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

TLR9-Activating CpG-B ODN but Not TLR7 Agonists Triggers Antibody Formation to Factor IX in Muscle Gene Transfer

Innate immune signals that promote B cell responses in gene transfer are generally ill-defined. In this study, we evaluate the effect of activating endosomal Toll-like receptors 7, 8, and 9 (TLR7, TLR7/8, and TLR9) on antibody formation during muscle-directed gene therapy with adeno-associated virus (AAV) vectors. We examined whether activation of endosomal TLRs, by adenine analog CL264 (TLR7 agonist), imidazolquinolone compound R848 (TLR7/8 agonist), or class B CpG oligodeoxynucleotides ODN1826 (TLR9 agonist), could augment antibody formation upon intramuscular administration of AAV1 expressing human clotting factor IX (AAV1-hFIX) in mice. The TLR9 agonist robustly enhanced antibody formation by the 1st week, thus initially eliminating systemic hFIX expression. By contrast, the TLR7 and TLR7/8 agonists did not markedly promote antibody formation, or significantly reduce circulating hFIX. We concurrently investigated the effects of these TLR agonists during muscle gene transfer on mature B cells and dendritic cells (DCs) in the draining lymph nodes including conventional DCs (CD11b+ or CD8α+ cDCs), monocyte-derived dendritic cells (moDCs), and plasmacytoid dendritic cells (pDCs). Only TLR9 stimulation caused a striking increase in the frequency of moDCs within 24 h. The TLR7/8 and TLR9 agonists activated pDCs, both subsets of cDCs, and mature B cells, whereas the TLR7 agonist had only mild effects on these cells. Thus, these TLR ligands have distinct effects on DCs and mature B cells, yet only the TLR9 agonist enhanced the humoral immune response against AAV-expressed hFIX. These new findings indicate a unique ability of certain TLR9 agonists to stimulate B cell responses in muscle gene transfer through enrichment of moDCs.

IFN Signaling in Inflammation and Viral Infections: New Insights from Fish Models

The overarching structure of the type I interferon (IFN) system is conserved across vertebrates. However, the variable numbers of whole genome duplication events during fish evolution offer opportunities for the expansion, diversification, and new functionalization of the genes that are involved in antiviral immunity. In this review, we examine how fish models provide new insights about the implication of virus-driven inflammation in immunity and hematopoiesis. Mechanisms that have been discovered in fish, such as the strong adjuvant effect of type I IFN that is used with DNA vaccination, constitute good models to understand how virus-induced inflammatory mechanisms can interfere with adaptive responses. We also comment on new discoveries regarding the role of pathogen-induced inflammation in the development and guidance of hematopoietic stem cells in zebrafish. These findings raise issues about the potential interferences of viral infections with the establishment of the immune system. Finally, the recent development of genome editing provides new opportunities to dissect the roles of the key players involved in the antiviral response in fish, hence enhancing the power of comparative approaches.

DNA vaccines for prostate cancer

DNA vaccines offer many advantages over other anti-tumor vaccine approaches due to their simplicity, ease of manufacturing, and safety. Results from several clinical trials in patients with cancer have demonstrated that DNA vaccines are safe and can elicit immune responses. However, to date few DNA vaccines have progressed beyond phase I clinical trial evaluation. Studies into the mechanism of action of DNA vaccines in terms of antigen-presenting cell types able to directly present or cross-present DNA-encoded antigens, and the activation of innate immune responses due to DNA itself, have suggested opportunities to increase the immunogenicity of these vaccines. In addition, studies into the mechanisms of tumor resistance to anti-tumor vaccination have suggested combination approaches that can increase the anti-tumor effect of DNA vaccines. This review focuses on these mechanisms of action and mechanisms of resistance using DNA vaccines, and how this information is being used to improve the anti-tumor effect of DNA vaccines. These approaches are then specifically discussed in the context of human prostate cancer, a disease for which DNA vaccines have been and continue to be explored as treatments.

Nanoparticulate mediated transcutaneous immunization: Myth or reality

Transcutaneous immunization (TCI) is a promising route of vaccine delivery through skin due to many well documented advantages. The main obstacle in TCI is the skin's top dead layer i.e. stratum corneum which is difficult to penetrate. Efficiently delivery of antigen to the immune competent cells of epidermis or dermis in TCI might elicit an effective immune response. In this review, skin immunology with a particular focus on potential of immunological active receptors in influencing adaptive immune responses is highlighted. The challenges with TCI and methods to improve it using different adjuvants, chemical and physical approaches, delivery systems, and combination of above methods to further improve immune response following skin application of antigen are elaborately discussed. Nanoparticulate vaccine delivery systems with reference to their applications in TCI are classified according to their chronological development. Conclusively, clinical translations of above methods are also briefly reviewed.

FROM THE CLINICAL EDITOR

Transcutaneous immunization has been investigated by many as a promising route of vaccination. In this comprehensive review article, the authors described and discussed the existing knowledge and difficulties in this approach. Furthermore, ways of improving transcutaneous delivery were also reviewed.

Effects of APC De-targeting and GAr modification on the duration of luciferase expression from plasmid DNA delivered to skeletal muscle

Immune responses to expressed foreign transgenes continue to hamper progress of gene therapy development. Translated foreign proteins with intracellular location are generally less accessible to the immune system, nevertheless they can be presented to the immune system through both MHC Class I and Class II pathways. When the foreign protein luciferase was expressed following intramuscular delivery of plasmid DNA in outbred mice, expression rapidly declined over 4 weeks. Through modifications to the expression plasmid and the luciferase transgene we examined the effect of detargeting expression away from antigen-presenting cells (APCs), targeting expression to skeletal muscle and fusion with glycine-alanine repeats (GAr) that block MHC-Class I presentation on the duration of luciferase expression. De-targeting expression from APCs with miR142-3p target sequences incorporated into the luciferase 3'UTR reduced the humoral immune response to both native and luciferase modified with a short GAr sequence but did not prolong the duration of expression. When a skeletal muscle specific promoter was combined with the miR target sequences the humoral immune response was dampened and luciferase expression persisted at higher levels for longer. Interestingly, fusion of luciferase with a longer GAr sequence promoted the decline in luciferase expression and increased the humoral immune response to luciferase. These studies demonstrate that expression elements and transgene modifications can alter the duration of transgene expression but other factors will need to overcome before foreign transgenes expressed in skeletal muscle are immunologically silent.

DNA vaccines: MHC II-targeted vaccine protein produced by transfected muscle fibres induces a local inflammatory cell infiltrate in mice

Vaccination with naked DNA holds great promise but immunogenicity needs to be improved. DNA constructs encoding bivalent proteins that bind antigen-presenting cells (APC) for delivery of antigen have been shown to enhance T and B cell responses and protection in tumour challenge experiments. However, the mechanism for the increased potency remains to be determined. Here we have constructed DNA vaccines that express the fluorescent protein mCherry, a strategy which allowed tracking of vaccine proteins. Transfected muscle fibres in mice were visualized, and their relationship to infiltrating mononuclear cells could be determined. Interestingly, muscle fibers that produced MHC class II-specific dimeric vaccine proteins with mCherry were for weeks surrounded by a localized intense cellular infiltrate composed of CD45⁺, MHC class II⁺ and CD11b⁺ cells. Increasing numbers of eosinophils were observed among the infiltrating cells from day 7 after immunization. The local infiltrate surrounding mCherry⁺ muscle fibers was dependent on the MHC II-specificity of the vaccine proteins since the control, a non-targeted vaccine protein, failed to induce similar infiltrates. Chemokines measured on day 3 in immunized muscle indicate both a DNA effect and an electroporation effect. No influence of targeting was observed. These results contribute to our understanding for why targeted DNA vaccines have an improved immunogenicity.

CpG-depleted adeno-associated virus vectors evade immune detection

Due to their efficient transduction potential, adeno-associated virus (AAV) vectors are leading candidates for gene therapy in skeletal muscle diseases. However, immune responses toward the vector or transgene product have been observed in preclinical and clinical studies. TLR9 has been implicated in promoting AAV-directed immune responses, but vectors have not been developed to circumvent this barrier. To assess the requirement of TLR9 in promoting immunity toward AAV-associated antigens following skeletal muscle gene transfer in mice, we compared immunological responses in WT and Tlr9-deficient mice that received an AAV vector with an immunogenic capsid, AAVrh32.33. In Tlr9-deficient mice, IFN-γ T cell responses toward capsid and transgene antigen were suppressed, resulting in minimal cellular infiltrate and stable transgene expression in target muscles. These findings suggest that AAV-directed immune responses may be circumvented by depleting the ligand for TLR9 (CpG sequences) from the vector genome. Indeed, we found that CpG-depleted AAVrh32.33 vectors could establish persistent transgene expression, evade immunity, and minimize infiltration of effector cells. Thus, CpG-depleted AAV vectors could improve outcome of clinical trials of gene therapy for skeletal muscle disease.

Targeting of a T cell agonist peptide to lysosomes by DNA vaccination induces tolerance in the nonobese diabetic mouse

CD4 T cells are crucial effectors in the pathology of type 1 diabetes (T1D). Successful therapeutic interventions for prevention and cure of T1D in humans are still elusive. Recent research efforts have focused on the manipulation of T cells by treatment with DNA. In this paper, we studied the effects of a DNA treatment strategy designed to target antigenic peptides to the lysosomal compartment on a monospecific T cell population termed 2.5mi(+) T cells that shares reactivity with the diabetogenic T cell clone BDC-2.5 in the NOD mouse. MHC class II tetramer analysis showed that repeated administrations were necessary to expand 2.5mi(+) T cells in vivo. This expansion was independent of Ag presentation by B cells. A single peptide epitope was sufficient to induce protection against T1D, which was not due to Ag-specific T cell anergy. Typical Th2 cytokines such as IL-10 or IL-4 were undetectable in 2.5mi(+) T cells, arguing against a mechanism of immune deviation. Instead, the expanded 2.5mi(+) T cell population produced IFN-γ similar to 2.5mi(+) T cells from naive mice. Protection against T1D by DNA treatment was completely lost in NOD.CD28(-/-) mice which are largely deficient of natural regulatory T cells (Treg). Although Ag-specific Foxp3(+) Treg did not expand in response to DNA treatment, diabetes onset was delayed in Treg-reconstituted and DNA-treated NOD.SCID mice. These observations provide evidence for a Treg-mediated protective mechanism that is independent of the expansion or de novo generation of Ag-specific Treg.

Modulation of plasmid DNA vaccine antigen clearance by caspase 12 RNA interference potentiates vaccination

The magnitude of the immune responses elicited by plasmid DNA vaccines might be limited, in part, by the duration of vaccine antigen expression in vivo. To explore strategies for improving plasmid DNA vaccine efficacy, we studied the apoptotic process in myocytes of mice vaccinated intramuscularly. We found that after vaccination, the proapoptotic protein caspase 12 (Casp12) was upregulated in myocytes coincident with the loss of vaccine antigen expression. To harness this observation to improve plasmid DNA vaccine efficacy, we used RNA interference technology, coadministering plasmid DNA expressing a short hairpin RNA (shRNA) of Casp12 with plasmid DNA vaccine constructs. This treatment with shRNA Casp12, administered twice within the first 10 days following vaccine administration, increased antigen expression 7-fold, the antigen-specific CD8(+) T cell immune response 6-fold, and antigen-specific antibody production 5-fold. This study demonstrates the critical role for Casp12 in plasmid DNA vaccine-induced immune responses and shows that increased antigen expression mediated by down-modulation of Casp12 can be used to potentiate vaccine efficacy.

Regulatory T cells suppress natural killer cells during plasmid DNA vaccination in mice, blunting the CD8+ T cell immune response by the cytokine TGFbeta

Background

CD4⁺CD25⁺ regulatory T cells (Tregs) suppress adaptive T cell-mediated immune responses to self- and foreign-antigens. Tregs may also suppress early innate immune responses to vaccine antigens and might decrease vaccine efficacy. NK and NKT cells are the first responders after plasmid DNA vaccination and are found at the site of inoculation. Earlier reports demonstrated that NKT cells could improve plasmid DNA efficacy, a phenomenon not found for NK cells. In fact, it has been shown that under certain disease conditions, NK cells are suppressed by Tregs via their release of IL-10 and/or TGFβ. Therefore, we tested the hypothesis that NK cell function is suppressed by Tregs in the setting of plasmid DNA vaccination.

Methodology/Principal Findings

In this study we show that Tregs directly inhibit NK cell function during plasmid DNA vaccination by suppressing the potentially 10-fold, NK cell-mediated, augmentation of plasmid DNA antigen-specific CD8⁺ T cells. We found that this phenomenon is dependent on the secretion of cytokine TGFβ by Tregs, and independent of IL-10.

Conclusions

Our data indicate a crucial function for Tregs in blocking plasmid DNA vaccine-elicited immune responses, revealing potentially novel strategies for improving the efficiency of plasmid DNA vaccines including chemical- or antibody-induced localized blockage of Treg-mediated suppression of NK cells at the site of plasmid DNA vaccine inoculation.

Non-classical natural killer T cells modulate plasmid DNA vaccine antigen expression and vaccine-elicited immune responses by MCP-1 secretion after interaction with a beta2-microglobulin-independent CD1d

The magnitude and durability of a plasmid DNA vaccine-induced immune response is shaped by immune effector molecules at the site of vaccination. In the present study, we show that antigen expression is modified by type II NKT cells, after interaction with a beta2-microglobulin-independent CD1d receptor. After activation, during the first days following plasmid DNA vaccination, NKT cells release IL-5 and MCP-1, leading to a T helper 0 (T(H)0) cytokine/chemokine profile and a stronger CD8(+)/CD4(+) T cell immune response. Our data indicate that this phenomenon was induced through the strong T(H)1 chemokine MCP-1 during the early phases of plasmid DNA vaccination because injecting the type II NKT cell-associated MCP-1 during the first 5 days led to 2-3-fold increases in vaccine-elicited T cell responses. This study demonstrates a critical role for NKT cells in plasmid DNA vaccine-induced immune responses. Manipulation of NKT cell function or co-administration of MCP-1 may represent novel methods for enhancing immune responses to plasmid DNA vaccines.

CD4+ T lymphocytes mediate in vivo clearance of plasmid DNA vaccine antigen expression and potentiate CD8+ T-cell immune responses

There is evidence that the limited immunogenicity of plasmid DNA vaccines is the result, at least in part, of the rapid clearance of vaccine antigen expression by antigen-specific immune responses. However, the cell types responsible for the clearance of plasmid DNA vaccine antigens are not known. Here we demonstrate that macrophages, NK cells, and CD8(+) T cells did not significantly contribute to the DNA antigen clearance but CD4(+) T cells played the crucial role in attenuating plasmid DNA vaccine antigen expression. Adoptive transfer experiments demonstrate that CD4(+) T cells facilitated DNA vaccine antigen clearance in a Fas/FasL-dependent manner. Furthermore, we show that depletion of CD4(+) T cells prevented the clearance of vaccine antigen and the appearance of a CD8(+) T-cell immune response. Inoculation of major histocompatibility complex class II KO mice with the plasmid DNA led to persistent antigen expression and abolition of a CD8(+) T-cell immune response. Importantly, the prolongation of antigen expression by disrupting the CD4(+) T-cell Fas/FasL myocytes signaling led to a 3- to 5-fold increase of antigen-specific CD8(+) T-cell responses. These data demonstrate a dominant role of CD4(+) T cell-mediated cytotoxicity in plasmid DNA vaccine antigen clearance.

Particle-based vaccines for transcutaneous vaccination

Immunization concepts evolve with increasing knowledge of how the immune system works and the development of new vaccination methods. Traditional vaccines are made of live, attenuated, killed or fragmented pathogens. New vaccine strategies can take advantage of particulate compounds--microspheres or nanoparticles--to target antigen-presenting cells better, which must subsequently reach the secondary lymphoid organs, which are the sites of the immune response. The use of the skin as a target organ for vaccine delivery stems from the fact that immature dendritic cells (DCs), which are professional antigen-presenting cells can be found at high density in the epidermis and dermis of human or animal skin. This has led to design various methods of dermal or transcutaneous vaccination. The quality and duration of the humoral and cellular responses to vaccination depend on the appropriate targeting of antigen-presenting cells, of the vaccine dose, route of administration and use of adjuvant. In this review, we will focus on the use of micro- and nano-particles to target the skin antigen-presenting cells and will discuss recent advances in the field of transcutaneous vaccination in animal models and humans.

Kinetics of recombinant adenovirus type 5, vaccinia virus, modified vaccinia ankara virus, and DNA antigen expression in vivo and the induction of memory T-lymphocyte responses

While a new generation of vaccine vectors has been developed for eliciting cellular immune responses, little is known about the optimal routes for their administration or about the ramifications of the kinetics of in vivo vaccine antigen expression for immunogenicity. We evaluated the kinetics of vaccine antigen expression by real-time in vivo photon imaging and showed dramatic differences in these kinetics using different vectors and different routes of administration. Further, using a gamma interferon enzyme-linked immunospot assay to measure T-lymphocyte immune responses, we observed an association between the kinetics of vaccine antigen expression in vivo and the magnitude of vaccine-elicited memory T-lymphocyte responses. These results highlight the utility of the real-time in vivo photon-imaging technology in evaluating novel immunization strategies and suggest an association between the kinetics of vaccine antigen clearance and the magnitude of vaccine-elicited T-lymphocyte memory immune responses.

DNA vaccines for poultry: the jump from theory to practice

DNA vaccines could offer a solution to a number of problems faced by the poultry industry; they are relatively easy to manufacture, stable, potentially easy to administer, can overcome neonatal tolerance and the deleterious effects of maternal antibody, and do not cause disease pathology. Combined with this, in ovo vaccination offers the advantage of reduced labor costs, mass administration and the induction of an earlier immune response. Together, this list of advantages is impressive. However, this combined technology is still in its infancy and requires many improvements. The potential of CpG motifs, DNA vaccines and in ovo vaccination, however, can be observed by the increasing number of recent reports investigating their application in challenge experiments. CpG motifs have been demonstrated to be stimulatory both in vitro and in vivo. In addition, DNA vaccines have been successfully delivered via the in ovo route, albeit not yet through the amniotic fluid. Lastly, a recent report has demonstrated that a DNA vaccine against infectious bronchitis virus administered via in ovo vaccination, followed by live virus boost, can slightly improve on the protective effect induced by the live virus alone. Therefore, DNA vaccination via the in ovo route is promising and offers potential as a poultry vaccine, however, efficacy needs to be improved and the costs of production reduced before it is likely to be beneficial to the poultry industry in the long term.

MHC expression and chemokine production in the murine vagina following intra-vaginal administration of ligands to toll-like receptors 3, 7 and 9

The expression of MHC class I, MHC class II and the chemokines IP-10, MIP-1alpha, RANTES, fractalkine and I-TAC has been analyzed after intra-vaginal treatment with three synthetic toll-like receptors (TLR) agonists-double-stranded RNA (poly I:C), imiquimod and CpG-rich oligonucleotides (CpG-ODN). These compounds act mainly through TLR3, TLR7 and TLR9, respectively. CpG-ODN induced an accumulation of leucocytes in the vagina, and a strong up-regulation of MHC class I expression on both leucocytes and epithelial cells. Imiquimod and poly I:C induced a weak MHC class I up-regulation in the epithelium but not in the lamina propria. Neither treatment had any profound effect on expression of MHC class II on epithelial cells but poly I:C and to a lesser extent CpG-ODN, up-regulated MHC class II staining intensity which, in the case of CpG-ODN, treatment, was associated with a strong accumulation of CD11c-positive dendritic cells. All three treatments induced an early (8h) but transient IP-10 response. Imiquimod and CpG-ODN, but not poly I:C induced an early MIP-1alpha response which remained for at least 7 days in CpG-ODN-treated animals but not in imiquimod-treated mice. Poly I:C and CpG-ODN, but not imiquimod, induced significant levels of RANTES at different time-points post-treatment. None of the treatments induced any significant changes in the levels of fractalkine, I-TAC or IFN-alpha. These studies have implications for the manipulation of the genital immune response and also improving the outcome of vaginal immunotherapy.

Immunological and pathological responses in BALB/c mice induced by genetic administration of Tc 13 Tul antigen of Trypanosoma cruzi

Tc13 is a trans-sialidase family protein of Trypanosoma cruzi, the aetiological agent of Chagas' disease. Recently, in vitro studies had suggested that Tc13 might participate in the pathogenesis of the disease. In order to study the role of Tc13 antigens in an in vivo model, we administered plasmid DNA encoding a Tc13 antigen from the Tulahuén strain (Tc13 Tul) to BALB/c mice and evaluated the immunological and pathological manifestations as well as the capacity of this antigen to confer protection against T. cruzi infection. Tc13 Tul immunization did not elicit a detectable humoral immune response but induced specific memory T-cells with no capacity to produce IFN-gamma. Five months after DNA-immunization with Tc13 Tul, signs of hepatotoxicity and reactive changes in the heart, liver and spleen were observed in 40-80% of mice. When Tc13 Tul DNA-immunized animals were challenged with trypomastigotes, a significant decrease in parasitaemia in early and late acute phase was observed without modification in the survival rate. Surprisingly, Tc13 Tul-immunized mice chronically infected with T. cruzi showed a decrease in the severity of heart damage. We conclude that, in BALB/c mice, genetic immunization with Tc13 Tul mainly induces immune responses associated with pathology.

Reducing the immunostimulatory activity of CpG-containing plasmid DNA vectors for non-viral gene therapy

The mammalian innate immune system has the ability to recognise and direct a response against incoming foreign DNA. The primary signal that triggers this response is unmethylated CpG motifs present in the DNA sequence of various disease-causing pathogens. These motifs are rare in vertebrate DNA, but abundant in bacterial and some viral DNAs. Because gene therapy generally involves the delivery of DNA from either plasmids of bacterial origin or recombinant viruses, an acute inflammatory response of variable severity inevitably results. The response is most serious for non-viral gene delivery vectors composed of cationic lipid-DNA complexes, producing adverse effects at lower doses and lethality at higher doses of complex. This review examines the role of immunostimulatory CpG motifs in the acute inflammatory response to non-viral gene therapy vectors. Strategies to neutralise or eliminate CpG motifs within plasmid DNA vectors, and the existing limitations of CpG reduction on improving the safety profile of non-viral vectors, will be discussed.

Immunobiology of muscle: advances in understanding an immunological microenvironment

Skeletal muscle, which is the largest cellular compartment of the body, lacks detectable MHC expression under physiological conditions. Therefore, immune reactions triggered by, or directed against, muscle cells proceed along specific pathways. Recently, the expression and functioning of classical MHC, non-classical MHC, adhesion and co-stimulatory molecules have been shown to support the concept that muscle cells can act as facultative antigen-presenting cells and should be considered as active participants, rather than passive targets, of immune reactions. Here, we summarize current knowledge on the immunological capabilities of skeletal muscle cells and discuss how these characteristics might contribute to inflammatory muscle disorders, as well as therapeutic strategies, such as gene or myoblast transfer.

Pseudovirion particle production by live poxvirus human immunodeficiency virus vaccine vector enhances humoral and cellular immune responses

Live-vector-based human immunodeficiency virus (HIV) vaccines are an integral part of a number of HIV vaccine regimens currently under evaluation. Live vectors that carry an intact gag gene are capable of eliciting HIV pseudovirion particle formation from infected host cells. The impact of pseudovirion particle formation on the immune response generated by live HIV vaccine vectors has not been established. In this study, a canarypox HIV vaccine candidate vector expressing HIV gag and env genes, vCP205, was modified by the introduction of a glycine-to-alanine coding change in the N-terminal myristylation site of gag to create Myr- vCP205. This substitution effectively eliminated particle formation without altering the level of protein production. vCP205 and Myr- vCP205 were then directly compared for the ability to induce HIV-specific immune responses in mice. The particle-competent vector vCP205 elicited higher levels of CD8+ T-cell responses, as indicated by gamma interferon enzyme-linked immunospot (ELISPOT) assay and intracellular cytokine staining. Humoral responses to Gag and Env were also markedly higher from animals immunized with the particle-competent vector. Furthermore, HIV-specific CD4+ T-cell responses were greater among animals immunized with the particle-competent vector. Using a human dendritic cell model of antigen presentation in vitro, vCP205 generated greater ELISPOT responses than Myr- vCP205. These results demonstrate that pseudovirion particle production by live-vector HIV vaccines enhances HIV-specific cellular and humoral immune responses.

DNA vaccines coding for heat-shock proteins (HSPs): tools for the activation of HSP-specific regulatory T cells

Heat-shock proteins (HSPs) perform opposing functions in autoimmune arthritis. HSP-specific T cells drive the progression of adjuvant arthritis (AA), an experimental model of autoimmune arthritis. However, HSP-specific T cells can also have a regulatory phenotype, controlling arthritogenic T cells and inhibiting AA progression. This manuscript reviews the use of DNA vaccines coding for HSPs to analyse the role of these proteins in the regulation of arthritis. Recent studies suggest that HSPs participate in the control of pathological autoimmunity. Indeed, DNA vaccines coding for HSPs can be used to activate these HSP-specific built-in regulatory mechanisms. Thus, DNA vaccines coding for HSPs may serve not only as tools for the dissection of immunoregulatory mechanisms, but also as agents for the treatment of autoimmune disorders.

Cytokines and chemokines are expressed at different levels in small and large murine colon-26 tumors following intratumoral injections of CpG ODN

Direct tumor injections of (CpG ODN) into murine colon tumor 26 (CT-26) tumors can induce a potent antitumor response. Tumor size at the beginning of treatment determines the final therapeutic outcome, with smaller tumors responding favorably to CpG ODN therapy whereas large tumors do not. CpG ODN injections in small tumors resulted in tumor necrosis and extensive inflammatory cell infiltration, with average survival that is significantly higher (48.1 +/- 34 days) when compared to control ODN-treated mice (16.1 +/- 3.5 days). Cytokines and chemokines are expressed at different levels in small and large CT-26 tumors following intratumoral injections of CpG ODN. We observed that granulocyte-macrophage colony-stimulating factor and interleukin (IL) 6 are the major cytokines that were overexpressed in CpG ODN-treated small tumors but not in large tumors. Similarly, several chemokines (CXCL1, CCL2, and CCL3) were also significantly higher in CpG ODN-treated small tumors compared to control ODN-treated tumors.

Cellular and molecular studies of B cells exhibiting reverse somatic mutation throughout life

Somatic mutation of immunoglobulin (Ig) genes plays an important role in generating antibody diversity. The frequency of somatic mutation appears to vary throughout life. However, this process has been difficult to study in vivo because the DNA in and around rearranged V genes undergoes random mutation, causing silent or replacement mutations. Therefore, we have developed a transgenic mouse model for studying the frequency of B cells exhibiting mutation in young and old mice. The system is based on a reporter transgene (HuG-X) that encodes a chimeric Ig heavy chain composed of a murine VDJ segment and a human IgG1 constant region. The VDJ has been mutated to contain a TAG stop codon in the D segment. Therefore, the transgene is transcribed but not translated. Point mutation of the stop codon results in expression of the chimeric H chain, which is readily detected as human IgG1 expression. In vivo, we found that the transgene undergoes spontaneous reverse somatic mutation at a low frequency. Treatment of HuG-X mice with anti-IgD greatly increases the frequency of somatic mutation. The observed mutation frequency in anti-IgD-treated mice increases with age until adulthood, then plateaux and finally declines in aged mice. The mutations in the stop codon were associated with increased double-stranded DNA breaks (DSB) within and around the TAG site. Our results demonstrate that the rate of frequency of spontaneous reverse mutation is very low in vivo, yet it is significantly increased after stimulation with anti-IgD antibodies. The frequency of point mutation is age dependent and correlates with increased DSB.

Different sources of ?help? facilitate the antibody response to hepatitis D virus ? antigen

Repeated injections of hepatitis D antigen (HDAg) delivered either as a recombinant protein, or expressed from a DNA vaccine elicited no (or only very low) antibody responses in inbred mouse strains. Codelivery of oligonucleotides (ODN) with immune-stimulating sequences (ISS) with the protein antigen, or ISS in DNA vaccines (encoding HDAg) did not overcome the low intrinsic immunogenicity of this small viral antigen for B cells. In contrast, codelivery of immunogenic, heterologous proteins (either mixed to recombinant HDAg as recombinant proteins, or fused to HDAg sequences as chimeric antigens expressed from DNA vaccines) provided specific, CD4+ T cell-dependent "help" that supported efficient priming of antibody responses to HDAg. Chimeric proteins in which selected HDAg fragments were fused in frame with immunogenic, heterologous protein fragments produced by DNA vaccines allowed the mapping of antibody-binding HDAg domains of the viral antigen. The described approach thus facilitates induction of serum antibody responses against native viral antigens with low immunogenicity for B cells.

Nonviral DNA vectors for immunization and therapy: design and methods for their obtention

The use of plasmid DNA for vaccination and therapy is a relatively novel technology, with advantages and limitations as with other gene transfer techniques. The technology is based on DNA vectors designed for administering genes coding for relevant proteins into a given organism, fulfilling requirements of the regulatory agencies that once properly formulated and delivered the desired vaccine/therapeutic effect can be achieved. Starting from conventional plasmid DNA vectors currently tested in clinical trials, improvement resulted in bacterial element-less vectors, increasing the complexity of the developmental process. The present review focuses on systems described for generating these nonviral DNA vectors for immunization and therapy from bacterial hosts (conventional and conditionally replicating plasmids, nonreplicating minicircles, and linear dumbbell-shaped expression cassettes) in vivo or in vitro. Additionally, nontherapeutic genetic sequences with a negative or positive effect according to the specific application are described, bringing a better comprehension of the technology's state of the art.

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

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

Toll-like receptor ligand links innate and adaptive immune responses by the production of heat-shock proteins

The report shows that CpG can exert additional adjuvant effects by inducing cells that are normally inferior antigen (Ag)-presenting cells to participate in immune induction by cross-priming. Macrophages (Mphi) exposed to protein Ag in the presence of bioactive CpG DNA released material that induced primary CD8(+) T cell responses in DC-naïve T cell cultures. This cross-priming event was accompanied by up-regulation of the stress protein response as well as inflammatory cytokine expression in treated Mphi. The material released was indicated to contain inducible heat shock protein-70 and epitope peptide, which in turn, were presented by dendritic cells (DCs) to responder T cells. Such an adjuvant effect by CpG may serve to salvage immunogenic material from otherwise inert depot cellular sites and additionally stimulate DCs to effectively cross-prime. The cross-priming, shown also to occur in vivo, may be particularly useful when Ag doses are low and have minimal opportunity for delivery to DCs for consequent direct priming.

The generation of monoclonal antibodies by genetic immunisation: antibodies against trout TCRalpha and IgL isotypes

Production of monoclonal antibodies (mAb) using genetic immunisation is a potential alternative when purified antigen is difficult to obtain, or when induction of an antibody response to a limited part of an antigen is wanted. DNA immunisation using only the constant parts of trout immunoglobulin light chains coding regions was attempted here, because mAbs against the variable (V) part of immunoglobulins do not recognise the whole repertoire of the isotype. After positive results with the light chains and establishing of a proper screening system (ELISA), generation of monoclonal antibodies against trout T cell receptor was also performed. The DNA constructs were used both for immunisation of mice and for protein expression in EBNA 293 cells. Mice were immunised with the constructs 3-5 times by intramuscular injection, with or without adjuvants during 1-3 months. Spleens of positive mice were fused with myeloma Sp2/0 cells and clones were screened by ELISA using double-screening (recombinant protein/trout cells).MAbs 46E5 (anti-IgL2C), 4F2 (anti-TCRalpha), 18B3 (anti-TCRalphaC) and 4E5 (anti-TCRalphaC) show specific binding to its antigen in Western blot, mAb 18B3 and 7H7(anti-TCRalpha) shows specific staining of trout splenocytes in flow cytometry and mAb 7H7 induces proliferation of trout peripheral blood leucocytes (PBL) in vitro.

Technological advances to increase immunogenicity of DNA vaccines

The latest clinical data obtained with DNA vaccines against HIV and malaria have shown promise, but it is clear that when DNA vaccines are compared with other vaccine vector delivery systems, there is still room for improvement. Further development is more than possible, based on the wealth of information accumulating on methods and approaches to increase immunogenicity of DNA vaccines. Thus, the goal of this review is to summarize some of the latest technological advances to increase immunogenicity of DNA vaccines administered by the im. and id. routes. By means of examples, the review will be intended to focus only on recent developments reported in the last 2 years and likely to go towards the improvement of mucosal, humoral and cellular immune responses mostly against cancer and infectious disease antigens.

Influenza update: vaccine development and clinical trials

Although influenza activity throughout the world has been relatively low during the past year, epidemics of influenza A, in particular, which are caused by new virus variants, continue to be a major public health problem. Widespread vaccination is the only rational measure that can be used for the prevention of illness in key risk groups. Although current inactivated split/subunit vaccines are reasonably effective, significant improvements have been shown to be possible in the boosting of responses by the use of particular adjuvants and/or the direct administration of vaccines to the respiratory tract. Live attenuated vaccines, also administered directly to the respiratory tract, have continued to be shown to be safe and effective, and, in the longer term, probably will have a major role in influenza prophylaxis, especially in children and young adults.

Induction of immune response in BALB/c mice with a DNA vaccine encoding bacterioferritin or P39 of Brucella spp

In this study, we evaluated the ability of DNA vaccines encoding the bacterioferritin (BFR) or P39 proteins of Brucella spp. to induce cellular and humoral immune responses and to protect BALB/c mice against a challenge with B. abortus 544. We constructed eukaryotic expression vectors called pCIBFR and pCIP39, encoding BFR or P39 antigens, respectively, and we verified that these proteins were produced after transfection of COS-7 cells. PCIBFR or pCIP39 was injected intramuscularly three times, at 3-week intervals. pCIP39 induced higher antibody responses than did the DNA vector encoding BFR. Both vectors elicited a T-cell-proliferative response and also induced a strong gamma interferon production upon restimulation with either the specific antigens or Brucella extract. In this report, we also demonstrate that animals immunized with these plasmids elicited a strong and long-lived memory immune response which persisted at least 3 months after the third vaccination. Furthermore, pCIBFR and pCIP39 induced a typical T-helper 1-dominated immune response in mice, as determined by cytokine or immunoglobulin G isotype analysis. The pCIP39 delivered by intramuscular injection (but not the pCIBFR or control vectors) induced a moderate protection in BALB/c mice challenged with B. abortus 544 compared to that observed in positive control mice vaccinated with S19.