Virosomes of hepatitis B virus envelope L proteins containing doxorubicin: synergistic enhancement of human liver-specific antitumor growth activity by radiotherapy

Abstract

Bionanocapsules (BNCs) are hollow nanoparticles consisting of hepatitis B virus (HBV) envelope L proteins and have been shown to deliver drugs and genes specifically to human hepatic tissues by utilizing HBV-derived infection machinery. The complex of BNCs with liposomes (LPs), the BNC–LP complexes (a LP surrounded by BNCs in a rugged spherical form), could also become active targeting nanocarriers by the BNC function. In this study, under acidic conditions and high temperature, BNCs were found to fully fuse with LPs (smooth-surfaced spherical form), deploying L proteins with a membrane topology similar to that of BNCs (ie, virosomes displaying L proteins). Doxorubicin (DOX) was efficiently encapsulated via the remote loading method at 14.2%±1.0% of total lipid weight (mean ± SD, n=3), with a capsule size of 118.2±4.7 nm and a ζ-potential of −51.1±1.0 mV (mean ± SD, n=5). When mammalian cells were exposed to the virosomes, the virosomes showed strong cytotoxicity in human hepatic cells (target cells of BNCs), but not in human colon cancer cells (nontarget cells of BNCs), whereas LPs containing DOX and DOXOVES (structurally stabilized PEGylated LPs containing DOX) did not show strong cytotoxicity in either cell type. Furthermore, the virosomes preferentially delivered DOX to the nuclei of human hepatic cells. Xenograft mice harboring either target or nontarget cell-derived tumors were injected twice intravenously with the virosomes containing DOX at a low dose (2.3 mg/kg as DOX, 5 days interval). The growth of target cell-derived tumors was retarded effectively and specifically. Next, the combination of high dose (10.0 mg/kg as DOX, once) with tumor-specific radiotherapy (3 Gy, once after 2 hours) exhibited the most effective antitumor growth activity in mice harboring target cell-derived tumors. These results demonstrated that the HBV-based virosomes containing DOX could be an effective antitumor nanomedicine specific to human hepatic tissues, especially in combination with radiotherapy.

Elucidation of the early infection machinery of hepatitis B virus by using bio-nanocapsule

“…BNC was capable of fusing with liposomes (LPs), leading to the formation of BNC-LP complex[ 28 ]. Under high temperature (up to 70 °C) and acidic conditions, the complex was found to transform into a smooth and spherical structure (namely virosomes), in which L proteins translocated across the membrane in the correct topology[ 34 ]. Following incorporation of beads and genes, these virosomes could efficiently deliver into the cytoplasm of human hepatic cells in vitro [ 28 ] and specifically to human hepatic cells in vivo [ 28 , 34 ].…”

“…Under high temperature (up to 70 °C) and acidic conditions, the complex was found to transform into a smooth and spherical structure (namely virosomes), in which L proteins translocated across the membrane in the correct topology[ 34 ]. Following incorporation of beads and genes, these virosomes could efficiently deliver into the cytoplasm of human hepatic cells in vitro [ 28 ] and specifically to human hepatic cells in vivo [ 28 , 34 ]. Furthermore, after incorporating doxorubicin by remote loading method, the virosomes were intravenously injected into xenograft mice harboring human hepatic cell-derived tumors.…”

“…Furthermore, after incorporating doxorubicin by remote loading method, the virosomes were intravenously injected into xenograft mice harboring human hepatic cell-derived tumors. The virosomes could retard the tumor growth more effectively than LPs containing doxorubicin, strongly suggesting that virosome could delivery their payload into human hepatic cell-derived tumor efficiently utilizing HBV-derived infection machinery[ 34 ]. These results indicate that the virosome is a promising nanocarrier for cytoplasmic delivery of drugs and genes.…”

Targeted Drug Delivery in Lipid-like Nanocages and Extracellular Vesicles

“…Virosomes are vesicles containing viral glycoproteins, such as neuraminidase [86], influenza virus hemagglutinin [87], and hepatitis B virus protein L [88] in their phospholipid bilayer ( Fig. 2A ).…”

Current Progress of Virus-mimicking Nanocarriers for Drug Delivery

“…BNCs can fuse with LPs and form BNC-LP complexes 153 , 154 . Furthermore, high temperature and low pH facilitates the fusion between BNCs and LPs, leading to the formation of BNC-virosomes 155 . When BNC-virosomes containing doxorubicin were injected into hepatic tumor-bearing xenograft mice, the growth of hepatic cell-derived tumors was inhibited effectively and specifically, strongly suggesting that BNC-virosomes deliver their payload into tumor efficiently utilizing HBV-derived infection machinery 155 .…”