Construction and immune characterization of virus-like particles of GII.17 norovirus strain GZ-L343 in Guangzhou

Abstract:

[Background] Human norovirus is regarded as the leading cause of the outbreak of acute gastroenteritis with GII.4 being the predominant genotype during the past decades. The GII.17 variant that emerged in 2014/2015 was the first non-GII.4 epidemic strain causing a large-scale epidemic in China. The full-length genome sequencing of the GII.17 strain from South China confirmed that it was different from the previously identified GII variants. [Objective] To prepare the virus-like particles and systematically characterize the immunogenicity and functions of GII.17-GZ-L343 in Guangzhou. [Methods] The baculovirus expression system was employed to produce GII.17-GZ-L343 in Sf9 insect cells. The virus-like particle was purified by cesium chloride gradient ultracentrifugation. Finally, the antiserum was prepared and its immune function was evaluated. [Results] The results of SDS-PAGE and Western blotting showed that the molecular weight of the obtained protein was about 58 kDa. The prepared virus-like particle had a diameter of about 30 nm, good immunogenicity, and binding activities to the saliva of type A/B/O/AB secretors and non-secretors. The serum titer after immunization was above 10⁴, and the antiserum had no inhibitory effects on other variants. In addition, the antiserum only blocked the binding of homotypic virus-like particle to the receptor, and did not block the binding of heterotypic virus-like particle. [Conclusion] GII.17-GZ-L343 has a broad binding pattern. Its antiserum is not broad-spectrum for heterotypic virus-like particle and only has blocking effect on homotypic virus-like particle. The results provide theoretical support for further revealing the host adaptation characteristics and evolution mechanism of the virus and developing multivalent vaccines.