Liver sinusoidal cells eliminate blood-borne phage K1F

Area of Science:

• Microbiology
• Immunology
• Pharmacology

Background:

• Bacteriophage (phage) therapy is a promising alternative to antibiotics for multidrug-resistant bacteria.
• Understanding phage pharmacokinetics, particularly their distribution and clearance in vivo, is crucial for successful phage therapy.
• The liver, a major organ for immune surveillance, is a key site for potential phage sequestration.

Purpose of the Study:

• To investigate the role of liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs) in the clearance of Escherichia coli phage K1Fg10b::gfp (K1F^gfp) following intravenous administration in mice.
• To determine the circulatory half-life, organ distribution, and hepatocellular localization of K1F^gfp.
• To explore the in vitro uptake mechanisms of K1F^gfp by LSECs and KCs, including the effect of opsonization.

Main Methods:

• Intravenous administration of K1F^gfp in mice to assess blood clearance, half-life, and organ distribution.
• Isolation and culture of primary mouse and human LSECs and KCs for in vitro uptake studies.
• Quantification of phage DNA in liver tissues and cultured cells.
• Microscopy and flow cytometry to analyze phage internalization and intracellular trafficking.

Main Results:

• Over 95% of K1F^gfp was cleared from circulation within 20 minutes, with 94% localized to the liver.
• Both KCs and LSECs internalized K1F^gfp, with KCs showing a higher uptake ratio (12:1).
• Opsonization with plasma proteins enhanced phage uptake by both cell types in vitro, and internalized phages were trafficked to lysosomes, where their viability was reduced.

Conclusions:

• Kupffer cells are the primary mediators of rapid bacteriophage clearance from the bloodstream in the liver, with significant contribution from liver sinusoidal endothelial cells.
• Phage opsonization enhances cellular uptake, and intracellular degradation occurs following endocytosis.
• These findings highlight the importance of considering liver sinusoidal cell populations and appropriate dosing strategies for effective intravenous phage therapy.