Fig. 3.

Reactivity of serum Abs from mice immunized with the gp120_LAI/mAb complex with or without MPL/DDA adjuvant. (A) Serum Ab titers to the whole gp120_LAI protein (top), the V3_LAI peptide (middle), and the N-terminal C1 peptides (bottom). BALB/c mice were immunized with the gp120_LAI/654-D complex or the mixture of gp120_LAI + control mAb 1418 in the presence or absence of adjuvant MPL/DDA (Adj). For controls, a group of animals was also immunized with PBS and MPL/DDA. Immune sera were serially diluted and tested in ELISA for reactivity with recombinant gp120_LAI protein, V3 peptide and C1 peptides coated directly on the microwell plates. Alkaline phosphatase-conjugated anti-mouse IgG was used as the secondary antibody. (B) Reactivity of serum Abs from mice immunized with the gp120_LAI/654-D complex and MPL/DDA with different V3 peptides. To detect cross reactivity of anti-V3 Abs induced by the gp120_LAI/654-D complex, V3 peptides with sequences of LAI, JRFL, MN, and SF162 strains were coated on the microwell plates and reacted with serially diluted sera from the gp120_LAI/654-D + MPL/DDA-immunized animals. (C) Neutralization of HIV-1 pseudovirus expressing the homologous envelope by sera from immunized animals. Sera were serially diluted 3 fold starting from 1:50, pre-incubated with the virus, and tested for virus neutralizing activity in the single round infection assay with TZM-bl cells. Means and standard deviations were derived from duplicate wells. Data from one of two repeated experiments are shown. OD₄₀₅, optical density at 405 nm.