Abstract
In this study, four experimental assays were conducted to evaluate the use of a new silver nanoparticle formulation named Argovit-4, which was prepared with slight modifications to enhance its biological activity against white spot syndrome virus (WSSV) in shrimp culture. The goals of these assays were to (1) determine the protective effect of Argovit-4 against WSSV, (2) determine whether Argovit-4 supplemented in feed exhibits toxicity towards shrimp, (3) determine whether Argovit-4 as antiviral additive in feed can prevent or delay/reduce WSSV-induced shrimp mortality, and (4) determine whether Argovit-4 supplemented in feed alters the early stages of the shrimp immune response. In bioassay 1, several viral inocula calibrated at 7 SID50(shrimp infectious doses 50% endpoint) were exposed to 40, 100, 200 and 1,000 ng/SID50 of Ag+ and then intramuscularly injected into shrimp for 96 h. In bioassay 2, shrimp were fed Argovit-4 supplemented in feed at different concentrations (10, 100 and 1,000 µg per gram of feed) for 192 h. In bioassay 3, shrimp were treated with Argovit-4 supplemented in feed at different concentrations and then challenged against WSSV for 192 h. In bioassay 4, quantitative real-time RT-qPCR was performed to measure the transcriptional responses of five immune-relevant genes in haemocytes of experimental shrimp treated with Argovit-4 supplemented in feed at 0, 6, 12, 24 and 48 h. The intramuscularly injected Argovit-4 showed a dose-dependent effect (p < 0.05) on the cumulative shrimp mortality from 0–96 h post-infection. In the second bioassay, shrimp fed Argovit-4 supplemented in feed did not show signs of toxicity for the assayed doses over the 192-h experiment. The third and fourth bioassays showed that shrimp challenged with WSSV at 1,000 µg/g feed exhibited reduced mortality without altering the expression of some immune system-related genes according to the observed level of transcriptional. This study is the first show that the new Argovit-4 formulation has potential as an antiviral additive in feed against WSSV and demonstrates a practical therapeutic strategy to control WSSV and possibly other invertebrate pathogens in shrimp aquaculture.
Highlights
The white spot syndrome virus (WSSV) is highly aggressive towards shrimp aquaculture worldwide, for which several studies have attempted to develop a treatment (Álvarez Sánchez et al, 2018)
The three assayed doses of WSSV resulted in 100% shrimp mortality at different time intervals
In the shrimp group infected with 7 SID50, mortality began after 36 hpi with values above 13%, reaching 100% at 72 hpi
Summary
The white spot syndrome virus (WSSV) is highly aggressive towards shrimp aquaculture worldwide, for which several studies have attempted to develop a treatment (Álvarez Sánchez et al, 2018). Nanotechnology has attracted a great deal of attention as an emerging field of research and technological development that open the possibility of handling material at the nanometric level, with dimensions between 1 and 100 nm (Meneses-Márquez et al, 2018). In this size range, nanoparticles show new physical and chemical properties that can be used in different scientific areas for the unprecedented study of phenomena that occur at the atomic and molecular level (Parveen, Misra & Sahoo, 2012; Esmaeillou et al, 2017). Several in vitro studies have demonstrated the effect of AgNPs as an antiviral alternative against human viruses, including human immunodeficiency virus (Elechiguerra et al, 2005; Lara et al, 2010), H1N1 influenza A virus (Mori et al, 2013), monkeypox virus (Rogers et al, 2008), Tacaribe virus (Speshock et al, 2010), hepatitis B virus (Lu et al, 2008) and herpes simplex virus (Baram-Pinto et al, 2009)
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