Harnessing anti-cytomegalovirus immunity for local immunotherapy against solid tumors.

Tumor infiltration by T cells profoundly affects cancer progression and responses to immunotherapy. However, the tumor immunosuppressive microenvironment can impair the induction, trafficking, and local activity of antitumor T cells. Here, we investigated whether intratumoral injection of virus-derived peptide epitopes could activate preexisting antiviral T cell responses locally and promote antitumor responses or antigen spreading. We focused on a mouse model of cytomegalovirus (CMV), a highly prevalent human infection that induces vigorous and durable T cell responses. Mice persistently infected with murine CMV (MCMV) were challenged with lung (TC-1), colon (MC-38), or melanoma (B16-F10) tumor cells. Intratumoral injection of MCMV-derived T cell epitopes triggered in situ and systemic expansion of their cognate, MCMV-specific CD4+ or CD8+ T cells. The MCMV CD8+ T cell epitopes injected alone provoked arrest of tumor growth and some durable remissions. Intratumoral injection of MCMV CD4+ T cell epitopes with polyinosinic acid:polycytidylic acid (pI:C) preferentially elicited tumor antigen-specific CD8+ T cells, promoted tumor clearance, and conferred long-term protection against tumor rechallenge. Notably, secondary proliferation of MCMV-specific CD8+ T cells correlated with better tumor control. Importantly, intratumoral injection of MCMV-derived CD8+ T cell-peptide epitopes alone or CD4+ T cell-peptide epitopes with pI:C induced potent adaptive and innate immune activation of the tumor microenvironment. Thus, CMV-derived peptide epitopes, delivered intratumorally, act as cytotoxic and immunotherapeutic agents to promote immediate tumor control and long-term antitumor immunity that could be used as a stand-alone therapy. The tumor antigen-agnostic nature of this approach makes it applicable across a broad range of solid tumors regardless of their origin.

In silico design of a T-cell epitope vaccine candidate for parasitic helminth infection.

Trichuris trichiura is a parasite that infects 500 million people worldwide, leading to colitis, growth retardation and Trichuris dysentery syndrome. There are no licensed vaccines available to prevent Trichuris infection and current treatments are of limited efficacy. Trichuris infections are linked to poverty, reducing children's educational performance and the economic productivity of adults. We employed a systematic, multi-stage process to identify a candidate vaccine against trichuriasis based on the incorporation of selected T-cell epitopes into virus-like particles. We conducted a systematic review to identify the most appropriate in silico prediction tools to predict histocompatibility complex class II (MHC-II) molecule T-cell epitopes. These tools were used to identify candidate MHC-II epitopes from predicted ORFs in the Trichuris genome, selected using inclusion and exclusion criteria. Selected epitopes were incorporated into Hepatitis B core antigen virus-like particles (VLPs). Bone marrow-derived dendritic cells and bone marrow-derived macrophages responded in vitro to VLPs irrespective of whether the VLP also included T-cell epitopes. The VLPs were internalized and co-localized in the antigen presenting cell lysosomes. Upon challenge infection, mice vaccinated with the VLPs+T-cell epitopes showed a significantly reduced worm burden, and mounted Trichuris-specific IgM and IgG2c antibody responses. The protection of mice by VLPs+T-cell epitopes was characterised by the production of mesenteric lymph node (MLN)-derived Th2 cytokines and goblet cell hyperplasia. Collectively our data establishes that a combination of in silico genome-based CD4+ T-cell epitope prediction, combined with VLP delivery, offers a promising pipeline for the development of an effective, safe and affordable helminth vaccine.

Mucosal CD8+ T cell responses induced by an MCMV based vaccine vector confer protection against influenza challenge.

Cytomegalovirus (CMV) is a ubiquitous ß-herpesvirus that establishes life-long latent infection in a high percentage of the population worldwide. CMV induces the strongest and most durable CD8+ T cell response known in human clinical medicine. Due to its unique properties, the virus represents a promising candidate vaccine vector for the induction of persistent cellular immunity. To take advantage of this, we constructed a recombinant murine CMV (MCMV) expressing an MHC-I restricted epitope from influenza A virus (IAV) H1N1 within the immediate early 2 (ie2) gene. Only mice that were immunized intranasally (i.n.) were capable of controlling IAV infection, despite the greater potency of the intraperitoneally (i.p.) vaccination in inducing a systemic IAV-specific CD8+ T cell response. The protective capacity of the i.n. immunization was associated with its ability to induce IAV-specific tissue-resident memory CD8+ T (CD8TRM) cells in the lungs. Our data demonstrate that the protective effect exerted by the i.n. immunization was critically mediated by antigen-specific CD8+ T cells. CD8TRM cells promoted the induction of IFNγ and chemokines that facilitate the recruitment of antigen-specific CD8+ T cells to the lungs. Overall, our results showed that locally applied MCMV vectors could induce mucosal immunity at sites of entry, providing superior immune protection against respiratory infections.

Delivery of foreign cytotoxic T lymphocyte epitopes to tumor tissues for effective antitumor immunotherapy against pre-established solid tumors in mice.

Cytotoxic T lymphocyte (CTL) can have remarkable abilities to kill tumor cells. However, the establishment of successful CTL-based anticancer therapy has met with many challenges. Within tumor cells, there exist subpopulations with low or no expression of the targeted antigen (termed as antigen-loss variants). In addition, tumor cells can downregulate the levels of major histocompatibility complex class I (MHC-I) molecules on cell surface due to immune pressure. As a result, some tumor cells can escape the immune pressure bestowed by CTLs, resulting in treatment failure. To address these difficulties, a new approach is developed to deliver foreign high-affinity CTL epitopes to tumor tissues utilizing pH-responsive "smart" microparticles (MPs). These MPs could encapsulate CTL peptide epitope, release the peptide under acidic condition encountered in tumor tissues and enhance CTL activation. Mice bearing pre-established tumor as "antigen-loss variant" solid tumor models were administered intratumorally with MPs containing the CTL peptide, which showed 100% survival following the treatment. In contrast, all control mice died from tumor. Significant protection from tumor-induced death was also observed with systemic administration of CTL peptide-MPs. The therapeutic efficacy can be attributed to enhanced delivery of the epitope to tumor tissues, presentation of the epitope by tumor cells as well as tumor stromal cells and/or generation of epitope-specific CTLs by the peptide-containing MPs. These findings offer a promising new direction for treating established solid tumor using CTL therapy.

Phase I/II study exploring ImMucin, a pan-major histocompatibility complex, anti-MUC1 signal peptide vaccine, in multiple myeloma patients.

ImMucin, a 21-mer cancer vaccine encoding the signal peptide domain of the MUC1 tumour-associated antigen, possesses a high density of T- and B-cell epitopes but preserves MUC1 specificity. This phase I/II study assessed the safety, immunity and clinical response to 6 or 12 bi-weekly intradermal ImMucin vaccines, co-administered with human granulocyte-macrophage colony-stimulating factor to 15 MUC1-positive multiple myeloma (MM) patients, with residual or biochemically progressive disease following autologous stem cell transplantation. Vaccination was well tolerated; all adverse events were temporal grade 1 2 and spontaneously resolved. ImMucin vaccination induced a robust increase in γ-interferon (IFN-γ-producing CD4+ and CD8+ T-cells (≤80-fold), a pronounced population of ImMucin multimer CD8+ T-cells (>2%), a 9·4-fold increase in peripheral blood mononuclear cells proliferation and 6·8-fold increase in anti-ImMucin antibodies, accompanied with T-cell and antibody-dependent cell-mediated cytotoxicity. A significant decrease in soluble MUC1 levels was observed in 9/10 patients. Stable disease or improvement, persisting for 17·5-41·3 months (ongoing) was achieved in 11/15 patients and appeared to be associated with low-intermediate PDL1 (CD274) bone marrow levels pre- and post-vaccination. In summary, ImMucin, a highly tolerable cancerous vaccine, induces robust, diversified T- and B-cell ImMucin-specific immunity in MM patients, across major histocompatibility complex-barrier, resulting in at least disease stabilization in most patients.

STING activator c-di-GMP enhances the anti-tumor effects of peptide vaccines in melanoma-bearing mice.

Therapeutic vaccines to induce anti-tumor CD8 T cells have been used in clinical trials for advanced melanoma patients, but the clinical response rate and overall survival time have not improved much. We believe that these dismal outcomes are caused by inadequate number of antigen-specific CD8 T cells generated by most vaccines. In contrast, huge CD8 T cell responses readily occur during acute viral infections. High levels of type-I interferon (IFN-I) are produced during these infections, and this cytokine not only exhibits anti-viral activity but also promotes CD8 T cell responses. The studies described here were performed to determine whether promoting the production of IFN-I could enhance the potency of a peptide vaccine. We report that cyclic diguanylate monophosphate (c-di-GMP), which activates the stimulator of interferon genes, potentiated the immunogenicity and anti-tumor effects of a peptide vaccine against mouse B16 melanoma. The synergistic effects of c-di-GMP required co-administration of costimulatory anti-CD40 antibody, the adjuvant poly-IC, and were mediated in part by IFN-I. These findings demonstrate that peptides representing CD8 T cell epitopes can be effective inducers of large CD8 T cell responses in vaccination strategies that mimic acute viral infections.

Ingestion of oats and barley in patients with celiac disease mobilizes cross-reactive T cells activated by avenin peptides and immuno-dominant hordein peptides.

Celiac disease (CD) is a common CD4(+) T cell mediated enteropathy driven by gluten in wheat, rye, and barley. Whilst clinical feeding studies generally support the safety of oats ingestion in CD, the avenin protein from oats can stimulate intestinal gluten-reactive T cells isolated from some CD patients in vitro. Our objective was to establish whether ingestion of oats or other grains toxic in CD stimulate an avenin-specific T cell response in vivo. We fed participants a meal of oats (100 g/day over 3 days) to measure the in vivo polyclonal avenin-specific T cell responses to peptides contained within comprehensive avenin peptide libraries in 73 HLA-DQ2.5(+) CD patients. Grain cross-reactivity was investigated using oral challenge with wheat, barley, and rye. Avenin-specific responses were observed in 6/73 HLA-DQ2.5(+) CD patients (8%), against four closely related peptides. Oral barley challenge efficiently induced cross-reactive avenin/hordein-specific T cells in most CD patients, whereas wheat or rye challenge did not. In vitro, immunogenic avenin peptides were susceptible to digestive endopeptidases and showed weak HLA-DQ2.5 binding stability. Our findings indicate that CD patients possess T cells capable of responding to immuno-dominant hordein epitopes and homologous avenin peptides ex vivo, but the frequency and consistency of these T cells in blood is substantially higher after oral challenge with barley compared to oats. The low rates of T cell activation after a substantial oats challenge (100 g/d) suggests that doses of oats commonly consumed are insufficient to cause clinical relapse, and supports the safety of oats demonstrated in long-term feeding studies.

Anti-IFN-γ and peptide-tolerization therapies inhibit acute lung injury induced by cross-reactive influenza A-specific memory T cells.

Viral infections have variable outcomes, with severe disease occurring in only few individuals. We hypothesized that this variable outcome could correlate with the nature of responses made to previous microbes. To test this, mice were infected initially with influenza A virus (IAV) and in memory phase challenged with lymphocytic choriomeningitis virus (LCMV), which we show in this study to have relatively minor cross-reactivity with IAV. The outcome in genetically identical mice varied from mild pneumonitis to severe acute lung injury with extensive pneumonia and bronchiolization, similar to that observed in patients who died of the 1918 H1N1 pandemic. Lesion expression did not correlate with virus titers. Instead, disease severity directly correlated with and was predicted by the frequency of IAV-PB1703- and IAV-PA224-specific responses, which cross-reacted with LCMV-GP34 and LCMV-GP276, respectively. Eradication or functional ablation of these pathogenic memory T cell populations, using mutant-viral strains, peptide-based tolerization strategies, or short-term anti-IFN-γ treatment, inhibited severe lesions such as bronchiolization from occurring. Heterologous immunity can shape outcome of infections and likely individual responses to vaccination, and can be manipulated to treat or prevent severe pathology.

A new model for CD8+ T cell memory inflation based upon a recombinant adenoviral vector.

CD8(+) T cell memory inflation, first described in murine CMV (MCMV) infection, is characterized by the accumulation of high-frequency, functional Ag-specific CD8(+) T cell pools with an effector-memory phenotype and enrichment in peripheral organs. Although persistence of Ag is considered essential, the rules underpinning memory inflation are still unclear. The MCMV model is, however, complicated by the virus's low-level persistence and stochastic reactivation. We developed a new model of memory inflation based on a ß-galactosidase (ßgal)-recombinant adenovirus vector. After i.v. administration in C57BL/6 mice, we observed marked memory inflation in the ßgal96 epitope, whereas a second epitope, ßgal497, undergoes classical memory formation. The inflationary T cell responses show kinetics, distribution, phenotype, and functions similar to those seen in MCMV and are reproduced using alternative routes of administration. Memory inflation in this model is dependent on MHC class II. As in MCMV, only the inflating epitope showed immunoproteasome independence. These data define a new model for memory inflation, which is fully replication independent, internally controlled, and reproduces the key immunologic features of the CD8(+) T cell response. This model provides insight into the mechanisms responsible for memory inflation and, because it is based on a vaccine vector, also is relevant to novel T cell-inducing vaccines in humans.

Comparative analysis of the magnitude, quality, phenotype, and protective capacity of simian immunodeficiency virus gag-specific CD8+ T cells following human-, simian-, and chimpanzee-derived recombinant adenoviral vector immunization.

Recombinant adenoviral vectors (rAds) are the most potent recombinant vaccines for eliciting CD8(+) T cell-mediated immunity in humans; however, prior exposure from natural adenoviral infection can decrease such responses. In this study we show low seroreactivity in humans against simian- (sAd11, sAd16) or chimpanzee-derived (chAd3, chAd63) compared with human-derived (rAd5, rAd28, rAd35) vectors across multiple geographic regions. We then compared the magnitude, quality, phenotype, and protective capacity of CD8(+) T cell responses in mice vaccinated with rAds encoding SIV Gag. Using a dose range (1 × 10(7)-10(9) particle units), we defined a hierarchy among rAd vectors based on the magnitude and protective capacity of CD8(+) T cell responses, from most to least, as: rAd5 and chAd3, rAd28 and sAd11, chAd63, sAd16, and rAd35. Selection of rAd vector or dose could modulate the proportion and/or frequency of IFN-γ(+)TNF-α(+)IL-2(+) and KLRG1(+)CD127(-)CD8(+) T cells, but strikingly ∼30-80% of memory CD8(+) T cells coexpressed CD127 and KLRG1. To further optimize CD8(+) T cell responses, we assessed rAds as part of prime-boost regimens. Mice primed with rAds and boosted with NYVAC generated Gag-specific responses that approached ∼60% of total CD8(+) T cells at peak. Alternatively, priming with DNA or rAd28 and boosting with rAd5 or chAd3 induced robust and equivalent CD8(+) T cell responses compared with prime or boost alone. Collectively, these data provide the immunologic basis for using specific rAd vectors alone or as part of prime-boost regimens to induce CD8(+) T cells for rapid effector function or robust long-term memory, respectively.

Effective cooperation of monoclonal antibody and peptide vaccine for the treatment of mouse melanoma.

mAbs binding to tumor-associated surface Ags are therapeutically applied in a range of malignancies. Therapeutic vaccination only recently met with clinical success, and the first cancer vaccine received U.S. Food and Drug Administration approval last year. To improve current protocols, we combined peptide vaccines with mAb to the tyrosinase-related protein (TRP)-1 surface Ag for the treatment of B16F10 skin melanoma. Vaccine formulations with synthetic long peptides failed to elicit strong CD8 T cell responses to self-differentiation Ags gp100 and TRP-2, whereas altered peptide sequences recruited gp100-specific CD8 T cells from the endogenous repertoire with frequencies of 40%. However, these high frequencies were reached too late; large, progressively growing melanomas had already emerged. Addition of the TRP-1-directed mAb TA99 to the treatment protocol mediated eradication of s.c. lesions. The mode of action of the Ab did not depend on complement factor C3 and did not lead to improved Ag presentation and CD8 T cell immunity; rather, it recruited FcγR-bearing innate immune cells during early tumor control, thereby creating a window of time for the generation of protective cellular immunity. These data support the concept of combination therapy, in which passive transfer of mAbs is supplemented with cancer peptide vaccines. Moreover, we advocate that tumor Ag-specific T cell immunity directed against self-proteins can be exploited from the endogenous repertoire.

Transcutaneous Peptide Immunotherapy of Japanese Cedar Pollinosis Using Solid-in-Oil Nanodispersion Technology.

Peptide immunotherapy is an attractive approach to relieve allergic symptoms such as rhinitis and asthma. Treatment of Japanese cedar pollinosis (Cryptomeria japonica; Cj), from which over one quarter of Japanese population suffer, is becoming a great concern. Recently, oral feeding of a peptide (7crp) consisting of seven immunodominant human T cell epitopes derived from two enzymes present in Cj pollen was demonstrated to have a benefit in treating Cj pollinosis. In this work, we aimed to apply a novel transcutaneous administration system as a simple and easy peptide delivery for an immunotherapy using a T cell epitope peptide. A modified 7crp peptide (7crpR) which contained triarginine linkers between each epitopes was designed to increase water solubility and was encapsulated in a unique solid-in-oil (S/O) nanodispersion. The S/O nanodispersion consists of a nano-sized peptide-surfactant complex dispersed in an oil vehicle. The S/O nanopartilces having an average diameter of 230 nm facilitated the permeation of the peptide 7crpR into the skin and suppressed serum total IgE and antigen-specific IgE levels in a Cj pollinosis mouse model. Transcutaneous administration of the T cell epitope peptide using the S/O nanodispersion system has potential for future simple and easy immunotherapy of Cj pollinosis.

Maintenance of T cell function in the face of chronic antigen stimulation and repeated reactivation for a latent virus infection.

Persisting infections are often associated with chronic T cell activation. For certain pathogens, this can lead to T cell exhaustion and survival of what is otherwise a cleared infection. In contrast, for herpesviruses, T cells never eliminate infection once it is established. Instead, effective immunity appears to maintain these pathogens in a state of latency. We used infection with HSV to examine whether effector-type T cells undergoing chronic stimulation retained functional and proliferative capacity during latency and subsequent reactivation. We found that latency-associated T cells exhibited a polyfunctional phenotype and could secrete a range of effector cytokines. These T cells were also capable of mounting a recall proliferative response on HSV reactivation and could do so repeatedly. Thus, for this latent infection, T cells subjected to chronic Ag stimulation and periodic reactivation retain the ability to respond to local virus challenge.

Synchronization of dendritic cell activation and antigen exposure is required for the induction of Th1/Th17 responses.

The dendritic cell (DC) targeting/activation patterns required to elicit Th1/Th17 responses remain undefined. One postulated requirement was that of a physical linkage between Ags and immunomodulators. Accordingly, the separate same-site administration of Ag85B-ESAT-6 (hybrid-1 protein; H1), a mycobacterial fusion Ag, and the CAF01 liposome-based adjuvant induced similar Ab and weak Th2 responses as those of coformulated H1/CAF01 but failed to elicit Th1/Th17 responses. Yet, this separate same-site injection generated the same type and number of activated Ag(+)/adjuvant(+) DCs in the draining lymph nodes (LN) as that of protective H1/CAF01 immunization. Thus, targeting/activating the same DC population by Ag and adjuvant is not sufficient to elicit Th1/Th17 responses. To identify the determinants of Th1/Th17 adjuvanticity, in vivo tracking experiments using fluorescently labeled Ag and adjuvant identified that a separate same-site administration elicits an additional early Ag(+)/adjuvant(-) DC population with a nonactivated phenotype, resulting from the earlier targeting of LN DCs by H1 than by CAF01 molecules. This asynchronous targeting pattern was mimicked by the injection of free H1 prior to or with, but not after, H1/CAF01 or H1/CpG/ aluminum hydroxide immunization. The injection of soluble OVA similarly prevented the induction of Th1 responses by OVA/CAF01. Using adoptively transferred OT-2 cells, we show that the Ag targeting of LN DCs prior to their activation generates nonactivated Ag-pulsed DCs that recruit Ag-specific T cells, trigger their initial proliferation, but interfere with Th1 induction in a dose-dependent manner. Thus, the synchronization of DC targeting and activation is a critical determinant for Th1/Th17 adjuvanticity.

Multieffector-functional immune responses of HMBPP-specific Vγ2Vδ2 T cells in nonhuman primates inoculated with Listeria monocytogenes ΔactA prfA*.

Although Listeria monocytogenes can induce systemic infection causing spontaneous abortion, septicemia, and meningitis, studies have not been performed to investigate human anti-L. monocytogenes immune responses, including those of Ag-specific Vγ2Vδ2 T cells, a dominant human γδ T cell subset. L. monocytogenes is the only pathogen known to possess both the mevalonate and non-mevalonate isoprenoid biosynthesis pathways that produce metabolic phosphates or phosphoantigens activating human Vγ2Vδ2 T cells, making it interesting to explore in vivo anti-L. monocytogenes immune responses of Vγ2Vδ2 T cells. In this study, we demonstrated that subclinical systemic L. monocytogenes infection of rhesus macaques via parenteral inoculation or vaccination with an attenuated Listeria strain induced multieffector-functional immune responses of phosphoantigen-specific Vγ2Vδ2 T cells. Subclinical systemic infection and reinfection with attenuated L. monocytogenes uncovered the ability of Vγ2Vδ2 T cells to mount expansion and adaptive or recall-like expansion. Expanded Vγ2Vδ2 T cells could traffic to and accumulate in the pulmonary compartment and intestinal mucosa. Expanded Vγ2Vδ2 T cells could evolve into effector cells producing IFN-γ, TNF-α, IL-4, IL-17, or perforin after L. monocytogenes infection, and some effector Vγ2Vδ2 T cells could coproduce IL-17 and IFN-γ, IL-4 and IFN-γ, or TNF-α and perforin. Surprisingly, in vivo-expanded Vγ2Vδ2 T effector cells in subclinical L. monocytogenes infection could directly lyse L. monocytogenes-infected target cells and inhibit intracellular L. monocytogenes bacteria. Thus, we present the first demonstration, to our knowledge, of multieffector-functional Vγ2Vδ2 T cell responses against L. monocytogenes.

Regulatory dendritic cells pulsed with carbonic anhydrase I protect mice from colitis induced by CD4+CD25- T cells.

Inflammatory bowel disease (IBD), which is characterized by a dysregulated intestinal immune response, is postulated to be controlled by intestinal self-antigens and bacterial Ags. Fecal extracts called cecal bacterial Ag (CBA) have been implicated in the pathogenesis of IBD. In this study, we identified a major protein of CBA related to the pathogenesis of IBD and established a therapeutic approach using Ag-pulsed regulatory dendritic cells (Reg-DCs). Using two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry, carbonic anhydrase I (CA I) was identified as a major protein of CBA. Next, we induced colitis by transfer of CD4(+)CD25(-) T cells obtained from BALB/c mice into SCID mice. Mice were treated with CBA- or CA I-pulsed Reg-DCs (Reg-DCs(CBA) or Reg-DCs(CA1)), which expressed CD200 receptor 3 and produced high levels of IL-10. Treatment with Reg-DCs(CBA) and Reg-DCs(CA1) ameliorated colitis. This effect was shown to be Ag-specific based on no clinical response of irrelevant Ag (keyhole limpet hemocyanin)-pulsed Reg-DCs. Foxp3 mRNA expression was higher but RORγt mRNA expression was lower in the mesenteric lymph nodes (MLNs) of the Reg-DCs(CA1)-treated mice compared with those in the MLNs of control mice. In the MLNs, Reg-DCs(CA1)-treated mice had higher mRNA expression of IL-10 and TGF-ß1 and lower IL-17 mRNA expression and protein production compared with those of control mice. In addition, Reg-DCs(CBA)-treated mice had higher Foxp3(+)CD4(+)CD25(+) and IL-10-producing regulatory T cell frequencies in MLNs. In conclusion, Reg-DCs(CA1) protected progression of colitis induced by CD4(+)CD25(-) T cell transfer in an Ag-specific manner by inducing the differentiation of regulatory T cells.

Rapid in vivo conversion of effector T cells into Th2 cells during helminth infection.

Stimulation of the immune system by pathogens, allergens, or autoantigens leads to differentiation of CD4(+) T cells with pro- or anti-inflammatory effector cell functions. Based on functional properties and expression of characteristic cytokines and transcription factors, effector CD4(+) T cells have been grouped mainly into Th1, Th2, Th17, and regulatory T (Treg) cells. At least some of these T cell subsets remain responsive to external cues and acquire properties of other subsets, raising the hope that this functional plasticity might be exploited for therapeutic purposes. In this study, we used an Ag-specific adoptive transfer model and determined whether in vitro-polarized or ex vivo-isolated Th1, Th17, or Treg cells can be converted into IL-4-expressing Th2 cells in vivo by infection of mice with the gastrointestinal helminth Nippostrongylus brasiliensis. Th1 and Th17 cells could be repolarized to acquire the expression of IL-4 and lose the expression of their characteristic cytokines IFN-γ and IL-17A, respectively. In contrast, both in vitro-generated and ex vivo-isolated Treg cells were largely resistant to repolarization. The helminth-induced conversion of Th1 or Th17 cells into Th2 cells may partially explain the inverse correlation between helminth infection and protection against autoimmune disorders.

Adjuvanted HLA-supertype restricted subdominant peptides induce new T-cell immunity during untreated HIV-1-infection.

We investigated the potential of inducing additional T-cell immunity during chronic HIV-1 infection directed to subdominant HIV-1 epitopes from common HLA-supertypes. Ten treatment-naïve HIV-1-infected individuals were immunized with peptides in the adjuvant CAF01. One individual received placebo. T-cell immunogenicity was examined longitudinally by a flow cytometry (CD107a, IFNγ, TNFα, IL-2 and/or MIP1ß expression) as well as IFNγ ELISPOT. Safety was evaluated by clinical follow up combined with monitoring of biochemistry, hematology, CD4 T-cell counts and viral load. New CD4 and CD8 T-cell responses specific for one or more vaccine epitopes were induced in 10/10 vaccinees. The responses were dominated by CD107a and MIP1ß expression. There were no significant changes in HIV-1 viral load or CD4 T-cell counts. Our study demonstrates that the peptide/CAF01 vaccine is safe and that it is possible to generate new HIV-1 T-cell responses to defined epitopes in treatment-naïve HIV-1-infected individuals.

Concurrent allorecognition has a limited impact on posttransplant vaccination.

Transplantation of allogeneic hematopoietic stem cells with or without immunocompetent lymphocytes has proved a successful strategy in the treatment of hematological malignancies. We have recently shown that this approach can also cure mouse prostate cancer, provided that it is combined with tumor-specific vaccination. Whether the response to alloantigens acts by providing helper function to enhance vaccine-specific responses or in other ways impinges on vaccine immunogenicity remains to be clarified, and this question is of clinical relevance. In this study, we have addressed this issue by comparing the immunogenicity of dendritic cells pulsed with a peptide derived from a tumor/viral model Ag in recipients of donor cells either syngeneic to the host or differing for either Y-encoded or multiple minor H antigens. We report that vaccination elicits comparable proliferation and differentiation of peptide-specific CD8(+) T cells despite concurrent expansion and differentiation of minor H antigen-specific IFN-γ effector T cells. Depletion of alloreactive CD4(+) T cells reduced alloreactivity but not vaccine-induced CD8(+) T cell priming, suggesting that alloresponses do not provide helper functions in peripheral lymphoid tissues. Vaccine-mediated T cell priming was also preserved in the case of multiple minor H antigen disparities, prone to graft-versus-host disease. Thus, in the context of nonmyeloablative allotransplantation aimed at restoring an effective tumor-specific T cell repertoire, minor H antigen-specific T cells do not interfere with vaccine-induced T cell priming, supporting the notion that posttransplant vaccination is a valuable strategy to boost tumor and pathogen-specific protective immunity.

Yersinia pestis YopE contains a dominant CD8 T cell epitope that confers protection in a mouse model of pneumonic plague.

Septic bacterial pneumonias are a major cause of death worldwide. Several of the highest priority bioterror concerns, including anthrax, tularemia, and plague, are caused by bacteria that acutely infect the lung. Bacterial resistance to multiple antibiotics is increasingly common. Although vaccines may be our best defense against antibiotic-resistant bacteria, there has been little progress in the development of safe and effective vaccines for pulmonary bacterial pathogens. The Gram-negative bacterium Yersinia pestis causes pneumonic plague, an acutely lethal septic pneumonia. Historic pandemics of plague caused millions of deaths, and the plague bacilli's potential for weaponization sustains an ongoing quest for effective countermeasures. Subunit vaccines have failed, to date, to fully protect nonhuman primates. In mice, they induce the production of Abs that act in concert with type 1 cytokines to deliver high-level protection; however, the Y. pestis Ags recognized by cytokine-producing T cells have yet to be defined. In this study, we report that Y. pestis YopE is a dominant Ag recognized by CD8 T cells in C57BL/6 mice. After vaccinating with live attenuated Y. pestis and challenging intranasally with virulent plague, nearly 20% of pulmonary CD8 T cells recognize this single, highly conserved Ag. Moreover, immunizing mice with a single peptide, YopE(69-77), suffices to confer significant protection from lethal pulmonary challenge. These findings suggest YopE could be a valuable addition to subunit plague vaccines and provide a new animal model in which sensitive, pathogen-specific assays can be used to study CD8 T cell-mediated defense against acutely lethal bacterial infections of the lung.