-PKR was identified and cloned from Nile tilapia, Oreochromis niloticus. On-PKR gene was constitutively expressed in all tissues examined, with the highest expression level observed in head kidney and liver, and was rapidly induced in all organs/tissues tested following the stimulation of poly(I:C). Importantly, the expression of On-PKR is induced by group I and group II IFNs with distinct induction kinetics in vivo: group I IFN elicits a relative delayed but sustained induction of On-PKR, whereas group II IFN triggers a rapid and transient expression of On-PKR. Moreover, the overexpression of On-PKR has been proven to inhibit the protein translation and virus replication in fish cells. The present study thus contributes to a better understanding of the functions of antiviral effectors in tilapia, and may provide clues for the prevention and therapy of viral diseases in fish.
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Affiliation(s)
- Zhen Gan
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, And Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Jun Cheng
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, And Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Jing Hou
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China
| | - Shannan Chen
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Hongli Xia
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China
| | - Liqun Xia
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, And Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Kevin W H Kwok
- Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hong Kong, China
| | - Yishan Lu
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, And Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China.
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
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Gan Z, Cheng J, Hou J, Xia L, Lu Y, Nie P. Molecular and functional characterization of interferon regulatory factor 1 (IRF1) in amphibian Xenopus tropicalis. Int J Biol Macromol 2020; 167:719-725. [PMID: 33279564 DOI: 10.1016/j.ijbiomac.2020.11.217] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 11/30/2020] [Accepted: 11/30/2020] [Indexed: 12/14/2022]
Abstract
Interferon regulatory factor 1 (IRF1) is an important regulator in controlling the transcription of type I interferon genes, and its functions have been well-characterized in mammals, birds and fish. However, little information is available regarding the function of amphibian IRF1. In this study, an IRF1 gene homolog named as Xt-IRF1 was identified in the Western clawed frog (Xenopus tropicalis), an amphibian model specie widely used for comparative immunology research. Xt-IRF1 and IRF1 in other vertebrates possess similar genomic structure and flanking genes, and were grouped together to form a separate clade in phylogenetic tree. In addition, Xt-IRF1 gene was constitutively expressed in all tissues examined, with the highest expression level observed in spleen, and was inducible after poly(I:C) stimulation. Importantly, the expression of Xt-IRF1 was markedly induced by recombinant type I interferon, and Xt-IRF1 induced a strong activation of both IFNβ and ISRE promoters. The present study opens the door to investigate the roles of IRF1 in amphibians, and thus contributes to a better understanding of the functional evolution of IRFs in lower tetrapods.
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Affiliation(s)
- Zhen Gan
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; College of Fishery, Guangdong Ocean University, Zhanjiang 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen 518120, China; Shenzhen Dapeng New District Science and Technology Innovation Service Center, Shenzhen 518120, China
| | - Jun Cheng
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen 518120, China
| | - Jing Hou
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; College of Fishery, Guangdong Ocean University, Zhanjiang 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen 518120, China; Shenzhen Dapeng New District Science and Technology Innovation Service Center, Shenzhen 518120, China
| | - Liqun Xia
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen 518120, China
| | - Yishan Lu
- Shenzhen Institute of Guangdong Ocean University, Shenzhen 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen 518120, China.
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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Gan Z, Cheng J, Chen S, Hou J, Li N, Xia H, Xia L, Lu Y, Nie P. Identification and characterization of tilapia CRFB1, CRFB2 and CRFB5 reveals preferential receptor usage of three IFN subtypes in perciform fishes. FISH & SHELLFISH IMMUNOLOGY 2020; 107:194-201. [PMID: 33011433 DOI: 10.1016/j.fsi.2020.10.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 09/26/2020] [Accepted: 10/01/2020] [Indexed: 06/11/2023]
Abstract
Type I interferons are a subset of cytokines playing central roles in host antiviral defense, and their effects depend on the interaction with the heterodimeric receptor complex. Surprisingly, two pairs of the receptor subunits, CRFB1 and CRFB5, and CRFB2 and CRFB5, have been identified in fish, but the studies about preferential receptor usage of different fish IFN subtypes are rather limited. In this study, the three receptor chains of type I IFNs named as On-CRFB1, On-CRFB2 and On-CRFB5 were identified in Nile tilapia, Oreochromis niloticus. These three genes were constitutively expressed in all tissues examined, with the highest expression level observed in muscle and liver, and were rapidly induced in liver following the stimulation of poly(I:C). Interestingly, it is possible that all three subtypes of tilapia IFNs are able to signal through two pairs of the receptor subunits, On-CRFB1 and On-CRFB5, and On-CRFB2 and On-CRFB5. More importantly, tilapia group I IFNs (On-IFNd and On-IFNh) preferentially signal through a receptor complex composed of On-CRFB1 and On-CRFB5, and group II IFNs (On-IFNc) preferentially signal through a receptor complex comprised of On-CRFB2 and On-CRFB5. The present study thus provides new insights into the receptor usage of group I and group II IFNs in fish.
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Affiliation(s)
- Zhen Gan
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China; Shenzhen Dapeng New District Science and Technology Innovation Service Center, Shenzhen, 518120, China
| | - Jun Cheng
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Shannan Chen
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Jing Hou
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China; Shenzhen Dapeng New District Science and Technology Innovation Service Center, Shenzhen, 518120, China
| | - Nan Li
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Hongli Xia
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Liqun Xia
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China
| | - Yishan Lu
- Shenzhen Institute of Guangdong Ocean University, Shenzhen, 518120, China; College of Fishery, Guangdong Ocean University, Zhanjiang, 524025, China; Guangdong Provincial Engineering Research Center for Aquatic Animal Health Assessment, and Shenzhen Public Service Platform for Evaluation of Marine Economic Animal Seedings, Shenzhen, 518120, China.
| | - Pin Nie
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
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Probiotics Modulate Tilapia Resistance and Immune Response against Tilapia Lake Virus Infection. Pathogens 2020; 9:pathogens9110919. [PMID: 33172079 PMCID: PMC7694748 DOI: 10.3390/pathogens9110919] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/25/2020] [Accepted: 11/04/2020] [Indexed: 11/23/2022] Open
Abstract
Tilapia lake virus (TiLV) causes an emerging viral disease associated with high mortality and economic damage in tilapia farming around the world. The use of probiotics in aquaculture has been suggested as an alternative to antibiotics and drugs to reduce the negative impact of bacterial and viral infections. In this study, we investigate the effect of probiotic Bacillus spp. supplementation on mortality, viral load, and expression of immune-related genes in red hybrid tilapia (Oreochromis spp.) upon TiLV infection. Fish were divided into three groups, and fed with: control diet, 0.5% probiotics-supplemented diet, and 1% probiotics-supplemented diet. After 21 days of experimental feeding, the three groups were infected with TiLV and monitored for mortality and growth performances, while organs were sampled at different time points to measure viral load and the transcription modulation of immune response markers. No significant difference was found among the groups in terms of weight gain (WG), average daily gain (ADG), feed efficiency (FE), or feed conversion ratio (FCR). A lower cumulative mortality was retrieved from fish fed 0.5% and 1% probiotics (25% and 24%, respectively), compared to the control group (32%). Moreover, fish fed with 1% probiotic diet had a significantly lower viral load, than those fed with 0.5% probiotic and control diet at 5, 6, 9, and 12 days post infection-challenge (dpc). The expression patterns of immune-related genes, including il-8 (also known as CXCL8), ifn-γ, irf-3, mx, rsad-2 (also known as VIPERIN) showed significant upregulation upon probiotic treatment during the peak of TiLV pathogenesis (between 9 and 12 dpc) and during most of the study period in fish fed with 1% probiotics-supplemented diet. Taken together, these findings indicate that dietary supplementation using Bacillus spp. probiotics may have beneficial effects to strengthen tilapia immunity and resistance against TiLV infections. Therefore, probiotic treatments may be preventively administered to reduce losses caused by this emerging viral infection in tilapia aquaculture.
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