The role of CpG motifs in innate immunity

Current Opinion in Immunology

Volumn 12, Issue 1, 2000, Pages 35-43

  Krieg, Arthur M ^a,b  

^a UNIVERSITY OF IOWA   (United States)

^b CpG ImmunoPharmaceuticals   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

DINUCLEOTIDE; DNA VACCINE; IMMUNOLOGIC AGENT; IMMUNOLOGICAL ADJUVANT; OLIGODEOXYNUCLEOTIDE; RECEPTOR; VACCINE;

ALLERGY; ANIMAL CELL; ANTIGEN PRESENTING CELL; ANTIGEN RECOGNITION; CANCER; HUMAN; HUMAN CELL; IMMUNE RESPONSE; IMMUNITY; IMMUNOSTIMULATION; LEUKOCYTE; MOLECULAR BIOLOGY; MOUSE; NONHUMAN; PRIMATE; PROKARYOTE; REVIEW; VERTEBRATE;

EID: 0033980073     PISSN: 09527915     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0952-7915(99)00048-5     Document Type: Review

References (98)

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7. Wagner H. Immunobiology of bacterial CpG DNA. Curr Top Microbiol Immunol. 247:1999;. in press. This entire volume is dedicated to reviews covering essentially all aspects of the biology of CpG DNA and will be an extremely useful reference for investigators wishing to get an up-to-date overview of this rapidly developing field.
8. Bird A.P. CpG islands as gene markers in the vertebrate nucleus. Trends Genet. 3:1987;342-347.
9. Krieg A.M., Wu T., Weeratna R., Efler S.M., Love-Homan L., Zhang L., Yang L., Yi A.K., Short D., Davis H. Sequence motifs in adenoviral DNA block immune activation by stimulatory CpG motifs. Proc Natl Acad Sci USA. 95:1998;12631-12636. This paper demonstrates the existence of immune neutralizing sequence motifs in ODN and in DNA vaccines.
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12. Yamamoto T., Yamamoto S., Kataoka T., Tokunaga T. Lipofection of synthetic oligodeoxyribonucleotide having a palindromic sequence of AACGTT to murine splenocytes enhances interferon production and natural killer activity. Microbiol Immunol. 38:1994;831-836.
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15. ••].
16. MacFarlane D.E., Manzel L. Antagonism of immunostimulatory CpG-oligodeoxynucletides by quinacrine, chloroquine, and structurally related compounds. J Immunol. 160:1998;1122-1131.
17. Krieg A.M., Hartmann G., Yi A-K. Mechanisms of action of CpG DNA. Curr Top Microbiol Immunol. 1999;247. in press.
18. Strekowski L., Zegrocka O., Henary M., Say M., Mokrosz M.J., Kotecka B.M., Manzel L., MacFarlane D.E. Structure-activity relationship analysis of substituted 4-quinolinamines, antagonists of immunostimulatory CpG-oligodeoxynucleotides. Bioorg Med Chem Lett. 9:1999;1819-1824.
19. Yi A-K., Klinman D.M., Martin T.L., Matson S., Krieg A.M. Rapid immune activation by CpG motifs in bacterial DNA: systemic induction of IL-6 transcription through an antioxidant-sensitive pathway. J Immunol. 157:1996;5394-5402.
20. Stacey K.J., Sweet M.J., Hume D.A. Macrophages ingest and are activated by bacterial DNA. J Immunol. 157:1996;2116-2122.
21. ••], this study demonstrates that CpG DNA triggers the rapid activation of mitogen-activated protein kinases in immune cells, and that these signaling pathways are required in order to generate downstream activation events.
22. Sweet M.J., Stacey K.J., Kakuda D.K., Markovich D., Hume D.A. IFN-γ primes macrophage responses to bacterial DNA. J Interferon Cytokine Res. 18:1998;263-271. This paper demonstrates that certain responses of macrophages to CpG DNA depend on priming of the macrophages by IFN-γ, whereas other responses do not. Macrophage expression of inducible nitric oxide synthase in response to CpG DNA requires IFN-γ priming, but activation of the HIV long terminal repeat or expression of the cationic amino acid transporter, CAT2, do not. Nevertheless, these latter activities of CpG DNA are enhanced by IFN-γ priming.
23. Yi A-K., Hornbeck P., Lafrenz D.E., Krieg A.M. CpG DNA rescue of murine B lymphoma cells from anti-IgM induced growth arrest and programmed cell death is associated with increased expression of c-myc and bcl-xL. J Immunol. 157:1996;4918-4925.
24. Sweet M.J., Stacey K.J., Ross I.L. Involvement of Ets, rel and Sp1-like proteins in lipopolysaccharide-mediated activation of the HIV-1 LTR in macrophages. J Inflam. 48:1998;67-83.
25. Cowdery J.S., Boerth N.J., Norian L.A., Myung P.S., Koretzky G.A. Differential regulation of the IL-12 p40 promoter and of p40 secretion by CpG DNA and lipopolysaccharide. J Immunol. 162:1999;6770-6775. These investigators provide the first demonstration of different mechanisms in the regulation of macrophage IL-12 expression by CpG DNA and LPS. Although both LPS and CpG DNA activate the IL-12 p40 promoter, only CpG DNA causes increased expression of p40 protein in a macrophage cell line. Addition of IFN-γ to the cells induces p40 protein expression in response to both CpG DNA and LPS.
26. Jakob T., Walker P.S., Krieg A.M., Udey M.C., Vogel J.C. Activation of cutaneous dendritic cells by CpG-containing oligo-deoxynucleotides: a role for dendritic cells in the augmentation of Th1 responses by immunostimulatory DNA. J Immunol. 161:1998;3042-3049.
27. Martin-Orozco E., Kobayashi H., Van Uden J., Nguyen M-D., Kornbluth R.S., Raz E. Enhancement of antigen-presenting cell surface molecules involved in cognate interactions by immunostimulatory DNA sequences. Int Immunol. 11:1999;1111-1118. This study provides an extensive analysis of the effects of CpG DNA on expression of cell surface MHC, costimulatory and adhesion molecules, as well as cytokine receptors and the Fcγ receptor on murine B cells and macrophages in vitro and in vivo. T cell expression of co-stimulatory molecules was not affected by CpG DNA. The kinetics of CpG-induced expression of co-stimulatory molecules in vivo was also examined, showing peak expression at day 2-7 with decreasing expression at later timepoints.
28. Sparwasser T., Miethke T., Lipford G., Borschert K., Hacker H., Heet K., Wagner H. Bacterial DNA causes septic shock. Nature. 386:1997;336-337.
29. Chu R.S., Askew D., Noss E.H., Tobian A., Krieg A.M., Harding C.V. CpG oligodeoxynucleotides downregulate macrophage class II MHC antigen processing. J Immunol. 163:1999;1188-1194. As so many studies have shown CpG DNA to be a potent adjuvant in vivo, it may seem paradoxical that it actually downregulates macrophage antigen processing and presentation, yet this is clearly shown in this study. However, this result is certainly consistent with the conclusion that in CpG-treated animals, DCs are more important for in vivo antigen presentation than macrophages, which are less capable of providing co-stimulatory signals. In fact, by avoiding antigen presentation on macrophages, it is even possible that the risk of inducing anergy to foreign antigens may be reduced. Presumably, the macrophages activated by CpG DNA are contributing to immune defence through other ways, perhaps involving innate resistance to intracellular pathogens.
30. •].
31. •], this paper demonstrates that the ability of CpG DNA to prevent activation-induced apoptosis in B lymphoma cells depends on the activation of NFκB. The second study demonstrates that an antisense ODN against the immediate early gene Egr-1 blocks the CpG-induced protection of B lymphoma cells against apoptosis. Although this experiment is interpreted to suggest a role for Egr-1 in mediating the protective effect of CpG DNA, it is noteworthy that the antisense sequence used for Egr-1 contained several poly-G motifs that have been shown to oppose the immune stimulatory effects of CpG ODN in other studies (see [32]). ODN can have multiple types of immune activities, which can complicate the interpretation of experimental results.
32. Ballas Z.K., Rasmussen W.L., Krieg A.M. Induction of natural killer activity in murine and human cells by CpG motifs in oligodeoxynucleotides and bacterial DNA. J Immunol. 157:1996;1840-1845.
33. Cowdery J.S., Chace J.H., Yi A-K., Krieg A.M. Bacterial DNA induces NK cells to produce interferon-γ in vivo and increases the toxicity of lipopolysaccharides. J Immunol. 156:1996;4570-4575.
34. Pisetsky D.S., Reich C.F. The influence of base sequence on the immunological properties of defined oligonucleotides. Immunopharmacology. 40:1998;199-208. The CpG motif is not the only DNA sequence that has immune activities. This paper demonstrates that poly-G sequences by themselves can act as B cell mitogens.
35. Hartmann G., Krieg A.M. CpG DNA and LPS induce distinct patterns of activation in human monocytes. Gene Ther. 6:1999;893-903. This study demonstrates that both LPS and CpG DNA activate human monocytes to secrete TNF-α and IL-6. The kinetics of this activation differ, however; the effects of LPS are detected within a few hours, whereas CpG DNA requires more than 12 hours to induce cytokine production. This allows differentiation of the effects of LPS and CpG DNA on human monocytes and raises the possibility that this effect of CpG DNA may be indirect.
36. Bohle B., Jahn-Schmid B., Maurer D., Kraft D., Ebner C. Oligodeoxynucleotides containing CpG motifs induce IL-12, IL-18 and IFN-γ production in cells from allergic individuals and inhibit IgE synthesis in vitro. Eur J Immunol. 29:1999;2344-2353. These studies demonstrate that PBMCs from either normal or allergic donors produce IFN-γ, IL-12, and IL-18 upon stimulation with CpG DNA but not upon non-CpG DNA stimulation. IFN-γ production is shown to occur in NK cells, and monocyte-derived DCs are shown by the reverse-transcriptase polymerase chain reaction to produce IL-12 and IL-18 mRNA upon stimulation with CpG DNA. The immune effects of CpG DNA on PBMCs from allergic donors are associated with a decrease in IgE production in vitro, which bodes well for the clinical application of CpG DNA in the immunotherapy of allergic diseases.
37. Hartmann G., Weiner G., Krieg A.M. CpG DNA as a signal for growth, activation and maturation of human dendritic cells. Proc Natl Acad Sci USA. 96:1999;9305-9310. This manuscript demonstrates that CpG DNA is a major growth factor for human primary blood DCs, promoting their survival, expression of co-stimulatory molecules, and functional ability to support T cell responses in an allogeneic mixed-lymphocyte response. This study also demonstrates that although CpG DNA activates monocyte-derived DCs to secrete Th1-like cytokines as noted above, its effects do not extend to enhancing the expression of co-stimulatory molecules on that DC cell subset. Moreover, LPS is shown to have the opposite pattern of DC-specificity in its stimulatory effects in that LPS preferentially stimulates monocyte-derived DCs, but has very little effect on primary blood DCs.
38. Brown W.C., Estes D.M., Chantler S.E., Kegerreis K.A., Suarez C.E. DNA and a CpG oligonucleotide derived from Babesia bovis are mitogenic for bovine B cells. Infect Immunity. 66:1998;5423-5432. The proinflammatory effects of many microbial extracts are well known. Since such extracts would contain CpG DNA, the question of the possible contribution of CpG DNA to the immune activation triggered by these extracts must be considered. This report is noteworthy for the demonstration that the immune stimulatory effects of Babesia bovis extracts are attributable to the parasite DNA. These effects were abolished by treatment of B. bovis extracts with nuclease.
39. Kanellos T.S., Sylvester I.D., Butler V.L., Ambali A.G., Partidos C.D., Hamblin A.S., Russell P.H. Mammalian granulocyte-macrophage colony-stimulating factor and some CpG motifs have an effect on the immunogenicity of DNA and subunit vaccines in fish. Immunology. 96:1999;507-510.
40. Shpaer E.G., Mullins J.I. Selection against CpG dinucleotides in lentiviral genes: a possible role of methylation in regulation of viral expression. Nucleic Acids Res. 18:1990;5793-5797.
41. Karlin S., Doerfler W., Cardon L.R. Why is CpG suppressed in the genomes of virtually all small eukaryotic viruses but not in those of large eukaryotic viruses? J Virol. 68:1994;2889-2897.
42. Karlin S., Ladunga I., Blaisdell B.E. Heterogeneity of genomes: measures and values. Proc Natl Acad Sci USA. 91:1994;12837-12841.
43. •].
44. •].
45. •].
46. •].
47. •].
48. •].
49. •] demonstrate that the activation of innate immunity by CpG DNA provides protection against a broad range of pathogens, as well as tumor cell challenges. CpG-induced protection is shown to be dependent on the production of IFN-γ and IL-12. As might be expected, CpG-induced protection against challenge with different types of organisms shows some kinetic differences. In CpG-induced protection against Listeria monocytogenes, at least 48 hours is required between the time of CpG exposure and the time of pathogen challenge, which presumably reflects the time required for upregulation of the innate immune defences required to control this rapidly replicating pathogen. However, CpG-induced defences against the more indolent pathogen, Leishmania major, can eradicate infection even when CpG treatment is delayed until 20 days after infection. A single dose of CpG DNA protects against pathogen challenge for approximately two to four weeks, and with repeated doses protection can be extended much further, perhaps even indefinitely. As this approach appears to be without major toxicity, it has been proposed as a defence against bioterrorism (see [6]).
50. Roman M., Martin-Orozco E., Goodman J.S., Nguyen M-D., Sato Y., Ronaghy A., Kornbluth R.S., Richman D.D., Carson D.A., Raz E. Immunostimulatory DNA sequences function as T helper-1-promoting adjuvants. Nat Med. 3:1997;849-854.
51. Chu R.S., Targoni O.S., Krieg A.M., Lehmann P.V., Harding C.V. CpG oligodeoxynucleotides act as adjuvants that switch on Th1 immunity. J Exp Med. 186:1997;1623-1631.
52. Lipford G.B., Bauer M., Blank C., Reiter R., Wagner H., Heeg K. CpG-containing synthetic oligonucleotides promote B and cytotoxic T cell responses to protein antigen: a new class of vaccine adjuvants. Eur J Immunol. 27:1997;2340-2344.
53. Schirmbeck R., Melber K., Reimann J. Adjuvants that enhance priming of cytotoxic T cells to a Kb-restricted epitope processed from exogenous but not endogenous hepatitis B surface antigen. Int Immunol. 11:1999;1093-1102.
54. Chelvarajan R.L., Raithatha R., Venkataraman C., Kaul R., Han S-S., Robertson D.A., Bondada S. CpG oligodeoxynucleotides overcome the unresponsiveness of neonatal B cells to stimulation with the thymus-independent stimuli anti-IgM and TNP-Ficoll. Eur J Immunol. 29:1999;2808-2818. This interesting paper shows that CpG DNA does not induce production of IL-1 in mouse spleen cells, but nevertheless induces even neonatal B cells to proliferate in response to IgM ligation or exposure to the thymus-independent type II model antigen, trinitrophenol-Ficoll.
55. Davis H.L., Weeranta R., Waldschmidt T.J., Tygrett L., Schorr J., Krieg A.M. CpG DNA is a potent adjuvant in mice immunized with recombinant hepatitis B surface antigen. J Immunol. 160:1998;870-876.
56. •].
57. •].
58. •].
59. •] demonstrate the ability of CpG DNA to act as an adjuvant for mucosal vaccines. Intranasal immunization with CpG DNA induces both cell-mediated and humoral responses, both systemically and at local and distant mucosal sites. Moreover, a Th1 bias is seen with mucosal CpG immunization. As a mucosal adjuvant, CpG DNA is at least as effective as cholera toxin, and better tolerated.
60. ••].
61. ••] demonstrate that CpG DNA is an effective adjuvant for inducing Th1 humoral and cell-mediated immune responses in neonatal mice. In fact, even in young mice in which Th2 responses have already been induced, CpG DNA can still partially overcome these.
62. Jones T.R., Obaldia N. III, Gramzinski R.A., Charoenvit Y., Kolodny N., Davis H.L., Krieg A.M., Hoffman S.L. Synthetic oligodeoxynucleotides containing CpG motifs enhance immunogenicity of a peptide malaria vaccine in Aotus monkeys. Vaccines. 17:1999;3065-3071. In this study, monkeys were immunized with a peptide vaccine against malaria that was formulated in mineral oil (Montanide 720, Seppic SA, Paris) with CpG or control ODN added as adjuvants. The monkeys immunized with the CpG ODN had enhanced antibody responses compared with the controls.
63. Gramzinski R.A., Millan C.L., Obaldia N., Hoffman S.L., Davis H.L. Immune response to a hepatitis B DNA vaccine in Aotus monkeys: a comparison of vaccine formulation, route, and method of administration. Mol Med. 4:1998;109-118. In this study, monkeys were immunized with a DNA vaccine against hepatitis B, and the adjuvant effect of CpG DNA was tested by simply adding Escherichia coli genomic DNA as a source of CpG motifs. Indeed, monkeys receiving the additional E. coli DNA had increased levels of antigen-specific antibody responses compared with monkeys that received the DNA vaccine alone.
64. Krieg A.M., Yi A-K., Schorr J., Davis H.L. The role of CpG dinucleotides in DNA vaccines. Trends Microbiol. 6:1998;23-27.
65. Akbari O., Panjwani N., Garcia S., Tascon R., Lowrie D., Stockinger B DNA vaccination: transfection and activation of dendritic cells as key events for immunity. J Exp Med. 189:1999;169-177. The mechanisms through which DNA vaccines drive such powerful Th1-like immune responses are incompletely understood. This report provides evidence from in vivo studies that injection of a DNA vaccine transfects a relatively small number of APCs to express the encoded gene, but causes activation of a large majority of the DCs in draining lymph nodes. Presumably, this more extensive nonspecific activation of DCs is a result of the CpG motifs in plasmids that have been taken up but degraded before they could be expressed as protein.
66. Grifantini R., Finco O., Bertonini E., Draghi M., Del Gludice G., Kocken C., Thomas A., Abrignani S., Grandi G. Multi-plasmid DNA vaccination avoids antigenic competition and enhances immunogenicity of a poorly immunogenic plasmid. Eur J Immunol. 28:1998;1225-1232.
67. Yi A-K., Chang M., Peckham D.W., Krieg A.M., Ashman R.F. CpG oligodeoxyribonucleotides rescue mature spleen B cells from spontaneous apoptosis and promote cell cycle entry. J Immunol. 160:1998;5898-5906. This report contains an extensive structure/function analysis of different CpG motifs using as readouts the protection of splenic B cells from spontaneous apoptosis and their progression into the cell cycle. The manuscript shows that the commonly cited formula for a CpG motif of purine-purine-CpG-pyrimidine-pyrimidine is incorrect; a much wider variety of CpG motifs were stimulatory in this study. In fact, the only CpG motifs that were not highly stimulatory were those in which the CpG was either preceded by a C or followed by a G. Sequences outside the immediate flanking bases of the CpG dinucleotide are also important in modulating the immune stimulatory effect since polypyrimidine sequences on the 3′ end of an ODN were found to be optimal for stimulation. These studies were performed with phosphodiester ODN, and other studies have shown that when ODN are made with a phosphorothioate backbone, a more restricted subset of CpG motifs is stimulatory.
68. Biswas S., Ashok M.S., Reddy G.S., Srinivasan V.A., Rangarajan P.N. Evaluation of the protective efficacy of rabies DNA vaccine in mice using an intracerebral challenge model. Curr Sci. 76:1999;1012-1016.
69. Vinner L., Nielsen H.V., Bryder K., Corbet S., Nielsen C., Fomsgaard A. Gene gun DNA vaccination with Rev-independent synthetic HIV-1 gp160 envelope gene using mammalian codons. Vaccine. 17:1999;2166-2175.
70. •].
71. •] demonstrate that intrapulmonary delivery of plasmid vectors triggers acute immune-mediated inflammation in the lung, which is caused by the presence of unmethylated CpG motifs in the vectors. This undesirable side effect can be avoided by methylation of the vectors. With realization of the importance of CpG-induced immune stimulation in the gene therapy community, there will be increasing interest on the development of ways to avoid these effects, such as by the incorporation of immune neutralizing sequences into the plasmids used for gene delivery.
72. Sun S., Beard C., Jaenisch R., Jones P., Sprent J. Mitogenicity of DNA from different organisms for murine B cells. J Immunol. 159:1997;3119-3125.
73. Wloch M.K., Pasquini S., Ertl H.C.J., Pisetsky D.S. The influence of DNA sequence on the immunostimulatory properties of plasmid DNA vectors. Human Gene Ther. 9:1998;1439-1447.
74. Weeratna R., Brazolot Millan C.L., Krieg A.M., Davis H.L. Reduction of antigen expression from DNA vaccines by coadministerred oligodeoxynucleotides. Antisense Nucleic Acid Drug Dev. 8:1998;351-356.
75. Tuetken R.S., Yi A-K., Krieg A.M. The immune effects of bacterial DNA and their possible role in the pathogenesis of lupus. Tsokos G.C., Kammer G., Totowa N.J. Lupus: Molecular and Cellular lPathogenesis. 1999;79-100 Humana Press.
76. Gilkeson G.S., Ruiz P., Pippen A.M.M., Alexander A.L., Lefkowith J.B., Pisetsky D.S. Modulation of renal disease in autoimmune NZB/NZW mice by immunization with bacterial DNA. J Exp Med. 183:1996;1389-1397.
77. Gilkeson G.S., Conover J., Halpern M., Pisetsky D.S., Feagin A., Klinman D.M. Effects of bacterial DNA on cytokine production by (NZB/NZW)F1 mice. J Immunol. 161:1998;3890-3895.
78. Sato Y., Masayuki M., Sato Y., Nishimaki T., Kochi H., Kasukawa R. CpG motif-containing DNA fragments from sera of patients with systemic lupus erythematosus proliferate mononuclear cells in vitro. J Rheumatol. 26:1999;294-301. It has been known for many years that besides making anti-DNA antibodies, lupus patients also have increased levels of circulating DNA in their plasma (see also [75]). This report demonstrates that when lupus sera DNA is cloned and expressed in bacteria, it has stimulatory effects on human PBMCs. While this result may seem obvious, since the lupus DNAs were grown in bacteria and would therefore be unmethylated, it should be kept in mind that unmethylated vertebrate DNA is not normally mitogenic [72]. Further studies of lupus plasma DNAs are clearly needed in order to understand their possible significance.
79. Bachmaier K., Neu N., de la Maza L.M., Pal S., Hessel A., Penninger J.M. Chlamydia infections and heart disease linked through antigenic mimicry. Science. 283:1999;1335-1339. CpG DNA is an outstanding adjuvant for inducing immune responses to foreign antigens. This report demonstrates that CpG DNA can also adjuvant an autoimmune response to a cardiac antigen, apparently by the mechanism of molecular mimicry. The role of CpG in serving as an adjuvant for associated microbial antigens is of course predicted from the hypothesis that it serves as a signal for 'infectious danger'. However, this report raises the specter that exposure to CpG DNA during an infection could help break tolerance to self-antigens under certain conditions. Further studies will be required in order to determine whether the presence of CpG DNA may be linked to hypothesized associations between infections and autoimmune disease.
80. Deng G-M., Nilsson I-M., Verdrengh M., Collins L.V., Tarkowski A. Intra articularly localized bacterial DNA containing CpG motifs induces arthritis. Nat Med. 5:1999;702-705. In this report, the proinflammatory effects of CpG DNA injected into the joint appear to result in a self-limited local inflammation, but induction of antigen-specific autoimmunity is not demonstrated. The findings are likely to be relevant to the mechanisms of joint damage in septic arthritis, but most studies indicate that microbial DNA is rarely present in the joints of patients with the most common rheumatic diseases such as rheumatoid arthritis.
81. Segal R., Bermas B.L., Dayan M., Kalush F., Shearer G.M., Mozes E. Kinetics of cytokine production in experimental systemic lupus erythematosus. J Immunol. 158:1997;3009-3016.
82. •].
83. •] demonstrate the complexities of the immune effects of CpG DNA and of models for organ-specific autoimmunity. Using different experimental models and treatment regimens, CpG DNA is shown in the former case to aggravate EAE, and in the latter case to ameliorate it.
84. Redford T.W., Yi A-K., Ward C.T., Krieg A.M. Cyclosporine A enhances IL-12 production by CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides. J Immunol. 161:1998;3930-3935.
85. Sparwasser T., Hultner L., Koch E.S., Luz A., Lipford G.B., Wagner H. Immunostimulatoy CpG-oligodeoxynucleotides cause extramedullary murine hemopoiesis. J Immunol. 162:1999;2368-2374. This manuscript shows that CpG DNA induces a dose-dependent extramedulary hemopoiesis in mice. This effect is maximal at approximately day six after CpG injection, and is associated with an increase in the numbers of myeloid and erythroid precursors in the spleen. Treatment with sublethally irradiated mice with CpG ODN protects them against lethal challenge with Listeria monocytogenes and leads to a more rapid recovery of immune responses to vaccination. These results suggest potential utility of CpG DNA in the treatment of immune-compromised humans.
86. Levin A.A., Monteith D.K., Leeds J.M., Nicklin P.L., Geary R.S., Butler M., Templin M.V., Henry S.P. Toxicity of oligodeoxynucleotide therapeutic agents. Crooke S. Handbook of Experimental Pharmacology 131: Antisense Research and Application. 1998;169-215 Springer-Verlag, New York.
87. Henry S.P., Templin M.V., Gillett N., Rojko J., Levin A.A. Correlation of toxicity and pharmacokinetic properties of a phosphorothioate oligonucleotide designed to inhibit ICAM-1. Toxicol Pathol. 27:1999;95-100.
88. Smith J.B., Wickstrom E. Antisense c-myc and immunostimulatory oligonucleotide inhibition of tumorigenesis in a murine B-cell lymphoma transplant model. J Natl Cancer Inst. 98:1998;1146-1154.
89. Kline J.N. Effects of CpG DNA on Th1/Th2 balance in asthma. Curr Top Microbiol Immunol. 247:1999;. in press.
90. Kline J.N., Waldschmidt T.J., Businga T.R., Lemish J.E., Weinstock J.V.,
91. ••].
92. ••] demonstrate several key findings supporting the utility of CpG DNA in the treatment of established Th2-mediated diseases. Together, the reports demonstrate that CpG DNA can not only prevent sensitization to an allergen, but also prevent established Th2-mediated immune responses in the airways. This is associated with the induction of a Th1-like immune response to the allergen. It appears that CpG DNA is most effective in reducing established Th2-like responses when the CpG DNA is given together with the allergen, but treatment with CpG DNA alone is also effective, especially when the DNA is given at least 48 hours prior to the allergen inhalation. The beneficial effects of CpG DNA in these systems persist for weeks after a single dose. Treatment appears to be well tolerated, although further studies will be required to determine the possible adverse effects of establishing a Th1-like immune response in the airways if the antigen is subsequently inhaled repeatedly.
93. Kline J.N., Krieg A.M., Waldschmidt T.J., Ballas S.K., Jain V., Businga T.R. CpG oligodeoxynucleotides do not require Th1 cytokines to prevent eosinophilic airway inflammation in a murine model of asthma. J All Clin Immunol. 104:1999;1258-1264. It may be expected that the ability of CpG DNA to oppose Th2-mediated airways inflammation depends on its induction of the Th1-like cytokines, IFN-γ and IL-12. It is therefore surprising that neither one of these cytokines is absolutely required for CpG DNA to work in this model system. CpG DNA prevented the induction of Th2-like immune responses in mice that were genetically deficient in both IL-12 and IFN-γ, although this required somewhat higher doses of CpG than were effective in wild-type mice. Further investigation into the mechanisms of this IL-12- and IFN-γ-independent effect of CpG DNA may reveal new insights into the regulation of Th1- and Th2-like immune responses.
94. Schwartz D.A., Wohlford-Lenane C.L., Quinn T.J., Krieg A.M. Bacterial DNA or oligonucleotides containing unmethylated CpG motifs can minimize LPS-induced inflammation in the lower respiratory tract through an IL-12 dependent pathway. J Immunol. 163:1999;224-231.
95. Weiner G.J., Liu H-M., Wooldridge J.E., Dahle C.E., Krieg A.M. Immunostimulatory oligodeoxynucleotides containing the CpG motifs are effective as immune adjuvants in tumor antigen immunization. Proc Natl Acad Sci USA. 94:1997;10833-10837.
96. Liu H.M., Newbrough S.E., Bhatia S.K., Dahle C.E., Krieg A.M., Weiner G.J. Immunostimulatory CpG oligodeoxynucleotides enhance the immune response to vaccine strategies involving granulocyte-macrophage colony-stimulating factor. Blood. 92:1998;3730-3736. This manuscript extends previous studies demonstrating the efficacy of CpG DNA as an adjuvant for a tumor vaccine by showing a remarkable degree of synergy with a GM-CSF-tumor antigen fusion protein. 70% of immunized mice could be cured of tumor even when the immunization was given only three days prior to injection of a lethal dose of tumor cells.
97. Sun S., Zhang X., Tough D.F., Sprent J. Type I interferon-mediated stimulation of T cells by CpG DNA. J Exp Med. 188:1998;2335-2342. This study demonstrates that although CpG DNA does not directly activate T cells, it induces adherent cells to produce type I IFNs that secondarily activate T cells to express CD69 and B7-2. The type I IFNs also have a suppressive effect on T cell proliferation, which is demonstrated using cells from mice genetically deficient in the type I IFN receptor.
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