Activation of the innate immune system by CpG oligodeoxynucleotides: immunoprotective activity and safety

Effects of skeletal unloading on the antibody repertoire of tetanus toxoid and/or CpG treated C57BL/6J mice

Spaceflight affects the immune system, but the effects on the antibody repertoire, responsible for humoral immunity, has not been well explored. In particular, the complex gene assembly and expression process; including mutations, might make this process vulnerable. Complementarity determining region 3 (CDR3), composed of parts of the V-(D-)J-gene segments, is very important for antigen binding and can be used as an important measure of variability. Skeletal unloading, and the physiological effects of it, parallel many impacts of space flight. Therefore, we explored the impact of skeletal unloading using the antiorthostatic suspension (AOS) model. Animals were experimentally challenged with tetanus toxoid (TT) and/or the adjuvant CpG. Blood was analyzed for anti-TT antibody and corticosterone concentrations. Whole spleen tissue was prepared for repertoire characterization. AOS animals showed higher levels of corticosterone levels, but AOS alone did not affect anti-TT serum antibody levels. Administration of CpG significantly increased the circulating anti-TT antibody concentrations. AOS did alter constant gene usage resulting in higher levels of IgM and lower levels of IgG. CpG also altered constant gene region usage increasing usage of IgA. Significant changes could be detected in multiple V-, D-, and J-gene segments in both the heavy and light chains in response to AOS, TT, and CpG treatments. Analysis of class-switched only transcripts revealed a different pattern of V-gene segment usage than detected in the whole repertoire and also showed significant alterations in gene segment usage after challenge. Alterations in V/J pairing were also detected in response to challenge. CDR3 amino acid sequence overlaps were similar among treatment groups, though the addition of CpG lowered overlap in the heavy chain. We isolated 3,045 whole repertoire and 98 potentially TT-specific CDR3 sequences for the heavy chain and 569 for the light chain. Our results demonstrate that AOS alters the repertoire response to challenge with TT and/or CpG.

Liposome-encapsulated CpG enhances antitumor activity accompanying the changing of lymphocyte populations in tumor via intratumoral administration

Although oligodeoxynucleotides containing CpG motifs (CpG-ODN) are potent immune stimulators, the use of natural CpG-ODN--phosphodiester-backbone CpG--has been limited due to its instability by nuclease in vivo. The aim of this study is to investigate the anticancer efficiency of CpG-ODN capsulated using liposome, which enhances the stability of CpG-ODN. We formulated lipoplex, encapsulated natural CpG-ODN from Mycobacterium bovis with liposome, and tested its immune stimulatory activity in vitro and in vivo. The lipoplex induced a systemic innate immune response in vivo and stimulated dendritic cells, but not macrophages, to stimulate proinflammatory cytokines such as tumor necrosis factor alpha and interleukin-6 in vitro. As expected, the lipoplex effectively mediated the prolonged cancer-therapeutic activity against B16 melanoma, which was dependent on natural killer and CD8(+) T cells. The therapeutic activity was observed after only intratumoral administration of lipoplex among several treatment routes. Intratumoral treatment of lipoplex significantly increased the populations of natural killer and CD8(+) T cells and reduced regulatory CD4(+) T cell recruitment, which was correlated with expression profiles of chemokines (CCL1, CCL3, CXCL1, CXCL10, and CCL22). The antitumor therapeutic effect of lipoplex was dependent on the altered lymphocyte population that might be developed by the profile of intratumoral chemokine expression.

Vaccination with L. infantum chagasi nucleosomal histones confers protection against new world cutaneous leishmaniasis caused by Leishmania braziliensis

Background

Nucleosomal histones are intracellular proteins that are highly conserved among Leishmania species. After parasite destruction or spontaneous lysis, exposure to these proteins elicits a strong host immune response. In the present study, we analyzed the protective capability of Leishmania infantum chagasi nucleosomal histones against L. braziliensis infection using different immunization strategies.

Methodology/Principal Findings

BALB/c mice were immunized with either a plasmid DNA cocktail (DNA) containing four Leishmania nucleosomal histones or with the DNA cocktail followed by the corresponding recombinant proteins plus CpG (DNA/Protein). Mice were later challenged with L. braziliensis, in the presence of sand fly saliva. Lesion development, parasite load and the cellular immune response were analyzed five weeks after challenge. Immunization with either DNA alone or with DNA/Protein was able to inhibit lesion development. This finding was highlighted by the absence of infected macrophages in tissue sections. Further, parasite load at the infection site and in the draining lymph nodes was also significantly lower in vaccinated animals. This outcome was associated with increased expression of IFN-γ and down regulation of IL-4 at the infection site.

Conclusion

The data presented here demonstrate the potential use of L. infantum chagasi nucleosomal histones as targets for the development of vaccines against infection with L. braziliensis, as shown by the significant inhibition of disease development following a live challenge.

Adjuvants for Leishmania vaccines: from models to clinical application

Two million new cases of leishmaniasis occur every year, with the cutaneous leishmaniasis (CL) presentation accounting for approximately two-thirds of all cases. Despite the high incidence rates and geographic expansion of the disease, CL remains a neglected tropical disease without effective intervention strategies. Efforts to address this deficit have given rise to the experimental murine model of CL. By virtue of its simplicity and pliability, the CL model has been used to provide substantial information regarding cellular immunity, as well as in the discovery and evaluation of various vaccine adjuvants. The CL model has facilitated in vivo studies of the mechanism of action of many adjuvants, including the TLR4 agonist monophosphoryl lipid A, the TLR7/8 agonist imiquimod, the TLR9 agonist CpG, adenoviral vectors, and the immunostimulatory complexes. Together, these studies have helped to unveil the requirement for certain types of immune responses at specific stages of CL disease and provide a basis to aid the design of effective second-generation vaccines for human CL. This review focuses on adjuvants that have been tested in experimental CL, outlining how they have helped advance our understanding of the disease and ultimately, how they have performed when applied within clinical trials against human CL.

Superior protective immunity against murine listeriosis by combined vaccination with CpG DNA and recombinant Salmonella enterica serovar typhimurium

Preexisting antivector immunity can severely compromise the ability of Salmonella enterica serovar Typhimurium live vaccines to induce protective CD8 T-cell frequencies after type III secretion system-mediated heterologous protein translocation in orally immunized mice. To circumvent this problem, we injected CpG DNA admixed to the immunodominant p60(217-225) peptide from Listeria monocytogenes subcutaneously into BALB/c mice and coadministered a p60-translocating Salmonella strain by the orogastric route. The distribution of tetramer-positive p60(217-225)-specific effector and memory CD8 T cells was analyzed by costaining of lymphocytes with CD62L and CD127. In contrast to the single oral application of recombinant Salmonella or single immunization with CpG and p60, in the spleens from mice immunized with a combination of both vaccine types a significantly higher level of p60-specific CD8 T cells with a predominance of the effector memory T-cell subset was detected. In vivo protection studies revealed that this CD8 T-cell population conferred sterile protective immunity against a lethal infection with L. monocytogenes. However, p60-specific central memory CD8 T cells induced by single vaccination with CpG and p60 were not able confer effective protection against rapidly replicating intracellular Listeria. In conclusion, we provide compelling evidence that the combination of Salmonella type III-mediated antigen delivery and CpG immunization is an attractive novel vaccination strategy to modulate CD8 differentiation patterns toward distinct antigen-specific T-cell subsets with favorable protective capacities.

Dihydrotestosterone inhibits tumor necrosis factor alpha induced interleukin-1alpha mRNA expression in rheumatoid fibroblast-like synovial cells

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects multiple synovial joints. Proinflammatory cytokines, such as interleukin-1 (IL-1) and tumor necrosis factor (TNF)alpha play important roles as principle inflammatory and destructive components of the disease. RA is known to be associated with significant gender differences in its prevalence and clinical features. We found that a potent androgen, 5alpha-dihydrotestosterone (DHT) inhibits IL-1alpha mRNA expression induced by TNFalpha and the DHT effect was inhibited by an androgen receptor antagonist, hydroxyflutamide (OHF). DHT inhibited the NF-kappaB activation induced by TNFalpha in a manner dependent on the androgen receptor (AR). These results suggest that DHT inhibits the TNFalpha-induced IL-1alpha mRNA expression by inhibiting NF-kappaB activation, and contributes to the gender differences of the disease.

Effects of multiple copies of CpG on DNA vaccination

It has previously been demonstrated that a dose-dependent enhancement of immune response is derived from immunization with several copies of the CpG motif. Following that lead, we sought to incorporate a higher copy number of CpG motifs into an expression construct to evaluate the augmentation of immune responses. By multiple insertions, 30 copies of the CpG motif were cloned into the backbone of an expression construct encoding the foot-and-mouth disease virus (FMDV) capsid protein VP1. After intramuscular immunization, an augmented immune response with significantly increased levels of the specific antibody, T-cell proliferation, and IFN-gamma in Balb/c mice was observed. Compared to chemically synthesized CpG ODN, application of such a multicopy of CpG sequences within the expression backbone for DNA vaccination strategy is feasible and warranted.

Suppressive Effect of Kanzo-bushi-to, a Kampo Medicine, on Collagen-Induced Arthritis

Kanzo-bushi-to (KBT) is a traditional Japanese herbal medicine (Kampo medicine), which is used in Japan to treat rheumatoid arthritis. In the present study, we investigated the suppressive effect of KBT on collagen-induced arthritis (CIA) and further studied the underlying mechanism. CIA was induced in male DBA/1J mice by immunization with bovine type II collagen, followed by a booster injection 21 d later. KBT was given at a dose of 430 mg/kg/d from three days before the first immunization to the end of the experiment. KBT suppressed CIA development effectively and further protected focal bone erosion and bone destruction as evidenced by the reduced histological score. Histochemical examination revealed that KBT decreased TRAP-positive cells at the synovium-bone interface and at the sites of focal bone erosion, coincident with the findings that RANKL/OPG mRNA ratio was significantly reduced by KBT treatment. KBT also decreased mRNA levels of M-CSF and iNOS in joints and of iNOS in peritoneal macrophages. In conclusion, KBT prevented osteoclast generation by decreasing RANKL/OPG ratio and M-CSF mRNA levels, resulting in reduction in bone erosion and destruction. In addition, KBT has anti-inflammatory effect such as the suppression of iNOS expression in peritoneal macrophages and joints of CIA mice. These finding suggests that KBT is a potential new therapeutic agent for the treatment of RA.

Coinjection with CpG-containing immunostimulatory oligodeoxynucleotides reduces the pathogenicity of a live vaccine against cutaneous Leishmaniasis but maintains its potency and durability

The inoculation of live, nonattenuated Leishmania major to produce a lesion in a selected site that heals, referred to as leishmanization, is to date the only vaccine against leishmaniasis that has proven to be effective in humans. Its use has been restricted or abandoned entirely, however, due to safety concerns. In an attempt to develop a leishmanization protocol that minimizes pathology while maintaining long-term protection, live parasites were coinjected with CpG-containing immunostimulatory oligodeoxynucleotides (CpG ODNs) alone or in combination with whole-cell lysates of heat-killed L. major promastigotes bound to alum (ALM). C57BL/6 mice infected intradermally by using L. major plus CpG ODN with or without ALM developed few or no dermal lesions and showed an early containment of parasite growth, while mice infected with L. major with or without ALM developed sizable dermal lesions that required up to 10 weeks to heal. The CpG ODNs provoked a transient inflammation that included an early recruitment and accumulation of gamma interferon-producing CD4(+) lymphocytes in the site. Attenuation of the live vaccine did not compromise its ability to confer long-term immunity, as mice receiving L. major and CpG ODN plus ALM were totally protected against reinfection with L. major for up to 6 months. By comparison, the immunity elicited by two efficient nonlive vaccines began to wane by 6 months. Our results suggest that immune modulation using CpG ODNs might be a practical approach to improving the safety of a highly effective live vaccine that has already been widely applied.

Divergent synthetic nucleotide motif recognition pattern: design and development of potent immunomodulatory oligodeoxyribonucleotide agents with distinct cytokine induction profiles

Unmethylated CpG dinucleotides present within certain specific sequence contexts in bacterial and synthetic DNA stimulate innate immune responses and induce cytokine secretion. Recently, we showed that CpG DNAs containing two 5'-ends, immunomers, are more potent in both regards. In this study, we show that an immunomer containing a synthetic CpR motif (R = 2'-deoxy-7-deazaguanosine) is a potent immunostimulatory agent. However, the profile of cytokine induction is different from that with immunomers containing a natural CpG motif. In general, a CpR immunomer induced higher interleukin (IL)-12 and lower IL-6 secretion. Compared with conventional CpG DNAs, both types of immunomers showed a rapid and enhanced activation of the transcription factor NF-kappaB in J774 cells. NF-kappaB activation by CpG DNA corresponded to degradation of IkappaBalpha in J774 cells. All three immunostimulatory oligonucleotides activated the p38 mitogen-activated protein kinase pathway as expected. Immunomers containing CpG and CpR motifs showed potent reversal of the antigen-induced Th2 immune response towards a Th1 type in antigen-sensitized mouse spleen cell cultures. Immunomers containing a CpR motif showed significant antitumor activity in nude mice bearing MCF-7 human breast cancer and U87MG glioblastoma xenografts. These studies suggest the ability for a divergent synthetic nucleotide motif recognition pattern of the receptor involved in the immunostimulatory pathway and the possibility of using synthetic nucleotides to elicit different cytokine response patterns.

Peritumoral CpG DNA elicits a coordinated response of CD8 T cells and innate effectors to cure established tumors in a murine colon carcinoma model

The immune system of vertebrates is able to detect bacterial DNA based on the presence of unmethylated CpG motifs. We examined the therapeutic potential of oligodeoxynucleotides with CpG motifs (CpG ODN) in a colon carcinoma model in BALB/c mice. Tumors were induced by s.c. injection of syngeneic C26 cells or Renca kidney cancer cells as a control. Injection of CpG ODN alone or in combination with irradiated tumor cells did not protect mice against subsequent tumor challenge. In contrast, weekly injections of CpG ODN into the margin of already established tumors resulted in regression of tumors and complete cure of mice. The injection site was critical, since injection of CpG ODN at distant sites was not effective. Mice with two bilateral C26 tumors rejected both tumors upon peritumoral injection of one tumor, indicating the development of a systemic immune response. The tumor specificity of the immune response was demonstrated in mice bearing a C26 tumor and a Renca tumor at the same time. Mice that rejected a tumor upon peritumoral CpG treatment remained tumor free and were protected against rechallenge with the same tumor cells, but not with the other tumor, demonstrating long term memory. Tumor-specific CD8 T cells as well as innate effector cells contributed to the antitumor activity of treatment. In conclusion, peritumoral CpG ODN monotherapy elicits a strong CD8 T cell response and innate effector mechanisms that seem to act in concert to overcome unresponsiveness of the immune system toward a growing tumor.

Use of immunostimulatory sequence-containing oligonucleotides as topical therapy for genital herpes simplex virus type 2 infection

Synthetic oligonucleotides containing CpG motifs in specific sequence contexts have been shown to induce potent immune responses. We have evaluated mucosal administration of two immunostimulatory sequence (ISS)-containing phosphorothioate-stabilized oligonucleotides for antiherpetic efficacy in animal models. The ISS oligonucleotides, suspended in phosphate-buffered saline, were tested in mouse and guinea pig vaginal models of herpes simplex virus type 2 (HSV-2) infection. For comparison, groups of untreated, non-ISS oligonucleotide-treated, and acyclovir-treated animals also were monitored. The results indicated that vaginal epithelial application of ISS (up to 6 h after viral inoculation) with mice lethally challenged with HSV-2 delayed disease onset and reduced the number of animals that developed signs of disease (P = 0.003). ISS application significantly increased survival rates over those of controls (P = 0.0014). The ISS also impacted an established infection in the guinea pig model of HSV-2 disease. A single administration of ISS (21 days after viral inoculation) significantly reduced the frequency and severity of HSV-2 lesions compared to results with non-ISS oligonucleotide-treated and untreated guinea pigs (P < 0.01). HSV-2 is shed from the vaginal cavity of the guinea pig in the absence of lesions, similar to the case with humans. As an additional indication of ISS efficacy, the magnitude of viral shedding also was significantly reduced in ISS-treated animals (P < 0.001). These effects appeared to be immunologically mediated, since ISS had no direct effect on HSV-2 replication in vitro using standard plaque assays. These data suggest that ISS may be useful in the treatment and control of genital herpes in humans.

Comparative efficacy of the Schistosoma mansoni nucleic acid vaccine, Sm23, following microseeding or gene gun delivery

Sm23 is an integral membrane protein expressed widely in the human parasitic worm Schistosoma mansoni. Sm23 has already been shown to elicit protective immune responses following immunization with peptides or DNA constructs. In this study, we evaluated the immunogenicity and the protective efficacy of the Sm23 DNA vaccine using two different intradermal DNA delivery methods: microseeding and gene gun. Using both techniques, all mice immunized with the Sm23-pcDNA construct generated Sm23-specific immunoglobulin (Ig)G antibody, while mice immunized with the control plasmid, pcDNA, did not. Antibody isotypes analysis revealed that microseeding elicited mainly IgG2a and IgG2b antibodies, with relatively low levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio was 0.03, indicative of a Th1 type immune response. In contrast, gene gun immunization resulted in significantly higher levels of IgG1 and IgG3. The relative IgG1/IgG2a ratio in this case was 11, indicative of a Th2 type immune response. No significant difference in the levels of IgG2b was observed. Coimmunization with plasmid DNA encoding either interleukin (IL)-12 or IL-4 by microseeding did not affect the levels of IgG1, while the levels of IgG2a and IgG2b were reduced. On the other hand, the levels of IgG3 were significantly increased by IL-4, but unchanged by IL-12. Importantly, in all experiments, the Sm23-pcDNA vaccine provided statistically significant levels of protection against challenge infection. Microseeding immunizations resulted in higher levels of protection (31-34% protection) than gene gun immunization (18% protection). This suggests that the Th1 type immune response elicited by microseeding immunization was responsible for the higher protection levels. However, the protective effect of the vaccine was not affected by coadministering plasmids encoding either IL-12 or IL-4 using the microseeding technique.

CpG oligodeoxynucleotides as vaccine adjuvants in primates

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs act as immune adjuvants in mice, boosting the humoral and cellular response to coadministered Ags. CpG ODN that stimulate human PBMC are only weakly active in mice. Thus, alternative animal models are needed to monitor the activity and safety of "human" CpG ODN in vivo. This work demonstrates that rhesus macaques recognize and respond to the same CpG motifs that trigger human immune cells. Coadministering CpG ODN with heat-killed Leishmania vaccine provided significantly increased protection of macaques against cutaneous Leishmania infection. These findings indicate that rhesus macaques provide a useful model for studying the in vivo activity of human CpG motifs, and that ODN expressing these motifs act as strong immune adjuvants.

Sterically stabilized cationic liposomes improve the uptake and immunostimulatory activity of CpG oligonucleotides

Immunostimulatory CpG oligonucleotides (ODN) show promise as immune adjuvants, anti-allergens, and immunoprotective agents. Increasing the bioavailability and duration of action of CpG ODN should improve their therapeutic utility. Encapsulating ODN in sterically stabilized cationic liposomes provides protection from serum nucleases while facilitating uptake by B cells, dendritic cells, and macrophages. In a pathogen challenge model, sterically stabilized cationic liposomes encapsulation doubled the duration of CpG ODN-induced immune protection. In an immunization model, coencapsulation of CpG ODN with protein Ag (OVA) magnified the resultant Ag-specific IFN-gamma and IgG responses by 15- to 40-fold compared with Ag plus CpG ODN alone. These findings support the use of sterically stabilized cationic liposomes to significantly enhance the therapeutic efficacy of CpG ODN.