Table 3.
VHH interference of ricin attachment to host cell receptors.
| % Inhibition | |||
|---|---|---|---|
| Tier | VHH | ASF a | THP-1 b |
| I | V5E4 | 64 ± 8 | 45 ± 16 |
| JIZ-B7 | 48 ± 9 | 36 ± 11 | |
| V2C11 | 65 ± 11 | 50 ± 16 | |
| V5G1 | 60 ±12 | 44 ± 12 | |
| II | V5D1 * | 0 | 22 ± 17 |
| V2D4 | 62 ± 14 | 28 ± 12 | |
| V4A1 | 59 ± 9 | 40 ± 7 | |
| V8D12 | 57 ± 8 | 46 ± 10 | |
| III | V1B4 * | 19 ± 18 | 27 ± 18 |
| V5G6 * | 38 ± 13 | 16 ± 14 | |
| V5G12 * | 0 | 3 ± 14 | |
| V5H2 | 55 ± 2 | 40 ± 6 | |
| V6B9 | 57 ± 3 | 38 ± 8 | |
| Controls | V5D5 | 84 ± 10 | 90 ± 1 |
| V5H6 | 6 ± 11 | 18 ± 8 | |
Binding assays were performed as described in Materials and Methods. Listed VHHs were a premixed with biotinylated ricin (0.25 µg/mL) and was applied to ASF coated plates or b premixed with FITC-labeled ricin (1 μg/mL), applied to THP-1 cells, and subjected to flow cytometry. Numbers listed represent % ricin binding inhibition ± standard deviation for three replicates. The asterisks (*) denote VHHs whose epitopes are holotoxin-specific. JIZ-B7 is bolded for emphasis. Underlines indicate members of the V2C11 family of VHHs.