Bhatia S, Khandia R, Sood R, Bhat S, Siddiqui A, Jahagirdhar G, Mishra S, Mishra A, Pateriya A K, Kulkarni D D
ICAR-National Institute of High Security Animal Diseases, Bhopal, Madhya Pradesh, 462022, India.
ICAR-National Institute of High Security Animal Diseases, Bhopal, Madhya Pradesh, 462022, India.
Microb Pathog. 2016 Aug;97:172-7. doi: 10.1016/j.micpath.2016.06.011. Epub 2016 Jun 11.
An inactivated vaccine was developed using the rgH5N2 virus (6 + 2 reassortant) generated by plasmid based reverse genetics system (RGS) with WSN/33/H1N1 as backbone virus. Following mutation of the basic amino acid cleavage site RRRKKRGLF to IETRGLF, the H5-HA (haemagglutinin) gene of the selected donor H5N1 virus (A/chicken/West Bengal/80995/2008) of antigenic clade 2.2 was used along with the N2-NA gene from H9N2 field isolate (A/chicken/Uttar Pradesh/2543/2004) for generation of the rgH5N2 virus. A single dose (0.5 ml/bird) of the inactivated rgH5N2 vaccine protected 100% of the vaccinated chickens (n = 10) on 28(th) dpv (early challenge) and 90% of the vaccinated chickens (n = 10) on 200(th) dpv (late challenge) against high dose challenge with HPAI virus (10(9) EID50/bird). Challenge virus shedding via oropharynx and cloaca of the vaccinated chickens was detectable by realtime RT-PCR during 1-5 dpc and 1-9 days dpc in the early and the late challenge, respectively. The protective level of antibodies (mean HI titre > 128) was maintained without booster vaccination for 200 days. The present study provides the experimental evidence about the extent of protection provided by a reverse genetics based vaccine for clade 2.2 H5N1 viruses against challenge with high dose of field virus at two different time points (28 dpv and 200 dpv). The challenge study is uniquely different from the previous similar experiments on account of 1000 times higher dose of challenge and protection at 200 dpv. The protection and virus shedding data of the study may be useful for countries planning to use H5 vaccine in poultry especially against the clade 2.2 H5N1 viruses.
一种灭活疫苗是利用基于质粒的反向遗传学系统（RGS），以WSN/33/H1N1作为骨架病毒产生的rgH5N2病毒（6 + 2重配株）研制而成。在将碱性氨基酸裂解位点RRRKKRGLF突变为IETRGLF后，使用抗原性2.2分支的选定供体H5N1病毒（A/鸡/西孟加拉邦/80995/2008）的H5-HA（血凝素）基因以及来自H9N2田间分离株（A/鸡/北方邦/2543/2004）的N2-NA基因来产生rgH5N2病毒。单剂量（0.5毫升/只）的灭活rgH5N2疫苗在接种后28天（早期攻毒）能保护100%的接种鸡（n = 10），在接种后200天（晚期攻毒）能保护90%的接种鸡（n = 10）免受高剂量高致病性禽流感病毒（10⁹ EID₅₀/只）的攻毒。在早期攻毒的1 - 5天和晚期攻毒的1 - 9天期间，通过实时RT-PCR可检测到接种鸡经口咽和泄殖腔排出的攻毒病毒。在不进行加强免疫的情况下，抗体保护水平（平均血凝抑制效价>128）维持了200天。本研究提供了实验证据，表明基于反向遗传学的疫苗对2.2分支H5N1病毒在两个不同时间点（接种后28天和200天）抵御高剂量田间病毒攻毒所提供的保护程度。该攻毒研究与之前的类似实验有独特的不同之处，在于攻毒剂量高1000倍且在接种后200天有保护作用。该研究的保护和病毒排出数据可能对计划在家禽中使用H5疫苗，尤其是针对2.2分支H5N1病毒的国家有用。
