Abstract
DNA vaccines had been widely used in animal models against various viral infections, while it was not so convincing for many infectious diseases especially bacterial disease in aquaculture. Interleukin-8(IL-8) as one of the CXC chemokines, its immunological role and adjuvant potential which had been proved in mammals were rarely reported in fish species. In this study, recombination plasmid pcDNA3.1/IL-8(pcIL-8) was conducted and the capacity of IL-8 as molecular adjuvant was explored from several aspects by co-injecting with a DNA vaccine encoding a-enolase(pcENO) against Streptococcus iniae infection in channel catfish. The results suggested that co-injection of pcIL-8 with DNA vaccine increased the innate immunity and specific antibody levels, as well as increased the immune-related genes involving in pro-inflammatory response, humoral and cellular immunity. Moreover, pcIL-8 enhanced the immunoprotection of pcENO with the relative percent survival(RPS) of 60% to 80% against S.iniae infection at 4 week post vaccination(p.v.), with the significantly higher RPS of 73.33% in pcENO+pcIL-8 group compared with that of pcENO alone(53.33%) at challenge test of 8 weeks p.v. Taken together, these results indicate pcIL-8 as a molecular adjuvant co-injected with DNA vaccine not only improves the immunoprotection but also maintains long period of immunity for channel catfish against S.iniae infection. Our study signifies that IL-8 holds promise to serve as a potential adjuvant in DNA vaccines against bacterial infections for long time.
Highlights
Aquaculture as one of the most vibrant sector of the global food system has shown a rapid growth in the last decades and with such growth comes the need for effective control measures against increasingly diseases
We further explore the adjuvant potential of IL-8 of channel catfish from several aspects by co-injecting with a DNA vaccine encoding α-enolase against Streptococcus iniae infection based on our previous report that IL-8 hold promise for use as potential immunopotentiator against bacterial infections but insufficient to extend the immune protection for long time in a subunit vaccine model [21]
On the basis of our previous report, we have further explored the capacity of IL-8 as molecular adjuvant by co-injecting with a DNA vaccine against S. iniae infection in channel catfish
Summary
Aquaculture as one of the most vibrant sector of the global food system has shown a rapid growth in the last decades and with such growth comes the need for effective control measures against increasingly diseases. Controlling the disease and infection in aquaculture relies mainly on the use of antibiotics and antimicrobial compounds. Compared with traditional inactivated and attenuated live vaccines, DNA vaccines consisting of naked plasmid DNA that will result in gene expression of immunoprotective antigen in vivo against fish diseases viral pathogens, have made major advances over the last decade and become one of the most promising vaccine preparations in aquaculture [1]. Despite DNA www.impactjournals.com/oncotarget vaccines used in fish have proven efficacious against some viral diseases [2,3,4,5,6,7], only one DNA vaccine for aquaculture fish has been licensed for sale [8], and it is not so convincing for a number of other viral infections and bacterial disease. Scientists are focused on improving and increasing the potency of DNA vaccines, which include the improvements of vectors and the covaccination of molecular adjuvants such as cytokines with the antigen to enhance the immune responses [9, 10]
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