Treatment of Adenovirus Infection by Adoptive Immunotherapy: Adenovirus Capsid Hexon Is the Main Target Protein of Adenovirus-Specific Cellular Immunity.

Introduction: Adenovirus (AdV) infection is a severe complication after hematopoietic stem cell transplantation, particularly in paediatric patients. Control of AdV infection particularly seems to be dependent on CD4+ T-cells but their main AdV antigenic targets have remained unknown so far. In order to design protocols for targeted adoptive immunotherapy the identification of the main AdV antigenic targets is a fundamental prerequisite.

Methods: We here adapted a novel technique to directly assess the entire repertoire of CD4+ T-cells specific AdV antigens according to antigen-induced CD154 expression after short-term ex vivo stimulation. AdV-lysate-specific and AdV-hexon-specific CD4+ T-cells were isolated, expanded in vitro and further assessed for their fine specificities using recombinant AdV-proteins and AdV-lysates from various AdV-serogroups. The cytokine profile of AdV-lysate- and AdV-hexon-specific CD4+ T-cells were assessed by intracellular analysis of AdV-induced CD154+ CD4+ T-cells.

Results: AdV-lysate-specific CD4+ T-cells reacted predominantly with AdV-hexon capsid protein. Furthermore, AdV-hexon (serogroup B) specific CD4+ T-cells crossreacted with recombinant hexon protein derived from various other AdV-serotypes and were characterized by a Th1-like cytokine profile.

Conclusion: Our results prove the effectiveness of antigen-induced CD154-expression for assessment of the entire repertoire of CD4+ T-cells specific for pathogens, for the identification of immunodominant target antigen from pathogens. We demonstrate that adenovirus hexon protein is a suitable candidate antigen for the ex vivo generation of adenovirus-specific, serogroup cross-reactive CD4+ T-cells with a Th1-like cytokine profile for adoptive T-cell therapies.