White Spot Syndrome Virus (WSSV) is an enveloped DNA virus that affects farmed shrimp. WSSV has a 100% mortality rate in farmed shrimp but is naturally present in nearly all wild crustaceans. Shrimp, like other invertebrates, lack an adaptive immune system. In nature, they rely on natural or environmental immune responses to protect them from these pathogens. The lack of some or all of these innate immune responses in the ontrolled aquaculture environments possibly explains why aquaculture shrimp are so susceptible to WSSV.
Vaccination would be the ideal response to this threat to cultured shrimp, but without an adaptive immune response, the shrimps’ muscle fibers would need to be continuously exposed to a protein-based vaccine. Researchers have designed a DNA construct vaccine that would innoculate aquacultured shrimp from WSSV, but have had to develop a novel delivery system since injecting every with shrimp protein-based vaccines on a continual basis would be economically and physically impractical. The DNA construct vaccine causes the shrimp to produce immunologic proteins that protect the shrimp from WSSV for up to 7 weeks per application. To deliver this DNA construct, scientists have developed and tested a chitosan-nanoparticle delivery vehicle aquaculturists can use to administer the vaccine to the shrimp orally. Researchers have proven this novel vaccine and delivery system to work in cultured tiger shrimp with relative survival rates of up to 85% after scientists administered the vaccine.
When these chitosan nanocapsules are released into the aquaculture environment, an ultrasound mechanism is used to break the capsules, releasing the short-strand DNA. The water soluble DNA is absorbed into the intestinal tract of the shrimp where it migrates to the animals’ lymphatic system.
- . Nanotechnology: A Novel Tool for Aquaculture and Fisheries Development. A Prospective Mini-Review. Fisheries and Aquaculture Journal [Internet]. Submitted ;2011(FAJ-16). Available from: http://astonjournals.com/manuscripts/Vol2011/FAJ-16_Vol2011.pdf
- . Oral delivery of DNA construct using chitosan nanoparticles to protect the shrimp from white spot syndrome virus (WSSV). Fish & Shellfish Immunology. 2009 ;26(3):429 - 437.
The potential benefit of this technology is to improve resource efficiency in shrimp aquaculture while improving food security.
Although the risks associated with genetically modified organisms are a hotly debated and contested topic, The researchers that developed this vaccine claim the in vivo and in-vitro toxicity of the chitosan nanoparticles and short strand DNA are low. In research conducted relating directly to this nano-application, the toxicity of the particle and DNA on living cells was below 10%. The risk of cell death is present, but low. The mutative effect of this particular DNA strand has not been studied extensively; presenting risk uncertainties. Additionally, the risks associated with release of this DNA into uncontrolled environments such as lakes, streams, and rivers has not been studied. More research is necessary to determine the ecological and environmental safety of shrimp food containing DNA constructs encapsulated in chitosan nanoparticles.