Liver sinusoidal cells eliminate blood-borne phage K1F

Abstract

Phage treatment has regained attention due to an increase in multiresistant bacteria. For phage therapy to be successful, phages must reach their target bacteria in sufficiently high numbers. Blood-borne phages are believed to be captured by macrophages in the liver and spleen. Since liver sinusoids also consist of specialized scavenger liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), this study investigated the contribution of both cell types in the elimination of Escherichia coli phage K1Fg10b::gfp (K1F^gfp) in mice. Circulatory half-life, organ, and hepatocellular distribution of K1F^gfp were determined following intravenous administration. Internalization of K1Fgfp and effects of phage opsonization on uptake were explored using primary mouse and human LSEC and KC cultures. When inoculated with 107 virions, >95% of the total K1F^gfp load was eliminated from the blood within 20 min, and 94% of the total retrieved K1F^gfp was localized to the liver. Higher doses resulted in slower elimination, possibly reflecting temporary saturation of liver scavenging capacity. Phage DNA was detected in both cell types, with a KC:LSEC ratio of 12:1 per population following cell isolation. Opsonization with plasma proteins increased time-dependent cellular uptake in both LSECs and KCs in vitro. Internalized phages were rapidly transported along the endocytic pathway to lysosomal compartments. Reduced viability of intracellular K1F^gfp corroborated inactivation following endocytosis. This study is the first to identify phage distribution in the liver at the hepatocellular level, confirming clearance of K1F^gfp performed mostly by KCs with a significant uptake also in LSECs.