Evaluation of DNA vaccination with recombinant adenoviruses using bioluminescence imaging of antigen expression: impact of application routes and delivery with dendritic cells

Higher Potential Sensitization of Cow αS1-Casein over Goat αS1-Casein in a Mouse Model due to Enhanced Dendritic Cell Uptake and Activation

Cow's milk allergy is a common food allergy, with the milk protein αS1-casein being a major allergen. This study aimed to investigate differences in sensitization between cow and goat αS1-CN. Cow and goat αS1-CN were labeled with fluorescent dyes and given to mice sensitized with cholera toxin adjuvant. Both proteins reached immune organs, suggesting no major difference in digestion. However, compared with goat αS1-CN, cow αS1-CN is more readily taken up by dendritic cells, inducing dendritic cell maturation. Furthermore, cow αS1-CN can more effectively induce the generation of Th2 cells, leading to a higher production of specific IgE. In a Caco-2/RBL-2H3 cell model, cow αS1-CN caused more mast cell degranulation and loss of epithelial barrier integrity than goat αS1-CN. In summary, this study found differences in immune responses between cow and goat milk αS1-CN. Cow αS1-CN elicited stronger dendritic cell and Th2 responses, leading to increased mast cell degranulation.

Adenoviral vaccines promote protective tissue-resident memory T cell populations against cancer

BACKGROUND

Adenoviral vectors emerged as important platforms for cancer immunotherapy. Vaccination with adenoviral vectors is promising in this respect, however, their specific mechanisms of action are not fully understood. Here, we assessed the development and maintenance of vaccine-induced tumor-specific CD8+ T cells elicited upon immunization with adenoviral vectors.

METHODS

Adenoviral vaccine vectors encoding the full-length E7 protein from human papilloma virus (HPV) or the immunodominant epitope from E7 were generated, and mice were immunized intravenously with different quantities (107, 108 or 109 infectious units). The magnitude, kinetics and tumor protection capacity of the induced vaccine-specific T cell responses were evaluated.

RESULTS

The adenoviral vaccines elicited inflationary E7-specific memory CD8+ T cell responses in a dose-dependent manner. The magnitude of these vaccine-specific CD8+ T cells in the circulation related to the development of E7-specific CD8+ tissue-resident memory T (TRM) cells, which were maintained for months in multiple tissues after vaccination. The vaccine-specific CD8+ T cell responses conferred long-term protection against HPV-induced carcinomas in the skin and liver, and this protection required the induction and accumulation of CD8+ TRM cells. Moreover, the formation of CD8+ TRM cells could be enhanced by temporal targeting CD80/CD86 costimulatory interactions via CTLA-4 blockade early after immunization.

CONCLUSIONS

Together, these data show that adenoviral vector-induced CD8+ T cell inflation promotes protective TRM cell populations, and this can be enhanced by targeting CTLA-4.

Application of Fluorescent Protein Expressing Strains to Evaluation of Anti-Tuberculosis Therapeutic Efficacy In Vitro and In Vivo

The slow growth of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), hinders development of new diagnostics, therapeutics and vaccines. Using non-invasive real-time imaging technologies to monitor the disease process in live animals would facilitate TB research in all areas. We developed fluorescent protein (FP) expressing Mycobacterium bovis BCG strains for in vivo imaging, which can be used to track bacterial location, and to quantify bacterial load in live animals. We selected an optimal FP for in vivo imaging, by first cloning six FPs: tdTomato, mCherry, mPlum, mKate, Katushka and mKeima, into mycobacteria under either a mycobacterial Hsp60 or L5 promoter, and compared their fluorescent signals in vitro and in vivo. Fluorescence from each FP-expressing strain was measured with a multimode reader using the optimal excitation and emission wavelengths for the FP. After normalizing bacterial numbers with optical density, the strain expressing L5-tdTomato displayed the highest fluorescence. We used the tdTomato-labeled M. bovis BCG to obtain real-time images of pulmonary infections in living mice and rapidly determined the number of bacteria present. Further comparison between L5-tdTomato and Hsp60-tdTomato revealed that L5-tdTomato carried four-fold more tdTomato gene copies than Hsp60-tdTomato, which eventually led to higher protein expression of tdTomato. Evaluating anti-TB efficacy of rifampicin and isoniazid therapy in vitro and in vivo using the L5-tdTomato strain demonstrated that this strain can be used to identify anti-TB therapeutic efficacy as quickly as 24 h post-treatment. These M. bovis BCG reporter strains represent a valuable new tool for evaluation of therapeutics, vaccines and virulence.

Intravenous genetic mesothelin vaccine based on human adenovirus 40 inhibits growth and metastasis of pancreatic cancer

High pancreatic cancer mortality and poor prognosis are caused by the difficulty for early diagnosis and extremely low rates of resection because of metastasis. Mesothelin overexpression in pancreatic cancer is a remarkable biomarker for tumor progression, especially for invasion and metastasis. Here, we generated a novel replication-defective recombinant adenovirus 40 (rAd40), whose gene delivery properties are totally different from a conventional rAd5. In this study, we have identified intravenous administration with rAd40 expressing mouse mesothelin (Msln) as an effective prophylactic cancer vaccine against metastatic lesions of pancreatic cancer in mice. Intravenous administration of rAd40 (rAd40 i.v.) achieved transgene delivery in wider range of organs compared to rAd5 i.v., while rAd5 was distributed mainly to the liver, spleen, and lungs. Additionally, rAd40 i.v. showed less transduction of the liver or inflammatory responses, resulted in reduced liver toxicity compared to rAd5 i.v. Also, more robust systemic antigen-specific immune responses were stimulated by rAd40 i.v. Pretreatment with a single ovalbumin-expressing rAd40 i.v. prevented tumor growth in mouse subcutaneous models of ovalbumin-expressing pancreatic cancer. When used with Msln-expressing rAd40 i.v., Msln protein expression and metastases were suppressed in a syngeneic orthotopic mouse model of pancreatic cancer, corresponding to the detection of Msln- and tumor-specific cytotoxic T lymphocyte (CTL). Our novel methods generated antitumor effects against antigen-expressing tumors through antigen- and tumor-specific CTL-mediated immunity. Thus, our results indicate that a rAd40-based intravenous vaccine provides a new strategy for the effective control of metastatic pancreatic cancer and novel therapy against other cancers and infectious diseases.

Induction of humoral and cellular immune responses by antigen-expressing immunostimulatory liposomes

Recently we have shown that liposomes can be used as artificial microbes for the production and delivery of DNA-encoded antigens. These so-called antigen-expressing immunostimulatory liposomes (AnExILs) were superior in inducing antigen-specific antibodies compared to conventional liposomal protein or DNA vaccines when tested in mice after i.m. immunization. In this study, we investigated the capacity of AnExILs to induce T-cell responses. By using a plasmid vector encoding a model antigen under control of both the prokaryotic T7 and the eukaryotic CMV promoter we hypothesized that antigen production could lead to CTL activation via two distinct routes: i. production of antigens inside the AnExILs with subsequent cross-presentation after processing by APCs and ii. endogenous production of antigens after AnExIL-mediated transfection of the pDNA. Although we were not able to demonstrate transfection-mediated expression of luc-NP in mice, i.m. injection of AnExILs producing luc-NP resulted in T-cell responses against the encoded NP epitope, as determined by tetramer staining. T-cell responses were comparable to the responses obtained after i.m. injection of naked pDNA. In order to find out whether CTL activation was caused by cross-presentation of the exogenous antigens produced inside AnExILs or by endogenous antigen production from transfection with the same pDNA source a second study was initiated in which the contribution of each of these effects could be separately determined. These results demonstrate that the observed T-cell responses were not exclusively caused by cross-presentation of the AnExIL-produced antigens alone, but were rather a combination of dose-dependent antigen cross-presentation and low levels of endogenous antigen production.

Expression of type I interferon by splenic macrophages suppresses adaptive immunity during sepsis

Early during Gram-negative sepsis, excessive release of pro-inflammatory cytokines can cause septic shock that is often followed by a state of immune paralysis characterized by the failure to mount adaptive immunity towards secondary microbial infections. Especially, the early mechanisms responsible for such immune hypo-responsiveness are unclear. Here, we show that TLR4 is the key immune sensing receptor to initiate paralysis of T-cell immunity after bacterial sepsis. Downstream of TLR4, signalling through TRIF but not MyD88 impaired the development of specific T-cell immunity against secondary infections. We identified type I interferon (IFN) released from splenic macrophages as the critical factor causing T-cell immune paralysis. Early during sepsis, type I IFN acted selectively on dendritic cells (DCs) by impairing antigen presentation and secretion of pro-inflammatory cytokines. Our results reveal a novel immune regulatory role for type I IFN in the initiation of septic immune paralysis, which is distinct from its well-known immune stimulatory effects. Moreover, we identify potential molecular targets for therapeutic intervention to overcome impairment of T-cell immunity after sepsis.

Whole-body imaging of infection using fluorescence

Optical imaging is emerging as a powerful tool to study physiological, neurological, oncological, cell biological, molecular, developmental, immunological, and infectious processes. This unit describes the use of fluorescent reporters for biological organisms, components, or events. We describe the application of fluorescence imaging to examination of infectious processes, in particular subcutaneous and pulmonary bacterial infections, but the same approaches are applicable to nearly any infectious route. The strategies described use mycobacterial infections as an example, but nearly identical systems can be used for Pseudomonas, Legionella, Salmonella, Escherichia, Borrelia, and Staphylococus, suggesting that the approaches are generally applicable to nearly any infectious agent. Two strategies for fluorescence imaging are described: the first method uses reporter enzyme fluorescence (REF), and the second uses fluorescent proteins for fluorescence imaging. Methods are described in detail to facilitate successful application of these emerging technologies to nearly any experimental system.

Delivery route, MyD88 signaling and cross-priming events determine the anti-tumor efficacy of an adenovirus based melanoma vaccine

Adenovirus (Ad)-based vaccines are considered for cancer immunotherapy, yet, detailed knowledge on their mechanism of action and optimal delivery route for anti-tumor efficacy is lacking. Here, we compared the anti-tumor efficacy of an Ad-based melanoma vaccine after intradermal, intravenous, intranasal or intraperitoneal delivery in the B16F10 melanoma model. The intradermal route induced superior systemic anti-melanoma immunity which was MyD88 signaling-dependent. Predominant transduction of non-professional antigen-presenting cells at the dermal vaccination sites and draining lymph nodes, suggested a role for cross-presentation, which was confirmed in vitro. We conclude that the dermis provides an optimal route of entry for Ad-based vaccines for high-efficacy systemic anti-tumor immunization and that this immunization likely involves cross-priming events in the draining lymph nodes.

The Hsc/Hsp70 co-chaperone network controls antigen aggregation and presentation during maturation of professional antigen presenting cells

The maturation of mouse macrophages and dendritic cells involves the transient deposition of ubiquitylated proteins in the form of dendritic cell aggresome-like induced structures (DALIS). Transient DALIS formation was used here as a paradigm to study how mammalian cells influence the formation and disassembly of protein aggregates through alterations of their proteostasis machinery. Co-chaperones that modulate the interplay of Hsc70 and Hsp70 with the ubiquitin-proteasome system (UPS) and the autophagosome-lysosome pathway emerged as key regulators of this process. The chaperone-associated ubiquitin ligase CHIP and the ubiquitin-domain protein BAG-1 are essential for DALIS formation in mouse macrophages and bone-marrow derived dendritic cells (BMDCs). CHIP also cooperates with BAG-3 and the autophagic ubiquitin adaptor p62 in the clearance of DALIS through chaperone-assisted selective autophagy (CASA). On the other hand, the co-chaperone HspBP1 inhibits the activity of CHIP and thereby attenuates antigen sequestration. Through a modulation of DALIS formation CHIP, BAG-1 and HspBP1 alter MHC class I mediated antigen presentation in mouse BMDCs. Our data show that the Hsc/Hsp70 co-chaperone network controls transient protein aggregation during maturation of professional antigen presenting cells and in this way regulates the immune response. Similar mechanisms may modulate the formation of aggresomes and aggresome-like induced structures (ALIS) in other mammalian cell types.

Reporter enzyme fluorescence (REF) imaging and quantification of tuberculosis in live animals

The slow growth rate of Mycobacterium tuberculosis hinders research progress, since estimating the bacterial numbers present in all experiments normally relies on determination of colony forming units on agar plates. M. tuberculosis colonies can take as long as four to six weeks to become visible. Whole animal imaging is an emerging technology that has broad applications in all areas of biological sciences, including monitoring infections. Imaging allows bacterial numbers to be determined in real-time for each infected animal, individually, which allows inter-animal variability to be observed and controlled for. Reporter enzyme fluorescence (REF) utilizes custom substrates that allow production of a fluorescent product after cleavage by a bacterial enzyme. In our recently published studies, we demonstrate that the enzyme β-lactamase, a naturally occurring enzyme expressed by M. tuberculosis, can be used for REF. The resulting imaging system is the first that allows non-invasive detection of natural M. tuberculosis strains directly in pulmonary infected living animals. Use of REF for M. tuberculosis infected mice allows detection of ~10⁴ CFU in the lungs, which is very sensitive. This system also displays promise for allowing rapid evaluation of differences in virulence strains and efficacy of therapeutics and vaccines. This system could be developed into a diagnostic tool for tuberculosis through the use of REF to identify infected tissues or other diagnostic specimens.

Quality of the transgene-specific CD8+ T cell response induced by adenoviral vector immunization is critically influenced by virus dose and route of vaccination

Adenoviral vectors have been widely used for experimental gene therapy and vaccination, yet there is a surprising lack of knowledge connecting the route and dose of adenovirus administration to the induced transgene-specific immune response. We have recently demonstrated polyfunctional CD8(+) T cells and protective memory responses using adenoviral vectors, which seem to contrast with recent reports suggesting that an exhausted CD8(+) T cell phenotype is induced by inoculation with adenoviral vectors. Accordingly, we investigated the route and dose interrelationship for transgene-specific CD8(+) T cells using adenoviral vectors encoding beta-galactosidase applied either s.c. or i.v. Irrespective of the route of inoculation, most of the adenoviral inoculum was found to disseminate systemically as the dose was raised beyond 10(9) particles. The number of transgene-specific CD8(+) T cells correlated positively with dissemination, whereas the functional capacity of the generated T cells correlated inversely with vector dissemination. A comparison of the immune response to s.c. or i.v. administration at moderate doses revealed that inoculation by both routes induced a transient peak of IFN-gamma-producing CD8(+) T cells 2 to 3 wk postinfection, but following i.v. administration, these cells were only detected in the liver. Two to four months after systemic, but not peripheral, immunization, dysfunctional transgene-specific CD8(+) T cells impaired in both cytokine production and important in vivo effector functions, accumulated in the spleen. These findings indicate that the localization of the adenoviral inoculum and not the total Ag load determines the quality of the CD8(+) T cell response induced with adenoviral vaccines.

Liver sinusoidal endothelial cells veto CD8 T cell activation by antigen-presenting dendritic cells

The liver is known to induce tolerance rather than immunity through tolerogenic antigen presentation or elimination of effector T cells. In particular, hepatic dendritic cells (DC) are known to be little immunogenic for CD8 T cells. Here, we investigated whether this peculiar phenotype resulted from interaction with resident hepatic cell populations. Contact of DC with liver sinusoidal endothelial cells (LSEC) but not hepatocytes or B cells vetoed antigen-presenting DC to fully activate naive CD8 T cells. This MHC-independent regulatory effect of LSEC on DC function was not connected to soluble mediators but required physical contact. Because interaction with third-party LSEC still allowed antigen-presenting DC to stimulate expression of initial activation markers on naive CD8 T cells and to stimulate activated CD8 T cells, we hypothesize that LSEC controlled the DC costimulatory function. Indeed, contact with LSEC led to reduced DC expression levels of CD80/86 or IL-12, but supplementation of these signals failed to rescue the ability to prime naive CD8 T cells, indicating involvement of further molecules. Taken together, our results reveal a novel principle operative in hepatic tolerance induction, in which LSEC not only tolerize T cells themselves but also suppress neighboring APC normally capable of inducing T cell immunity.

Cytosolic delivery of membrane-impermeable molecules in dendritic cells using pH-responsive core-shell nanoparticles

Polycations that absorb protons in response to the acidification of endosomes can theoretically disrupt these vesicles via the "proton sponge" effect. To exploit this mechanism, we created nanoparticles with a segregated core-shell structure for efficient, noncytotoxic intracellular drug delivery. Cross-linked polymer nanoparticles were synthesized with a pH-responsive core and hydrophilic charged shell designed to disrupt endosomes and mediate drug/cell binding, respectively. By sequestering the relatively hydrophobic pH-responsive core component within a more hydrophilic pH-insensitive shell, nontoxic delivery of small molecules and proteins to the cytosol was achieved in dendritic cells, a key cell type of interest in the context of vaccines and immunotherapy.

Engineering bacterial vectors for delivery of genes and proteins to antigen-presenting cells

Bacterial vectors offer a biological route to gene and protein delivery with this article featuring delivery to antigen-presenting cells (APCs). Primarily in the context of immune stimulation against infectious disease or cancer, the goal of bacterially mediated delivery is to overcome the hurdles to effective macromolecule delivery. This review will present several bacterial vectors as macromolecule (protein or gene) delivery devices with both innate and acquirable (or engineered) biological features to facilitate delivery to APCs. The review will also present topics related to large-scale manufacture, storage, and distribution that must be considered if the bacterial delivery devices are ever to be used in a global market.