A novel gene therapy strategy using secreted multifunctional anti-HIV proteins to confer protection to gene-modified and unmodified target cells

Abstract

Current human immunodeficiency virus type I (HIV) gene therapy strategies focus on rendering HIV target cells non-permissive to viral replication. However, gene-modified cells fail to accumulate in patients and the virus continues to replicate in the unmodified target cell population. We have designed lentiviral vectors encoding secreted anti-HIV proteins to protect both gene-modified and unmodified cells from infection. Soluble CD4 (sCD4), a secreted single chain variable fragment (sscFv17b) and a secreted fusion inhibitor (sFIT45) were used to target receptor binding, co-receptor binding and membrane fusion, respectively. Additionally, we designed bi- and tri-functional fusion proteins to exploit the multistep nature of HIV entry. Of the seven antiviral proteins tested, sCD4, sCD4-scFv17b, sCD4-FIT45 and sCD4-scFv17b-FIT45 efficiently inhibited HIV entry. The neutralization potency of the bi-functional fusion proteins sCD4-scFv17b and sCD4-FIT45 was superior to that of sCD4 and the Food and Drug Administration-approved fusion inhibitor T-20. In co-culture experiments, sCD4, sCD4-scFv17b and sCD4-FIT45 secreted from gene-modified producer cells conferred substantial protection to unmodified peripheral blood mononuclear cells. In conclusion, continuous delivery of secreted anti-HIV proteins via gene therapy may be a promising strategy to overcome the limitations of the current treatment. © 2014 Macmillan Publishers Limited.