Interleukin-12 as an adjuvant for induction of protective antibody responses

Adjuvantation of a SARS-CoV-2 mRNA vaccine with controlled tissue-specific expression of an mRNA encoding IL-12p70

Messenger RNA (mRNA) vaccines were pivotal in reducing severe acute respiratory syndrome 2 (SARS-CoV-2) infection burden, yet they have not demonstrated robust durability, especially in older adults. Here, we describe a molecular adjuvant comprising a lipid nanoparticle (LNP)-encapsulated mRNA encoding interleukin-12p70 (IL-12p70). The bioactive adjuvant was engineered with a multiorgan protection (MOP) sequence to restrict transcript expression to the intramuscular injection site. Admixing IL-12-MOP (CTX-1796) with the BNT162b2 SARS-CoV-2 vaccine increased spike protein-specific immune responses in mice. Specifically, the benefits of IL-12-MOP adjuvantation included amplified humoral and cellular immunity and increased immune durability for 1 year after vaccination in mice. An additional benefit included the restoration of immunity in aged mice to amounts comparable to those achieved in young adult animals, alongside amplification with a single immunization. Associated enhanced dendritic cell and germinal center responses were observed. Together, these data demonstrate that an LNP-encapsulated IL-12-MOP mRNA-encoded adjuvant can amplify immunogenicity independent of age, demonstrating translational potential to benefit vulnerable populations.

Promising Cytokine Adjuvants for Enhancing Tuberculosis Vaccine Immunity

Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), remains a formidable global health challenge, affecting a substantial portion of the world's population. The current tuberculosis vaccine, bacille Calmette-Guérin (BCG), offers limited protection against pulmonary tuberculosis in adults, underscoring the critical need for innovative vaccination strategies. Cytokines are pivotal in modulating immune responses and have been explored as potential adjuvants to enhance vaccine efficacy. The strategic inclusion of cytokines as adjuvants in tuberculosis vaccines holds significant promise for augmenting vaccine-induced immune responses and strengthening protection against M. tuberculosis. This review delves into promising cytokines, such as Type I interferons (IFNs), Type II IFN, interleukins such as IL-2, IL-7, IL-15, IL-12, and IL-21, alongside the use of a granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant, which has shown effectiveness in boosting immune responses and enhancing vaccine efficacy in tuberculosis models.

Polymeric Caffeic Acid Acts as an Antigen Delivery Carrier for Mucosal Vaccine Formulation by Forming a Complex with an Antigenic Protein

The development of mucosal vaccines, which can generate antigen-specific immune responses in both the systemic and mucosal compartments, has been recognized as an effective strategy for combating infectious diseases caused by pathogenic microbes. Our recent research has focused on creating a nasal vaccine system in mice using enzymatically polymerized caffeic acid (pCA). However, we do not yet understand the molecular mechanisms by which pCA stimulates antigen-specific mucosal immune responses. In this study, we hypothesized that pCA might activate mucosal immunity at the site of administration based on our previous findings that pCA possesses immune-activating properties. However, contrary to our initial hypothesis, the intranasal administration of pCA did not enhance the expression of various genes involved in mucosal immune responses, including the enhancement of IgA responses. Therefore, we investigated whether pCA forms a complex with antigenic proteins and enhances antigen delivery to mucosal dendritic cells located in the lamina propria beneath the mucosal epithelial layer. Data from gel filtration chromatography indicated that pCA forms a complex with the antigenic protein ovalbumin (OVA). Furthermore, we examined the promotion of OVA delivery to nasal mucosal dendritic cells (mDCs) after the intranasal administration of pCA in combination with OVA and found that OVA uptake by mDCs was increased. Therefore, the data from gel filtration chromatography and flow cytometry imply that pCA enhances antigen-specific antibody production in both mucosal and systemic compartments by serving as an antigen-delivery vehicle.

Recent Advances in the Development of Adenovirus-Vectored Vaccines for Parasitic Infections

Vaccines against parasites have lagged centuries behind those against viral and bacterial infections, despite the devastating morbidity and widespread effects of parasitic diseases across the globe. One of the greatest hurdles to parasite vaccine development has been the lack of vaccine strategies able to elicit the complex and multifaceted immune responses needed to abrogate parasitic persistence. Viral vectors, especially adenovirus (AdV) vectors, have emerged as a potential solution for complex disease targets, including HIV, tuberculosis, and parasitic diseases, to name a few. AdVs are highly immunogenic and are uniquely able to drive CD8+ T cell responses, which are known to be correlates of immunity in infections with most protozoan and some helminthic parasites. This review presents recent developments in AdV-vectored vaccines targeting five major human parasitic diseases: malaria, Chagas disease, schistosomiasis, leishmaniasis, and toxoplasmosis. Many AdV-vectored vaccines have been developed for these diseases, utilizing a wide variety of vectors, antigens, and modes of delivery. AdV-vectored vaccines are a promising approach for the historically challenging target of human parasitic diseases.

The potential of a universal influenza virus-like particle vaccine expressing a chimeric cytokine

The efficacy of the current influenza vaccines is frequently reduced because of antigenic drift, a trade-off of developing improved vaccines with broad cross-protective activity against influenza A viruses. In this study, we have successfully constructed a chimeric cytokine (CC) comprising the M2 protein, influenza A neuraminidase stalk, and interleukin-12. We produced virus-like particles (VLPs) containing CC and influenza hemagglutinin (HA) proteins using a baculovirus system in Eri silkworm pupae. The protective efficacy of the CCHA-VLP vaccine was evaluated in mice. The CCFkH5HA-VLP vaccine increased the survival rates of BALB/c mice, infected with a lethal dose of PRH1 and HKH5 viruses, to 80% and 100%, respectively. The results suggested that CCHA-VLP successfully induced potent cross-reactive protective immunity against infection with homologous and heterologous subtypes of the influenza A virus. This is the first study to design a CC-containing HA-VLP vaccine and validate its protective efficacy.

STING and TLR7/8 agonists-based nanovaccines for synergistic antitumor immune activation

Immunostimulatory therapies based on pattern recognition receptors (PRRs) have emerged as an effective approach in the fight against cancer, with the ability to recruit tumor-specific lymphocytes in a low-immunogenicity tumor environment. The agonist cyclic dinucleotides (CDNs) of the stimulator of interferon gene (STING) are a group of very promising anticancer molecules that increase tumor immunogenicity by activating innate immunity. However, the tumor immune efficacy of CDNs is limited by several factors, including relatively narrow cytokine production, inefficient delivery to STING, and rapid clearance. In addition, a single adjuvant molecule is unable to elicit a broad cytokine response and thus cannot further amplify the anticancer effect. To address this problem, two or more agonist molecules are often used together to synergistically enhance immune efficacy. In this work, we found that a combination of the STING agonist CDG^SF and the Toll-like receptor 7/8 (TLR7/8) agonist 522 produced a broader cytokine response. Subsequently, we developed multicomponent nanovaccines (MCNVs) consisting of a PC7A polymer as a nanocarrier encapsulating the antigen OVA and adjuvant molecules. These MCNVs activate bone marrow-derived dendritic cells (BMDCs) to produce multiple proinflammatory factors that promote antigen cross-presentation to stimulate specific antitumor T-cell responses. In in vivo experiments, we observed that MCNVs triggered a strong T-cell response in tumor-infiltrating lymphocytes, resulting in significant tumor regression and, notably, a 100% survival rate in mice through 25 days without other partnering therapies. These data suggest that our nanovaccines have great potential to advance cancer immunotherapy with increased durability and potency.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (synthesis of CDG^SF, 522, PC7A and OVA; preparation of MCNVs; representative gating strategies for flow cytometry) is available in the online version of this article at 10.1007/s12274-022-4282-x.

Vaccine Candidates for the Control and Prevention of the Sexually Transmitted Disease Gonorrhea

The World Health Organization (WHO) has placed N. gonorrhoeae on the global priority list of antimicrobial resistant pathogens and is urgently seeking the development of new intervention strategies. N. gonorrhoeae causes 86.9 million cases globally per annum. The effects of gonococcal disease are seen predominantly in women and children and especially in the Australian Indigenous community. While economic modelling suggests that this infection alone may directly cost the USA health care system USD 11.0–20.6 billion, indirect costs associated with adverse disease and pregnancy outcomes, disease prevention, and productivity loss, mean that the overall effect of the disease is far greater still. In this review, we summate the current progress towards the development of a gonorrhea vaccine and describe the clinical trials being undertaken in Australia to assess the efficacy of the current formulation of Bexsero^® in controlling disease.

Dynamics of SARS-CoV-2 neutralising antibody responses and duration of immunity: a longitudinal study

Background

Studies have found different waning rates of neutralising antibodies compared with binding antibodies against SARS-CoV-2. The impact of neutralising antibody waning rate at the individual patient level on the longevity of immunity remains unknown. We aimed to investigate the peak levels and dynamics of neutralising antibody waning and IgG avidity maturation over time, and correlate this with clinical parameters, cytokines, and T-cell responses.

Methods

We did a longitudinal study of patients who had recovered from COVID-19 up to day 180 post-symptom onset by monitoring changes in neutralising antibody levels using a previously validated surrogate virus neutralisation test. Changes in antibody avidities and other immune markers at different convalescent stages were determined and correlated with clinical features. Using a machine learning algorithm, temporal change in neutralising antibody levels was classified into five groups and used to predict the longevity of neutralising antibody-mediated immunity.

Findings

We approached 517 patients for participation in the study, of whom 288 consented for outpatient follow-up and collection of serial blood samples. 164 patients were followed up and had adequate blood samples collected for analysis, with a total of 546 serum samples collected, including 128 blood samples taken up to 180 days post-symptom onset. We identified five distinctive patterns of neutralising antibody dynamics as follows: negative, individuals who did not, at our intervals of sampling, develop neutralising antibodies at the 30% inhibition level (19 [12%] of 164 patients); rapid waning, individuals who had varying levels of neutralising antibodies from around 20 days after symptom onset, but seroreverted in less than 180 days (44 [27%] of 164 patients); slow waning, individuals who remained neutralising antibody-positive at 180 days post-symptom onset (46 [28%] of 164 patients); persistent, although with varying peak neutralising antibody levels, these individuals had minimal neutralising antibody decay (52 [32%] of 164 patients); and delayed response, a small group that showed an unexpected increase of neutralising antibodies during late convalescence (at 90 or 180 days after symptom onset; three [2%] of 164 patients). Persistence of neutralising antibodies was associated with disease severity and sustained level of pro-inflammatory cytokines, chemokines, and growth factors. By contrast, T-cell responses were similar among the different neutralising antibody dynamics groups. On the basis of the different decay dynamics, we established a prediction algorithm that revealed a wide range of neutralising antibody longevity, varying from around 40 days to many decades.

Interpretation

Neutralising antibody response dynamics in patients who have recovered from COVID-19 vary greatly, and prediction of immune longevity can only be accurately determined at the individual level. Our findings emphasise the importance of public health and social measures in the ongoing pandemic outbreak response, and might have implications for longevity of immunity after vaccination.

Funding

National Medical Research Council, Biomedical Research Council, and A*STAR, Singapore.

Immune effect of a Newcastle disease virus DNA vaccine with IL-12 as a molecular adjuvant delivered by electroporation

Newcastle disease (ND), caused by virulent Newcastle disease virus (NDV) strains, has been one of the most problematic diseases affecting the poultry industry worldwide. Conventional vaccines provide effective protection for birds to survive ND outbreaks, but they may not completely suppress NDV shedding. NDV strains circulate on farms for a long time after the initial infection and cause potential risks. A new vaccine with fast clearance ability and low viral shedding is needed. In this study, we used interleukin-12 (IL-12) as an adjuvant and electroporation (EP) as an advanced delivery system to improve a DNA vaccine candidate. The fusion (F) protein gene from an NDV strain of the prevalent genotype VII.1.1 was cloned to prepare the vaccine. Chickens immunized with the F gene DNA vaccine co-delivered with an IL-12-expressing plasmid DNA showed higher neutralizing antibody levels and stronger concanavalin-A-induced lymphocyte proliferation than those treated with the F gene DNA vaccine alone. The co-delivered vaccine provided 100% protection, and less viral shedding and a shorter release time were observed in challenged chickens than when the F gene DNA vaccine was administered alone. The use of F gene DNA combined with IL-12 delivered by electroporation is a promising approach for vaccination against ND.

Altered immune system in frailty: Genetics and diet may influence inflammation

Frailty is a complex geriatric syndrome associated with biological vulnerability to stressors and decreased physiological reserve. Its etiology and pathogenesis are not completely understood, although various causes and complex pathways have been proposed. Immune system alterations (immunosenescence and "InflammAging") have been suggested to contribute to frailty, but a precise causative role of such alterations remains to be determined. Genetic studies support the suggestion of immune system involvement in frailty: genetic variants in genes involved in immune system function have been associated with the syndrome. Interestingly, nutritional status, through its effects on cellular metabolism, may also influence the immune system, i.e. hormone and cytokine (mainly adipocytokine) levels, and immune cell populations and function, increasing inflammation and contributing to frailty. This review aims to discuss the role of immune system alterations in frailty, analyzing the role of genetic factors in frailty onset and the impact of diet on inflammation and, in turn, on frailty.

Evaluation on the efficacy and immunogenicity of recombinant DNA plasmids expressing S gene from porcine epidemic diarrhea virus and VP7 gene from porcine rotavirus

Porcine rotavirus (PoRV) and porcine epidemic diarrhea virus (PEDV) usually co-infect pigs in modern large-scale piggery, which both can cause severe diarrhea in newborn piglets and lead to significant economic losses to the pig industry. The VP7 protein is the main coat protein of PoRV, and the S protein is the main structural protein of PEDV, which are capable of inducing neutralizing antibodies in vivo. In this study, a DNA vaccine pPI-2.EGFP.VP7.S co-expressing VP7 protein of PoRV and S protein of PEDV was constructed. Six 8-week-old mice were immunized with the recombinant plasmid pPI-2.EGFP.VP7.S. The high humoral immune responses (virus specific antibody) and cellular immune responses (IFN-γ, IL-4, and spleen lymphocyte proliferation) were evaluated. The immune effect through intramuscular injection increased with plasmid dose when compared with subcutaneous injection. The immune-enhancing effect of IFN-α adjuvant was excellent compared with pig spleen transfer factor and IL-12 adjuvant. These results demonstrated that pPI-2.EGFP.VP7.S possess the immunological functions of the VP7 proteins of PoRV and S proteins of PEDV, indicating that pPI-2.EGFP.VP7.S is a candidate vaccine for porcine rotaviral infection (PoR) and porcine epidemic diarrhea (PED).

Acetalated Dextran Microparticles for Codelivery of STING and TLR7/8 Agonists

Vaccines are the most effective tool for preventing infectious diseases; however, subunit vaccines, considered the safest type, suffer from poor immunogenicity and require adjuvants to create a strong and sustained immune response. As adjuvants, pathogen-associated molecular patterns (PAMPs) offer potent immunostimulatory properties and defined mechanisms of action through their cognate pattern recognition receptors (PRRs). Their activity can be further enhanced through combining two or more PAMPs, particularly those that activate multiple immune signaling pathways. However, the cytosolic localization of many PRRs requires intracellular delivery of PAMPs for optimal biological activity, which is particularly true of the stimulator of interferon genes (STING) PRR. Using acetalated dextran (Ace-DEX) microparticles (MPs) encapsulating STING agonist 3'3'-cyclic GMP-AMP (cGAMP) combined with soluble PAMPS, we screened the effect of codelivery of adjuvants using primary mouse bone marrow derived dendritic cells (BMDCs). We identified that codelivery of cGAMP MPs and soluble Toll-like receptor 7/8 (TLR7/8) agonist resiquimod (R848) elicited the broadest cytokine response. cGAMP and R848 were then coencapsulated within Ace-DEX MPs via electrospray. Using the model antigen ovalbumin, we observed that Ace-DEX MPs coencapsulating cGAMP and R848 (cGAMP/R848 Ace-DEX MPs) induced antigen-specific cellular immunity, and a balanced Th1/Th2 humoral response that was greater than cGAMP Ace-DEX MPs alone and PAMPs delivered in separate MPs. These data indicate that polymeric Ace-DEX MPs loaded with STING and TLR7/8 agonists represent a potent cellular and humoral vaccine adjuvant.

Experimental vaccine induces Th1-driven immune responses and resistance to Neisseria gonorrhoeae infection in a murine model

Female mice were immunized intravaginally with gonococcal outer membrane vesicles (OMVs) plus microencapsulated interleukin-12 (IL-12), and challenged using an established model of genital infection with Neisseria gonorrhoeae. Whereas sham-immunized and control animals cleared the infection in 10-13 days, those immunized with OMV plus IL-12 cleared infection with homologous gonococcal strains in 6-9 days. Significant protection was also seen after challenge with antigenically distinct strains of N. gonorrhoeae, and protective anamnestic immunity persisted for at least 6 months after immunization. Serum and vaginal immunoglobulin G (IgG) and IgA antibodies were generated against antigens expressed by homologous and heterologous strains. Iliac lymph node CD4⁺ T cells secreted interferon-γ (IFNγ), but not IL-4, in response to immunization, and produced IL-17 in response to challenge regardless of immunization. Antigens recognized by immunized mouse serum included several shared between gonococcal strains, including two identified by immunoproteomics approaches as elongation factor-Tu (EF-Tu) and PotF3. Experiments with immunodeficient mice showed that protective immunity depended upon IFNγ and B cells, presumably to generate antibodies. The results demonstrated that immunity to gonococcal infection can be induced by immunization with a nonliving gonococcal antigen, and suggest that efforts to develop a human vaccine should focus on strategies to generate type 1 T helper cell (Th1)-driven immune responses in the genital tract.

Advances in Studies Related to Interleukin-12 Family and Infectious Diseases

Interleukin (IL)-12 family is a group of cytokines composed of heterogeneous molecules and whose members include IL-12, IL-23, IL-27, and IL-35. IL-12 family bridges natural and adaptive immune responses and especially plays a significant role in classical adaptive immune process participated by TH1, TH17, and Treg cells. Members of IL-12 family participate in adaptive immune responses via the Janus kinase-signal transducers and activators of transcription signaling pathway by sharing some subunits and receptors. IL-12 features an extremely complex regulatory network. During resistance of microbial infection, IL-12 and IL-23 mainly show inflammatory effects, whereas IL-27 and IL-35 commonly show antiinflammatory effects. This study reviews advances in studies related to IL-12 family members and infectious diseases and provides references to further reveal functions of IL-12 family members in occurrence and development of infectious diseases.

Sex, the aging immune system, and chronic disease

The immune systems of men and women differ in significant ways, especially after puberty. In particular, females are generally more prone to autoimmunity, but experience lower rates of infections and chronic inflammatory disease. Sex hormones, genes encoded on the sex chromosomes, and gender-specific behaviors likely contribute to these differences. The aging process is associated with changes in the composition and function of the immune system and these changes may occur at an accelerated rate in men as compared to women. Moreover, after the age of menopause, the incidence of chronic inflammatory disease in women approaches or exceeds that observed in males. At the same time, the incidence of autoimmunity in post-menopausal women is decreased or equivalent to the rates observed in similarly-aged men. Additional studies addressing the influence of sex on the pathogenesis of chronic and autoimmune diseases in the aged are warranted.

IL12Rβ1: the cytokine receptor that we used to know

Human IL12RB1 encodes IL12Rβ1, a type I transmembrane receptor that is an essential component of the IL12- and IL23-signaling complex. IL12RB1 is well-established as being a promoter of delayed type hypersensitivity (DTH), the immunological reaction that limits tuberculosis. However, recent data demonstrate that in addition to promoting DTH, IL12RB1 also promotes autoimmunity. The contradictory roles of IL12RB1 in human health raises the question, what are the factors governing IL12RB1 function in a given individual, and how is inter-individual variability in IL12RB1 function introduced? Here we review recent data that demonstrate individual variability in IL12RB1 function is introduced at the epigenetic, genomic polymorphism, and mRNA splicing levels. Where and how these differences contribute to disease susceptibility and outcome are also reviewed. Collectively, recent data support a model wherein IL12RB1 sequence variability - whether introduced at the genomic or post-transcriptional level - contributes to disease, and that human IL12RB1 is not as simple a gene as we once believed.

Interleukin-21 and T follicular helper cells in HIV infection: research focus and future perspectives

Interleukin (IL)-21 is a member of the γ chain-receptor cytokine family along with IL-2, IL-4, IL-7, IL-9, and IL-15. The effects of IL-21 are pleiotropic, owing to the broad cellular distribution of the IL-21 receptor. IL-21 is secreted by activated CD4 T cells and natural killer T cells. Within CD4 T cells, its secretion is restricted mainly to T follicular helper (Tfh) cells and Th17 cells to a lesser extent. Our research focus has been on the role of IL-21 and more recently of Tfh in immunopathogenesis of HIV infection. This review focuses on first the influence of IL-21 in regulation of T cell, B cell, and NK cell responses and its immunotherapeutic potential in viral infections and as a vaccine adjuvant. Second, we discuss the pivotal role of Tfh in generation of antibody responses in HIV-infected persons in studies using influenza vaccines as a probe. Lastly, we review data supporting ability of HIV to infect Tfh and the role of these cells as reservoirs for HIV and their contribution to viral persistence.

Grouper interleukin-12, linked by an ancient disulfide-bond architecture, exhibits cytokine and chemokine activities

Interleukin-12 (IL-12) is a pleiotropic cytokine which bridges innate and adaptive immunity in defense against pathogens. IL-12 proved to be an effective and successful adjuvant to enhance both the innate and adaptive immune responses and could be applicable for a rationale vaccine formulation in fish against pathogen infection. We have cloned the p35 and p40 cDNAs of IL-12 from orange-spotted grouper (Epinephelus coioides). Grouper IL-12 most resembles with sea bass orthologues; moderate to low identity with other teleost and mammalian counterparts. The structural model of grouper IL-12 heterodimer revealed NC(141)F three amino acid patch of grouper p35, which is present in teleost p35 but absent in mammalian and avian p35, and is spatially nearby the conserved cysteine residue located at A-helix of p35 to form a disulfide bond when the 14aa peptide located at loop 1 of grouper p35 was aligned with human corresponding exon 4, instead of exon 5. The results indicated that the loss of this 3aa patch during evolution was compensated by the duplication of exon 4 in mammalian p35 to gain another cysteine residue to form a disulfide bond, evidenced by chicken p35 which does not contain NCF corresponding 3-aa patch nor exon 4 duplication. Accordingly, the inter-chain disulfide bond of IL-12 heterodimer is conserved from teleost to mammalian IL-12. A single chain grouper IL-12 (scgIL-12) construct linked by (G4S)3 was successfully expressed in baculovirus-insect cell system; its identity has been confirmed by LC/MS/MS. In addition, the biological activity of recombinant scgIL-12 (rscgIL-12) are demonstrated for its stimulation of PBL proliferation, chemotactic migration, induction of TNF-α gene expression and a plausible adjuvant effect of prolonged protection against parasite infection in fish. We illustrated the first time in lower vertebrate that grouper IL-12 possesses both cytokine and chemokine activities.

Neonatal Fc receptor expression in dendritic cells mediates protective immunity against colorectal cancer

Cancers arising in mucosal tissues account for a disproportionately large fraction of malignancies. Immunoglobulin G (IgG) and the neonatal Fc receptor for IgG (FcRn) have an important function in the mucosal immune system that we have now shown extends to the induction of CD8(+) T cell-mediated antitumor immunity. We demonstrate that FcRn within dendritic cells (DCs) was critical for homeostatic activation of mucosal CD8(+) T cells that drove protection against the development of colorectal cancers and lung metastases. FcRn-mediated tumor protection was driven by DCs activation of endogenous tumor-reactive CD8(+) T cells via the cross-presentation of IgG complexed antigens (IgG IC), as well as the induction of cytotoxicity-promoting cytokine secretion, particularly interleukin-12, both of which were independently triggered by the FcRn-IgG IC interaction in murine and human DCs. FcRn thus has a primary role within mucosal tissues in activating local immune responses that are critical for priming efficient anti-tumor immunosurveillance.

Enhancement of adaptive immunity to Neisseria gonorrhoeae by local intravaginal administration of microencapsulated interleukin 12

Gonorrhea remains one of the most frequent infectious diseases, and Neisseria gonorrhoeae is emerging as resistant to most available antibiotics, yet it does not induce a state of specific protective immunity against reinfection. Our recent studies have demonstrated that N. gonorrhoeae proactively suppresses host T-helper (Th) 1/Th2-mediated adaptive immune responses, which can be manipulated to generate protective immunity. Here we show that intravaginally administered interleukin 12 (IL-12) encapsulated in sustained-release polymer microspheres significantly enhanced both Th1 and humoral immune responses in a mouse model of genital gonococcal infection. Treatment of mice with IL-12 microspheres during gonococcal challenge led to faster clearance of infection and induced resistance to reinfection, with the generation of gonococcus-specific circulating immunoglobulin G and vaginal immunoglobulin A and G antibodies. These results suggest that local administration of microencapsulated IL-12 can serve as a novel therapeutic and prophylactic strategy against gonorrhea, with implications for the development of an effective vaccine.

Feline immunodeficiency virus (FIV) vaccine efficacy and FIV neutralizing antibodies

A HIV-1 tier system has been developed to categorize the various subtype viruses based on their sensitivity to vaccine-induced neutralizing antibodies (NAbs): tier 1 with greatest sensitivity, tier 2 being moderately sensitive, and tier 3 being the least sensitive to NAbs (Mascola et al., J Virol 2005; 79:10103-7). Here, we define an FIV tier system using two related FIV dual-subtype (A+D) vaccines: the commercially available inactivated infected-cell vaccine (Fel-O-Vax(®) FIV) and its prototype vaccine solely composed of inactivated whole viruses. Both vaccines afforded combined protection rates of 100% against subtype-A tier-1 FIVPet, 89% against subtype-B tier-3 FIVFC1, 61% against recombinant subtype-A/B tier-2 FIVBang, 62% against recombinant subtype-F'/C tier-3 FIVNZ1, and 40% against subtype-A tier-2 FIVUK8 in short-duration (37-41 weeks) studies. In long-duration (76-80 weeks) studies, the commercial vaccine afforded a combined protection rate of at least 46% against the tier-2 and tier-3 viruses. Notably, protection rates observed here are far better than recently reported HIV-1 vaccine trials (Sanou et al., The Open AIDS J 2012; 6:246-60). Prototype vaccine protection against two tier-3 and one tier-2 viruses was more effective than commercial vaccine. Such protection did not correlate with the presence of vaccine-induced NAbs to challenge viruses. This is the first large-scale (228 laboratory cats) study characterizing short- and long-duration efficacies of dual-subtype FIV vaccines against heterologous subtype and recombinant viruses, as well as FIV tiers based on in vitro NAb analysis and in vivo passive-transfer studies. These studies demonstrate that not all vaccine protection is mediated by vaccine-induced NAbs.

Inflammatory signals direct expression of human IL12RB1 into multiple distinct isoforms

IL12RB1 is essential for human resistance to multiple intracellular pathogens, including Mycobacterium tuberculosis. In its absence, the proinflammatory effects of the extracellular cytokines IL-12 and IL-23 fail to occur, and intracellular bacterial growth goes unchecked. Given the recent observation that mouse leukocytes express more than one isoform from il12rb1, we examined whether primary human leukocytes similarly express more than one isoform from IL12RB1. We observed that human leukocytes express as many as 13 distinct isoforms, the relative levels of each being driven by inflammatory stimuli both in vitro and in vivo. Surprisingly, the most abundant isoform present before stimulation is a heretofore uncharacterized intracellular form of the IL-12R (termed "isoform 2") that presumably has limited contact with extracellular cytokine. After stimulation, primary PBMCs, including the CD4(+), CD8(+), and CD56(+) lineages contained therein, alter the splicing of IL12RB1 RNA to increase the relative abundance of isoform 1, which confers IL-12/IL-23 responsiveness. These data demonstrate both a posttranscriptional mechanism by which cells regulate their IL-12/IL-23 responsiveness, and that leukocytes primarily express IL12RB1 in an intracellular form located away from extracellular cytokine.

Pulmonary macrophage subpopulations in the induction and resolution of acute lung injury

Macrophages are key orchestrators of the inflammatory and repair responses in the lung, and the diversity of their function is indicated by their polarized states and distinct subpopulations and localization in the lung. Here, we characterized the pulmonary macrophage populations in the interstitial and alveolar compartments during the induction and resolution of acute lung injury induced by Pseudomonas aeruginosa infection. We identified macrophage subpopulations and polarity according to FACS analysis of cell surface protein markers, combined with cell sorting for gene expression using real-time PCR. With these techniques, we validated a novel, alternatively activated (M2) marker (transferrin receptor), and we described three interstitial and alveolar macrophage subpopulations in the lung whose distribution and functional state evolved from the induction to resolution phases of lung injury. Together, these findings indicate the presence and evolution of distinct macrophage subsets in the lung that serve specific niches in regulating the inflammatory response and its resolution. Alterations in the balance and function of these subpopulations could lead to nonresolving acute lung injury.

Adjuvants for Leishmania vaccines: from models to clinical application

Two million new cases of leishmaniasis occur every year, with the cutaneous leishmaniasis (CL) presentation accounting for approximately two-thirds of all cases. Despite the high incidence rates and geographic expansion of the disease, CL remains a neglected tropical disease without effective intervention strategies. Efforts to address this deficit have given rise to the experimental murine model of CL. By virtue of its simplicity and pliability, the CL model has been used to provide substantial information regarding cellular immunity, as well as in the discovery and evaluation of various vaccine adjuvants. The CL model has facilitated in vivo studies of the mechanism of action of many adjuvants, including the TLR4 agonist monophosphoryl lipid A, the TLR7/8 agonist imiquimod, the TLR9 agonist CpG, adenoviral vectors, and the immunostimulatory complexes. Together, these studies have helped to unveil the requirement for certain types of immune responses at specific stages of CL disease and provide a basis to aid the design of effective second-generation vaccines for human CL. This review focuses on adjuvants that have been tested in experimental CL, outlining how they have helped advance our understanding of the disease and ultimately, how they have performed when applied within clinical trials against human CL.

Homeostatic regulation of Salmonella-induced mucosal inflammation and injury by IL-23

IL-12 and IL-23 regulate innate and adaptive immunity to microbial pathogens through influencing the expression of IFN-γ, IL-17, and IL-22. Herein we define the roles of IL-12 and IL-23 in regulating host resistance and intestinal inflammation during acute Salmonella infection. We find that IL-23 alone is dispensable for protection against systemic spread of bacteria, but synergizes with IL-12 for optimal protection. IL-12 promotes the production of IFN-γ by NK cells, which is required for resistance against Salmonella and also for induction of intestinal inflammation and epithelial injury. In contrast, IL-23 controls the severity of inflammation by inhibiting IL-12A expression, reducing IFN-γ and preventing excessive mucosal injury. Our studies demonstrate that IL-23 is a homeostatic regulator of IL-12-dependent, IFN-γ-mediated intestinal inflammation.

Small heat shock protein αA-crystallin prevents photoreceptor degeneration in experimental autoimmune uveitis

The small heat shock protein, αA-crystallin null (αA−/−) mice are known to be more prone to retinal degeneration than the wild type mice in Experimental Autoimmune Uveoretinitis (EAU). In this report we demonstrate that intravenous administration of αA preserves retinal architecture and prevents photoreceptor damage in EAU. Interestingly, only αA and not αB-crystallin (αB), a closely related small heat shock protein works, pointing to molecular specificity in the observed retinal protection. The possible involvement of αA in retinal protection through immune modulation is corroborated by adaptive transfer experiments, (employing αA−/− and wild type mice with EAU as donors and Rag2−/− as the recipient mice), which indicate that αA protects against the autoimmune challenge by modulating the systemic B and T cell immunity. We show that αA administration causes marked reduction in Th1 cytokines (TNF-α, IL-12 and IFN-γ), both in the retina and in the spleen; notably, IL-17 was only reduced in the retina suggesting local intervention. Importantly, expression of Toll-like receptors and their associated adaptors is also inhibited suggesting that αA protection, against photoreceptor loss in EAU, is associated with systemic suppression of both the adaptive and innate immune responses.

TSLP: from allergy to vaccine adjuvant

The field of vaccine adjuvants has been an area of active research and development because of the need to improve the generation of protective immunity to a large number of pathogens, as well as in diseases such as cancer. Adjuvants can also help induce stronger immune responses with fewer injections, and consequently improve both the feasibility and success rate of large-scale population vaccine campaigns in developing countries. A current challenge is to identify vaccine adjuvants of various classes (cytokines, toll-like receptor ligands, etc.) with specific immune-modulating properties in order to tailor the immune response to certain pathological situations. In this issue, Van Roey et al. [Eur. J. Immunol. 2012. 42: 353-363] explore one of these challenges, namely to identify novel mucosal adjuvants. Van Roey et al. show that the pro-allergic cytokine thymic stromal lymphopoietin (TSLP) promotes a strong B-cell response with production of secretory IgA at mucosal sites. Here, we discuss the importance and limits of these findings within the broader field of vaccine adjuvants, and the potential development of TSLP as a mucosal and B-cell adjuvant in humans.

Intranasal administration of an inactivated Yersinia pestis vaccine with interleukin-12 generates protective immunity against pneumonic plague

Inhalation of Yersinia pestis causes pneumonic plague, which rapidly progresses to death. A previously licensed killed whole-cell vaccine is presently unavailable due to its reactogenicity and inconclusive evidence of efficacy. The present study now shows that vaccination intranasally (i.n.) with inactivated Y. pestis CO92 (iYp) adjuvanted with interleukin-12 (IL-12) followed by an i.n. challenge with a lethal dose of Y. pestis CO92 prevented bacterial colonization and protected 100% of mice from pneumonic plague. Survival of the vaccinated mice correlated with levels of systemic and lung antibodies, reduced pulmonary pathology and proinflammatory cytokines, and the presence of lung lymphoid cell aggregates. Protection against pneumonic plague was partially dependent upon Fc receptors and could be transferred to naïve mice with immune mouse serum. On the other hand, protection was not dependent upon complement, and following vaccination, depletion of CD4 and/or CD8 T cells before challenge did not affect survival. In summary, the results demonstrate the safety, immunogenicity, and protective efficacy of i.n. administered iYp plus IL-12 in a mouse model of pneumonic plague.