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Background Zika virus (ZIKV) is an emerging public health threat, rendering development of a safe and effective vaccine against the virus a high priority to face this unmet medical need. Our vaccine candidate has been developed on the same platform used for the licensed vaccine IXIARO®, a vaccine against Japanese Encephalitis virus, another closely related member of the Flaviviridae family. Methods Between 24 February 2018 and 16 November 2018, we conducted a randomized, observer-blinded, placebo controlled, single center phase 1 study to assess the safety and immunogenicity of an adjuvanted, inactivated, purified whole-virus Zika vaccine candidate in the USA. A total of 67 healthy flavivirus-naïve adults aged 18–49 years were randomly assigned to one of five study arms to receive two immunizations of either high dose or low dose (6 antigen units or 3 antigen units) with both dose levels applied in two different immunization regimens or placebo as control. Results Our vaccine candidate showed an excellent safety profile independent of dose and vaccination regimen with predominantly mild adverse events (AEs). No serious AE has been reported. The ZIKV vaccine induced neutralizing antibodies in all tested doses and regimens with seroconversion rates up to 85.7% (high dose), which remained up to 40% (high dose) at 6 months follow-up. Of note, the rapid regimen triggered a substantial immune response within days. Conclusions The rapid development and production of a ZIKV vaccine candidate building on a commercial Vero-cell manufacturing platform resulted in a safe and immunogenic vaccine suitable for further clinical development. To optimize antibody persistence, higher doses and a booster administration might be considered.

Summary Background Chikungunya disease, which results in incapacitating arthralgia, has been reported worldwide. We developed a live-attenuated chikungunya virus (CHIKV) vaccine candidate designed for active immunisation of the general population living in endemic regions, as well as serving as a prophylactic measure for travellers to endemic areas. Methods This single-blind, randomised, dose-escalation, phase 1 study investigated as primary outcome safety of a live-attenuated CHIKV vaccine candidate. At two professional clinical trial centres in Illinois and Alabama, USA, healthy volunteers aged 18–45 years were randomly assigned (1:1:2) to one of three escalating dose groups (low dose 3·2 × 103 per 0·1 mL; medium dose 3·2 × 104 per 1 mL; or high dose 3·2 × 105 50% tissue culture infection dose per 1 mL) and received a single-shot immunisation on day 0. Individuals in all groups were revaccinated with the highest dose on either month 6 or 12, and followed up for 28 days after revaccination. The safety analysis included all individuals who received the single vaccination; the immunogenicity analysis, which was a secondary outcome, included all individuals who completed the study without major protocol deviations (per-protocol population). The study is registered with ClinicalTrials.gov , NCT03382964 , and is complete. Findings The study was done between March 5, 2018, and Jul 23, 2019, with 120 adults recruited and enrolled between March 5 and June 21, 2018, and assigned to receive a low (n=31), medium (n=30), or high (n=59) dose of the vaccine. The vaccine was safe in the high-dose group and well tolerated in the low-dose and medium-dose groups. Four (7%) of 59 vaccinees in the high-dose group reported any local reaction, and 11 (36%), 12 (40%), and 40 (68%) volunteers in the low-dose, medium-dose, and high-dose groups, respectively, reported any solicited systemic reaction. No vaccine-related serious adverse events were reported. Data up to month 12 after a single immunisation of the 120 healthy volunteers showed a good immunogenicity profile with 100% seroconversion rates achieved at day 14 (103 [100%] of 103) and sustained for 1 year across all dose groups. Mean peak antibody titres at day 28 ranged from 592·6 to 686·9 geometric mean titres from the low-dose to high-dose groups, respectively. A single vaccination was sufficient to induce sustaining high-titre neutralising antibodies, as shown by the absence of an anamnestic response after any revaccination ranging from 94% to 100% of participants. Following revaccination, vaccinees were protected from vaccine-induced viraemia. Interpretation A novel live-attenuated CHIKV vaccine was well tolerated and highly immunogenic in an adult population and could be an effective intervention for prophylaxis of chikungunya disease worldwide. Funding Valneva, Vienna, Austria; Coalition for Epidemic Preparedness Innovation and EU Horizon 2020.

Background: Chikungunya disease has been reported worldwide resulting in incapacitating arthralgia. We developed a live-attenuated Chikungunya virus vaccine candidate designed for active immunization of the general population living in endemic regions, as well as serving as a prophylactic measure for travelers to endemic areas. Methods: An observer-blinded, randomized, dose-escalation phase 1 clinical study investigated safety, immunogenicity and antibody persistence. Healthy volunteers aged 18 to 45 years were randomly assigned 1:1:2 to one of three escalating dose groups (low 3·2×103/0·1mL, medium 3·2×104 /1mL or high dose 3·2×105 TCID50/1mL) and received a single-shot immunization on Day 0. Half of individuals in Group H were challenged with the highest dose on Month 6 and followed up for 28 days post-challenge. Findings: Data up to Month 6 after a single immunization of 120 healthy volunteers showed an excellent immunogenicity profile with 100% seroconversion rates already achieved at Day 14 in all dose groups. Mean peak antibody titers at Day 28 range from 592·6 to 686·9 GMT from Groups L to H, respectively, with maximum titers reaching 2560. A single vaccination is sufficient to induce sustaining high titer neutralizing antibodies, as demonstrated by the absence of an anamnestic response following challenge and the development of sterilizing immunity (96·2% of participants). The vaccine was generally safe and well tolerated in the low and medium dose group, with both doses demonstrating a superior reactogenicity profile compared to the high dose group. Following challenge, vaccinees were protected from vaccine induced viremia. No adverse events of special interest and no vaccine related serious adverse events were reported. Interpretation: A novel live-attenuated CHIKV vaccine was well tolerated and highly immunogenic in an adult population and could be an effective intervention for prophylaxis of Chikungunya disease worldwide supporting further development. Trial Registration: https://clinicaltrials.gov NCT03382964. Funding Statement: Valneva Austria GmbH, Vienna, Austria. Declaration of Interests: NW, RH, OZ, AF, NB, KL, MS, UL, AM, AP, SEL, KD and WB are Valneva employees and own stock and share options in Valneva. All other authors declare that they have no competing interests. Ethics Approval Statement: Ethics committee approval has been obtained prior any study related assessments occurred. The study was compliant with the current International Council on Harmonisation/Good Clinical Practice guidelines and in accordance with the principles set forth in the Declaration of Helsinki. Throughout the study an independent data safety monitoring board consisting of four external medical experts performed periodic reviews of accruing safety information. All enrolled individuals provided their written informed consent prior to any study-related procedure.

Phosphorylation of transcription factor STAT-1 on Y701 regulates subcellular localization whereas phosphorylation of the transactivating domain at S727 enhances transcriptional activity. In this study, we investigate the impact of STAT-1 and the importance of transactivating domain phosphorylation on the induction of peptide-specific CTL in presence of the TLR9-dependent immune adjuvant IC31. STAT-1 deficiency completely abolished CTL induction upon immunization, which was strongly reduced in animals carrying the mutation of the S727 phospho-acceptor site. A comparable reduction of CTL was found in mice lacking the type I IFN (IFN-I) receptor, whereas IFN-γ-deficient mice behaved like wild-type controls. This finding suggests that S727-phosphorylated STAT-1 supports IFN-I-dependent induction of CTL. In adoptive transfer experiments, IFN-I- and S727-phosphorylated STAT-1 were critical for the activation and function of dendritic cells. Mice with a T cell-specific IFN-I receptor ablation did not show impaired CTL responses. Unlike the situation observed for CTL development S727-phosphorylated STAT-1 restrained proliferation of naive CD8+ T cells both in vitro and following transfer into Rag-deficient mice. In summary, our data reveal a dual role of S727-phosphorylated STAT-1 for dendritic cell maturation as a prerequisite for the induction of CTL activity and for T cell autonomous control of activation-induced or homeostatic proliferation.

IC31 is a novel adjuvant which combines the immunostimulatory effects of an 11-mer antibacterial peptide (KLKL(5)KLK) and a synthetic oligodeoxynucleotide (ODN1a) which is a Toll-like receptor 9 agonist without containing cytosine phosphate guanine (CpG) motifs. The effects of IC31 on neonatal immune response to vaccination have not been reported. Neonatal mice were immunized once or twice with a Streptococcus pneumoniae serotype 1 polysaccharide conjugate containing Tetanus Toxoid (Pnc1-TT) carrier protein, with or without IC31 or CpG-ODN. IC31 significantly enhanced IgG1, IgG2a and IgG2b antibodies (Ab) to the serotype 1 polysaccharide. One dose of Pnc1-TT and low dose IC31 elicited high Ab levels that protected the neonatal mice completely from bacteraemia and significantly reduced lung infection following i.n. challenge with serotype 1 pneumococcal strain. One-sixth of an adult murine dose of IC31 was sufficient and optimal for induction of protective immunity in neonatal mice. Two doses of Pnc1-TT with or without adjuvants protected the neonatal mice completely, but more rapid Ab response was observed when IC31 was given with the Pnc1-TT. IC31 is a promising new adjuvant for neonatal vaccinations, rapidly enhancing protective humoral responses when combined with Pnc1-TT.

The compromised immune responses in the elderly as well as the threat of pandemic influenza necessitate the development of improved influenza vaccines. This study provides evidence that IC31 ® , a two-component synthetic adjuvant signalling through TLR-9, augments humoral and cellular immune responses to seasonal influenza vaccines. Experiments performed in young adult mice showed increased HI titres and higher levels of IgG2a antibodies that were accompanied by the induction of IFN-γ producing CD4 + T cells after single vaccination with reduced doses of vaccine antigens, even 200 days after single immunisation. Importantly, similar effects were seen in aged mice, although most pronounced upon booster immunisation. Thus, IC31 ® fulfils important criteria of novel influenza vaccine adjuvants.

Vaccine efficacy largely depends upon DC targeting and activation. The most potent TLR soluble ligands induce diffuse DC activation, which may be associated with marked pro-inflammatory responses and possibly adverse effects. This raises the concern that effective vaccine adjuvants may similarly rely on widespread DC activation. Using a promising candidate vaccine against tuberculosis (fusion protein of Ag85B and 6-kDa early secretory antigenic target (ESAT-6)) formulated in the potent IC31 adjuvant, DC targeting and activation was studied in vivo, following the fate of antigen and adjuvant in the draining lymph nodes, to define the magnitude of DC targeting/activation required in vivo to induce protective vaccine responses. Unexpectedly, protective IFN-gamma-mediated Ag85B-ESAT-6/IC31 responses were associated to the activation of a minute population (less than 0.3%) of CD11c(+) lymph node DC, without detectable systemic pro-inflammatory responses. This activated peripheral tissue-derived DC population, characterized by enhanced CD80, CD86, CD40 and IL-12p40 expression, was only identified when focusing on adjuvant- or antigen-labeled CD11c(+) DC, which were found to support T cell proliferation. Immunization with aluminum hydroxide adjuvant (Alum) resulted in a similar proportion of antigen-associated DC but without detectable enhancement of CD80, CD86, CD40 or IL-12p40 expression. Thus, potent protective IFN-gamma-producing responses may be elicited by the exquisite activation of a minute number of in vivo targeted DC.

IC31, the combination of a novel immunostimulatory oligodeoxynucleotide containing deoxy-Inosine/deoxy-Cytosine (ODN1a) and the antimicrobial peptide KLKL(5)KLK, represents a promising novel adjuvant signaling via the TLR9/MyD88-dependent pathway of the innate immune system. In mice, IC31 induces potent peptide-specific type 1 cellular immune responses, as well as mainly type 1 dominated protein-specific cellular and humoral immune responses. In addition, cytotoxic T lymphocytes were induced, able to kill efficiently target cells in vivo. Activation of murine dendritic cells by IC31 induced efficiently proliferation of naïve CD4(+) TCR transgenic T cells (DO.11.10) as well as their differentiation into IFN-gamma- and IL-4-producing T cells in vitro.

H2-M is a major histocompatibility complex (MHC) class II-like molecule that catalyzes peptide binding to MHC class II molecules. Recently, the H2-O heterodimer, encoded by H2-Oa and H2-Ob in the MHC class II region, has been shown to be physically associated with H2-M in B cells and to downregulate H2-M function. Examination of H2-O expression in freshly isolated mouse organs revealed that H2-Oa- and H2-Ob-specific transcripts are present in both lymphoid and nonlymphoid tissues. To evaluate the gene regulation and functional impact of H2-O on antigen presentation, we examined the effects on MHCII, invariant chain (Ii), H2-M, and H2-O gene expression of interleukin (IL)-4, IL-10, and interferon (IFN)-gamma in different antigen-presenting cells (APCs). In nonprofessional APCs, e.g., L929 fibroblasts, IFN-gamma-inducible expression of the MHC class II-specific transcription factor CIITA is associated with coordinate expression of MHCII, Ii, H2-M, and H2-Oa genes but without concomitant H2-Ob induction. In contrast, professional APCs, e.g., the macrophage cell line P388D1, exhibit constitutive H2-Oa and H2-Ob expression, which is not inducible by IFN-gamma in contrast to CIITA, MHCII, Ii, and H2-M expression. In B cells, CIITA, MHCII, Ii, and H2-M genes are differentially expressed relative to H2-Oa and H2-Ob genes upon stimulation with IL-4, IL-10, or IFN-gamma. A differential ratio of H2-M to H2-O may represent one mechanism by which professional and nonprofessional APCs bypass H2-O inhibitory activity.

IL-4 was found to be the essential differentiation factor for Th2 cells and simultaneously to be a potent inhibitor of Th1 development that is induced by IFN-γ and IL-12. Furthermore, it was demonstrated that TGF-β can also inhibit Th1 development. In this work, we demonstrate that polyclonal activation of Mel-14highCD4+ T cells by immobilized anti-αβTCR mAb together with a mixture of IL-4 and TGF-β can lead to the development of both Th1 and Th2 cells, depending on the concentration of these cytokines. Additional experiments revealed that Th1 induction by a combination of IL-4 and TGF-β depends on the presence of endogenous IFN-γ, and that this alternative Th1 development is further enhanced by IL-12, but is not dependent on this cytokine. Moreover, naive OVA323–339-specific Th cells that were stimulated by APCs and OVA323–339 peptide differentiated toward Th1 cells after priming in the presence of IL-4 in combination with TGF-β. Hence, this finding confirmed the results obtained by polyclonal activation of naive CD4+ Th cells and implicates that this alternative Th1 development may also occur in vivo under the influence of TGF-β and IL-4 independently of the Th1-promoting effect of IL-12.

Streptococcus pneumoniae is responsible for many vaccine-preventable deaths, annually causing around 1 million deaths in children younger than 5 years of age. A new generation of pneumococcal vaccines based on conserved proteins is being developed. We evaluated the immunogenicities and protective efficacies of four pneumococcal protein vaccine candidates, PcsB, StkP, PsaA, and PspA, in a neonatal mouse model. Mice were immunized three times and challenged intranasally with virulent pneumococci. All four proteins were immunogenic in neonatal mice, and antibody (Ab) responses were significantly enhanced by the novel adjuvant IC31, which consists of an antibacterial peptide ( KLKL 5 KLK ) and a synthetic oligodeoxynucleotide, ODN1a, that signals through Toll-like receptor 9 (TLR9). Two single proteins, StkP and PspA, combined with IC31 significantly reduced pneumococcal bacteremia but had no effects on lung infection. Three proteins, PcsB, StkP, and PsaA, were evaluated with alum or IC31. IC31 enhanced Ab responses and avidity to all three proteins, whereas alum enhanced Ab responses and avidity to StkP and PsaA only. Mice receiving the trivalent protein formulation with IC31 had significantly reduced bacteremia and lung infection compared to unvaccinated mice, but the level of protection was dependent on the dose of IC31. When PspA was added to the trivalent protein formulation, the dose of IC31 needed to obtain protective immunity could be reduced. These results demonstrate that a novel pneumococcal protein-based vaccine is immunogenic at an early age of mice and emphasize the benefits of using a combination of conserved proteins and an effective adjuvant to elicit potent protective immunity against invasive pneumococcal disease.

New TB vaccines are urgently needed because of the apparent lack of effect of the BCG vaccine on rates of adult contagious pulmonary tuberculosis and the risk of disseminated BCG disease in immunocompromised individuals. Since BCG appears to protect children, the primary target for vaccine development is a booster vaccine for adults but such vaccines ideally need to be able to efficiently prime mycobacterially naïve individuals as well as boost individuals previously vaccinated with BCG and those latently infected with TB. Protective immunity against Mycobacterium tuberculosis depends mainly on the generation of a Th1-type cellular immune response characterized by interferon-gamma (IFN-γ) production. In the present study, we monitored safety and IFN-γ responses in healthy BCG-vaccinated and prior or latently TB-infected individuals receiving a novel vaccine composed of the fusion protein Ag85B-ESAT-6 combined with the adjuvant IC31(®), administered at 0 and 2 months. Vaccination caused few local or systemic adverse effects besides transient soreness at the injection site, but it elicited strong antigen-specific T cell responses against Ag85B-ESAT-6 and both the Ag85B and ESAT-6 components, that could be augmented by second vaccination. The strong responses persisted through 32 weeks of follow-up, indicating the induction of a persistent memory response in the vaccine recipients.

Tuberculosis (TB) remains a major killer worldwide. The only available TB vaccine, the nearly century-old Mycobacterium bovis BCG, has had only a limited effect on TB incidence. Therefore, developing new TB vaccines is a key priority, and the first new generation TB vaccines are now being tested in clinical trials. Here we describe the development and first testing in humans of a novel, wholly synthetic TB subunit vaccine. This vaccine has proven safe and highly immunogenic in all species in which it was tested, including mice, guinea pigs, non-human primates and humans. Most encouragingly, following vaccination in humans, strong IFN gamma responses persisted through at least 2 1/2 years of follow-up, indicating induction of a substantial memory response by this new TB vaccine. These findings encourage further preclinical and clinical studies with TB subunit vaccines and cellular immunity-stimulating new adjuvants.

Streptococcus pneumoniae is a major human pathogen, causing high morbidity and mortality in children, and also in the elderly, who are particularly susceptible to S. pneumoniae infections due to the dysregulated function of the aged immune system. As the current generation of polysaccharide vaccines do not provide sufficient protection for elderly, new vaccination strategies are urgently needed. To learn whether pneumococcal proteins are able to induce adaptive immune responses in adults in different age groups, we determined serum IgG antibody titers and T cell immunity (IFN-γ, IL-17A and IL-5 production) to three pneumococcal antigens, PcsB, StkP and PsaA, that are components of an investigational protein-based pneumococcal vaccine, IC47. Therefore, sera and PBMCs of 108 healthy adults in three different age groups (young, middle-aged and elderly) were analyzed by ELISA and ELISpot, respectively. We found naturally acquired antibodies to all three proteins in all age groups against all three antigens. However, elderly individuals had significantly lower IgG levels to PcsB and PsaA compared to those of younger donors. There was no significant age-related difference in the overall rate of T cell immunity for the three pneumococcal proteins. We found that the Th17 response was dominant in all age groups and was frequently combined with a Th1 or Th2 response in young and middle-aged subjects. However, in elderly persons there was a lower percentage of PBMC samples producing more than one cytokine upon antigenic stimulation. The narrow cytokine secretion pattern was the most striking difference between elderly and younger adult age groups. Our results demonstrate that in the majority of adults there is a naturally acquired humoral and cellular immune response to the three pneumococcal proteins tested. The dominance of the Th17 response is especially interesting in the light of new insights regarding the role of Th17 cells in mucosal protection against this pathogen.

Summary Interferon-regulatory factor 4 (IRF4) is essential for the development of T helper 2 (Th2) and Th17 cells. Herein, we report that IRF4 is also crucial for the development and function of an interleukin-9 (IL-9)-producing CD4 + T cell subset designated Th9. IRF4-deficient CD4 + T cells failed to develop into IL-9-producing Th9 cells, and IRF4-specific siRNA inhibited IL-9 production in wild-type CD4 + T cells. Chromatin-immunoprecipitation (ChIP) analyses revealed direct IRF4 binding to the Il9 promoter in Th9 cells. In a Th9-dependent asthma model, neutralization of IL-9 substantially ameliorated asthma symptoms. The relevance of these findings is emphasized by the fact that the induction of IL-9 production also occurs in human CD4 + T cells accompanied by the upregulation of IRF4. Our data clearly demonstrate the central function of IRF4 in the development of Th9 cells and underline the contribution of this T helper cell subset to the pathogenesis of asthma.

Though widely used, the BCG vaccine has had little apparent effect on rates of adult pulmonary tuberculosis. Moreover, the risk of disseminated BCG disease in immunocompromised individuals means that improved TB vaccines ideally need to be able to efficiently prime mycobacterially-naïve individuals as well as boost individuals previously vaccinated with BCG. Protective immunity against Mycobacterium tuberculosis is thought to depend on the generation of a Th1-type cellular immune response characterized by interferon-gamma (IFN-gamma) production. In the present study, we monitored safety and IFN-gamma responses in healthy TB-naïve humans receiving an entirely novel vaccine, composed of the fusion protein Ag85B-ESAT-6, administered at 0 and 2 months either as recombinant protein alone or combined with two concentrations of the novel adjuvant IC31. Vaccination did not cause local or systemic adverse effects besides transient soreness at the injection site, but it elicited strong antigen-specific T cell responses against H1 and both the Ag85B and the ESAT-6 components. These strong responses persisted through 2.5 years of follow-up, indicating the induction of a substantial memory response in the vaccine recipients.

Originally identified as antiviral substances produced by infected cells, type I interferons (IFN-I) are now known to have a wide range of additional activities within both the innate and adaptive immune response. Here we review properties of IFN-I contributing to their 'natural immune adjuvant' character, and their important role for the function of complete Freund's adjuvant (CFA) and the TLR9-dependent immune adjuvant IC31. We show data to demonstrate that treatment with IFN-I boosts the ability of vaccine/adjuvant combinations to induce peptide-specific CTL in both young and old mice. We view these findings in the perspective of previous clinical applications of IFN-I for vaccination.

BACKGROUND: With the exception of some live vaccines, e.g. BCG, subunit vaccines formulated with "classical" adjuvants do not induce similar responses in neonates as in adults. The usual neonatal profile is characterized by lower levels of TH1-associated biomarkers. This has hampered the development of new neonatal vaccines for diseases that require early protection. Tuberculosis is one of the major targets for neonatal immunization. In this study, we assessed the immunogenicity of a novel candidate vaccine comprising a mycobacterial fusion protein, Ag85B-ESAT-6, in a neonatal murine immunization model. METHODS/FINDINGS: The Ag85B-ESAT-6 fusion protein was formulated either with a classical alum based adjuvant or with the novel IC31 adjuvant. Following neonatal or adult immunization, 3 parameters were studied in vivo: (1) CD4(+) T cell responses, (2) vaccine targeting/activation of dendritic cells (DC) and (3) protection in a surrogate mycobacterial challenge model. Conversely to Alum, IC31 induced in both age groups strong Th1 and Th17 responses, characterized by multifunctional T cells expressing IL-2 and TNF-alpha with or without IFN-gamma. In the draining lymph nodes, a similarly small number of DC contained the adjuvant and/or the antigen following neonatal or adult immunization. Expression of CD40, CD80, CD86 and IL-12p40 production was focused on the minute adjuvant-bearing DC population. Again, DC targeting/activation was similar in adults and neonates. These DC/T cell responses resulted in an equivalent reduction of bacterial growth following infection with M. bovis BCG, whereas no protection was observed when Alum was used as adjuvant. CONCLUSION: Neonatal immunization with the IC31-adjuvanted Ag85B-ESAT-6 subunit vaccine elicited adult-like multifunctional protective anti-mycobacterial T cell responses through the induction of an adult pattern of in vivo DC activation.

Toll-like receptor (TLR) agonists have a proven potential to become the adjuvants of the next generation when admixed and formulated with all kinds of vaccine compositions. The quality and magnitude of a vaccine-induced immune response is often strongly facilitated by TLR agonists, with the result that protection is increased and expanded toward type 1-driven immunity. DNA oligodeoxynucleotides bind to TLR9 and have been tested in a variety of vaccine settings with encouraging results. Combining oligodeoxynucleotides with poly-L-arginine (IC30) or certain artificial antimicrobial peptides dramatically improves and synergizes with the adjuvant action of TLR9 agonists, a notion that has prompted the development of IC31, an adjuvant with a promising profile in both preclinical and clinical trials.

In this study, we evaluated the potential of a novel synthetic adjuvant designated IC31 for the ability to augment the immune response and protective efficacy of the well-known mycobacterial vaccine antigen, Ag85B-ESAT-6. The IC31 adjuvant, consisting of a vehicle based on the cationic peptide KLKL(5)KLK and the immunostimulatory oligodeoxynucleotide ODN1a signalling through the TLR9 receptor, was found to promote highly efficient Th1 responses. The combination of Ag85B-ESAT-6 and IC31 exhibited significant levels of protection in the mouse aerosol challenge model of tuberculosis and a detailed analysis of the immune response generated revealed the induction of CD4 T cells giving rise to high levels of IFN-gamma secretion. Furthermore, the combination of Ag85B-ESAT-6/IC31 was found to confer efficient protection in the guinea pig aerosol model of tuberculosis infection and is at present moving towards clinical testing.

Vaccines that induce high numbers of sustained T cell responses are urgently needed for the treatment of numerous diseases including cancer. Antigen-presenting cells (APCs), the most important of which are dendritic cells, orchestrate antigen-dependent T cell responses in that they present antigens to T cells in an appropriate environment. Here we present evidence that after vaccination with a simple mixture of the cationic poly-amino acid poly-L-arginine and tumor antigen-derived peptide antigens, large numbers of antigen-specific T cells are induced and APCs mediate the generation of T lymphocytes. We observe that after s.c. injection, MHC class II(+) cells infiltrate injection sites and are loaded with large amounts of antigen in vivo under the influence of poly-L-arginine. Consequently, numerous antigen-charged APCs can be detected in draining lymph nodes of vaccinated animals. Antigen-specific T cell responses induced are systemic and were readily detected more than 4 months after the last vaccination, the latest time point we measured. By contrast, even after repeat injections, we were consistently unable to detect antibody responses against poly-L-arginine, allowing this compound to be used for numerous booster injections. Clinical trials in cancer patients using poly-L-arginine as immunostimulant will be carried out in the near future.

Although vaccines have proven very successful in preventing certain infectious diseases, progress in the field has been slowed by the tediousness of developing classical vaccines consisting of whole pathogens. Thus, there is great need for improvement in several areas: firstly, the range of diseases which can be treated has to be expanded. Secondly, antigens have to be defined to make the use of whole pathogens as antigen obsolete. And thirdly, new adjuvants have to be developed which show low toxicity, high potency and are also able to drive the immune response in the desired direction. Ideally, a vaccine would only consist of well-characterized, synthetic materials. This review summarizes the different approaches for the development of completely defined synthetic vaccines.

Background: The c-kit ligand, stem cell factor (SCF), is an important activating and chemotactic factor for both mast cells and eosinophils. These cells are known to play a fundamental role in the pathogenesis of asthma. Objective: Our goal was to analyze the functional role of SCF in the pathogenesis of asthma. Methods: The expression of SCF was targeted in fibroblasts, epithelial cells, and locally in a murine model of asthma in mice induced by ovalbumin sensitization with an antisense DNA strategy. Results: We could suppress SCF expression in NIH 3T3 fibroblasts and SP1 epithelial cells by a specific antisense phosphorothioate oligonucleotide overlapping the translation start site of SCF, whereas control oligonucleotides were virtually inactive. We then focused on the role of SCF in a murine model of asthma associated with late-phase allergic inflammation in ovalbumin-sensitized mice: Local intranasal administration of FITC-labeled SCF antisense oligonucleotides led to strong DNA uptake in interstitial lung cells associated with a striking reduction of intracellular SCF expression. Such intrapulmonary blockade of SCF expression after repeated allergen challenges suppressed various signs of lung inflammation including IL-4 production and infiltration of eosinophils. SCF antisense DNA treatment was at least as effective as corticosteroid treatment. Conclusion: These data indicate a critical role for SCF in a murine asthma model and suggest that local delivery of SCF antisense oligonucleotides may be a novel approach for the treatment of inflammatory lung disorders such as asthma. (J Allergy Clin Immunol 2001;107:279-86.)

The aim of this study was to characterize and identify the mode of action of IC31®, a two-component vaccine adjuvant. We found that IC31® was accumulated in human peripheral blood monocytes, MHC class II positive cells and monocyte-derived DCs (moDCs) but not in plasmacytoid DCs (pDCs). In the presence of IC31® the differentiation of inflammatory CD1a(+) moDCs and the secretion of chemokines, TNF-α and IL-6 cytokines was inhibited but the production of IFNβ was increased. Sustained addition of IC31® to differentiating moDCs interfered with IκBα phosphorylation, while the level of phospho-IRF3 increased. We also showed that both IC31® and its KLK component exhibited a booster effect on type I IFN responses induced by the specific ligands of TLR3 or TLR7/8, whereas TLR9 ligand induces type I IFN production only in the presence of IC31® or ODN1. Furthermore, long term incubation of moDCs with IC31® caused significantly higher expression of IRF and IFN genes than a single 24 hr treatment. The adjuvant activity of IC31® on the IFN response was shown to be exerted through TLRs residing in the vesicular compartment of moDCs. Based on these results IC31® was identified as a moDC modulatory adjuvant that sets the balance of the NF-κB and IRF3 mediated signaling pathways to the production of IFNβ. Thus IC31® is emerging as a potent adjuvant to increase immune responses against intracellular pathogens and cancer in future vaccination strategies.

Qualitative differences in the MHC class II antigen processing and presentation pathway may be instrumental in shaping the CD4+ T cell response directed against tumour cells. Efficient loading of many MHC class II alleles with peptides requires the assistance of H2-M, a heterodimeric MHC class II-like molecule. In contrast to the HLA-DM region in humans, the beta-chain locus is duplicated in mouse, with the H2-Mb1 (Mb1beta-chain distal to H2-Mb2 (Mb2) and the H2-Ma (Ma) alpha-chain gene). Here, we show that murine MHC class II and H2-M genes are coordinately regulated in murine tumour cell lines by T helper cell 1 (IFN-gamma) and T helper cell 2 (IL-4 or IL-10) cytokines in the presence of the MHC class II-specific transactivator CIITA as determined by mRNA expression and Western blot analysis. Furthermore, Malphabeta1 and Malphabeta2 heterodimers are differentially expressed in murine tumour cell lines of different histology. Both H2-M isoforms promote equally processing and presentation of native protein antigens to H2-A(d)- and H2-E(d)-restricted CD4+ T cells. Murine tumour cell lines could be divided into three groups: constitutive MHC class II and CIITA expression; inducible MHC class II and CIITA expression upon IFN-gamma-treatment; and lack of constitutive and IFN-gamma-inducible MHC class II and CIITA expression. These differences may impact on CD4+ T cell recognition of cancer cells in murine tumour models.