Partial protection against SIV challenge by vaccination of adenovirus and MVA vectors in rhesus monkeys.

This study explores the effect of priming rhesus monkeys with an Ad5/35 vector expressing simian immunodeficiency virus (SIV) gag and gp120, and then boosting the animals with an modified vaccinia virus Ankara (MVA) vector encoding the same antigens after a 2-month interval. The animals were intravenously challenged with 100 TCID50 of highly pathogenic SIVmac239 virus 2 months after the booster vaccination. The priming vaccination induced robust SIV-specific cell-mediated and humoral immune responses, and boosting further enhanced the cellular immunity. Vaccination reduced peak and long-term viral loads by 1-2 logs for a period of >6 months, as reflected by a reduction in both the SIV RNA and DNA levels. Of considerable interest, the immunized monkeys did not suffer from loss of CD4 T cells, particularly central memory CD4 T cells. These results demonstrate that prophylactic vaccination with Ad5/35 followed by MVA reduces viral replication and prevents CD4 T-cell loss, and that these effects may decrease the likelihood of disease progression.

Immunological priming potentiates non-viral anti-inflammatory gene therapy treatment of neuropathic pain.

We recently described a non-viral gene therapy paradigm offering long-term resolution of established neuropathic pain in several animal models. Here, the requirements for long-term therapeutic effects are described, and evidence is provided for a mechanism of action based on immunological priming of the intrathecal (i.t.) space. Long-term pain reversal was achieved when two i.t. injections of various naked plasmid DNA doses were separated by 5 h to 3 days. We show that an initial DNA injection, regardless of whether a transgene is included, leads to an accumulation of phagocytic innate immune cells. This accumulation coincides with the time in which subsequent DNA injection efficacy is potentiated. We show the ability of non-coding DNA to induce short-term pain reversal that is dependent on endogenous interleukin-10 (IL-10) signaling. Long-term efficacy requires the inclusion of an IL-10(F129S) transgene in the second injection. Blockade of IL-10, by a neutralizing antibody, either between the two injections or after the second injection induces therapeutic failure. These results show that this gene therapy paradigm uses an initial 'priming' injection of DNA to induce accumulation of phagocytic immune cells, allowing for potentiated efficacy of a subsequent 'therapeutic' DNA injection in a time- and dose-dependent manner.

A suppressive oligodeoxynucleotide inhibits ocular inflammation.

Synthetic oligodeoxynucleotides (ODN) expressing 'suppressive' TTAGGG motifs down-regulate a variety of proinflammatory and T helper type 1 (Th1)-mediated pathological immune responses. The ability of the archetypal suppressive ODN A151 to inhibit ocular inflammation was examined in two murine models: experimental autoimmune uveitis, induced by immunization with a retinal antigen, interphotoreceptor retinoid-binding protein (IRBP) and adoptively transferred ocular inflammation, induced by transferring Th1 cells specific to hen egg lysozyme (HEL) into recipient mice that express HEL in their eyes. A151 treatment suppressed the inflammation in both models. In addition, A151 inhibited IRBP-specific cytokine production and lymphocyte proliferation in mice immunized with IRBP. These findings suggest that suppressive ODN affects both afferent and efferent limbs of the immunopathogenic process and may be of use in the treatment of autoimmune ocular inflammation.

Effect of therapeutic immunization using Ad5/35 and MVA vectors on SIV infection of rhesus monkeys undergoing antiretroviral therapy.

Antiretroviral therapy (ART) effectively slows the progression of AIDS. However, drug resistance and/or toxicity can limit the utility of ART in many patients. In this study, we assessed whether a viral vector-based vaccine can be used as a therapeutic vaccine in simian immunodeficiency virus (SIV)-infected monkeys. The effect of vaccinating SIVmac239-infected rhesus monkeys with an SIV gag and gp120-expressing adenovirus (Ad) vector vaccine and a modified vaccinia Ankara (MVA) vaccine was explored while being treated with ART. Rhesus monkeys were intravenously infected with 10 and 1000 TCID(50) (50% tissue culture infectious dose) of SIVmac239. Two months after SIV infection, the monkeys received a 4-month treatment with ART. Some of the monkeys were immunized with adenovirus-based vaccine and MVA-based vaccine with 2 months interval during ART. Viral load, CD4 count and SIV-specific immune responses were observed for 7 months after interruption of ART. The vaccinated animals had higher (i) CD4 counts, (ii) SIV-specific cell-mediated immune responses and (iii) anti-SIV-neutralizing antibody (Ab) titers than monkeys treated with ART alone. More importantly, the vaccination significantly reduced the SIV RNA load from animals infected with a low dose of SIV (10 TCID(50)). The anti-SIV cell-mediated and humoral responses induced by the vaccination was inversely correlated with a reduction in SIV viral load and positively correlated with an increase in CD4(+) T cell counts. These results suggest that vaccination can improve antiviral cell-mediated and humoral immunity, which may contribute to controlling viral replication.

Prime-boost vaccination with plasmid DNA and a chimeric adenovirus type 5 vector with type 35 fiber induces protective immunity against HIV.

Immunization involving a DNA vaccine prime followed by an adenovirus type 5 (Ad5) boost elicited a protective immune response against SHIV challenge in monkeys. However, the hepatocellular tropism of Ad5 limits the safety of this viral vector. This study examines the safety and immunogenicity of a replication-defective chimeric Ad5 vector with the Ad35 fiber (Ad5/35) in BALB/c mice and rhesus monkeys. This novel Ad5/35 vector showed minimal hepatotoxicity after intramuscular administration with the novel Ad5/35 vector. In addition, an Ad5/35 vector expressing HIV Env gp160 protein (Ad5/35-HIV) generated strong HIV-specific immune responses in both animal models. Priming with a DNA vaccine followed by Ad5/35-HIV boosting yielded protection against a gp160-expressing vaccinia virus challenge in BALB/c mice. The Ad5/35-HIV vector was significantly less susceptible to the pre-existing Ad5 immunity than a comparable Ad5 vector. These findings indicate that an Ad5/35 vector-based HIV vaccine may be of considerable value for clinical use.

Hierarchical recognition of CpG motifs expressed by immunostimulatory oligodeoxynucleotides.

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs trigger human PBMC to proliferate and secrete Ig, cytokines and chemokines. CpG ODN have entered clinical trials, and show promise as vaccine adjuvants, antiallergens, and for the treatment of infectious diseases and cancer. ODNs under consideration for human use vary in the sequence, number and location of the CpG motifs they contain. Yet little is known of the magnitude of the immune response elicited by these diverse ODNs, or the rules governing their interaction with immune cells. This work compares the proliferative, IgM, IL-6 and IP-10 response of PBMC from normal donors to a diverse panel of CpG ODNs. Results indicate that ODNs expressing 3-4 different CpG motifs are strongly stimulatory. The location of these motifs is important, with those at the 5' end exerting the greatest influence on ODN activity. These findings provide a basis for the rational design of ODNs optimized for clinical use.

Response of peripheral blood mononuclear cells from lupus patients to stimulation by CpG oligodeoxynucleotides.

OBJECTIVES: Increased levels of hypomethylated CpG-containing DNA in sera from patients with systemic lupus erythematosus (SLE) may contribute to the initiation and/or perpetuation of the disease. This study characterizes the in vitro response of peripheral blood mononuclear cells (PBMC) from SLE patients to CpG DNA. METHODS: Secretion of cytokines and IgM, cell proliferation and up-regulation of co-stimulatory molecules were evaluated in PBMC from SLE patients (n=24) and normal controls (n=24) after stimulation with synthetic oligodeoxynucleotides (ODN) containing CpG motifs. RESULTS: Up-regulation of co-stimulatory molecules and the secretion of interferon-alpha and interleukin-6 (IL-6) in response to CpG ODN was significantly reduced in monocytes and dendritic cells from SLE patients. Secretion of interferon-gamma by natural killer (NK) cells was also reduced. In contrast, the IgM and IL-10 response of B cells to CpG ODN was normal. CONCLUSION: Monocytes, dendritic cells and NK cells from SLE patients respond abnormally to CpG ODN stimulation, which may contribute to the cytokine imbalance observed in SLE.

Transplacental genetic immunization after intravenous delivery of plasmid DNA to pregnant mice.

A number of factors influence the development of tolerance, including the nature, concentration, and mode of Ag presentation to the immune system, as well as the age of the host. The studies were conducted to determine whether immunizing pregnant mice with liposome-encapsulated DNA vaccines had an effect on the immune status of their offspring. Two different plasmids (encoding Ags from HIV-1 and influenza virus) were administered i.v. to pregnant mice. We examined the uptake of plasmid DNA by the fetuses until the 21st postcoital day, but little such transfer occurred in early pregnancy. At 9.5 days postconception with cationic liposomes, injected plasmid was present in the tissues of the fetus, consistent with transplacental transfer. When the offspring of vaccinated dams were immunized with DNA vaccine, they mounted stronger Ag-specific immune responses than controls, and were protected against challenge by homologous influenza virus after vaccination. Moreover, such immune responses were strong in the offspring of mothers injected with DNA plasmid 9.5 days after coitus. These results suggest that DNA-vaccinated mothers confer the Ag-specific immunity to their progeny.

Activation of microglia and astrocytes by CpG oligodeoxynucleotides.

Bacterial DNA and synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs stimulate cells of the immune system to secrete a variety of cytokines and chemokines. This function can be carried out by microglia and astrocytes in the CNS. To evaluate the effect of CpG ODN on microglia and astrocytes, purified cells were isolated and cultured in vitro. CpG ODN rapidly up-regulated their production of IL-1beta, IL-6, IL-12, TNFalpha, MIP-1alpha and/or MIP-1beta. In vivo, systemically administered CpG ODN up-regulated the expression of mRNA encoding cytokines and chemokines in normal mouse brain. These findings suggest that CpG ODN can directly activate immune cells of the CNS.

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

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

Cutting edge: Role of Toll-like receptor 9 in CpG DNA-induced activation of human cells.

Unmethylated CpG motifs present in bacterial DNA stimulate a rapid and robust innate immune response. Human cell lines and PBMC that recognize CpG DNA express membrane-bound human Toll-like receptor 9 (hTLR9). Cells that are not responsive to CpG DNA become responsive when transfected with hTLR9. Expression of hTLR9 dramatically increases uptake of CpG (but not control) DNA into endocytic vesicles. Upon cell stimulation, hTLR9 and CpG DNA are found in the same endocytic vesicles. Cells expressing hTLR9 are stimulated by CpG motifs that are active in primates but not rodents, suggesting that evolutionary divergence between TLR9 molecules underlies species-specific differences in the recognition of bacterial DNA. These findings indicate that hTLR9 plays a critical role in the CpG DNA-mediated activation of human cells.

Genomic DNA released by dying cells induces the maturation of APCs.

Mature APCs play a key role in the induction of Ag-specific immunity. This work examines whether genomic DNA released by dying cells provides a stimulus for APC maturation. Double-stranded but not single-stranded genomic DNA triggered APC to up-regulate expression of MHC class I/II and various costimulatory molecules. Functionally, dsDNA enhanced APC function in vitro and improved primary cellular and humoral immune responses in vivo. These effects were dependent on the length and concentration of the dsDNA but were independent of nucleotide sequence. The maturation of APC induced by dsDNA may promote host survival by improving immune surveillance at sites of tissue injury/infection.

Disassociation of sex hormone levels and cytokine production in SLE patients.

This study examines whether changes in the cytokine milieu of patients with systemic lupus erythematosus (SLE) are associated with abnormal levels of sex hormone levels in serum. The concentration of 17beta-estradiol (E2), progesterone (Pg) and dehydroepiandrosterone-sulphate (DHEAS) was monitored in sera from 128 lupus patients and 96 controls, and correlated with the activity of their cytokine secreting cells. Results indicate that SLE patients have (i) significantly fewer cells secreting IFNgamma, (ii) increased serum E2 and Pg levels, and (iii) reduced serum DHEAS levels compared to normal controls. However, the observed abnormalities in the cytokine milieu of SLE patients did not correlate with abnormalities in serum sex hormone levels. Instead, the association between IFNgamma production and DHEAS levels evident in healthy controls is absent in SLE patients, suggesting that cells from lupus patients are defective in their ability to produce IFNgamma in response to physiologic stimuli. Similarly, the normal correlation between IL-4 production and E2 levels was lost in patients with severe disease. Thus, while it remains possible that increased E2 and reduced DHEAS levels in lupus patients may help induce cytokine abnormalities early in disease, the subsequent cytokine imbalance does not correlate with sex hormone levels.

The regulation of DNA vaccines.

The framework for regulating DNA vaccines has been in place since the first clinical trial was initiated in the mid-1990s. American and European regulatory guidance has evolved on the basis of insights provided by ongoing preclinical and clinical studies. These include analyses of the safety of DNA vaccines in normal volunteers, and recent data concerning the tissue distribution, persistence, and integration potential of DNA plasmids.

CpG motifs of DNA vaccines induce the expression of chemokines and MHC class II molecules on myocytes.

Determining how an immune response is initiated after in vivo transfection of myocytes with plasmids encoding foreign antigens is essential to understand the mechanisms of intramuscular (i. m.) genetic immunization. Since myocytes are facultative antigen-presenting cells lacking MHC class II and co-stimulatory molecules, it was assumed that their unique role upon DNA vaccination is to synthesize and secrete the protein encoded by the plasmid. Here we describe that i. m. injection of unmethylated CpG motifs induced the expression of chemokines (monocyte chemotactic protein-1) and MHC class II molecules on myocytes. Our results indicate that immunostimulatory DNA sequences (CpG motifs) of DNA vaccines augment synthesis of chemokine by myocytes with subsequent recruitment of inflammatory cells secreting IFN-gamma, a potent cytokine that up-regulates the expression of MHC class II molecules on myocytes. A myoblast cell line triple transfected with plasmids encoding MHC class II molecules and an immunodominant CD4 T cell epitope of influenza virus presented the endogenously synthesized peptide and activated specific T cells. These findings suggest that one mechanism for the immunogenicity of DNA vaccines consists in the presentation of peptides to CD4 T cells by in vivo plasmid-transfected myocytes.

Response of porcine peripheral blood mononuclear cells to CpG-containing oligodeoxynucleotides.

Exposure to bacterial DNA generates a "danger signal" that stimulates cellular elements of the mammalian immune system to proliferate and/or secrete cytokines. Stimulation is critically dependent on hexameric motifs that contain an unmethylated CpG dinucleotide: these are commonly found in bacterial but not vertebrate DNA. Different motifs are optimally stimulatory in different species. This work examines whether oligodeoxynucleotides (ODNs) containing CpG motifs stimulate peripheral blood mononuclear cells from pigs. Results show that pigs respond to CpG ODN by proliferating and secreting IL-6, IL-12 and TNF-alpha. By screening a large panel (>100) of ODNs, the palindromic hexamer 'ATCGAT' was identified as being optimally active in all animals examined (N=10). These findings are the first to establish the immunostimulatory activity of CpG ODN in pigs, and suggest that the therapeutic uses envisioned for these ODNs (as vaccine adjuvants and immunoprotective agents) may be applicable to husbandry animals.

Human peripheral blood cells differentially recognize and respond to two distinct CPG motifs.

Oligodeoxynucleotides (ODN) that contain unmethylated CpG dinucleotides trigger a strong innate immune response in vertebrates. CpG ODN show promise as vaccine adjuvants, anti-allergens, and immunoprotective agents in animal models. Their transition to clinical use requires the identification of motifs that are optimally stimulatory in humans. Analysis of hundreds of novel ODN resulted in the identification and characterization of two structurally distinct "clusters" of immunostimulatory CpG ODN. One cluster ("D") preferentially stimulates IFN-gamma production by NK cells, whereas the other ("K") stimulates cell proliferation and the production of IL-6 and IgM by monocytes and B cells. The distinct immunostimulatory properties of K and D ODN can improve the design of CpG-based products to achieve specific therapeutic goals.

Sex hormone levels correlate with the activity of cytokine-secreting cells in vivo.

This work examines the correlation between serum levels of oestrogen, progesterone and dehydroepiandrosterone sulphate (DHEA-S) and the number of human peripheral blood cells actively secreting interleukin (IL)-2, IL-4, IL-6, IL-10, tumour necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma) in vivo. Simultaneous assessment of serum hormone levels and cytokine-secreting cell activity throughout the menstrual cycle showed that the number of peripheral blood mononuclear cells (PBMC) able to secrete IL-4 in response to stimulation correlated significantly (P < 0.0001) with oestrogen levels and fluctuated with the menstrual cycle in pre-menopausal women. The activity of IFN-gamma-secreting cells, on the other hand, varied as a function of serum DHEA-S levels in pre-menopausal women (P < 0.0001). Similarly, the number of cells secreting IFN-gamma in men correlated with serum DHEA-S levels (P < 0.001). In contrast, post-menopausal women had fewer cells actively secreting cytokines and the activity of these cells did not correlate with sex hormone levels. These results suggest that sex hormones may modulate cytokine production in vivo and contribute to gender-related differences in normal and pathological immune responses.