Acta Veterinaria et Zootechnica Sinica ›› 2020, Vol. 51 ›› Issue (12): 3160-3170.doi: 10.11843/j.issn.0366-6964.2020.12.025

• BASIC VETERINARY MEDICINE • Previous Articles     Next Articles

Evaluation of Therapeutic Effect of Porcine β-defensin-2 on Streptococcus suis Infection

WANG Antian, HUANG Jing, SONG Bingxiao, SUN Yufan, ZHOU Rui, LI Lu*   

  1. The Cooperative Innovation Center for Sustainable Pig Production, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China
  • Received:2020-07-06 Online:2020-12-25 Published:2020-12-23

Abstract: Defensin is a small cationic peptide widely distributed in animals and plants. It is an important component of the innate immune defense system of mammals. It has a broad spectrum of antibacterial, antiviral and antifungal activities. Porcine β-defensin-2 (PBD-2) is one of the natural defensins expressed in pigs and has good antibacterial activity in vitro. The purpose of this study is to evaluate the therapeutic effect of PBD-2 in the treatment of Streptococcus suis infection in animals and to provide more insights for evaluating the value of PBD-2 as a therapeutic drug. Firstly, the bactericidal activity of PBD-2 against S. suis clinical isolate SC-19 was measured in vitro, and the cytotoxicity of PBD-2 was tested on mouse-derived macrophages (RAW264.7). Subsequently, C57 female mice aged 4-6 weeks and weighing between 18-22 g infected with S. suis SC-19 were treated with PBD-2 or PBS (n ≥ 6). The survival rate of mice, and the bacteria loads, inflammatory cytokine levels, and pathological changes of tissues were determined. The results showed that PBD-2 (25-200 μg·mL-1) could significantly inhibit the growth of S. suis SC-19 in a concentration-dependent manner (P<0.05). At the same time, PBD-2 had no significant toxic effect on RAW cells (P>0.05). The in vivo study revealed that PBD-2 treatment could effectively reduce the mortality of mice infected with S. suis SC-19. At the same time, PBD-2 treatment significantly reduced bacteria loads in brain, lung, spleen and blood of mice, and decreased the levels of inflammatory cytokines IL-6, IL-12 and TNF-α in mouse sera (P<0.05). At the same time, PBD-2 treatment also significantly alleviated the degree of pathological damages in lung and spleen tissues of mice infected with bacteria (P<0.05). These results indicate that PBD-2 confers great resilience to S. suis in vitro without significant cytotoxicity, while it also exhibits a therapeutic effect on S. suis infection in mice, suggesting that the use of PBD-2 as a therapeutic drug and substitutes for antibiotics is of an excellent prospect.

Key words: porcine β-defensin-2, bacterial infection, treatment, Streptococcus suis

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