HaHV-1 is a re-emerging viral pathogen characterised by mass mortality events in wild and farmed Australian abalone, with no current treatment options. This project sought to examine whether immune priming could protect abalone from lethal HaHV-1 exposure and if this protection is transgenerational.
Naive abalone of alternate ages and species were exposed to HaHV-1 via immersion in infectious water. Real-time PCR was utilised to detect both HaHV-1 in nerves and track immune response genes in haemocytes. Immune priming was performed via injection of abalone with non-specific synthetic nucleic acid or protein, prior to HaHV‑1 infection or spawning.
Following optimisation of immune primers and their delivery methods, we established that primers directly administered to abalone at least 5 days prior to infection, provided complete protection against lethal HaHV-1 challenge. Protection lasted at least 121 days and was associated with the transcriptional upregulation of antiviral interferon stimulated genes in abalone haemolymph. In collaboration with 3 Victorian abalone farms and to explore if this protection was transgenerational, female abalone (greenlip and blacklip) were primed between 3 days and 8 weeks prior to spawning to produce blacklip, greenlip and hybrid progeny. The progeny was challenged with HaHV-1 at both 6 and 12-months of age and although it was clear that transgenerational immune priming was not protective, juvenile abalone (<1yo) were found to be significantly less susceptible to HaHV-1 infection when compared to older abalone. This contrasts from what is known in respect to oyster herpesvirus (OsHV-1) infection and our work has therefore added crucial knowledge into the currently poorly understood HaHV-1 field.
This work provides the first insight into a protection strategy against HaHV-1 in collaboration with the Australian abalone industry and informs our current research involving the development of a feed and immersion immune priming approach against HaHV-1 in large-scale aquacultural settings.