Optimized adenovirus-antibody complexes stimulate strong cellular and humoral immune responses against an encoded antigen in naïve mice and those with preexisting immunity

The immune response to recombinant adenoviruses is the most significant impediment to their clinical use for immunization. We test the hypothesis that specific virus-antibody combinations dictate the type of immune response generated against the adenovirus and its transgene cassette under certain physiological conditions while minimizing vector-induced toxicity. In vitro and in vivo assays were used to characterize the transduction efficiency, the T and B cell responses to the encoded transgene, and the toxicity of 1 × 10 ¹¹ adenovirus particles mixed with different concentrations of neutralizing antibodies. Complexes formed at concentrations of 500 to 0.05 times the 50% neutralizing dose (ND ₅₀) elicited strong virus-and transgene-specific T cell responses. The 0.05-ND ₅₀ formulation elicited measurable anti-transgene antibodies that were similar to those of virus alone (P =0.07). This preparation also elicited very strong transgene-specific memory T cell responses (28.6±5.2% proliferation versus 7.7±1.4% for virus alone). Preexisting immunity significantly reduced all responses elicited by these formulations. Although lower concentrations (0.005 and 0.0005 ND ₅₀) of antibody did not improve cellular and humoral responses in naïve animals, they did promote strong cellular (0.005 ND ₅₀) and humoral (0.0005 ND ₅₀) responses in mice with preexisting immunity. Some virus-antibody complexes may improve the potency of adenovirus-based vaccines in naïve individuals, while others can sway the immune response in those with preexisting immunity. Additional studies with these and other virus-antibody ratios may be useful to predict and model the type of immune responses generated against a transgene in those with different levels of exposure to adenovirus.