Zoetis, Veterinary Medicine Research and Development, 1930 Zaventem, Belgium.
Vaccine. 2013 Jun 28;31(31):3126-30. doi: 10.1016/j.vaccine.2013.05.043. Epub 2013 May 23.
Despite effective vaccines against common Leptospira serovars, the development of new products with long duration of immunity is still important to protect dogs against leptospirosis. The results from four challenge studies performed one year after vaccination of dogs with a multivalent vaccine containing four Leptospira antigens are reported. Six week old dogs received two vaccinations, three weeks apart, and were challenged 367 days later. Clinical observations were recorded, while blood (culture, biochemistry and haematology), urine (culture) and liver and kidney (culture) samples were collected throughout the study or at necropsy. All control dogs remained seronegative until challenge, when they seroconverted. Antibody titres to Leptospira antigens were seen in vaccinated dogs 21 days after first vaccination and peaked three to six weeks after the second vaccination. Titres decreased in all studies over the following 12 months, until challenge when anamnestic responses were observed. In all studies control dogs demonstrated various abnormal clinical signs, while no vaccinated dogs were affected; differences between groups were only significant following L. bratislava challenge. Analysis of blood cultures showed all control and five of the 24 vaccinated dogs were Leptospira positive after challenge; all studies showed significant differences between treatment groups in mean number of days with positive cultures. Significant differences between vaccinated and control groups in mean number of days with positive urine cultures were also observed, with all non-vaccinated and one vaccinated dog Leptospira positive. The urine culture positive vaccinated dog also gave positive culture from kidney and liver samples. All except one control dog also showed positive Leptospira isolation from kidney or liver, with significant differences between vaccinated and control groups observed. The results demonstrate that administration of a new vaccine to six week old puppies induces immunity which is still effective up to one year later as demonstrated by challenge.
尽管针对常见钩端螺旋体血清型已有有效的疫苗，但开发具有长期免疫效果的新产品对于保护犬类免受钩端螺旋体病的侵害仍然很重要。本文报道了在接种含有四种钩端螺旋体抗原的多价疫苗一年后进行的四项挑战研究的结果。六周龄的犬接受了两次疫苗接种，间隔三周，然后在 367 天后进行了攻毒。记录临床观察结果，同时在整个研究过程中或在尸检时采集血液（培养、生化和血液学）、尿液（培养）和肝脏和肾脏（培养）样本。所有对照犬在攻毒前均保持血清阴性，攻毒后血清转化。接种疫苗的犬在首次接种后 21 天出现针对钩端螺旋体抗原的抗体滴度，在第二次接种后三至六周达到峰值。在随后的 12 个月中，所有研究中的抗体滴度均下降，直到攻毒时观察到回忆反应。在所有研究中，对照犬均表现出各种异常的临床症状，而接种疫苗的犬则没有受到影响；仅在 L. bratislava 攻毒后，两组之间才有差异。血液培养分析显示，所有对照犬和 24 只接种犬中的 5 只在攻毒后呈钩端螺旋体阳性；所有研究均显示治疗组之间平均阳性培养天数存在显著差异。接种组和对照组之间的尿液培养阳性天数也存在显著差异，所有未接种疫苗的犬和一只接种疫苗的犬均为钩端螺旋体阳性。尿液培养阳性的接种犬的肾脏和肝脏样本也呈阳性培养。除一只对照犬外，所有对照犬的肾脏或肝脏均分离出钩端螺旋体，接种组和对照组之间观察到显著差异。结果表明，向六周龄幼犬接种新疫苗可诱导免疫，攻毒后一年仍有效。
