Shi Kaichuang, Li Huanrong, Guo Xin, Ge Xinna, Jia Hong, Zheng Shijun, Yang Hanchun
Key Laboratory of Preventive Veterinary Medicine of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Haidian District, Beijing, China.
Vet Microbiol. 2008 Jun 22;129(3-4):367-77. doi: 10.1016/j.vetmic.2007.11.020. Epub 2007 Nov 29.
Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) are pathogens, which can significantly affect the swine industry worldwide. Field surveys suggest that simultaneous PRRSV and PCV2 infection is common in pigs. The objective of this study was to measure the changes in peripheral blood leukocyte subpopulations in piglets co-infected experimentally with PRRSV and PCV2, in order to analyze the synergistic influence of co-infection on the immune system. Changes in peripheral blood leukocyte subpopulations were systematically measured by flow cytometry (FCM). The levels of antibodies to PRRSV and PCV2 were detected by indirect Enzyme-Linked ImmunoSorbent Assay (ELISA) and the indirect fluorescent antibody test (IFA), respectively. Serum viral loads were measured using real-time PCR. The results showed that piglets co-infected with PRRSV and PCV2 exhibited slower generation and lower levels of antibodies to PRRSV and PCV2, and increased amounts and a prolonged presence of both PRRSV and PCV2 in serum, in comparison to the piglets infected with either virus alone. The major finding in our study was that the total and differential leukocyte counts, including white blood cells (WBCs), monocytes, granulocytes and lymphocytes (T, B and NK cells, as well as T-cell subpopulations), dramatically decreased early during co-infection with PRRSV and PCV2 for about two weeks, in contrast with animals singly infected with either PRRSV or PCV2. These results suggest that PRRSV and PCV2 co-infection results in a synergistic decrease in immune cells in the peripheral blood of piglets. These data contribute to the understanding of the immunosuppressive effects resulting from PRRSV and PCV2 co-infection in pigs.
猪繁殖与呼吸综合征病毒（PRRSV）和猪圆环病毒2型（PCV2）是可对全球养猪业产生重大影响的病原体。现场调查表明，PRRSV和PCV2同时感染在猪群中很常见。本研究的目的是测定实验性同时感染PRRSV和PCV2的仔猪外周血白细胞亚群的变化，以分析共同感染对免疫系统的协同影响。通过流式细胞术（FCM）系统地测定外周血白细胞亚群的变化。分别采用间接酶联免疫吸附测定（ELISA）和间接荧光抗体试验（IFA）检测PRRSV和PCV2的抗体水平。使用实时PCR测定血清病毒载量。结果表明，与单独感染任一病毒的仔猪相比，同时感染PRRSV和PCV2的仔猪对PRRSV和PCV2的抗体产生较慢且水平较低，血清中PRRSV和PCV2的含量增加且持续存在时间延长。我们研究的主要发现是，与单独感染PRRSV或PCV2的动物相比，在同时感染PRRSV和PCV2的早期约两周内，包括白细胞（WBC）、单核细胞、粒细胞和淋巴细胞（T、B和NK细胞以及T细胞亚群）在内的白细胞总数和分类计数显著下降。这些结果表明，PRRSV和PCV2共同感染导致仔猪外周血免疫细胞协同减少。这些数据有助于理解PRRSV和PCV2共同感染猪所产生的免疫抑制作用。
