Haliotid herpesvirus (HaHV-1) and Ostreid herpesvirus (OsHV-1) infect economically important species of abalone and oysters respectively, causing significant production losses worldwide. Our understanding of the molluscan immune system, especially that of the abalone, remains in its infancy and further understanding of these antiviral immune responses is required to develop successful antiviral strategies against herpesvirus infections in molluscs.
Only recently, abalone draft genomes for some species have become available, with the first now available for the economically important Australian greenlip abalone (Haliotis laevigata). Through gene mining strategies and domain database analysis, we now have a putative representation of the potential key players involved in the greenlip abalone immune response in comparison to the oyster (Crassostrea gigas). We highlight that these immune counterparts, mainly from the TLR, cytosolic RNA and DNA and RNA interference signalling pathways are divergent between the two molluscan species, with that of the oyster closely reflecting those of the mammalian immune response. Interestingly, we have identified that the key downstream counterpart of the dsDNA sensing pathway, STING is absent in the greenlip abalone, as well as in a transcriptome assembly for the Australian blacklip abalone, however, it was present in the genomes of the oyster and two additional abalone species (Haliotis rufescens, Haliotis discus hannai). We hypothesise that this may reflect the species’ variable susceptibility to HaHV-1 challenge in vivo, however further work needs to be performed to determine this. Furthermore, this putative analysis has since informed our current experimental immune priming strategies to prevent HaHV-1 infection in blacklip (H. rubra) x greenlip (H. laevigata) hybrid abalone, as has previously and successfully been shown in oysters against OsHV-1.
This work provides a better understanding of the key features of the abalone antiviral innate immune system, providing key information towards the development of immune priming strategies in these animals.