Neutralization of genetically diverse HIV-1 strains by IgA antibodies to the gp120-CD4-binding site from long-term survivors of HIV infection.
OBJECTIVE
To identify an HIV epitope suitable for vaccine development.


METHODS
Diverse HIV-1 strains express few structurally constant regions on their surface vulnerable to neutralizing antibodies. The mostly conserved CD4-binding site (CD4BS) of gp120 is essential for host cell binding and infection by the virus. Antibodies that recognize the CD4BS are rare, and one component of the CD4BS, the 421-433 peptide region, expresses B-cell superantigenic character, a property predicted to impair the anti-CD4BS adaptive immune response.


METHODS
IgA samples purified from the plasma of patients with HIV infection were analyzed for the ability to bind synthetic mimetics containing the 416-433 gp120 region and full-length gp120. Infection of peripheral blood mononuclear cells by clinical HIV isolates was measured by p24 ELISA.


RESULTS
IgA preparations from three patients with subtype B infection for 19-21 years neutralized heterologous, coreceptor CCR5-dependent subtype A, B, C, D, and AE strains with exceptional potency. The IgAs displayed specific binding of a synthetic 416-433 peptide mimetic dependent on recognition of the CD4-binding residues located in this region. Immunoadsorption, affinity chromatography, and mutation procedures indicated that HIV neutralization occurred by IgA recognition of the CD4BS.


CONCLUSIONS
These observations identify the 421-433 peptide region as a vulnerable HIV site to which survivors of infection can produce powerful neutralizing antibodies. This indicates that the human immune system can bypass restrictions on the adaptive B cell response to the CD4BS, opening the route to targeting the 421-433 region for attaining control of HIV infection.
Planque
Stephanie
S
Chemical Immunology Research Center and Gulf States Hemophilia and Thrombophilia Center, Departments of Pathology and Pediatrics, University of Texas-Houston Medical School, Houston, Texas, USA.
Salas
Maria
M
Mitsuda
Yukie
Y
Sienczyk
Marcin
M
Escobar
Miguel A
MA
Mooney
Jason P
JP
Morris
Mary-Kate
MK
Nishiyama
Yasuhiro
Y
Ghosh
Dipanjan
D
Kumar
Amit
A
Gao
Feng
F
Hanson
Carl V
CV
Paul
Sudhir
S
D016915:AIDS Vaccines / Q000276:immunology*; D001665:Binding Sites; D015704:CD4 Antigens / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000276:immunology*; D015658:HIV Infections / Q000235:genetics / Q000276:immunology* / Q000821:virology; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D009500:Neutralization Tests; D017741:Survivors
D016915:AIDS Vaccines; D015704:CD4 Antigens; D000939:Epitopes; D015699:HIV Envelope Protein gp120