title: Expression and functional activity of isotype and subclass switched human monoclonal antibody reactive with the base of the V3 loop of HIV-1 gp120.
abstract: Immunoglobulins undergo isotype switching in response to antigenic stimulation. The C(H) domains, in particular the hinge region, impose structural constraints on the interaction of antibody with antigen, especially multivalent antigens such as HIV. We previously showed that switching the IgG1 anti-HIV human monoclonal antibody (HMAb) F105 to an IgG3 resulted in significantly enhanced neutralization of HIV. To further investigate the influence of isotype, including the functional activity of HMAbs switched to IgA, which may be important in mucosal defenses, isotype switched antibodies have been generated for the anti-V3 loop base IgG2 HMAb F425B4e8. Reactivity of the IgG1 antibody was greater than the parental IgG2 antibody for SF2 infected cells but less for primary isolate virions. In contrast, there was less reactivity of the IgG3 with either infected cells or virions. IgA reacted significantly more with infected cells and virions as compared to the IgG subclasses. In contrast to previous studies whereby IgG3 enhanced neutralization, comparable neutralization of primary isolate virus was observed for IgG subclasses (IgG1, IgG2, IgG3) and IgA. This may reflect differences in the exposure of epitopes recognized by the HMAb with antibody flexibility being important to neutralization by antibodies reactive with obscured epitopes (e.g., CD4 binding site). Further analysis of the in vitro activity of isotype or subclass switched antibodies, IgA in particular, alone and in combination with other HMAbs, will provide important information on the role of IgG subclass and IgA antibodies on protective immunity to HIV.
authors.affiliation: Beth Israel Deaconess Medical Center, Massachusetts 02215, USA.
authors.forename: Fangbing
authors.initials: F
authors.lastname: Liu
authors.forename: Pablo Lopez
authors.initials: PL
authors.lastname: Bergami
authors.forename: Mark
authors.initials: M
authors.lastname: Duval
authors.forename: David
authors.initials: D
authors.lastname: Kuhrt
authors.forename: Marshall
authors.initials: M
authors.lastname: Posner
authors.forename: Lisa
authors.initials: L
authors.lastname: Cavacini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D001483:Base Sequence; D003001:Cloning, Molecular; D000939:Epitopes / Q000276:immunology*; D005803:Genes, Immunoglobulin; D015483:HIV Antibodies / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015488:HIV Antigens / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D007070:Immunoglobulin A / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D017578:Immunoglobulin Class Switching; D007074:Immunoglobulin G / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D007132:Immunoglobulin Isotypes / Q000235:genetics / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests; D010446:Peptide Fragments / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014162:Transfection; D014407:Tumor Cells, Cultured; D014771:Virion / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D015483:HIV Antibodies; D015488:HIV Antigens; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007135:Immunoglobulin Variable Region; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins