TLR-Mediated Host Immune Response to Parasitic Infectious Diseases

Abstract

Toll-like receptors (TLRs) are important for the host immune response to a variety of pathogens, including bacteria, viruses, fungi, and parasites. These receptors become activated upon recognizing pathogen-associated molecular patterns (PAMPs) and thus initiate the innate immune response to the corresponding pathogen. A key aspect of TLRs is their activation of signaling that leads to cytokine production and an inflammatory response. Additionally, TLRs act as the bridge between innate and acquired immunity, enhancing phagocytosis and the process of killing parasites. We herein focus on how parasites (protozoans and helminths) and their derived products have the capability of stimulating or evading the host response by triggering or inhibiting TLR activation. Parasites often develop successful survival strategies that imply interference with the host immune response. Accordingly, many of these organisms have molecules that modulate inflammation and other aspects of host immunity. Taking advantage of such mechanisms, there are some anti-inflammatory therapies based on human infection with helminths. Helminths and protozoans influence the activity of various TLRs, especially TLR2, TLR4, and TLR9. A better understanding of the role of TLRs and their parasite-derived ligands should certainly provide new therapeutic tools for combatting various parasitic and inflammatory diseases.

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