乙型脑炎减毒活疫苗(SA_(14)-14-2)在豚鼠体内保护作用的免疫机制的研究

本实验将乙脑减毒活疫苗ＳＡ_（１４）－１４－２株以不同疫苗病毒量（３．８７ＰＦＵ／ｍｌ和５．８７ＰＦＵ／ｍｌ）分别一次免疫豚鼠，观察其对强毒攻击后抑制毒血症和抗体形成的能力。结果显示疫苗（５．８７ＰＦＵ／ｍｌ）免疫组豚鼠攻击前虽然中和抗体阴性或很低，但经攻击感染后不同时间内均未出现病毒血症，对照组豚鼠则于第２，３，４天全部出现病毒血症。表明一次活疫苗免疫后能有效地抑制病毒血症的产生。免疫后３０天虽然免疫组的豚鼠中和抗体很低，但攻击感染后抗体迅速增长。第四天的抗体滴度为１：８～３２，第５天达１：１２８～２５６，第１４天抗体高达１：５１２～１０２４；而对照组抗体则上升很慢，第７天才出现低水平抗体（１：４）。血凝抑制抗体增长的动态与中和抗体近似。表明活疫苗免疫后虽然中和抗体水平不高，但一经感染可迅速产生高滴度抗体达到保护作用。

Protective Effect and Dynamic of Antibody Response of Guinea Pigs Immunized with Japanese Encephalitis Attenuated Live Vaccine after Challenged with Virulent Virus

In this study, guinea pigs were used as animalmodel for studying protective mechanism of Japanese Encephalitis(JE) attenuated live vaccine. We found out guinea pigs didn' get disease after infected with wild JE virus (P3strain) but virus coula propagate inthem and viremia appeared.Viremia last at least 4 days, the virus titer reached to 3. OlogPFU/ml. However viremia did not appear in those animals immunized with vaccine affter challenged with virulent JE virus (P3 strain), eoenthough noor low neutralizing antibody(NT) existed pre-challenge. It is interesting that gguinea pigs of control group appeared NT-Ab slowlybegining on day 7 woth low titer (1: 4) after challenging,while NT-Ab of the immunized guinea pigs increased rapidly on day 4(titer 1 : 8-32), and reacbed to a high titer on day 5(1 : 128-256), day 14(1 : 512-1024). The dynamic of HI antibody induction was similar to that of NT-Ab. This results indicate that althouggh NT-Ab in the immunized guinea pigs are negative or very low before infectionthey still have an ability ofinhibiting virusmultiplication. The rapid NT-Ah induction to a high level might be an important role for protection of JE illness.