Identification of critical antibody-binding sites in the HIV-1 gp41 six-helix bundle core as potential targets for HIV-1 fusion inhibitors.
Formation of the six-helix bundle (6-HB) core between the N- and C-terminal heptad repeats (NHR and CHR) regions of the HIV-1 envelope glycoprotein (Env) transmembrane subunit gp41 is a critical step during the process of virus and target cell membrane fusion. In the present study, we generated a panel of five monoclonal antibodies (mAbs) which specifically recognized the HIV-1 gp41 6-HB formed by the NHR-peptide N36 and CHR-peptide C34 mixture, but did not react with the isolated peptides N36 and C34. These mAbs did not block the HIV-1 Env-mediated cell-cell fusion at physiological temperature (37 degrees C), but inhibited the HIV-1 Env-mediated cell-cell fusion at suboptimal temperature (31.5 degrees C), under which condition the fusion process is slowed down and the viral 6-HB becomes accessible. The fusion inhibitory activity of the mAbs is correlated with their binding affinity with the 6-HB core. By screening 24 6-HB variants with single mutations at the b, c, and f positions in the helical wheels, we found that the critical binding sites of these mAbs were localized in the N-terminal region of the NHR and the C-terminal region of the CHR. These sites may serve as targets for design of small molecule HIV fusion inhibitors, e.g., organic compounds, peptides, and low molecular weight proteins.
Li
Jing
J
Laboratory of Immunology, Department of Biology, Tsinghua University, Beijing 100084, PR China.
Chen
Xi
X
Huang
Jinghe
J
Jiang
Shibo
S
Chen
Ying-Hua
YH
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001666:Binding Sites, Antibody / Q000276:immunology*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005818:Genetic Engineering; D015700:HIV Envelope Protein gp41 / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D006825:Hybridomas; D007117:Immunization, Secondary; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology / Q000378:metabolism; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
D000914:Antibodies, Viral; D000956:Antigens, Viral; D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments; D014760:Viral Fusion Proteins; C514787:gp41 protein, Human immunodeficiency virus 1; C407149:peptide C34; C407148:peptide N36