Evaluation of immune effects of recombinant norovirus GI.1 and GII.4 virus-like particles

Objective To evaluate the immune effects of virus-like particles (VLPs) of VP1 proteins derived from norovirus GⅠ.1 and GⅡ.4 genotypes expressed in Hansenula polymorpha expression system. Methods SDS-PAGE and Western blot assay were performed to detect the purity of GⅠ.1 and GⅡ.4 VP1 proteins after purification. Morphologies of the recombinant VLPs were observed under transmission electron microscopy (TEM). Sizes and distributions of the VLPs were analyzed by dynamic light scattering analyzer. BT50 (50% of blocking titer) was detected by HBGA (histo-blood group antigen) blocking assay in BALB/c mice immunized with different regimens. Results SDS-PAGE analysis of the purified recombinant GⅠ.1 and GⅡ.4 VP1 proteins showed that their purity were greater than 90%. Western blot assay confirmed the specific bands of VLPs. TEM images showed that the sizes of purified GⅠ.1 and GⅡ.4 VP1 VLPs were at a mean diameter of 30-50 nm with clear border and high homogeneity, which was similar to that of wild virus. BT50 significantly increased in the groups, in which Al(OH)3 was used as adjuvant. Conclusion Animal studies have shown that administration of GⅠ.1 and GⅡ.4 VP1 VLPs in the presence of Al(OH)3 induces detectable HBGA-blocking antibody, indicating that GⅠ.1 and GⅡ.4 VP1 VLPs are promising candidates for norovirus vaccine. Key words: Norovirus (NoV); Virus-like particles (VLPs); Histo-blood group antigen (HBGA)