CpG DNA: a novel immunomodulator

CpG DNA-triggered upregulation of TLR9 expression affects apoptosis and immune responses in human plasmacytoid dendritic cells isolated from chronic hepatitis B patients

Plasmacytoid dendritic cells (pDCs) were treated with cytosine-phosphate-guanine (CpG) DNA, and cell apoptosis, signals and immune responses were measured to investigate the effects and mechanism of CpG DNA in pDCs from chronic hepatitis B patients. CpG DNA-stimulated pDCs secreted more IFN-α than the control pDCs. CpG DNA activated Toll-like receptor 9 (TLR9), thereby resulting in the upregulated expression of myeloid differentiation primary response gene 88 (MyD88), interferon regulatory factor 7 (IRF7) and nuclear factor kappa B (NF-κB). Furthermore, CpG DNA down-regulated apoptosis and promoted the expression of IFN-α, interleukin-12 (IL-12), IL-21, IL-26 and tumour necrosis factor-α (TNF-α) in pDCs. Following treatment with NF-κB inhibitor, pyrollidine dithiocarbamate (PDTC), the influence of CpG DNA on pDCs was inhibited. Our results suggest that CpG DNA may directly interfere with the function of pDCs through TLR9-mediated upregulation of MyD88, IRF7 and NF-κB expression, which can partially explain the activation of pDCs in chronic hepatitis B patients.

Early-Stage Identification and Avoidance of Antisense Oligonucleotides Causing Species-Specific Inflammatory Responses in Human Volunteer Peripheral Blood Mononuclear Cells

A human peripheral blood mononuclear cell (PBMC)-based assay was developed to identify antisense oligonucleotide (ASO) with the potential to activate a cellular innate immune response outside of an acceptable level. The development of this assay was initiated when ISIS 353512 targeting the messenger ribonucleic acid for human C-reactive protein (CRP) was tested in a phase I clinical trial, in which healthy human volunteers unexpectedly experienced increases in interleukin-6 (IL-6) and CRP. This level of immune stimulation was not anticipated following rodent and nonhuman primate safety studies in which no evidence of exaggerated proinflammatory effects were observed. The IL-6 increase induced by ISIS 353512 was caused by activation of B cells. The IL-6 induction was inhibited by chloroquine pretreatment of PBMCs and the nature of ASOs suggested that the response is mediated by a Toll-like receptor (TLR), in all likelihood TLR9. While assessing the inter PBMC donor variability, two classes of human PBMC responders to ISIS 353512 were identified (discriminator and nondiscriminators). The discriminator donor PBMCs were shown to produce low level of IL-6 after 24 h in culture, in the absence of ASO treatment. The PBMC assay using discriminator donors was shown to be reproducible, allowing to assess reliably the immune potential of ASOs by comparison to known benchmark ASO controls that were previously shown to be either safe or inflammatory in clinical trials. Clinical Trial registration numbers: NCT00048321 NCT00330330 NCT00519727.

The Distinct and Cooperative Roles of Toll-Like Receptor 9 and Receptor for Advanced Glycation End Products in Modulating In Vivo Inflammatory Responses to Select CpG and Non-CpG Oligonucleotides

Antisense oligonucleotides (ASOs) are widely accepted therapeutic agents that suppress RNA transcription. While the majority of ASOs are well tolerated in vivo, few sequences trigger inflammatory responses in absence of conventional CpG motifs. In this study, we identified non-CpG oligodeoxy-nucleotide (ODN) capable of triggering an inflammatory response resulting in B cell and macrophage activation in a MyD88- and TLR9-dependent manner. In addition, we found the receptor for advance glycation end product (RAGE) receptor to be involved in the initiation of inflammatory response to suboptimal concentrations of both CpG- and non-CpG-containing ODNs. In contrast, dosing RAGE KO mice with high doses of CpG or non-CpG ODNs lead to a stronger inflammatory response than observed in wild-type mice. Together, our data provide a previously uncharacterized in vivo mechanism contingent on ODN-administered dose, where TLR9 governs the primary response and RAGE plays a distinct and cooperative function in providing a pivotal role in balancing the immune response.

CpG DNA analysis of bacterial STDs

BACKGROUND

Bacterial infections in the genital tract frequently result in morbidity through a variety of inflammation based symptoms. One component of the bacteria that may trigger host inflammatory response is their DNA. CpG motifs in this DNA are known targets for Toll-like receptor 9 (TLR9), which is a pathogen-recognition receptors focusing on CpG DNA. The activation of TLR9 induces the NF-κB inflammatory pathway. This study aims to provide a broad view of the inflammatory potential of CpG DNA motifs in bacteria related to genital diseases: C. trachomatis, E. coli, N. gonorrhoeae, G. vaginalis, H. ducreyi, L. crispatus, L. gasseri, M. hominis, M. genitalium, T. pallidum, and U. urealyticum.

METHODS

Publicly available genomic sequences of the bacterial species and strains have been analyzed in silico to produce a CpG index number. This CpG index number shows the relative inflammatory potential of the genome and has previously been used in a study by Lundberg et al. (2003). Higher CpG index values suggest a strong CpG induced inflammation potential during infection and vice versa.

RESULTS

The highest observed CpG index belongs to G. vaginalis with a value of 26,2, suggesting a strong pro-inflammatory potential when in contact with TLR9. The lowest index belongs to N. gonorrhoeae with a value of -79,5, suggesting a strong immunoinhibitory effect on TLR9 contact. Interestingly, Lactobacilli showed a mean CpG index value of 4,2, suggesting a weak inflammatory potential.

DISCUSSION

Our results show varying CpG index values between bacterial species. Comparison of CpG indices with the clinical course of several pathogens shows the CpG index helps clarify the clinical course of infection. However, we found no links between CpG index values and either obligate pathogenicity or facultative pathogenicity through bacterial vaginosis. Lactobacilli showed relatively low CpG indices which do suggest a lower inflammatory potential from these bacteria.

CONCLUSIONS

Our results show varying CpG index values between bacterial species, which may help clarify the clinical course of infection, and may help diagnosis.

Protection of mice against Brucella abortus 544 challenge by vaccination with recombinant OMP28 adjuvanted with CpG oligonucleotides

Brucella abortus, a gram negative, facultative intracellular pathogen causes brucellosis in many animal species and humans. Although live, attenuated vaccines are available against this infection, they suffer from certain limitations. Therefore, the development of an effective subunit vaccine against brucellosis is an area of intense research. The outer membrane proteins (OMPs) of Brucella species have been extensively studied for its immunogenicity and protective ability. We have investigated the potential of CpG ODN to enhance the immunogenicity and protective efficacy of recombinant 28 kDa outer membrane protein (rOMP28) of Brucella melitensis. The study demonstrated vigorous immunoglobulin G (IgG) response of OMP28. The administration of rOMP28 with CpG caused increased cell mediated immune response in terms of induced IgG2a, T-cell proliferation and up-regulation of type I cytokine expression. In contrast, the free antigen suppressed the interferon gamma (type I cytokine) production on in-vitro stimulation of spleenocytes. The result indicates the role of OMP28 in the down regulation of IFN-gamma production. Moreover, the B. abortus S-19 vaccinated mice showed highest production of IL-4 and IFN-gamma. The protective ability of the antigen was evaluated by systemic bacterial clearance after challenging the mouse with B. abortus 544 pathogen. The level of protection was significant in rOMP28+CpG treated mice but was lower than the required level. The results of the present study indicate that rOMP28 could be an immunogen capable of inducing both humoral and cellular immune response. The humoral response was biased towards Th1 type when it was co-administered with CpG.

Enhanced in vivo immunogenicity of SIV vaccine candidates with cationic liposome-DNA complexes in a rhesus macaque pilot study

This pilot study tested the immunogenicity of a novel cationic liposome-DNA complex (CLDC) immunomodulatory vaccine adjuvant. Combined with a specific antigen, CLDC enhanced anti-SIV immune responses induced by various SIV vaccine candidates. Rhesus macaques immunized in the presence of CLDC developed stronger SIV-specific T and B cell responses compared to animals immunized without CLDC. These differences persisted and resulted in better memory responses after an in vivo boost of the animals several months later with whole AT-2 inactivated SIVmac239. Thus, CLDC should be explored further as a potential immunomodulatory adjuvant in HIV vaccine design.

A review of CpGs and their relevance to aquaculture

CpG oligodeoxynucleotides (ODN) have been described as functioning as natural adjuvants because they promote professional antigen presenting cell (APC) function and co-stimulate lymphocytes. The majority of studies into the immune effects of CpG ODN to date have been carried out on mammals where they are proving very successful at stimulating innate and adaptive immune responses in a variety of species as well as protecting them from bacterial, viral and protozoan pathogens. Fish also possess the ability to raise both innate and adaptive immune responses to invading pathogens and interest in the effect of CpG ODN on the piscine immune system is growing. Various studies have now been carried out to elicit the effects of CpG ODN on diverse fish species showing that 31 different B-class CpG ODN exert various immune responses both in vivo and in vitro in salmonids, cyprinids and pleuronectiformes. These responses include activation of macrophages, proliferation of leucocytes and stimulation of cytokine expression. CpG ODN have also been shown to be protective against bacterial and viral challenge as well as against pathogenic amoebae. As would be expected these effects are all dependent on not only the ODN sequence and length but on the concentration and the species in which it is being used. This review provides the first comprehensive overview of all CpG ODN tested in fish to date and brings together all the work carried out in this field.

CpG-oligodeoxynucleotide is a potent adjuvant with an Entamoeba histolytica Gal-inhibitable lectin vaccine against amoebic liver abscess in gerbils

The protozoan parasite Entamoeba histolytica causes invasive amoebiasis characterized by amoebic dysentery and liver abscesses (ALA). The E. histolytica galactose/N-acetyl-D-galactosamine-inhibitable lectin (Gal-lectin), an immunogenic surface molecule involved in colonization and invasion, is a promising vaccine candidate against amoebiasis. Gal-lectin is known to induce Th1 cytokines in macrophages and spleen cells in vitro, and a Th1 response is thought to be protective against ALA. In this study, we report the use of cytosine guanine oligodeoxynucleotide (CpG-ODN) as adjuvant to augment Th1 responses against Gal-lectin in the gerbil model of ALA. Gerbils were vaccinated intramuscularly with the native Gal-lectin plus CpG-ODN or a paired non-CpG control GpC-ODN, and control gerbils received CpG-ODN alone. One week after the last boost gerbils were challenged intrahepatically with 10(6) amoebae. Gerbils receiving CpG-ODN as adjuvant with Gal-lectin were completely protected against the development of ALA, whereas 50% of gerbils receiving GpC-ODN and Gal-lectin developed ALA and 85% of controls developed ALA. Stronger lymphoproliferation in response to the Gal-lectin and higher prechallenge titers of serum Gal-lectin-specific antibodies, capable of blocking amoebic adherence, were observed when CpG-ODN was used as adjuvant. Gerbils vaccinated with CpG-ODN and Gal-lectin also had significantly higher levels of gamma interferon, interleukin-12 (IL-12), and IL-2 mRNA than controls. These data indicate that CpG-ODN can enhance the Th1 responses, which improve the protective effects of Gal-lectin. This is the first report of the use of CpG as a potent Th1 adjuvant with Gal-lectin to increase protection against ALA formation.

Considerations for development of whole cell bacterial vaccines to prevent diarrheal diseases in children in developing countries

Enteric pathogens constitute a major pediatric threat in the developing world through their impact on morbidity and mortality, physical and cognitive development and cause and effect relationship with malnutrition. Although many bacterial pathogens can cause diarrheal diseases, a group of less than 10 including Shigella spp., enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, and possibly, Campylobacter jejuni account for a significant percentage of these diseases in developing countries. Rotavirus is also a major cause of diarrheal diseases. Vaccines against these agents offer a potentially effective control measure against these diseases, but safe, practical, and effective vaccines for many of these agents have yet to be realized. Many vaccine development approaches are under investigation, but the one that is currently most advanced and that has been most widely applied to enteric pathogens is the use of orally administered live or killed whole pathogen preparations. If inactivated, these vaccines will probably be administered as multiple doses with approximately 10(10) to 10(11) total particles per dose, but they are relatively safe for oral administration. Further, they may not require a buffer for delivery and can be stored in liquid formulations. Fewer doses may be required for some live attenuated pathogen vaccines, but a buffer will most likely be required for oral delivery and the product must be stored in a dried formulation. Also, safety becomes more of a concern with live pathogens depending on the degree of attenuation, host immunocompetence, and the total number and kinds of attenuated pathogens which may be present in a combined agent vaccine. Both live and killed whole pathogen vaccines can be immunogenic and have the possibility to serve as vectors for other antigens. Although many organisms and serotypes are clinically important, by exploiting antigenic cross reactivity and using some pathogen components as vectors for cloned antigens of other pathogens, it could be possible to induce immunity against major enteric pathogens/serotypes with <10 whole pathogen components in a multi-agent vaccine. Safe and effective mucosal adjuvants may in the future be useful in whole pathogen vaccines, but they do not seem to be essential for immunization. Further, dietary supplements such as zinc, mixed routes of delivery and new regimens are under study which may in the future enhance further the effectiveness of the whole pathogen vaccines which now seem realizable in the near term. For this to happen, however, a coordinated and committed effort is necessary now to address the immunologic, regulatory, manufacturing, testing and implementation issues which will be involved in the realization of this important product to benefit children's health worldwide.

Immunostimulatory CpG motifs induce CTL responses to HIV type I oligomeric gp140 envelope protein

In the present study we investigated the immunomodulatory effects of two adjuvants, liposomal lipid A [L(LA)] and CpG-containing oligodeoxynucleotides (CpG ODN), to the HIV-1 ogp140 envelope protein. Administration of each of these adjuvants separately with unencapsulated ogp140 resulted in low antibody titres. Encapsulation of ogp140 in liposomes containing lipid A resulted in a sixfold increase in anti-ogp140 antibodies. The antibody titres were further enhanced threefold by the addition of CpG ODN. Priming and boosting BALB/c mice with unencapsulated ogp140 with L(LA) or encapsulation in liposomes containing lipid A induced a mixed Th1/Th2 type of immune response. In contrast, immunization with L(ogp140 + LA) plus CpG ODN switched the immune response to a Th-1 response with elevated anti-ogp140 IgG2a antibodies and IFN-gamma levels. Both adjuvants induced excellent ogp140-specific proliferative and CTL responses. Therefore, for the induction of high titre antibodies, but not for cellular responses, the antigen and lipid A have to be present in the same liposomes. These results can have significant implications in directing the Th1 or Th2 differentiation of antigen-specific immune responses in the context of vaccine development.

CpG oligodeoxynucleotides stimulate immune cell proliferation but not specific antibody production in rainbow trout (Oncorhynchus mykiss)

Bacterial DNA and CpG ODN have both been shown to have immunostimulatory effects in mammals, activating APCs and inducing a potent Th1 type immune response. They have also been shown to have a strong adjuvant effect and up-regulate MHC class 2 expression in murine cells, augment human and murine NK cell lytic activity, activate human B cells and induce murine B cell proliferation. However, little work has been carried out with regard to their effects on the piscine immune system. Here it is shown that various CpG ODN induce proliferation of peripheral blood leucocytes, spleen and head kidney cells from rainbow trout although, at the range of concentrations tested CpG ODN 2133 lacked the ability to induce specific antibody production to a protein antigen.

Herpes simplex virus type 1 DNA is immunostimulatory in vitro and in vivo

Recently, prokaryotic DNAs containing unmethylated CpG motifs have been shown to be intrinsically immunostimulatory both in vitro and in vivo, tending to promote Th1-like responses. In contrast, CpG dinucleotides in mammalian DNAs are extensively methylated on cytosines and hence immunologically inert. Since the herpes simplex virus (HSV) genome is unmethylated and G+C rich, we predicted that CpG motifs would be highly prevalent in the HSV genome; hence, we examined the immunostimulatory potential of purified HSV DNA in vitro and in vivo. Mouse splenocyte cultures treated with HSV DNA or HSV-derived oligodeoxyribonucleotides (ODNs) showed strong proliferative responses and production of inflammatory cytokines (gamma interferon [IFN-gamma], tumor necrosis factor [TNF], and interleukin-6 [IL-6]) in vitro, whereas splenocytes treated with mammalian CV-1 DNA or non-CpG ODN did not. After immunization with ovalbumin (OVA), only splenocytes from mice immunized with HSV DNA or HSV-ODN as the adjuvants proliferated strongly and produced typical Th1 responses, including CD8(+) cytotoxic T-lymphocyte responses, upon restimulation with OVA. Furthermore, HSV-ODN synergized with IFN-gamma to induce nitric oxide (NO), IL-6, and TNF production from macrophages. These results demonstrate that HSV DNA and HSV-ODN are immunostimulatory, driving potent Th1 responses both in vitro and in vivo. Considering that HSV DNA has been found to persist in nonneuronal cells, these results fuel speculation that HSV DNA might play a role in pathogenesis, in particular, in diseases like herpes stromal keratitis (HSK) that involve chronic inflammatory responses in the absence of virus or viral antigens.

IL-13 effector functions

IL-13 was first recognized for its effects on B cells and monocytes, where it upregulated class II expression, promoted IgE class switching and inhibited inflammatory cytokine production. It was also thought to be functionally redundant with IL-4. However, studies conducted with knockout mice, neutralizing antibodies, and novel antagonists demonstrate that IL-13 possesses several unique effector functions that distinguish it from IL-4. Resistance to most gastrointestinal nematodes is mediated by type-2 cytokine responses, in which IL-13 plays a dominant role. By regulating cell-mediated immunity, IL-13 modulates resistance to intracellular organisms including Leishmania major, Leishmania mexicana, and Listeria monocytogenes. In the lung, IL-13 is the central mediator of allergic asthma, where it regulates eosinophilic inflammation, mucus secretion, and airway hyperresponsiveness. Manipulation of IL-13 effector function may also prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth. IL-13 can also inhibit tumor immunosurveillance. As such, inhibitors of IL-13 might be effective as cancer immunotherapeutics by boosting type-1-associated anti-tumor defenses. Finally, IL-13 was revealed as a potent mediator of tissue fibrosis in both schistosomiasis and asthma, which indicates that it is a key regulator of the extracellular matrix. The mechanisms that regulate IL-13 production and/or function have also been investigated, and IL-4, IL-12, IL-18, IFN-gamma, IL-10, TGF-beta, TNF-alpha, and the IL-4/IL-13 receptor complex play important roles. This review highlights the effector functions of IL-13 and describes multiple pathways for modulating its activity in vivo.

Creating space: an antigen-independent, CpG-induced peripheral expansion of naive and memory T lymphocytes in a full T-cell compartment

Many of the mechanisms that govern T-cell homeostasis remain obscure. Here we report that repeated administration of synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG-ODN) into mice induces a systemic antigen-independent expansion of naive and memory T cells in a full T-cell compartment. Expansion of T cells was observed on both CD4(+) and CD8(+) T-cell subsets and was produced not by inducing the proliferation of the cells but by preventing their death. The antiapoptotic effects of CpG-ODN on T cells were observed against activation-induced death and growth factor withdrawal-mediated death. The ability of CpG-ODN to protect T cells from these forms of death was associated with the up-regulation of antiapoptotic gene products including c-FLIP, bcl-xL, and, to some extent, bcl-2. The effect of CpG-ODN on naive and memory T cells required the expression of CD28 and was not dependent on the presence of B lymphocytes, suggesting that other antigen-presenting cells that respond to CpG-ODN, such as dendritic cells, may provide antiapoptotic signals to T cells in an antigen-independent but CD28/B7-dependent fashion. The present findings suggest that CpG-ODN can disrupt normal T-cell homeostasis not by acting as a mitogen but by preventing T-cell death that normally takes place as a mechanism to maintain steady-state levels of T cells. These findings support a potential means to expeditiously replenish and maintain the peripheral lymphocyte population after severe immunodepletion such as that which occurs in HIV-infected individuals and individuals undergoing cytoablative therapies.

Lipopolysaccharide and CpG DNA synergize for tumor necrosis factor-alpha production through activation of NF-kappaB

Unmethylated CpG motifs in bacterial DNA (CpG DNA) activate host innate immune responses synergistically with some other microbial products, such as endotoxins, and may contribute to disease pathogenesis through excessive production of proinflammatory cytokines. Because monocyte-derived tumor necrosis factor (TNF)-alpha is an important mediator of disease, we investigated whether CpG DNA and lipopolysaccharide (LPS) synergize for inducing TNF-alpha biosynthesis. CpG DNA and LPS synergistically induce TNF-alpha production in RAW264.7 cells and J774 cells through activation of NF-kappaB. Furthermore, transient transfection with a super-repressive mutant of IkappaBalpha (IkappaBalpha-AA) demonstrated that NF-kappaB plays a critical role in CpG DNA-mediated TNF-alpha expression. Like NF-kappaB activation, CpG DNA-induced activation of mitogen-activated protein kinases (MAPK) regulates TNF-alpha production. Both extracellular receptor kinase (ERK) and p38 can regulate TNF-alpha gene transcription induced by CpG DNA. Although CpG DNA at the higher concentration slightly enhanced LPS-mediated phosphorylation of ERK, it did not alter the LPS-mediated activation of c-Jun N-terminal kinase and p38. In addition, CpG DNA showed little or no enhancement of LPS-mediated AP-1 activation. These results suggest that CpG DNA- and LPS-mediated signals converge at or above the level of NF-kappaB and ERK, and that there are distinct, as well as common, signaling pathways which are utilized by both CpG DNA and LPS for activating various transcription factors and MAPK.

Vaccination of cattle against Mycobacterium bovis

Protection of cattle against bovine tuberculosis by vaccination could be an important control strategy in countries where there is persistence of Mycobacterium bovis infection in wildlife and in developing countries where it is not economical to implement a 'test and slaughter' control programme. Early field trials with Bacille Calmette Guerin (BCG) M. bovis vaccine in cattle produced disappointing results, with induction of tuberculin skin-test reactivity following vaccination and low levels of protection. However, recent studies using a low dose of BCG vaccine in cattle have produced more encouraging results and field trials should now be carried out in developing countries to determine whether this low dose BCG vaccination strategy will reduce the spread of infection. The options for new candidate tuberculosis vaccines have increased markedly in the last decade with the advent of new attenuated strains of M. bovis, and sub-unit protein and recombinant DNA vaccines. Some of these new types of vaccines have recently been tested in cattle. New attenuated M. bovis vaccines induced greater protection than BCG vaccine in cattle which had been sensitized to environmental mycobacteria prior to vaccination. In contrast, it has proved difficult to stimulate appropriate immune responses in cattle necessary for protection with sub-unit protein and recombinant DNA vaccines and better immunological adjuvants are required for these types of vaccines. Progress in the development of new tuberculosis vaccines has been very rapid in the past decade and the prospects for vaccination to control and eradicate bovine tuberculosis are encouraging.

Protection of BALB/c mice against Brucella abortus 544 challenge by vaccination with bacterioferritin or P39 recombinant proteins with CpG oligodeoxynucleotides as adjuvant

The P39 and the bacterioferrin (BFR) antigens of Brucella melitensis 16M were previously identified as T dominant antigens able to induce both delayed-type hypersensivity in sensitized guinea pigs and in vitro gamma interferon (IFN-gamma) production by peripheral blood mononuclear cells from infected cattle. Here, we analyzed the potential for these antigens to function as a subunitary vaccine against Brucella abortus infection in BALB/c mice, and we characterized the humoral and cellular immune responses induced. Mice were injected with each of the recombinant proteins alone or adjuvanted with either CpG oligodeoxynucleotides (CpG ODN) or non-CpG ODN. Mice immunized with the recombinant antigens with CpG ODN were the only group demonstrating both significant IFN-gamma production and T-cell proliferation in response to either Brucella extract or to the respective antigen. The same conclusion holds true for the antibody response, which was only demonstrated in mice immunized with recombinant antigens mixed with CpG ODN. The antibody titers (both immunoglobulin G1 [IgG1] and IgG2a) induced by P39 immunization were higher than the titers induced by BFR (only IgG2a). Using a B. abortus 544 challenge, the level of protection was analyzed and compared to the protection conferred by one immunization with the vaccine strain B19. Immunization with P39 and CpG ODN gave a level of protection comparable to the one conferred by B19 at 4 weeks postchallenge, and the mice were still significantly protected at 8 weeks postchallenge, although to a lesser extent than the B19-vaccinated group. Intriguingly, no protection was detected after BFR vaccination. All other groups did not demonstrate any protection.

Nanoparticulate systems for the delivery of antisense oligonucleotides

Antisense oligonucleotides are molecules that are able to inhibit gene expression being therefore potentially active for the treatment of viral infections or cancer. However, because of their poor stability in biological medium and their weak intracellular penetration, colloidal drugs carriers such as nanoparticles were developed for the delivery of oligonucleotides (ODN). ODN associated to nanoparticles were shown to be protected against degradation and to penetrate more easily into different types of cells. As a consequence, nanoparticles were shown to improve the efficiency of ODNs for the inhibition of the proliferation of cells expressing the point mutated Ha-ras gene. In vivo, polyalkylcyanoacrylate (PACA) nanoparticles were able to efficiently distribute the ODNs to the liver whereas the alginate nanosponges could concentrate the ODNs in the lungs. Finally, ODN loaded to PACA nanoparticles were able to improve in mice, the treatment of RAS cells expressing the point mutated Ha-ras gene.

Vaccination with empty plasmid DNA or CpG oligonucleotide inhibits diabetes in nonobese diabetic mice: modulation of spontaneous 60-kDa heat shock protein autoimmunity

Nonobese diabetic (NOD) mice develop insulitis and diabetes through a process involving autoimmunity to the 60-kDa heat shock protein (HSP60). Treatment of NOD mice with HSP60 or with peptides derived from HSP60 inhibits this diabetogenic process. We now report that NOD diabetes can be inhibited by vaccination with a DNA construct encoding human HSP60, with the pcDNA3 empty vector, or with an oligonucleotide containing the CpG motif. Prevention of diabetes was associated with a decrease in the degree of insulitis and with down-regulation of spontaneous proliferative T cell responses to HSP60 and its peptide p277. Moreover, both the pcDNA3 vector and the CpG oligonucleotide induced specific Abs, primarily of the IgG2b isotype, to HSP60 and p277, and not to other islet Ags (glutamic acid decarboxylase or insulin) or to an unrelated recombinant Ag expressed in bacteria (GST). The IgG2b isotype of the specific Abs together with the decrease in T cell proliferative responses indicate a shift of the autoimmune process to a Th2 type in treated mice. These results suggest that immunostimulation by bacterial DNA motifs can modulate spontaneous HSP60 autoimmunity and inhibit NOD diabetes.

A two B-Z junction containing DNA resolves into an all right-handed double-helix

Natural and artificial oligonucleotides are capable of assuming many different conformations and functions. Here we present results of an NMR restrained molecular modelling study on the conformational preferences of the modified decanucleotide d((m)C1G2(m)C3G4C5(L)G6(L)(m)C7G8(m)C9G10) .d((m)C11G12(m)C13G14C15(L)G (L)16(m)C17-G18(m)C19G20 ) which contains L deoxynucleotides in its centre. This chimeric DNA was expected to form a right-left-right-handed B-type double-helix (BB*B) at low salt concentration. Actually, it matured into a fully right-handed double helix with its central C(L)pG(L) core forming a right-handed Z-DNA helix embedded in a B-DNA matrix (BZ*B). The interplay between base-base and base-sugar stackings within the core and its immediately adjacent residues was found to be critical in ensuring the stabilisation of the right-handed helix. The structure could serve as a model for the design of antisense oligonucleotides resistant to nucleases and capable of hybridising to natural DNAs and RNAs.

Effective induction of simian immunodeficiency virus-specific systemic and mucosal immune responses in primates by vaccination with proviral DNA producing intact but noninfectious virions

We report a pilot evaluation of a DNA vaccine producing genetically inactivated simian immunodeficiency virus (SIV) particles in primates, with a focus on eliciting mucosal immunity. Our results demonstrate that DNA vaccines can be used to stimulate strong virus-specific mucosal immune responses in primates. The levels of immunoglobulin A (IgA) detected in rectal secretions of macaques that received the DNA vaccine intradermally and at the rectal mucosa were the most striking of all measured immune responses and were higher than usually achieved through natural infection. However, cytotoxic T lymphocyte responses were generally low and sporadically present in different animals. Upon rectal challenge with cloned SIVmac239, resistance to infection was observed, but some animals with high SIV-specific IgA levels in rectal secretions became infected. Our results suggest that high levels of IgA alone are not sufficient to prevent the establishment of chronic infection, although mucosal IgA responses may have a role in reducing the infectivity of the initial viral inoculum.

New tuberculosis vaccines based on attenuated strains of the Mycobacterium tuberculosis complex

The world urgently needs a better tuberculosis vaccine. Bacille Calmette-Guerin (BCG), an attenuated strain of Mycobacterium bovis, has been very widely used as a vaccine for many years but has had no major effect on reducing the incidence of tuberculosis. A number of alternative living and non-living vaccines are being investigated. Live vaccine candidates include genetically modified forms of BCG, genetically attenuated strains of the Mycobacterium tuberculosis complex and genetically engineered vaccinia virus and Salmonella strains. Non-living vaccine candidates include killed mycobacterial species, protein subunits and DNA vaccines. One requirement for acceptance of any new vaccine will be a favourable comparison of the protection it induces relative to BCG in a range of animal models, some of which may need further development. Molecular genetic techniques are now available that enable production of live attenuated strains of the M. tuberculosis complex with vaccine potential. In the first of two broadly different approaches that are being used, large numbers of mutants are produced by transposon mutagenesis or illegitimate recombination and are screened for properties that correlate with attenuation. In the second approach, putative genes that may be required for virulence are identified and subsequently inactivated by allelic exchange. In both approaches, mutants that are attenuated need to be identified and subsequently tested for their vaccine efficacy in animal models. Many mutants of the M. tuberculosis complex have now been produced and the vaccine properties of a substantial number will be assessed in the next 3 years.

Dengue virus type 1 DNA vaccine induces protective immune responses in rhesus macaques

A candidate DNA vaccine expressing dengue virus type 1 pre-membrane and envelope proteins was used to immunize rhesus macaques. Monkeys were immunized intramuscularly (i.m.) or intradermally (i.d.) by three or four 1 mg doses of vaccine, respectively. Monkeys that were inoculated i.m. seroconverted more quickly and had higher antibody levels than those that were inoculated i.d. The sera exhibited virus-neutralizing activity, which declined over time. Four of the eight i.m.-inoculated monkeys were protected completely from developing viraemia when challenged 4 months after the last dose with homologous dengue virus. The other four monkeys had reduced viraemia compared with the control immunized monkeys. The i.d. -inoculated monkeys showed no reduction in viraemia when challenged with the virus. All vaccinated monkeys showed an anamnestic antibody response, indicating that they had established immunological memory. Vaccine-induced antibody had an avidity index similar to that of antibody induced by virus infection; however, no clear correlation was apparent between antibody avidity and virus neutralization titres.

Repeated administration of cytosine-phosphorothiolated guanine-containing oligonucleotides together with peptide/protein immunization results in enhanced CTL responses with anti-tumor activity

The development of therapeutic anti-cancer vaccines designed to elicit CTL responses with anti-tumor activity has become a reality thanks to the identification of several tumor-associated Ags and their corresponding peptide T cell epitopes. However, peptide-based vaccines, in general, fail to elicit sufficiently strong CTL responses capable of producing therapeutic anti-tumor effects (i.e., prolongation of survival, tumor reduction). Here we report that repeated administration of synthetic oligonucleotides containing foreign cytosine-phosphorothiolated guanine (CpG) motifs increased 10- to 100-fold the CTL response to immunization with various synthetic peptides corresponding to well-known T cell epitopes. Moreover, repeated CpG administration allowed the induction of CTL to soluble protein even in the absence of additional adjuvant. Our results indicate that the potentiating effect of CpG in CTL responses required the participation of Th lymphocytes. Repeated CpG administration resulted in overt splenomegaly and lymphadenopathy with a significant increase in the numbers of CTL precursors and dendritic cells. Protein vaccination in combination with repeated CpG therapy was effective in delaying tumor cell growth and extending survival in mice bearing melanoma tumors. These findings support the contention that repeated administration of CpG-oligonucleotides enhances the effect of peptide and protein vaccines leading to potent anti-tumor responses, presumably through the induction of Th1 and dendritic cells, which are essential for optimal CTL responses. The immunostimulatory properties of CpG motifs may be key in inducing a consistent long term immunity to tumor-associated Ags when using peptides or proteins as T cell-inducing vaccines.

CpG DNA induces stronger immune responses with less toxicity than other adjuvants

The ability to augment protective immune responses with minimal side effects is quintessential for a good adjuvant. This study has compared various adjuvants that are used in animal research (Freund's complete and incomplete adjuvants, Titermax Gold), are licensed for human use (alum), or are in clinical testing for humans (monophosphoryl lipid, CpG DNA), for their ability to augment humoral responses to a model antigen (hepatitis B surface antigen) and for the degree of damage they caused in the injected muscle. According to the data, the adjuvant combination CpG DNA+alum had the greatest potential to augment immune responses with minimal side effects at the injection site. Evaluation of antibody isotypes indicated Th2 responses (no IgG2a) with all adjuvants except monophosphoryl lipid and CpG DNA, which gave mixed Th1/Th2 responses (IgG1 and IgG2a). Strong Th1 responses (predominantly IgG2a) were obtained with combinations of CpG DNA with other adjuvants.

Intravitreal administration of antisense oligonucleotides: potential of liposomal delivery

Antisense oligonucleotides are short synthetic fragments of genes that are able to inhibit gene expression after being internalized by cells. They can therefore be used as antiviral compounds particularly, for the treatment of ocular viral infections (i.e. Herpes simplex virus or Cytomegalovirus, CMV). Antisense oligonucleotides are however poorly stable in biological fluids and their intracellular penetration is limited. Although oligonucleotides are now currently used in therapeutics for the treatment of CMV by intravitreal injection (Vitravene) their main drawbacks impose to repeat the number of administrations which can be very harmful and damaging. A system that is able to permit a protection of oligonucleotides against degradation and their slow delivery into the vitreous would be more favorable for improving patient compliance. The use of liposomes for intravitreal administration can be very promising since these lipid vesicles are able to protect oligonucleotides against degradation by nucleases and they allow to increase the retention time of many drugs in the vitreous. In this review, the potentialities of liposomes for the intravitreal delivery of oligonucleotides will be discussed.

CpG oligonucleotides can prophylactically immunize against Th2-mediated schistosome egg-induced pathology by an IL-12-independent mechanism

Using a Schistosoma mansoni egg-induced granuloma model, we examined the ability of CpG oligodeoxynucleotides (ODN) to suppress Th2-type cytokine expression and to prophylactically immunize against Th2-dependent pulmonary pathology. The mechanism was examined by studying Th2 response regulation in cytokine-deficient mice. Surprisingly, our findings revealed several functions of CpG DNA that were completely IL-12 independent. Most striking was the marked suppression in Th2 cytokine expression and granulomatous inflammation observed in egg/CpG-sensitized IL-12-deficient mice. Immune deviation was not dependent on NK or B cells. However, a role for IL-10, B7.1, and CD40 expression in Th2 response inhibition was suggested. Indeed, CpG ODN up-regulated all three elements in both wild-type and IL-12-deficient mice. The role of IL-10 was demonstrated in mice exhibiting combined deficiencies in IL-12 and IL-10. Here, a marked increase in egg-specific IL-4/IL-5-producing cells confirmed a role for both cytokines in Th2 response inhibition. Nevertheless, the frequency of Th2-producing cells was again reduced by CpG ODN. However, in marked contrast to IL-12-deficient animals, a significant increase in IFN-gamma-producing cells likely explains the reduced Th2 response in IL-10/IL-12-deficient mice. Thus, a novel IL-12-independent type 1-inducing pathway was revealed in the combined absence of IL-12 and IL-10. Together, these data demonstrate 1) that the Th1-promoting activity of CpG DNA is controlled by IL-12 and IL-10, and 2) that Th2 response inhibition by CpG ODN involves IL-12-independent changes in IL-10 and costimulatory molecule expression. These findings illustrate the utility of CpG DNA as adjuvants for vaccines designed to prevent Th2-dependent immunopathology.