Gut Microbiota and Bacterial DNA Suppress Autoimmunity by Stimulating Regulatory B Cells in a Murine Model of Lupus

Autoimmune diseases, such as systemic lupus erythematosus, are characterized by excessive inflammation in response to self-antigens. Loss of appropriate immunoregulatory mechanisms contribute to disease exacerbation. We previously showed the suppressive effect of vancomycin treatment during the "active-disease" stage of lupus. In this study, we sought to understand the effect of the same treatment given before disease onset. To develop a model in which to test the regulatory role of the gut microbiota in modifying autoimmunity, we treated lupus-prone mice with vancomycin in the period before disease development (3-8 weeks of age). We found that administration of vancomycin to female MRL/lpr mice early, only during the pre-disease period but not from 3 to 15 weeks of age, led to disease exacerbation. Early vancomycin administration also reduced splenic regulatory B (Breg) cell numbers, as well as reduced circulating IL-10 and IL-35 in 8-week old mice. Further, we found that during the pre-disease period, administration of activated IL-10 producing Breg cells to mice treated with vancomycin suppressed lupus initiation, and that bacterial DNA from the gut microbiota was an inducer of Breg function. Oral gavage of bacterial DNA to mice treated with vancomycin increased Breg cells in the spleen and mesenteric lymph node at 8 weeks of age and reduced autoimmune disease severity at 15 weeks. This work suggests that a form of oral tolerance induced by bacterial DNA-mediated expansion of Breg cells suppress disease onset in the autoimmune-prone MRL/lpr mouse model. Future studies are warranted to further define the mechanism behind bacterial DNA promoting Breg cells.

Structures and Mechanisms in the cGAS-STING Innate Immunity Pathway

Besides its role as the blueprint of life, DNA can also alert the cell to the presence of microbial pathogens as well as damaged or malignant cells. A major sensor of DNA that triggers the innate immune response is cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) (cGAMP) synthase (cGAS), which produces the second messenger cGAMP. cGAMP activates stimulator of interferon genes (STING), which activates a signaling cascade leading to the production of type I interferons and other immune mediators. Recent research has demonstrated an expanding role of the cGAS-cGAMP-STING pathway in many physiological and pathological processes, including host defense against microbial infections, anti-tumor immunity, cellular senescence, autophagy, and autoimmune and inflammatory diseases. Biochemical and structural studies have elucidated the mechanism of signal transduction in the cGAS pathway at the atomic resolution. This review focuses on the structural and mechanistic insights into the roles of cGAS and STING in immunity and diseases revealed by these recent studies.

CXCL4 assembles DNA into liquid crystalline complexes to amplify TLR9-mediated interferon-α production in systemic sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by fibrosis and vasculopathy. CXCL4 represents an early serum biomarker of severe SSc and likely contributes to inflammation via chemokine signaling pathways, but the exact role of CXCL4 in SSc pathogenesis is unclear. Here, we elucidate an unanticipated mechanism for CXCL4-mediated immune amplification in SSc, in which CXCL4 organizes "self" and microbial DNA into liquid crystalline immune complexes that amplify TLR9-mediated plasmacytoid dendritic cell (pDC)-hyperactivation and interferon-α production. Surprisingly, this activity does not require CXCR3, the CXCL4 receptor. Importantly, we find that CXCL4-DNA complexes are present in vivo and correlate with type I interferon (IFN-I) in SSc blood, and that CXCL4-positive skin pDCs coexpress IFN-I-related genes. Thus, we establish a direct link between CXCL4 overexpression and the IFN-I-gene signature in SSc and outline a paradigm in which chemokines can drastically modulate innate immune receptors without being direct agonists.

Clustered intergenic region sequences as predictors of factor H Binding Protein expression patterns and for assessing Neisseria meningitidis strain coverage by meningococcal vaccines

Factor H binding protein (fHbp) is a major protective antigen in 4C-MenB (Bexsero®) and Trumenba®, two serogroup B meningococcal vaccines, wherein expression level is a determinant of protection. Examination of promoter-containing intergenic region (IGR) sequences indicated that nine fHbp IGR alleles covered 92% of 1,032 invasive meningococcal strains with variant 1 fHbp alleles. Relative expression values for fHbp were determined for 79 meningococcal isolates covering ten IGR alleles by quantitative reverse transcriptase polymerase chain reaction (qRT PCR). Derivation of expression clusters of IGR sequences by linear regression identified five expression clusters with five nucleotides and one insertion showing statistically associations with differences in expression level. Sequence analysis of 273 isolates examined by the Meningococcal Antigen Typing Scheme, a sandwich ELISA, found that coverage depended on the IGR expression cluster and vaccine peptide homology combination. Specific fHbp peptide-IGR expression cluster combinations were designated as 'at risk' for coverage by 4C-MenB and were detected in multiple invasive meningococcal disease cases confirmed by PCR alone and occurring in partially-vaccinated infants. We conclude that sequence-based analysis of IGR sequences is informative for assessing protein expression and has utility for culture-independent assessments of strain coverage by protein-based vaccines.

Composition and immuno-stimulatory properties of extracellular DNA from mouse gut flora

AIM

To demonstrate that specific bacteria might release bacterial extracellular DNA (eDNA) to exert immunomodulatory functions in the mouse small intestine.

METHODS

Extracellular DNA was extracted using phosphate buffered saline with 0.5 mmol/L dithiothreitol combined with two phenol extractions. TOTO-1 iodide, a cell-impermeant and high-affinity nucleic acid stain, was used to confirm the existence of eDNA in the mucus layers of the small intestine and colon in healthy Male C57BL/6 mice. Composition difference of eDNA and intracellular DNA (iDNA) of the small intestinal mucus was studied by Illumina sequencing and terminal restriction fragment length polymorphism (T-RFLP). Stimulation of cytokine production by eDNA was studied in RAW264.7 cells in vitro.

RESULTS

TOTO-1 iodide staining confirmed existence of eDNA in loose mucus layer of the mouse colon and thin surface mucus layer of the small intestine. Illumina sequencing analysis and T-RFLP revealed that the composition of the eDNA in the small intestinal mucus was significantly different from that of the iDNA of the small intestinal mucus bacteria. Illumina Miseq sequencing showed that the eDNA sequences came mainly from Gram-negative bacteria of Bacteroidales S24-7. By contrast, predominant bacteria of the small intestinal flora comprised Gram-positive bacteria. Both eDNA and iDNA were added to native or lipopolysaccharide-stimulated Raw267.4 macrophages, respectively. The eDNA induced significantly lower tumor necrosis factor-α/interleukin-10 (IL-10) and IL-6/IL-10 ratios than iDNA, suggesting the predominance for maintaining immune homeostasis of the gut.

CONCLUSION

Our results indicated that degraded bacterial genomic DNA was mainly released by Gram-negative bacteria, especially Bacteroidales-S24-7 and Stenotrophomonas genus in gut mucus of mice. They decreased pro-inflammatory activity compared to total gut flora genomic DNA.

DCs facilitate B cell responses against microbial DNA via DC-SIGN

Microbial DNA is highly immunostimulatory and is sensed by endosomal pattern recognition receptors after release from internalized microbes. It is unclear how extracellular DNA released from dead microbes is delivered to endosomal PRRs to induce immune responses. Here we have investigated the ability of DCs to bind and internalize extracellular E.coli DNA as well as synthetic DNA. DCs internalized E.coli and synthetic DNA, which was dependent on the C-type lectin receptor DC-SIGN. Notably, endosomal uptake of DNA by DCs enhanced TLR9-dependent responses of B cells against DNA. Hence, we have identified DC-SIGN as a cell surface receptor for DNA that facilitates immune responses directed against DNA.

Perinatal Bacterial Exposure Contributes to IL-13 Aeroallergen Response

There is a high prevalence of aeroallergen sensitivity in asthmatic populations, and seroreactivity to aeroallergens early in infancy is associated with increased risk of developing asthma later in life. In addition to allergen sensitivity, asthma development has been associated with differential microbial exposure and infection in early life. We have previously shown that cord blood mononuclear cells respond to common aeroallergens (i.e., house dust mite [Der f1] and cockroach [Bla g2]) as assayed by lymphoproliferation and cytokine (IL-13 and IFN-γ) production. We hypothesized that there is a relationship between perinatal microbial exposure and response to specific aeroallergens. To test this hypothesis, we isolated DNA from cord blood serum samples with known lymphoproliferative and cytokine responses to Bla g2 and Der f1. Bacterial 16S ribosomal DNA amplicon libraries were generated and analyzed using high throughput sequencing of cord blood serum samples. In our analysis, we identified major compositional differences, including diversity and abundance of specific taxa, between groups whose IL-13 response to Der f1 and Bla g2 differed. We demonstrate a strong association between the ratio of Acinetobacter to Proteobacteria and IL-13 production and the probability of IL-13 production after allergen exposure. IL-13 concentrations in serum were also significantly correlated with the diversity of bacterial DNA. Together, these results underscore the relationship between immune responses to allergens and bacterial exposure during perinatal development.

Toll-like receptor polymorphisms compromise the inflammatory response against bacterial antigen translocation in cirrhosis

Bacterial translocation is associated with clinically relevant complications in cirrhosis. We evaluated the effect of toll-like receptor polymorphisms in the soluble response against these episodes. Consecutive patients with cirrhosis and ascitic fluid were distributed by TLR2 rs4696480, TLR4 rs4986790, and TLR9 rs187084 single-nucleotide polymorphisms. Lipoteichoic acid, lipopolyssaccharide, bacterial-DNA, pro-inflammatory cytokines and nitric oxide levels were quantified in serum samples. In vitro response against specific ligands in variant TLR genotypes was evaluated. One hundred and fourteen patients were included. Variant TLR-2, TLR-4 and TLR-9 SNP genotypes were associated with significantly increased serum levels of LTA, LPS and bacterial-DNA. TNF-α, IL-6 and nitric oxide serum levels were significantly decreased in all variant TLR genotyped patients. Cytokine levels were significantly less upregulated in response to specific TLR-ligands in patients with all variant vs wildtype TLR genotypes. Although in vitro gene expression levels of all wildtype and variant TLRs were similar, MyD88 and NFkB were significantly downregulated in cells from TLR-variant genotyped patients in response to their ligands. Variant TLR genotypes are associated with an increased circulating antigen burden and a decreased proinflammatory response in cirrhosis. This immunodeficiency may facilitate bacteria-related complications in cirrhosis and enhance TLR targeting for its management.

Bacterial amyloid curli acts as a carrier for DNA to elicit an autoimmune response via TLR2 and TLR9

Bacterial biofilms are associated with numerous human infections. The predominant protein expressed in enteric biofilms is the amyloid curli, which forms highly immunogenic complexes with DNA. Infection with curli-expressing bacteria or systemic exposure to purified curli-DNA complexes triggers autoimmunity via the generation of type I interferons (IFNs) and anti-double-stranded DNA antibodies. Here, we show that DNA complexed with amyloid curli powerfully stimulates Toll-like receptor 9 (TLR9) through a two-step mechanism. First, the cross beta-sheet structure of curli is bound by cell-surface Toll-like receptor 2 (TLR2), enabling internalization of the complex into endosomes. After internalization, the curli-DNA immune complex binds strongly to endosomal TLR9, inducing production of type I IFNs. Analysis of wild-type and TLR2-deficient macrophages showed that TLR2 is the major receptor that drives the internalization of curli-DNA complexes. Suppression of TLR2 internalization via endocytosis inhibitors led to a significant decrease in Ifnβ expression. Confocal microscopy analysis confirmed that the TLR2-bound curli was required for shuttling of DNA to endosomal TLR9. Structural analysis using small-angle X-ray scattering revealed that incorporation of DNA into curli fibrils resulted in the formation of ordered curli-DNA immune complexes. Curli organizes parallel, double-stranded DNA rods at an inter-DNA spacing that matches up well with the steric size of TLR9. We also found that production of anti-double-stranded DNA autoantibodies in response to curli-DNA was attenuated in TLR2- and TLR9-deficient mice and in mice deficient in both TLR2 and TLR9 compared to wild-type mice, suggesting that both innate immune receptors are critical for shaping the autoimmune adaptive immune response. We also detected significantly lower levels of interferon-stimulated gene expression in response to purified curli-DNA in TLR2 and TLR9 deficient mice compared to wild-type mice, confirming that TLR2 and TLR9 are required for the induction of type I IFNs. Finally, we showed that curli-DNA complexes, but not cellulose, were responsible elicitation of the immune responses to bacterial biofilms. This study defines the series of events that lead to the severe pro-autoimmune effects of amyloid-expressing bacteria and suggest a mechanism by which amyloid curli acts as a carrier to break immune tolerance to DNA, leading to the activation of TLR9, production of type I IFNs, and subsequent production of autoantibodies.

Human β-defensin 3 increases the TLR9-dependent response to bacterial DNA

Human β-defensin 3 (hBD3) is a cationic antimicrobial peptide with potent bactericidal activity in vitro. HBD3 is produced in response to pathogen challenge and can modulate immune responses. The amplified recognition of self-DNA by human plasmacytoid dendritic cells has been previously reported, but we show here that hBD3 preferentially enhances the response to bacterial DNA in mouse Flt-3 induced dendritic cells (FLDCs) and in human peripheral blood mononuclear cells. We show the effect is mediated through TLR9 and although hBD3 significantly increases the cellular uptake of both E. coli and self-DNA in mouse FLDCs, only the response to bacterial DNA is enhanced. Liposome transfection also increases uptake of bacterial DNA and amplifies the TLR9-dependent response. In contrast to hBD3, lipofection of self-DNA enhances inflammatory signaling, but the response is predominantly TLR9-independent. Together, these data show that hBD3 has a role in the innate immune-mediated response to pathogen DNA, increasing inflammatory signaling and promoting activation of the adaptive immune system via antigen presenting cells including dendritic cells. Therefore, our data identify an additional immunomodulatory role for this copy-number variable defensin, of relevance to host defence against infection and indicate a potential for the inclusion of HBD3 in pathogen DNA-based vaccines.

Bovine milk RNases modulate pro-inflammatory responses induced by nucleic acids in cultured immune and epithelial cells

Activation of innate immune receptors by exogenous substances is crucial for the detection of microbial pathogens and a subsequent inflammatory response. The inflammatory response to microbial lipopolysaccharide via Toll-like receptor 4 (TLR4) is facilitated by soluble accessory proteins, but the role of such proteins in the activation of other pathogen recognition receptors for microbial nucleic acid is not well understood. Here we demonstrate that RNase4 and RNase5 purified from bovine milk bind to Salmonella typhimurium DNA and stimulate pro-inflammatory responses induced by nucleic acid mimetics and S. typhimurium DNA in an established mouse macrophage cell culture model, RAW264.7, as well as in primary bovine mammary epithelial cells. RNase4 and 5 also modulated pro-inflammatory signalling in response to nucleic acids in bovine peripheral blood mononuclear cells, although producing a distinct response. These results support a role for RNase4 and RNase5 in mediating inflammatory signals in both immune and epithelial cells, involving mechanisms that are cell-type specific.

Crosstalk between Cytoplasmic RIG-I and STING Sensing Pathways

Detection of evolutionarily conserved molecules on microbial pathogens by host immune sensors represents the initial trigger of the immune response against infection. Cytosolic receptors sense viral and intracellular bacterial genomes, as well as nucleic acids produced during replication. Once activated, these sensors trigger multiple signaling cascades, converging on the production of type I interferons and proinflammatory cytokines. Although distinct classes of receptors are responsible for the RNA and DNA sensing, the downstream signaling components are physically and functionally interconnected. This review highlights the importance of the crosstalk between retinoic acid inducible gene-I (RIG-I)-mitochondrial antiviral-signaling protein (MAVS) RNA sensing and the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) DNA sensing pathways in potentiating efficient antiviral responses. The potential of cGAS-STING manipulation as a component of cancer immunotherapy is also reviewed.

Rapid diagnosis of Mycoplasma pneumoniae in children with pneumonia by an immuno-chromatographic antigen assay

Mycoplasma pneumoniae is a particularly important pathogen that causes community acquired pneumonia in children. In this study, a rapid test was developed to diagnose M. pneumoniae by using a colloidal gold-based immuno-chromatographic assay which targets a region of the P1 gene. 302 specimens were analyzed by the colloidal gold assay in parallel with real-time PCR. Interestingly, the colloidal gold assay allowed M. pneumoniae identification, with a detection limit of 1 × 10(3) copies/ml. 76 samples were found to be positive in both real-time PCR and the colloidal gold assay; two specimens positive in real-time PCR were negative in the rapid colloidal gold assay. The specificity and sensitivity of the colloidal gold assay were 100% and 97.4%, respectively. These findings indicate that the newly developed immuno-chromatographic antigen assay is a rapid, sensitive and specific method for identifying M. pneumoniae, with potential clinical application in the early diagnosis of Mycoplasma pneumoniae infection.

T(H)17 cells promote microbial killing and innate immune sensing of DNA via interleukin 26

Interleukin 17-producing helper T cells (T(H)17 cells) have a major role in protection against infections and in mediating autoimmune diseases, yet the mechanisms involved are incompletely understood. We found that interleukin 26 (IL-26), a human T(H)17 cell-derived cytokine, is a cationic amphipathic protein that kills extracellular bacteria via membrane-pore formation. Furthermore, T(H)17 cell-derived IL-26 formed complexes with bacterial DNA and self-DNA released by dying bacteria and host cells. The resulting IL-26-DNA complexes triggered the production of type I interferon by plasmacytoid dendritic cells via activation of Toll-like receptor 9, but independently of the IL-26 receptor. These findings provide insights into the potent antimicrobial and proinflammatory function of T(H)17 cells by showing that IL-26 is a natural human antimicrobial that promotes immune sensing of bacterial and host cell death.

Genetic Variation of Bordetella pertussis in Austria

In Austria, vaccination coverage against Bordetella pertussis infections during infancy is estimated at around 90%. Within the last years, however, the number of pertussis cases has increased steadily, not only in children but also in adolescents and adults, indicating both insufficient herd immunity and vaccine coverage. Waning immunity in the host and/or adaptation of the bacterium to the immunised hosts could contribute to the observed re-emergence of pertussis. In this study we therefore addressed the genetic variability in B. pertussis strains from several Austrian cities. Between the years 2002 and 2008, 110 samples were collected from Vienna (n = 32), Linz (n = 63) and Graz (n = 15) by nasopharyngeal swabs. DNA was extracted from the swabs, and bacterial sequence polymorphisms were examined by MLVA (multiple-locus variable number of tandem repeat analysis) (n = 77), by PCR amplification and conventional Sanger sequencing of the polymorphic regions of the prn (pertactin) gene (n = 110), and by amplification refractory mutation system quantitative PCR (ARMS-qPCR) (n = 110) to directly address polymorphisms in the genes encoding two pertussis toxin subunits (ptxA and ptxB), a fimbrial adhesin (fimD), tracheal colonisation factor (tcfA), and the virulence sensor protein (bvgS). Finally, the ptxP promoter region was screened by ARMS-qPCR for the presence of the ptxP3 allele, which has been associated with elevated production of pertussis toxin. The MLVA analysis revealed the highest level of polymorphisms with an absence of MLVA Type 29, which is found outside Austria. Only Prn subtypes Prn1/7, Prn2 and Prn3 were found with a predominance of the non-vaccine type Prn2. The analysis of the ptxA, ptxB, fimD, tcfA and bvgS polymorphisms showed a genotype mixed between the vaccine strain Tohama I and a clinical isolate from 2006 (L517). The major part of the samples (93%) displayed the ptxP3 allele. The consequences for the vaccination strategy are discussed.

Amyloid-DNA Composites of Bacterial Biofilms Stimulate Autoimmunity

Research on the human microbiome has established that commensal and pathogenic bacteria can influence obesity, cancer, and autoimmunity through mechanisms mostly unknown. We found that a component of bacterial biofilms, the amyloid protein curli, irreversibly formed fibers with bacterial DNA during biofilm formation. This interaction accelerated amyloid polymerization and created potent immunogenic complexes that activated immune cells, including dendritic cells, to produce cytokines such as type I interferons, which are pathogenic in systemic lupus erythematosus (SLE). When given systemically, curli-DNA composites triggered immune activation and production of autoantibodies in lupus-prone and wild-type mice. We also found that the infection of lupus-prone mice with curli-producing bacteria triggered higher autoantibody titers compared to curli-deficient bacteria. These data provide a mechanism by which the microbiome and biofilm-producing enteric infections may contribute to the progression of SLE and point to a potential molecular target for treatment of autoimmunity.

[Advances in immunomodulation of microbial unmethylated CpG DNA on animal intestinal tract--a review]

Unmethylated cytosine-guanine (CpG) dinucleotides motifs in bacterial DNA can be recognized by specific Toll-like receptor 9 (TLR9) in intestinal cells. As one of the intestinal immunostimulatory factors, unmethylated CpG DNA can modulate intestinal innate immune responses directly and adaptive immune responses indirectly. There is a great prospect for unmethylated CpG DNA as an immunomodulator in the rapy of intestinal diseases. This article illustrated the basic concepts of unmethylated CpG DNA, the characteristics of TLR9. We also reviewed specific applications of unmethylated CpG DNA as adjuvants in modulating intestinal immune responses. At last, we elaborated the research and application prospects of CpG DNA in the future.

Subgingival microbial communities in Leukocyte Adhesion Deficiency and their relationship with local immunopathology

Leukocyte Adhesion Deficiency I (LAD-I) is a primary immunodeficiency caused by single gene mutations in the CD18 subunit of β2 integrins which result in defective transmigration of neutrophils into the tissues. Affected patients suffer from recurrent life threatening infections and severe oral disease (periodontitis). Microbial communities in the local environment (subgingival plaque) are thought to be the triggers for inflammatory periodontitis, yet little is known regarding the microbial communities associated with LAD-I periodontitis. Here we present the first comprehensive characterization of the subgingival communities in LAD-I, using a 16S rRNA gene-based microarray, and investigate the relationship of this tooth adherent microbiome to the local immunopathology of periodontitis. We show that the LAD subgingival microbiome is distinct from that of health and Localized Aggressive Periodontitits. Select periodontitis-associated species in the LAD microbiome included Parvimonas micra, Porphyromonas endodontalis, Eubacterium brachy and Treponema species. Pseudomonas aeruginosa, a bacterium not typically found in subgingival plaque is detected in LAD-I. We suggest that microbial products from LAD-associated communities may have a role in stimulating the local inflammatory response. We demonstrate that bacterial LPS translocates into the lesions of LAD-periodontitis potentially triggering immunopathology. We also show in in vitro assays with human macrophages and in vivo in animal models that microbial products from LAD-associated subgingival plaque trigger IL-23-related immune responses, which have been shown to dominate in patient lesions. In conclusion, our current study characterizes the subgingival microbial communities in LAD-periodontitis and supports their role as triggers of disease pathogenesis.

Innate immune sensing of nucleic acids from pathogens

The innate immune system is important as the first line of defense to sense invading pathogens. Nucleic acids represent critical pathogen signatures that trigger a host proinflammatory immune response. Much progress has been made in understanding how DNA and RNA trigger host defense countermeasures, however, several aspects of how cytosolic nucleic acids are sensed remain unclear. This special issue reviews how the host innate immune system senses nucleic acids from Brucella abortus, Mycobacterium sp and Legionella pneumophila, viral DNA, the role of STING in DNA sensing and inflammatory diseases and the mechanism of viral RNA recognition by the small interfering RNA pathway in Drosophila melanogaster.

[Chlamydia pneumoniae persistent infection is associated with primary IgA nephropathy]

OBJECTIVE

To explore the correlations between Chlamydia pneumoniae (CP) infection and IgA nephropathy (IgAN).

METHODS

Seventy patients with primary IgAN were enrolled in the study. Seventy serum specimens from healthy blood donors and twelve renal autopsy specimens from accidental death bodies were regarded as control groups. Serum CP IgG and CP IgA antibody titers were detected by indirect immunofluorescence. CP DNA of renal tissue was measured by fluorescent quantitative PCR. Finally, using statistical methods, we analyzed the correlations of CP infection and CP DNA of renal tissue with clinical manifestations and kidney pathological changes of IgAN patients.

RESULTS

The rate of CP persistent infection in IgAN group was higher than that of healthy blood donor group (P<0.01). The rate was not significantly different within the IgAN group, such as among acute infection, previous infection and no infection subgroups (P>0.05). It was higher in the patients with gross proteinuria and/or durative renal insufficiency than in non-gross proteinuria patients (P<0.05). The scores of glomerular patholopical and tubulointerstitial injury of CP persistent infection patients were higher than those of non-persistent infection ones (P<0.05). The renal injury of CP persistent infection patients was more severe than that of non-persistent infection ones. The positive rate of CP DNA in gross proteinuria and/or renal insufficiency patients was higher than that of non-gross proteinuria patients (P<0.05). The scores of glomerular pathological and tubulointerstitial injury of positive CP DNA patients were respectively higher than those of negative CP DNA ones (P<0.05, P<0.01). The renal injury of patients with positive CP DNA was more severe than that of negative CP DNA ones. CP persistent infection was obviously correlated with renal CP DNA (P<0.01).

CONCLUSION

Primary IgAN is associated with CP persistent infection, but not with CP previous infection or CP acute infection.

The effect of polyamines on the binding of anti-DNA antibodies from patients with SLE and normal human subjects

Antibodies to DNA (anti-DNA) are the serological hallmark of systemic lupus erythematosus (SLE). To elucidate specificity further, the effect of polyamines on the binding of anti-DNA antibodies from patients with lupus was tested by ELISA to calf thymus (CT) DNA; we also assessed the binding of plasmas of patients and normal human subjects (NHS) to Micrococcus luteus (MC) DNA. As these studies showed, spermine can dose-dependently inhibit SLE anti-DNA binding to CT DNA and can promote dissociation of preformed immune complexes. With MC DNA as antigen, spermine failed to inhibit the NHS anti-DNA binding. Studies using plasmas adsorbed to a CT DNA cellulose affinity indicated that SLE plasmas are mixtures of anti-DNA that differ in inhibition by spermine and binding to conserved and non-conserved determinants. Together, these studies demonstrate that spermine can influence the binding of anti-DNA autoantibodies and may contribute to the antigenicity of DNA.

A palindromic CpG-containing phosphodiester oligodeoxynucleotide as a mucosal adjuvant stimulates plasmacytoid dendritic cell-mediated T(H)1 immunity

BACKGROUND

CpG oligodeoxynucleotides (ODNs), resembling bacterial DNA, are currently tested in clinical trials as vaccine adjuvants. They have the nuclease-resistant phosphorothioate bond; the immune responses elicited differ according to the CpG ODN sequence and vaccination method. To develop a CpG ODN that can induce plasmacytoid dendritic cell (pDC)-mediated T(H)1 immunity through the mucosa, we constructed phosphodiester G9.1 comprising one palindromic CpG motif with unique polyguanosine-runs that allows degradation similar to naturally occurring bacterial DNA.

METHODS

T(H)1 and T(H)2 immunity activation was evaluated by cytokine production pattern and T-bet/GATA-3 ratio in human peripheral blood mononuclear cells and mouse bone marrow cells. Adjuvanticity was evaluated in mice administered G9.1 with diphtheria toxoid (DT) through nasal vaccination.

RESULTS

G9.1 exhibited stronger IFN-α-inducing activity than A-class CpG ODN2216 and increased T-bet/GATA-3 ratio by enhancing T-bet expression. Nasally administered G9.1 plus DT induced DT-specific mucosal IgA and serum IgG, but not IgE, responses with antitoxin activity in C57BL/6 and BALB/c mice, possibly due to IFN/BAFF production. Induction of T(H)1, but not T(H)2-type Abs depended completely on pDCs, the first in vivo demonstration by CpG ODNs.

CONCLUSIONS

G9.1 is a promising mucosal adjuvant for induction of pDC-mediated T(H)1 immunity.

Activation of an innate immune response in the schistosome-transmitting snail Biomphalaria glabrata by specific bacterial PAMPs

Injection of crude lipopolysaccharide (LPS) from Escherichia coli into the hemocoel of Biomphalaria glabrata stimulates cell proliferation in the amebocyte-producing organ (APO). However, it is not known if mitogenic activity resides in the lipid A or O-polysaccharide component of LPS. Moreover, the possible role of substances that commonly contaminate crude LPS and that are known to stimulate innate immune responses in mammals, e.g., peptidoglycan (PGN), protein, or bacterial DNA, is unclear. Therefore, we tested the effects of the following injected substances on the snail APO: crude LPS, ultrapurified LPS (lacking lipoprotein contamination), two forms of lipid A, (diphosphoryl lipid A and Kdo2-lipid A), O-polysaccharide, Gram negative PGN, both crude and ultrapurified (with and without endotoxin activity, respectively), Gram positive PGN, PGN components Tri-DAP and muramyl dipeptide, and bacterial DNA. Whereas crude LPS, ultrapurified LPS, and crude PGN were mitogenic, ultrapurified PGN was not. Moreover, LPS components, PGN components, and bacterial DNA were inactive. These results suggest that it is the intact LPS molecule which stimulates cell division in the APO.

Toll-like receptor 9 signaling delays neutrophil apoptosis by increasing transcription of Mcl-1

Neutrophils detect bacterial constituents, including bacterial DNA (CpG DNA), which elicits innate immunity and prolongs the functional life span of neutrophils through suppression of apoptosis. Both the anti-apoptotic protein Mcl-1 and activation of NF-κB have been implicated in neutrophil survival, but there is no evidence that these are linked in neutrophils. We hypothesized that CpG DNA could simultaneously activate these pathways. High purity CpG DNA (0.4–3.2 µg/ml) extended the life span of human neutrophils in vitro by delaying apoptosis through altering the rate of Mcl-1 turnover. CpG DNA slightly decreased Mcl-1 protein level in the presence of cyclohexmide and the proteasome inhibitor MG132 had little effect on Mcl-1 expression in CpG DNA-treated neutrophils. In contrast, CpG DNA evoked rapid increases in DNA binding by NF-κB/p65 and Mcl-1 mRNA. NF-κB inhibitors and the telomere-derived TLR9 inhibitory oligonucleotide 5′-TTT AGG GTT AGG GTT AGG G-3′ markedly reduced Mcl-1 protein levels and subsequently abrogated suppression of apoptosis by CpG DNA. Furthermore, CpG DNA attenuated the decreases in Mcl-1 in both cell lysate and nucleus of neutrophils undergoing spontaneous apoptosis and increased Mcl-1 translocation to the mitochondria, leading to preservation of mitochondrial transmembrane potential. These results demonstrate that CpG DNA through toll-like receptor 9 links two survival signaling pathways by delaying apoptosis through induction of NF-κB-mediated Mcl-1 gene transcription and promoting Mcl-1 translocation to the mitochondria.

DNA recognition in immunity and disease

Great progress has been made in understanding how immune cells detect microbial pathogens. An area that has received particular attention is nucleic acid sensing where RNA and DNA sensing machineries have been uncovered. For DNA, TLR9 in endosomes and numerous cytoplasmic DNA binding proteins have been identified. Several of these have been proposed to couple DNA recognition to induction of type I IFNs, pro-inflammatory cytokines and/or caspase-1 activation. Given the ubiquitous expression of many of these DNA binding proteins and the significant potential for endogenous DNA to engage these molecules, it is important that DNA recognition is tightly regulated. A better understanding of DNA recognition pathways can provide new insights into infectious, inflammatory and autoimmune diseases.

In situ forming microparticle implants for delivery of sex steroids in fish: Modulation of the immune response of gilthead seabream by testosterone

Current knowledge on the sensitivity of marine fish to androgenic environmental chemicals is limited, despite the growing interest in the effects of endocrine disrupting chemicals. To study in vivo the effects of testosterone (T) on the fish immune response, we used a microencapsulation implant technique, the in situ forming microparticle system, containing 1 mg T/kg body weight (T-ISM), in adult specimens of gilthead seabream (Sparus aurata L.), a species of great economic interest. We demonstrated that implants themselves (without T) have no significant effect on most of the parameters measured. In T-ISM implanted fish, T serum levels reached supraphysiological concentrations accompanied by a slight increase in 11-ketotestosterone and 17β-estradiol levels 21 days post-implantation (dpi). Liver and head-kidney samples were processed 7 and 21 dpi to assess T-ISM effect on (i) the mRNA expression of genes involved in the metabolism of steroid hormones and in the immune response, and (ii) phagocyte activities. The expression profile of cytokines, chemokines and immune receptors was altered in T-ISM implanted animals that showed an early pro-inflammatory tendency, and then, a mixed pro-/anti-inflammatory activation during longer exposure. Furthermore, the enhancement of phagocytic activity and the production of reactive oxygen species by leukocytes 21 dpi in T-ISM implanted specimens suggest fine modulation of the innate immune response by T. Taken together, these data demonstrate for the first time the feasibility of using ISM implants in an aquatic species, and provide new data on the role played by T on the immune response in fish.

Extracellular M. tuberculosis DNA targets bacteria for autophagy by activating the host DNA-sensing pathway

Eukaryotic cells sterilize the cytosol by using autophagy to route invading bacterial pathogens to the lysosome. During macrophage infection with Mycobacterium tuberculosis, a vacuolar pathogen, exogenous induction of autophagy can limit replication, but the mechanism of autophagy targeting and its role in natural infection remain unclear. Here we show that phagosomal permeabilization mediated by the bacterial ESX-1 secretion system allows cytosolic components of the ubiquitin-mediated autophagy pathway access to phagosomal M. tuberculosis. Recognition of extracelluar bacterial DNA by the STING-dependent cytosolic pathway is required for marking bacteria with ubiquitin, and delivery of bacilli to autophagosomes requires the ubiquitin-autophagy receptors p62 and NDP52 and the DNA-responsive kinase TBK1. Remarkably, mice with monocytes incapable of delivering bacilli to the autophagy pathway are extremely susceptible to infection. Our results reveal an unexpected link between DNA sensing, innate immunity, and autophagy and indicate a major role for this autophagy pathway in resistance to M. tuberculosis infection.

Direct molecular detection and genotyping of Borrelia burgdorferi from whole blood of patients with early Lyme disease

Direct molecular tests in blood for early Lyme disease can be insensitive due to low amount of circulating Borrelia burgdorferi DNA. To address this challenge, we have developed a sensitive strategy to both detect and genotype B. burgdorferi directly from whole blood collected during the initial patient visit. This strategy improved sensitivity by employing 1.25 mL of whole blood, a novel pre-enrichment of the entire specimen extract for Borrelia DNA prior to a multi-locus PCR and electrospray ionization mass spectrometry detection assay. We evaluated the assay on blood collected at the initial presentation from 21 endemic area patients who had both physician-diagnosed erythema migrans (EM) and positive two-tiered serology either at the initial visit or at a follow-up visit after three weeks of antibiotic therapy. Results of this DNA analysis showed detection of B. burgdorferi in 13 of 21 patients (62%). In most cases the new assay also provided the B. burgdorferi genotype. The combined results of our direct detection assay with initial physician visit serology resulted in the detection of early Lyme disease in 19 of 21 (90%) of patients at the initial visit. In 5 of 21 cases we demonstrate the ability to detect B. burgdorferi in early Lyme disease directly from whole blood specimens prior to seroconversion.

Transcriptomics of in vitro immune-stimulated hemocytes from the Manila clam Ruditapes philippinarum using high-throughput sequencing

Background

The Manila clam (Ruditapes philippinarum) is a worldwide cultured bivalve species with important commercial value. Diseases affecting this species can result in large economic losses. Because knowledge of the molecular mechanisms of the immune response in bivalves, especially clams, is scarce and fragmentary, we sequenced RNA from immune-stimulated R. philippinarum hemocytes by 454-pyrosequencing to identify genes involved in their immune defense against infectious diseases.

Methodology and Principal Findings

High-throughput deep sequencing of R. philippinarum using 454 pyrosequencing technology yielded 974,976 high-quality reads with an average read length of 250 bp. The reads were assembled into 51,265 contigs and the 44.7% of the translated nucleotide sequences into protein were annotated successfully. The 35 most frequently found contigs included a large number of immune-related genes, and a more detailed analysis showed the presence of putative members of several immune pathways and processes like the apoptosis, the toll like signaling pathway and the complement cascade. We have found sequences from molecules never described in bivalves before, especially in the complement pathway where almost all the components are present.

Conclusions

This study represents the first transcriptome analysis using 454-pyrosequencing conducted on R. philippinarum focused on its immune system. Our results will provide a rich source of data to discover and identify new genes, which will serve as a basis for microarray construction and the study of gene expression as well as for the identification of genetic markers. The discovery of new immune sequences was very productive and resulted in a large variety of contigs that may play a role in the defense mechanisms of Ruditapes philippinarum.

Co-administration of attenuated Mycoplasma hyopneumoniae 168 strain with bacterial DNA enhances the local and systemic immune response after intranasal vaccination in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. M. hyopneumoniae infects pigs at mucosal surfaces of respiratory tract. The aim of the present study was to investigate if the protection rate against M. hyopneumoniae infection following intranasal immunization with attenuated M. hyopneumoniae 168 strain is improved by administration of bacterial DNA containing CpG motifs. Thirty pigs were immunized intranasally or intramuscularly and the levels of local respiratory tract and systemic immune responses were detected. The results showed that the number of intraepithelial lymphocytes in the tracheal fork, the levels of cytokine IL-6, and M. hyopneumoniae specific SIgA in local nasal cavity increased respectively after intranasal vaccination with the attenuated M. hyopneumoniae 168 strain alone. However, the levels of IL-10 and IFN-γ in local nasal cavity, the number of intraepithelial lymphocytes in trachea, CD4(+) and CD8(+) T lymphocytes in the lung and hilar lymph nodes, the specific IgG antibody level in serum on 35 day post immunization were all increased significantly after intranasal vaccination of the attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA. We concluded that intranasal administration of attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA may be effective in evoking the local cellular and humoral immune response in the respiratory tract and the systemic immune response. Intranasal vaccination will be effective in prevention of the transmission and prevalence of MPS.

Edwardsiella tarda DnaJ is a virulence-associated molecular chaperone with immunoprotective potential

Members of the DnaJ/Hsp40 family play an important role in protein homeostasis by regulating the activity of DnaK/Hsp70. In this study, we examined the activity and function of the DnaJ from Edwardsiella tarda, a serious fish pathogen that can also infect humans and birds. In silico analysis indicated that E. tarda DnaJ contains structural features, i.e. the J domain, the glycine/phenylalanine-rich region, and the zinc-finger domain, that are conserved among Type I Hsp40. Purified recombinant DnaJ was able to stimulate the ATPase activity of DnaK. Pull-down assay indicated that DnaJ could interact specifically with DnaK. Mutation of the conserved HPD site in the J domain completely abolished the DnaK-stimulating effect of DnaJ. To examine the functional importance of DnaJ, a dnaJ-defective mutant was constructed. Compared to the wild type, the dnaJ mutant (i) was retarded in growth and more sensitive to H₂O₂-induced oxidative damage, (ii) dramatically reduced in general bacterial virulence and in blood dissemination capacity, and (iii) significantly weakened in the ability to block macrophage activation and to survive within macrophages. Furthermore, when used as a subunit vaccine, purified recombinant DnaJ induced protective immunity in Japanese flounder (Paralichthys olivaceus). Taken together, these results indicate that DnaJ plays an important role in the pathogenesis of E. tarda probably by functioning as a DnaK partner and that DnaJ, with its immunoprotective property, may be useful in the control of E. tarda infection in aquaculture.

[Role of Toll-like receptors in the therapeutic effect of probiotics]

We considered data on the interaction of probiotics with Toll-like receptors. Is was shown that the probiotic effect may have and intact bacterial cells, living or dead, and their structural components. The basis of the surface structures and the DNA of probiotics is the ability to interact with Toll-like receptors, and this interaction can lead to uneven effects, which greatly depends on the strain of probiotic. Hence the obvious need for a more detailed study of the effects of the interaction of probiotic strains with the Toll-receptors. The criteria for evaluating new drugs probiotioticheskih and feasibility of optimal probiotic in a particular clinical case.

Immunoadjuvant effects of bacterial genomic DNA and CpG oligodeoxynucleotides on avian influenza virus subtype H5N1 inactivated oil emulsion vaccine in chicken

This study investigated the immunoadjuvant effects of three types of bacterial genomic DNA and CpG oligonucleotides (CpG ODN) on the avian influenza virus (AIV) subtype H5N1 inactivated oil emulsion vaccine under two immunization strategies. The genomic DNA extracted from Escherichia coli O(2), Staphylococcus aureus,Streptococcus faecalis FQ68, and synthetic CpG ODN were used as adjuvants, and their effects on the AIV oil emulsion vaccine were examined in chickens. The results indicated that when administered separately from the vaccine, adjuvants induced lower haemagglutination inhibition (HI) titres and serum IgG titres but resulted in higher concentrations of IFN-gamma and IL-10. In contrast, when combined with the oil emulsion vaccine prior to inoculation, CpG ODN induced higher HI, IgG titres and IFN-gamma concentration but resulted in lower IL-10 concentration. These data suggest that, depending on the immunization approaches, adjuvants may exert distinct immune effects in chickens receiving AIV H5N1 oil emulsion vaccine: the prior incorporation of CpG ODN into the vaccine may augment both the humoral and Th1 type immune responses, while separate inoculation of adjuvants has not shown better adjuvanticity.

DNA motifs suppressing TLR9 responses

Immune cells respond to bacterial DNA containing unmethylated CpG motifs via Toll-like receptor 9 (TLR9). Given the apparent role of TLR9 in development of systemic lupus erythematosus (SLE), there is interest in the development of TLR9 inhibitors. TLR9-mediated responses are reported to be inhibited by a confusing variety of different DNA sequences and structures. To aid characterization, we have provisionally categorized TLR9-inhibitory oligodeoxynucleotides (ODN) into 4 classes, on the basis of sequence and probable mode of action. Class I are short G-rich ODN, which show sequence-specific inhibition of all TLR9 responses, and may be direct competitive inhibitors for DNA binding to TLR9. Class II are telomeric repeat motifs that inhibit STAT signaling, and thus are not specific to TLR9 responses. Because Class II ODN are generally made as 24-base phosphorothioate-modified ODN (PS-ODN), they also fall into Class IV, defined as long PS-ODN, which inhibit TLR9 responses in a sequence-nonspecific manner. Class III includes oligo (dG) that forms a 4-stranded structure and inhibits DNA uptake. The Class I G-rich motifs show the most promise as selective and potent TLR9 inhibitors for therapeutic applications.

Decreased suppression of immune stimulatory CpG motifs in plant DNA

Due to differential content of CpG motifs in genomic DNA of organisms like bacteria and mammals, CpG-containing DNA delivers a danger or immunostimulatory signal that is recognized by Toll-like receptor 9 in mammalian cells. Here we show that genomic DNA from several plants promote proliferation and CD69 expression as well as activate NFkappaB and JNK pathways in murine B lymphocytes. Plant DNA synergize with specific antigen in activating B cells in a dose-dependent manner. Using a computational method we compared the usage of CpG motif related sequences in DNA of plants, bacteria, mammals or other species. It was found that the CpG motif suppression is much less significant in plant DNA than in mammalian genomes. These computation results partially explain the immunostimulatory activity of plant DNA observed in biological experiments, and lead to the hypothesis that plants respond to plant pathogens by recognizing CpG motifs in the pathogens' genomic DNA. Collectively this work provides new evidence for further understanding the interactions between plants and the human immune system or homeostasis, and between plants and their pathogens. The hypothesis that CpG dependent immunomodulation is a feature of plant DNA that contributes to plant nutrition or food/pollen allergy is also discussed.

Bacterial DNA confers neuroprotection after optic nerve injury by suppressing CD4+CD25+ regulatory T-cell activity

PURPOSE

Protective autoimmunity attenuates secondary degeneration after central nervous system (CNS) injury. Such neuroprotection is achieved via activation of autoimmune CD4(+)CD25(-) effector T cells (Teffs) or suppression of naturally occurring CD4(+)CD25(+) regulatory T cells (Tregs). In this study the ability of bacterial DNA, characterized by unmethylated CpG islands, to downregulate Treg activity and therefore, to confer neuroprotection was investigated.

METHODS

The effects of CpG on suppressive activity of mouse Tregs were studied by coculturing Tregs with Teffs and measuring proliferation by radiolabeled thymidine. The neuroprotective effects of CpG-mediated Treg suppression was examined in rats after optic nerve crush.

RESULTS

Teff proliferation in response to T-cell receptor stimuli was significantly reduced when the Teffs were cocultured with Tregs, compared with Teff activation when cultured alone. Treating Tregs with CpG reduced their suppressive activity and restored Teff proliferation to baseline levels. CpG injection in rats with optic nerve crush conferred significant neuroprotection compared with that in untreated control rats (118 +/- 8 cells/mm(2) vs. 69 +/- 5 cells/mm(2), respectively; mean +/- SEM; P < 0.05). CpG-mediated neuroprotection was accompanied by significantly increased T-cell infiltration at the injury site. Similar CpG treatment of athymic nude rats yielded no neuroprotection, further suggesting a T-cell-dependent mechanism of CpG action.

CONCLUSIONS

These findings strongly support the notion that alleviation of Treg suppression after injury benefits neuronal survival. Bacterial DNA attenuation of Treg suppressive activity may represent an evolutionary adaptation that curbs the amplified infection risk after CNS trauma, due to blood-brain barrier breakdown. This study may prompt development of new neuroprotective therapies aimed at the immune system, to benefit the injured CNS.

Adjuvant effect of CIA07, a combination ofEscherichia coliDNA fragments and modified lipopolysaccharides, on the immune response to hepatitis B virus surface antigen

CIA07 is an immunostimulatory agent composed of bacterial DNA fragments and modified lipopolysaccharide, which has antitumor activity against bladder cancer in mice. In this study, the adjuvant activity of CIA07 was evaluated using hepatitis B virus surface antigen (HBsAg) as the immunogen. Mice were immunized intramuscularly three times at 1-week intervals with HBsAg alone or in combination with alum, bacterial DNA fragments, modified lipopolysaccharide, CIA07 or CpG1826, and immune responses were assessed. At 1 week after the final injection, the HBsAg-specific total serum IgG antibody titer in CIA07-treated mice was 14 times higher than that in animals administered antigen alone, six times higher than in mice given alum or bacterial DNA fragments and twice as high as those treated with modified lipopolysaccharide or CpG1826, and remained maximal until 8 weeks postimmunization. Animals receiving antigen alone or plus alum displayed barely detectable HBsAg-specific serum IgG2a antibody responses. However, coadministration of CIA07 with antigen led to markedly enhanced serum IgG2a antibody titer and IFN-gamma(+) production in splenocytes, indicating that CIA07 effectively induces Th1-type immune responses. In addition, the number of HBsAg-specific CD8(+) T cells in peripheral blood mononuclear cells was elevated in CIA07-treated mice. These data clearly demonstrate that CIA07 is able to induce both cellular and humoral immune responses to HBsAg, and confirm its potential as an adjuvant in therapeutic vaccines for hepatitis B virus infections.

Protective efficiency of DNA vaccination in Asian seabass (Lates calcarifer) against Vibrio anguillarum

Vibriosis is one of the most prevalent fish diseases caused by bacteria belonging to the genus Vibrio. Vibriosis caused by Vibrio anguillarum produces a 38-kDa major outer membrane porin protein (OMP) for biofilm formation and bile resistant activity. The gene encoding the porin was used to construct DNA vaccine. The protective efficiency of such vaccine against V. anguillarum causing acute vibrio haemorrhagic septicaemia was evaluated in Asian seabass (Lates calcarifer Bloch), a common species of the Indian coast and a potential resource for the aquaculture industry. In vitro protein expression of porin gene was determined by fluorescent microscopy after transfection of seabass kidney cell line (SISK). Fish immunized with a single intramuscular injection of 20 microg of the OMP38 DNA vaccine showed significant serum antibody levels in 5th and 7th weeks after vaccination, compared to fish vaccinated with the control eukaryotic expression vector pcDNA3.1. Asian seabass vaccinated with the OMP38 DNA vaccine was challenged with pathogenic V. anguillarum by intramuscular injection. A relative percent survival (RPS) rate of 55.6% was recorded. Bacterial agglutination and serum complement activity was analysed by using DNA vaccinated seabass serum above 80% of analysed strain was killed at the highest agglutination titre. Histopathological signs of V. anguillarum challenged fish were observed in around 45% of pVAOMP38, 90% of PBS and 87% of pcDNA3.1-vaccinated control fish. The results indicate that L. calcarifer vaccinated with a single dose of DNA plasmid encoding the major outer membrane protein shows moderate protection against acute haemorrhagic septicaemia and mortality by V. anguillarum experimental infection.

Identification by genomic immunization of a pool of DNA vaccine candidates that confer protective immunity in mice against Neisseria meningitidis serogroup B

We have shown previously that expression library immunization is viable alternative approach to induce protective immunity against Neisseria meningitidis serogroup B. In this study we report that few rounds of library screening allow identification of protective pools of defined antigens. A previously reported protective meningococcal library (L8, with 600 clones) was screened and two sub-libraries of 95 clones each were selected based on the induction of bactericidal and protective antibodies in BALB/c mice. After sequence analysis of each clone within these sub-libraries, we identified a pool of 20 individual antigens that induced protective immune responses in mice against N. meningitidis infection, and the observed protection was associated with the induction of bactericidal antibodies. Our studies demonstrate for the first time that ELI combined with sequence analysis is a powerful and efficient tool for identification of candidate antigens for use in a meningococcal vaccine.

Periodontal bacterial DNA suppresses the immune response to mutans streptococcal glucosyltransferase

Certain CpG motifs found in bacterial DNA enhance immune responses through Toll-like receptor 9 (TLR-9) and may also demonstrate adjuvant properties. Our objective was to determine if DNA from bacteria associated with periodontal disease could affect the immune response to other bacterial antigens in the oral cavity. Streptococcus sobrinus glucosyltransferase (GTF), an enzyme involved in dental caries pathogenesis, was used as a test antigen. Rowett rats were injected with aluminum hydroxide (alum) with buffer, alum-GTF, or alum-GTF together with either Escherichia coli DNA, Fusobacterium nucleatum DNA, or Porphyromonas gingivalis DNA. Contrary to expectation, animals receiving alum-GTF plus bacterial DNA (P. gingivalis in particular) demonstrated significantly reduced serum immunoglobulin G (IgG) antibody, salivary IgA antibody, and T-cell proliferation to GTF compared to animals immunized with alum-GTF alone. A diminished antibody response was also observed after administration of alum-GTF with the P. gingivalis DNA either together or separately, indicating that physical complexing of antigen and DNA was not responsible for the reduction in antibody. Since TLR triggering by DNA induces synthesis of prospective suppressive factors (e.g., suppressor of cytokine signaling [SOCS]), the effects of P. gingivalis DNA and GTF exposure on rat splenocyte production of SOCS family molecules and inflammatory cytokines were investigated in vitro. P. gingivalis DNA significantly up-regulated SOCS1 and SOCS5 expression and down-regulated interleukin-10 expression by cultured splenocytes. These results suggested that DNA from periodontal disease-associated bacteria did not enhance, but in fact suppressed, the immune response to a protein antigen from cariogenic streptococci, potentially through suppressive SOCS components triggered by innate mechanisms.

Bacterial DNA containing methylated CpG motifs retains immunostimulatory activity in synergy with modified lipopolysaccharides

We previously described the immunostimulatory activity of CIA07, a combination of bacterial DNA fragments and modified LPS, and demonstrated that CIA07 has antitumor activity in a mouse bladder cancer model. In this study, we investigated whether methylation of the CpG motifs on the bacterial DNA fragments affects the immunostimulatory potential of CIA07. E. coli DNA fragments were methylated with CpG methylase, and then combined with modified LPS for experiments. Our results revealed that methylated CIA07 (mCIA07) and unmethylated CIA07 were equally active in inducing cytokine secretion from human whole blood cells. In addition, both methylated DNA fragments and mCIA07 retained the ability to activate expression and nuclear translocation of NF-kappaB in RAW 264.7 cells. Finally, methylated DNA fragments and mCIA07 exhibited an antitumor activity comparable to those of their unmethylated counterparts in our mouse bladder cancer model. These data demonstrate that CpG methylation of E. coli DNA does not abrogate the immunostimulatory activity of DNA fragments or CIA07, suggesting that the synergistic activity by bacterial DNA in combination with LPS may be independent of the methylation status of CpG motifs.

Bacterial DNA induces the complement system activation in serum and ascitic fluid from patients with advanced cirrhosis

Translocation of intestinal bacteria to ascitic fluid is, probably, the first step in the development of spontaneous bacterial peritonitis in patients with cirrhosis. Proteins of the complement system are soluble mediators implicated in the host immune response to bacterial infections and its activation has been traditionally considered to be an endotoxin-induced phenomenon. The aim of this study was to compare the modulation of these proteins in response to the presence of bacterial DNA and/or endotoxin in patients with advanced cirrhosis and ascites in different clinical conditions. Groups I and II consisted of patients without/with bacterial DNA. Group III included patients with spontaneous bacterial peritonitis and Group IV with patients receiving norfloxacin as secondary long-term prophylaxis of spontaneous bacterial peritonitis. Serum and ascitic fluid levels of endotoxin and truncated residues of the complement system were measured by ELISA. The complement system is triggered in response to bacterial DNA, as evidenced by significantly increased levels of C3b, membrane attack complex, and C5a in patients from Groups II and III compared with patients without bacterial DNA (Group I) and those receiving norfloxacin (Group IV). Gram classification did not further differentiate the immune response between patients within groups II and III, even though endotoxin levels were, as expected, significantly higher in patients with bacterial DNA from gram-negative microorganisms. The complement protein activation observed in patients with bacterial DNA in blood and ascitic fluid is indistinguishable from that observed in patients with spontaneous bacterial peritonitis and may occur in an endotoxin-independent manner.

DNA and its cationic lipid complexes induce CpG motif-dependent activation of murine dendritic cells

Unmethylated CpG motifs in bacterial DNA, but not in vertebrate DNA, are known to trigger an inflammatory response of antigen-presenting cells (APC). In this study, we investigated the cytokine release from murine dendritic cells (DC) by the addition of various types of DNA in the free or complexed form with cationic lipids. Naked plasmid DNA and Escherichia coli DNA with immunostimulatory unmethylated CpG motifs induced pro-inflammatory cytokine secretion from granulocyte-macrophage colony-stimulating factor (GM-CSF)-cultured bone marrow-derived DC and the DC cell-line, DC2.4 cells, though vertebrate calf thymus DNA (CT DNA) with less CpG motifs did not. These characteristics differed from mouse peritoneal resident macrophages that do not respond to any naked DNA. The amount of cytokines released from the DC was significantly increased by complex formation with cationic lipids when CpG-motif positive DNAs were used. Unlike murine macrophages or Flt-3 L cultured DC, GM-CSF DC did not release inflammatory cytokines in response to the addition of CT DNA/cationic lipid complex, suggesting that the activation is completely dependent on CpG motifs. Taken together, the results of the present study demonstrate that murine DC produce pro-inflammatory cytokines upon stimulation with CpG-containing DNAs and the responses are enhanced by cationic lipids. These results also suggest that DC are the major cells that respond to naked CpG DNA in vivo, although both DC and macrophages will release inflammatory cytokines after the administration of a DNA/cationic lipid complex.

Immunogenicity and persistence of a targeted anti-caries DNA vaccine

We have previously reported that a targeted anti-caries DNA vaccine, pGJA-P, induced accelerated and increased antibody responses compared with a non-targeted anti-caries DNA vaccine. Recently, pGJA-P/VAX, a new targeted anti-caries DNA vaccine for human trials, was constructed by replacing the pCI vector used in the construction of pGJA-P with pVAX1, the only vector authorized by the US Food and Drug Administration in clinical trials. Here, we report on our exploration of the kinetics of the antibody responses generated following pGJA-P/VAX immunization and the persistence of pGJA-P/VAX at both the inoculation site and the draining lymph nodes. Intranasal vaccination of mice with pGJA-P/VAX induced strong antibody responses that lasted for more than 6 months. Furthermore, pGJA-P/VAX could still be detected at both the inoculation site and the draining cervical lymph nodes 6 months after immunization. Thus, the persistent immune responses are likely due to the DNA depot in the host, which acts as a booster immunization.

Construction of an oral recombinant DNA vaccine from H pylori neutrophil activating protein and its immunogenicity

AIM: To construct a live attenuated Salmonella typhimurium (S. typhimurium) strain harboring the H pylori neutrophil activating protein (HP-NAP) gene as an oral recombinant DNA vaccine, and to evaluate its immunogenicity.

METHODS: By genetic engineering methods, the genomic DNA of H pylori was extracted as a template. The total length of the HP-NAP gene was amplified by polymerase chain reaction (PCR) and cloned into pBT vector for sequencing and BLAST analysis, then subcloned into a eukaryotic expression vector pIRES followed by PCR identification and restriction enzyme digestion. The identified recombinant plasmid pIRES-NAP was transfected into COS-7 cells for target fusion protein expression, and its antigenicity was detected by Western blotting. Then the recombinant plasmid was transformed into a live attenuated S. typhimurium strain SL7207 as an oral vaccine strain, and its immunogenicity was evaluated with animal experiments.

RESULTS: A 435 bp product was cloned using high homology with HP-NAP gene in GenBank (more than 98%). With identification by PCR and restriction enzyme digestion, a recombinant eukaryotic expression plasmid pIRES-NAP containing the HP-NAP gene of H pylori was successfully constructed. The expressed target protein had a specific reaction with H pylorii whole cell antibody and showed a single strip result detected by Western blotting. Oral immunization of mice with recombinant DNA vaccine strain SL7207 (pIRES-NAP) also induced a specific immune response.

CONCLUSION: The successful construction of HP-NAP oral DNA vaccine with good immunogenicity may help to further investigate its immunoprotection effects and develop vaccine against H pylori infection.

Studies on immunogenicity and protective efficacy of DnaJ of Salmonella Typhi against lethal infection by Salmonella Typhimurium in mice

In the present study DnaJ (HSP40) of Salmonella enterica serovar Typhi has been evaluated for its immunogenicity and efficacy in protecting mice against lethal challenge by S. enterica serovar Typhimurium infection. DnaJ was amplified by PCR of the genomic DNA of S. Typhi and subsequently cloned in pQE-30 expression vector. The protein was induced by IPTG and purified using Ni-NTA chromatography under denaturing conditions. After refolding in vitro the immune response was evaluated by injecting 40 microg DnaJ protein/mouse i.p. on 0th, 7th and 28th day. The results showed a significant increase in antibody titre and lymphocyte proliferation in animals immunised with DnaJ as compared to control. Further there was an appreciable increase in IL-2, IL-4, IFN-gamma production in lymphocytes isolated from immunised mice as compared to control. In this limited study, immunisation of mice with DnaJ was found to provide 70% protection against lethal challenge by S. Typhimurium indicating the possible use of DnaJ as vaccine candidate against typhoid.

Adjuvant properties of CpG oligonucleotides in primates

Unlike mammalian DNA, bacterial, plasmid, and synthetic DNA containing unmethylated CpG dinucleotides in specific sequence contexts are recognized by the Toll-like receptor 9 expressed by B cells and plasmacytoid dendritic cells, and trigger the activation of the innate and adaptive immune system. Upon signaling, CpG DNA induces B cells, natural killer cells, macrophages, and dendritic cells to proliferate, differentiate, take up, and present antigen and secrete a variety of immunoglobulins, chemokines, and predominantly Th1-type cytokines. Preclinical studies in mice and primates show that DNA sequences containing CpG motifs can selectively promote cellular and/or humoral immune responses in vivo. Early results from ongoing clinical studies indicate that CpG oligonucleotides (ODN) are well tolerated and improve the immune response to microbial vaccines. This work examines the progress in utilizing CpG ODN as adjuvants in conventional and DNA vaccines.