Lyle L. Moldawer, Ph.D.
Overproduction of the pro-inflammatory cytokines, TNF-alpha, and IL-1, contributes to the pathologic consequences of adverse wound healing, adult respiratory distress syndrome, systemic inflammatory response syndrome and septic shock. However, current therapeutic approaches to deliver anti-cytokine therapies (IL-1ra, antiTNF-Alpha antibodies or anti TNF immunoadhesins) systemically are inherently inefficient and often ineffective. In particular, systemic administration of cytokine inhibitors at levels sufficient to neutralize exaggerated cytokine production in one organ may also block the presumably beneficial aspects of cytokine production in another. To develop an alternative approach for the targeted delivery of anti-cytokine therapies to organs or tissues adversely affected by acute inflammation, gene transfer of cytokine inhibitors is currently under development. Using cationic liposomes and mammalian expression plasmids which results in only the transient expression (days) of foreign genes, trasngene expression of such human cytokine inhibitors as the extra-cellular domain of the p55 TNF receptor and IL1ra, as well as the anti-inflammatory cytokines, IL-10 has been achieved in rodents and primates. Studies are under way to determine whether these expression plasmids delivering anti-inflammatory genes can reduce the exaggerated local tissue production of TNF-alpha and Il-1beta that is associated with organ damage or delayed wound healing. In this manner, the utility of transient gene transfer in clinically relevant models of infection and sepsis can be explored. In particular, the advantages of non-stable gene transfer as a novel drug delivery system for the treatment of acute inflammation, multi-system organ failure and systemic inflammatory response syndromes are currently under investigation.
Simultaneously, the Laboratory is pursuing viral techniques for gene transfer and their applicability to acute inflammation. Adenovirus gene therapy offers significant advantages over nonviral techniques in that transgene expression is often one to two logs higher than seen with plasmids and cationic liposomes. However, the widespread use of adenovirus based gene therapy has been limited by the early inflammatory response and the clearance of virally infected cells expressing the transgene. Studies are currently underway to modify the immediate proinflammatory cytokine response to adenovirus gene transfer in order to reduce the inflammatory cell infiltration and parenchymal injury that occurs early after adenovirus transfection in lung, and to alter the TH1 and TH2 type acquired immune responses to adenovirus that ultimately determine the cytotoxic T-cell and antibody reactions which limit transgene expression. In this manner, the utility of adenovirus-based gene transfer to the lung can be further developed. We are currently incorporating genes for immune modulators into the adenovirus genome using internal ribosome entry site (IRES) elements rather than administering the proteins exogenously. This approach is preferable in that the immune modulators will be produced in Ad-infected cells rather than throughout the body, minimizing the risk of systemic immune suppression.