Pathogenesis of BSE and highly sensitive isolation of BSE agent

疯牛病在英国和欧洲流行的连锁反应以及随后在年轻人和青少年中出现的vCJD引起了人们的关注，并强调了在食物链中进行风险评估的重要性。近年来，人们开发了几种高灵敏度的先验检测方法。其中的代表是PMCA。PMCA最初是由Claudio Soto和他的同事开发的，在世界各地的朊病毒会议上一直是争论的热门话题。现在，广泛的PrP^Sc物种已经使用PMCA成功扩增，包括CWD，小鼠适应痒病和疯牛病。对人类散发性和变异型CJD病例的研究表明，PMCA扩增效率受到密码子129处PrP^C底物基因型的严格控制。PMCA似乎比在体内更快地克服了跨物种传播过程中遇到的物种障碍。通过使用较低稀释度的PrP^Sc种子和更多的扩增轮来“强制”这项技术，小鼠Chandler PrP^Sc现在可以转化仓鼠PrP^C或子鼠PrP^C，这种转化可能在体内观察到，但需要极长的潜伏期。Castilla J.表明，利用PMCA， PrP^Sc从11个不同物种的健康大脑中产生，包括田鼠、小鼠、牛、人类、绵羊和兔子，产生了各种电泳图谱。PMCA能够在无症状朊病毒感染小鼠的血液中检测到1 μL的PrP^Sc。鉴于越来越多的证据表明通过血液制品人际传播，科学家们正在等待将PMCA纳入一种可靠的检测方法，以便能够识别无症状携带者的献血者。扩增技术的进一步发展是值得期待的，重组PrP作为底物取代PrP^C，以及使用间歇震动而不是超声，应该可以在不久的将来规避一些困难。

The chain reaction of BSE epidemics in the UK and Europe and subsequent emergence of vCJD in young adults and teenagers have raised concerns and highlighted the importance of risk assessment in the food chain. Recently, several highly sensitive methods for detecting priors have been developed. Representative of these is PMCA.Originally developed by Claudio Soto and his colleagues, PMCA has been a hot topic of debate in prion meetings all over the world. A broad spectrum of PrP^Sc species have now been successfully amplified using PMCA, including CWD, mouse-adapted scrapie, and BSE. Studies with human sporadic and variant CJD cases show that PMCA amplification efficiency is tightly controlled by the PrP^C substrate genotype at codon 129. PMCA appears to overcome the species barrier encountered during cross-species transmission more rapidly than in vivo. By "forcing" the technique with lower dilutions of the PrP^Sc seed and more amplification rounds, mouse Chandler PrP^Sc can now convert hamster PrP^C or cervid PrP^C, a conversion that might be observable in vivo but only with extremely long incubation periods. Castilla J. showed that using PMCA, PrP^Sc was generated from the healthy brains of 11 different species, including bank voles, mice, cattle, humans, sheep and rabbits, generating a variety of electrophoretic profiles. PMCA was able to detect PrP^Sc in as little as 1 μL of blood from an asymptomatic prion-infected mouse. Given the increasing evidence of human to human transmission via blood products, scientists are waiting for PMCA to be incorporated into a reliable test with the ability to identify blood donors that are asymptomatic carriers. Further advances in amplification technology are to be expected and the replacement of PrP^C by recombinant PrP as a substrate as well as the use of intermittent shaking rather than sonication should circumvent some of the difficulties in the near future.