Evaluation of immune effects of virus-like particles of recombinant GII. 17 norovirus

Abstract

Objective To evaluate the immune effects of virus-like particles (VLPs) assembled from the capsid protein VP1 of a recombinant norovirus (NoV) GⅡ.17 genotype. Methods The recombinant NoV GⅡ.17 VP1 VLPs were purified, and then tested by SDS-PAGE and Western blot to analyze the purity. The size, morphology and diameter distribution of the recombinant VLPs were detected by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyzer. The recombinant VP1 VLPs adsorbed by aluminium adjuvant were used to immunize BALB/c mice. Serum samples were collected after immunization. Specific antibody level and neutralizing antibody activity were evaluated with enzyme linked immunosorbent assay (ELISA) and histo-blood group antigen (HBGA)-VLP blocking test. Cross-reactivity of serum samples with GⅠ.1 and GⅡ.4 VP1 VLPs were detected. Moreover, cross-protection against GⅠ.1 and GⅡ.4 VP1 VLPs was analyzed. Results The purity of the recombinant NoV GⅡ.17 VP1 VLP was greater than 90% and specific bands were detected by Western blot. TEM images and DLS experiments showed that VLPs were 30-50 nm in size with good morphology and uniformity, indicating that the recombinant VLPs were similar to the wildtype virus. High titers of specific antibodies were detected in serum samples of the immunized mice. A certain degree of cross-reactions between serum samples and VP1 VLPs of NoV GⅠ.1 and GⅡ.4 were observed, but no cross-protection was detected. Conclusion The recombinant GⅡ. 17 VP1 VLPs in combination with aluminum adjuvant can induce higher titers of HBGA blocking antibodies in mice, suggesting that it could be used as a candidate target antigen for norovirus vaccine. Key words: Norovirus (NoV); GⅡ.17 genotype; Virus like particles (VLPs); Histo-blood group antigen (HBGA)