Volume 19, Number 12—December 2013
Dispatch
Novel Variants of Clade 2.3.4 Highly Pathogenic Avian Influenza A(H5N1) Viruses, China
Table 2
Efficacy of vaccines against highly pathogenic avian influenza virus A(H5N1) clade 2.3.4 variants in chickens, China*
Virus and vaccine type | HI titer ±SD, log2 |
Challenge test results, by swab type, no. positive birds/no. tested (mean titer ±SD)† |
No. surviving birds/total no. | |||||||
---|---|---|---|---|---|---|---|---|---|---|
3 dpc |
5 dpc |
|||||||||
Re-4 | Re-5 | k0602 | Tracheal | Cloacal | Tracheal | Cloacal | ||||
k0602 | ||||||||||
Re-4/Re-5 | 8.10 ±0.97 | 6.20 ±0.31 | 2.25 ±0.45 | 6/6 (3.79 ±1.46) | 4/6 (2.25 ±2.39) | 2/3 (2.17 ±2.40) | 2/3 (2.92 ±2.55) | 1/7 | ||
rk0602 | 2.10 ±0.37 | 3.27 ±0.33 | 9.35 ±0.75 | 0/10 | 0/10 | 0/10 | 0/10 | 10/10 | ||
Control‡ |
ND |
ND |
ND |
ND |
ND |
ND |
ND |
0/5 |
||
k0603 | ||||||||||
Re-4/Re-5 | 7.70 ±0.26 | 5.70 ±0.29 | 1.93 ±1.21 | 8/8 (3.15 ±1.30) | 8/8 (3.50 ±0.25) | 3/3 (3.50 ±0.43) | 3/3 (2.33 ±0.58) | 1/10 | ||
rk0602 | 2.05 ±0.85 | 2.75 ±0.57 | 9.25 ±0.71 | 0/10 | 0/10 | 0/10 | 0/10 | 10/10 | ||
Control‡ | ND | ND | ND | ND | ND | ND | ND | 0/5 |
*Chickens were immunized with the Re4/Re5 or the inactivated rk0602 vaccine (the HA and NA genes of rk0602 were derived from subtype H5N1 k0602 virus; the internal genes were from PR8), and HI antibody titers were determined on day 28 postvaccination. HI, hemagglutination inhibition assay; dpc, days postchallenge; ND, not done.
†Birds were challenged with 106.0 50% egg infectious dose (EID50) of k0602 or k0603 virus; virus titers are expressed as log10 EID50/0.1 mL.
‡Two groups of 5 mock-vaccinated chickens served as controls; all died within 3 dpc.