The transcription factor CREB1 is a mechanistic driver of immunogenicity and reduced HIV-1 acquisition following ALVAC vaccination

Development of effective human immunodeficiency virus 1 (HIV-1) vaccines requires synergy between innate and adaptive immune cells. Here we show that induction of the transcription factor CREB1 and its target genes by the recombinant canarypox vector ALVAC + Alum augments immunogenicity in non-human primates (NHPs) and predicts reduced HIV-1 acquisition in the RV144 trial. These target genes include those encoding cytokines/chemokines associated with heightened protection from simian immunodeficiency virus challenge in NHPs. Expression of CREB1 target genes probably results from direct cGAMP (STING agonist)-modulated p-CREB1 activity that drives the recruitment of CD4+ T cells and B cells to the site of antigen presentation. Importantly, unlike NHPs immunized with ALVAC + Alum, those immunized with ALVAC + MF59, the regimen in the HVTN702 trial that showed no protection from HIV infection, exhibited significantly reduced CREB1 target gene expression. Our integrated systems biology approach has validated CREB1 as a critical driver of vaccine efficacy and highlights that adjuvants that trigger CREB1 signaling may be critical for efficacious HIV-1 vaccines.

Effective DNA damage response after acute but not chronic immune challenge: SARS-CoV-2 vaccine versus Systemic Lupus Erythematosus

Whether and how an acute immune challenge may affect DNA Damage Response (DDR) is unknown. By studying vaccinations against Influenza and SARS-CoV-2 (mRNA-based) we found acute increases of type-I interferon-inducible gene expression, oxidative stress and DNA damage accumulation in blood mononuclear cells of 9 healthy controls, coupled with effective anti-SARS-CoV-2 neutralizing antibody production in all. Increased DNA damage after SARS-CoV-2 vaccine, partly due to increased oxidative stress, was transient, whereas the inherent DNA repair capacity was found intact. In contrast, in 26 patients with Systemic Lupus Erythematosus, who served as controls in the context of chronic immune activation, we validated increased DNA damage accumulation, increased type-I interferon-inducible gene expression and induction of oxidative stress, however aberrant DDR was associated with deficiencies in nucleotide excision repair pathways. These results indicate that acute immune challenge can indeed activate DDR pathways, whereas, contrary to chronic immune challenge, successful repair of DNA lesions occurs.

Structural Fine-Tuning of Desmuramylpeptide NOD2 Agonists Defines Their In Vivo Adjuvant Activity

We report on the design, synthesis, and biological evaluation of a series of nucleotide-binding oligomerization-domain-containing protein 2 (NOD2) desmuramylpeptide agonists with improved in vitro and in vivo adjuvant properties. We identified two promising compounds: 68, a potent nanomolar in vitro NOD2 agonist, and the more lipophilic 75, which shows superior adjuvant activity in vivo. Both compounds had immunostimulatory effects on peripheral blood mononuclear cells at the protein and transcriptional levels, and augmented dendritic-cell-mediated activation of T cells, while 75 additionally enhanced the cytotoxic activity of peripheral blood mononuclear cells against malignant cells. The C₁₈ lipophilic tail of 75 is identified as a pivotal structural element that confers in vivo adjuvant activity in conjunction with a liposomal delivery system. Accordingly, liposome-encapsulated 75 showed promising adjuvant activity in mice, surpassing that of muramyl dipeptide, while achieving a more balanced Th1/Th2 immune response, thus highlighting its potential as a vaccine adjuvant.

Deletion of immune evasion genes provides an effective vaccine design for tumor-associated herpesviruses

Vaccines based on live attenuated viruses often induce broad, multifaceted immune responses. However, they also usually sacrifice immunogenicity for attenuation. It is particularly difficult to elicit an effective vaccine for herpesviruses due to an armament of immune evasion genes and a latent phase. Here, to overcome the limitation of attenuation, we developed a rational herpesvirus vaccine in which viral immune evasion genes were deleted to enhance immunogenicity while also attaining safety. To test this vaccine strategy, we utilized murine gammaherpesvirus-68 (MHV-68) as a proof-of-concept model for the cancer-associated human γ-herpesviruses, Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus. We engineered a recombinant MHV-68 virus by targeted inactivation of viral antagonists of type I interferon (IFN-I) pathway and deletion of the latency locus responsible for persistent infection. This recombinant virus is highly attenuated with no measurable capacity for replication, latency, or persistence in immunocompetent hosts. It stimulates robust innate immunity, differentiates virus-specific memory T cells, and elicits neutralizing antibodies. A single vaccination affords durable protection that blocks the establishment of latency following challenge with the wild type MHV-68 for at least six months post-vaccination. These results provide a framework for effective vaccination against cancer-associated herpesviruses through the elimination of latency and key immune evasion mechanisms from the pathogen.

Nanoformulated Single-Stranded RNA-Based Adjuvant with a Coordinative Amphiphile as an Effective Stabilizer: Inducing Humoral Immune Response by Activation of Antigen-Presenting Cells

As agonists of TLR7/8, single-stranded RNAs (ssRNAs) are safe and promising adjuvants that do not cause off-target effects or innate immune overactivation. However, low stability prevents them from mounting sufficient immune responses. This study evaluates the adjuvant effects of ssRNA derived from the cricket paralysis virus intergenic region internal ribosome entry site, formulated as nanoparticles with a coordinative amphiphile, containing a zinc/dipicolylamine complex moiety as a coordinative phosphate binder, as a stabilizer for RNA-based adjuvants. The nanoformulated ssRNA adjuvant was resistant to enzymatic degradation in vitro and in vivo, and that with a coordinative amphiphile bearing an oleyl group (CA-O) was approximately 100 nm, promoted effective recognition, and improved activation of antigen-presenting cells, leading to better induction of neutralizing antibodies following single immunization. Hence, CA-O may increase the efficacy of ssRNA-based adjuvants, proving useful to meet the urgent need for vaccines during pathogen outbreaks.

Cricket paralysis virus internal ribosome entry site-derived RNA promotes conventional vaccine efficacy by enhancing a balanced Th1/Th2 response

•

RNA adjuvant was developed from the CrPV intergenic region IRES.

•

The RNA adjuvant functioned as an adjuvant with protein-based vaccines.

•

The RNA adjuvant increased vaccine efficacy and induced balanced Th1/Th2 response.

•

The RNA adjuvant enhanced APC chemotaxis.

An ideal adjuvant should increase vaccine efficacy through balanced Th1/Th2 responses and be safe to use. Recombinant protein-based vaccines are usually formulated with aluminum (alum)-based adjuvants to ensure an adequate immune response. However, use of alum triggers a Th2-biased immune induction, and hence is not optimal. Although the adjuvanticity of RNA has been reported, a systematic and overall investigation on its efficacy is lacking. We found that single strand RNA (termed RNA adjuvant) derived from cricket paralysis virus intergenic region internal ribosome entry site induced the expression of various adjuvant-function-related genes, such as type 1 and 2 interferon (IFN) and toll-like receptor (TLR), T cell activation, and leukocyte chemotaxis in human peripheral blood mononuclear cells; furthermore, its innate and IFN transcriptome profile patterns were similar to those of a live-attenuated yellow fever vaccine. This suggests that protein-based vaccines formulated using RNA adjuvant function as live-attenuated vaccines. Application of the RNA adjuvant in mouse enhanced the efficacy of Middle East respiratory syndrome spike protein, a protein-subunit vaccine and human papillomavirus L1 protein, a virus-like particle vaccine, by activating innate immune response through TLR7 and enhancing pAPC chemotaxis, leading to a balanced Th1/Th2 responses. Moreover, the combination of alum and the RNA adjuvant synergistically induced humoral and cellular immune responses and endowed long-term immunity. Therefore, RNA adjuvants have broad applicability and can be used with all conventional vaccines to improve vaccine efficacy qualitatively and quantitively.

Innate sensors that regulate vaccine responses

Pattern recognition receptors (PRRs) control elemental functions of antigen presenting cells (APCs) and critically shape adaptive immune responses. Wielding a natural adjuvanticity, live attenuated vaccines elicit exceptionally efficient and durable immunity. Commonly used vaccine adjuvants target individual PRRs or bolster the immunogenicity of vaccines via indirect mechanisms of inflammation. Here, we review the impact of innate sensors on immune responses to live attenuated vaccines and commonly used vaccine adjuvants, with a focus on human vaccine responses. We discuss the unique potential of microbial nucleic acids and their corresponding sensing receptors to mimic live attenuated vaccines and promote protective immunity.

Elevated monocyte-specific type I interferon signalling correlates positively with cardiac healing in myocardial infarct patients but interferon alpha application deteriorates myocardial healing in rats

Monocytes are involved in adverse left ventricular (LV) remodelling following myocardial infarction (MI). To provide therapeutic opportunities we aimed to identify gene transcripts in monocytes that relate to post-MI healing and evaluated intervention with the observed gene activity in a rat MI model. In 51 MI patients treated by primary percutaneous coronary intervention (PCI), the change in LV end-diastolic volume index (EDVi) from baseline to 4-month follow-up was assessed using cardiovascular magnetic resonance imaging (CMR). Circulating monocytes were collected at day 5 (Arterioscler Thromb Vasc Biol 35:1066-1070, 2015; Cell Stem Cell 16:477-487, 2015; Curr Med Chem 13:1877-1893, 2006) after primary PCI for transcriptome analysis. Transcriptional profiling and pathway analysis revealed that patients with a decreased LV EDVi showed an induction of type I interferon (IFN) signalling (type I IFN pathway: P value < 0.001; false discovery rate < 0.001). We subsequently administered 15,000 Units of IFN-α subcutaneously in a rat MI model for three consecutive days following MI. Cardiac function was measured using echocardiography and infarct size/cardiac inflammation using (immuno)-histochemical analysis. We found that IFN-α application deteriorated ventricular dilatation and increased infarct size at day 28 post-MI. Moreover, IFN-α changed the peripheral monocyte subset distribution towards the pro-inflammatory monocyte subset whereas in the myocardium, the presence of the alternative macrophage subset was increased at day 3 post-MI. Our findings suggest that induction of type I IFN signalling in human monocytes coincides with adverse LV remodelling. In rats, however, IFN-α administration deteriorated post-MI healing. These findings underscore important but also contradictory roles for the type I IFN response during cardiac healing following MI.

Antiviral activity of porcine interferon omega 7 against foot-and-mouth disease virus in vitro

Foot‐and‐mouth disease (FMD) is a disease of worldwide economic importance, and vaccines play an important role in preventing FMDV outbreaks. However, new control strategies are still needed since FMDV outbreaks still occur in some disease‐free countries. Currently, interferon (IFN)‐based strategies have been demonstrated to be an efficient biotherapeutic option against FMDV; however, interferon omega (IFN‐ω) has not yet been assessed in this capacity. Thus, this study evaluated the antiviral activity of porcine IFN omega 7 (PoIFN‐ω7) against FMDV. After the PoIFN‐ω7 was expressed and purified, cell proliferation assays and quantitative real‐time reverse transciption‐polymerase chain reaction were used to evaluate the effective anti‐cytopathic concentration of PoIFN‐ω7 and its effectiveness pre‐ and post‐infection with FMDV in swine kidney cells (IBRS‐2). Results showed the rHis‐PoIFN‐ω7 fusion protein was considerably expressed using Escherichia coli BL21 (DE3) strain, and the recombinant protein exhibited significant in vitro protection against FMDV, including two strains belonging to type O and A FMDV, respectively. In addition, PoIFN‐ω7 upregulated the transcription of Mx1, ISG15, OAS1, and PKR genes. These findings indicated that IFN‐ω has the potential for serving as a useful therapeutic agent to prevent FMDV or other viral outbreaks in pigs.

1.

PoIFN‐ω7 exerted effective antiviral activity against FMDV pre‐ and post‐infection in vitro.

2.

PoIFN‐ω7 induced the transcription of IFN‐stimulated genes, including Mx1, ISG15, OAS1, and PKR genes.

Negative regulation of type I IFN signaling

Type I IFNs (α, β, and others) are a family of cytokines that are produced in physiological conditions as well as in response to the activation of pattern recognition receptors. They are critically important in controlling the host innate and adaptive immune response to viral and some bacterial infections, cancer, and other inflammatory stimuli. However, dysregulation of type I IFN production or response can contribute to immune pathologies termed "interferonopathies", pointing to the importance of balanced activating signals with tightly regulated mechanisms of tuning this signaling. Here, we summarize the recent advances of how type I IFN production and response are controlled at multiple levels of the type I IFN signaling cascade.

A new HDV mouse model identifies mitochondrial antiviral signaling protein (MAVS) as a key player in IFN-β induction

BACKGROUND & AIMS

Studying hepatitis delta virus (HDV) and developing new treatments is hampered by the limited availability of small animal models. Herein, a description of a robust mouse model of HDV infection that mimics several important characteristics of the human disease is presented.

METHODS

HDV and hepatitis B virus (HBV) replication competent genomes were delivered to the mouse liver using adeno-associated viruses (AAV; AAV-HDV and AAV-HBV). Viral load, antigen expression and genomes were quantified at different time points after AAV injection. Furthermore, liver pathology, genome editing, and the activation of the innate immune response were evaluated.

RESULTS

AAV-HDV infection initiated HDV replication in mouse hepatocytes. Genome editing was confirmed by the presence of small and large HDV antigens and sequencing. Viral replication was detected for 45days, even after the AAV-HDV vector had almost disappeared. In the presence of HBV, HDV infectious particles were detected in serum. Furthermore, as observed in patients, co-infection was associated with the reduction of HBV antigen expression and the onset of liver damage that included the alteration of genes involved in the development of liver pathologies. HDV replication induced a sustained type I interferon response, which was significantly reduced in immunodeficient mice and almost absent in mitochondrial antiviral signaling protein (MAVS)-deficient mice.

CONCLUSION

The animal model described here reproduces important characteristics of human HDV infection and provides a valuable tool for characterizing the viral infection and for developing new treatments. Furthermore, MAVS was identified as a main player in HDV detection and adaptive immunity was found to be involved in the amplification of the innate immune response. Lay summary: Co-infection with hepatitis B and D virus (HBV and HDV, respectively) often causes a more severe disease condition than HBV alone. Gaining more insight into HDV and developing new treatments is hampered by limited availability of adequate immune competent small animal models and new ones are needed. Here, a mouse model of HDV infection is described, which mimics several important characteristics of the human disease, such as the initiation and maintenance of replication in murine hepatocytes, genome editing and, in the presence of HBV, generation of infectious particles. Lastly, the involvement of an adaptive immunity and the intracellular signaling molecule MAVS in mounting a strong and lasting innate response was shown. Thus, our model serves as a useful tool for the investigation of HDV biology and new treatments.

Innate Control of Adaptive Immunity: Beyond the Three-Signal Paradigm

Activation of cells in the adaptive immune system is a highly orchestrated process dictated by multiples cues from the innate immune system. Although the fundamental principles of innate control of adaptive immunity are well established, it is not fully understood how innate cells integrate qualitative pathogenic information to generate tailored protective adaptive immune responses. In this review, we discuss complexities involved in the innate control of adaptive immunity that extend beyond TCR engagement, costimulation, and priming cytokine production but are critical for the generation of protective T cell immunity.

Improving Adoptive T Cell Therapy: The Particular Role of T Cell Costimulation, Cytokines, and Post-Transfer Vaccination

Adoptive cellular therapy (ACT) is a form of immunotherapy whereby antigen-specific T cells are isolated or engineered, expanded ex vivo, and transferred back to patients. Clinical benefit after ACT has been obtained in treatment of infection, various hematological malignancies, and some solid tumors; however, due to poor functionality and persistence of the transferred T cells, the efficacy of ACT in the treatment of most solid tumors is often marginal. Hence, much effort is undertaken to improve T cell function and persistence in ACT and significant progress is being made. Herein, we will review strategies to improve ACT success rates in the treatment of cancer and infection. We will deliberate on the most favorable phenotype for the tumor-specific T cells that are infused into patients and on how to obtain T cells bearing this phenotype by applying novel ex vivo culture methods. Moreover, we will discuss T cell function and persistence after transfer into patients and how these factors can be manipulated by means of providing costimulatory signals, cytokines, blocking antibodies to inhibitory molecules, and vaccination. Incorporation of these T cell stimulation strategies and combinations of the different treatment modalities are likely to improve clinical response rates further.

Age-Associated Failure To Adjust Type I IFN Receptor Signaling Thresholds after T Cell Activation

With increasing age, naive CD4 T cells acquire intrinsic defects that compromise their ability to respond and differentiate. Type I IFNs, pervasive constituents of the environment in which adaptive immune responses occur, are known to regulate T cell differentiation and survival. Activated naive CD4 T cells from older individuals have reduced responses to type I IFN, a defect that develops during activation and that is not observed in quiescent naive CD4 T cells. Naive CD4 T cells from young adults upregulate the expression of STAT1 and STAT5 after activation, lowering their threshold to respond to type I IFN stimulation. The heightened STAT signaling is critical to maintain the expression of CD69 that regulates lymphocyte egress and the ability to produce IL-2 and to survive. Although activation of T cells from older adults also induces transcription of STAT1 and STAT5, failure to exclude SHP-1 from the signaling complex blunts their type I IFN response. In summary, our data show that type I IFN signaling thresholds in naive CD4 T cells after activation are dynamically regulated to respond to environmental cues for clonal expansion and memory cell differentiation. Naive CD4 T cells from older adults have a defect in this threshold calibration. Restoring their ability to respond to type I IFN emerges as a promising target to restore T cell responses and to improve the induction of T cell memory.

Optimization of Fermentation Conditions for Recombinant Human Interferon Beta Production by Escherichia coli Using the Response Surface Methodology

Background:

The periplasmic overexpression of recombinant human interferon beta (rhIFN-β)-1b using a synthetic gene in Escherichia coli BL21 (DE3) was optimized in shake flasks using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD).

Objectives:

This study aimed to predict and develop the optimal fermentation conditions for periplasmic expression of rhIFN-β-1b in shake flasks whilst keeping the acetate excretion as the lowest amount and exploit the best results condition for rhIFN-β in a bench top bioreactor.

Materials and Methods:

The process variables studied were the concentration of glucose as carbon source, cell density prior the induction (OD _{600 nm}) and induction temperature. Ultimately, a three-factor three-level BBD was employed during the optimization process. The rhIFN-β production and the acetate excretion served as the evaluated responses.

Results:

The proposed optimum fermentation condition consisted of 7.81 g L^-1 glucose, OD _{600 nm} prior induction 1.66 and induction temperature of 30.27°C. The model prediction of 0.267 g L^-1 of rhIFN-β and 0.961 g L^-1 of acetate at the optimum conditions was verified experimentally as 0.255 g L^-1 and 0.981 g L^-1 of acetate. This agreement between the predicted and observed values confirmed the precision of the applied method to predict the optimum conditions.

Conclusions:

It can be concluded that the RSM is an effective method for the optimization of recombinant protein expression using synthetic genes in E. coli.

Innate endogenous adjuvants prime to desirable immune responses via mucosal routes

Vaccination is an effective strategy to prevent infectious or immune related diseases, which has made remarkable contribution in human history. Recently increasing attentions have been paid to mucosal vaccination due to its multiple advantages over conventional ways. Subunit or peptide antigens are more reasonable immunogens for mucosal vaccination than live or attenuated pathogens, however adjuvants are required to augment the immune responses. Many mucosal adjuvants have been developed to prime desirable immune responses to different etiologies. Compared with pathogen derived adjuvants, innate endogenous molecules incorporated into mucosal vaccines demonstrate prominent adjuvanticity and safety. Nowadays, cytokines are broadly used as mucosal adjuvants for participation of signal transduction of immune responses, activation of innate immunity and polarization of adaptive immunity. Desired immune responses are promptly and efficaciously primed on basis of specific interactions between cytokines and corresponding receptors. In addition, some other innate molecules are also identified as potent mucosal adjuvants. This review focuses on innate endogenous mucosal adjuvants, hoping to shed light on the development of mucosal vaccines.

A pig tonsil cell culture model for evaluating oral, low-dose IFN-α treatments

Oral, low-dose IFN-α treatments proved effective in several models of viral infections and immunopathological conditions. Also, they do not give rise to the serious side effects observed after parenteral inoculation of high doses (10(5)U/kg b.w. and higher). There is convincing evidence that such treatments work through an early, effective interaction with oral lymphoid tissues before the IFN-α molecules are rapidly destroyed by gut enzymes. Yet, the paucity of detailed information about these crucial interactions and the lack of recognized in vitro models hamper the development of proper administration protocols. On the basis of a previous study, we developed an in vitro model of interaction between different types of human and porcine IFNs-α at low/moderate concentrations and pig tonsil cells. The IFNs-α under study showed different properties with respect to three fundamental control actions: (1) IgA release in culture, (2) release of natural antimicrobial compounds, and (3) homeostatic regulation of the inflammatory response. This was checked in pig intestinal epithelial cells (IPEC-J2 cell line) treated with supernatants of control and IFN α-treated tonsil cell cultures, respectively, in terms of inflammatory cytokine and chemokine responses. Some IFNs-α caused a significant inhibition of IL-8 (protein release and gene expression) and beta-defensin 1 (gene expression) probably through second messengers released by IFN α-treated tonsil cells. Interestingly, a human lymphoblastoid IFN-α under study caused the decrease of polyclonal IgA release by pig tonsil cells and significantly stimulated the in vitro recall antibody response of swine PBMC to Foot-and-Mouth Disease virus. The modulation of IgA and antibacterial compounds was accompanied by an anti-inflammatory control action at the same, low to moderate IFN-α concentrations (1-100 U/ml). This highlights the very foundation of the homeostatic control actions performed by Type I IFNs: to promote an effective host response to infectious and non-infectious stressors and to turn off noxious inflammatory responses associated with tissue damage and waste of metabolic energy. The described tonsil cell model in vitro can be conducive to a further development of oral cytokine treatments in humans and animals in the "one health" conceptual framework.

Type I interferons as regulators of human antigen presenting cell functions

Type I interferons (IFNs) are pleiotropic cytokines, initially described for their antiviral activity. These cytokines exhibit a long record of clinical use in patients with some types of cancer, viral infections and chronic inflammatory diseases. It is now well established that IFN action mostly relies on their ability to modulate host innate and adaptive immune responses. Work in recent years has begun to elucidate the mechanisms by which type I IFNs modify the immune response, and this is now recognized to be due to effects on multiple cell types, including monocytes, dendritic cells (DCs), NK cells, T and B lymphocytes. An ensemble of results from both animal models and in vitro studies emphasized the key role of type I IFNs in the development and function of DCs, suggesting the existence of a natural alliance between these cytokines and DCs in linking innate to adaptive immunity. The identification of IFN signatures in DCs and their dysregulation under pathological conditions will therefore be pivotal to decipher the complexity of this DC-IFN interaction and to better exploit the therapeutic potential of these cells.

Nanoparticle formulation enhanced protective immunity provoked by PYGPI8p-transamidase related protein (PyTAM) DNA vaccine in Plasmodium yoelii malaria model

We have previously reported the new formulation of polyethylimine (PEI) with gamma polyglutamic acid (γ-PGA) nanoparticle (NP) to have provided Plasmodium yoelii merozoite surface protein-1 (PyMSP-1) plasmid DNA vaccine with enhanced protective cellular and humoral immunity in the lethal mouse malaria model. PyGPI8p-transamidase-related protein (PyTAM) was selected as a possible candidate vaccine antigen by using DNA vaccination screening from 29 GPI anchor and signal sequence motif positive genes picked up using web-based bioinformatics tools; though the observed protection was not complete. Here, we observed augmented protective effect of PyTAM DNA vaccine by using PEI and γ-PGA complex as delivery system. NP-coated PyTAM plasmid DNA immunized mice showed a significant survival rate from lethal P. yoelii challenge infection compared with naked PyTAM plasmid or with NP-coated empty plasmid DNA group. Antigen-specific IgG1 and IgG2b subclass antibody levels, proportion of CD4 and CD8T cells producing IFN-γ in the splenocytes and IL-4, IFN-γ, IL-12 and TNF-α levels in the sera and in the supernatants from ex vivo splenocytes culture were all enhanced by the NP-coated PyTAM DNA vaccine. These data indicates that NP augments PyTAM protective immune response, and this enhancement was associated with increased DC activation and concomitant IL-12 production.

Initial afferent lymphatic vessels controlling outbound leukocyte traffic from skin to lymph nodes

Tissue drains fluid and macromolecules through lymphatic vessels (LVs), which are lined by a specialized endothelium that expresses peculiar differentiation proteins, not found in blood vessels (i.e., LYVE-1, Podoplanin, PROX-1, and VEGFR-3). Lymphatic capillaries are characteristically devoid of a continuous basal membrane and are anchored to the ECM by elastic fibers that act as pulling ropes which open the vessel to avoid edema if tissue volume increases, as it occurs upon inflammation. LVs are also crucial for the transit of T lymphocytes and antigen presenting cells from tissue to draining lymph nodes (LN). Importantly, cell traffic control across lymphatic endothelium is differently regulated under resting and inflammatory conditions. Under steady-state non-inflammatory conditions, leukocytes enter into the lymphatic capillaries through basal membrane gaps (portals). This entrance is integrin-independent and seems to be mainly guided by CCL21 chemokine gradients acting on leukocytes expressing CCR7. In contrast, inflammatory processes in lymphatic capillaries involve a plethora of cytokines, chemokines, leukocyte integrins, and other adhesion molecules. Importantly, under inflammation a role for integrins and their ligands becomes apparent and, as a consequence, the number of leukocytes entering the lymphatic capillaries multiplies several-fold. Enhancing transmigration of dendritic cells en route to LN is conceivably useful for vaccination and cancer immunotherapy, whereas interference with such key mechanisms may ameliorate autoimmunity or excessive inflammation. Recent findings illustrate how, transient cell-to-cell interactions between lymphatic endothelial cells and leukocytes contribute to shape the subsequent behavior of leukocytes and condition the LV for subsequent trans-migratory events.

Porcine neonatal blood dendritic cells, but not monocytes, are more responsive to TLRs stimulation than their adult counterparts

The neonatal immune system is often considered as immature or impaired compared to the adult immune system. This higher susceptibility to infections is partly due to the skewing of the neonatal immune response towards a Th2 response. Activation and maturation of dendritic cells (DCs) play an important role in shaping the immune response, therefore, DCs are a target of choice for the development of efficient and protective vaccine formulations able to redirect the neonatal immune response to a protective Th1 response. As pigs are becoming more important for vaccine development studies due to their similarity to the human immune system, we decided to compare the activation and maturation of a subpopulation of porcine DCs in adult and neonatal pigs following stimulation with different TLR ligands, which are promising candidates for adjuvants in vaccine formulations. Porcine blood derived DCs (BDCs) were directly isolated from blood and consisted of a mix of conventional and plasmacytoid DCs. Following CpG ODN (TLR9 ligand) and imiquimod (TLR7 ligand) stimulation, neonatal BDCs showed higher levels of expression of costimulatory molecules and similar (CpG ODN) or higher (imiquimod) levels of IL-12 compared to adult BDCs. Another interesting feature was that only neonatal BDCs produced IFN-α after TLR7 or TLR9 ligand stimulation. Stimulation with CpG ODN and imiquimod also induced enhanced expression of several chemokines. Moreover, in a mixed leukocyte reaction assay, neonatal BDCs displayed a greater ability to induce lymphoproliferation. These findings suggest that when stimulated via TLR7 or TLR9 porcine DCs display similar if not better response than adult porcine DCs.

Imidazoquinoline Toll-like receptor 8 agonists activate human newborn monocytes and dendritic cells through adenosine-refractory and caspase-1-dependent pathways

BACKGROUND

Newborns have frequent infections and manifest impaired vaccine responses, motivating a search for neonatal vaccine adjuvants. Alum is a neonatal adjuvant but might confer a T(H)2 bias. Toll-like receptor (TLR) agonists are candidate adjuvants, but human neonatal cord blood monocytes demonstrate impaired T(H)1-polarizing responses to many TLR agonists caused by plasma adenosine acting through cyclic AMP. TLR8 agonists, including imidazoquinolines (IMQs), such as the small synthetic 3M-002, induce adult-level TNF from neonatal monocytes, but the scope and mechanisms of IMQ-induced activation of neonatal monocytes and monocyte-derived dendritic cells (MoDCs) have not been reported.

OBJECTIVE

We sought to characterize IMQ-induced activation of neonatal monocytes and MoDCs.

METHODS

Neonatal cord and adult peripheral blood monocytes and MoDCs were cultured in autologous plasma; levels of alum- and TLR agonist-induced cytokines and costimulatory molecules were measured. TLR8 and inflammasome function were assayed by using small interfering RNA and Western blotting/caspase-1 inhibitory peptide, respectively. The ontogeny of TLR8 agonist-induced cytokine responses was defined in rhesus macaque whole blood ex vivo.

RESULTS

IMQs were more potent and effective than alum at inducing TNF and IL-1β from monocytes. 3M-002 induced robust TLR pathway transcriptome activation and T(H)1-polarizing cytokine production in neonatal and adult monocytes and MoDCs, signaling through TLR8 in an adenosine/cyclic AMP-refractory manner. Newborn MoDCs displayed impaired LPS/ATP-induced caspase-1-mediated IL-1β production but robust 3M-002-induced caspase-1-mediated inflammasome activation independent of exogenous ATP. TLR8 IMQs induced robust TNF and IL-1β in whole blood of rhesus macaques at birth and infancy.

CONCLUSIONS

IMQ TLR8 agonists engage adenosine-refractory TLR8 and inflammasome pathways to induce robust monocyte and MoDC activation and represent promising neonatal adjuvants.

Nonplasmacytoid, high IFN-α-producing, bone marrow dendritic cells

Plasmacytoid dendritic cells (pDC) are the producers of type I IFNs in response to TLR9 ligands. However, we have found that when bone marrow is depleted of pDC, the IFN-α produced in response to TLR9 ligands is not fully removed. We assign the source of this non-pDC IFN-α as a newly described DC type. It displays the high IFN-α producing activity of pDC but to a more limited range of viruses. Unlike pDC, the novel DC display high T cell stimulation capacity. Moreover, unlike mouse pDC, they are matured with GM-CSF and are less prone to apoptosis upon activation stimuli, including viruses. We propose that these DC constitute a novel bone marrow inflammatory DC type, ideally geared to linking innate and adaptive immune responses in bone marrow via their potent IFN-α production and high T cell stimulatory capacity.

Oral-nasopharyngeal dendritic cells mediate T cell-independent IgA class switching on B-1 B cells

Native cholera toxin (nCT) as a nasal adjuvant was shown to elicit increased levels of T-independent S-IgA antibody (Ab) responses through IL-5- IL-5 receptor interactions between CD4⁺ T cells and IgA⁺ B-1 B cells in murine submandibular glands (SMGs) and nasal passages (NPs). Here, we further investigate whether oral-nasopharyngeal dendritic cells (DCs) play a central role in the induction of B-1 B cell IgA class switch recombination (CSR) for the enhancement of T cell-independent (TI) mucosal S-IgA Ab responses. High expression levels of activation-induced cytidine deaminase, Iα-Cμ circulation transcripts and Iμ-Cα transcripts were seen on B-1 B cells purified from SMGs and NPs of both TCRβ^−/− mice and wild-type mice given nasal trinitrophenyl (TNP)-LPS plus nCT, than in the same tissues of mice given nCT or TNP-LPS alone. Further, DCs from SMGs, NPs and NALT of mice given nasal TNP-LPS plus nCT expressed significantly higher levels of a proliferation-inducing ligand (APRIL) than those in mice given TNP-LPS or nCT alone, whereas the B-1 B cells in SMGs and NPs showed elevated levels of transmembrane activator and calcium modulator cyclophilin ligand interactor (TACI) expression. Interestingly, high frequencies of IgA⁺ B-1 B cells were induced when peritoneal IgA⁻ IgM⁺ B cells were stimulated with mucosal DCs from mice given nasal TNP-LPS plus nCT. Taken together, these findings show that nasal nCT plays a key role in the enhancement of mucosal DC-mediated TI IgA CSR by B-1 B cells through their interactions with APRIL and TACI.

IFN-α as a vaccine adjuvant: recent insights into the mechanisms and perspectives for its clinical use

The IFN-α family are pleiotropic cytokines with the longest record of clinical use. Over the last decade, new biological effects of IFN-α on immune cells, including dendritic cells, have been described, supporting the concept that these cytokines can act as effective vaccine adjuvants. Recently, an important advance in our understanding of the mechanisms of interferon adjuvant activity has been achieved. Some clinical studies have been performed to assess the adjuvant activity in individuals immunized with preventive vaccines, showing variable results depending on interferon/vaccine formulation and vaccinated subjects. In spite of many data in animal models, little information is available on the possible advantage of utilizing IFN-α as an adjuvant for cancer vaccines in humans. Further clinical trials specifically designed to explore vaccine adjuvant activity are needed in order to define the best conditions for using IFN-α or IFN-α-conditioned dendritic cells for the development of therapeutic vaccines.

Toward self-adjuvanting subunit vaccines: model peptide and protein antigens incorporating covalently bound toll-like receptor-7 agonistic imidazoquinolines

Toll-like receptor (TLR)-7 agonists show prominent Th1-biased immunostimulatory activities. A TLR7-active N(1)-(4-aminomethyl)benzyl substituted imidazoquinoline 1 served as a convenient precursor for the syntheses of isothiocyanate and maleimide derivatives for covalent attachment to free amine and thiol groups of peptides and proteins. 1 was also amenable to direct reductive amination with maltoheptaose without significant loss of activity. Covalent conjugation of the isothiocyanate derivative 2 to α-lactalbumin could be achieved under mild, non-denaturing conditions, in a controlled manner and with full preservation of antigenicity. The self-adjuvanting α-lactalbumin construct induced robust, high-affinity immunoglobulin titers in murine models. The premise of covalently decorating protein antigens with adjuvants offers the possibility of drastically reducing systemic exposure of the adjuvant, and yet eliciting strong, Th1-biased immune responses.

Epothilone B enhances Class I HLA and HLA-A2 surface molecule expression in ovarian cancer cells

OBJECTIVE

Ovarian cancer is the leading cause of death from gynecologic cancers in the United States. Epothilone B (EpoB), Taxol and vinblastine are anti-neoplastic agents that interfere with microtubules and arrest the cell cycle in the G2/M phase. EpoB is being evaluated in phase III clinical trials, and its analogs are currently being used in the treatment of taxane-resistant metastatic breast cancer. Little is known about the effect of these drugs on the immune response to tumors. Cancer cells evade immune recognition by down-regulating HLA Class I expression, allowing escape from immune surveillance and destruction. Our data illustrates the effect of microtubule-interacting agents on HLA Class I and HLA-A2 expression as well as the modulation of cytokine expression in ovarian cancer cells.

METHODS

Ovarian cancer cells were treated with different concentrations of drugs. Cell surface expression and mRNA transcription of HLA Class I molecules and HLA-A2 was examined. IFNα, IL1β, IL12 and IL6 mRNA expression was also evaluated upon EpoB treatment.

RESULTS

Low-dose EpoB, Taxol and vinblastine greatly increased expression of HLA Class I and HLA-A2 molecules in Hey ovarian cancer cells. EpoB does not modulate HLA expression in drug-resistant ovarian cancer cells. The expression of IFNα, IL1β, IL12 and IL6 is also markedly increased upon EpoB treatment.

CONCLUSIONS

Nanomolar concentrations of microtubule-interacting agents enhance immune-visibility of ovarian cancer cells by increasing HLA Class I and pro-inflammatory cytokine expression. Immune recognition of tumor cells may be improved.

Direct effects of type I interferons on cells of the immune system

Type I interferons (IFN-I) are well-known inducers of tumor cell apoptosis and antiangiogenesis via signaling through a common receptor interferon alpha receptor (IFNAR). IFNAR induces the Janus activated kinase-signal transducer and activation of transcription (JAK-STAT) pathway in most cells, along with other biochemical pathways that may differentially operate, depending on the responding cell subset, and jointly control a large collection of genes. IFNs-I were found to systemically activate natural killer (NK) cell activity. Recently, mouse experiments have shown that IFNs-I directly activate other cells of the immune system, such as antigen-presenting dendritic cells (DC) and CD4 and CD8 T cells. Signaling through the IFNAR in T cells is critical for the acquisition of effector functions. Cross-talk between IFNAR and the pathways turned on by other surface lymphocyte receptors has been described. Importantly, IFNs-I also increase antigen presentation of the tumor cells to be recognized by T lymphocytes. These IFN-driven immunostimulatory pathways offer opportunities to devise combinatorial immunotherapy strategies.

Role of innate signalling pathways in the immunogenicity of alphaviral replicon-based vaccines

Background

Alphaviral replicon-based vectors induce potent immune responses both when given as viral particles (VREP) or as DNA (DREP). It has been suggested that the strong immune stimulatory effect induced by these types of vectors is mediated by induction of danger signals and activation of innate signalling pathways due to the replicase activity. To investigate the innate signalling pathways involved, mice deficient in either toll-like receptors or downstream innate signalling molecules were immunized with DREP or VREP.

Results

We show that the induction of a CD8⁺ T cell response did not require functional TLR3 or MyD88 signalling. However, IRF3, converging several innate signalling pathways and important for generation of pro-inflammatory cytokines and type I IFNs, was needed for obtaining a robust primary immune response. Interestingly, type I interferon (IFN), induced by most innate signalling pathways, had a suppressing effect on both the primary and memory T cell responses after DREP and VREP immunization.

Conclusions

We show that alphaviral replicon-based vectors activate multiple innate signalling pathways, which both activate and restrict the induced immune response. These results further show that there is a delicate balance in the strength of innate signalling and induction of adaptive immune responses that should be taken into consideration when innate signalling molecules, such as type I IFNs, are used as vaccine adjuvant.

Enhancement of anti-Aspergillus T helper type 1 response by interferon-β-conditioned dendritic cells

Although data show the importance of type I interferons (IFNs) in the regulation of the innate and adaptive immunity elicited in response to viral, bacterial and parasitic infections, the functional activities of these cytokines during fungal infections are poorly understood. We examined here the impact of IFN-β on the response of human monocyte-derived dendritic cells (DCs) infected in vitro with Aspergillus fumigatus. Having found that A. fumigatus-infected DCs do not express IFN-β, we evaluated the effect of the exogenous addition of IFN-β on the maturation of human DCs induced by the infection with A. fumigatus conidia. Although the phagocytosis of the fungus was not affected by IFN-β treatment, the expression of CD86 and CD83 induced upon A. fumigatus challenge was enhanced in IFN-β-conditioned DCs, which also showed an increased expression of IL-27 and IL-12p70, members of IL-12 family. Through these modifications, IFN-β improved the capacity of DCs to promote an anti-Aspergillus T helper type 1 response, as evaluated by mixed leucocyte reaction, which plays a crucial role in the control of invasive aspergillosis. Our results identified a novel effect of IFN-β on anti-Aspergillus immune responses which, in turn, might open new perspectives on the use of IFN-β in immunotherapy for fungal infections aimed at enhancing the immunological functions of DCs.

Immunogenic and replicative properties of classical swine fever virus replicon particles modified to induce IFN-α/β and carry foreign genes

Virus replicon particles (VRP) are genetically engineered infectious virions incapable of generating progeny virus due to partial or complete deletion of at least one structural gene. VRP fulfil the criteria of a safe vaccine and gene delivery system. With VRP derived from classical swine fever virus (CSF-VRP), a single intradermal vaccination protects from disease. Spreading of the challenge virus in the host is however not completely abolished. Parameters that are critical for immunogenicity of CSF-VRP are not well characterized. Considering the importance of type I interferon (IFN-α/β) to immune defence development, we generated IFN-α/β-inducing VRP to determine how this would influence vaccine efficacy. We also evaluated the effect of co-expressing granulocyte macrophage colony-stimulating factor (GM-CSF) in the vaccine context. The VRP were capable of long-term replication in cell culture despite the presence of IFN-α/β. In vivo, RNA replication was essential for the induction of an immune response. IFN-α/β-inducing and GM-CSF-expressing CSF-VRP were similar to unmodified VRP in terms of antibody and peripheral T-cell responses, and in reducing the blood levels of challenge virus RNA. Importantly, the IFN-α/β-inducing VRP did show increased efficacy over the unmodified VRP in terms of B-cell and T-cell responses, when tested with secondary immune responses by in vitro restimulation assay.

Cyclophosphamide synergizes with type I interferons through systemic dendritic cell reactivation and induction of immunogenic tumor apoptosis

Successful chemotherapy accounts for both tumor-related factors and host immune response. Compelling evidence suggests that some chemotherapeutic agents can induce an immunogenic type of cell death stimulating tumor-specific immunity. Here, we show that cyclophosphamide (CTX) exerts two types of actions relevant for the induction of antitumor immunity in vivo: (i) effect on dendritic cell (DC) homeostasis, mediated by endogenous type I interferons (IFN-I), leading to the preferential expansion of CD8α(+) DC, the main subset involved in the cross-presentation of cell-derived antigens; and (ii) induction of tumor cell death with clear-cut immunogenic features capable of stimulating tumor infiltration, engulfment of tumor apoptotic material, and CD8 T-cell cross-priming by CD8α(+) DC. Notably, the antitumor effects of CTX were efficiently amplified by IFN-I, the former providing a source of antigen and a "resetting" of the DC compartment and the latter supplying optimal costimulation for T-cell cross-priming, resulting in the induction of a strong antitumor response and tumor rejection. These results disclose new perspectives for the development of targeted and more effective chemoimmunotherapy treatments of cancer patients.

Dendritic cells adhere to and transmigrate across lymphatic endothelium in response to IFN-α

Migration of DC into lymphatic vessels ferries antigenic cargo and pro-inflammatory stimuli into the draining LN. Given that tissues under the influence of viral infections produce type I IFN, it is conceivable that these cytokines enhance DC migration in order to facilitate an antiviral immune response. Cultured lymphatic endothelium monolayers pretreated with TNF-α were used to model this phenomenon under inflammatory conditions. DC differentiated in the presence of either IFN-α2b or IFN-α5 showed enhanced adhesion to cultured lymphatic endothelial cells. These pro-adhesive effects were mediated by DC, not the lymphatic endothelium, and correlated with increased DC transmigration across lymphatic endothelial cell monolayers. Transmigration was guided by chemokines acting on DC, and blocking experiments with mAb indicated a role for LFA-1. Furthermore, incubation of DC with IFN-α led to the appearance of active conformation epitopes on the CD11a integrin chains expressed by DC. Differentiation of mouse DC in the presence of IFN-α also increased DC migration from inflammed footpads toward popliteal LN. Collectively, these results indicate a role for type I IFN in directing DC toward LN under inflammatory conditions.

Expression of hepatitis B virus surface antigen determinants in Lactococcus lactis for oral vaccination

Lactococcus lactis with non-pathogenic and non-colonizing properties is an attractive candidate for delivering biologically active proteins by mucosal routes. In this report we described recombinant L. lactis applicable for the development of live mucosal vaccine against hepatitis B virus (HBV). The PreS region of the HBV surface antigen alone or combined with "a" determinant of S region (PreSa) was cloned and expressed in the food grade bacterium L. lactis using a nisin-controlled expression (NICE) system. Western blot analysis indicated that both PreS and PreSa fusion proteins were successfully expressed in L. lactis after nisin induction. Oral immunization of BALB/c mice with PreS and PreSa-producing strains induced both mucosal (intestinal IgA) and systemic (serum IgG) immune responses against HBV at the same magnitude. Two additional groups of mice given L. lactis expressing human interferon-alpha 2b as an adjuvant with the PreS or PreSa-producing strains produced higher IgG but not IgA antibody responses. These results indicated that the lactococci-derived vaccines could be promising candidates as alternative HBV vaccines for preventing hepatitis B.

Developmental biology of the innate immune response: implications for neonatal and infant vaccine development

Molecular characterization of mechanisms by which human pattern recognition receptors (PRRs) detect danger signals has greatly expanded our understanding of the innate immune system. PRRs include Toll-like receptors, nucleotide oligomerization domain-like receptors, retinoic acid inducible gene-like receptors, and C-type lectin receptors. Characterization of the developmental expression of these systems in the fetus, newborn, and infant is incomplete but has yielded important insights into neonatal susceptibility to infection. Activation of PRRs on antigen-presenting cells enhances costimulatory function, and thus PRR agonists are potential vaccine adjuvants, some of which are already in clinical use. Thus, study of PRRs has also revealed how previously mysterious immunomodulators are able to mediate their actions, including the vaccine adjuvant aluminum hydroxide that activates a cytosolic protein complex known as the Nacht domain leucine-rich repeat and pyrin domain-containing protein 3 inflammasome leading to interleukin-1beta production. Progress in characterizing PRRs is thus informing and expanding the design of improved adjuvants. This review summarizes recent developments in the field of innate immunity emphasizing developmental expression in the fetus, newborn, and infant and its implications for the design of more effective neonatal and infant vaccines.

Adjuvants for porcine reproductive and respiratory syndrome virus vaccines

This review deals with present and past efforts in utilization of vaccine adjuvants for porcine reproductive and respiratory syndrome virus (PRRSV) vaccines. PRRSV vaccines elicit delayed and weak cell-mediated immune (CMI) and antibody responses after vaccination. Several kinds of vaccine adjuvants have been utilized to accelerate and magnify immune responses to PRRSV vaccines. These adjuvants include cytokines, chemical reagents, and bacterial products. Of 11 vaccine adjuvants tested, five (i.e. interleukin-2 (IL-2), IL-12, interferon alpha (IFNalpha), polyinosinic and polycytidylic acid, and cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN)) significantly enhance CMI response to PRRSV vaccines. The response is characterized by proliferation, cytotoxicity, and IFNgamma secretion of peripheral blood mononuclear cells or T cells in response to recall PRRSV antigens in vitro. Two (i.e. CpG ODN and cholera toxin) significantly enhance PRRSV-specific antibody response after vaccination. Two (i.e. IL-2 and CpG ODN) significantly enhance protective efficacy of PRRSV vaccines in challenge models. Improvement of immune responses to PRRSV vaccines should focus in future studies on assessing more vaccine adjuvants for their efficiency in enhancing both CMI and antibody responses and on identifying PRRSV components and strategies that down-modulate pig immune responses in order to devise vaccine adjuvants that can regulate such strategies of the virus.

IFN-beta improves BCG immunogenicity by acting on DC maturation

Given the variable protective efficacy provided by Mycobacterium bovis bacillus Calmette-Guérin (BCG), there is an urgent need to develop new vaccines against tuberculosis. As dendritic cells (DC) play a critical role in initiating and regulating a protective T cell response against the pathogens, the comprehension of mycobacterium-induced modulation of DC functions is critical to pinpoint new, immunological strategies. To this end, a comparative analysis of the effect induced by BCG and Mycobacterium tuberculosis (Mtb) infection on the DC immunophenotype indicated that BCG is less efficient in inducing DC maturation than Mtb. In addition, BCG-infected DC poorly expressed IFN-beta and displayed a reduced production of IL-12 as compared with Mtb-stimulated cells. The impaired expression of IL-12p35 and IFN-beta is likely a result of the inability of BCG to induce the activation of the IFN regulatory factor-3. Taking into account these data, we sought to investigate whether the exogenous addition of IFN-beta, a cytokine that exerts important effects on the immune system, could enhance the Th1-polarizing capacity of BCG-infected DC. Interestingly, when DC infected by BCG were pretreated in vitro with IFN-beta, they displayed a fully mature phenotype and released a significant amount of bioactive IL-12p70, which resulted in an enhanced Th1 response. This study demonstrates that IFN-beta potentiates DC immunological functions following BCG infection, thus suggesting IFN-beta as a possible candidate as vaccine adjuvant.

Peptide-based vaccines for cancer: realizing their potential

Advances in the engineering of peptides, adjuvants and delivery systems have renewed the enthusiasm for peptide-based vaccination regimens in the setting of cancer, and there are a variety of clinical trials being conducted by pharmaceutical companies based on the use of peptides. The challenges to successful cancer immunotherapy are common to all immunotherapeutic strategies and not unique to peptide-based vaccination regimens. This review will describe the advances in the identification, design and delivery of peptides, the challenges to successful immunotherapy and will discuss potential options for the future.