疫苗的第三次革命—核酸疫苗

在预防疾病的各种手段中,免疫预防是一种比较方便、有效和经济的措施.继第一、二代疫苗实践应用后,核酸疫苗以其特有的可诱导机体产生全面的免疫应答,对不同亚型的病原体具有交叉防御作用以及安全、可靠、生产方便等优点被称之为"疫苗的第三次革命".     

自杀性DNA疫苗

基因疫苗与传统疫苗相比,具有许多优势:比较稳定,便于保存和运输;将抗原以天然的形式提供给免疫系统,可同时引起全面的体液免疫和细胞免疫应答;对不同亚型的病原体有交叉抵抗作用,没有减毒活疫苗毒力回复的危险性等。基因疫苗一出现,就受到普遍关注,迅速成为疫苗研究领域的一大     

Titration of Marek's disease cell-associated vaccine virus (CVI 988) of reconstituted vaccine and vaccine ampoules from Dutch hatcheries

Thirty-one outbreaks of Marek's disease (MD) were reported in the Netherlands and retrospectively analyzed. The outbreaks occurred mostly in vaccinated commercial layer and a few breeder flocks of several breeds; however, the cause of the outbreaks could not be established. Therefore, in a prospective study, the occurrence of true vaccine failures was assessed onfive hatcheries. The plaque-forming units (PFU) of MD vaccine per chicken dose were determined through in vitro assays on vacine ampoules (2 to 5 per hatchery) and samples of reconstituted vaccine (approximately 22 per hatchery). All forty reconstituted vaccine samples of hatcheries 1 and 4 showed PFU doses <10(3). In hatchery 4, 14 samples showed extreme low PFU (< or = 10 PFU). In hatcheries 2, 3, and 5, the numbers of MD vaccine suspensions with a titer > or = 10(3) PFU, which is the standard required, were 1 (5%), 17 (77%), and 3 (14%), respectively. Some vaccine ampoules showed < 10(3) PFU per chicken dose. This study shows the usefulness to assess the PFU per chicken dose of reconstituted MD vaccine and vaccine ampoules to unravel true vaccine failures, which could result in disease outbreaks in the field.