TABLE 2.
Characteristics of RTA- and RTB-specific VHHs
| VHHb | EC50c | Kd | IC50 | Competitive inhibition assaysa |
|||
|---|---|---|---|---|---|---|---|
| PB10 | SyH7 | IB2 | GD12 | ||||
| nm | nm | nm | |||||
| RTA-F5* | 1.50 | 2.24 | 5 | +++ | – | – | – |
| RTA-F6 | 1.00 | – | – | ++ | – | ||
| RTA-G12 | 0.50 | 0.62 | >330 | +++ | – | – | – |
| RTA-A7 | 1.20 | +++ | – | – | – | ||
| RTA-D9 | 3.30 | – | – | – | – | ||
| RTA-D10* | 0.66 | 0.63 | 25 | – | – | – | – |
| RTA-E1 | 3.00 | – | + | – | – | ||
| RTA-E3 | 2.00 | +++ | – | – | – | ||
| RTA-E5* | 0.83 | 1.94 | 5 | +++ | – | – | – |
| RTA-F10 | 13.20 | – | – | – | – | ||
| RTA-G11 | 0.83 | 0.35 | 90 | +++ | – | – | – |
| SylH3 | 24B11 | ||||||
| RTB-B1 | 4.10 | – | – | ||||
| RTB-C12 | 1.65 | – | – | ||||
| RTB-D12 | 0.83 | – | – | ||||
| RTB-G5* | 0.23 | – | – | ||||
| RTB-G10 | 1.65 | – | – | ||||
| RTB-B7* | 0.66 | 1.33 | 4 | – | – | ||
| RTB-B9* | 1.20 | – | – | ||||
| RTB-D8 | 3.63 | – | – | ||||
| RTB-G4 | 33.00 | – | – | ||||
a RTA- or RTB-specific murine mAbs were tested for capacity to prevent indicated VHHs binding to ricin in an ELISA format. The number of plus signs indicates the degree of relative inhibition (−, no reduction; +, 10–30% reduction; ++, 30–60% reduction; and +++, >60% reduction).
b Underlining indicates neutralizing VHHs. Asterisks indicate VHHs used in heterodimer formation.
c The values indicate the effective concentration of VHH required to achieve 50% maximal binding to ricin by ELISA.