1
|
Divilov K, Merz N, Schoolfield B, Green TJ, Langdon C. Genome-wide allele frequency studies in Pacific oyster families identify candidate genes for tolerance to ostreid herpesvirus 1 (OsHV-1). BMC Genomics 2023; 24:631. [PMID: 37872508 PMCID: PMC10594793 DOI: 10.1186/s12864-023-09744-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 10/14/2023] [Indexed: 10/25/2023] Open
Abstract
BACKGROUND Host genetics influences the development of infectious diseases in many agricultural animal species. Identifying genes associated with disease development has the potential to make selective breeding for disease tolerance more likely to succeed through the selection of different genes in diverse signaling pathways. In this study, four families of Pacific oysters (Crassostrea gigas) were identified to be segregating for a quantitative trait locus (QTL) on chromosome 8. This QTL was previously found to be associated with basal antiviral gene expression and survival to ostreid herpesvirus 1 (OsHV-1) mortality events in Tomales Bay, California. Individuals from these four families were phenotyped and genotyped in an attempt to find candidate genes associated with the QTL on chromosome 8. RESULTS Genome-wide allele frequencies of oysters from each family prior to being planting in Tomales Bay were compared with the allele frequencies of oysters from respective families that survived an OsHV-1 mortality event. Six significant unique QTL were identified in two families in these genome-wide allele frequency studies, all of which were located on chromosome 8. Three QTL were assigned to candidate genes (ABCA1, PIK3R1, and WBP2) that have been previously associated with antiviral innate immunity in vertebrates. CONCLUSION The identification of vertebrate antiviral innate immunity genes as candidate genes involved in molluscan antiviral innate immunity reinforces the similarities between the innate immune systems of these two groups. Causal variant identification in these candidate genes will enable future functional studies of these genes in an effort to better understand their antiviral modes of action.
Collapse
Affiliation(s)
- Konstantin Divilov
- Department of Fisheries, Wildlife, and Conservation Sciences, Coastal Oregon Marine Experiment Station, Oregon State University, Hatfield Marine Science Center, Newport, OR, 97365, USA.
| | - Noah Merz
- Department of Fisheries, Wildlife, and Conservation Sciences, Coastal Oregon Marine Experiment Station, Oregon State University, Hatfield Marine Science Center, Newport, OR, 97365, USA
| | - Blaine Schoolfield
- Department of Fisheries, Wildlife, and Conservation Sciences, Coastal Oregon Marine Experiment Station, Oregon State University, Hatfield Marine Science Center, Newport, OR, 97365, USA
| | - Timothy J Green
- Centre for Shellfish Research, Vancouver Island University, Nanaimo, BC, V9R 5S5, Canada
| | - Chris Langdon
- Department of Fisheries, Wildlife, and Conservation Sciences, Coastal Oregon Marine Experiment Station, Oregon State University, Hatfield Marine Science Center, Newport, OR, 97365, USA
| |
Collapse
|
2
|
Trancart S, Tweedie A, Liu O, Paul-Pont I, Hick P, Houssin M, Whittington RJ. Diversity and molecular epidemiology of Ostreid herpesvirus 1 in farmed Crassostrea gigas in Australia: Geographic clusters and implications for "microvariants" in global mortality events. Virus Res 2023; 323:198994. [PMID: 36332723 PMCID: PMC10194400 DOI: 10.1016/j.virusres.2022.198994] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 10/26/2022] [Accepted: 10/31/2022] [Indexed: 11/08/2022]
Abstract
Since 2010, mass mortality events known as Pacific oyster mortality syndrome (POMS) have occurred in Crassostrea gigas in Australia associated with Ostreid herpesvirus 1. The virus was thought to be an OsHV-1 µVar or "microvariant", i.e. one of the dominant variants associated with POMS in Europe, but there are few data to characterize the genotype in Australia. Consequently, the genetic identity and diversity of the virus was determined to understand the epidemiology of the disease in Australia. Samples were analysed from diseased C. gigas over five summer seasons between 2011 and 2016 in POMS-affected estuaries: Georges River in New South Wales (NSW), Hawkesbury River (NSW) and Pitt Water in Tasmania. Sequencing was attempted for six genomic regions. Numerous variants were identified among these regions (n = 100 isolates) while twelve variants were identified from concatenated nucleotide sequences (n = 61 isolates). Nucleotide diversity of the seven genotypes of C region among Australian isolates (Pi 0.99 × 10-3) was the lowest globally. All Australian isolates grouped in a cluster distinct from other OsHV-1 isolates worldwide. This is the first report that Australian outbreaks of POMS were associated with OsHV-1 distinct from OsHV-1 reference genotype, µVar and other microvariants from other countries. The findings illustrate that microvariants are not the only variants of OsHV-1 associated with mass mortality events in C. gigas. In addition, there was mutually exclusive spatial clustering of viral genomic and amino acid sequence variants between estuaries, and a possible association between genotype/amino acid sequence and the prevalence and severity of POMS, as this differed between these estuaries. The sequencing findings supported prior epidemiological evidence for environmental reservoirs of OsHV-1 for POMS outbreaks in Australia.
Collapse
Affiliation(s)
- Suzanne Trancart
- LABÉO Research Department, 1 Route de Rosel, Cedex 4, Caen 14053, France
| | - Alison Tweedie
- The University of Sydney, Sydney School of Veterinary Science, Faculty of Science, 425 Werombi Rd, Camden, NSW 2570, Australia; Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia
| | - Olivia Liu
- The University of Sydney, Sydney School of Veterinary Science, Faculty of Science, 425 Werombi Rd, Camden, NSW 2570, Australia; Department of Agriculture, Water and the Environment, Canberra, ACT 2601, Australia
| | - Ika Paul-Pont
- The University of Sydney, Sydney School of Veterinary Science, Faculty of Science, 425 Werombi Rd, Camden, NSW 2570, Australia; LEMAR, Rue Dumont d'Urville, Plouzané 29280, France
| | - Paul Hick
- The University of Sydney, Sydney School of Veterinary Science, Faculty of Science, 425 Werombi Rd, Camden, NSW 2570, Australia; Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia
| | - Maryline Houssin
- LABÉO Research Department, 1 Route de Rosel, Cedex 4, Caen 14053, France; UMR BOREA Université de Caen Normandie, MNHN, CNRS 8067, SU, IRD 207, UCN, UA, Esplanade de la Paix Caen Cedex 4 14032, France
| | - Richard J Whittington
- The University of Sydney, Sydney School of Veterinary Science, Faculty of Science, 425 Werombi Rd, Camden, NSW 2570, Australia.
| |
Collapse
|
3
|
Delisle L, Rolton A, Vignier J. Inactivated ostreid herpesvirus-1 induces an innate immune response in the Pacific oyster, Crassostrea gigas, hemocytes. Front Immunol 2023; 14:1161145. [PMID: 37187746 PMCID: PMC10175643 DOI: 10.3389/fimmu.2023.1161145] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/18/2023] [Indexed: 05/17/2023] Open
Abstract
Infectious diseases are a major constraint to the expansion of shellfish production worldwide. Pacific oyster mortality syndrome (POMS), a polymicrobial disease triggered by the Ostreid herpesvirus-1 (OsHV-1), has devastated the global Pacific oyster (Crassostrea gigas) aquaculture industry. Recent ground-breaking research revealed that C. gigas possess an immune memory, capable of adaption, which improves the immune response upon a second exposure to a pathogen. This paradigm shift opens the door for developing 'vaccines' to improve shellfish survival during disease outbreaks. In the present study, we developed an in-vitro assay using hemocytes - the main effectors of the C. gigas immune system - collected from juvenile oysters susceptible to OsHV-1. The potency of multiple antigen preparations (e.g., chemically and physically inactivated OsHV-1, viral DNA, and protein extracts) to stimulate an immune response in hemocytes was evaluated using flow cytometry and droplet digital PCR to measure immune-related subcellular functions and gene expression, respectively. The immune response to the different antigens was benchmarked against that of hemocytes treated with Poly (I:C). We identified 10 antigen preparations capable of inducing immune stimulation in hemocytes (ROS production and positively expressed immune- related genes) after 1 h of exposure, without causing cytotoxicity. These findings are significant, as they evidence the potential for priming the innate immunity of oysters using viral antigens, which may enable cost-effective therapeutic treatment to mitigate OsHV-1/POMS. Further testing of these antigen preparations using an in-vivo infection model is essential to validate promising candidate pseudo-vaccines.
Collapse
Affiliation(s)
- Lizenn Delisle
- Biosecurity Group, Cawthron Institute, Nelson, New Zealand
- *Correspondence: Lizenn Delisle, ; Anne Rolton,
| | - Anne Rolton
- Biosecurity Group, Cawthron Institute, Nelson, New Zealand
- *Correspondence: Lizenn Delisle, ; Anne Rolton,
| | - Julien Vignier
- Aquaculture Group, Cawthron Institute, Nelson, New Zealand
| |
Collapse
|
4
|
Delisle L, Laroche O, Hilton Z, Burguin JF, Rolton A, Berry J, Pochon X, Boudry P, Vignier J. Understanding the Dynamic of POMS Infection and the Role of Microbiota Composition in the Survival of Pacific Oysters, Crassostrea gigas. Microbiol Spectr 2022; 10:e0195922. [PMID: 36314927 PMCID: PMC9769987 DOI: 10.1128/spectrum.01959-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 09/16/2022] [Indexed: 11/07/2022] Open
Abstract
For over a decade, Pacific oyster mortality syndrome (POMS), a polymicrobial disease, induced recurring episodes of massive mortality affecting Crassostrea gigas oysters worldwide. Recent studies evidenced a combined infection of the ostreid herpesvirus (OsHV-1 μVar) and opportunistic bacteria in affected oysters. However, the role of the oyster microbiota in POMS is not fully understood. While some bacteria can protect hosts from infection, even minor changes to the microbial communities may also facilitate infection and worsen disease severity. Using a laboratory-based experimental infection model, we challenged juveniles from 10 biparental oyster families with previously established contrasted genetically based ability to survive POMS in the field. Combining molecular analyses and 16S rRNA gene sequencing with histopathological observations, we described the temporal kinetics of POMS and characterized the changes in microbiota during infection. By associating the microbiota composition with oyster mortality rate, viral load, and viral gene expression, we were able to identify both potentially harmful and beneficial bacterial amplicon sequence variants (ASVs). We also observed a delay in viral infection resulting in a later onset of mortality in oysters compared to previous observations and a lack of evidence of fatal dysbiosis in infected oysters. Overall, these results provide new insights into how the oyster microbiome may influence POMS disease outcomes and open new perspectives on the use of microbiome composition as a complementary screening tool to determine shellfish health and potentially predict oyster vulnerability to POMS. IMPORTANCE For more than a decade, Pacific oyster mortality syndrome (POMS) has severely impacted the Crassostrea gigas aquaculture industry, at times killing up to 100% of young farmed Pacific oysters, a key commercial species that is cultivated globally. These disease outbreaks have caused major financial losses for the oyster aquaculture industry. Selective breeding has improved disease resistance in oysters, but some levels of mortality persist, and additional knowledge of the disease progression and pathogenicity is needed to develop complementary mitigation strategies. In this holistic study, we identified some potentially harmful and beneficial bacteria that can influence the outcome of the disease. These results will contribute to advance disease management and aquaculture practices by improving our understanding of the mechanisms behind genetic resistance to POMS and assisting in predicting oyster vulnerability to POMS.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Xavier Pochon
- Cawthron Institute, Nelson, New Zealand
- Institute of Marine Science, University of Auckland, Warkworth, New Zealand
| | - Pierre Boudry
- Département Ressources Biologiques et Environnement, Ifremer, ZI de la pointe du diable, Plouzané, France
| | | |
Collapse
|