Todd J D
Dev Biol Stand. 1975;28:473-6.
The principal significance of PI-3 virus in the bovine respiratory disease complex would seem to be its role in predisposing the respiratory tract to bacterial infection by (5) disrupting the integrity of the superficial mucosa and (3) producing a more favourable milieu for bacterial growth. Attention has therefore been given to establishing local immunity to preclude infection of superficial cells of the mucosa. Criteria used to evaluate the degree of such immunity are (5) presence of specific antibody activity in nasal secretions and (3) extent of virus excretion in nasal secretions following challenge with low passage virus. Studies completed thus far demonstrate that modified, live PI-3 virus administered intranasally is more effective than either modified, live or inactivated PI-3 virusadministered by parenteral injection in providing antibody activity in respiratory tractsecretions and in reducing virus excretion following challenge. IgA antibodies, presumably synthesized locally, apparently contribute heavily to the total antibody activity present in respiratory tract secretions.
PI - 3病毒在牛呼吸道疾病综合征中的主要意义似乎在于，它通过（5）破坏表层黏膜的完整性以及（3）为细菌生长创造更有利的环境，从而使呼吸道易受细菌感染。因此，人们已将注意力转向建立局部免疫，以防止黏膜表层细胞受到感染。用于评估这种免疫程度的标准是（5）鼻分泌物中特异性抗体活性的存在情况，以及（3）用低代病毒攻击后鼻分泌物中病毒排泄的程度。迄今为止完成的研究表明，经鼻内接种的改良活PI - 3病毒，在提供呼吸道分泌物中的抗体活性以及减少攻击后的病毒排泄方面，比通过肌肉注射接种的改良活PI - 3病毒或灭活PI - 3病毒更有效。推测在局部合成的IgA抗体，显然对呼吸道分泌物中存在的总抗体活性有很大贡献。
