TABLE 3.

Percent enhancement in recognition by conformation-dependent antibodies following heat treatment^a

Virus	% gp120 binding to:
	CD4 BS				2G12 specific (2G12)	V3 specific (447-52D)
	CD4-IgG	IgG1b12	205-46-9	205-43-1
HIVSX	243	193	255	295	94	128
HIVNL4-3	83	100	ND	ND	97	112

^aAliquots of HIV_SX or HIV_NL4-3 (130 ng of p24/ml) were harvested in serum-free medium and held at 4°C or heated to 62°C for 30 min. Binding using the indicated reagents was performed for 45 min at 37°C in 200 μl. The retention of epitopes was assessed by HIV gp120 capture ELISA. Control reactivity without Ag was <0.1 for each antibody. Antibody concentrations were determined by titration. IgG1b12 was used at 2,000 ng/ml; ODs at 4°C were 0.54 ± 0.03 for HIV_SX and 0.31 ± 0.08 for HIV_NL4-3. 205-46-9 was used at 2,000 ng/ml; OD at 4°C was 0.700 ± 0.06 for HIV_SX. 205-43-1 was used at 2,000 ng/ml; OD at 4°C was 0.900 ± 0.02 for HIV_SX. 2G12 was used at 400 ng/ml; ODs at 4°C were 1.92 ± 0.05 for HIV_SX and 1.43 ± 0.04 for HIV_NL4-3. 447-52D was used at 2,000 ng/ml; ODs at 4°C were 1.31 ± 0.06 for HIV_SX and 0.34 ± 0.06 for HIV_NL4-3. CD4-IgG was synthesized in 293T cells and used at a 1:10 dilution; ODs at 4°C were 1.04 ± 0.05 for HIV_SX and 1.02 ± 0.04 for HIV_NL4-3. The assay was performed in triplicate. Data are representative of three independent experiments. ND, not done.