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AIDS Res Hum Retroviruses. 1995 Mar;11(3):395-403.

Analysis of envelope glycoprotein-specific antibodies from SIV-infected and gp110-immunized monkeys in ACC and ADCC assays.

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Department of Microbiology, Tulane Regional Primate Research Center, Covington, Louisiana 70433, USA.


Sera collected from SIV-infected or recombinant glycoprotein-immunized monkeys were characterized for antibodies participating in antibody-complement-mediated cytolysis (ACC) and antibody-dependent cellular cytolysis (ADCC) in terms of their IgG subclass and epitope specificity. In a competitive inhibition ELISA, gp110-specific antibody reactivity with nondenatured rgp110 was blocked completely by soluble homologous rgp110 and partially inhibited by heterologous rgp110, suggesting cross-reactivity between viral strains. However, only partial inhibition was observed with denatured recombinant gp140 (rgp140) in selected monkeys, indicating that the majority of gp110-specific antibodies recognized conformational epitopes. ACC activity against recombinant vaccinia-infected, envelope-expressing targets was found in sera from both infected and immunized monkeys, whereas ADCC activity was observed only in sera from infected monkeys. ACC was blocked with denatured rgp140 as well as nondenatured rgp110, indicating that ACC-mediating antibodies recognized mainly linear epitopes. In contrast, rgp140 did not compete as effectively as rgp110 in the ADCC assay, indicating that the majority of ADCC antibodies recognized conformational epitopes. Competitive inhibition using three peptide fragments of gp110 indicated that epitopes recognized by ACC antibodies lie within amino acid residues 214-471, a region that spans V3, whereas ADCC-reactive epitopes lie between amino acid residues 52 and 214 at the N-terminal end of gp110. Column chromatography of rhesus IgG resulted in three subclass-enriched fractions, designated IgG-I, IgG-II, and IgG-III. IgG-I, but not IgG-II or IgG-III, from both infected and immunized monkeys mediated ACC, whereas IgG-I and IgG-II from infected monkeys mediated ADCC.(ABSTRACT TRUNCATED AT 250 WORDS).

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