TABLE 2.
Selection of PRRSV phage-display libraries with porcine sera: description of a simple method to monitor the specific enrichment for epitope-displaying phagesa
| Library | Selection no. and Sepharose type | Pig no. | Amt of 0-dpi serum used (μl) | Titer (PFU/ml)
|
Output-input ratio | Pig no. | Amt of 42-dpi serum used (μl) | Titer (PFU/ml)
|
Output-input ratio | Specific enrichment ratio | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Input | Output | Input | Output | |||||||||
| ORF 1 | 1, A | 12 | 2 | 1.0 × 1013 | 1.2 × 105 | 1.4 × 10−6 | 12 | 2 | 1.0 × 1013 | 6.0 × 105 | 6.9 × 10−6 | 4.6 |
| 2, G | 10 | 0.5 | 3.6 × 1013 | 1.6 × 106 | 5.1 × 10−6 | 10 | 0.5 | 3.7 × 1013 | >4 × 107 | >1.2 × 10−4 | >24 | |
| 3, A | 12 | 0.25 | 5.3 × 1013 | 2.5 × 105 | 5.3 × 10−7 | 12 | 0.25 | 1.7 × 1013 | 1.8 × 107 | 1.3 × 10−4 | 245 | |
| ORF 2-3 | 1, A | 12 | 2 | 1.3 × 1013 | 1.5 × 105 | 1.4 × 10−6 | 12 | 2 | 1.3 × 1013 | 1.6 × 105 | 1.4 × 10−6 | 1 |
| 2, G | 10 | 0.5 | 7.1 × 1013 | 4.8 × 105 | 7.8 × 10−7 | 10 | 0.5 | 8.8 × 1013 | 1.2 × 106 | 1.6 × 10−6 | 2 | |
| 3, A | 12 | 0.25 | 8.6 × 1013 | 3.2 × 106 | 4.3 × 10−6 | 12 | 0.25 | 8.3 × 1013 | 2.7 × 107 | 3.7 × 10−5 | 9 | |
| 4, G | 10 | 0.25 | 9.0 × 1013 | 1.0 × 106 | 1.3 × 10−6 | 10 | 0.25 | 8.0 × 1013 | 1.5 × 107 | 2.1 × 10−5 | 16 | |
| ORF 4-7 | 1, A | 12 | 2 | 4.6 × 1012 | 1.3 × 105 | 3.3 × 10−6 | 12 | 2 | 4.6 × 1012 | 1.0 × 105 | 2.5 × 10−6 | 1 |
| 2, G | 10 | 0.5 | 3.7 × 1013 | 2.0 × 105 | 6.2 × 10−7 | 10 | 0.5 | 1.1 × 1013 | ND | ND | ND | |
| 3, A | 12 | 0.25 | 1.7 × 1012 | 2.1 × 105 | 1.4 × 10−5 | 12 | 0.25 | 3.5 × 1012 | 4.2 × 106 | 1.4 × 10−4 | 10 | |
PRRSV phage display libraries underwent parallel selections with 0-dpi (free for PRRSV antibodies) and 42-dpi (containing high titers of anti-PRRSV antibodies) porcine sera. Serum from two pigs and two types of Sepharose (protein A or protein G) were used in alternate selection rounds, as indicated. Three or four cycles of selection were performed using successively lower serum levels. For all selection rounds, the input was 10 μl of library with the indicated titer, and the output was 1.15 ml of eluate with the indicated titer. The output-input ratio was calculated as (titer of eluate × 1.15)/(titer of input library × 0.01). The specific enrichment ratio was calculated by dividing the output-input ratio obtained with the 42-dpi serum with the output-input ratio obtained with the 0-dpi serum. ND, not done.