Enhanced Th2 immunity after DNA prime-protein boost immunization with amyloid beta (1-42) plus CpG oligodeoxynucleotides in aged rats

Generation and accumulation of fibrillar amyloid beta (Abeta) is widely considered as the pathogenic basis of neurodegeneration in Alzheimer's disease (AD). Both active immunization with fibrillar Abeta and passive immunization with anti-Abeta antibodies in transgenic mouse models of AD result in prevention/dissociation of Abeta plaque formation and restoration of cognitive functions. However, similar immunization studies in humans had to be halted because 6% of the AD patients developed acute meningoencephalitis, likely due to anti-Abeta specific autoimmune Th1 cells. Hence, making Abeta immunotherapy successful requires production of strong antibody responses without Th1-type immunity. In an attempt to develop safer vaccines, we examined the influence of oligodeoxynucleotides as adjuvant on the Th1 and Th2 immune response to Abeta in aged rats. We further investigated whether a DNA prime-protein boost strategy could elicit a more robust Th2 response. The results of the present study showed that all the animals injected with either Abeta peptide alone or Abeta encoding plasmid alone or plasmid DNA prime followed by peptide boost have elicited specific anti-Abeta antibodies. When co-administered, synthetic oligodeoxynucleotides (ODN) further enhanced the anti-Abeta titres. More importantly, the IgG subclasses of the antibodies generated by DNA prime-peptide boost regimen with ODN as adjuvant were primarily of IgG2b and IgG1 isotypes, suggesting that heterologous immunization strategy along with ODN would be advantageous in eliciting more beneficial Th2-type humoral immune response.     

The influence of CpG motifs on a protein or DNA-based Th2-type immune response against major pollen allergens Bet v 1a, Phl p 2 and Escherichia coli-derived beta-galactosidase

BACKGROUND: DNA immunization and protein immunization with CpG motifs as adjuvants represent promising approaches in allergen-specific immunotherapy. Objective: We investigated the effect of coinjection or prepriming with CpG-ODN on Th2-type responses induced by gene gun and protein immunization. METHODS: BALB/c mice were immunized with the gene gun using plasmid DNA containing the cDNAs coding for the genes of Bet v 1a, Phl p 2 and beta-galactosidase or with the purified Al(OH)(3)-adsorbed proteins. In addition, CpG-ODN were applied by coinjection or by prepriming treatment. Antibody and cytokine responses were measured by ELISA, proliferative and cytotoxic responses were determined by standard labeling procedures. Furthermore, the allergenic activity of sera was measured by passive cutaneous anaphylaxis. RESULTS: Gene gun immunization and protein immunization induced a clear Th2-type response for all antigens. The Th1-promoting effect of CpG-ODN coinjection together with gene gun immunization was restricted to beta-galactosidase as indicated by the increase of IgG2a and a marked expression of IFN-gamma. CpG motifs also increased the specific cytotoxic response against beta-galactosidase. Prepriming with CpG-ODN and gene gun or protein immunization with Bet v 1a exhibited no significant difference to the non-CpG control group. However, sera from mice preprimed with CpG-ODN induced no anaphylaxis with gene gun immunization, but with protein immunization. CONCLUSIONS: The effect of CpG motifs in vivo depends on a variety of parameters like the nature of the antigen and the immunization modality. Furthermore, our studies indicate that a combination of CpG + DNA immunization may be more effective in antagonizing Th2 responses than the combination of CpG + protein immunization.     

Oligodeoxynucleotides lacking CpG dinucleotides mediate Toll-like receptor 9 dependent T helper type 2 biased immune stimulation

Oligodeoxynucleotides (ODN) with unmethylated CpG dinucleotides mimic the immune stimulatory activity of bacterial DNA in vertebrates and are recognized by Toll-like receptor 9 (TLR9). It is also possible to detect immune activation with certain phosphorothioate sequences that lack CpG motifs. These ODN are less potent than CpG ODN and the mechanism by which they stimulate mammalian leucocytes is not understood. We here provide several lines of evidence demonstrating that the effects induced by non-CpG ODN are mediated by TLR9. First, non-CpG ODN could not stimulate cytokine secretion from the splenocytes of TLR9-deficient (TLR9(-/-)) mice. Second, immunization of TLR9(+/+) but not TLR9(-/-) mice with non-CpG ODN enhanced antigen-specific antibody responses, although these were T helper type 2 (Th2)-biased. Third, reactivity to non-CpG ODN could be reconstituted by transfection of human TLR9 into non-responsive cells. In addition, we define a new efficient immune stimulatory motif aside from the CpG dinucleotide that consists of a 5'-TC dinucleotide in a thymidine-rich background. Non-CpG ODN containing this motif induced activation of human B cells, but lacked stimulation of Th1-like cytokines and chemokines. Our study indicates that TLR9 can mediate either efficient Th1- or Th2-dominated effects depending on whether it is stimulated by CpG or certain non-CpG ODN.     

The immunodominant T helper 2 (Th2) response elicited in BALB/c mice by the Leishmania LiP2a and LiP2b acidic ribosomal proteins cannot be reverted by strong Th1 inducers

The search for disease-associated T helper 2 (Th2) Leishmania antigens and the induction of a Th1 immune response to them using defined vaccination protocols is a potential strategy to induce protection against Leishmania infection. Leishmania infantum LiP2a and LiP2b acidic ribosomal protein (P proteins) have been described as prominent antigens during human and canine visceral leishmaniasis. In this study we demonstrate that BALB/c mice infected with Leishmania major develop a Th2-like humoral response against Leishmania LiP2a and LiP2b proteins and that the same response is induced in BALB/c mice when the parasite P proteins are immunized as recombinant molecules without adjuvant. The genetic immunization of BALB/c mice with eukaryotic expression plasmids coding for these proteins was unable to redirect the Th2-like response induced by these antigens, and only the co-administration of the recombinant P proteins with CpG oligodeoxynucleotides (CpG ODN) promoted a mixed Th1/Th2 immune response. According to the preponderance of a Th2 or mixed Th1/Th2 responses elicited by the different regimens of immunization tested, no evidence of protection was observed in mice after challenge with L. major. Although alterations of the clinical outcome were not detected in mice presensitized with the P proteins, the enhanced IgG1 and interleukin (IL)-4 response against total Leishmania antigens in these mice may indicate an exacerbation of the disease.     

新型CpG ODN增强乙肝疫苗诱导IgG2a类抗体产生的实验研究

目的：寻找能增强乙肝疫苗刺激IgG2a类抗体产生，使机体处于Th1样免疫环境的新型乙肝疫苗佐剂。方法：选用自行设计的A、B、C型CpGODN，并以发表的A、B型CpGODN作为阳性对照，与重组乙肝疫苗混合后于第0．4周免疫BALB／C小鼠，用ELISA法检测免疫小鼠血清中HBsAb水平及种类。结果：各型CpGODN都能增强乙肝疫苗刺激HBsAb的产生水平，CpGODN＋乙肝疫苗免疫的小鼠血清中HBsAb类型为IgG2a〉〉IgG1，而单独应用商品化重组乙型肝炎疫苗的小鼠血清中HBsAb类型为IgG1〉〉IgG2a。结论：各型CpGODN对重组乙型肝炎疫苗[含AI（OH）3佐剂]均具有增效作用，而且可以诱导机体产生倾向于Th1途径的免疫应答反应。     

CpG immuno-stimulatory motifs enhance humoral immune responses against hepatitis C virus core protein after DNA-based immunization

Summary.  Chronic HCV infection is associated with a high morbidity and mortality rate, and currently a prophylactic or therapeutic vaccine is not available. DNA-based immunization is a powerful method to generate cellular and humoral immune responses. However, DNA immunization against HCV core results only in a weak humoral immune response demonstrated in several studies. Therefore, co-immunization with a novel adjuvant may enhance such potentially important immune responses. We examined whether unmethylated CpG motifs in the form of oligodeoxynucleotides (ODN) or E. coli DNA can act as adjuvants for a DNA vaccination approach, since CpG motifs have been shown to stimulate the innate immune system as well as B and T cell immune reactivity. The present study demonstrates that CpG motifs enhance in vivo antibody levels after DNA immunization against HCV core. However, despite some in vitro activity of CpG motifs, no enhancement of T cell responses in vivo was observed after immunization with HCV plasmid DNA and CpG motifs in mice. Our results suggest that co-immunization with CpG-ODN may strengthen humoral immune responses but show no potential effect as an adjuvant to induce cellular immunity against HCV core. Received July 24, 2002; accepted October 9, 2002     

Immunogenicity and safety of liposome-vaccine encapsulating hepatitis B surface antigen and phosphodiester CpG oligodeoxynucleotides

CpG oligodeoxynucleotides (CpG ODN) as adjuvant have been extensively studied in recent years. Phosphodiester CpG ODN (PO CpG ODN) can perfectly mimic bacterial DNA in enhancing immune response but are vulnerable to nucleases in vivo . This study aimed to evaluate the immunostimulatory potential and safety of phosphodiester CpG ODN encapsulated in nonphospholipid liposomes. BALB/c mice were immunized intramuscularly with different formulations of liposomes,CpG ODN and hepatitis B surface antigen (HBsAg). The results demonstrated that the encapsulated PO CpG ODN were protected against rapid degradation in vivo and retained their adjuvant activity. PO CpG ODN encapsulated with HBsAg in liposomes induced strong Th1-biased or Th1/Th2 mixed humoral immune response in mice with the magnitude similar to their phosphothioate equivalent in the same formulation. High IFN-gamma production induced by this formulation confirmed the generation of strong cellular immune response. Additionally, co-delivery of HBsAg and PO CpG ODN improved the immune response over that obtained with separate delivery. Safety experiment showed that liposome-encapsulaed PO CpG ODN and HBsAg caused mild systemic and moderate local adverse reaction. In conclusion, our data shows that PO CpG ODN encapsulated in liposomes fully exhibit their Th1-type adjuvant activity and act as a potential adjuvant for vaccines.     

Plasmid DNA vaccines are effective in the absence of IFNgamma.

Intramuscular injection of bacterially derived plasmid DNA results in the development of both humoral and cellular immune responses against plasmid-encoded antigens. Immunostimulatory CpG sequences within bacterial DNA are thought to enhance this process by stimulating the secretion of proinflammatory cytokines such as interferon gamma (IFNgamma) by cells of the innate immune system. Although IFNgamma induction by CpG elements within plasmid DNA has been documented in vitro and more recently in vivo, and coimmunization with plasmids expressing IFNgamma has been shown to enhance DNA-immunization-induced immune responses, it is unclear if IFNgamma is necessary for successful DNA immunization. To address this issue, we compared humoral and cellular immune responses in wild-type and IFNgamma-deficient mice vaccinated with a plasmid (pCMVNP) expressing the nucleoprotein gene from the arenavirus lymphocytic choriomeningitis virus (LCMV). IFNgamma-positive (BALB/c) and IFNgamma-negative (GKO) mice responded to DNA vaccination by the development of antigen-specific CD8(+) T cells, which were detectable directly ex vivo by intracellular cytokine staining and comprised 0.7-2.5% of all CD8(+) T cells in the vaccine. DNA vaccines also induced virus-specific cytotoxic T lymphocytes (CTL), even in the absence of IFNgamma. DNA vaccination of both mouse strains also was associated with a significant reduction in viral titers after LCMV challenge, indicating that, at least in the presence of other immune effector mechanisms, IFNgamma is not required for induction of protective anti-viral immunity by DNA immunization. No quantitative differences were observed in antiviral IgG levels among GKO and BALB/c vaccinees, although GKO mice did exhibit a significant reduction of the IgG2a:IgG1 ratio, in agreement with the previously documented requirement for IFNgamma in isotype switching to IgG2a. Immunized BALB/c mice produced similar levels of both IgG1 and IgG2a, indicating a mixed Th1/Th2 response to intramuscular immunization with pCMVNP. These results show that IFNgamma induction by bacterially derived plasmid DNA does not contribute to the magnitude of the antibody response and is not required for the induction or short-term maintenance of DNA-induced CTL. However, IFNgamma is necessary for the development of IgG2a antibodies that may be crucial for protection against some pathogens.     

Interleukin-12- and gamma interferon-dependent protection against malaria conferred by CpG oligodeoxynucleotide in mice

Unmethylated CpG dinucleotides in bacterial DNA or synthetic oligodeoxynucleotides (ODNs) cause B-cell proliferation and immunoglobulin secretion, monocyte cytokine secretion, and activation of natural killer (NK) cell lytic activity and gamma interferon (IFN-gamma) secretion in vivo and in vitro. The potent Th1-like immune activation by CpG ODNs suggests a possible utility for enhancing innate immunity against infectious pathogens. We therefore investigated whether the innate immune response could protect against malaria. Treatment of mice with CpG ODN 1826 (TCCATGACGTTCCTGACGTT, with the CpG dinucleotides underlined) or 1585 (ggGGTCAACGTTGAgggggG, with g representing diester linkages and phosphorothioate linkages being to the right of lowercase letters) in the absence of antigen 1 to 2 days prior to challenge with Plasmodium yoelii sporozoites conferred sterile protection against infection. A higher level of protection was consistently induced by CpG ODN 1826 compared with CpG ODN 1585. The protective effects of both CpG ODNs were dependent on interleukin-12, as well as IFN-gamma. Moreover, CD8+ T cells (but not CD4+ T cells), NK cells, and nitric oxide were implicated in the CpG ODN 1585-induced protection. These data establish that the protective mechanism induced by administration of CpG ODN 1585 in the absence of parasite antigen is similar in nature to the mechanism induced by immunization with radiation-attenuated P. yoelii sporozoites or with plasmid DNA encoding preerythrocytic-stage P. yoelii antigens. We were unable to confirm whether CD8+ T cells, NK cells, or nitric oxide were required for the CpG ODN 1826-induced protection, but this may reflect differences in the potency of the ODNs rather than a real difference in the mechanism of action of the two ODNs. This is the first report that stimulation of the innate immune system by CpG immunostimulatory motifs can confer sterile protection against malaria.     

Various factors (allergen nature,mouse strain,CpG/recombinant protein expressed) influence the immune response elicited by genetic immunization

BACKGROUND: Genetic immunization is a very promising therapeutic approach for allergy treatment. In the present study we investigate the influence of the nature of the allergen, the mouse strain, and the relative amount of CpG to expressed recombinant protein on immune responses using two major peanut allergens, Ara h 1 and Ara h 4. METHODS: The cDNA of Ara h 1 and of an isoform of Ara h 4 were cloned and inserted in pcDNA3. Antigen specific IgG1, IgG2a and IgE were followed after genetic immunization with 100 microg of these clones in mouse strain SKH-Hr1 or BALB/c and with 1 microg of the clones+99 blank plasmid in SKH-Hr1. RESULTS: Genetic immunization in SKH-Hr1 with Ara h 1 elicited a classical Th1 type response, but Ara h 4 elicited a mixed Th1/Th2 response with high IgG1 and even IgE in some mice. In BALB/c both plasmids produced a high IgG1 level. Decreasing the amount of plasmid injected did not change the immune response profile. However, increasing the amount of CpG administered relative to the recombinant Ara h 4 protein expressed reversed the Th1/Th2 response pattern in SKH-Hr1 mice. CONCLUSIONS: Immune responses after genetic immunization are strongly influenced by the nature of the allergen, the mouse strain, and the ratio of CpG to recombinant protein expressed.     

Adjuvant effects of bacillus Calmette-Guerin DNA or CpG-oligonucleotide in the immune response to Taenia solium cysticercosis vaccine in porcine

The immune stimulation properties of CpG-oligonucleotides (CpG-ODN) containing a central unmethylated CpG motif could be useful for vaccination against parasite infection. However, the high cost of synthetic CpG-ODN has limited its use in veterinary vaccines. In this study, we investigated whether genomic DNA derived from Mycobacterium bovis bacillus Calmette-Guerin (BCG-DNA) could be used as an effective adjuvant to enhance the immunogenicity and the protective capacity of recombinant cC1 antigen (rcC1) against pig cysticercosis. Pigs were vaccinated with rcC1 plus CpG-containing DNA adjuvants (BCG-DNA or CpG-ODN) or rcC1 alone. Immunization with rcC1 alone induced a Th1-biased response, whereas coadministration of rcC1 with BCG-DNA or CpG-ODN increased levels of IgG2, IFN-gamma, percentage of CD8+ and specific proliferation of peripheral blood mononuclear cells. Four weeks after the last immunization, pigs were infected with Taenia solium eggs. A high level of protection (81%) was induced by rcC1 immunization that was not significantly increased by the CpG-containing DNA. These data indicate that coadministration of rcC1 plus BCG-DNA or CpG-ODN significantly enhanced Th1 response but did not improve the level of the protection induced.     

GM-CSF对抗原化抗体基因免疫TH细胞应答的调节作用

目的研究GM-CSF(粒-单核巨噬细胞集落刺激因子)与抗原化抗体联合基因免疫时,GM-CSF对TH细胞应答的调节作用。方法在编码免疫球蛋白重链的质粒中分别克隆黏蛋白1(MUC1)中特异性PDTRP抗原表位和GM-CSF编码基因,构建含PDTRP和GM-CSF编码基因的抗原化抗体表达重组体。经脾免疫和肌肉加强的方式免疫BALB／c小鼠。采用ELISA方法检测小鼠血清中特异性抗体的水平及其亚类并动态观察;RT-PCR方法检测TH细胞分化中细胞因子和转录因子的表达水平。结果抗原化抗体基因免疫能诱导机体产生免疫应答。GM-CSF增强抗原化抗体基因免疫诱生的抗PDTRP特异性IgG抗体水平并且伴随IgG1／IgG2a显著性升高,同时可增强淋巴细胞TH2型细胞因子及转录因子(IL-4、GATA-3)mRNA的表达水平。结论GM-CSF在增强抗原化抗体基因免疫诱导的免疫应答的同时使得免疫应答向TH2方向偏移。     

The immunobiology and clinical potential of immunostimulatory CpG oligodeoxynucleotides

Over 100 years ago, Coley first explored the use of bacterial products as immunostimulatory therapy for nonbacterial disease. It is now clear that bacterial DNA, and synthetic oligodeoxynucleotides containing specific motifs centered on a CpG dinucleotide (CpG ODN), are potent immunostimulatory agents. The molecular mechanisms responsible for the immunostimulatory effects of CpG ODN have yet to be elucidated fully, although it is clear that CpG ODN act rapidly on a variety of cell types. This includes activation of B cells, natural killer cells, and antigen-presenting cells including monocytes, macrophages, and dendritic cells. These effects have led to evaluation of CpG ODN as immune adjuvants in immunization where they have been shown in animal models to enhance the development of a TH1-type immune response. Preliminary results from clinical trials using CpG ODN as an immune adjuvant are promising. Preclinical studies suggest CpG ODN can also enhance innate immunity against a variety of infections, synergize with monoclonal antibody to enhance antibody-dependent cellular cytotoxicity, and alter the Th1/Th2 balance as a possible treatment for allergic diseases and asthma. Clinical evaluation has recently begun to determine whether promising preclinical results with CpG ODN can be translated into effective and tolerable clinical treatment approaches.     

The adjuvant effect of CpG oligodeoxynucleotide linked to the non-toxic B subunit of cholera toxin for induction of immunity against H. pylori in mice

The present study was carried out to test the immunostimulatory and adjuvant effects of the non-toxic B subunit of cholera toxin (CTB), CpG oligodeoxynucleotide (ODN) and CpG ODN linked to CTB (CTB–CpG) for generation of immunity against H. pylori in mice. Herein, we showed that CTB–CpG induces more potent proinflammatory cytokine and chemokine responses in the cervical and the mesenteric lymph nodes (CLN and MLN, respectively) cells in vitro compared with those of CTB and CpG ODN. The adjuvant effects of these agents were examined following intranasal immunization of C57Bl/6 mice with H. pylori lysate in combination with CpG ODN, CTB or CTB–CpG. All three immunization regimes resulted in high H. pylori -specific IgG antibody responses; however, only the CTB–CpG and, to some extent, the CpG ODN immunized mice mounted a sustainable IgG2c antibody response. Importantly, mice immunized with H. pylori antigen and CTB–CpG or CpG ODN, but not CTB, developed strong H. pylori -specific proliferative and IFN-γ responses in their MLN CD4⁺ T cells upon recall antigen stimulation in vitro . These mice also had significantly lower bacterial load compared with the control-infected mice. Furthermore, the CTB–CpG and the CpG ODN immunized mice developed increased specific IgA antibody responses in their gastrointestinal tracts following H. pylori challenge. These results imply that CTB–CpG and CpG ODN, but not CTB, could serve as nasal adjuvants for induction of a H. pylori -specific Th1 type immunity in MLN and also a specific mucosal IgA antibody response in the gastrointestinal tract upon H. pylori challenge.     

Co-administration of porcine-specific CpG oligodeoxynucleotide enhances the immune responses to pseudorabies attenuated virus vaccine in newborn piglets in vivo

Oligonucleotides containing CpG motifs (CpG ODN) are strong adjuvants for humoral and cellular immune responses in mice, but data on immune responses in piglets are scarce. In this report, porcine-specific CpG ODN were used as immunoadjuvants to enhance the immune responses of the newborn piglets to Pseudorabies attenuated virus (PRV) vaccine. The titres of specific antibodies and serum IgG1/IgG2 ratio to PRV vaccine, the proliferation of peripheral blood mononuclear cells (PBMCs), IL-4 and interferon-gamma(IFN-gamma) in piglets serum were examined to identify the immune response of the newborn piglets. The results showed that piglets immunized with PRV vaccine and CpG ODN presented high titers of PRV-specific antibodies and IgG2 isotype, a Th1-dominated (IFN-gamma) cytokine profile, together with inducing higher proliferation of PBMCs. All these data indicate that CpG ODN are potential effective adjuvants for the PRV vaccine in newborn piglets.     

Mucosal immunity induced by pneumococcal glycoconjugate

Host defenses against Streptococcus pneumoniae involve opsonophagocytosis mediated by antibodies and complement. Because the pneumococcus is a respiratory pathogen, mucosal immunity may play an important role in the defense against infection. The mechanism for protection in mucosal immunity consists of induction of immunity by the activation of lymphocytes within the mucosal-associated lymphoid tissues, transport of antigen-specific B and T cells from inductive sites through bloodstream and distribute to distant mucosal effector sites. Secretory IgA is primarily involved in protection of mucosal surfaces. Mucosal immunization is an effective way of inducing immune responses at mucosal surfaces. Several mucosal vaccines are in various stages of development. A number of mucosal adjuvants have been proposed. CpG oligodeoxynucleotide (ODN) has been shown to be an effective mucosal adjuvant for various antigens. Mucosal immunity induced by intranasal immunization was studied with a pneumococcal glycoconjugate, using CpG ODN as adjuvant. Mice immunized with type 9V polysaccharide (PS) conjugated to inactivated pneumolysin (Ply) plus CpG produced high levels of 9V PS IgG and IgA antibodies compared to the group that received the conjugate alone. High levels of subclasses of IgGI, IgG2 and IgG3 antibodies were also observed in sera of mice immunized with 9V PS-Ply plus CpG. In addition, high IgG and IgA antibody responses were observed in sera of young mice immunized with 9V PS-Ply plus CpG or the conjugate plus non-CpG compared with the group received the conjugate alone. These results reveal that mucosal immunization with pneumococcal glycoconjugate using CpG as adjuvant can confer protective immunity against pneumococcal infection.     

The effect of combined IL10 siRNA and CpG ODN as pathogen-mimicking microparticles on Th1/Th2 cytokine balance in dendritic cells and protective immunity against B cell lymphoma

Success of an immunotherapy for cancer often depends on the critical balance of T helper 1 (Th1) and T helper 2 (Th2) responses driven by antigen presenting cells, specifically dendritic cells (DCs). Th1-driven cytotoxic T cell (CTL) responses are key to eliminating tumor cells. It is well established that CpG oligonucleotides (ODN), a widely studied Toll-like receptor 9 (TLR9) agonist, used to enhance Th1 response, also induces high levels of the anti-inflammatory, Th2-promoting cytokine IL10, which could dampen the resulting Th1 response. Biomaterials-based immunomodulatory strategies that can reduce IL10 production while maintaining IL12 levels during CpG delivery could further enhance the Th1/Th2 cytokine balance and improve anti-tumor immune response. Here we report that dual-delivery of IL10-silencing siRNA along with CpG ODN to the same DCs using pathogen-mimicking microparticles (PMPs), significantly enhances their Th1/Th2 cytokine ratio through concurrent inhibition of CpG-induced IL10 production. Co-delivery of poly(I:C), a TLR3 agonist had only minor effects on IL10 levels. Further, simultaneous immunotherapy with CpG ODN and IL10 siRNA enhanced immune protection of an idiotype DNA vaccine in a prophylactic murine model of B cell lymphoma whereas co-delivery of poly(I:C) and CpG did not enhance protection. These results suggest that PMPs can be used to precisely modulate TLR ligand-mediated immune-stimulation in DCs, through co-delivery of cytokine-silencing siRNAs and thereby boost antitumor immunity.     

Long-lasting protective immune response to the 19-kilodalton carboxy-terminal fragment of Plasmodium yoelii merozoite surface protein 1 in mice

Merozoite surface protein 1 (MSP1) is the major protein on the surface of the plasmodial merozoite, and its carboxy terminus, the 19-kDa fragment (MSP1(19)), is highly conserved and effective in induction of a protective immune response against malaria parasite infection in mice and monkeys. However, the duration of the immune response has not been elucidated. As such, we immunized BALB/c mice with a standard four-dose injection of recombinant Plasmodium yoelii MSP1(19) formulated with Montanide ISA51 and CpG oligodeoxynucleotide (ODN) and monitored the MSP1(19)-specific antibody levels for up to 12 months. The antibody titers persisted constantly over the period of time without significant waning, in contrast to the antibody levels induced by immunization with Freund's adjuvant, where the antibody levels gradually declined to significantly lower levels 12 months after immunization. Investigation of immunoglobulin G (IgG) subclass longevity revealed that only the IgG1 antibody level (Th2 type-driven response) decreased significantly by 6 months, while the IgG2a antibody level (Th1 type-driven response) did not change over the 12 months after immunization, but the boosting effect was seen in the IgG1 antibody responses but not in the IgG2a antibody responses. After challenge infection, all immunized mice survived with negligibly patent parasitemia. These findings suggest that protective immune responses to MSP1(19) following immunization using oil-based Montanide ISA51 and CpG ODN as an adjuvant are very long-lasting and encourage clinical trials for malaria vaccine development.     

Immunization against hepatitis B virus by mucosal administration of antigen-antibody complexes

Antigen-antibody complexes have been shown to enhance immune responses against several antigens given by parenteral immunization. Herein, we have evaluated the potential of administering such immunostimulatory complexes by a mucosal route. Hepatitis B surface antigen (HBsAg) complexed with antibodies against HBsAg (anti-HBs) (HBsAg/Ab) was administered to BALB/c mice by intranasal inhalation. HBsAg by itself did not induce immune responses, whereas with HBsAg/Ab complexes, both systemic and mucosal immune responses were observed and these could be modulated by adjuvants. With HBsAg/Ab (1 or 10 microg), anti-HBs antibodies induced were predominantly of the IgG1 isotype (Th2-like). In contrast, anti-HBs induced by HBsAg/Ab plus cholera toxin (CT) or oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs (CpG) (1 microg each) were predominantly IgG2a (Th1-like). Results from this study indicate that HBsAg/Ab complexes can induce strong humoral immune responses when delivered by a noninvasive route, whether used alone or in combination with other mucosal adjuvants.     

CpG motifs as possible adjuvants for the treatment of allergic diseases

DNA containing unmethylated CpG motifs and synthetic oligodeoxynucleotides derived thereof (CpG ODN) have intensively been investigated for their immunostimulatory properties in the recent past. CpG ODN were shown to induce strong Th1 immune responses in mammals. The downregulation of the antigen-driven Th2 response of type I allergies represents one important therapeutic goal of specific immunotherapy (SIT). Hence, CpG ODN represent promising substances which support the modification of the pathogenic Th2 immune profile toward a Th1 profile when used as adjuvants for SIT. This article discusses how the use of CpG ODN in immunotherapeutics could improve the treatment of type I allergy.