title: Resistance of Black-lip learl oyster, Pinctada margaritifera, to infection by Ostreid herpes virus 1μvar under experimental challenge may be mediated by humoral antiviral activity.
abstract: Ostreid herpesvirus 1 (OsHV-1) has induced mass mortalities of the larvae and spat of Pacific oysters, Crassostrea gigas, in Europe and, more recently, in Oceania. The production of pearls from the Black-lip pearl oyster, Pinctada margaritifera, represents the second largest source of income to the economies of French Polynesia and many Pacific Island nations that could be severely compromised in the event of a disease outbreak. Coincidentally with the occurrence of OsHV-1 in the southern hemisphere, C. gigas imported from New Zealand and France into French Polynesia tested positive for OsHV-1. Although interspecies viral transmission has been demonstrated, the transmissibility of OsHV-1 to P. margaritifera is unknown. We investigated the susceptibility of juvenile P. margaritifera to OsHV-1 μvar that were injected with tissue homogenates sourced from either naturally infected or healthy C. gigas. The infection challenge lasted 14 days post-injection (dpi) with sampling at 0, 1, 2, 3, 5, 7 and 14 days. Mortality rate, viral prevalence, and cellular immune responses in experimental animals were determined. Tissues were screened by light microscopy and TEM. Pacific oysters were also challenged and used as a positive control to validate the efficiency of OsHV-1 μvar infection. Viral particles and features such as marginated chromatin and highly electron dense nuclei were observed in C. gigas but not in P. margaritifera. Mortality rates and hemocyte immune parameters, including phagocytosis and respiratory burst, were similar between challenged and control P. margaritifera. Herpesvirus-inhibiting activity was demonstrated in the acellular fraction of the hemolymph from P. margaritifera, suggesting that the humoral immunity is critical in the defence against herpesvirus in pearl oysters. Overall, these results suggest that under the conditions of the experimental challenge, P. margaritifera was not sensitive to OsHV-1 μvar and was not an effective host/carrier. The nature and spectrum of activity of the humoral antiviral activity is worthy of further investigation.
authors.affiliation: The University of Queensland, School of Biological Sciences and Centre for Marine Science, Brisbane, Queensland 4072, Australia.
authors.forename: Terence L S
authors.initials: TL
authors.lastname: Tan
authors.affiliation: The University of Sydney, Faculty of Veterinary Science, Camden, New South Wales 2570, Australia.
authors.forename: Ika
authors.initials: I
authors.lastname: Paul-Pont
authors.affiliation: The University of Sydney, Faculty of Veterinary Science, Camden, New South Wales 2570, Australia.
authors.forename: Olivia M
authors.initials: OM
authors.lastname: Evans
authors.affiliation: Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Watterson
authors.affiliation: Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
authors.forename: Paul
authors.initials: P
authors.lastname: Young
authors.affiliation: The University of Sydney, Faculty of Veterinary Science, Camden, New South Wales 2570, Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Whittington
authors.affiliation: Direction des Ressources Marines, Papeete, French Polynesia.
authors.forename: Angelique
authors.initials: A
authors.lastname: Fougerouse
authors.affiliation: Direction des Ressources Marines, Papeete, French Polynesia.
authors.forename: Hervé
authors.initials: H
authors.lastname: Bichet
authors.affiliation: The University of Queensland, School of Biological Sciences and Centre for Marine Science, Brisbane, Queensland 4072, Australia. Electronic address: a.barnes@uq.edu.au.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Barnes
authors.affiliation: The University of Queensland, School of Biological Sciences and Centre for Marine Science, Brisbane, Queensland 4072, Australia.
authors.forename: Cécile
authors.initials: C
authors.lastname: Dang
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D060467:Disease Resistance / Q000276:immunology*; D006434:Hemocytes / Q000166:cytology / Q000502:physiology; D006564:Herpesviridae / Q000254:growth & development / Q000502:physiology*; D056724:Immunity, Humoral; D010587:Phagocytosis; D049911:Pinctada / Q000276:immunology* / Q000821:virology*; D014709:Vero Cells; D010948:Viral Plaque Assay
keywords: Hemocytes; Herpes; Humoral immunity; Ostreid herpesvirus; Pinctada