The
CD22 antigen is a viable target for therapeutic intervention for
B-cell lymphomas. Several therapeutic anti-CD22
antibodies as well as an anti-CD22-based
immunotoxin (HA22) are currently under investigation in clinical settings. Coupling of anti-CD22
reagents with a nano-
drug delivery vehicle is projected to significantly improve treatment efficacies. Therefore, we generated a mutant of the targeting segment of HA22 (a CD22 scFv) to increase its soluble expression (mut-HA22), and conjugated it to the surface of sonicated
liposomes to generate immunoliposomes (mut-HA22-liposomes). We examined
liposome binding and uptake by CD22(+) B-lymphocytes (BJAB) by using
calcein and/or
rhodamine PE-labeled
liposomes. We also tested the effect of targeting on cellular toxicity with
doxorubicin-loaded
liposomes. We report that: (i) Binding of mut-HA22-liposomes to BJAB cells was significantly greater than
liposomes not conjugated with mut-HA22 (control
liposomes), and mut-HA22-liposomes bind to and are taken in by BJAB cells in a dose and temperature-dependent manner, respectively; (ii) This binding occurred via the interaction with the cellular CD22 as pre-incubation of the cells with mut-HA22 blocked subsequent
liposome binding; (iii) Intracellular localization of mut-HA22-liposomes at 37 degrees C but not at 4 degrees C indicated that our targeted
liposomes were taken up through an energy dependent process via receptor-mediated endocytosis; and (iv) Mut-HA22-liposomes loaded with
doxorubicin exhibited at least 2-3 fold more accumulation of
doxorubicin in BJAB cells as compared to control
liposomes. Moreover, these
liposomes showed at least a 2-4 fold enhanced killing of BJAB or Raji cells (CD22(+)), but not SUP-T1 cells (CD22(-)). Taken together these data suggest that these 2nd-generation
liposomes may serve as promising carriers for targeted
drug delivery to treat patients suffering from
B-cell lymphoma.