Long-term reversal of hypercholesterolemia in low density lipoprotein receptor (LDLR)-deficient mice by adenovirus-mediated LDLR gene transfer combined with CD154 blockade

Background Deficiency of the low density lipoprotein receptor (LDLR) result s in abnormal elevation of cholesterol within the intermediate and low dens ity plasma lipoproteins (IDL/LDL), and predisposes to early onset atheroscl erosis. Cholesterol reduction after adenovirus-mediated LDLR gene transfer to LDLR-deficient animals is transient, due to the elicitation of an immune response. Methods The LDLR-deficient mouse was used as a model to investigate adenovi rus-mediated LDLR gene transfer combined with short-term immunosuppression as a cholesterol lowering therapy. Mice were infused with replication-defic ient recombinant adenovirus encoding LDLR under control of the cytomegalovi rus promoter/enhancer (AdLDLR), and injected with a blocking antibody direc ted against CD154 (CD40 ligand) to suppress immune responses against the ve ctor and foreign transgene product. Results Mice given AdLDLR and treated with anti-CD154 expressed LDLR on hep atocytes and maintained cholesterol levels below or within normal range for at least 92 days. In contrast, without adjunct immunosuppression LDLR expr ession was transient, corresponding to temporary decline in cholesterol lev els. Analysis of cholesterol concentrations in fractionated plasma showed r emarkable reduction in all lipoprotein fractions at early time-points after gene transfer. At later time-points, non-immunosuppressed control mice reg ained the disease profile with elevated IDL/LDL cholesterol, while profiles of anti-CD154-treated mice were similar to normal. LDLR mRNA transcripts w ere present in livers of the anti-CD154-treated mice but not controls, 93 d ays after AdLDLR injection. However, vector DNA was detected in livers of b oth groups. These results suggest that loss of LDLR expression in the non a nti-CD154-treated mice was in part due to immune-mediated promoter silencin g, and that anti-CD154 prevented this effect. Conclusion Treatment with anti-CD154 antibody inhibits immune-mediated loss of transgene expression, enabling long-term reduction in cholesterol level s after AdLDLR gene transfer to LDLR-deficient mice. Copyright (C) 2000 Joh n Wiley & Sons, Ltd.