TABLE 5.
Syncytium inhibition (89.6 envelope) by intact IgG versus F(ab′)2 and Faba
| HIVIG | ID50 (nM)
|
IgG1/IgG3 ratio | |
|---|---|---|---|
| IgG1 | IgG3 | ||
| Intact | 1,200 | 267 | 4.5 |
| F(ab′)2 fragment | 920 | 260 | 3.5 |
| Fab fragment | 5,600 | 4,800 | 1.2 |
a
12E1 cells were infected overnight with recombinant vaccinia virus expressing the envelope of dual-tropic HIV-1 strain 89.6 at 10 PFU/cell. Envelope-expressing cells were preincubated for 60 min with HIVIG subclasses, either intact or after enzymatic digestion into Fab and F(ab′)2 fragments. The cells were then mixed with PM1 target cells at a 1:1 ratio in triplicate, and syncytia were scored after 4 h of incubation at 37°C. The number of syncytia in control RSVIG-treated cultures was 437 ± 49 (mean ± standard deviation). ID50 were derived from linear regression analyses of fusion inhibition values at multiple doses of each Ig preparation.