Abstract:
Swine influenza virus (SIV) is an important viral pathogen in pig
populations. However, commercial vaccines cannot provide complete
protection with induced humoral immunity only and require frequent
updates to fight against current isolates. DNA vaccination is an effective
means of eliciting both arms of immune system, humoral and cellular
immune responses. In this study, DNA vector pcDNA3.1 was inserted with
a chimeric intron downstream of the CMV promoter region followed by a
Kozak sequence to enhance the expression of gene inserts. The C-terminal of VP22 gene (VP22c), encoding the
tegument protein of bovine herpesvirus-1, was fused separately to the N-terminal of four quadruplicated epitopes,
two B-cell epitopes (HA and M2e)) and two T-cell epitopes (NP1 and NP2), which were conserved at least among
H1 SIV isolates. Linkers-KK– was used to space between each copy of the two B-cell epitopes and –RVKR– was
used for the two T-cell epitopes in order to enhance the presentation of epitopes to the immune system. The
expression of epitopes was confirmed in in vitro transfection of 293FT cells and higher numbers of epitope-positive
cells were achieved from those containing VP22c than those without. After the DNA plasmids were administered
to mice intramuscularly in combination or separately, or boosted with recombinant proteins of quadruplicated
epitopes fused to VP22c, the vaccine stimulated desired epitope-specific humoral immunity to the two B-cell
epitopes and cellular immunity to the epitope NP380-393. Our results indicate that the DNA vaccines with quadruplicated
epitopes fused to the VP22c may be a potential strategy in developing universal vaccines against SIV.
Huiling Wei’s research project won the American College of Veterinary Microbiologists award at the Conference for
Research Workers in Animal Disease annual meeting in Chicago, December, 2011.