Department of Microbiology and Plant Pathology, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa.
Vaccine. 2013 Aug 28;31(38):4177-82. doi: 10.1016/j.vaccine.2013.06.089. Epub 2013 Jul 16.
Rabies in dogs can be controlled through mass vaccination. Oral vaccination of domestic dogs would be useful in the developing world, where greater vaccination coverage is needed especially in inaccessible areas or places with large numbers of free-roaming dogs. From this perspective, recent research has focused on development of new recombinant vaccines that can be administered orally in a bait to be used as adjunct for parenteral vaccination. One such candidate, a recombinant canine adenovirus type 2 vaccine expressing the rabies virus glycoprotein (CAV2-RG), is considered a promising option for dogs, given host specificity and safety. To assess the potential use of this vaccine in domestic dog populations, we investigated the prevalence of antibodies against canine adenovirus type 2 in South African dogs. Blood was collected from 241 dogs from the Gauteng and KwaZulu-Natal provinces. Sampled dogs had not previously been vaccinated against canine adenovirus type 1 (CAV1) or canine adenovirus type 2 (CAV2). Animals from both provinces had a high percentage of seropositivity (45% and 62%), suggesting that CAV2 circulates extensively among domestic dog populations in South Africa. Given this finding, we evaluated the effect of pre-existing CAV-specific antibodies on the efficacy of the CAV2-RG vaccine delivered via the oral route in dogs. Purpose-bred Beagle dogs, which received prior vaccination against canine parvovirus, canine distemper virus and CAV, were immunized by oral administration of CAV2-RG. After rabies virus (RABV) infection all animals, except one vaccinated dog, developed rabies. This study demonstrated that pre-existing antibodies against CAV, such as naturally occurs in South African dogs, inhibits the development of neutralizing antibodies against RABV when immunized with a CAV-based rabies recombinant vaccine.
狂犬病可以通过大规模疫苗接种来控制。对家犬进行口服疫苗接种将在发展中国家有用，在这些国家，特别是在难以到达的地区或有大量自由放养犬的地方，需要更高的疫苗接种覆盖率。从这个角度来看，最近的研究集中在开发新的重组疫苗上，这些疫苗可以作为辅助剂通过口服疫苗接种在诱饵中使用。其中一种候选疫苗是表达狂犬病病毒糖蛋白的重组犬腺病毒 2 型疫苗（CAV2-RG），由于宿主特异性和安全性，被认为是犬的一种有前途的选择。为了评估该疫苗在南非家犬中的潜在用途，我们调查了南非犬中抗犬腺病毒 2 的抗体流行率。从豪登省和夸祖鲁-纳塔尔省采集了 241 只狗的血液。采样犬以前未接种过犬腺病毒 1 型（CAV1）或犬腺病毒 2 型（CAV2）疫苗。两个省的动物血清阳性率都很高（分别为 45%和 62%），这表明 CAV2 在南非的家犬中广泛传播。鉴于这一发现，我们评估了预先存在的 CAV 特异性抗体对通过口服途径给予 CAV2-RG 疫苗的效果的影响。目的是饲养的比格犬，它们接受了犬细小病毒、犬瘟热病毒和 CAV 的预先接种，通过口服给予 CAV2-RG 进行免疫。在狂犬病病毒（RABV）感染后，除了一只接种疫苗的狗外，所有动物都患了狂犬病。这项研究表明，南非犬中自然发生的针对 CAV 的预先存在的抗体，当用基于 CAV 的狂犬病重组疫苗免疫时，会抑制针对 RABV 的中和抗体的产生。
