Effect of plasmid DNA immunizations with gp120 fused with MCP-3 or β-defensin 2.

Plasmid DNA immunizations with gp120 fused with MCP-3 or β-defensin 2 elicit HIV-1 Env–neutralizing antibodies. Titrated amounts of pooled sera from mice immunized with pMCP3gp120, pmDF2βgp120, and pvMIP2gp120 (panel A), or with pMCP3gp120, pMDCgp120, and pMCP3-EGFP (an irrelevant MCP-3 fusion protein expressing plasmid) (panel B) were incubated with Tf228 cells, which express HIV LAI envelope glycoprotein, and SupT1 cells, which express human CD4 and CXCR4. Control samples (100% fusion) contained 5% sera from untreated mice (control medium). Fusion was measured by the amount of β-galactosidase activity in the cell lysates of fused cells at OD₅₉₅. Total serum immunoglobulin was purified from pMCP3gp120-vaccinated mice on protein G–Sepharose and also tested for its ability to inhibit cell fusion, after normalization to anti-gp120 Ab content (IgG-pMCP3gp120). These results are representative of 3 independent experiments involving 5 mice per group.