In vivo white spot syndrome virus (WSSV) infection models are indispensable tools to support the development of antiviral therapies and immunomodulators against white spot disease (WSD) . Still, the selection of the most appropriate models for anti-WSSV product development is typically not straightforward. The objective of this review was to further elaborate on this subject to provide investigators with solid arguments for or against the selection of certain types of WSSV infection models in specific research contexts.
A review was conducted by retrieving literature from searches of computerized databases, hand searches, and authoritative texts with the overarching purpose to synthesize the existing literature in the field (Sargeant & O’Connor, 2020).
To determine if anti-WSSV product candidates have virucidal properties, it is advisable to carry out in vivo antiviral activity tests. M ultiple product candidates can be screened in parallel, which reduces the costs and the time spent in development. Since immunomodulators target the host rather than the virus, antiviral activity testing is not applicable. Both for antiviral and immunomodulators product candidates, it is recommended to test in vivo if the chosen delivery method manages to deliver a sufficient concentration of the active substance to intended site(s) of action. Next , the efficacy of the product candidate can be tested during in vivo infection experiments. An inoculation procedure that resembles natural infection (immersion, feeding of WSSV-infected tissues) is expected to help translate study results to the field . Housing shrimp individually instead of in groups when the delivery methods and the efficacy of the therapy still need to be established, is advised , because individuals can easily be monitored and sampled. The evaluation of the product candidate’s protective properties against WSSV can be based on clinical observations (survival rates and pathogen counts ), or additional health parameters that can be evaluated through the model and/or additional laboratory tests. At a later development stage, it is more beneficial for the extrapolation of the results to house shrimp in groups instead of individually . This facilitates natural transmission between hosts, which mimics the situation in the field , but in a laboratory setting the biotic and abiotic parameters can still be controlled . It is therefore recommended to test the product candidates in these controlled conditions, before proceeding to assess their effectiveness under ‘real-world’ conditions in field studies on farms.
This research received funding from Flanders Innovation and Entrepreneurship (Belgium).
Reference:
Sargeant, J. M., et al., (2020). Front. vet. sci. , 7, 502756.