Table 2.
Antigenic relationships between the neuraminidases of H9N2, H2N2, and H3N2 viruses
| Viruses | Subtype | Neuraminidase inhibition titer*
|
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Hyperimmune rabbit sera
|
Postinfection chicken sera
|
Postinfection ferret sera
|
|||||||
| Ty/Wis 1/66 | A/Sing 1/57 | A/Aichi 2/68 | A/Beij 32/92 | Qa/HK G1/97 | Ck/HK G9/97 | A/HK 1073/99 | Ck/HK G9/97 | ||
| Ty/Wisconsin/1/66 | H9N2 | 5120 | 640 | < | < | < | < | < | < |
| A/Singapore/1/57 | H2N2 | 640 | 2560 | < | < | < | 80 | < | < |
| A/Aichi/2/68 | H3N2 | 160 | 320 | 5120 | 640 | < | 80 | < | < |
| A/Beijing/32/92 | H3N2 | < | < | 160 | 1280 | ND | ND | ND | ND |
| A/Hong Kong/1073/99 | H9N2 | 640 | 320 | 160 | < | 320 | 320 | 320 | 160 |
| A/Hong Kong/1074/99 | H9N2 | 640 | 320 | 160 | < | 320 | 320 | 320 | 160 |
| Qa/Hong Kong/G1/97 | H9N2 | 320 | < | < | < | 640 | 160 | 80 | 160 |
| Ck/Hong Kong/G9/97 | H9N2 | 160 | 640 | 160 | < | 640 | 1280 | 80 | 640 |
*
Homologous titers in bold. Rabbit sera, < means < 160; chicken and ferret sera, < means < 80; ND, not done.