Table 1.
Overview of antibody and neutralization results in suspect positive horses: RBD-ELISA (standardized OD); surrogate neutralization assay (sVNT; percentage of inhibition); pseudotype-based neutralization assay (PVNA): variant-specific neutralizing antibodies (titers) against B.1, Alpha, Beta, Delta and Omicron BA.1 or BA.2 variants. The first six samples (#61, 199, 451, 705, 844 and 948) originate from Swiss horses investigated in this study. The last five samples (#850, 859, 912, 932 and 1020) were from seropositive Californian horses. The cut-off OD value for a suspect positive result in RBD-ELISA is ≥0.568. The cut-off for inhibition in sVNT is >51%. The cut-off for PVNA was 50. The suspect positive RBD-ELISA results, positive sVNT results and highest titers in PVNA are marked in bold.
| Sample ID | Sampling Date | RBD-ELISA | sVNT | B.1 | Alpha | Delta | Omicron BA.1 | Omicron BA.2 |
|---|---|---|---|---|---|---|---|---|
| #705 | May 2020 | 0.592 | 15.9 | ≤50 | ≤50 | ≤50 | ≤50 | n.t. |
| #199 | August 2020 | 0.571 | 21.8 | ≤50 | ≤50 | ≤50 | ≤50 | n.t. |
| #61 | December 2020 | 0.640 | 12.8 | ≤50 | ≤50 | ≤50 | ≤50 | n.t. |
| #451 | January 2022 | 0.634 | 11.4 | ≤50 | ≤50 | ≤50 | ≤50 | n.t. |
| #844 | May 2022 | 0.868 | 74.7 | 101 | 168 | 108 | 71 | 68 |
| #948 | August 2022 | 0.566 | 73.4 | 76 | 120 | 153 | 87 | 59 |
| #850 | August 2020 | 0.875 | 98.2 | 243 | 225 | 120 | ≤50 | n.t. |
| #859 | August 2020 | 1.105 | 100.6 | 543 | 371 | 207 | 71 | n.t. |
| #912 | August 2020 | 1.000 | 100.4 | 363 | 307 | 222 | 54 | n.t. |
| #932 | August 2020 | 1.097 | 100.8 | 1151 | 815 | 636 | 93 | n.t. |
| #1020 | September 2020 | 0.953 | 100.3 | 568 | 403 | 285 | 59 | n.t. |
n.t. = not tested.