Table 1 Comparison of A, B, C, and P class CpG

CpG-A

phosphodiester CpG motif(s)

phosphorothioate-G-rich 3’ and 5’ ends

strong pDC IFN-α induction

weak B cell activation.

[146, 147]

CpG-B

multiple CpG motifs on a phosphorothioate backbone

potent Th1

strong B cell and NK cell activation

triger TNF-α and IL-6 production

weak pDC IFN-α induction

[148]

CpG-C

wholly phosphorothioate

no poly-G stretches

palindromic sequence

good induction of IFN-α in pDCs

activating B cells

good Th1 induction

[149, 150]

CpG-P

two palindromic sequences

form concatemers

multimeric units

strong induction of IFN-α production

[151]