Introduction: Increasing evidence has emerged that adenoviruses (AdV) can cause severe complications in immunocompromised hosts especially following hematopoietic stem cell transplantation (HSCT). So far protective immune responses in adenovirus infection have not been assessed in detail, but control of infection seems to be dependent on CD4+ T-cells. However, the main antigenic adenovirus targets for specific CD4+ T-cells are unknown.

Methods: We here use a novel technique to directly assess the entire repertoire of CD4+ T-cells specific for a defined antigen 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. Additionally, we evaluated the cytokine profile of AdV-lysate- and AdV-hexon-specific CD4+ T-cells.

Results: AdV-lysate-specific CD4+ T-cells reacted efficiently with AdV-hexon and penton proteins. Furthermore, CD4+ T-cells specific for hexon protein derived from AdV-serogroup B crossreact with recombinant hexon protein derived from various other AdV-serotypes and are characterized by a Th1-like cytokine profile.

Conclusion: Our results imply that adenovirus hexon protein is a suitable candidate antigen for the ex vivo generation of adenovirus-specific, serogroup cross-reactive proinflammatory CD4+ T-cells for adoptive T-cell therapies.

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