Sequence motifs in adenoviral DNA block immune activation by stimulatory CpG motifs.
Unmethylated CpG dinucleotides in particular base contexts (CpG-S motifs) are relatively common in bacterial DNA but are rare in vertebrate DNA. B cells and monocytes have the ability to detect such CpG-S motifs that trigger innate immune defenses with production of Th1-like cytokines. Despite comparable levels of unmethylated CpG dinucleotides, DNA from serotype 12 adenovirus is immune-stimulatory, but serotype 2 is nonstimulatory and can even inhibit activation by bacterial DNA. In type 12 genomes, the distribution of CpG-flanking bases is similar to that predicted by chance. However, in type 2 adenoviral DNA the immune stimulatory CpG-S motifs are outnumbered by a 15- to 30-fold excess of CpG dinucleotides in clusters of direct repeats or with a C on the 5' side or a G on the 3' side. Synthetic oligodeoxynucleotides containing these putative neutralizing (CpG-N) motifs block immune activation by CpG-S motifs in vitro and in vivo. Eliminating 52 of the 134 CpG-N motifs present in a DNA vaccine markedly enhanced its Th1-like function in vivo, which was increased further by the addition of CpG-S motifs. Thus, depending on the CpG motif, prokaryotic DNA can be either immune-stimulatory or neutralizing. These results have important implications for understanding microbial pathogenesis and molecular evolution and for the clinical development of DNA vaccines and gene therapy vectors.
Krieg
A M
AM
Interdisciplinary Immunology Program and Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242, USA. arthur-krieg@uiowa.edu
Wu
T
T
Weeratna
R
R
Efler
S M
SM
Love-Homan
L
L
Yang
L
L
Yi
A K
AK
Short
D
D
Davis
H L
HL
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D018899:CpG Islands / Q000502:physiology*; D016207:Cytokines / Q000096:biosynthesis; D004279:DNA, Viral / Q000235:genetics*; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D018417:Th1 Cells / Q000276:immunology
D016207:Cytokines; D004279:DNA, Viral