Protein kinase C overexpression does not enhance immune-stimulatory surface markers of vaccinia-infected dendritic cells and DC cell lines.

One of the shortcomings of vaccinia virus (VACV) as immunization vector is the down-regulation of HLA and costimulatory molecules in antigen presenting cells. To overcome this problem we investigated the use of protein kinase C (PKC) as immune stimulatory agent. Thus several classical and atypical PKCs were inserted into wild-type or attenuated VACV using recombination into the hemagglutinin gene and the expression driven by the VACV 7,5K-IE gene promoter. Recombinant constructs expressing PKC-alpha, -beta, -theta as well as wild-type, constitutive active or dominant negative PKC-zeta constructs were generated. Additional constructs expressing PKB/Akt1 and ICAM-1 were used for comparison. Immature and mature peripheral blood derived-dendritic cells (DC) as well as lymphoid cell lines capable of obtaining a DC-like phenotype upon mitogen stimulation were infected. Disappointingly, VACV-driven PKC overexpression did not significantly enhance expression of various activation markers or costimulatory molecules tested. Neither CD86 nor HLA-DR expression was upregulated and also no influence on the maturation of DC, as measured by DC-SIGN and CD83, was observed. However, VACV did not interfere with LPS induced up-regulation of CD83 and did not lead to substantial apoptosis of infected DC within the first 24 hours.