Infection with Modifed Vaccinia virus Ankara leads to distinct phenotypic and functional characteristics of infected and bystander dendritic cells

MARÍA FERNANDA PASCUTTI; ANA MARÍA RODRIGUEZ; JULIANA FALIVENE; INGO DREXLER; LUIS GIAVEDONI; GHERARDI MM

Atlanta

Conferencia; AIDS Vaccine Conference; 2010

BACKGROUND: Understanding the development of immunity to Modified Vaccinia virus Ankara (MVA), a highly attenuated poxvirus currently under evaluation in several HIV vaccine phase I/II trials, is of great importance for the generation of more effective vaccines. MVA is known to induce phenotypic activation of human monocyte-derived dendritic cells (MDDCs) but little is known about how these DCs activate T cells to produce IFN-γ. The goal of this work was to study the maturation and cytokine production profile of MVA-infected and bystander DCs and their participation in T cell activation in an in vitro model. METHODS: MDDCs were infected with a GFP-expressing MVA. Then, CD86 expression and TNF-α/ IP-10 production were assessed by flow cytometry in infected (GFPpos) and bystander (GFPneg) cells. To study the ability of infected/bystander MDDCs to activate T cells, cells were infected at increasing MOI, charged with CMV-EBV-Influenza virus (CEF) peptides and co-cultured with syngeneic T cells. The number of IFN-γ-producing cells was analyzed by ELISPOT. The role of type I IFN in MVA-induced maturation, cytokine production and IFN-γ induction was assessed in the presence of an antibody against type I IFN receptor. RESULTS: Analysis of the maturation profile revealed that CD86 was upregulated mainly on bystander MDDCs. Infected MDDCs produced TNF-α, whereas IP-10 was almost exclusively produced by bystander MDDCs. The ability of MVA-infected MDDCs to induce IFN-γ production by specific T cells decreased as the number of infected MDDCs increased. Production of IP-10, but not maturation or IFN-γ induction, was partially blocked by anti-IFNAR. CONCLUSION: MVA infection of human MDDCs led to differential production of mediators in infected and bystander cells. Maturation was observed mainly in bystander DCs that seemed to be responsible for the induction of IFN-γ production by specific memory T cells. These results contribute to the understanding of the mechanism of T cell activation by MVA-infected DCs.