Evasion of the Host Innate Immune System by Pathogenic Bacteria

Bacterial pathogens have evolved clever strategies to manipulate host immune responses to their advantage. They employ various mechanisms to evade bacterial clearance by the host, leading to persistent and sometimes life-threatening infections. Early innate immune responses are critical for the host to develop adaptive immune responses. If these early innate immune responses are suppressed, it can hinder the body’s antibacterial defense, resulting in serious health consequences before adaptive immune responses can take effect. In this overview, we first review our basic knowledge and recent insights into the host’s antibacterial innate immune responses, particularly focusing on pattern recognition receptors, the complement system, and inflammatory responses during the early stages of infection. We then discuss the relevant mechanisms that bacterial pathogens use to threaten human health. We highlight how pathogenic bacteria can maneuver the antibacterial defense system through various tactics, including surface modification to evade host recognition, molecular mimicry, and the production of enzymes to manipulate host cell signaling pathways. Additionally, we explore their strategies for evading complement action and suppressing phagocyte functions. We have selected clinically important and challenging bacteria as examples, including Yersinia, Shigella flexneri, Staphylococcus aureus, Salmonella, Brucella melitensis, Streptococcus, Escherichia coli, Helicobacter pylori, and Pseudomonas aeruginosa. These examples are presented at both the functional and molecular levels. Studying the complex interactions between hosts and pathogens is an exciting research field. Understanding the strategies that bacteria use to evade host innate immune responses opens up promising opportunities to counteract these escape strategies. Ultimately, this research aims to provide innovative treatment approaches to manage challenging bacterial infections. Highlights