Toll-like receptor 8 agonists improve NK-cell function primarily targeting CD56^brightCD16^- subset

Area of Science:

• Immunology
• Cell Biology
• Oncology

Background:

• Toll-like receptors (TLRs) are crucial for innate immunity, recognizing pathogen-associated molecular patterns (PAMPs).
• Natural killer (NK) cells express endosomal TLRs, responding to viral and bacterial nucleic acids.
• Understanding NK cell activation via specific TLRs is vital for developing effective cancer immunotherapies.

Purpose of the Study:

• To determine which endosomal TLRs directly mediate NK cell activation and function.
• To identify the optimal TLR agonist for use as an adjuvant in cancer vaccines and immunotherapies.
• To investigate the specific TLR pathway responsible for activating the CD56brightCD16- NK cell subset.

Main Methods:

• Assessed endosomal TLR expression in NK cell subsets (CD56brightCD16- and CD56dimCD16+) using RT-qPCR and western blotting.
• Evaluated NK cell activation markers, cytokine production, and cytotoxicity via flow cytometry and ELISA.
• Analyzed NK cells from ovarian ascites of patients with metastatic ovarian carcinoma.

Main Results:

• Endosomal TLR3, TLR7/8, and TLR9 were expressed on both NK cell subsets.
• TLR7/8 (R848), TLR3 (Poly I:C), and TLR9 (ODN2395) ligands enhanced NK cell function with suboptimal cytokines.
• R848 primarily activated CD56brightCD16- NK cells via TLR8, increasing proliferation, cytokine production, and cytotoxicity, an effect also observed in patient-derived NK cells.

Conclusions:

• TLR8 activation is a key driver of NK cell-mediated anti-tumor responses.
• Targeting TLR8 on NK cells presents a novel strategy for cancer immunotherapy.
• These findings are particularly relevant for treating metastatic ovarian carcinoma.