Hussein H A, Ahmed B M, Aly S M, El-Deeb A H, El-Sanousi A A, Rohaim M A, Arafa A A, Gadalla M R
Acta Virol. 2016;60(3):307-15. doi: 10.4149/av_2016_03_307.
In this study, a recombinant DNA plasmid was constructed, encoding for HA1 of a selected Egyptian H5N1 virus (isolated during the 2012 outbreaks). In the immunization and challenge experiments, SPF chickens received 1 or 2 doses of H5-DNA plasmid prime, and boosted with the inactivated H5N2 vaccine. Haemagglutination inhibition (HI) titers, protection levels, and the magnitude of virus shedding were compared to that of the chickens that received either DNA plasmid or inactivated H5N2 vaccine alone. H5N1 virus A/chicken/Egypt/128s/2012 (H5N1) highly pathogenic avian influenza (HPAI) clade 2.2.1/C was used for the challenge. Chickens immunized with 1 or 2 doses of H5-DNA vaccine failed to overcome the challenge with 0% and 10% protection, respectively. Quantitative real-time reverse transcription-PCR revealed virus shedding of 2.2 x 104 PCR copies/ml 3 days post challenge (dpc) in the only surviving bird from the group that received 2 doses of plasmid. However, chickens immunized with 1 or 2 doses of H5-DNA plasmid as prime and inactivated H5N2 vaccine as booster, showed 80% protection after challenge, with a viral shedding of 1.2 x 104 PCR copies/ml (1 dose) and 1.6 x 104 PCR copies/ml (2 doses) 3 dpc. The surviving birds in both groups did not shed the virus at 5 and 7 dpc. In H5N2-vaccinated chickens, protection levels were 70% with relatively high virus shedding (1.8 x 104 PCR copies/ml) 3 dpc. HI titers were protective to the surviving chickens. This study reports the efficacy of H5-DNA plasmid to augment reduction in viral shedding and to provide better protection when applied in a prime-boost program with the inactivated AI vaccine.
在本研究中，构建了一种重组DNA质粒，其编码一种选定的埃及H5N1病毒（于2012年疫情爆发期间分离得到）的HA1。在免疫和攻毒实验中，SPF鸡接受1或2剂H5-DNA质粒初免，并以灭活的H5N2疫苗进行加强免疫。将血凝抑制（HI）效价、保护水平和病毒排毒量与单独接受DNA质粒或灭活H5N2疫苗的鸡进行比较。使用H5N1病毒A/鸡/埃及/128s/2012（H5N1）高致病性禽流感（HPAI）2.2.1/C分支进行攻毒。用1或2剂H5-DNA疫苗免疫的鸡分别以0%和10%的保护率未能抵御攻毒。定量实时逆转录PCR显示，在接受2剂质粒的组中唯一存活的鸡在攻毒后3天（dpc）的病毒排毒量为2.2×10⁴ PCR拷贝/ml。然而，用1或2剂H5-DNA质粒初免并以灭活H5N2疫苗加强免疫的鸡在攻毒后显示出80%的保护率，在攻毒后3 dpc的病毒排毒量分别为1.2×10⁴ PCR拷贝/ml（1剂）和1.6×10⁴ PCR拷贝/ml（2剂）。两组中的存活鸡在5 dpc和7 dpc时均未排毒。在接种H5N2疫苗的鸡中，保护水平为70%，攻毒后3 dpc时病毒排毒量相对较高（1.8×10⁴ PCR拷贝/ml）。HI效价对存活鸡具有保护作用。本研究报告了H5-DNA质粒在与灭活禽流感疫苗联合进行初免-加强免疫方案时，在减少病毒排毒和提供更好保护方面的效果。
