Genotype-matched vaccines provide ideal protection against infection caused by new Newcastle disease virus (NDV) genotypes or variants even in the vaccinated chickens. In this study, we report a protocol for attenuation and rapid development of a velogenic NDV isolate as an effective vaccine candidate, using a simple and reliable infectious cloning platform. Based on DHN3, a genotype VII velogenic NDV isolate, recombinant rDHN3 was rescued by co-transfection of plasmids expressing the genomic RNA, NDV proteins NP, P and L, and the T7 polymerase without using a helper virus. Subsequently, an attenuated strain rDHN3-mF was produced by substitution of residues from amino acids 112 to 117 in the DHN3 F protein with the corresponding sequence from the LaSota strain. Both rDHN3 and rDHN3-mF are genetically stable during propagation in cell culture and chicken embryos. Further characterization through determination of EID₅₀, MDT and clinical assessments confirmed that rDHN3 is velogenic and rDHN3-mF lentogenic. Vaccination of one-week-old SPF chicks with inactivated rDHN3-mF produced much higher anti-DHN3 antibody response and better protection against live DHN3 challenge than did the commercial LaSota vaccine, providing 100% protection and much earlier viral clearance. This attenuated NDV isolate would merit further development into a vaccine product.

基因型匹配疫苗即使在接种疫苗的鸡中也能提供理想的保护，以防止新的新城疫病毒（NDV）基因型或变异引起的感染。在这项研究中，我们报告了使用简单可靠的感染性克隆平台，减毒和快速开发出速激肽NDV分离物作为有效疫苗候选物的协议。基于DHN3（基因型VII velogenic NDV分离株），重组rDHN3通过共转染表达基因组RNA，NDV蛋白NP，P和L以及T7聚合酶的质粒而无需使用辅助病毒而得以拯救。随后，通过用来自LaSota菌株的相应序列取代DHN3 F蛋白中氨基酸112至117的残基来产生减毒菌株rDHN3-mF。在细胞培养和鸡胚中繁殖期间，rDHN3和rDHN3-mF在遗传上均稳定。通过确定EID进一步表征₅₀，MDT和临床评估证实，rDHN3是velogenic的，rDHN3-mF是lentogenic的。与商业LaSota疫苗相比，用灭活的rDHN3-mF接种一周大的SPF雏鸡所产生的抗DHN3抗体反应更高，并且对活的DHN3攻击的保护效果更好，可提供100％的保护并更早地清除病毒。这种减毒的NDV分离株值得进一步发展成为疫苗产品。