Scientia Agricultura Sinica ›› 2023, Vol. 56 ›› Issue (15): 3040-3050.doi: 10.3864/j.issn.0578-1752.2023.15.017

• ANIMAL SCIENCE·VETERINARY SCIENCE • Previous Articles    

The Protective Efficacy of Commercial Vaccines Against H9N2 Avian Influenza Virus of Branch h9.4.2.5 Isolated in China

MA Qi1(), HE XinWen1, WANG Yan1, LIU YanJing1, PAN ShuXin1,3, HOU YuJie1, SHI JianZhong1,3, DENG GuoHua1,3, BAO HongMei1,3, LIU JingLi2, GUO XingFu2, MAO ShengGang2, HU JingLei2, LU Tong2, YANG Fan2, TIAN GuoBin1,3, ZENG XianYing1,3(), CHEN HuaLan1,3()   

  1. 1 National Poultry Laboratory Animal Resource Center/State Key Lab for Animal Disease Control and Prevention/Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069
    2 Harbin Weike Biotechnology Company Limited, Harbin 150069
    3 Key Laboratory for Prevention and Control of Avian Influenza and Other Major Poultry Diseases, Ministry of Agriculture and Rural Affairs, Harbin 150069
  • Received:2022-07-04 Accepted:2022-09-15 Online:2023-08-01 Published:2023-08-05

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Abstract:

【Objective】 There are many commercial inactivated vaccines against the H9 subtype avian influenza approved for use in China, and their protection efficacy and selection have been widely concerned by farmers. In this study, the protection efficacy of main commercial vaccines against H9N2 viruses recently isolated in the field were evaluated, so as to provide the research reference for guiding the prevention and control of H9 subtype AI by immunization in China.【Method】 According to the vaccine batch release of the National Veterinary Drug Basic Information Database in China, 4 commercial vaccines (labeled as A-D) with large batches were selected from 40 kinds of sold H9 commercial vaccines. The four H9N2 subtype AIV, including CK/XJ/S1204/2015, DK/JX/S4512/2017, CK/YN/S1666/2020 and CK/NX/S4590/2020, belonging to h9.4.2.5 branch and isolated at different times and places, were used to evaluate the protection efficacy of selected commercial H9 subtype AI vaccines. The 50% chicken embryo infection (EID50), 50% chicken infection (CID50), and 50% cell infection (TCID50) of the four viruses were tested to determine the challenge dose of the animal experiment and the infection dose of the cell test. 40 3-week-old SPF chickens were injected intramuscularly with 4 kinds of inactivated vaccine, and the groups of 10 similar SPF chickens were inoculated with PBS as control group. 3 weeks post vaccination (p.v.), the serum of all experimental chickens were collected before challenge, the hemagglutination inhibition (HI) and neutralization (NT) antibody titers were detected by HI test and neutralization test; the 40 immunized chickens of each vaccine were randomly divided into four groups, and 10 chickens of each vaccine and 10 control chickens were infected intranasally with the 10 CID50 of each H9N2 virus. Oropharyngeal and cloacal swabs were collected on days 3 and 5 post challenge (p.c.) for virus shedding detection and calculation of the protective rate of each vaccine. 【Result】 The CID50 of the four strains were 103.5 EID50/0.1 mL, 102.5 EID50/0.1 mL, 102.5 EID50/0.1 mL and 103.5 EID50/0.1 mL, respectively. At three weeks p.v., the mean HI antibodies titers against the commercial H9 subtype HI test antigen (CK/SH/10/2001) in 4 groups of vaccinated chickens ranged from 9.4 log2 to 11 log2, while the mean HI antibodies titers against challenge virus in 4 groups of vaccinated chickens ranged from 4.6 log2 to 10.8 log2, and the significant differences of HI antibodies titers were observed among different vaccine groups, for the maximum difference of mean HI antibodies titers were 64-fold among them. The mean NT antibodies titers against challenge virus in 4 groups of vaccinated chickens ranged from 6.7 log2 to 12.2 log2, while the maximum difference of mean HI antibodies titers were 32-fold among them, and the HI antibody and NT antibody of the control group were negative. After intranasal infection with different H9 viruses, the immune effects of the four vaccines were quite different. In CK/XJ/S1204/2015 challenged groups, 3 vaccines (B-D) could provide more than 80% protection. In DK/JX/S4512/2017 challenged groups, 1 vaccine (B) could provide more than 80% protection. In CK/YN/S1666/2020 challenged groups, 2 vaccines (A and B) could provide more than 80% protection. In CK/NX/S4590/2020 challenged groups, the protection efficacy of the four vaccines (A-D) were all less than 80%. In the same period, the virus shedding rate of chickens under the control group was more than 8/10. 【Conclusion】 There was a great difference in the immune protection efficacy of the four kinds of commercial vaccines after challenge with recently isolated H9 strains, and the difference of antigenicity between vaccine antigens and isolates was the main reason for the decrease of immune protection efficacy of the commercial vaccines. The titers of HI antibody and NT antibody against H9N2 prevalent strains could be as important data for evaluation of the commercial H9N2 AI vaccines. This study provided the scientific references for selection and usage of the commercial vaccines against H9N2 AI.

Key words: H9N2 subtype, AIV, commercial vaccine, protective efficacy, avian influenza

Table 1

The EID50, CID50 and TCID50 of the four H9N2 avian influenza viruses"

攻毒毒株 Virus 鸡胚半数感染量 EID50 鸡半数感染量 CID50 细胞半数感染量 TCID50
CK/XJ/S1204/2015 10-8.5/0.1 mL 103.5 EID50/0.1 mL 10-6.5/0.1 mL
DK/JX/S4512/2017 10-8.63/0.1 mL 102.5 EID50/0.1 mL 10-7.5/0.1 mL
CK/YN/S1666/2020 10-8.94/0.1 mL 102.5 EID50/0.1 mL 10-6.5/0.1 mL
CK/NX/S4590/2020 10-8.83/0.1 mL 103.5 EID50/0.1 mL 10-7.5/0.1 mL

Fig. 1

The HI antibody titers in groups of chickens immunized with different vaccines at 3 weeks post immunization"

Fig. 2

The NT antibody titers to challenge virus in groups of chickens immunized with different vaccines before challenge study"

Table 2

The results of virus shedding in the groups of chickens immunized with different vaccine after challenge"

攻毒毒株
Virus		 疫苗编号
Vaccine
number		 攻毒后3 d和5 d各组鸡排毒结果：排毒数/总数（Log10EID50/mL）
Virus shedding detection on days 3 and 5 post challenge(p.c.)
No. of chickens shedding virus/Total chickens (Log10EID50/mL)		 保护率
Protection
ratio
3 d 5 d
喉头 Oropharynx 泄殖腔 Cloaca 喉头 Oropharynx 泄殖腔 Cloaca
CK/XJ/S1204/2015 A 5/10（2.9） 3/10（3.3） 9/10（3.3） 3/10（2.1） 10%
B 0/10 0/10 2/10（2.9） 0/10 80%
C 2/10（2.9） 0/10 0/10 0/10 80%
D 0/10 0/10 1/10（3.0） 0/10 90%
PBS 10/10（4.3） 0/10 10/10（3.1） 5/10（3.0） /
DK/JX/S4512/2017 A 5/10（3.7） 0/10 10/10（4.9） 7/10（3.2） 0
B 0/10 0/10 0/10 0/10 100%
C 4/10（4.6） 3/10（2.3） 9/10（4.2） 7/10（3.1） 10%
D 3/10（4.9） 1/10（1.3） 10/10（4.6） 10/10（3.2） 0
PBS 10/10（5.9） 9/10（3.1） 10/10（5.0） 10/10（3.2） /
CK/YN/S1666/2020 A 0/10 0/10 0/10 0/10 100%
B 0/10 0/10 0/10 0/10 100%
C 10/10（5.5） 6/10（2.9） 7/10（4.9） 7/10（2.4） 0
D 3/10（4.5） 1/10（3.3） 6/10（5.5） 2/10（2.8） 40%
PBS 10/10（6.1） 8/10（2.9） 10/10（6.5） 9/10（3.1） /
CK/NX/S4590/2020 A 10/10（4.8） 4/10（2.4） 10/10（5.5） 9/10（3.1） 0
B 4/10（4.8） 2/10（2.4） 9/10（5.3） 4/10（3.2） 10%
C 10/10（4.9） 3/10（2.4） 10/10（5.4） 8/10（2.9） 0
D 8/10（4.7） 2/10（2.4） 10/10（5.5） 8/10（3.0） 0
PBS 10/10（6.3） 6/10（2.5） 10/10（6.6） 6/10（3.8） /

Table 3

Correlation between mean antibody titers and protective efficacy of commercial H9 AI vaccine in chickens"

疫苗编号
Vaccine number		 攻毒毒株
Challenge virus		 HI抗体效价
HI antibody titers
n=6（log2）		 中和抗体
NT antibody titers
n=6（log2）		 保护率
Protection ratio
CK/SH/10/2001 攻毒毒株 Challenge virus 攻毒毒株 Challenge virus
A CK/XJ/S1204/2015 9.3 9.3 8.9 10%
DK/JX/S4512/2017 10.2 5.3 6.7 0
CK/YN/S1666/2020 10.0 8.0 10.9 100%
CK/NX/S4590/2020 10.2 6.3 8.3 0
B CK/XJ/S1204/2015 10.2 10.2 11.1 80%
DK/JX/S4512/2017 9.8 9.8 10.0 100%
CK/YN/S1666/2020 10.3 10.8 12.2 100%
CK/NX/S4590/2020 9.3 8.6 8.4 10%
C CK/XJ/S1204/2015 9.5 9.5 10.0 80%
DK/JX/S4512/2017 10.5 8.0 8.8 10%
CK/YN/S1666/2020 9.5 4.6 7.6 0
CK/NX/S4590/2020 9.3 5.1 7.0 0
D CK/XJ/S1204/2015 10.8 10.8 10.9 90%
DK/JX/S4512/2017 11.0 7.0 8.4 0
CK/YN/S1666/2020 9.8 7.5 8.4 40%
CK/NX/S4590/2020 10.2 6.8 8.6 0

Table 4

Cross-reactive HI antibody titers of four H9 viruses with different antisera"

病毒
Virus		 血清交叉抗体滴度 Cross-reactive HI antibody titers of different antisera (log2)
CK/SH/10/2001 CK/XJ/S1204/2015 DK/JX/S4512/2017 CK/YN/S1666/2020 CK/NX/S4590/2020
CK/SH/10/2001 1024 256 256 64 64
CK/XJ/S1204/2015 256 256 32 16 32
DK/JX/S4512/2017 32 64 2048 128 64
CK/YN/S1666/2020 64 128 512 512 512
CK/NX/S4590/2020 64 128 256 128 512
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