Immune Evasion of <i>Mycoplasma bovis</i>

• Main Authors: Hussam Askar, Shengli Chen, Huafang Hao, Xinmin Yan, Lina Ma, Yongsheng Liu, Yuefeng Chu
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Pathogens
• Subjects: <i>Mycoplasma bovis</i>; immune response; exhausted T-cell; infection; immune evasion
• Online Access: https://www.mdpi.com/2076-0817/10/3/297

<i>Mycoplasma bovis (M. bovis)</i> causes various chronic inflammatory diseases, including mastitis and bronchopneumonia, in dairy and feed cattle. It has been found to suppress the host immune response during infection, leading to the development of chronic conditions. Both in vitro and in vivo studies have confirmed that <i>M. bovis</i> can induce proinflammatory cytokines and chemokines in the host. This consists of an inflammatory response in the host that causes pathological immune damage, which is essential for the pathogenic mechanism of <i>M. bovis</i>. Additionally, <i>M. bovis</i> can escape host immune system elimination and, thus, cause chronic infection. This is accomplished by preventing phagocytosis and inhibiting key responses, including the neutrophil respiratory burst and the development of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) that lead to the creation of an extracellular bactericidal network, in addition to inhibiting monocyte and alveolar macrophage apoptosis and inducing monocytes to produce anti-inflammatory factors, thus inducing the apoptosis of peripheral blood mononuclear cells (PBMCs), inhibiting their proliferative response and resulting in their invasion. Together, these conditions lead to long-term <i>M. bovis</i> infection. In terms of the pathogenic mechanism, <i>M. bovis</i> may invade specific T-cell subsets and induce host generation of exhausted T-cells, which helps it to escape immune clearance. Moreover, the <i>M. bovis</i> antigen exhibits high-frequency variation in size and expression period, which allows it to avoid activation of the host humoral immune response. This review includes some recent advances in studying the immune response to <i>M. bovis</i>. These may help to further understand the host immune response against <i>M. bovis</i> and to develop potential therapeutic approaches to control <i>M. bovis</i> infection.