Ostanello F, Caprioli A, Di Francesco A, Battilani M, Sala G, Sarli G, Mandrioli L, McNeilly F, Allan G M, Prosperi S
Department of Veterinary Public Health and Animal Pathology, Faculty of Veterinary Medicine, Bologna University, Via Tolara di Sopra 50, 40064 Ozzano Emilia (BO), Italy.
Vet Microbiol. 2005 Jul 1;108(3-4):179-86. doi: 10.1016/j.vetmic.2005.04.010.
This report describes an experimental infection with porcine circovirus type 2 (PCV2) in combination with porcine parvovirus (PPV) in 3-week-old conventional colostrum-fed pigs with maternal antibodies to both viruses. Two groups of four pigs each were inoculated with PCV2 and PPV. One of the groups received also a commercial inactivated vaccine against porcine pleuropneumonia to evaluate possible effects of the stimulation of the immune system of pigs on the infection. Another group of four pigs was kept as uninfected control. Clinical signs, rectal temperatures and body weights were recorded. Serum antibody titers to PCV2 and PPV were determined at weekly intervals. Pigs were killed 42 days after inoculation and tissue samples were examined for the presence of gross and microscopic lesions. Tissues were also analyzed for the presence of PCV2 and PPV DNA by PCR, and for the presence of PCV2 antigen by immunohistochemistry (IHC). All the pigs had serum antibodies to PCV2 and PPV at the beginning of the trial. None of them developed clinical symptoms or pathological lesions typical of post-weaning multisystemic wasting syndrome (PMWS), a disease associated to PCV2 infection. However, IHC and/or PCR analyses showed that clinically silent PCV2 infection developed in five of the eight inoculated pigs, regardless of the administration of the vaccine. In particular, PCV2 DNA and/or antigen were detected in most of the tissues examined in the two pigs with the lowest titer of maternal PCV2 antibodies at the beginning of the trial. PPV DNA was not detected in any of the samples examined. The five pigs with PCR and/or IHC evidence of PCV2 infection had a mean weight gain during the experiment lower than that of the inoculated PCR-negative pigs considered together and that of the control pigs. In conclusion, it would appear that passive immunity against PCV2 can play a role in preventing the development of PMWS, but is not able to prevent the establishing of clinically silent PCV2 infections. The dissemination and persistence of the virus in the tissues may depend on the level of PCV2 antibodies at the time of inoculation.
本报告描述了在3周龄、食用初乳的传统饲养猪中，对同时具有两种病毒母源抗体的猪进行猪圆环病毒2型（PCV2）与猪细小病毒（PPV）的联合实验性感染。两组猪，每组4头，接种PCV2和PPV。其中一组还接种了一种商业化的猪传染性胸膜肺炎灭活疫苗，以评估刺激猪免疫系统对感染可能产生的影响。另一组4头猪作为未感染对照。记录临床症状、直肠温度和体重。每周测定血清中针对PCV2和PPV的抗体滴度。接种后42天处死猪，检查组织样本的大体和微观病变。还通过聚合酶链反应（PCR）分析组织中PCV2和PPV DNA的存在情况，并通过免疫组织化学（IHC）检测PCV2抗原的存在情况。试验开始时，所有猪都有针对PCV2和PPV的血清抗体。它们均未出现断奶后多系统消耗综合征（PMWS，一种与PCV2感染相关的疾病）的典型临床症状或病理病变。然而，免疫组织化学和/或聚合酶链反应分析表明，无论是否接种疫苗，8头接种猪中有5头发生了无症状的PCV2感染。特别是，在试验开始时母源PCV2抗体滴度最低的两头猪的大部分检测组织中，检测到了PCV2 DNA和/或抗原。在所检测的任何样本中均未检测到PPV DNA。5头有PCV2感染的聚合酶链反应和/或免疫组织化学证据的猪在实验期间的平均体重增加低于接种后聚合酶链反应阴性猪的总体平均体重增加以及对照猪的平均体重增加。总之，似乎针对PCV2的被动免疫在预防PMWS的发生中可能起作用，但不能预防无症状PCV2感染的建立。病毒在组织中的传播和持续存在可能取决于接种时PCV2抗体的水平。
