BACKGROUND Porcine β-defensin 2 (PBD-2), produced by host cells, is an antimicrobial cysteine-rich cationic peptide with multi-functions. Previous studies have demonstrated that PBD-2 can kill various bacteria, regulate host immune responses and promote growth of piglets. However, the antiviral role of PBD-2 is rarely investigated. This study aimed to reveal the antiviral ability of PBD-2 against pseudorabies virus (PRV), the causative pathogen of Aujeszky's disease, in PK-15 cells and in a PBD-2 expressing transgenic (TG) mouse model. METHODS In this study, the cytotoxicity of PBD-2 on PK-15 cells was measured by CCK-8 assay. PK-15 cells were incubated with PRV pre-treated with different concentrations of PBD-2 and PRV titers in cell culture supernatants were determined by real-time quantitative PCR (RT-qPCR). TG mice and wild-type (WT) mice were intraperitoneally injected with PRV and the survival rate was recorded for 10 days. Meanwhile, tissue lesions in brain, spleen and liver of infected mice were observed and the viral loads of PRV in brain, liver and lung were analyzed by RT-qPCR. RESULTS PBD-2 at a maximum concentration of 80 μg/mL displayed no significant cytotoxicity on PK-15 cells. A threshold concentration of PBD-2 at 40 μg/mL was required to inhibit PRV proliferation in PK-15 cells. The survival rate in PBD-2 TG mice was 50% higher than that of WT mice. In addition, TG mice showed alleviated tissue lesions in brain, spleen and liver compared with their WT littermates after PRV challenge, while viral loads of PRV in brain, liver and lung of TG mice were significantly lower than that of WT mice. CONCLUSIONS PBD-2 could inhibit PRV proliferation in PK-15 cells and protect mice from PRV infection, which confirmed the antiviral ability of PBD-2 both in vitro and in vivo. The application of PBD-2 in developing anti-viral drugs or disease-resistant animals can be further investigated.

中文翻译：

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猪β-防御素2在体外和转基因小鼠中均抑制伪狂犬病病毒的增殖。

背景技术由宿主细胞产生的猪β-防御素2（PBD-2）是一种富含抗菌半胱氨酸的多功能阳离子肽。先前的研究表明，PBD-2可以杀死各种细菌，调节宿主的免疫反应并促进仔猪的生长。但是，很少研究PBD-2的抗病毒作用。这项研究旨在揭示PBD-2在PK-15细胞和表达PBD-2的转基因（TG）小鼠模型中对伪狂犬病病毒（Aujeszky病的致病菌）的抗病毒能力。方法采用CCK-8法检测PBD-2对PK-15细胞的细胞毒性。将PK-15细胞与用不同浓度的PBD-2预处理的PRV孵育，并通过实时定量PCR（RT-qPCR）确定细胞培养上清液中的PRV滴度。TG小鼠和野生型（WT）小鼠腹膜内注射PRV，记录10天的存活率。同时，观察了感染小鼠脑，脾和肝的组织损伤，并通过RT-qPCR分析了PRV在脑，肝和肺中的病毒载量。结果最大浓度为80μg/ mL的PBD-2对PK-15细胞没有明显的细胞毒性。为了抑制PRV在PK-15细胞中的增殖，需要40μg/ mL的PBD-2阈值浓度。PBD-2 TG小鼠的存活率比WT小鼠高50％。此外，TG小鼠在PRV攻击后比WT同窝小鼠的大脑，脾脏和肝脏组织损伤减轻，而TG小鼠在脑，肝和肺中PRV的病毒载量显着低于WT小鼠。结论PBD-2可以抑制PR-15在PK-15细胞中的增殖，并保护小鼠免受PRV感染，这证实了PBD-2在体内外均具有抗病毒能力。可以进一步研究PBD-2在开发抗病毒药物或抗病动物中的应用。