Cellular and humoral immune responses to viral antigens create barriers to lung-directed gene therapy with recombinant adenoviruses

TLDR

Recombinant adenoviruses are promising for lung gene therapy in cystic fibrosis, but first‑generation E1a/E1b‑deleted viruses elicit transient transgene expression, strong inflammation, and diminished efficacy upon repeat dosing. The study aims to define antigen‑specific cellular and humoral immune responses that limit adenovirus‑mediated lung gene therapy in cystic fibrosis. The authors employed immunodeficient mice together with adoptive and passive transfer experiments to dissect the antigen‑specific cellular and humoral responses responsible for the observed limitations. The results show that MHC‑I–restricted CD8+ cytotoxic T lymphocytes kill virus‑infected cells and suppress transgene expression, while MHC‑II–presented viral antigens activate CD4+ TH1 cells that, together with CD8+ responses, generate neutralizing antibodies that impede repeat adenovirus delivery.

Abstract

Recombinant adenoviruses are an attractive vehicle for gene therapy to the lung in the treatment of cystic fibrosis (CF). First-generation viruses deleted of E1a and E1b transduce genes into airway epithelial cells in vivo; however, expression of the transgene is transient and associated with substantial inflammatory responses, and gene transfer is significantly reduced following a second administration of the virus. In this study, we have used mice deficient in immunological effector functions in combination with adoptive and passive transfer techniques to define antigen-specific cellular and humoral immune responses that underlie these important limitations. Our studies indicate that major histocompatibility complex class I-restricted CD8+ cytotoxic T lymphocytes are activated in response to newly synthesized antigens, leading to destruction of virus infected cells and loss of transgene expression. Major histocompatibility complex class II-associated presentation of exogenous viral antigens activates CD4+ T-helper (TH) cells of the TH1 subset and, to a lesser extent, of the TH2 subset. CD4+ cell-mediated responses are insufficient in the absence of cytotoxic T cells to completely eliminate transgene containing cells; however, they contribute to the formation of neutralizing antibodies in the airway which block subsequent adenovirus-mediated gene transfer. Definition of immunological barriers to gene therapy of cystic fibrosis should facilitate the design of rational strategies to overcome them.