Porcine circovirus type 2 (PCV2) is an important pathogen of the current pig industry. The Wnt signalling pathway plays an important role in the growth of young animals. In this study, we mainly elucidated the relationship between PCV2 and the Wnt signalling pathway. In an in vivo experiment in mice, we demonstrated the downregulatory effects of PCV2 infection on expression levels of downstream components of the Wnt signalling pathway. Weight loss in mice was reversed by activating the Wnt signalling pathway, and the body weight was still significantly higher than that in mice infected with PCV2. We detected levels of growth hormone (GH) in the liver and sera, which showed that GH was also downregulated in mice challenged with PCV2. Lithium chloride, the activator of Wnt signalling, upregulated GH, albeit to a significantly lesser degree than that in corresponding non-stimulated mock mice. In vitro studies showed that PCV2 infection downregulated protein expression of β-catenin and mRNA expression of matrix metallopeptidase-2 (Mmp2), downregulated protein expression of β-catenin in the cytoplasm and nucleus, and reduced the activity of the TCF/LEF promoter, demonstrating that PCV2 inhibited activation of the Wnt signalling pathway in vitro. Finally, we found that Rep protein of PCV2 might be responsible for the inhibitory effect.

猪圆环病毒2型（PCV2）是当前养猪业的重要病原体。Wnt信号通路在年幼动物的生长中起重要作用。在这项研究中，我们主要阐明了PCV2与Wnt信号通路之间的关系。在体内在小鼠的实验中，我们证明了PCV2感染对Wnt信号通路下游成分表达水平的下调作用。通过激活Wnt信号通路可以逆转小鼠的体重减轻，体重仍然明显高于感染PCV2的小鼠。我们检测到肝脏和血清中的生长激素（GH）水平，这表明GH在受PCV2攻击的小鼠中也被下调。Wnt信号的激活剂氯化锂上调了GH，尽管其程度明显低于相应的非刺激模拟小鼠。体外研究表明PCV2感染下调了β-catenin的蛋白表达和基质金属肽酶2（Mmp2），下调β-catenin在细胞质和细胞核中的蛋白表达，并降低TCF / LEF启动子的活性，表明PCV2在体外抑制Wnt信号通路的激活。最后，我们发现PCV2的Rep蛋白可能是抑制作用的原因。