Table 1.
Seroresponse following challenge with Norwalk virus, detected by HAI ELISA and blocking assays, by study visit (n = 34)a
| Patient parameterb | Day 0 | Day 28 | Day 180 |
|---|---|---|---|
| Infected, gastroenteritis (n = 12) | |||
| HAI | |||
| GMT (95% CI) | 9 (6, 14) | 341 (194, 599) | 78 (52, 118) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| % with titer of ≥40 | 8.3 | 100 | 100 |
| HBGA blocking assay | |||
| GMT BT50 (95% CI) | 34 (23,51) | 449 (260, 777) | 404 (250, 651) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| ELISA | |||
| GMT (95% CI) | 3,800 (1,200, 12,000) | 580,000 (290,000, 1,200,000) | 82,000 (47,000, 140,000) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| Infected, no gastroenteritis (n = 6) | |||
| HAI | |||
| GMT (95% CI) | 32 (15, 68) | 685 (287, 1,633) | 180 (74, 437) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| % with titer of ≥40 | 83.3 | 100 | 100 |
| HBGA blocking assay | |||
| GMT BT50 (95% CI) | 167 (78, 356) | 1,957 (1,051, 3,646) | 903 (494, 1,652) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| ELISA | |||
| GMT (95% CI) | 12,000 (4,400, 30,000) | 1,000,000 (530,000, 2,000,000) | 130,000 (61,000, 280,000) |
| Seroresponse frequency (%) | NA | 100 | 100 |
| Uninfected (n = 16)c | |||
| HAI | |||
| GMT (95% CI) | 9 (6, 14) | 8 (5, 14) | 8 (5, 13) |
| Seroresponse frequency (%) | NA | 0 | 0 |
| % with titer of ≥40 | 6.3 | 6.3 | 6.3 |
| HBGA blocking assay | |||
| GMT BT50 (95% CI) | 40 (25, 64) | 41 (25, 67) | NT |
| Seroresponse frequency (%) | NA | 0 | NT |
| ELISA | |||
| GMT (95% CI) | 1,200 (350, 3,900) | 1,000 (300, 3,400) | 1,000 (300, 3,400) |
| Seroresponse frequency (%) | NA | 0 | 0 |
a
The seroresponse represents the percentage of persons within each group with a ≥4-fold rise in titer relative to the day 0 (d0) value.
b
Abbreviations: CI, confidence interval; HAI, hemagglutination inhibition; NA, not applicable; NT, not tested; HBGA, histo-blood group antigen; BT50, the level of antibody that blocks 50% of the signal generated from binding of Norwalk virus VLPs to HBGAs in an HBGA blocking assay.
c
The majority of the uninfected individuals had a reason to resist infection, including receipt of placebo, a nonfunctional fucosyltransferase 2, or blood group B or AB.