Ahmad J, Sharma J M
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Minnesota, St Paul 55108.
Am J Vet Res. 1992 Nov;53(11):1999-2004.
The B1 strain of Newcastle disease virus (NDV-B1), which is nonpathogenic for newly hatched chickens, killed embryos when it was used to inoculate chicken eggs at embryonation day 18. Treatment of NDV-B1 with an alkylating agent, ethylmethane sulfonate (EMS) markedly reduced the pathogenicity of the virus for 18-day-old chicken embryos. Eggs inoculated with the modified virus (NDV-B1-EMS) hatched, and the virus was isolated from lungs and spleen of 1-day-old chickens. The hatched chickens developed antibody to NDV and were protected against challenge exposure (at 4 weeks of age) with a highly virulent GB-Texas strain of NDV. Presence of maternal antibody to NDV in embryonating eggs did not influence the protective ability of NDV-B1-EMS, which also induced protective immunity when administered to 4-week-old chickens. The 50% protective dose of NDV-B1-EMS in maternal antibody-negative and -positive embryos was calculated to be 10.77 and 17.70 embryo 50% lethal doses, respectively. Results of the study indicated that NDV-B1-EMS may be used as an embryo vaccine to protect chickens against Newcastle disease.
新城疫病毒B1株（NDV - B1）对新孵出的雏鸡无致病性，但在胚胎发育第18天用于接种鸡胚时可致死胚胎。用烷化剂甲磺酸乙酯（EMS）处理NDV - B1可显著降低该病毒对18日龄鸡胚的致病性。接种了经修饰病毒（NDV - B1 - EMS）的鸡胚孵化出雏鸡，并且从1日龄雏鸡的肺和脾中分离到了病毒。孵出的雏鸡产生了针对NDV的抗体，并在4周龄时受到高致病性GB - Texas株NDV攻击时得到保护。胚胎期鸡蛋中存在的母源抗NDV抗体不影响NDV - B1 - EMS的保护能力，当给4周龄雏鸡接种时，它也能诱导保护性免疫。计算得出，在母源抗体阴性和阳性胚胎中，NDV - B1 - EMS的50%保护剂量分别为10.77和17.70个鸡胚50%致死剂量。研究结果表明，NDV - B1 - EMS可用作胚胎疫苗来保护鸡抵抗新城疫。
