Whole blood cultures to assess the immunostimulatory activities of CpG oligodeoxynucleotides

Specially designed oligodeoxynucleotide (ODN) sequences known as 'CpG' ODNs elicit innate and acquired immune responses. In general, screening of new CpG ODNs has been conducted by conventional lymphoproliferative assays or e xpression of activation markers in peripheral blood mononuclear cell (PBMC) cultures. Here, we compared conventional in vitro human PBMC assays with w hole blood assays for screening the immunostimulatory properties of CpG ODN s. Commercially available DNA preparations and mycobacterial-based adjuvant s were used as comparators. Activation was assessed by flow cytometry and c ytokine production. CpG ODNs, identified by four-letter codes, consisted of 2006 (strong human cell stimulant), 1826 (strong murine cell stimulant), 1 840 (weak immunostimulant). and 2041, a non-CpG ODN. In both test systems, and in accordance with previous reports, 2006 was an effective up-regulator of CD40 on human dendritic cells (DC1, DC2), monocytes, and B cells, and o f CD69 on NK cells. In contrast to murine cells exposed to CpG ODNs, IL-12 (p40) and IFN-gamma production in human immune cells was negligible, but gr eatly enhanced by adding GM-CSF, Like 2006, two comparator mycobacterial ad juvant formulations activated DC1, DC2, monocytes and natural killer (NK) c ells, but only 2006 had a strong effect on B cells. The usefulness of the w hole blood assay was further demonstrated by studies in small volumes of um bilical cord mononuclear cells. that like adult blood cells, showed up-regu lation of CD40 expression on B cells, DC, and monocytes, and CD69 on NK cel ls. The whole blood assay, in conjunction with flow cytometry, is useful fo r assessing the immunological properties of CpG ODN sequences. (C) 2001 Els evier Science B.V. All rights reserved.