Objective:To analyze and evaluate the effect of OX40L as a potential adjuvant for H7N9 whole-virion inactivated vaccine (WIV).Methods:Fifty BALB/c mice were randomly divided into five groups and immunized intramuscularly with PBS (control group) and 1.5 μg WIV alone or in combination with 0.6, 1.8 or 3.0 μg Fc-fused OX40L (OX40L/Fc) adjuvant. Three weeks after immunization, IgG, IgG1 and IgG2 titers were measured by ELISA and hemagglutination inhibition (HI) assay. Moreover, the mice were challenged with 50×median lethal dose (LD 50) of homologous virus and the changes in mouse body weight and survival rate were recorded to evaluate the effects of OX40L. Flow cytometry was used to analyze the mechanism of OX40L as an adjuvant 7 d after immunization. Results:Compared with immunization with WIV alone, co-immunization of WIV with OX40L/Fc induced higher antigen-specific IgG in mice. The geometric mean titers (lgGMT) of antibodies induced by 0.6, 1.8 and 3.0 μg OX40L/Fc reached 3.79, 4.40 and 4.20, respectively. WIV combined with OX40L/Fc induced high levels of IgG1 and IgG2a without influencing Th1/Th2 balance. HI antibodies were also higher in WIV+ 1.8 μg OX40L/Fc and WIV+ 3.0 μg OX40L/Fc groups than in WIV group (6.25±0.50 and 5.70±0.97 vs 3.00±0.97, both P<0.05). WIV combined with 1.8 or 3.0 μg OX40L/Fc could protect 80% or 75% of mice against lethal challenge with H7N9 and result in less weight loss as compared with WIV alone. The most effective dose of OX40L/Fc was 1.8 μg. Flow cytometry showed that WIV (0.6, 1.8, 3.0 μg) in combination with OX40L/Fc enhanced the proliferation of T follicular helper cells (Tfh) through promoting the expression of CXCR5 and PD-1 as compared with WIV alone (all P<0.05). Conclusions:This study suggested that OX40L was beneficial to potent antibody responses induced by H7N9 WIV through promoting Tfh cell proliferation.

Objective To create a recombinant rabies virus overexpressing IL-33 and to clarify the effect of IL-33 overexpression on the phenotypic characteristics of recombinant virus in vitro. Methods The IL-33 gene was obtained and amplified from the brain of a highly virulent strain of rabies infected mouse. It was then inserted between the G and L genes of the parental virus LBNSE genome by reversing genetic manipulation and rescuing a recombinant virus overexpressing IL-33. BSR cells or mouse NA cells were infected with recombinant rabies virus (rLBNSE-IL33) and the parental strain LBNSE. Sequencing and fluorescent antibody virus neutralization assay was employed to detect the stability of recombinant virus at multiplicity of infection=0.01. Viral titres focal forming units (FFU) were detected to plot multi-step growth curves (multiplicity of infection=0.01). Cytotoxicity assay kit was used to detect cellular activity. ELISA was adopted to identify the IL-33 in the supernatant of infected cells of different multiplicity of infection. Results Rescued rLBNSE-IL33 overexpressing IL-33 remained stable for at least 10 consecutive generations and had virus titers of approximately 10⁸ FFU/mL. rLBNSE-IL33 was able to express IL-33 at high levels in a dose-dependent manner, but no high expression of IL-33 was detected in the supernatant of cells infected by LBNSE. Examination of the titers of rLBNSE-IL33 and the parental strain LBNSE in BSR and NA cells over 5 days showed no significant differences and similar kinetic properties in growth. Overexpression of IL-33 had no significant effect on the proliferation and activity of infected cells. Conclusion Overexpression of IL-33 does not significantly affect the phenotypic characteristics of recombinant rabies virus in vitro.
Animals ; Cricetinae ; Mice ; Cell Line ; Interleukin-33/genetics* ; Rabies virus/genetics* ; Phenotype