Lobmann M, Charlier P, Florent G, Zygraich N
Am J Vet Res. 1984 Dec;45(12):2498-503.
A naturally occurring strain of bovine viral diarrhea (BVD) virus was chemically treated to produce a genetically stable, temperature-sensitive mutant, designated RIT 4350. The RIT 4350 strain had a restrictive growth temperature of 39.5 C, so that systemic replication or fetal infection was not detected after parenteral administration in cattle. The RIT 4350 strain was tested as a cell culture-adapted vaccine in healthy heifers, immunodepressed calves, and pregnant cows. In a pathogenicity test in 5 healthy heifers, vaccination with 10 times the field dose resulted in seroconversion, but produced no clinical signs of disease or leukopenia. In a pathogenicity test in immunodepressed calves, 7 test animals were treated with dexamethasone and inoculated with 10 times the field dose. The calves developed mild enteric signs, but virus isolation attempts were negative. Following vaccination, the immunodepressed vaccinated calves were challenge exposed with the Osloss strain of BVD virus; all these vaccinated calves remained healthy. Two of 68 postchallenge serum samples from vaccinated calves were positive for BVD virus, compared with 9 of 20 samples from control calves. In another pathogenicity test, 7 pregnant cows vaccinated with 4 times the field dose seroconverted, remained clinically healthy, and delivered healthy calves.
对一种天然存在的牛病毒性腹泻（BVD）病毒株进行化学处理，以产生一种基因稳定的温度敏感突变株，命名为RIT 4350。RIT 4350株的限制性生长温度为39.5℃，因此在牛经肠胃外给药后未检测到全身复制或胎儿感染。对RIT 4350株作为细胞培养适应疫苗在健康小母牛、免疫抑制犊牛和怀孕母牛中进行了测试。在对5头健康小母牛的致病性试验中，用10倍田间剂量进行疫苗接种导致血清转化，但未产生疾病的临床症状或白细胞减少。在对免疫抑制犊牛的致病性试验中，7只试验动物用 dexamethasone 进行处理，并接种10倍田间剂量。犊牛出现轻度肠道症状，但病毒分离试验结果为阴性。疫苗接种后，对免疫抑制的接种犊牛用BVD病毒的Osloss株进行攻毒；所有这些接种犊牛均保持健康。接种犊牛攻毒后68份血清样本中有2份BVD病毒呈阳性，而对照犊牛的20份样本中有9份呈阳性。在另一项致病性试验中，7头怀孕母牛用4倍田间剂量进行疫苗接种后血清转化，保持临床健康，并产下健康犊牛。
