Study On Influenza NP Vaccine Based On Baculovirus Surface-Display Technology

NP protein of influenza virus is highly conserved and type-specific. NP can trigger strong cell-mediated immune responses in host and is involved in the protection against the challenges with different subtype influenza viruses. Here, NP of an avian H5N1isolate (A/Hubei/1/2010, HB) was expressed by baculovirus surface-display technology and its immunogenicity as well as protective mechanism was investigated.NP gene of HB virus was obtained by use of RT-PCR and cloned into pFastBacDual vector. The recombinant virus NP-Bac was obtained by shult vetor and Bac-to-Bac baculovirus expression system. The NP expression and its distribution on baculovirus surface were identified by western blot and immunolabeled electron microscopy, respectively. Then, the immunogenicity of NP-Bac and its related mechanism were studied in mice infection model.Western blot and immunolabeled electron microscopy assay showed NP protein has been displayed on baculovirus surface. ELISA results show NP protein can induce high level of anti-NP IgG in the sera from NP-Bac-inoculated mice. Four peptides (Pep7:NP49-66LSDYEGRLIQNSITIERM; Pep8:NP57-74IQNSITIERMVLSAFDER; Pep55:NP433-450:TEGRTSDMRTEIIKMMES and Pep56:NP441-458RTEIIKMMESARPEDLSF) were identified by IFN-γ ELISPOT assay. NP57-66IQNSITIERM-, NP441-450RTEIIKMMES-specific T cell responses in vaccinated BALB/c mice was confirmed by FACS. Furthermore, NP protein could be able to trigger the activation of CD4+and CD8+T, and the response of CD8+T is more predominant. The challenge study of mice-adapted virus A/PR/8/34(H1N1) showed that NP-Bac can reduce viral load and attenuate the damage to lung tissue.50%protection ration against the virus could be detected.The NP protein displayed on baculovirus surface in our study can elecit humoral and cell-mediated immune responses in mice and provides protections against different subtype influenza virus infection via reducing viral load.