Laboratory in vitro replication of Ostreid Herpes Virus (OsHV-1) using Pacific oyster tissue explants

Pacific oysters (Crassostrea or Magallana gigas) are one of the most economically important aquaculture species globally. Over the past two decades, ostreid herpesvirus (OsHV-1), has become a major pathogen of cultured Pacific oysters resulting in widespread mortality with a global distribution. Experimental use of OsHV-1 is challenging for many reasons, including both complexity and relative obscurity of host pathogen dynamics, and a lack of functioning model systems. The goal of this study was to improve the tools available for working with OsHV-1 in both whole animals and in tissue explants established ex vivo from oysters and maintained in controlled laboratory conditions. Tissue explants were taken from oysters originating from two different sources that have different levels of mortality in OsHV-1 challenges and were used in disease challenges alongside whole animals for comparison. Quantitative PCR, histology and electron microscopy were used to confirm that the explants were capable of replicating OsHV-1. Furthermore, the quantitative PCR results suggests that the source of the oysters was significant in determining the outcome of infection in the explants, supporting the validity of the explant model for OsHV-1 infection. This approach for studying OsHV-1 allows for the control of confounding factors in disease outcome that is not possible in whole animal challenges, providing a new tool for studying OsHV-1 in Pacific oysters.