PRESENTATION OF HIV V3 LOOP EPITOPES FOR ENHANCED ANTIGENICITY, IMMUNOGENICITY AND DIAGNOSTIC POTENTIAL

Objective: To evaluate the immunological properties of a panel of huma n mucin MUC1/HIV V3 loop chimeras. Design: The immunodominant epitope of MUC1 (APDTR) was found to be structurally isomorphous with the tip of the principle neutralizing determinant (PND) of HIV-1 (MN) (GPGRA). A panel of 120 residue, six tandem repeat (TR) and 60 residue, three TR chimeric antigens were constructed in which the repeating MUC1 epit ope is replaced by HIV-1 PND. Each 20 residue TR contains one PND epit ope. The PND of HIV-1 is presented in the native beta-turn conformatio n at the crest of each repeating knob structure of the mucin-like prot ein. Methods: The antigenicity of the chimeric antigens were compared using enzyme-linked immunosorbent assay (ELISA) and HIV-infected patie nt sera. Structural effects of antibody-antigen interactions were dete rmined using surface plasmon resonance, with human monoclonal antibodi es, chimeric antigens and the cyclic and linear V3 loops. Immunogenici ty of three versus six TR was measured in mice. Results: Nine residues of the HIV PND substituted into the mucin backbone were equivalent to the 36 residue cyclic V3 loop in ELISA. The 120 residue antigens indu ced high titer, immunoglobulin (Ig)M and Igc, and HIV-specific antibod ies in mice. Conclusions: MUC1/V3 chimeras efficiently detect HIV-spec ific antibodies in patient sera. Multivalent presentation of the PND i s advantageous for higher affinity antibody-antigen interactions and f or inducing HIV-specific IgM and IgG antibodies.