A Replicating Modified Vaccinia Tiantan Strain Expressing an Avian-Derived Influenza H5N1 Hemagglutinin Induce Broadly Neutralizing Antibodies and Cross-Clade Protective Immunity in Mice

Xiao, Haixia; Liu, Li; Zhu, Qingyu; Tan, Zhiwu; Yu, Wenbo; Tang, Xian; Zhan, Dawei; Du, Yanhua; Wang, Haibo; Liu, Di; Li, Zhixin; Yuen, Kwok-Yung; Ho, David D.; Gao, George F.; Chen, Zhiwei

To further determine the efficacy of vaccination, three groups of mice were immunized twice with 3610 6 PFU of MVTT HA-QH on day 0 and 31, via the intranasal, intramuscular and oral administration routes, respectively. We included the oral route, as it is one of the easiest methods of vaccination for resourcelimited settings. Serum samples collected on day 0 before vaccination, day 28 after the first immunization and 2 weeks after the second inoculation (day 45) were subjected to HI and NT assays using the live homologous A/BhG/QH/1/05 strain. We found that all three vaccination routes were able to induce both HI and NT responses ( Table 2 ). The I.N. route induced seemingly higher levels of both HI and NT responses than the other two routes after the first immunization. Moreover, the second immunization boosted the primary responses significantly, more specifically, 4-16 fold for HI and 5-7 fold for NT titers, which are consistent to findings using the pseudoviral neutralization assay (Fig. 3A) . Unexpectedly, two of the five mice in the oral group did not respond to the vaccine after two immunizations for unknown reasons. For the control, mice receiving PBS did not generate any responses, as expected. We did not conduct the ELIspot assay in this experiment because the animals were kept for subsequent viral challenge.