Dampened TLR2-mediated Inflammatory Signaling in Bats

Area of Science:

• Immunology
• Virology
• Evolutionary Biology

Background:

• Bats are natural reservoirs for diverse viruses, capable of carrying pathogens without succumbing to illness.
• Toll-like receptor 2 (TLR2) is crucial for innate immunity, recognizing pathogen patterns and initiating inflammatory responses.
• Dysregulated TLR2 signaling can lead to excessive inflammation and self-damage, while moderate signaling aids pathogen clearance.

Purpose of the Study:

• To investigate the evolutionary adaptations of Toll-like receptor 2 (TLR2) in bats.
• To understand the functional consequences of TLR2 variations in bats concerning immune signaling.
• To explore the link between dampened TLR2 responses and the ability of bats to host viruses.

Main Methods:

• Comparative genomic analysis of TLR2 across bat species and other mammals.
• Site-directed mutagenesis to identify key residues in bat TLR2.
• Cell-based assays to assess TLR2 heterodimerization and downstream inflammatory signaling.

Main Results:

• TLR2 has undergone relaxed evolutionary selection in bats compared to other mammals.
• Bat TLR2 exhibits significantly reduced binding affinity with TLR1 and TLR6, leading to dampened inflammatory signaling.
• Specific mutations, present in the bat common ancestor, were identified as responsible for reduced TLR2-mediated inflammation.

Conclusions:

• The inflammatory response mediated by TLR2 is specifically dampened in bats.
• This evolutionary adaptation in TLR2 may contribute to bats' unique ability to host numerous viruses without developing disease.
• Reduced TLR2 signaling potentially prevents detrimental self-damage from excessive inflammation in bats.