CYCLOPHOSPHAMIDE DIMINISHES INFLAMMATION AND PROLONGS TRANSGENE EXPRESSION FOLLOWING DELIVERY OF ADENOVIRAL VECTORS TO MOUSE-LIVER AND LUNG

Immune responses to adenovirus-mediated gene transfer contribute to th e problems of transient recombinant gene expression, inflammation, and difficulties with vector readministration. Activation of CD4(+) T cel ls is required for full realization of effector function of both CD8() T cells (i,e,, cytotoxic T cells) and B cells (i,e,, neutralizing an tibody), We evaluate in this study the effectiveness of a short course of high-dose cyclophosphamide to block immune responses in mice admin istered vector into lung and liver of C57BL/6 mice, Administration of cyclophosphamide with vector directed to liver blocked activation and mobilization of both CD4(+) and CD8(+) T cells, As a result, transgene expression was prolonged, inflammation was reduced, and, at the highe r doses of cyclophasphamide, formation of neutralizing antibody was pr evented and the vector was successfully readministered, Similar studie s in the lung demonstrated an effective blockade of T and B cell respo nses, In contrast to the liver, where it was easier to stabilize trans gene expression than to prevent neutralizing antibody, cyclophosphamid e prevented the formation of neutralizing antibodies at all doses in t he lung, whereas stabilization of transgene expression was only achiev ed at the highest dose, These experiments begin to define the paramete rs by which cyclophosphamide could be used as an adjunct in gene thera py.