Infections by the parasitic Haplosporidian Bonamia ostreae have devastated European flat oyster, Ostrea edulis, populations, posing an ongoing threat to aquaculture and restoration efforts today. Understanding the mechanisms of host-parasite interactions is therefore critical for developing effective management strategies that support oyster restoration, promote sustainable aquaculture, and inform marine policy. This study aimed to establish an in vitro model to investigate the effects of B. ostreae on oyster physiology, with a particular focus on heart function.
A novel co-culture system was developed using heart tissue from previously infected oysters to preserve both the integrity and infection status of whole hearts in vitro (Fig 1A). Uninfected hearts remained viable and continued contracting in vitro for up to nine months, while hearts infected with B. ostreae maintained the parasite in co-culture for over three months (Fig 1B). This system allowed for the assessment of the impact of B. ostreae on heart function, revealing a significant increase in resting heart rate in infected cultures. Furthermore, early histological analysis with Hemacolor indicated that Bonamia is likely replicating in culture, evidenced by the presence of double-nucleated parasites (Fig 1B). Moreover, preliminary metabolomic, and proteomic analyses offer insights into the broader physiological changes triggered by the infection, suggesting complex interactions between the parasite and host in vitro.
To our knowledge, this is the first study to successfully maintain B. ostreae in vitro for an extended period, offering a reliable platform to investigate the host-pathogen interactions in O. edulis at both cellular and organ levels. Future work will focus on further characterizing the molecular changes and exploring potential interventions to mitigate the impact of B. ostreae on oyster populations.