title: A single point mutation in HIV-1 V3 loop alters the immunogenic properties of rgp120.
abstract: The results of the study presented in this report show that clones of env derived from genetically divergent HIV-1 field isolates fall into two major subsets based on the predicted secondary structure of the V3 region in gp120. One subset exemplified by the clones A-UG06c, B-RT3.12 and C-UG045 is predicted to assume a beta-turn conformation in the V3 loop and comprises the GPGX residues. The other subset exemplified by the clones D-UG23c and D-UG042 (GXGX) are deficient in the expression of the beta-turn in the loop. Since secondary conformations are highly likely to confer antigenic properties in a protein backbone at least for B cells, we have used nucleic acid immunization to test the effect of the beta-turn deficiency on the immunogenic potential of rgp120 encoded in these field isolates. As hypothesized, inoculation of BALB/c mice with the env plasmid encoding the beta-turn expressing rgp120 molecules resulted in the development of a vigorous antibody response to the homologous V3 loop peptides. In contrast, immunization with an rgp120 clone deficient in the beta-turn in the V3 loop showed no evidence of antibody development to the V3 loop. Instead, the latter clones triggered T cell proliferative responses and markedly increased the level of IL-2 and IFN-gamma production by T cells. Significantly, reconstitution of the beta-turn conformation by site-directed mutagenesis of a single V3 loop residue yielded rgp120 molecules which restored antibody production while diminishing the cell-mediated immune (CMI) responses to the V3 residue. These observations demonstrate the marked impact of a single amino acid substitution on the immunogenic properties of V3 region in gp120 encoded by divergent HIV-1 field isolates.
authors.affiliation: Department of Biology, The City College of New York, New York 10031, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Lee
authors.forename: G A
authors.initials: GA
authors.lastname: Pestano
authors.forename: J
authors.initials: J
authors.lastname: Riley
authors.forename: A S
authors.initials: AS
authors.lastname: Hasan
authors.forename: M
authors.initials: M
authors.lastname: Pezzano
authors.forename: M
authors.initials: M
authors.lastname: Samms
authors.forename: K J
authors.initials: KJ
authors.lastname: Park
authors.forename: J
authors.initials: J
authors.lastname: Guyden
authors.forename: W M
authors.initials: WM
authors.lastname: Boto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004279:DNA, Viral / Q000276:immunology; D015483:HIV Antibodies / Q000097:blood; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D015497:HIV-1 / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007114:Immunization; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D010957:Plasmids / Q000235:genetics; D017354:Point Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology
chemical_list: D004279:DNA, Viral; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments; D011994:Recombinant Proteins