Generation, Characterization and Epitope Mapping of Two Neutralizing and Protective Human Recombinant Antibodies against Influenza A H5N1 Viruses

Lina Sun,Dexin Li,Jessica A Belser,Jacqueline M Katz,Qun Li,Xiuhua Lu,Feng Liu,Chuan Li,Min Wang,Qinzhi Liu,Jiandong Li,Yuelong Shu,Zi Li,Xiaofen Hu,Kathy Hancock,Mifang Liang,Jörg Hermann Fritz

doi:10.1371/journal.pone.0005476

Abstract

BackgroundThe development of new therapeutic targets and strategies to control highly pathogenic avian influenza (HPAI) H5N1 virus infection in humans is urgently needed. Broadly cross-neutralizing recombinant human antibodies obtained from the survivors of H5N1 avian influenza provide an important role in immunotherapy for human H5N1 virus infection and definition of the critical epitopes for vaccine development.Methodology/Principal FindingsWe have characterized two recombinant baculovirus-expressed human antibodies (rhAbs), AVFluIgG01 and AVFluIgG03, generated by screening a Fab antibody phage library derived from a patient recovered from infection with a highly pathogenic avian influenza A H5N1 clade 2.3 virus. AVFluIgG01 cross-neutralized the most of clade 0, clade 1, and clade 2 viruses tested, in contrast, AVFluIgG03 only neutralized clade 2 viruses. Passive immunization of mice with either AVFluIgG01 or AVFluIgG03 antibody resulted in protection from a lethal H5N1 clade 2.3 virus infection. Furthermore, through epitope mapping, we identify two distinct epitopes on H5 HA molecule recognized by these rhAbs and demonstrate their potential to protect against a lethal H5N1 virus infection in a mouse model.Conclusions/SignificanceImportantly, localization of the epitopes recognized by these two neutralizing and protective antibodies has provided, for the first time, insight into the human antibody responses to H5N1 viruses which contribute to the H5 immunity in the recovered patient. These results highlight the potential of a rhAbs treatment strategy for human H5N1 virus infection and provide new insight for the development of effective H5N1 pandemic vaccines.

Highlights

Multiple distinct and geographically diverse genotypes of highly pathogenic avian influenza (HPAI) A H5N1 viruses exist and continue to cause outbreaks of disease in domestic poultry on three continents [1,2]
We describe for the first time the generation and characterization of two broadly cross-neutralizing recombinant human antibodies generated by screening a Fab antibody phage library derived from a patient recovered from infection with a clade 2.3 H5N1 virus
Through epitope mapping, we identify two distinct epitopes on H5 HA molecule recognized by these recombinant baculovirus-expressed human antibodies (rhAbs) and demonstrate their potential to protect against a lethal H5N1 virus infection in a mouse model

Summary

Introduction

Multiple distinct and geographically diverse genotypes of highly pathogenic avian influenza (HPAI) A H5N1 viruses exist and continue to cause outbreaks of disease in domestic poultry on three continents [1,2]. H5N1 viruses are endemic in multiple countries in parts of Asia, Africa, and possibly the Middle East [2] These viruses pose a substantial public health threat; if H5N1 viruses acquire the ability to spread efficiently in humans lacking antibodymediated immunity to the H5 surface protein, a pandemic would result. H5N1 Clade 2.1 viruses are endemic in Indonesia, whereas Clade 2.2 viruses spread from Qinghai Lake, China in 2005, and are found in birds in Western Asia, the Middle East, Europe and Africa and have caused fatal human disease in these respective regions. The development of new therapeutic targets and strategies to control highly pathogenic avian influenza (HPAI) H5N1 virus infection in humans is urgently needed. Cross-neutralizing recombinant human antibodies obtained from the survivors of H5N1 avian influenza provide an important role in immunotherapy for human H5N1 virus infection and definition of the critical epitopes for vaccine development

Methods

Results

Conclusion