Expression of H3N2 nucleoprotein in maize seeds and immunogenicity in mice
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Oral administration of maize-expressed H3N2 nucleoprotein induced antibody responses in mice showing the immunogenicity of plant-derived antigen and its potential to be utilized as a universal flu vaccine.
Influenza A viruses cause influenza epidemics that are devastating to humans and livestock. The vaccine for influenza needs to be reformulated every year to match the circulating strains due to virus mutation. Influenza virus nucleoprotein (NP) is a multifunctional RNA-binding protein that is highly conserved among strains, making it a potential candidate for a universal vaccine. In this study, the NP gene of H3N2 swine origin influenza virus was expressed in maize endosperm. Twelve transgenic maize lines were generated and analyzed for recombinant NP (rNP) expression. Transcript analysis showed the main accumulation of rNP in seed. Protein level of rNP in T1 transgenic maize seeds ranged from 8.0 to 35 µg of NP/g of corn seed. The level increased up to 70 µg of NP/g in T3 seeds. A mouse study was performed to test the immunogenicity of one line of maize-derived rNP (MNP). Mice were immunized with MNP in a prime-boost design. Oral gavage administration showed that a humoral immune response was elicited in the mice treated with MNP indicating the immunogenicity of MNP. NP-specific antibody responses in the MNP group showed comparable antibody titer with the groups receiving positive controls such as Vero cell-derived NP (VNP) or alphavirus replicon particle-derived NP (ANP). Cytokine analysis showed antigen-specific stimulation of IL-4 cytokine elicited in splenocytes from mice treated with MNP further confirming a TH2 humoral immune response induced by MNP administration.
KeywordsNucleoprotein H3N2 Plant-based vaccine Antigens Transgenic maize
HN and KW thank Meaghan Nelson and Pam Whitson for their technical assistance in animal experiment, Dr. Ryan Vander Veen for providing H3N2 NP gene cassette and technical assistance in the experiment, and Dr. Hank Harris for his expertise in vaccines and initial scientific discussion. This work was supported in part by the U.S. Department of Agriculture National Institute of Food and Agriculture (Hatch Project No. IOW05162), the Plant Sciences Institute of Iowa State University and Charoen Pokphand Indonesia.
Conflict of interest
HN, BB, JC and KW declare that they have no conflict of interest. MM is an employee of Harrisvaccines, Inc., which provided materials and expertise for the work. However, this does not alter the author’s adherence to all the Plant Cell Reports policies on sharing data and materials.
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