The Protective Effect of a Combination of Human Intracellular and Extracellular Antibodies against Highly Pathogenic Avian Influenza H5N1 Virus

Background:Highly pathogenic avian influenza H5N1 virus is a serious threat to humans. Due to its antiviral activity, antibody-based therapy is one of the possible effective countermeasures. Here,a combination of intracellular and extracellular human antibodies was investigated and showed a better protective effect. Methods: The scFv4F5-based intracellular antibody and full-length IgG1 extracellular antibody vectors were constructed or expressed, respectively. In vitro, the sensitivity, specificity and affinity of these antibodies were detected by western blotting, ELISA, flow cytometry, Biacore X100 SPR technique and microneutralization assay. In vivo, the protective effect of the combination of antibodies and the dynamics of viral replication were tested, and the related cytokines and proteins were detected by ELISA, western blotting and qPCR. Results: The intracellular antibody could inhibit H5N1 virus propagation in A549 cells in a dose-dependent manner. The protective effect of IgG1 was good in post-treatment therapy in a mouse model. When the intracellular antibody was pre-transfected in a combination regimen with IgG1, it had a better protective effect than IgG1 alone. The protective effect was primarily accomplished by inducing the secretion of cytokines, i.e., IFN-γ, IL-6, and IL-10, and the expression of apoptosis-related proteins, i.e., Bim and cleaved PARP. Conclusions: This antibody combination technique could be used as an appropriate and powerful alternative to antiviral therapy.