Therapeutic effect of DNA vaccines combined with chemotherapy in a latent infection model after aerosol infection of mice with Mycobacterium tuberculosis

Extracellular nucleoprotein exacerbates influenza virus pathogenesis by activating Toll-like receptor 4 and the NLRP3 inflammasome

Host immune responses, such as those initiated by pattern recognition receptor (PRR) activation, are important for viral clearance and pathogenesis. However, little is known about the interactions of viral proteins with surface PRRs or, more importantly, the association of innate immune activation with viral pathogenesis. In this study, we showed that internal influenza virus proteins were released from infected cells. Among these proteins, nucleoprotein (NP) played a critical role in viral pathogenesis by stimulating neighboring cells through toll-like receptor (TLR)2, TLR4, and the NLR family pyrin domain containing 3 (NLRP3) inflammasome. Through the activation of these PRRs, NP induced the production of interleukin (IL)-1β and IL-6, which subsequently led to the induction of trypsin. Trypsin induced by NP increased the infectivity of influenza virus, leading to increases in viral replication and pathology upon subsequent viral infection. These results reveal the role of released NP in influenza pathogenesis and highlight the importance of the interactions of internal viral proteins with PRRs in the extracellular compartment during viral pathogenesis.

Therapeutic Effect of Subunit Vaccine AEC/BC02 on Mycobacterium tuberculosis Post-Chemotherapy Relapse Using a Latent Infection Murine Model

Tuberculosis (TB), caused by the human pathogen Mycobacterium tuberculosis (Mtb), is an infectious disease that presents a major threat to human health. Bacillus Calmette-Guérin (BCG), the only licensed TB vaccine, is ineffective against latent TB infection, necessitating the development of further TB drugs or therapeutic vaccines. Herein, we evaluated the therapeutic effect of a novel subunit vaccine AEC/BC02 after chemotherapy in a spontaneous Mtb relapse model. Immunotherapy followed 4 weeks of treatment with isoniazid and rifapentine, and bacterial loads in organs, pathological changes, and adaptive immune characteristics were investigated. The results showed slowly increased bacterial loads in the spleen and lungs of mice inoculated with AEC/BC02 with significantly lower loads than those of the control groups. Pathological scores for the liver, spleen, and lungs decreased accordingly. Moreover, AEC/BC02 induced antigen-specific IFN-γ-secreting or IL-2-secreting cellular immune responses, which decreased with the number of immunizations and times. Obvious Ag85b- and EC-specific IgG were observed in mice following the treatment with AEC/BC02, indicating a significant Th1-biased response. Taken together, these data suggest that AEC/BC02 immunotherapy post-chemotherapy may shorten future TB treatment.

Immunotherapeutic Role of NOD-2 and TLR-4 Signaling as an Adjunct to Antituberculosis Chemotherapy

Tuberculosis (TB) treatment is lengthy and inflicted with severe side-effects. Here, we attempted a novel strategy to reinforce host immunity through NOD-like receptor (NOD-2) and Toll-like receptor (TLR-4) signaling in the murine model of TB. Intriguingly, we noticed that it not only bolstered the immunity but also reduced the dose and duration of rifampicin and isoniazid therapy. Further, we observed expansion in the pool of effector (CD44^hi, CD62L^lo, CD127^hi) and central (CD44^hi, CD62L^hi, CD127^hi) memory CD4 T cells and CD8 T cells and increased the intracellular killing of Mycobacterium tuberculosis (Mtb) by activated dendritic cells [CD86^hi, CD40^hi, IL-6^hi, IL-12^hi, TNF-α^hi, nitric oxide (NO)^hi] with significant reduction in Mtb load in the lungs and spleen of infected animals. We infer that the signaling through NOD-2 and TLR-4 may be an important approach to reduce the dose and duration of the drugs to treat TB.

Enhancement of CD4+ T Cell Function as a Strategy for Improving Antibiotic Therapy Efficacy in Tuberculosis: Does It Work?

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) remains a major public health problem worldwide due in part to the lack of an effective vaccine and to the lengthy course of antibiotic treatment required for successful cure. Combined immuno/chemotherapeutic intervention represents a major strategy for developing more effective therapies against this important pathogen. Because of the major role of CD4⁺ T cells in containing Mtb infection, augmentation of bacterial specific CD4⁺ T cell responses has been considered as an approach in achieving this aim. Here we present new data from our own research aimed at determining whether boosting CD4⁺ T cell responses can promote antibiotic clearance. In these studies, we first characterized the impact of antibiotic treatment of infected mice on Th1 responses to major Mtb antigens and then performed experiments aimed at sustaining CD4⁺ T cell responsiveness during antibiotic treatment. These included IL-12 infusion, immunization with ESAT-6 and Ag85B immunodominant peptides and adoptive transfer of Th1-polarized CD4⁺ T cells specific for ESAT-6 or Ag85B during the initial month of chemotherapy. These approaches failed to enhance antibiotic clearance of Mtb, indicating that boosting Th1 responses to immunogenic Mtb antigens highly expressed by actively dividing bacteria is not an effective strategy to be used in the initial phase of antibiotic treatment, perhaps because replicating organisms are the first to be eliminated by the drugs. These results are discussed in the context of previously published findings addressing this concept along with possible alternate approaches for harnessing Th1 immunity as an adjunct to chemotherapy.

Tuberculosis vaccination needs to avoid 'decoy' immune reactions

Current search for a new effective vaccine against tuberculosis involves selected antigens, vectors and adjuvants. These are being evaluated usually by their booster inoculation following priming with Bacillus Calmette-Guerin. The purpose of this article is to point out, that despite being attenuated of virulence, priming with BCG may still involve immune mechanisms, which are not favourable for protection against active disease. It is postulated, that the responsible 'decoy' constituents selected during the evolution of pathogenic tubercle bacilli may be involved in the evasion from bactericidal host resistance and stimulate immune responses of a cytokine phenotype, which lead to the transition from latent closed granulomas to reactivation with infectious lung cavities. The decoy mechanisms appear as favourable for most infected subjects but leading in a minority of cases to pathology which can effectively transmit the infection. It is proposed that construction and development of new vaccine candidates could benefit from avoiding decoy-type immune mechanisms.

Recent progress in the design of DNA vaccines against tuberculosis

Current tuberculosis (TB) vaccines have some disadvantages and many efforts have been undertaken to produce effective TB vaccines. As a result of their advantages, DNA vaccines are promising future vaccine candidates. This review focuses on the design and delivery of novel DNA-based vaccines against TB.

The effect of adjuvants and delivery systems on Th1, Th2, Th17 and Treg cytokine responses in mice immunized with Mycobacterium tuberculosis-specific proteins

Tuberculosis (TB) is a major health problem of global concern. The control of this disease requires appropriate preventive measures, including vaccines. In TB, T helper (Th)1 cytokines provide protection whereas Th2 and T regulatory (Treg) cytokines contribute to the pathogenesis and Th17 cytokines play a role in both protection and pathogenesis. Previous studies with Mycobacterium tuberculosis-specific proteins have identified seven low molecular weight proteins, PE35, ESXA, ESXB, Rv2346c, Rv2347c, Rv3619c, and Rv3620c, as immunodominant antigens inducing Th1-cell responses in humans following natural infection with M. tuberculosis. The aim of this study was to characterize the cytokine responses induced in mice immunized with these proteins, using various adjuvants and delivery systems, i.e. chemical adjuvants (Alum and IFA), non-pathogenic mycobacteria (M. smegmatis and M. vaccae) and a DNA vaccine plasmid (pUMVC6). The immune responses were monitored by quantifying the marker cytokines secreted by Th1 (IFN-ɣ), Th2 (IL-5), Treg (IL-10), and Th17 (IL-17A) cells. DNA corresponding to pe35, esxa, esxb, rv2346c, rv2347c, rv3619c, and rv3620c genes were cloned into the expression vectors pGES-TH-1, pDE22 and pUMVC6 for expression in Escherichia coli, mycobacteria and eukaryotic cells, respectively. Mice were immunized with the recombinants using different adjuvants and delivery systems, and spleen cells were stimulated in vitro with peptides of immunizing proteins to investigate antigen-specific secretion of Th1 (IFN-ɣ), Th2 (IL-5), Treg (IL-10), and Th17 (IL-17A) cytokines. The results showed that spleen cells, from mice immunized with all antigens, secreted the protective Th1 cytokine IFN-ɣ, except ESXB, with one or more adjuvants and delivery systems. However, only Rv3619c consistently induced Th1-biased responses, without the secretion of significant concentrations of Th2, Th17 and Treg cytokines, with all adjuvants and delivery systems. Rv3619c also induced antigen-specific IgG antibodies in immunized mice.

Immunotherapeutic effects of Mycobacterium tuberculosis rv3407 DNA vaccine in mice

Tuberculosis (TB) is a major global public health problem. Latent TB infection (LTBI) is a major source of active TB. New vaccines to treat LTBI are urgently demanded. In this study, the gene encoding latency-associated antigen Rv3407 of Mycobacterium tuberculosis (MTB) rv3407 DNA vaccine was used to prepare and the immunogenicity and therapeutic effects were evaluated. Normal mice were immunized intramuscularly three times at two-week intervals with sterile water for injection, plasmid vector pVAX1, M. vaccae vaccine, ag85a DNA or rv3407 DNA. TB-infected mice were immunized intramuscularly three times at two-week intervals with phosphate-buffered saline (PBS) and rv3407 DNA. The normal mice immunized with rv3407 DNA or ag85a DNA showed higher levels of interferon-gamma (IFN-γ) in stimulated spleen lymphocyte culture supernatants, and had more Th1 cells and an elevated ratio of Th1/Th2 immune cells in whole blood, indicating that a Th1-type immune response was predominant. The levels of anti-Ag85A or anti-Rv3407 IgG antibody were significantly increased in the ag85a DNA and rv3407 DNA groups compared to the sterile water for injection, vector, and M. vaccae groups (p < .0001). Compared with the PBS group, the rv3407 DNA group had pulmonary bacterial loads that were lower by 0.56 log₁₀ (p < .01)_. The mice vaccinated with rv3407 DNA developed antigen-specific cellular and humoral responses. The rv3407 DNA is a potential DNA vaccine candidate against TB.

Unique Chemokine Profiles of Lung Tissues Distinguish Post-chemotherapeutic Persistent and Chronic Tuberculosis in a Mouse Model

There is a substantial need for biomarkers to distinguish latent stage from active Mycobacterium tuberculosis infections, for predicting disease progression. To induce the reactivation of tuberculosis, we present a new experimental animal model modified based on the previous model established by our group. In the new model, the reactivation of tuberculosis is induced without administration of immunosuppressive agents, which might disturb immune responses. To identify the immunological status of the persistent and chronic stages, we analyzed immunological genes in lung tissues from mice infected with M. tuberculosis. Gene expression was screened using cDNA microarray analysis and confirmed by quantitative RT-PCR. Based on the cDNA microarray results, 11 candidate cytokines genes, which were obviously up-regulated during the chronic stage compared with those during the persistent stage, were selected and clustered into three groups: (1) chemokine genes, except those of monocyte chemoattractant proteins (MCPs; CXCL9, CXCL10, CXCL11, CCL5, CCL19); (2) MCP genes (CCL2, CCL7, CCL8, CCL12); and (3) TNF and IFN-γ genes. Results from the cDNA microarray and quantitative RT-PCR analyses revealed that the mRNA expression of the selected cytokine genes was significantly higher in lung tissues of the chronic stage than of the persistent stage. Three chemokines (CCL5, CCL19, and CXCL9) and three MCPs (CCL7, CCL2, and CCL12) were noticeably increased in the chronic stage compared with the persistent stage by cDNA microarray (p < 0.01, except CCL12) or RT-PCR (p < 0.01). Therefore, these six significantly increased cytokines in lung tissue from the mouse tuberculosis model might be candidates for biomarkers to distinguish the two disease stages. This information can be combined with already reported potential biomarkers to construct a network of more efficient tuberculosis markers.

Immunogenicity and therapeutic effects of a Mycobacterium tuberculosis rv2190c DNA vaccine in mice

Background

Tuberculosis (TB) is a major global public health problem. New treatment methods on TB are urgently demanded. In this study, Mycobacterium tuberculosis (MTB) rv2190c DNA vaccine was prepared and its immunogenicity and therapeutic effects were evaluated.

Results

Non-infected mice immunized with rv2190c DNA or ag85a DNA showed higher levels of interferon-gamma (IFN-γ) in stimulated spleen lymphocyte culture supernatants, and had more Th1 cells and an elevatory ratio of Th1/Th2 immune cells in whole blood, indicating that Th1-type immune response was predominant. Compared with the saline group, ag85a DNA group and rv2190c DNA group in the infected mice decreased the lung colony-forming units (CFUs) by 0.533 and 0.283 log₁₀, and spleen CFUs by 0.425 and 0.321 log₁₀ respectively, and pathological lesion.

Conclusions

The rv2190c DNA had some immunotherapeutic effect on TB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0196-x) contains supplementary material, which is available to authorized users.

Ag85A/ESAT-6 chimeric DNA vaccine induces an adverse response in tuberculosis-infected mice

The Mycobacterium tuberculosis (M. tb) antigens encoded by the 6 kDa early secretory antigenic target (esat-6) and antigen 85A (ag85a) genes are known to exert protective effects against tuberculosis in animal models. In addition, these antigens represent vaccine components that were tested in early human clinical trials. In the present study, a chimeric DNA vaccine was constructed that contained two copies of the esat-6 gene inserted into the ag85a gene from M. tb. BALB/c mice were treated with this chimeric vaccine following infection with either M. tb H37Rv or a clinical multi drug resistant tuberculosis isolate. Treatment of both groups of mice with the chimeric vaccine resulted in accelerated mortality. These findings are in contrast with previous results, which indicated that DNA vaccines expressing the individual antigens were either beneficial or at least not harmful. The results of the present study suggested that the ESAT-6 antigen is not suitable for inclusion in therapeutic vaccines.

Prophylactic Use of Ganoderma lucidum Extract May Inhibit Mycobacterium tuberculosis Replication in a New Mouse Model of Spontaneous Latent Tuberculosis Infection

A mouse model of spontaneous latent tuberculosis infection (LTBI) that mimics LTBI in humans is valuable for drug/vaccine development and the study of tuberculosis. However, most LTBI mouse models require interventions, and a spontaneous LTBI mouse model with a low bacterial load is difficult to establish. In this study, mice were IV-inoculated with 100 CFU Mycobacterium tuberculosis H37Rv, and a persistent LTBI was established with low bacterial loads (0.5~1.5log₁₀ CFU in the lung; < 4log₁₀ CFU in the spleen). Histopathological changes in the lung and spleen were mild during the first 20 weeks post-inoculation. The model was used to demonstrate the comparative effects of prophylactic and therapeutic administration of Ganoderma lucidum extract (spores and spores lipid) in preventing H37Rv replication in both lung and spleen. H37Rv was inhibited with prophylactic use of G. lucidum extract relative to that of the untreated control and therapy groups, and observed in the spleen and lung as early as post-inoculation week 3 and week 5 respectively. H37Rv infection in the therapy group was comparable to that of the untreated control mice. No significant mitigation of pathological changes was observed in either the prophylactic or therapeutic group. Our results suggest that this new LTBI mouse model is an efficient tool of testing anti-tuberculosis drug, the use of G. lucidum extract prior to M. tuberculosis infection may protect the host against bacterial replication to some extent.

A lentiviral vector-based therapeutic vaccine encoding Ag85B-Rv3425 potently increases resistance to acute tuberculosis infection in mice

Few treatment options for multidrug-resistant tuberculosis (TB) and extensively drug-resistant TB call attention to the development of novel therapeutic approaches for TB. Therapeutic vaccines are promising candidates because they can induce antigen-specific cellular immune responses, which play an important role in the elimination of Mycobacterium tuberculosis (MTB). In this study, a novel lentiviral vector therapeutic vaccine for delivering MTB-specific fusion protein Ag85B-Rv3425 was constructed. Results showed that one single-injection of this recombinant lentivirus vaccine could trigger antigen-specific Th1-type immune responses in mice. More importantly, mice with acute infection benefited a lot from a single-dose administration of this vaccine by markedly reduced MTB burdens in lungs and spleens as well as attenuated lesions in lungs compared with untreated mice. These results displayed good prospects of this novel vaccine for the immunotherapy of TB.

Transcriptome profiles associated to VHSV infection or DNA vaccination in turbot (Scophthalmus maximus)

DNA vaccines encoding the viral G glycoprotein show the most successful protection capability against fish rhabdoviruses. Nowadays, the molecular mechanisms underlying the protective response remain still poorly understood. With the aim of shedding light on the protection conferred by the DNA vaccines based in the G glycoprotein of viral haemorrhagic septicaemia virus (VHSV) in turbot (Scophthalmus maximus) we have used a specific microarray highly enriched in antiviral sequences to carry out the transcriptomic study associated to VHSV DNA vaccination/infection. The differential gene expression pattern in response to empty plasmid (pMCV1.4) and DNA vaccine (pMCV1.4-G₈₆₀) intramuscular administration with regard to non-stimulated turbot was analyzed in head kidney at 8, 24 and 72 hours post-vaccination. Moreover, the effect of VHSV infection one month after immunization was also analyzed in vaccinated and non-vaccinated fish at the same time points. Genes implicated in the Toll-like receptor signalling pathway, IFN inducible/regulatory proteins, numerous sequences implicated in apoptosis and cytotoxic pathways, MHC class I antigens, as well as complement and coagulation cascades among others were analyzed in the different experimental groups. Fish receiving the pMCV1.4-G₈₆₀ vaccine showed transcriptomic patterns very different to the ones observed in pMCV1.4-injected turbot after 72 h. On the other hand, VHSV challenge in vaccinated and non-vaccinated turbot induced a highly different response at the transcriptome level, indicating a very relevant role of the acquired immunity in vaccinated fish able to alter the typical innate immune response profile observed in non-vaccinated individuals. This exhaustive transcriptome study will serve as a complete overview for a better understanding of the crosstalk between the innate and adaptive immune response in fish after viral infection/vaccination. Moreover, it provides interesting clues about molecules with a potential use as vaccine adjuvants, antiviral treatments or markers for vaccine efficiency monitoring.

Adjunctive immunotherapy with α-crystallin based DNA vaccination reduces Tuberculosis chemotherapy period in chronically infected mice

By employing modified Cornell model, we have evaluated the potential of adjunctive immunotherapy with DNA vaccines to shorten the tuberculosis chemotherapy period and reduce disease reactivation. We demonstrate that α-crystallin based DNA vaccine (DNAacr) significantly reduced the chemotherapy period from 12 weeks to 8 weeks when compared with the chemotherapy alone. Immunotherapy with SodA based DNA vaccine (DNAsod) reduced the pulmonary bacilli only as much as DNAvec. Both DNAacr and DNAsod, although significantly delayed the reactivation in comparison to the chemotherapy alone, this delay was associated with the immunostimulatory sequences present in the vector backbone and was not antigen specific. Both DNA vaccines resulted in the production of significantly higher number of T_EM cells than the chemotherapy alone, however, only in the case of DNAsod, this enhancement was significant over the DNAvec treatment. Overall, our findings emphasize the immunotherapeutic potential of DNAacr in shortening the duration of TB chemotherapy.

Immunotherapeutic potential of recombinant ESAT-6 protein in mouse model of experimental tuberculosis

Recent understanding of the pathogenesis of tuberculosis allows the possible application of immunotherapy for the treatment of tuberculosis. Therapies that would upregulate the host antimycobacterial immune response and/or attenuate T-cell suppressive and macrophage-deactivating cytokines may prove to be useful in the treatment of tuberculosis. ESAT6, 6-kDa early secreted antigenic target, is a potent protective antigen and is considered as major target for long-lived memory cells. In the present study the immunotherapeutic potential of ESAT-6 has been evaluated in mouse model of experimental tuberculosis. In the present study the ESAT-6 protein was cloned in Escherichia coli using pET23a(+) plasmid and purified by Ni(2+)-NTA chromatography. Further, the immunotherapeutic potential of the recombinant ESAT-6 (in terms of CFU enumeration in the target organs and histopathological analysis of lungs) was evaluated against experimental tuberculosis. The recombinant ESAT-6 with C-terminal histidine-tag and free N-terminus mimics the natural form of ESAT-6 has been successfully cloned and purified. The recombinant ESAT-6 protein adjuvanted with dimethyl dioctadecylammonium bromide (DDA) moderately reduced the bacterial load in the target organs of infected mice. Further, the formulation (ESAT-6-DDA) was able to act synergistically when given in combination with antituberculosis drugs. This recombinant ESAT-6 showed good immunotherapeutic potential against experimental tuberculosis and can be used as an adjunct to the conventional antituberculosis chemotherapy.

In vivo action of IL-27: reciprocal regulation of Th17 and Treg cells in collagen-induced arthritis

Interleukin (IL)-27 is a novel cytokine of the IL-6/IL-12 family that has been reported to be involved in the pathogenesis of autoimmune diseases and has a pivotal role as both a pro- and anti-inflammatory cytokine. We investigated the in vivo effects of IL-27 on arthritis severity in a murine collagen-induced arthritis (CIA) model and its mechanism of action regarding control of regulatory T (Tregs) and IL-17-producing T helper 17 (Th17) cells. IL-27-Fc-treated CIA mice showed a lower severity of arthritis. IL-17 expression in the spleens was significantly decreased in IL-27-Fc-treated CIA mice compared with that in the CIA model. The Th17 population was decreased in the spleens of IL-27-Fc-treated CIA mice, whereas the CD4⁺CD25⁺Foxp3⁺ Treg population increased. In vitro studies revealed that IL-27 inhibited IL-17 production in murine CD4⁺ T cells, and the effect was associated with retinoic acid-related orphan receptor γT and signal transducer and activator of transcription 3 inhibition. In contrast, fluorescein isothiocyanate-labeled forkhead box P3 (Foxp3) and IL-10 were profoundly augmented by IL-27 treatment. Regarding the suppressive capacity of Treg cells, the proportions of CTLA-4⁺ (cytotoxic T-lymphocyte antigen 4), PD-1⁺ (programmed cell death protein 1) and GITR⁺ (glucocorticoid-induced tumor necrosis factor receptor) Tregs increased in the spleens of IL-27-Fc-treated CIA mice. Furthermore, in vitro differentiated Treg cells with IL-27 exerted a more suppressive capacity on T-cell proliferation. We found that IL-27 acts as a reciprocal regulator of the Th17 and Treg populations in CD4⁺ cells isolated from healthy human peripheral blood mononuclear cells (PBMCs), as well as from humans with rheumatoid arthritis (RA) PBMCs. Our study suggests that IL-27 has the potential to ameliorate overwhelming inflammation in patients with RA through a reciprocal regulation of Th17 and Treg cells.

Interleukin-12 as a genetic adjuvant enhances hepatitis C virus NS3 DNA vaccine immunogenicity

Hepatitis C virus (HCV) chronic infection is a worldwide health problem, and numerous efforts have been invested to develop novel vaccines. An efficient vaccine requires broad immune response induction against viral proteins. To achieve this goal, we constructed a DNA vaccine expressing nonstructural 3 (NS3) gene (pcDNA3.1-HCV-NS3) and assessed the immune response in C57BL/6 mice. In this study, the NS3 gene was amplified with a nested-reverse transcriptase-polymerase chain reaction (RT-PCR) method using sera of HCV-infected patients with genotype 1a. The resulting NS3 gene was subcloned into a pcDNA3.1 eukaryotic expression vector, and gene expression was detected by western blot. The resultant DNA vaccine was co-administered with interleukin-12 (IL-12) as an adjuvant to female C57BL/6 mice. After the final immunizations, lymphocyte proliferation, cytotoxicity, and cytokine levels were assessed to measure immune responses. Our data suggest that co-administration of HCV NS3 DNA vaccine with IL-12 induces production of significant levels of both IL-4 and interferon (IFN)-γ (p<0.05). Cytotoxicity and lymphocyte proliferation responses of vaccinated mice were significantly increased compared to control (p<0.05). Collectively, our results demonstrated that co-administration of HCV NS3 and IL-12 displayed strong immunogenicity in a murine model.

Nonlytic Fc-fused IL-7 synergizes with Mtb32 DNA vaccine to enhance antigen-specific T cell responses in a therapeutic model of tuberculosis

Improvement to the immunogenicity of DNA vaccines was evaluated in a Mycobacterium tuberculosis (MTB) infection mouse model examining the combined effects of nonlytic Fc-fused IL-7 DNA (IL-7-nFc) and Flt3-ligand fused Mtb32 (F-Mtb32) DNA. Mice were treated with conventional chemotherapy for 6 weeks from 4 weeks after aerosol infection of MTB. Following the start of chemotherapy, DNA immunizations were administered five times with 2-week intervals. Coadministration of IL-7-nFc and F-Mtb32 DNA given during chemotherapy synergistically enhanced the magnitude of Mtb32-specific T cell responses and sustained for one-year after the last immunization assessed by IFN-γ ELISPOT assay. After dexamethasone treatment, a significantly reduced MTB reactivation was observed in mice received both IL-7-nFc and F-Mtb32 DNA, compared with F-MTb32 DNA alone or with control mice. In addition, mice treated with IL-7-nFc and F-Mtb32 DNA together showed improved lung pathology and reduced pulmonary inflammation values relative to F-Mtb32 DNA or saline injected mice. Intracellular cytokine staining revealed that the protection levels induced by combination therapy with IL-7-nFc and F-Mtb32 DNA was associated with enhanced Mtb32-specific IFN-γ secreting CD4(+) T cell responses and CD8(+) T cell responses stimulated with CTL epitope peptide in the lungs and spleens. These data suggest that IL-7-nFc as a novel TB adjuvant may facilitate therapeutic TB DNA vaccine to the clinics through significant enhancement of codelivered DNA vaccine-induced T cell immunity.

Interleukin-27 suppresses osteoclastogenesis via induction of interferon-γ

Interleukin (IL)-27 is a heterodimeric cytokine that is known to have both stimulatory and inhibitory functions during immune responses. We investigated the effects of IL-27 on arthritis and bone erosion in the murine collagen-induced arthritis (CIA) model. We demonstrate that the inhibitory effect of IL-27 on osteoclastogenesis is associated with interferon-γ (IFN-γ) production by using an IFN-γ knockout mouse model. The IL-27-Fc was injected into both CIA and IFN-γ-deficient mice. The effects of IL-27-Fc on osteoclast differentiation were evaluated both in vitro and in vivo. The IL-27-Fc-injected mice showed significantly lower arthritis indices and fewer tartrate-resistant acid-phosphatase-positive osteoclasts in their joint tissues than untreated mice. Interleukin-27 inhibited osteoclastogenesis from bone marrow-derived mononuclear cells in vitro, which was counteracted by the addition of anti-IFN-γ antibody. The IL-27-Fc did not affect arthritis in IFN-γ knockout mice. Interleukin-27 also suppressed osteoclast differentiation in human and intriguingly, it could promote the expression of IFN-γ on priming osteoclasts. These results imply that IL-27 suppressed the generation of CIA and osteoclastogenesis, which were mediated by the induction of IFN-γ.

Antigen-presenting cells transfected with Hsp65 messenger RNA fail to treat experimental tuberculosis

In the last several years, the use of dendritic cells has been studied as a therapeutic strategy against tumors. Dendritic cells can be pulsed with peptides or full-length protein, or they can be transfected with DNA or RNA. However, comparative studies suggest that transfecting dendritic cells with messenger RNA (mRNA) is superior to other antigen-loading techniques in generating immunocompetent dendritic cells. In the present study, we evaluated a new therapeutic strategy to fight tuberculosis using dendritic cells and macrophages transfected with Hsp65 mRNA. First, we demonstrated that antigen-presenting cells transfected with Hsp65 mRNA exhibit a higher level of expression of co-stimulatory molecules, suggesting that Hsp65 mRNA has immunostimulatory properties. We also demonstrated that spleen cells obtained from animals immunized with mock and Hsp65 mRNA-transfected dendritic cells were able to generate a mixed Th1/Th2 response with production not only of IFN-γ but also of IL-5 and IL-10. In contrast, cells recovered from mice immunized with Hsp65 mRNA-transfected macrophages were able to produce only IL-5. When mice were infected with Mycobacterium tuberculosis and treated with antigen-presenting cells transfected with Hsp65 mRNA (therapeutic immunization), we did not detect any decrease in the lung bacterial load or any preservation of the lung parenchyma, indicating the inability of transfected cells to confer curative effects against tuberculosis. In spite of the lack of therapeutic efficacy, this study reports for the first time the use of antigen-presenting cells transfected with mRNA in experimental tuberculosis.

Efficacy of Mycobacterium indicus pranii immunotherapy as an adjunct to chemotherapy for tuberculosis and underlying immune responses in the lung

BACKGROUND

The 9-month-long chemotherapy of tuberculosis often results in poor compliance and emergence of drug-resistant strains. So, improved therapeutic strategy is urgently needed. Immunotherapy could be beneficial for the effective management of the disease. Previously we showed the protective efficacy of Mycobacterium indicus pranii (MIP) when given as prophylactic vaccine in animal models of tuberculosis.

METHODS

We sought to investigate whether MIP can be used as an adjunct to the chemotherapy in guinea pig models of tuberculosis. Efficacy of MIP was evaluated when given subcutaneously or by aerosol.

RESULTS

MIP-therapy as an adjunct to the chemotherapy was found to be effective in accelerating bacterial killing and improving organ pathology. MIP-immunotherapy resulted in higher numbers of activated antigen-presenting cells and lymphocytes in the infected lungs and also modulated the granulomatous response. Early increase in protective Th1 immune response was observed in the immunotherapy group. Following subsequent doses of MIP, decrease in the inflammatory response and increase in the immunosuppressive response was observed, which resulted in the improvement of lung pathology.

CONCLUSION

MIP immunotherapy is a valuable adjunct to chemotherapy for tuberculosis. Aerosol route of immunotherapy can play a crucial role for inducing immediate local immune response in the lung.

Immunotherapy for TB

Mycobacterium tuberculosis was one of the first human pathogens to be identified as the cause of a specific disease – TB. TB was also one of the first specific diseases for which immunotherapy was attempted. In more than a century since, multiple different immunotherapies have been attempted, alongside vaccination and antibiotic treatment, with varying degrees of success. Despite this, TB remains a major worldwide health problem that causes nearly 2 million deaths annually and has infected an estimated 2 billion people. A major reason for this is that M. tuberculosis is an ancient human pathogen that has evolved complex strategies for persistence in the human host. It has thus been long understood that, to effectively control TB, we will need to address the ability of the pathogen to establish a persistent, latent infection in most infected individuals. This review discusses what is presently known about the interaction of M. tuberculosis with the immune system, and how this knowledge has been used to design immunotherapeutic strategies.

Attempted immunotherapy for Mycobacterium tuberculosis with viral and protein vaccines based on Ag85B-ESAT6 in a mouse model

The increasing threat of drug-resistant strains of Mycobacterium tuberculosis (M. tb) and co-infection with human immunodeficiency virus (HIV) has worsened the international public health crisis and challenged conventional chemotherapy. Therapeutic vaccines, which possess the capacity to stimulate the immune system and affect the disease progression, deserve reconsideration to aid chemotherapy. Vaccines based on Ag85B-ESAT6 fusion protein were tested as potential immunotherapeutic vaccines against ongoing intravenous infection in a mouse model. Therapeutic efficacy was evaluated by enumeration of bacilli in infected tissues and by histological examination of the lungs. Ag85B-ESAT6 with the adjuvant dimethyl dioctadecylammonium bromide (DDA) - monophosphoryl lipid A (MPL) did not reduce bacterial load, however induced a sharp weight loss and worsened pathology. Recombinant virus-based vaccines failed to protect mice against tuberculosis either. More efforts should be taken to search for protective candidates and elucidate the mechanism for immunotherapy.

Protective and therapeutic efficacy of Mycobacterium smegmatis expressing HBHA-hIL12 fusion protein against Mycobacterium tuberculosis in mice

Tuberculosis (TB) remains a major worldwide health problem. The only vaccine against TB, Mycobacterium bovis Bacille Calmette-Guerin (BCG), has demonstrated relatively low efficacy and does not provide satisfactory protection against the disease. More efficient vaccines and improved therapies are urgently needed to decrease the worldwide spread and burden of TB, and use of a viable, metabolizing mycobacteria vaccine may be a promising strategy against the disease. Here, we constructed a recombinant Mycobacterium smegmatis (rMS) strain expressing a fusion protein of heparin-binding hemagglutinin (HBHA) and human interleukin 12 (hIL-12). Immune responses induced by the rMS in mice and protection against Mycobacterium tuberculosis (MTB) were investigated. Administration of this novel rMS enhanced Th1-type cellular responses (IFN-γ and IL-2) in mice and reduced bacterial burden in lungs as well as that achieved by BCG vaccination. Meanwhile, the bacteria load in M. tuberculosis infected mice treated with the rMS vaccine also was significantly reduced. In conclusion, the rMS strain expressing the HBHA and human IL-12 fusion protein enhanced immunogencity by improving the Th1-type response against TB, and the protective effect was equivalent to that of the conventional BCG vaccine in mice. Furthermore, it could decrease bacterial load and alleviate histopathological damage in lungs of M. tuberculosis infected mice.

Co-immunization of plasmid DNA encoding IL-12 and IL-18 with Bacillus Calmette-Guérin vaccine against progressive tuberculosis

PURPOSE

Bacillus Calmette-Guérin (BCG) vaccine has widely been used to immunize against tuberculosis, but its protective efficacy is variable in adult pulmonary tuberculosis, while it is not efficiently protective against progressive infection of virulent Mycobacterium tuberculosis strains. In this study, the protective effects of plasmid DNA vaccine constructs encoding IL-12 or IL-18 with the BCG vaccine were evaluated against progressive infection of M. tuberculosis, using mouse aerosol challenge model.

MATERIALS AND METHODS

Plasmid DNA vaccine constructs encoding IL-12 or IL-18 were constructed and mice were immunized with the BCG vaccine or with IL-12 DNA or IL-18 DNA vaccine constructs together with the BCG vaccine.

RESULTS

The BCG vaccine induced high level of interferon gamma (IFN-γ) but co-immunization of IL-12 or IL-18 DNA vaccine constructs with the BCG vaccine induced significantly higher level of IFN-γ than a single BCG vaccine. The BCG vaccine was highly protective at early stage of M. tuberculosis infection, but its protective efficacy was reduced at later stage of infection. The co-immunization of IL-12 DNA vaccine constructs with the BCG vaccine was slightly more protective at early stage of infection and was significantly more protective at later stage infection than a single BCG vaccine.

CONCLUSION

Co-immunization of IL-12 DNA vaccine with the BCG vaccine induced more protective immunity and was more effective for protection against progressive infection of M. tuberculosis.

Mtb32 is a promising tuberculosis antigen for DNA vaccination in pre- and post-exposure mouse models

Identification of antigens that provide protective immunity via prophylactic and therapeutic vaccination against Mycobacterium tuberculosis is critical for the development of subunit vaccines for tuberculosis (TB). In this study, we performed a head-to-head comparison of seven well-known TB antigens delivered by DNA vaccine, and evaluated their respective immunogenicities and protective efficacies in pre- and post-exposure mouse models. All TB antigens were designed as a chimeric fusion with Flt3-L to enhance antigen-specific T-cell immunity upon vaccination. Prophylactic vaccination with the Flt3L (F)-Mtb32 DNA vaccine elicited significant protection in both the spleen and lungs against M. tuberculosis challenge, comparable to the Bacillus Calmette-Guerin vaccine. F-Ag85A and F-Mtb32 DNA vaccines, in combination with chemotherapy, reduced the bacterial burden to undetectable levels in the lungs of all mice infected with M. tuberculosis. These data collectively indicate that the F-Mtb32 DNA vaccine confers the most efficient protective immunity that suppresses bacterial growth in the active or latent status of M. tuberculosis.

A review of murine models of latent tuberculosis infection

The mechanisms of latency and the causes of reactivation of Mycobacterium tuberculosis remain poorly understood; an important reason for this gap in knowledge is the absence of a standardized animal model of latent tuberculosis infection (LTBI). A complete LTBI model should incorporate 2 aspects of LTBI: a persistent infection model with a low bacterial load and a latent infection model that is modified from the Cornell model. Many parameters must be carefully considered to establish an LTBI model, including the inoculating dose, the route of infection, the time interval between infection and the initiation of antibiotic therapy, and the genetic background of the host animal. The responsiveness of this mouse model of LTBI can be assessed through the integrated use of indices, including Karnofsky performance status, bacterial load in spleen and lungs, induced levels of interferon-gamma and tumour necrosis factor-alpha, expression of interleukin (IL)-10 and IL-4 in tissues, specific antigen load in organs, time required for hormone-induced TB relapse, expression level of dormancy genes, and CD4 T-cell count.

Immunotherapeutic role of Ag85B as an adjunct to antituberculous chemotherapy

BACKGROUND

Immunotherapy to enhance the efficiency of the immune response in tuberculosis patients and to eliminate the persisters could be an additional valuable strategy to complement anti-mycobacterial chemotherapy. This study was designed to assess the immunotherapeutic potential of Ag85B as an adjunct to chemotherapy and its effect against active and persister bacteria left after therapy in mouse model of tuberculosis.

METHODS

6-8 week old female Balb/c mice were infected with Mycobacterium tuberculosis and treated with chemotherapy or immunotherapy. Protective efficacy was measured in terms of bacterial counts in lungs and spleen. Immune correlates of protection in terms of Th1 and Th2 cytokines were measured by ELISA.

RESULTS

Therapeutic effect of Ag85B was found to be comparable to that of short term dosage of antituberculous drugs (ATDs). The therapeutic effect of ATDs was augmented by the simultaneous treatment with rAg85B and moreover therapy with this protein allowed us to reduce ATD dosage. This therapy was found to be effective even in case of drug persisters. The levels of antigen specific IFNγ and IL-12 were significantly increased after immunotherapy as compared to the basal levels; moreover antigen specific IL-4 levels were depressed on immunotherapy with Ag85B.

CONCLUSION

We demonstrated in this study that the new combination approach using immunotherapy and concurrent chemotherapy should offer several improvements over the existing regimens to treat tuberculosis. The therapeutic effect is associated not only with initiating a Th1 response but also with switching the insufficient Th2 immune status to the more protective Th1 response.

Comprehensive gene expression profiling in lungs of mice infected with Mycobacterium tuberculosis following DNAhsp65 immunotherapy

BACKGROUND

The continued increase in tuberculosis (TB) rates and the appearance of extremely resistant Mycobacterium tuberculosis strains (XDR-TB) worldwide are some of the great problems of public health. In this context, DNA immunotherapy has been proposed as an effective alternative that could circumvent the limitations of conventional drugs. Nonetheless, the molecular events underlying these therapeutic effects are poorly understood.

METHODS

We characterized the transcriptional signature of lungs from mice infected with M. tuberculosis and treated with heat shock protein 65 as a genetic vaccine (DNAhsp65) combining microarray and real-time polymerase chain reaction analysis. The gene expression data were correlated with the histopathological analysis of lungs.

RESULTS

The differential modulation of a high number of genes allowed us to distinguish DNAhsp65-treated from nontreated animals (saline and vector-injected mice). Functional analysis of this group of genes suggests that DNAhsp65 therapy could not only boost the T helper (Th)1 immune response, but also could inhibit Th2 cytokines and regulate the intensity of inflammation through fine tuning of gene expression of various genes, including those of interleukin-17, lymphotoxin A, tumour necrosis factor-alpha, interleukin-6, transforming growth factor-beta, inducible nitric oxide synthase and Foxp3. In addition, a large number of genes and expressed sequence tags previously unrelated to DNA-therapy were identified. All these findings were well correlated with the histopathological lesions presented in the lungs.

CONCLUSIONS

The effects of DNA therapy are reflected in gene expression modulation; therefore, the genes identified as differentially expressed could be considered as transcriptional biomarkers of DNAhsp65 immunotherapy against TB. The data have important implications for achieving a better understanding of gene-based therapies.

The treatment of mice infected with multi-drug-resistant Mycobacterium tuberculosis using DNA vaccines or in combination with rifampin

The problems of tuberculosis (TB) and its drug resistance are very severe in China. New therapeutic agents or regimens to treat multi-drug-resistant tuberculosis (MDR-TB) are urgently needed. In this study, the effects of Ag85A DNA or ESAT6/Ag85A chimeric DNA vaccines alone or in combination with rifampin (RFP) were studied for the treatment of mice with MDR-TB. Eighty female BALB/c mice infected with Mycobacterium tuberculosis clinical isolate HB361, which was resistant to high level of RFP, and low level of isoniazid (INH), were treated with the saline, plasmid vector pVAX1, RFP, HSP65 DNA, Ag85A DNA, Ag85A DNA combined with RFP, chimeric ESAT6/Ag85A DNA, chimeric ESAT6/Ag85A DNA combined with RFP, respectively. Different effects of DNA vaccines for the treatment of MDR-TB were demonstrated in this study. Compared with saline group, Ag85A DNA vaccine alone or Ag85A DNA in combination with rifampin group reduced the pulmonary and splenic bacterial loads by 0.58, 0.82 and 0.51, 0.69 logs, respectively. The pathological changes of lungs were also slight and the lesions were limited in comparison with that of the control mice in which the lesions were extensive and more necrotic changes were observed. Interestingly, the chimeric Ag85A/ESAT6 DNA vaccine showed the lower effect for the treatment of MDR-TB. Ag85A DNA vaccine played a main role for the treatment of TB and MDR-TB. We believe that this is the first report of the use of DNA vaccine in the treatment of MDR-TB, and that these data suggest that DNA vaccine was effective for the treatment of MDR-TB which might have the potential contribution for resolving this problem in developing countries.

Immunogenicity of a DNA prime and recombinant adenovirus boost regime significantly varies between rhesus macaques of Chinese and Indian origins

BACKGROUND

Due to an ever increasing shortage of rhesus macaques of Indian origin (InR) that have been generally used for preclinical AIDS vaccine trials in non-human primates, demand is rising for Chinese rhesus macaques (ChR). However, the immunogenicity of an AIDS vaccine candidate has not been compared in parallel in both rhesus macaque subspecies.

METHODS

ChR and InR were immunized with SIV/HIV DNA and adenovirus vaccine and their immune responses to SIV and HIV evaluated.

RESULTS

SIV Gag- and Env-specific T-cell responses and SIV-specific lymphoproliferative responses measured in ChR were significantly weaker than those in InR (P < 0.05). By contrast, antibody responses to SIV Env, Tat, and Nef in ChR were stronger than those in InR (P < 0.05).

CONCLUSIONS

Immunogenicity of an AIDS vaccine can vary significantly depending on the geographic origin implying genetic differences of macaques. This must be considered when describing and interpreting results of such vaccine studies.

Implications of partial immunity on the prospects for tuberculosis control by post-exposure interventions

One-third of the world population (approximately 2 billion individuals) is currently infected with Mycobacterium tuberculosis, the vast majority harboring a latent infection. As the risk of reactivation is around 10% in a lifetime, it follows that 200 million of these will eventually develop active pulmonary disease. Only therapeutic or post-exposure interventions can tame this vast reservoir of infection. Treatment of latent infections can reduce the risk of reactivation, and there is accumulating evidence that combination with post-exposure vaccines can reduce the risk of reinfection. Here we develop mathematical models to explore the potential of these post-exposure interventions to control tuberculosis on a global scale. Intensive programs targeting recent infections appear generally effective, but the benefit is potentially greater in intermediate prevalence scenarios. Extending these strategies to longer-term persistent infections appears more beneficial where prevalence is low. Finally, we consider that susceptibility to reinfection is altered by therapy, and explore its epidemiological consequences. When we assume that therapy reduces susceptibility to subsequent reinfection, catastrophic dynamics are observed. Thus, a bipolar outcome is obtained, where either small or large reductions in prevalence levels result, depending on the rate of detection and treatment of latent infections. By contrast, increased susceptibility after therapy may induce an increase in disease prevalence and does not lead to catastrophic dynamics. These potential outcomes are silent unless a widespread intervention is implemented.

Mycobacterium tuberculosis-specific CD8+ T cells and their role in immunity

There are more cases of tuberculosis in the world today than at any other time in history. The global epidemic has generated intense interest into the immunological mechanisms that control infection. Although CD4+ T cells play a critical role in host immunity to Mycobacterium tuberculosis, there is considerable interest in understanding the role of other T cell subsets in preventing disease development following infection. CD8+ T cells are required for optimum host defense following M. tuberculosis infection, which has led to investigation into how this protective effect is mediated. A critical review of recent literature regarding the role of CD8+ T cells in protective immunity to M. tuberculosis infection is now required to address the strengths and weaknesses of these studies. In this article, we evaluate the evidence that CD8+ T cells are critical in immunity to M. tuberculosis infection. We discuss the specific mycobacterial proteins that are recognized by CD8+ T cells elicited during infection. Finally, we examine the effector mechanisms of CD8+ T cells generated during infection and synthesize recent studies to consider the protective roles that these T cells serve in vivo.

Construction of recombinant attenuated Salmonella typhimurium DNA vaccine expressing H pylori ureB and IL-2

AIM: To construct a recombinant live attenuated Salm-onella typhimurium DNA vaccine encoding H pylori ureB gene and mouse IL-2 gene and to detect its immunogenicity in vitro and in vivo.

METHODS: H pylori ureB and mouse IL-2 gene fragments were amplified by polymerase chain reaction (PCR) and cloned into pUCmT vector. DNA sequence of the amplified ureB and IL-2 genes was assayed, then cloned into the eukaryotic expression vector pIRES through enzyme digestion and ligation reactions resulting in pIRES-ureB and pIRES-ureB-IL-2. The recombinant plasmids were used to transform competent E. coli DH5α, and the positive clones were screened by PCR and restriction enzyme digestion. Then, the recombinant pIRES-ureB and pIRES-ureB-IL-2 were used to transform LB5000 and the recombinant plasmids extracted from LB5000 were finally introduced into the final host SL7207. After that, recombinant strains were grown in vitro repeatedly. In order to detect the immunogenicity of the vaccine in vitro, pIRES-ureB and pIRES-ureB-IL-2 were transfected to COS-7 cells using Lipofectamine^TM2000, the immunogenicity of expressed UreB and IL-2 proteins was assayed with SDS-PAGE and Western blot. C57BL/6 mice were orally immunized with 1 × 10⁸ recombinant attenuated Salmonella typhimurium DNA vaccine. Four weeks after vaccination, mice were challenged with 1 × 10⁷ CFU of live H pylori SS1. Mice were sacrificed and the stomach was isolated for examination of H pylori 4 wk post-challenge.

RESULTS: The 1700 base pair ureB gene fragment amplified from the genomic DNA was consistent with the sequence of H pylori ureB by sequence analysis. The amplified 510 base pair fragment was consistent with the sequence of mouse IL-2 in gene bank. It was confirmed by PCR and restriction enzyme digestion that H pylori ureB and mouse IL-2 genes were inserted into the eukaryotic expression vector pIRES. The experiments in vitro showed that stable recombinant live attenuated Salmonella typhimurium DNA vaccine carrying ureB and IL-2 genes was successfully constructed and the specific strips of UreB and IL-2 expressed by recombinant plasmids were detected through Western blot. Study in vivo showed that the positive rate of rapid urease test of the immunized group including ureB and ureB-IL-2 was 37.5% and 12.5% respectively, and was significantly lower than that (100%) in the control group (P < 0.01).

CONCLUSION: Recombinant attenuated Salmonella typhimurium DNA vaccine expressing UreB protein and IL-2 protein with immunogenicity can be constructed. It can protect mice against H pylori infection, which may help the development of a human-use H pylori DNA vaccine.

Enhanced immunogenicity and protective efficacy with the use of interleukin-12-encapsulated microspheres plus AS01B in tuberculosis subunit vaccination

Tuberculosis subunit vaccines codelivered with interleukin-12 (IL-12)-encapsulated microspheres (IL-12EM) are designed for a sustained release of IL-12 and could induce strong Th1 immune responses specific to Ag85A and ESAT-6. The adjuvant combination of IL-12EM plus AS01B was a more efficient way to induce a sustained Th1 immunity and protection against Mycobacterium tuberculosis.

DNA vaccines for therapy of tuberculosis: Where are we now?

DNA vaccines that were being investigated in mice for prophylactic use against tuberculosis were soon found also to be surprisingly effective as treatment against established infection. The immune system was stimulated to kill the bacteria, even including the persistent latent bacteria that are otherwise refractory to the immune system and antibacterial chemotherapeutic drugs alike. Subsequent results from a range of laboratories using diverse DNA vaccines in diverse murine models of infection have been very varied, ranging from enhanced pathology, through negligible effects, to major additive benefit from combined vaccine and chemotherapy. This review summarises the data and assesses future prospects.

Mucosal immunotherapy of tuberculosis: is there a value in passive IgA?

Immunotherapeutic approaches, which have been considered for tuberculosis (TB), include immuno-potentiating or suppressing agents, cytokines, antibodies, DNA vaccines, non-pathogenic mycobacteria and mycobacterial extracts. While most or all of these potential agents showed at least some degree of promise in various experimental models, few progressed to clinical trials, yielding only moderately encouraging, though controversial results. Consequently, further research is required, as the need for an immunological agent, adjunct to chemotherapy, remains strongly justified. Its purpose is to shorten the currently protracted (6-9 months) drug treatment and thus increase compliance rates, which are most disappointing in areas with the highest disease prevalence. Using a mouse model of Mycobacterium tuberculosis (Mtb) infection, we recently reported, that an intranasally given monoclonal IgA antibody significantly reduced the bacterial load in the infected lungs, and that this protective effect of IgA could be further extended by co-inoculation with interferon gamma (IFNgamma). In this review, we describe the main features of IgA and its cellular receptors, the extent and possible mechanisms of passive vaccination with an IgA monoclonal antibody against the alpha-crystallin antigen of Mtb and discuss the potentials of this approach in the wider context of immunotherapy of TB.

Sustained E2 antibody response correlates with reduced peak viremia after hepatitis C virus infection in the chimpanzee

Immune correlates of protection against hepatitis C virus (HCV) infection are not well understood. Here we investigated 2 naive and 6 immunized chimpanzees before and after intravenous challenge, 12 weeks after the last immunization, with 100 50% chimpanzee infectious doses (CID(50)) of heterologous genotype 1b HCV. Vaccination with recombinant DNA and adenovirus vaccines expressing HCV core, E1E2, and NS3-5 genes induced long-term HCV-specific antibody and T-cell responses and reduced peak viral load about 100 times compared with controls (5.91 +/- 0.38 vs. 3.81 +/- 0.71 logs, respectively). There was a statistically significant inverse correlation between peak viral loads and envelope glycoprotein 2 (E2)-specific antibody responses at the time of challenge. Interestingly, one vaccinee that had sterilizing immunity against slightly heterologous virus generated the highest level of E2-specific total and neutralizing antibody responses as well as strong NS3/NS5-specific T-cell proliferative responses. The other four vaccinees with low levels of E2-specific antibody had about 44-fold reduced peak viral loads but eventually developed persistent infections. In conclusion, vaccine-induced E2-specific antibody plays an important role in prevention from nonhomologous virus infection and may provide new insight into the development of an effective HCV vaccine.