Modulation of TNFα, a determinant of acute toxicity associated with systemic delivery of first-generation and helper-dependent adenoviral vectors

Abstract

Understanding the determinants of the host innate immune response to systemic administration of adenoviral (Ad) vectors is critical for clinical gene therapy. Acute toxicity occurs within minutes to hours after vector administration and is characterized by activation of innate immune responses. Our data indicate that in mice, indicators of vector toxicity include elevations of cytokine levels, liver transaminase levels and thrombocytopenia. To discern potential targets for blunting this host response, we evaluated genetic factors in the host response to systemically administered first-generation Ad vectors (FGV) and helper-dependent Ad vectors (HDV) containing b-galactosidase expression cassettes. A preliminary screen for modulation of vector-induced thrombocytopenia revealed no role for interferon-g, mast cells or perforin. However, vector-induced thrombocytopenia and interleukin 6 (IL-6) expression are less evident in tumor necrosis factor alpha (TNFa)-deficient mice. Moreover, we also demonstrated that TNFa blockade via antibody or huTNFR:Fc pretreatment attenuates both thrombocytopenia (440% increase in platelet count) and IL-6 expression (480% reduction) without affecting interleukin 12 , liver enzymes, hematological indices or vector transduction in a murine model. Our data indicate that the use of HDV, in combination with clinically approved TNFa immunomodulation, may represent an approach for improving the therapeutic index of Ad gene therapy for human clinical trials.

Evaluation of Long-Term Toxicity of Ad/hIFN-γ, an Adenoviral Vector Encoding the Human Interferon-γGene, in Nonhuman Primates

“…In this study recombinant adenovirus was injected intramuscularly; no decrease in platelet counts was observed, nor was the prothrombin time (PT) affected. Similar to many previous findings in mice and rhesus monkeys (Schnell et al, 2001;Varnavski et al, 2002Varnavski et al, , 2005Mane et al, 2006), intramuscularly administered recombinant adenovirus induced a transient decrease in WBC counts in the three Ad/hIFN-␥-treated groups in this study.…”

Current Advances and Future Challenges in Adenoviral Vector Biology and Targeting

“…The complement branch of the innate immune system appears to play a larger role than just vector opsonization and clearance, studies have shown that complement deficient C3-knockout (KO) mice are defective in the induction of a number of cytokines including CXCL-1, IL-5, G-CSF, GM-CSF, and IL-6 [Kiang et al, 2006]. TNFα also appears to be a modulator of acute toxicity as TNFα-deficient mice display decreased levels of IL-6 and reduced thrombocytopenia in response to Ad vector [Mane et al, 2006].…”

Characterization of high‐capacity adenovirus production by the quantitative real‐time polymerase chain reaction: a comparative study of different titration methods

“…Thus, monitoring every amplification passage allows a better control over the production process. The existing protocols for HC-Ad production are ambiguous with respect to the number of passages that should be performed before starting a largescale preparation [16,23]. In our hands, eight passages were found to be optimal for large-scale preparation.…”