Inflammation promotes the loss of adeno-associated virus-mediated transgene expression in mouse liver

BACKGROUND & AIMS

Non-self transgenes delivered to mouse liver via adeno-associated virus (AAV) are expressed stably due to the induction of immune tolerance. However, such transgene expression has been reported to be lost in higher-order primates. We investigated whether inflammatory processes, which likely differ between species, impact the stability of transgene expression.

METHODS

We developed a mouse model that mimics a scenario in which a subject that has received hepatic AAV-mediated gene transfer develops subsequent, vector-unrelated, systemic inflammation.

RESULTS

Inflammation eliminated previously stable expression of transgenes delivered by AAV; the limited tissue destruction and persistence of AAV genomes implicated pathways besides the cytotoxic T-cell response. Tumor necrosis factor-a down-regulated expression of the transgene from the AAV, indicating a role for similar inflammatory cytokines in such loss of transgene expression.

CONCLUSIONS

Inflammation can block AAV-mediated expression of transgenes in mouse liver. The presence of inflammation might therefore affect hepatic expression of transgenes from viral vectors in humans.

Transient immunomodulation with anti-CD40 ligand antibody and CTLA4Ig enhances persistence and secondary adenovirus-mediated gene transfer into mouse liver

Although recombinant adenovirus vectors offer a very efficient means by which to transfer genetic information into cells in vivo, antigen-dependent immunity limits the duration of gene expression and prevents retreatment. Recombinant murine CTLA4Ig and anti-CD40 ligand antibody block costimulatory interactions between T cells and antigen presenting cells. We previously reported that murine CTLA4Ig prolongs adenoviral-mediated gene transfer, but does not allow for secondary expression after readministration of the vector. In studies described here, when anti-CD40 ligand and recombinant murine CTLA4Ig were coadministered around the time of primary vector administration (i) prolonged adenovirus-mediated gene expression (length of experiment up to 1 year) from the livers of >90% of treated mice was observed, and (ii) secondary adenovirus-mediated gene transfer was achieved in >50% of the mice even after the immunosuppressive effects of these agents were no longer present. Nearly two-thirds of these mice had persistent secondary gene expression lasting for at least 200-300 days. Neither agent alone allowed transduction after secondary vector administration. Treated mice had decreased immune responses to the vector as shown by markedly decreased production of neutralizing antibodies, diminished spleen proliferation responses and IFN-gamma production in vitro, and reduced T cell infiltrates in the liver. These results suggest that it may be possible to obtain persistence as well as secondary adenoviral-mediated gene transfer with transient immunosuppressive therapies.