The TLR2 agonists lipoteichoic acid and Pam3CSK4 induce greater pro-inflammatory responses than inactivated Mycobacterium butyricum.

The innate immune system can recognize pathogen-associated molecular patterns (PAMP) through toll-like receptors (TLRs). TLR stimulation by TLR-ligands (TLR-L) induces several genes that can regulate the immune response. In this study, we compared the ability of diverse TLR2-L to activate professional antigen presenting cells (pAPCs). We found that in comparison to whole non-replicating microorganism Mycobacterium butyricum, the smaller components; lipoteichoic acid and Pam3CSK4 significantly enhanced the expression of several pro-inflammatory mediators. These included IL-6, TNF-α and nitric oxide both at the mRNA and the protein levels. Moreover, the higher response was associated with a differential activation of nuclear transcription factor kappa-B (NF-κB) by the diverse TLR2-L. However, all three ligands enhanced antigen cross-presentation and T cell induction after virus infection to the same extent. In conclusion, the data highlight the potential for small components of TLR agonists to induce superior inflammatory immune responses than whole microbial preparation in the field of vaccine studies.