Generation, characterization and epitope mapping of two neutralizing and protective human recombinant antibodies against influenza A H5N1 viruses.
BACKGROUND
The 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.


RESULTS
We 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
Importantly, 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.
Sun
Lina
L
State Key Laboratory for Infectious Disease Control and Prevention, National Institute for Viral Disease Control and Prevention, China CDC, Beijing, China.
Lu
Xiuhua
X
Li
Chuan
C
Wang
Min
M
Liu
Qinzhi
Q
Li
Zi
Z
Hu
Xiaofen
X
Li
Jiandong
J
Liu
Feng
F
Li
Qun
Q
Belser
Jessica A
JA
Hancock
Kathy
K
Shu
Yuelong
Y
Katz
Jacqueline M
JM
Liang
Mifang
M
Li
Dexin
D
D000328:Adult; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000914:Antibodies, Viral / Q000235:genetics / Q000276:immunology*; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007114:Immunization; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests; D010446:Peptide Fragments / Q000276:immunology*; D019151:Peptide Library; D011994:Recombinant Proteins / Q000276:immunology*
D000914:Antibodies, Viral; D010446:Peptide Fragments; D019151:Peptide Library; D011994:Recombinant Proteins