Drug targeting using OX7-immunoliposomes: correlation between Thy1.1 antigen expression and tissue distribution in...

Area of Science:

• Immunology
• Nanotechnology
• Pharmacology

Background:

• OX7 monoclonal antibody fragments targeting Thy1.1 antigen can be conjugated to liposomes for drug delivery.
• OX7-conjugated immunoliposomes (OX7-IL) have shown potential for targeting rat glomerular mesangial cells expressing high levels of Thy1.1.

Purpose of the Study:

• To investigate the relationship between OX7-IL tissue distribution and Thy1.1 antigen localization in various rat organs.
• To determine the specificity and site of pharmacological effects of OX7-IL.

Main Methods:

• Western blot and immunohistofluorescence to assess Thy1.1 expression in different organs.
• Distribution studies using fluorescence- or (14)C-labeled OX7-IL.
• Competition assays with unbound OX7 antibody fragments.

Main Results:

• High Thy1.1 expression was found in brain cortex, striatum, thymus, and renal glomeruli; moderate levels in kidney collecting ducts, lung, and spleen; none in liver and heart.
• OX7-IL distribution showed poor correlation with Thy1.1 levels, with highest accumulation in spleen, lung, liver, and kidney, and minimal in brain and heart.
• Localized OX7-IL signal and doxorubicin toxicity were observed specifically in renal glomerular mesangial cells.
• Competition assays confirmed OX7-mediated specificity.

Conclusions:

• Tissue-specific accumulation and pharmacological effects of OX7-IL require both high target antigen density and absence of endothelial barriers.
• The liposomal drug delivery strategy is specific to renal glomeruli, potentially reducing off-target side effects.