Biblioteca Virtual en Salud

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.