IL-18 potentiates the adjuvant properties of IL-12 in the induction of a strong Th1 type immune response against a recombinant antigen

Allo-Priming Reverses Immunosenescence and May Restore Broad Respiratory Viral Protection and Vaccine Responsiveness to the Elderly: Results of a Phase I/II Clinical Trial

Respiratory viral infections pose a significant health problem that disproportionately affects the elderly. With the aging worldwide population being less responsive to protective vaccines, there is an urgent need for strategies that can protect the elderly from community-acquired viral infections.

BACKGROUND/OBJECTIVES

Allo-priming is a novel immunomodulatory vaccine concept using allogeneic, living, activated Th1 cells that are rejected by the host, creating anti-alloantigen Th1 immunity, increasing Th1 titers. Th1 cells orchestrate cellular immunity, and the age-related decline in Th1 cells contributes to weakened cellular immune response in the elderly, which correlates with poor responsiveness to vaccines and increased susceptibility to respiratory viral infections. Increased Th1 cell titers in the elderly were hypothesized to reverse immunosenescence and restore cellular immune function. Restoration of cellular immune function was predicted to restore broad respiratory viral protection through a heterologous immune mechanism.

METHODS

A phase I/II, multi-center, open-label clinical trial was conducted in 40 healthy adults over 65 years of age to investigate the safety of allo-priming and the effects this vaccination strategy has on cellular immune function over time.

RESULTS

Allo-priming had a benign safety profile and significantly increased the titers of circulating Th1 cells. The increase in Th1 cells was shown to provide broad, self-amplifying respiratory viral protection over time in an ex vivo cytopathic effect assay without additional vaccinations and without any viral antigens included in the formulation, as well acting to increase neutralizing antibody titers in low-responding individuals previously vaccinated for COVID-19.

CONCLUSIONS

These results provide support for an expanded clinical evaluation of this immunomodulatory vaccination strategy as a possible method to restore cellular immune competence to the elderly and provide broad heterologous immune protection from respiratory viral infections without the need for frequent vaccine re-formulations or booster shots (National Library of Medicine: NCT04441047).

Immunostimulant plant proteins: Potential candidates as vaccine adjuvants

The COVID-19 pandemic is shaking up global scientific structures toward addressing antibiotic resistance threats and indicates an urgent need to develop more cost-effective vaccines. Vaccine adjuvants play a crucial role in boosting immunogenicity and improving vaccine efficacy. The toxicity and adversity of most adjuvant formulations are the major human immunization problems, especially in routine pediatric and immunocompromised patients. The present review focused on preclinical studies of immunoadjuvant plant proteins in use with antiparasitic, antifungal, and antiviral vaccines. Moreover, this report outlines the current perspective of immunostimulant plant protein candidates that can be used by researchers in developing new generations of vaccine-adjuvants. Future clinical studies are required to substantiate the plant proteins' safety and applicability as a vaccine adjuvant in pharmaceutical manufacturing.

Immune features of the peritumoral stroma in pancreatic ductal adenocarcinoma

Background

The peritumoral stroma is a hallmark of pancreatic ductal adenocarcinoma (PDA) with implications for disease development, progression and therapy resistance. We systematically investigated immune features of the stroma in PDA patients to identify markers of clinical importance and potential therapeutic targets.

Methods

Tissue and blood samples of 51 PDA patients with clinical and follow-up information were included. Laser Capture Microdissection allowed us to analyze the stromal compartment in particular. Systematic immunohistochemistry, followed by software-based image analysis were conducted. Also, multiplex cytokine analyses (including 50 immune-related molecules) were performed. Functional analyses were performed using patient-derived 3D bioprints. Clinical information was used for survival analyses. Intercompartmental IL9 and IL18 gradients were assessed in matched samples of tumor epithelium, stroma, and serum of patients. Serum levels were compared to an age-matched healthy control group.

Results

Stromal IL9 and IL18 are significantly associated with patient survival. While IL9 is a prognostic favorable marker (p=0.041), IL18 associates with poor patient outcomes (p=0.030). IL9 correlates with an anti-tumoral cytokine network which connects regulation of T helper (Th) 9, Th1 and Th17 cells (all: p<0.05 and r>0.5). IL18 correlates with a Th1-type cytokine phenotype and stromal CXCL12 expression (all: p<0.05 and r>0.5). Further, IL18 associates with a higher level of exhausted T cells. Inhibition of IL18 results in diminished Th1- and Th2-type cytokines. Patients with high stromal IL9 expression have a tumor-to-stroma IL9 gradient directed towards the stroma (p=0.019). Low IL18 expression associates with a tumor-to-stroma IL18 gradient away from the stroma (p=0.007). PDA patients showed higher serum levels of IL9 than healthy controls while serum IL18 levels were significantly lower than in healthy individuals. The stromal immune cell composition is distinct from the tumor epithelium. Stromal density of FoxP3⁺ regulatory T cells showed a tendency towards improved patient survival (p=0.071).

Conclusion

An unexpected high expression of the cytokines IL9 and IL18 at different ends is of significance in the stroma of PDA and relates to opposing patient outcomes. Sub-compartmental cytokine analyses highlight the importance of a differentiated gradient assessment. The findings suggest stromal IL9 and/or IL18 as markers for patient stratification and as potential therapeutic targets. Future steps include investigating e. g. the role of local microbiota as both cytokines are also regulated by microbial compositions.

IFN-γ and IL-18 in conditioned media of parasite-infected host and IL-21-silenced colorectal cancer cells

The presence of certain soluble factors may provide a possible selective advantage for a parasite to gradually modify cell proliferation in neighbouring cells, which may result in chronic diseases. These soluble factors present in the conditioned medium also allow the parasite to invade rapidly into more host cells. The present study aimed to determine the levels of a group of type 1 T helper (Th1) cytokines in the conditioned media of host cells infected with parasites and in IL-21-silenced colorectal cancer cells. The conditioned media of human foreskin fibroblasts (HFFs) parasitized with the RH and ME49 strains of Toxoplasma gondii for 10 days were prepared, and subsequently the levels of the Th1 cytokines in the conditioned media were determined by ELISA. HFFs were incubated with the growth media containing selected soluble factors, and cell proliferation markers were subsequently analysed by reverse transcription-quantitative PCR. The mRNA expression level of cell proliferation markers was also examined in IL-21-silenced HCT116 cells, where the levels of soluble factors in the conditioned media were also determined as aforementioned. The results of the present study demonstrated that HFFs parasitized with ME49 released elevated levels of IFN-γ and lower levels of IL-18 into the conditioned medium compared with the controls. These phenomena were not observed in the conditioned medium of HFFs parasitized with RH. Similar levels of these soluble factors were also detected in the conditioned medium of IL-21-silenced HCT116 cells. The results of the present study also revealed that Ki67 and proliferating cell nuclear antigen mRNA expression was altered in host cells incubated with various levels of IFN-γ and IL-18, as well as in IL-21-silenced HCT116 cells compared with the respective controls. In conclusion, the current study provided preliminary evidence on the fundamental molecular mechanisms of host-parasite interactions that result in chronic diseases, which may aid in the treatment of these diseases in the relevant endemic regions.

Pathogen-host interaction mediated by vesicle-based secretion in schistosomes

As part of the parasite's excretory/secretory system, extracellular vesicles (EVs) represent a potent communication tool of schistosomes with their human host to strike the balance between their own survival in a hostile immunological environment and a minimal damage to the host tissue. Their cargo consists of functional proteins, lipids, and nucleic acids that facilitate biological processes like migration, nutrient acquisition, or reproduction. The most important impact of the vesicle-mediated communication, however, is the promotion of the parasite survival via mimicking host protein function and directly or indirectly modulating the immune response of the host. Overcoming this shield of immunological adaption in the schistosome-host relation is the aim of current research activities in this field and crucial for the development of a reliable anti-schistosomal therapy. Not least because of their prospective use in clinical applications, research on EVs is now a rapidly expanding field. We herein focus on the current state of knowledge of vesicle-based communication of schistosomes and discussing the role of EVs in facilitating biological processes and immune modulatory properties of EVs considering the different life stages of the parasite.

Inflammasomes as Targets for Adjuvants

Inflammasomes are an essential part of the innate immune system. They are necessary for the development of a healthy immune response against infectious diseases. Inflammasome activation leads to the secretion of pro-inflammatory cytokines such as IL-1β and IL-18, which stimulate the adaptive immune system. Inflammasomes activators can be used as adjuvants to provide and maintain the strength of the immune response. This review is focused on the mechanisms of action and the effects of adjuvants on inflammasomes. The therapeutic and prophylaxis significance of inflammasomes in infectious diseases is also discussed.

Blocking NF-κB Is Essential for the Immunotherapeutic Effect of Recombinant IL18 in Pancreatic Cancer

PURPOSE

We sought to find new immune-based treatments for pancreatic cancer.

EXPERIMENTAL DESIGN

We detected IL18 expression in plasma and specimens from patients with pancreatic cancer. We then investigated whether IL18 had a therapeutic effect for pancreatic cancer in vitro and in vivo and any underlying mechanisms.

RESULTS

Higher plasma IL18 was associated with longer overall survival (OS), but higher IL18 in pancreatic cancer tissues was associated with shorter OS and increased invasion and metastasis. Recombinant IL18 alone had no antitumor effect in the syngeneic mice with orthotopically transplanted tumors and promoted tumors in immunocompromised mice; it also facilitated immune responses in vitro and in vivo by augmenting the activity of cytotoxic T cells and NK cells in peripheral blood and lymph nodes. However, IL18 promoted the proliferation and invasion of pancreatic cancer cells, in vitro and in vivo, through the NF-κB pathway. Nevertheless, by coadministrating IL18 with BAY11-7082, an NF-κB inhibitor, we were able to prevent the procancerous effects of IL18 and prolong the survival time of the mice.

CONCLUSIONS

IL18 has both cancer-promoting and cancer-suppressing functions. Although its single-agent treatment has no therapeutic effect on pancreatic cancer, when combined with the NF-κB pathway inhibitor, IL18 improved survival in a murine pancreatic cancer model. Our study implies the possibility of a combinational immunotherapy that uses IL18 and targets NF-κB pathway. Clin Cancer Res; 22(23); 5939-50. ©2016 AACR.

A eukaryotic expression plasmid carrying chicken interleukin-18 enhances the response to newcastle disease virus vaccine

Interleukin-18 (IL-18) is an important cytokine involved in innate and acquired immunity. In this study, we cloned the full-length chicken IL-18 (ChIL-18) gene from specific-pathogen-free (SPF) chicken embryo spleen cells and provided evidence that the ChIL-18 gene in a recombinant plasmid was successfully expressed in chicken DT40 cells. ChIL-18 significantly enhanced gamma interferon (IFN-γ) mRNA expression in chicken splenocytes, which increased IFN-γ-induced nitric oxide (NO) synthesis by macrophages. The potential genetic adjuvant activity of the ChIL-18 plasmid was examined in chickens by coinjecting ChIL-18 plasmid and inactivated Newcastle disease virus (NDV) vaccine. ChIL-18 markedly elevated serum hemagglutination inhibition (HI) titers and anti-hemagglutinin-neuraminidase (anti-HN)-specific antibody levels, induced the secretion of both Th1- (IFN-γ) and Th2- (interleukin-4) type cytokines, promoted the proliferation of T and B lymphocytes, and increased the populations of CD3(+) T cells and their subsets, CD3(+) CD4(+) and CD3(+) CD8(+) T cells. Furthermore, a virus challenge revealed that ChIL-18 contributed to protection against Newcastle disease virus challenge. Taken together, our data indicate that the coadministration of ChIL-18 plasmid and NDV vaccine induces a strong immune response at both the humoral and cellular levels and that ChIL-18 is a novel immunoadjuvant suitable for NDV vaccination.

Schistosome Vaccine Adjuvants in Preclinical and Clinical Research

There is currently no vaccine available for human use for any parasitic infections, including the helminth disease, schistosomiasis. Despite many researchers working towards this goal, one of the focuses has been on identifying new antigenic targets. The bar to achieve protective efficacy in humans was set at a consistent induction of 40% protection or better by the World Health Organisation (WHO), and although this is a modest goal, it is yet to be reached with the six most promising schistosomiasis vaccine candidates (Sm28GST, IrV5, Sm14, paramyosin, TPI, and Sm23). Adjuvant selection has a large impact on the effectiveness of the vaccine, and the use of adjuvants to aid in the stimulation of the immune system is a critical step and a major variable affecting vaccine development. In addition to a comprehensive understanding of the immune system, level of protection and the desired immune response required, there is also a need for a standardised and effective adjuvant formulation. This review summarises the status of adjuvants that have been or are being employed in schistosomiasis vaccine development focusing on immunisation outcomes at preclinical and clinical stages.

IL-18 expression results in a recombinant vaccinia virus that is highly attenuated and immunogenic

Interferon-γ (IFN-γ) is an attenuating factor for vaccinia virus (VACV), decreasing its virulence in vivo by more than a million fold. It is also a highly effective adjuvant when administered at the time of immunization with protein antigens. However, recombinant VACV (rVACV) vaccines expressing IFN-γ do not induce enhanced immune responses. It is possible that the IFN-γ expressed by rVACVs induces both an antiviral state and increased immunological clearance, thus resulting in decreased levels of antigen expression due to reduced viral replication and spread. We conjectured that delaying expression of IFN-γ would result in enhanced production of antigens by rVACVs thus resulting in increased immune responses to foreign antigens. Interleukin (IL)-18, also known as IFN-γ inducing factor, is a cytokine that induces T and NK cells to produce IFN-γ. In this study, we demonstrated that an rVACV expressing bioactive murine IL-18 replicated to low but detectable levels in vivo, unlike an rVACV expressing IFN-γ. Moreover, the rVACV expressing IL-18 was significantly attenuated in both immunocompromised and immunocompetent mice. This attenuation was dependent on IFN-γ, as IL-18 expression failed to attenuate VACV in IFN-γ knock-out mice. Cytotoxic T-cell (CTL) and anamnestic antibody responses were slightly increased in animals vaccinated with the rVACV expressing IL-18. Thus, induction of IFN-γ because of IL-18 expression resulted in an rVACV that replicated to low but detectable levels in vivo, yet elicited slightly better CTL and anamnestic humoral immune responses.

Expression of Equine Interleukin-18 by Baculovirus Expression System and Its Biologic Activity

The equine interleukin-18 (IL-18) cDNA that contains the coding sequence was cloned and a recombinant baculovirus, named AcEIL-18, was constructed. The recombinant protein of the equine IL-18 was expressed by AcEIL-18 and its expression was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. Insect cells infected with AcEIL-18 secreted a precursor IL-18 with 24 kilo dalton (kDa) into the culture supernatant. Western blot analysis showed that mature equine IL-18 about 18 kDa was also confirmed without co-expression of caspase-1. Culture supernatant from AcEIL-18 infected cells showed a synergistic effect with recombinant human interleukin-12 for induction of interferon-gamma gene expression in equine peripheral mononuclear cells, indicating that the recombinant equine IL-18 expressed in this study also has biological activity without any treatment.

Protective and anti-pathology effects of Sm fructose-1,6-bisphosphate aldolase-based DNA vaccine against schistosoma mansoni by changing route of injection

This study aimed to evaluate the efficacy of fructose-1,6-bis phosphate aldolase (SMALDO) DNA vaccination against Schistosoma mansoni infection using different routes of injection. The SMALDO has been cloned into the eukaryotic expression vector pcDNA3.1/V5-His TOPO-TA and was used in injecting Swiss albino mice intramuscularly (IM), subcutaneously (SC), or intraperitoneally (IP) (50 µg/mouse). Mice vaccinated with non-recombinant pcDNA3.1 served as controls. Each group was immunized 4 times at weeks 0, 2, 4, and 6. Two weeks after the last booster dose, all mice groups were infected with 80 S. mansoni cercariae via tail immersion. At week 8 post-infection, animals were sacrificed for assessment of parasitological and histopathological parameters. High anti-SMALDO IgG antibody titers were detected in sera of all vaccinated groups (P<0.01) compared to the control group. Both the IP and SC vaccination routes resulted in a significant reduction in worm burden (46.2% and 28.9%, respectively, P<0.01). This was accompanied by a significant reduction in hepatic and intestinal egg counts (41.7% and 40.2%, respectively, P<0.01) in the IP group only. The number of dead eggs was significantly increased in both IP and IM groups (P<0.01). IP vaccination recorded the highest significant reduction in granuloma number and diameter (54.7% and 29.2%, respectively, P<0.01) and significant increase in dead miracidia (P<0.01). In conclusion, changing the injection route of SMALDO DNA vaccination significantly influenced the efficacy of vaccination. SMALDO DNA vaccination via IP route could be a promising protective and anti-pathology vaccine candidate against S. mansoni infection.

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.

Expression of bovine (Bos indicus) interleukin-18 in Escherichia coli and its biological activity

IL-18 modulates immune functions by inducing IFN-γ production and promoting Th1 immune responses. In the present study, we amplified and cloned the sequence (582 bp) encoding full-length bovine IL-18 from PBMC stimulated with PHA. The nucleotide and the deduced amino acid sequence of Bos indicus IL-18 showed an identity of 86-98% compared with IL-18 sequences of other ruminants. The insert was subcloned into a pET 32a vector and expressed in Escherichia coli as a fusion protein and the matured protein was obtained by caspase I treatment. The specificity of these proteins was confirmed by western blotting. The biological activity of the purified protein was analyzed by its ability to induce IFN-γ production in PBMC measured by ELISA and qPCR.

Schistosoma japonicum: protective immunity induced by schistosomulum-derived cells in a mouse model

We previously reported that immunization with intact live cells from schistosomula of Schistosoma japonicum (S.j) partially protected the Kunming strain of mice from challenge infection. In the present work, 2 immune protective experiments were designed to further validate the protective effect induced by this type of vaccine and to optimize the immunization protocol, including the number of inoculations and parasite stages from which immunogenic cells were derived. Three antigens derived from 18-day-old postinfection live (LLC) and dead (DLC) larval worm cells and from dead 42-day-old postinfection adult worm cells (DAC) were used as immunogens. Our results demonstrate that live cells from 18-day-old worms are capable of inducing significant protection in mice using a murine-Sj challenge model as shown by reduction rates of worm recoveries and egg burdens. The development of adult worms was stunted. A Th1-biased immune response was reflected in the protected groups as evidenced by the ratio of IgG2a/IgG1. A 38-kDa polypeptide was recognized by sera from LLC immunized animals. We demonstrate that live parasite cells are a source of novel protective antigens that can be exploited for vaccine development.

Review: novel nonviral delivery approaches for interleukin-12 protein and gene systems: curbing toxicity and enhancing adjuvant activity

It has become increasingly apparent that the ability to generate an optimal host immune response requires effective cross talk between the innate and adaptive components of the immune system. Pro-inflammatory cytokines, in particular those that can induce a danger signal, often called signal 3, are crucial in this role of initiating and augmenting the presentation of exogenous antigen to T cells by dendritic cells. Interleukin-12 (IL-12) in particular has been defined as a "signal 3" cytokine required for the antigen cross priming. Given this unique interactive function, a significant amount of work has been performed to define possible therapeutic applications for IL-12. Systemic IL-12 administration can clearly act as a potent adjuvant for postvaccination T cell responses in a variety of diseases. As an example, in the cancer setting, systemic IL-12 is capable of suppressing tumor growth, metastasis, and angiogenesis in vivo. IL-12, however, has been associated with significant dose- and schedule-dependent toxicity in early clinical trials, results that have proven to be a major obstacle to its clinical application. Recent research has focused on decreasing the toxicity of IL-12 using different delivery approaches, including virus-based and gene-modified cell-based delivery. Although effective, these approaches also have limitations, including the generation of neutralizing antibodies, in addition to lacking the simplicity and versatility required for universal clinical application. Thus, there is a significant interest in the development of alternative delivery approaches for IL-12 administration that can overcome these issues. Several nonviral delivery approaches for IL-12 protein or gene expression vectors are being defined, including alum, liposomes, and polymer-based delivery. These developing approaches have shown promising adjuvant effects with significantly lessened systemic toxicity. This article discusses the potential capabilities of these nonvirus-based IL-12 delivery systems in different disease settings, including allergy, infection, and cancer.

Ex vivo Culture with Interleukin (IL)-12 Improves CD8+ T-Cell Adoptive Immunotherapy for Murine Leukemia Independent of IL-18 or IFN-γ but Requires Perforin

In animal models and clinical trials, adoptive transfer of activated, antigen-specific CD8+ T cells mediates tumor regression in a cell dose-dependent manner. The cytokine interleukin (IL)-12 promotes CD8+ T-cell cytotoxicity and, with IL-18, synergistically up-regulates IFN-γ release. We have shown that culturing CD8+ T cells ex vivo with IL-12 and IL-18 enhanced antitumor responses in vivo and in vitro using a model of C1498/ovalbumin, a murine acute myeloid leukemia cell line expressing the antigen ovalbumin. Activated ovalbumin-specific CD8+ T cells cultured with IL-12, IL-18, both, or neither were assayed for antigen-specific cytokine production and cytolytic activity and adoptively transferred to C57BL/6 mice with established tumors. Maximal IFN-γ release occurred after T-cell culture with IL-12 and IL-18. Tumor-specific in vitro cytotoxicity was enhanced by IL-12, unaffected by addition of IL-18, and abrogated in perforin-deficient T cells irrespective of cytokine exposure. T cells cultured with IL-12 more effectively eliminated tumors, and addition of IL-18 did not further augment responses. IFN-γ-deficient CD8+ T cells showed effective antitumor activity that was enhanced by IL-12 with or without IL-18. Perforin-deficient CD8+ T cells were poor mediators of antitumor activity, though, and showed no improvement after culture with IL-12 and/or IL-18. Thus, ex vivo culture with IL-12 was sufficient to augment antigen-specific in vitro cytotoxicity and antitumor activity in vivo in an IFN-γ-independent but perforin-dependent manner. Ex vivo culture with IL-12 may improve CD8+ T-cell immunotherapy of cancer in the absence of donor cell–derived IFN-γ via perforin-mediated cytolysis. (Cancer Res 2006; 66(9): 4913-21)

An interferon gamma-gp120 fusion delivered as a DNA vaccine induces enhanced priming

Nucleic acid vaccination has many potential advantages over traditional methods, but suffers from the fact that DNA vaccines tend to be relatively poorly immunogenic. Attempts to enhance DNA vaccine immunogenicity have included the addition of cytokine-encoding plasmids into the formulation, as well as the use of heterologous prime-boost regimes and the addition of conventional adjuvants, such as alum. We have previously shown that interferon gamma fusions have enhanced immunogenicity as recombinant protein vaccines. We have assessed here the immunogenicity of an interferon gamma-gp120 fusion delivered as a DNA vaccine, in the context of a prime-boost strategy and in the presence of absence of aluminium phosphate. Fusion of gp120 DNA to interferon gamma-encoding DNA resulted in strongly enhanced priming, especially of Th1 responses, including IgG2a responses to a protein boost.

The cytoskeleton and motor proteins of human schistosomes and their roles in surface maintenance and host-parasite interactions

Schistosomes are parasitic blood flukes, responsible for significant human disease in tropical and developing nations. Here we review information on the organization of the cytoskeleton and associated motor proteins of schistosomes, with particular reference to the organization of the syncytial tegument, a unique cellular adaptation of these and other neodermatan flatworms. Extensive EST databases show that the molecular constituents of the cytoskeleton and associated molecular systems are likely to be similar to those of other eukaryotes, although there are potentially some molecules unique to schistosomes and platyhelminths. The biology of some components, particular those contributing to host-parasite interactions as well as chemotherapy and immunotherapy are discussed. Unresolved questions in relation to the structure and function of the tegument relate to dynamic organization of the syncytial layer.

IL-12 enhances protective immunity in mice engendered by immunization with recombinant 14 kDa Schistosoma mansoni fatty acid-binding protein through an IFN-gamma and TNF-alpha dependent pathway

Herein, we tested the ability of IL-12 to enhance protection induced by recombinant Sm14 (rSm14). Mice immunization with three doses of 25 microg of rSm14 was able to induce 25% of protection in mice against challenge. However, co-administration of exogenous IL-12 enhanced protective immunity engendered by rSm14 from 25 to 42.2%. Higher levels of IgG2a and TNF-alpha were observed in mice immunized with rSm14 plus IL-12 compared to animals vaccinated with rSm14 alone. Regarding other cytokines, significant amounts of IFN-gamma were measured in splenocyte culture supernatants of rSm14/IL-12 or rSm14 vaccinated mice and no IL-4 was detected. In an attempt to determine the role of IFN-gamma and TNF-alpha in IL-12 induced immunity, IFN-gamma and TNFR-p55 knockout mice were immunized with rSm14/IL-12 and no protection was achieved. Therefore, protection induced by rSm14/IL-12 was shown to be dependent on endogenous IFN-gamma and TNF-alpha. Although, rSm14 immunization induced partial protection, reduction of hepatic granuloma area was only observed when IL-12 was co-administered.

Persistent high plasma levels of interleukins 18 and 4 in children with recurrent infections of the upper respiratory tract

The aim of this study was to examine whether children with recurrent infections of the upper respiratory tract might have alterations in the systemic immune response to viral infections as compared with healthy control children. We quantitated plasma levels of interferon-gamma, interleukin-12, interleukin-18, interleukin-4, lymphocyte subpopulations, serum immunoglobulins, and subclasses of immunoglobulin G in 30 children under the age of 6 years with recurrent infections of the upper respiratory tract, both during the acute phase of the infection and 4 weeks later, when clinical symptoms had resolved, as well as in 20 normal controls. We found elevated levels of immunoglobulin G primarily due to increased levels of immunoglobulin G(1). Moreover, significantly higher levels of interleukin-18 and interleukin-4 were noted during the acute phase of infection among children with an increased incidence of respiratory infections as compared with the controls (P =.022 and P =.0001, respectively), while plasma levels of interferon-gamma and interleukin-12 were significantly lower (P =.034 and P =.0001, respectively) than in controls. We suggest that an imbalance between T-cell helper type-1 and T-cell helper type-2 immune responses might be responsible for the perpetuation of recurrent infections of the upper respiratory tract.

Interleukin-18 plays a role in both the alum-induced T helper 2 response and the T helper 1 response induced by alum-adsorbed interleukin-12

Previous studies have shown that the antigen-specific T helper 2 (Th2) response induced by alum adjuvants is interleukin (IL)-4 independent. As a role for IL-18 in Th2 induction has recently been described, in addition to its role in enhancing Th1 responses, we have studied the Th2 response induced by ovalbumin (OVA) adsorbed to alum in wild-type and IL-18-deficient mice. Our results indicate that while endogenous IL-18 facilitates alum-induced IL-4 production, OVA-specific immunoglobulin G1 (IgG1) and IgE production remain unaffected. Furthermore, antigen-specific Th1 responses induced with alum/IL-12-adsorbed OVA were demonstrated to be highly IL-18 dependent. Despite these observations, injection of BALB/c mice with exogenous IL-18 adsorbed to alum/OVA did not alter IL-4 or interferon-gamma production by T cells and had little effect on the relative production of IgG1/IgG2a antibody subclasses compared with alum/OVA inoculated mice. However, the previously described synergism between IL-12 and IL-18 in Th1 induction was evident as the Th1-promoting activity of alum/IL-12 against adsorbed OVA was greatly augmented by the coadministration of IL-18. These results indicate that while alum-induced IL-18 can facilitate Th2 induction, the addition of exogenous IL-18 cannot further enhance the alum-induced Th2 response.

Expression of IL-18 by SIV does not modify the outcome of the antiviral immune response

Interleukin 18 (IL-18) is a proinflammatory cytokine expressed by several cell types, including activated dendritic cells and macrophages, that acts in synergy with IL-12 as an important amplifying factor for IFN-gamma production and Th1 development. To study the immunological and virological effects of IL-18 expression in the context of a lentiviral infection, we inoculated rhesus macaques with a high dose of replication-competent simian immunodeficiency virus (SIV) vectors carrying the rhesus IL-18 gene in the sense (SIV(IL-18)) or antisense (SIV(FIGI)) orientation. Both vectors behaved as attenuated viruses, resulting in low viral loads, induction of low and transient levels of inflammatory cytokines, no CD4(+) T cell depletion, and mild activation of T lymphocytes. Although IL-18-expressing virus could be isolated from some SIV(IL18)-infected macaques for 12 weeks postinfection, the anti-SIV humoral and cellular immune responses of macaques inoculated with SIV(IL18) and SIV(FIGI) were similar to each other, with the exception of an early IFN-gamma response in animals infected with SIV(IL18). In summary, expression of IL-18 during the acute phase of SIV infection does not increase viral replication or influence the outcome of the antiviral immune response.

Porcine interleukin-12 fusion protein and interleukin-18 in combination induce interferon-gamma production in porcine natural killer and T cells

A pcDNA3 vector containing a gene encoding a porcine interleukin-12 (poIL-12) fusion protein was constructed, with the p40 chain and its signal peptide positioned first, followed by a linker and the p35 domain. When expressed in COS cells, secreted poIL-12 fusion protein showed high activity in terms of ability to induce interferon-gamma (IFN-gamma) production in porcine peripheral blood mononuclear cells (PBMCs) in vitro. The IFN-gamma production induced by poIL-12 fusion protein, as well as heterodimeric poIL-12 and human IL-12, was markedly dependent on the presence of human IL-18 (huIL-18). Furthermore, huIL-18 showed a dose-dependent induction of IFN-gamma production in PBMC in the presence of a constant concentration of huIL-12. A marked synergism between poIL-12 and IL-18 was consequently observed in poPBMC. The actual IFN-gamma producing cells were identified as probable NK cells (about 30%) and T lymphocytes (about 70%), using flow cytometry. Furthermore, a histidine-tagged poIL-12 fusion protein was expressed in Drosophila melanogaster Schneider 2 cells, using a modified pMT/V5-His vector lacking the V5 epitope. Such poIL-12 fusion protein was easily purified using Ni-NTA agarose and retained high biological activity.

Cellular and humoral immune responses and protection against schistosomes induced by a radiation-attenuated vaccine in chimpanzees

The radiation-attenuated Schistosoma mansoni vaccine is highly effective in rodents and primates but has never been tested in humans, primarily for safety reasons. To strengthen its status as a paradigm for a human recombinant antigen vaccine, we have undertaken a small-scale vaccination and challenge experiment in chimpanzees (Pan troglodytes). Immunological, clinical, and parasitological parameters were measured in three animals after multiple vaccinations, together with three controls, during the acute and chronic stages of challenge infection up to chemotherapeutic cure. Vaccination induced a strong in vitro proliferative response and early gamma interferon production, but type 2 cytokines were dominant by the time of challenge. The controls showed little response to challenge infection before the acute stage of the disease, initiated by egg deposition. In contrast, the responses of vaccinated animals were muted throughout the challenge period. Vaccination also induced parasite-specific immunoglobulin M (IgM) and IgG, which reached high levels at the time of challenge, while in control animals levels did not rise markedly before egg deposition. The protective effects of vaccination were manifested as an amelioration of acute disease and overall morbidity, revealed by differences in gamma-glutamyl transferase level, leukocytosis, eosinophilia, and hematocrit. Moreover, vaccinated chimpanzees had a 46% lower level of circulating cathodic antigen and a 38% reduction in fecal egg output, compared to controls, during the chronic phase of infection.

Expression of the interleukin-18 gene from rhesus macaque by the simian immunodeficiency virus does not result in increased viral replication

Interleukin-18 (IL-18), previously known as interferon-gamma (IFN-gamma)-inducing factor (IGIF), is a proinflammatory cytokine expressed by activated macrophages that acts in synergy with IL-12 as an important amplifying factor for IFN-gamma production and Th1 development. To study the effect of IL-18 on a lentiviral infection, we cloned the IL-18 gene from a rhesus macaque and constructed replication-competent simian immunodeficiency virus (SIV) that expressed either the precursor pro-IL-18 (SIV(IL-18)) or the mature form (SIV(mIL-18)) of IL-18. The predicted amino acid sequence for rhesus IL-18 had 96% homology with the human one, differing in only 8 of 193 residues. SIV(IL-18) and SIV(mIL-18) replicated more slowly than control viruses in the CEM x 174 cell line and resulted in the development of chronically infected cell lines that expressed high levels of infectious SIV. The cell line generated by SIV(IL-18) released large quantities of IL-18 into the supernatant, whereas the one obtained from SIV(mIL-18) showed the accumulation of IL-18 in the cytoplasm. Similarly, SIV(IL-18) and SIV(mIL-18) replicated more slowly than the unmodified viral vector in rhesus peripheral blood mononuclear cells (PMBC), but only SIV(IL-18) expressed biologically active IL-18. These experiments show that the precursor form of IL-18 is necessary for the efficient release of the cytokine and that IL-18 does not promote increased replication of SIV in rhesus PBMC.

Efficient production of biologically active porcine interleukin-18 by coexpression with porcine caspase-1 using a baculovirus expression system

We previously reported that the precursor form of porcine interleukin-18 (IL-18) expressed by the baculovirus system was able to be secreted efficiently into the supernatant of insect cells, whereas only small amounts of mature IL-18 were secreted from insect cells. As insect cells do not normally have the IL-1beta converting enzyme (caspase-1), which is required for processing of the precursor IL-18 into the mature IL-18, we recently cloned porcine caspase-1 cDNA. In this study, we constructed a recombinant baculovirus containing the cDNA encoding porcine caspase-1 and showed that the coexpression of caspase-1 and the precursor IL-18 enabled insect cells to secrete mature IL-18 into the culture supernatant efficiently. Moreover, inhibition of caspase-1 activity by its specific inhibitor prevented the processing of precursor IL-18 into the mature form. These results indicated that the processing and secretion of precursor IL-18 into the mature form in insect cells were enhanced by the artificial introduction of caspase-1 activity for cleavage.

Immunostimulatory effect of IL-18-encoding plasmid in DNA vaccination against murine Schistosoma mansoni infection

In vivo delivery of DNA encoding antigens is a simple tool to induce immune responses against pathogens. This approach to vaccination also offers the possibility to codeliver plasmids encoding immunomodulatory molecules in order to drive immune responses towards optimal protective effects. In the murine model of Schistosoma mansoni infection, vaccination inducing a Th1 profile has been shown to be protective. In this study, we used a plasmid encoding the Th1-promoting cytokine IL-18, since we observed that percutaneous infection of Balb/c mice strongly induced the production of IL-18 mRNA in the skin. Intradermal injection of the IL-18-encoding plasmid prior to infection did not interfere with parasite migration through the skin although it led to a local and transient cellular infiltration. When the IL-18-encoding plasmid was codelivered with a S. mansoni glutathione S-transferase (Sm28GST)-encoding plasmid, a 30-fold increase of antigen-specific IFN-gamma secretion by spleen cells was observed in comparison to spleen cells from mice that had received only the Sm28GST-encoding plasmid. This immunostimulatory effect was related to a significant protective effect (28% reduction in egg laying and 23% reduction in worm burden) which was attributed to a cooperative effect between both plasmids. Therefore, this study shows that codelivery of an IL-18-encoding plasmid with an antigen-encoding plasmid can stimulate specific cellular responses and induce protective effects against S. mansoni infection.