TABLE 2.
Detection of equine influenza virus by virus isolation, antigen detection, and RT-PCR after repeat freeze-thaw cycles in samples with or without FCS
| No. of freeze-thaw cycles | Samplea | EID50/ml | TCID50/ml | DFA | RT-PCR Ob | RT-PCR Ic |
|---|---|---|---|---|---|---|
| 0 | A (F) | 107.3 | ≥107.5 | +++ | + | + |
| A | 107.5 | ≥107.5 | ++ | + | + | |
| B (F) | 106 | 105.25 | − | + | + | |
| B | 105.83 | 105.75 | − | + | + | |
| C (F) | 102.5 | 102.75 | − | − | + | |
| C | 102.3 | 103 | − | − | + | |
| 1 | A (F) | 107.16 | 107 | +++ | + | + |
| A | 105.5 | 106.75 | ++ | + | + | |
| B (F) | 104.6 | 105.25 | − | + | + | |
| B | 103.6 | 103.75 | − | + | + | |
| C (F) | 102 | 102 | − | − | + | |
| C | 101 | − | − | − | + | |
| 2 | A (F) | 106.5 | 106.5 | +++ | + | + |
| A | 105.3 | 105.5 | ++ | + | + | |
| B (F) | 104 | 104.5 | − | + | + | |
| B | 101.16 | 101.25 | − | + | + | |
| C (F) | 101.6 | 101.75 | − | − | + | |
| C | − | − | − | − | + | |
| 3 | A (F) | 106.3 | 106.75 | +++ | + | + |
| A | 104.16 | 104.5 | ++ | + | + | |
| B (F) | 103.6 | 104.25 | − | + | + | |
| B | − | − | − | + | + | |
| C (F) | 101 | − | − | − | + | |
| C | − | − | − | − | + | |
| 4 | A (F) | 106.16 | 106.25 | +++ | + | + |
| A | 103.83 | 103.5 | ++ | + | + | |
| B (F) | 103.3 | 103.5 | − | + | + | |
| B | − | − | − | + | + | |
| C (F) | 100.83 | − | − | − | + | |
| C | − | − | − | − | − |
a
F, with FCS. Other samples are without FCS.
b
PCR O, PCR using the NPF and NPR primers.
c
PCR I, nested PCR using NPF, NPR, NPFI, and NPRI.