Immunological responses and anti-tumor effects of HPV16/18 L1-L2-E7 multiepitope fusion construct along with curcumin and nanocurcumin in C57BL/6 mouse model

AIMS

Human papillomavirus (HPV) L1, L2 and E7 proteins were used as target antigens for development of preventive and therapeutic vaccines. Moreover, linkage of antigens to heat shock proteins (HSPs) could enhance the potency of vaccines. Curcumin and nanocurcumin compounds were suggested as the chemopreventive and chemotherapeutic agents against cancer. In this study, two multiepitope DNA and peptide-based vaccine constructs (L1-L2-E7 and HSP70-L1-L2-E7) were used along with curcumin and nanocurcumin to evaluate immune responses, and protective/therapeutic effects in tumor mouse model.

MAIN METHODS

At first, the multiepitope L1-L2-E7 and HSP70-L1-L2-E7 fusion genes were subcloned in eukaryotic and prokaryotic expression vectors. The recombinant multiepitope peptides were generated in E. coli strain. Then, the cytotoxic effects of curcumin and nanocurcumin were evaluated on HEK-293 T non-cancerous and C3 cancerous cells. Finally, mice vaccination was performed using different regimens. Curcumin and nanocurcumin compounds were administered alone or along with different vaccine constructs.

KEY FINDINGS

Our data indicated that the use of nanocurcumin along with the multiepitope HSP70-L1-L2-E7 vaccine construct could completely protect mice against HPV-related C3 tumor cells, and eradicate tumors in a therapeutic test. Furthermore, nanocurcumin showed higher protection than curcumin alone. Generally, curcumin and nanocurcumin compounds could reduce tumor growth synergistically with the multiepitope vaccine constructs, but they did not influence the immune responses in different regimens.

SIGNIFICANCE

These data demonstrated that the designed multiepitope vaccine constructs along with curcumin and nanocurcumin can be used as a promising method for HPV vaccine development.

Single-component multilayered self-assembling nanoparticles presenting rationally designed glycoprotein trimers as Ebola virus vaccines

Ebola virus (EBOV) glycoprotein (GP) can be recognized by neutralizing antibodies (NAbs) and is the main target for vaccine design. Here, we first investigate the contribution of the stalk and heptad repeat 1-C (HR1_C) regions to GP metastability. Specific stalk and HR1_C modifications in a mucin-deleted form (GPΔmuc) increase trimer yield, whereas alterations of HR1_C exert a more complex effect on thermostability. Crystal structures are determined to validate two rationally designed GPΔmuc trimers in their unliganded state. We then display a modified GPΔmuc trimer on reengineered protein nanoparticles that encapsulate a layer of locking domains (LD) and a cluster of helper T-cell epitopes. In mice and rabbits, GP trimers and nanoparticles elicit cross-ebolavirus NAbs, as well as non-NAbs that enhance pseudovirus infection. Repertoire sequencing reveals quantitative profiles of vaccine-induced B-cell responses. This study demonstrates a promising vaccine strategy for filoviruses, such as EBOV, based on GP stabilization and nanoparticle display.

Tissue-Resident Memory T Cells in the Lungs Protect against Acute Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in young children. The T cell response plays a critical role in facilitating clearance of an acute RSV infection, and memory T cell responses are vital for protection against secondary RSV exposures. Tissue-resident memory (TRM) T cells have been identified as a subset of memory T cells that reside in nonlymphoid tissues and are critical for providing long-term immunity. There is currently limited information regarding the establishment and longevity of TRM T cell responses elicited following an acute RSV infection as well as their role in protection against repeated RSV infections. In this study, we examined the magnitude, phenotype, and protective capacity of TRM CD4 and CD8 T cells in the lungs of BALB/c mice following an acute RSV infection. TRM CD4 and CD8 T cells were established within the lungs and waned by 149 d following RSV infection. To determine the protective capacity of TRMs, FTY720 administration was used to prevent trafficking of peripheral memory T cells into the lungs prior to challenge of RSV-immune mice, with a recombinant influenza virus expressing either an RSV-derived CD4 or CD8 T cell epitope. We observed enhanced viral clearance in RSV-immune mice, suggesting that TRM CD8 T cells can contribute to protection against a secondary RSV infection. Given the protective capacity of TRMs, future RSV vaccine candidates should focus on the generation of these cell populations within the lung to induce effective immunity against RSV infection.

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.

Nanoscale Peptide Self-assemblies Boost BCG-primed Cellular Immunity Against Mycobacterium tuberculosis

Bacillus Calmette-Guerin (BCG) is the only vaccine against TB and has limited protection efficacy, which wanes past adolescence. Multifunctional CD8+ T cells (IFN-γ+/TNF-α+/IL-2+) are associated with lower reactivation risk and enhanced control of active Mtb infection. Since boosting with BCG is contraindicated, booster vaccines that augment T cell immunity in the lungs of BCG-vaccinated individuals are urgently needed. We developed a vaccination strategy based on self-assembling peptide nanofibers presenting Mtb-specific CD8+ or CD4+ T cell epitopes that induce high frequency and antigen-specific effector memory T cells producing IFN-γ and IL-2. Intranasal immunization with peptide nanofibers was well tolerated in mice leading to increased antigen-specific CD8+ T cell population in the lungs. Co-assembled nanofibers of CD8+ T cell epitopes and toll-like receptor 2 (TLR2) agonists induced a 8-fold expansion in multifunctional CD8+ T cell populations in the lungs of vaccinated mice. Aerosol challenge with Mtb in BCG-primed and nanofiber-boosted mice provided an additional 0.5-log CFU reduction in lung bacterial load and indicating enhanced protection compared to BCG alone. Together, these data suggest that heterologous prime-boost with BCG and peptide nanofiber vaccines induces cell mediated immunity in the lung, reduces bacterial burden, and is a potentially safer alternative for boosting BCG-primed immunity.

Intranasal delivery of adjuvant-free peptide nanofibers elicits resident CD8+ T cell responses

Influenza vaccines that can be administered intranasally or by other needle-free delivery routes have potential advantages over injected formulations in terms of patient compliance, cost, and ease of global distribution. Supramolecular peptide nanofibers have been investigated previously as platforms for vaccines and immunotherapies and have been shown to raise immune responses in the absence of exogenous adjuvants and without measurable inflammation. However, at present it has not been tested whether the immunogenicity of these materials extends to the intranasal route. Here we investigated the extent to which self-assembled peptide nanofibers bearing an influenza peptide epitope elicit antigen-specific CD8+ T cell responses when delivered intranasally, and we compared these responses with those elicited by subcutaneous immunization. Peptides containing an epitope from influenza acid polymerase (PA) and the Q11 self-assembly domain formed nanofibers that were avidly taken up by dendritic cells in lung-draining mediastinal lymph nodes after intranasal immunization. Intranasally delivered nanofibers generated greater antigen-specific CD8+ T cell responses in the lung-draining lymph nodes than subcutaneous immunizations while retaining the non-inflammatory character of the materials observed in other delivery sites. The CD8+ T cells elicited systemically were functional as assessed by their ability to produce IFN-γ ex vivo, lyse epitope-pulsed target cells in vivo, and diminish viral loads in infected mice. Compared to subcutaneously delivered nanofibers, intranasally delivered peptide nanofibers significantly increased the number of persisting antigen-specific tissue resident memory CD8+ T cells in the lung, allowing for a more rapid response to infection at 6 weeks post-vaccination. These results indicate that intranasally delivered self-assembled peptide nanofibers are immunogenic when delivering CD8+ epitopes without adjuvant or CD4+ epitopes, are non-inflammatory, and promote more lung-resident memory CD8+ T cells compared to subcutaneous immunization.

An In vivo study: Adjuvant activity of poly-n-vinyl-2-pyrrolidone-co-acrylic acid on immune responses against Melanoma synthetic peptide

Peptides have been studied as an important class of components in medicine to control many major diseases with vaccination. Polymers as adjuvants are capable of enhancing the vaccine potential against various diseases by improving the delivery of antigens, and they reduce the booster doses of vaccines. In brief, polymers are promising candidates for peptide-based vaccine delivery platforms. The purpose of the present study was to create a possible alternative approach in the treatment of malignant melanoma and/or to prevent metastasis of melanoma. The study was designed as both an experimental and an in vivo study. We prepared a complex and covalent conjugate of MAGE-3 121-134 (L-L-K-Y-R-A-R-E-P-V-T-K-A-E) T-cell epitope as a vaccine candidate for melanoma. These conjugates were able to generate an immune response in mice after a single immunization, without the help of any external adjuvant. The peptide-polymer complexes activated the immune system in the best way and formed the highest antigen specific immune response. These results indicate the adjuvant activity of Poly(N-vinyl-2- pyrrolidone-co-acrylic acid) [P(VP-co-AA)] and the potential use of P(VP-coAA)-peptide based vaccine prototypes for future melanoma cancer vaccine formulations.

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.

Vaccination with Melanoma Helper Peptides Induces Antibody Responses Associated with Improved Overall Survival

PURPOSE

A melanoma vaccine incorporating six peptides designed to induce helper T-cell responses to melanoma antigens has induced Th1-dominant CD4(+) T-cell responses in most patients, and induced durable clinical responses or stable disease in 24% of evaluable patients. The present study tested whether this vaccine also induced antibody (Ab) responses to each peptide, and whether Ab responses were associated with T-cell responses and with clinical outcome.

EXPERIMENTAL DESIGN

Serum samples were studied from 35 patients with stage III-IV melanomas vaccinated with 6 melanoma helper peptides (6MHP). IgG Ab responses were measured by ELISA. Associations with immune response and overall survival were assessed by log-rank test and χ(2) analysis of Kaplan-Meier data.

RESULTS

Ab responses to 6MHP were detected by week 7 in 77% of patients, and increased to peak 6 weeks after the last vaccine and persisted to 6 months. Ab responses were induced most frequently to longer peptides. Of those with T-cell responses, 82% had early Ab responses. Survival was improved for patients with early Ab response (P = 0.0011) or with early T-cell response (P < 0.006), and was best for those with both Ab and T-cell responses (P = 0.0002).

CONCLUSIONS

Vaccination with helper peptides induced both Ab responses and T-cell responses, associated with favorable clinical outcome. Such immune responses may predict favorable clinical outcome to guide combination immunotherapy. Further studies are warranted to understand mechanisms of interaction of these Abs, T-cell responses, and tumor control.

Subcomponent vaccine based on CTA1-DD adjuvant with incorporated UreB class II peptides stimulates protective Helicobacter pylori immunity

A mucosal vaccine against Helicobacter pylori infection could help prevent gastric cancers and peptic ulcers. While previous attempts to develop such a vaccine have largely failed because of the requirement for safe and effective adjuvants or large amounts of well defined antigens, we have taken a unique approach to combining our strong mucosal CTA1-DD adjuvant with selected peptides from urease B (UreB). The protective efficacy of the selected peptides together with cholera toxin (CT) was first confirmed. However, CT is a strong adjuvant that unfortunately is precluded from clinical use because of its toxicity. To circumvent this problem we have developed a derivative of CT, the CTA1-DD adjuvant, that has been found safe in non-human primates and equally effective compared to CT when used intranasally. We genetically fused the selected peptides into the CTA1-DD plasmid and found after intranasal immunizations of Balb/c mice using purified CTA1-DD with 3 copies of an H. pylori urease T cell epitope (CTA1-UreB3T-DD) that significant protection was stimulated against a live challenge infection. Protection was, however, weaker than with the gold standard, bacterial lysate+CT, but considering that we only used a single epitope in nanomolar amounts the results convey optimism. Protection was associated with enhanced Th1 and Th17 immunity, but immunizations in IL-17A-deficient mice revealed that IL-17 may not be essential for protection. Taken together, we have provided evidence for the rational design of an effective mucosal subcomponent vaccine against H. pylori infection based on well selected protective epitopes from relevant antigens incorporated into the CTA1-DD adjuvant platform.

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 MIP1β 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 MIP1β 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.

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.

Oral immunotherapy with immunodominant T-cell epitope peptides alleviates allergic reactions in a Balb/c mouse model of egg allergy

BACKGROUND

  Allergen-specific T-cell epitopes are obvious targets for immunotherapeutic interventions in allergic disease. T-cell epitope peptides given orally may provide a practical way of inducing tolerance and preventing allergy.

OBJECTIVE

  This study investigates oral immunotherapy (OIT) with T-cell epitope peptides of the dominant egg-white allergen ovomucoid (Ovm) in a Balb/c mouse model of egg allergy.

METHODS

  Groups of mice were orally sensitized to Ovm and subsequently administered Ovm T-cell epitopes [single peptide 157-171 (SP) or multiple peptide (157-171)(3) (MP)], followed by oral challenge with Ovm. Outcomes post oral challenge were measured as clinical signs, serum histamine, antibody activity (IgG, IgE, IgG1, IgG2, IgA), cytokines (IL-4, IFN-γ, IL-12p70, IL-10, TGF-β, and IL-17), and T regulatory cells (Tregs).

RESULTS

  Clinical signs were less frequent in both SP and MP groups (P ≤ 0.05). Specific IgE was less and IgA was more in both groups; however, SP-treated mice had less histamine and IgG1 and more IgG2-related antibodies indicating a bias toward the type-1 response (P ≤ 0.05). Concentration of type-2 cytokine interleukin-4 (IL-4) was significantly less in both groups and IL-12p70 and IL-10 were more in SP-treated mice (P ≤ 0.001). Interferon-γ, IL-17, and TGF-β did not differ significantly. There was significant increase in the percentage of CD4+FOXP3+ and CD4+CD25+ cells in the SP group, indicating the significant role of Tregs in immune regulation.

CONCLUSION

  In summary, we demonstrated that OIT with SP and MP comprising the immunodominant regions of Ovm was safe and significantly reduced subsequent frequency of allergy to Ovm, and validated potential use of Ovm T-cell epitope as an immunoregulator.

Suppression of ongoing T cell-mediated autoimmunity by peptide-MHC class II dimer vaccination

Tissue-specific autoimmune diseases such as type 1 diabetes (T1D) are characterized by T cell-driven pathology. Administration of autoantigenic peptides provides a strategy to selectively target the pathogenic T cell response. Indeed, treatment with beta cell peptides effectively prevents T1D in NOD mice. However, the efficacy of peptide immunotherapy generally wanes as beta cell autoimmunity progresses and islet inflammation increases. With the goal of enhancing the efficacy of peptide immunotherapy, soluble (s)IA(g7)-Ig dimers covalently linked to beta cell autoantigen-derived peptides were tested for the capacity to suppress late preclinical T1D. NOD female mice with established beta cell autoimmunity were vaccinated i.v. with a short course of sIA(g7)-Ig dimers tethered to peptides derived from glutamic acid decarboxylase (GAD)65 (sIA(g7)-pGAD65). Treatment with sIA(g7)-pGAD65 dimers and the equivalent of only approximately 7 microg of native peptide effectively blocked the progression of insulitis and the development of diabetes. Furthermore, suppression of T1D was dependent on beta cell-specific IL-10-secreting CD4+ T cells, although the frequency of GAD65-specific FoxP3-expressing CD4+ T cells was also increased in sIA(g7)-pGAD65 dimer vaccinated NOD mice. These results demonstrate that MHC class II-Ig dimer vaccination is a robust approach to suppress ongoing T cell-mediated autoimmunity, and may provide a superior strategy of adjuvant-free peptide-based immunotherapy to induce immunoregulatory T cells.

26-Week oral safety study in macaques for transgenic rice containing major human T-cell epitope peptides from Japanese cedar pollen allergens

A study of repeated oral administration of transgenic rice containing a hybrid peptide of major human T-cell epitopes (7Crp) from Japanese cedar pollen allergens was carried out in cynomolgus macaques over 26 weeks. The monkeys were divided into three groups, each comprising three males and three females, administered a high dose of transgenic rice, a low dose of transgenic rice, or a high dose of the parental rice strain. The transgenic rice 7crp#10 and the parental nontransgenic control were polished, steamed, mashed, and prepared in water at 40% (w/v). Monkeys were orally administered a high or low dose of transgenic rice or the nontransgenic control by gavage every day. No adverse effects on general behavior or body weight of animals were observed during the study. Analysis of blood from monkeys administered for 26 weeks showed that, with few exceptions, there were no significant differences in hematological or biochemical values between them. Additionally, neither pathological symptoms nor histopathological abnormalities were observed. Thus, it was concluded that oral administration of transgenic rice containing T-cell epitopes from Japanese cedar pollen allergens has no adverse effects.

CD8+ CTL priming by exact peptide epitopes in incomplete Freund's adjuvant induces a vanishing CTL response, whereas long peptides induce sustained CTL reactivity

Therapeutic vaccination trials, in which patients with cancer were vaccinated with minimal CTL peptide in oil-in-water formulations, have met with limited success. Many of these studies were based on the promising data of mice studies, showing that vaccination with a short synthetic peptide in IFA results in protective CD8(+) T cell immunity. By use of the highly immunogenic OVA CTL peptide in IFA as a model peptide-based vaccine, we investigated why minimal CTL peptide vaccines in IFA performed so inadequately to allow full optimization of peptide vaccination. Injection of the minimal MHC class I-binding OVA(257-264) peptide in IFA transiently activated CD8(+) effector T cells, which eventually failed to undergo secondary expansion or to kill target cells, as a result of a sustained and systemic presentation of the CTL peptides gradually leaking out of the IFA depot without systemic danger signals. Complementation of this vaccine with the MHC class II-binding Th peptide (OVA(323-339)) restored both secondary expansion and in vivo effector functions of CD8(+) T cells. Simply extending the CTL peptide to a length of 30 aa also preserved these CD8(+) T cell functions, independent of T cell help, because the longer CTL peptide was predominantly presented in the locally inflamed draining lymph node. Importantly, these functional differences were reproduced in two additional model Ag systems. Our data clearly show why priming of CTL with minimal peptide epitopes in IFA is suboptimal, and demonstrate that the use of longer versions of these CTL peptide epitopes ensures the induction of sustained effector CD8(+) T cell reactivity in vivo.

Intraoral administration of a T-cell epitope peptide induces immunological tolerance in Cry j 2-sensitized mice

Sublingual immunotherapy using allergen-derived peptides is feasible as a novel specific immunotherapy, but its efficacy has not yet been demonstrated in either humans or animals. In addition, it remains obscure whether the oral immune system is involved in the mechanism of sublingual immunotherapy. Here, we show that the intraoral administration of the T-cell epitope peptide P2-246-259 derived from Cry j 2, a major Japanese cedar (Cryptomeria japonica) pollen allergen, to Cry j 2-sensitized mice induces immunological tolerance, and that ex vivo lymph node cell proliferation to P2-246-259 and Cry j 2 was inhibited. In addition, intraoral administration was shown to be superior to intragastric administration in terms of tolerance induction, suggesting that the oral immune system contributes to the induction of immunological tolerance. Therefore, the significant efficacy of sublingual immunotherapy using a peptide on allergen-specific T-cells was demonstrated in animals, and this may be potentiated by the oral mucosal immune system.

Broad TCR usage in functional HIV-1-specific CD8+ T cell expansions driven by vaccination during highly active antiretroviral therapy

During chronic HIV-1 infection, continuing viral replication is associated with impaired proliferative capacity of virus-specific CD8+ T cells and with the expansion and persistence of oligoclonal T cell populations. TCR usage may significantly influence CD8+ T cell-mediated control of AIDS viruses; however, the potential to modulate the repertoire of functional virus-specific T cells by immunotherapy has not been explored. To investigate this, we analyzed the TCR Vbeta usage of CD8+ T cells populations which were expanded following vaccination with modified vaccinia virus Ankara expressing a HIV-1 gag/multiepitope immunogen (MVA.HIVA) in HIV-1-infected patients receiving highly active antiretroviral therapy. Vaccinations induced the re-expansion of HIV-1-specific CD8+ T cells and these showed broad TCR Vbeta usage which was maintained for at least 1 year in some individuals. By contrast, virus-specific CD8+ T cell populations in the same donors which failed to expand after vaccination and in unvaccinated controls were oligoclonal. Simultaneously, we observed that CD8+ T cells recognizing vaccine-derived HIV-1 epitopes displayed enhanced capacity to proliferate and to inhibit HIV-1 replication in vitro, following MVA.HIVA immunizations. Taken together, these data indicate that an attenuated viral-vectored vaccine can modulate adaptive CD8+ T cell responses to HIV-1 and improve their antiviral functional capacity. The potential therapeutic benefit of this vaccination approach warrants further investigation.

Altered B:9–23 Insulin, When Administered Intranasally with Cholera Toxin Adjuvant, Suppresses the Expression of Insulin Autoantibodies and Prevents Diabetes

Insulin peptide B:9-23 is a major autoantigen in type 1 diabetes that contains two distinct CD4 epitopes (B:9-16 and B:13-23). One of the two epitopes, B:13-23, overlaps with a CTL epitope (B:15-23). In this study, we report that the elimination of the CTL epitope from the B:9-23 peptide by amino acid substitution (with alanine) at positions B:16 and 19 (A16,19 altered peptide ligand) or truncation of the C-terminal amino acids from the peptide (B:9-21), neither of which stimulated the proliferation of insulin B:15-23 reactive CD8 T cells, provided significant intranasally induced suppression of diabetes when coadministered with a potent mucosal adjuvant cholera toxin (CT). Intranasal treatment with A16,19 resulted in the elimination of spontaneous insulin autoantibodies, significant inhibition of insulitis and remission from hyperglycemia, and prevented the progression to diabetes. Intranasal administration of native B:9-23/CT or B:11-23/CT resulted in a significant enhancement of insulin autoantibody expression and severity of insulitis and failed to prevent diabetes. Our present study indicates that elimination of the CTL epitope from the B:9-23 peptide was critically important for mucosally induced diabetes prevention. The A16,19 altered peptide ligand, but not other native insulin peptides, suppresses insulin autoantibodies associated with protection from and remission of diabetes.

Intranasal immunization with a dominant T-cell epitope peptide of a major allergen of olive pollen prevents mice from sensitization to the whole allergen

Mucosal tolerance induction with vaccines based on peptides representing T-cell epitopes of allergens is a promising way for treating allergic diseases. Ole e 1 is the main allergen of olive pollen, which is an important cause of allergy in Mediterranean countries. The aim of this study was to evaluate the ability of the peptide T109-K130 containing a dominant T-cell epitope of Ole e 1, to modulate the allergen-specific immune response in a prophylactic mouse model. Mice were intranasally treated with the peptide 1 week prior to sensitization with Ole e 1. Blood, lungs and spleens were collected and analysed for immune response. Intranasal pretreatment of mice with the peptide led to suppress serum specific IgE, IgG1 and IgG2a antibody levels, and markedly reduced proliferative T-cell response and Th2-cytokine production, but increased IFN-gamma secretion in spleen cell cultures. Increased mRNA IL-10 levels were observed in lungs from pretreated mice. Pathologic alterations of the lung associated with airway inflammation (peribronchial/perivascular infiltrates, eosinophilia and mucus production) were significantly suppressed after pretreatment. Similar results were obtained when mice were sensitized 10 weeks after treatment. Our results demonstrate that intranasal administration of a single T-cell peptide protects mice against subsequent sensitization to the allergen, possibly via IFN-gamma and IL-10. This study emphasizes the usefulness of nasal peptide T-based vaccines against allergy.

Comparative prime-boost vaccinations using Semliki Forest virus, adenovirus, and ALVAC vectors demonstrate differences in the generation of a protective central memory CTL response against the P815 tumor

Tumor-specific Ags are potential target molecules in the therapeutic treatment of cancer. One way to elicit potent immune responses against these Ags is to use recombinant viruses, which activate both the innate and the adaptive arms of the immune system. In this study, we have compared Semliki Forest virus (SFV), adenovirus, and ALVAC (poxvirus) vectors for their capacity to induce CD8(+) T cell responses against the P1A tumor Ag and to elicit protection against subsequent challenge injection of P1A-expressing P815 tumor cells in DBA/2 mice. Both homologous and heterologous prime-boost regimens were studied. In most cases, both higher CD8(+) T cell responses and better tumor protections were observed in mice immunized with heterologous prime-boost regimens, suggesting that the combination of different viral vectors is beneficial for the induction of an effective immune response. However, homologous immunization with SFV provided potent tumor protection despite a rather moderate primary CD8(+) T cell response as compared with mice immunized with recombinant adenovirus. SFV-immunized mice showed a rapid and more extensive expansion of P1A-specific CD8(+) T cells in the tumor-draining lymph node after tumor challenge and had a higher frequency of CD62L(+) P1A-specific T cells in the blood, spleen, and lymph nodes as compared with adenoimmunized mice. Our results indicate that not only the magnitude but in particular the quality of the CD8(+) T cell response correlates with tumor protection.

Induction of potent CD8+ T-cell responses by novel biodegradable nanoparticles carrying human immunodeficiency virus type 1 gp120

The mainstream of recent anti-AIDS vaccines is a prime/boost approach with multiple doses of the target DNA of human immunodeficiency virus type 1 (HIV-1) and recombinant viral vectors. In this study, we have attempted to construct an efficient protein-based vaccine using biodegradable poly(gamma-glutamic acid) (gamma-PGA) nanoparticles (NPs), which are capable of inducing potent cellular immunity. A significant expansion of CD8+ T cells specific to the major histocompatibility complex class I-restricted gp120 epitope was observed in mice intranasally immunized once with gp120-carrying NPs but not with gp120 alone or gp120 together with the B-subunit of cholera toxin. Both the gp120-encapsulating and -immobilizing forms of NPs could induce antigen-specific spleen CD8+ T cells having a functional profile of cytotoxic T lymphocytes. Long-lived memory CD8+ T cells could also be elicited. Although a substantial decay in the effector memory T cells was observed over time in the immunized mice, the central memory T cells remained relatively constant from day 30 to day 238 after immunization. Furthermore, the memory CD8+ T cells rapidly expanded with boosting with the same immunogen. In addition, gamma-PGA NPs were found to be a much stronger inducer of antigen-specific CD8+ T-cell responses than nonbiodegradable polystyrene NPs. Thus, gamma-PGA NPs carrying various HIV-1 antigens may have great potential as a novel priming and/or boosting tool in current vaccination regimens for the induction of cellular immune responses.

TLR3 ligand stimulates fully functional memory CD8+ T cells in the absence of CD4+ T-cell help

We investigated whether Toll-like receptor ligands (TLR-Ls) can bypass the requirement for CD4+ T-cell help in the induction of fully efficient memory CD8+ T cells (cytotoxic T lymphocytes [CTLs]). “Helpless” CTLs were induced by a synthetic CD8+ T-cell epitope administered with TLR3-L and TLR9-L, but not with TLR2/6-L, TLR4-L, or TLR7-L. The up-regulation of MHC-I and costimulatory molecules by dendritic cells following TLR stimulation was not sufficient for the priming of “helpless” CTLs, which depended essentially on the induction of a strong IFN-α/β response. The “helpless” CTLs induced by TLR-Ls differentiated into fully functional memory CTLs able to proliferate as well as their “helped” counterparts upon challenge, in the absence of CD4+ T-cell help.

Functional and phenotypic characterization of tetanus toxoid-specific human CD4+ T cells following re-immunization

The formation of immunological memory is a hallmark of adaptive immunity and the goal of vaccination. For CD8(+ )T cells, successful generation of memory cells has been linked to IL-7 receptor alpha (IL-7Ralpha) expression, suggesting a role for IL-7 signaling, which in turn is important for preventing T cell apoptosis. We thus investigated the kinetics and changes of IL-7Ralpha and anti-apoptotic protein Bcl-2 expression levels in tetanus toxoid (TT)-specific CD4(+ )T cells at different time points prior and after TT re-immunization of TT-immune individuals. Prior to re-immunization, most TT-specific CD4(+ )T cells were high IL-2 producers, CD45RA(-)CCR7(+), IL-7Ralpha(high)Bcl-2(high) cells, resembling typical long-lived central memory cells. Already 5 days, and more importantly at the peak of the response, after TT re-immunization, a substantial fraction of these cells secreted also IFN-gamma, down-regulated CCR7, IL-7Ralpha and Bcl-2 and became Ki67 positive, resembling effector memory cells. In contrast, TT-specific CD4(+ )T cells found 60 days or later after re-immunization were again as baseline. Interestingly, a significant fraction of IL-7Ralpha(high)Bcl-2(high) TT-specific CD4(+ )T cells, i.e. the proposed memory cell precursors, remained stable at any time point upon re-immunization. Together, these results suggest that IL-7Ralpha expression levels might be a useful marker for identifying long-lived Ag-specific CD4(+ )T cells in memory T cells.

Requirement for CD4 T Cell Help in Maintenance of Memory CD8 T Cell Responses Is Epitope Dependent

CD4 Th cells play critical roles in stimulating Ab production and in generating primary or maintaining memory CTL. The requirement for CD4 help in generating and maintaining CTL responses has been reported to vary depending on the vector or method used for immunization. In this study, we examined the requirement for CD4 T cell help in generating and maintaining CTL responses to an experimental AIDS vaccine vector based on live recombinant vesicular stomatitis virus (VSV) expressing HIV Env protein. We found that primary CD8 T cell responses and short-term memory to HIV Env and VSV nucleocapsid (VSV N) proteins were largely intact in CD4 T cell-deficient mice. These responses were efficiently recalled at 30 days postinfection by boosting with vaccinia recombinants expressing HIV Env or VSV N. However, by 60 days postinfection, the memory/recall response to VSV N was lost in CD4-deficient mice, while the recall response HIV Env was partially maintained in the same animals for at least 90 days. This result indicates that there are epitope-specific requirements for CD4 help in the maintenance of memory CD8 T cell responses. Our results also suggest that choice of epitopes might be critical in an AIDS vaccine designed to protect against disease in the context of reduced or declining CD4 T cell help.

Identification and characterization of dominant helper T-cell epitopes in the nucleocapsid protein of severe acute respiratory syndrome coronavirus

By using a series of overlapping synthetic peptides covering 98% of the amino acid sequence of the nucleocapsid protein (NP) of severe acute respiratory syndrome coronavirus (SARS-CoV), four helper T-cell (Th) epitopes (NP11, residues 11 to 25; NP51, residues 51 to 65; NP61, residues 61 to 75; and NP111, residues 111 to 125) in C57BL mice (H-2(b)), four (NP21, residues 21 to 35; NP91, residues 91 to 105; NP331, residues 331 to 345; and NP351, residues 351 to 365) in C3H mice (H-2(k)), and two (NP81, residues 81 to 95; and NP351, residues 351 to 365) in BALB/c mice (H-2(d)) have been identified. All of these peptides were able to stimulate the proliferation of NP-specific T-cell lines or freshly isolated lymph node cells from mice immunized with recombinant NP. Immunization of mice with synthetic peptides containing appropriate Th epitopes elicited strong cellular immunity in vivo, as evidenced by delayed-type hypersensitivity. Priming with the helper peptides (e.g., NP111 and NP351) significantly accelerated the immune response induced by recombinant NP, as determined by the production of NP-specific antibodies. When fused with a conserved neutralizing epitope (SP1143-1157) from the spike protein of SARS-CoV, NP111 and NP351 assisted in the production of high-titer neutralizing antibodies in vivo. These data provide useful insights regarding immunity against SARS-CoV and have the potential to help guide the design of peptide-based vaccines.

Epitope specificity of autoreactive T and B cells associated with experimental autoimmune encephalomyelitis and optic neuritis induced by oligodendrocyte-specific protein in SJL/J mice

The encephalitogenic potential of oligodendrocyte-specific protein (OSP) in mice, its specific localization in the intralamellar tight junctions in CNS myelin, and the detection of autoreactivity against OSP in multiple sclerosis (MS) strongly suggest the relevance of autoreactivity against OSP in the pathogenesis of MS. In this study, we have characterized the autoimmune T and B cells that are associated with clinicopathological manifestations of OSP-induced MS-like disease in mice by using recombinant soluble mouse OSP (smOSP) and synthetic overlapping peptides spanning smOSP. SJL/J mice immunized with smOSP developed chronic relapsing clinical experimental autoimmune encephalomyelitis accompanied with intense perivascular and parenchymal inflammatory infiltrates, widespread demyelination, axonal loss, and remarkable optic neuritis. The smOSP-primed lymph node cells reacted predominantly against OSP55-80 and to a lesser extent also to OSP22-46 and OSP179-207. Unexpectedly, in vitro selection with smOSP resulted in pathogenic smOSP-specific CD4+ T cells that reacted equally well against OSP55-80, OSP22-46, OSP45-66, and OSP179-207. Fine analysis of the anti-OSP autoimmunity revealed that the disease is primarily associated with CD4+ T cells directed against the major (OSP55-80) and the minor (OSP179-207) encephalitogenic regions that were further delineated, both in vitro and in vivo, to OSP55-66 and OSP194-207, respectively. In contrast, the OSP-induced Abs were predominantly directed against OSP22-46; these Abs were mostly of IgG1 isotype, but high levels of IgG2a and IgG2b and significant levels of IgE were also observed. The reactivity of pathogenic T cells to two encephalitogenic regions, OSP55-80 and OSP179-207, and their diverse TCRVbeta gene repertoire may impose difficulties for epitope-directed or TCR-targeting approaches to immune-specific modulation of OSP-related pathogenesis.

CD4+T Cells in the Absence of the CD8+Cytotoxic T Cells Are Critical and Sufficient for NKT Cell-Dependent Tumor Rejection

NKT cells perform crucial roles in tumor surveillance, functioning as regulators of early host response. In this study, we have assessed the effects of NKT activation at the time of tumor Ag immunization, and have evaluated the contributions of CD4+ and CD8+ T cells in tumor rejection during adaptive immune response against live tumor cells. Our data indicate that CD4+ T cells play critical roles, not only in assisting CTL, but also in the orchestration of host response against the tumor. The CD4+ T cells were found to reject the transplanted tumor cells very efficiently under conditions in which the CTLs were removed either genetically, or via the action of anti-CD8 Ab in mice that had been immunized with tumor extracts and alpha-galactosylceramide. Immunization resulted in an NKT cell-dependent antitumor adaptive immune response, which was associated with both CD4+ T cells and cytokine IFN-gamma.

Listeriolysin O-deficient Listeria monocytogenes as a vaccine delivery vehicle: antigen-specific CD8 T cell priming and protective immunity

Strains of Listeria monocytogenes (LM) that are deficient in the virulence factor listeriolysin O (LLO) are highly attenuated and are thought not to elicit protective immunity. This failure has been attributed to the inability of the bacterium to enter the host cell cytosol and access MHC class I Ag processing machinery. We reexamined this issue using recombinant strains of LM that are deficient in LLO but express an additional CD8 T cell epitope derived from lymphocytic choriomeningitis virus. After infection with LLO-deficient strains, we find sizable priming of epitope-specific CD8 T cells and the development of a functional memory cell population. Mice primed with the LLO-deficient LM strain are equally resistant against high-dose challenge with virulent LM as mice primed with wild-type virulent bacteria and also resist heterologous challenge with lymphocytic choriomeningitis virus. Interestingly, priming with a low dose of LLO-deficient LM, which occurred in environment of reduced inflammation (IFN-gamma), allowed rapid amplification of Ag-specific CD8 T cells by booster immunization, despite an undetectable primary response. We conclude that the generation of protective immunity by LLO-deficient strains of LM does in fact occur and that this highly attenuated LM strain may be a useful platform for vaccine delivery.

IL-17 plays an important role in the development of experimental autoimmune encephalomyelitis

IL-17 is a proinflammatory cytokine that activates T cells and other immune cells to produce a variety of cytokines, chemokines, and cell adhesion molecules. This cytokine is augmented in the sera and/or tissues of patients with contact dermatitis, asthma, and rheumatoid arthritis. We previously demonstrated that IL-17 is involved in the development of autoimmune arthritis and contact, delayed, and airway hypersensitivity in mice. As the expression of IL-17 is also augmented in multiple sclerosis, we examined the involvement of this cytokine in these diseases using IL-17(-/-) murine disease models. We found that the development of experimental autoimmune encephalomyelitis (EAE), the rodent model of multiple sclerosis, was significantly suppressed in IL-17(-/-) mice; these animals exhibited delayed onset, reduced maximum severity scores, ameliorated histological changes, and early recovery. T cell sensitization against myelin oligodendrocyte glycoprotein was reduced in IL-17(-/-) mice upon sensitization. The major producer of IL-17 upon treatment with myelin digodendrocyte glycopritein was CD4+ T cells rather than CD8+ T cells, and adoptive transfer of IL-17(-/-) CD4+ T cells inefficiently induced EAE in recipient mice. Notably, IL-17-producing T cells were increased in IFN-gamma(-/-) cells, while IFN-gamma-producing cells were increased in IL-17(-/-) cells, suggesting that IL-17 and IFN-gamma mutually regulate IFN-gamma and IL-17 production. These observations indicate that IL-17 rather than IFN-gamma plays a crucial role in the development of EAE.

Four distinct patterns of memory CD8 T cell responses to chronic murine cytomegalovirus infection

CMVs are beta herpesviruses that establish lifelong latent infection of their hosts. Acute infection of C57BL/6 mice with murine CMV elicits a very broad CD8 T cell response, comprising at least 24 epitopes from 18 viral proteins. In contrast, we show here that the CD8 T cell response in chronically infected mice was dominated by only five epitopes. Altogether, four distinct CD8 T cell kinetic patterns were evident. Responses to some epitopes, including M45, which dominates the acute response, contracted sharply after day 7 and developed into stable long-term memory. The response to m139 underwent rapid expansion and contraction, followed by a phase of memory inflation, whereas the response to an M38 epitope did not display any contraction phase. Finally, responses against two epitopes encoded by the immediate early gene IE3 were readily detectable in chronically infected mice but near the limit of detection during acute infection. CD8 T cells specific for the noninflationary M45 epitope displayed a classic central memory phenotype, re-expressing the lymph node homing receptor CD62L and homeostatic cytokine receptors for IL-7 and IL-15, and produced low levels of IL-2. Responses to two inflationary epitopes, m139 and IE3, retained an effector memory surface phenotype (CD62L(low), IL-7Ralpha(-), IL-15Rbeta(-)) and were unable to produce IL-2. We suggest that immunological choices are superimposed on altered viral gene expression profiles to determine immunodominance during chronic murine CMV infection.

IL-18 bridges innate and adaptive immunity through IFN-gamma and the CD134 pathway

IL-18 induces inflammation resulting in either enhanced protection from pathogens or exacerbation of autoimmunity, and T cells are profoundly activated during these responses. How IL-18 influences T cell activation is unknown, but this study in mice shows that IL-18 boosted Ag-specific T cell clonal expansion of effector T cells and induced a subpopulation of IFN-gamma superproducing T cells. Commitment to IFN-gamma production through IL-18 was independent of NK cells and IL-12 but dependent on host-derived IFN-gamma. To determine how expansion of these effectors occurred, IL-18 was shown to induce OX40L on dendritic cells, whereas peptide stimulation induced CD134 (OX40) on specific T cells. CD134 blockade inhibited T cell effector expansion thereby reducing the number of IFN-gamma superproducers by 12-fold. Thus, independent of IL-12, IL-18 impacts T cell immunity throughout lymphoid and nonlymphoid tissue by bridging the innate and adaptive arms of the immune system through IFN-gamma and the CD134 costimulatory pathway.

A modified tyrosinase-related protein 2 epitope generates high-affinity tumor-specific T cells but does not mediate therapeutic efficacy in an intradermal tumor model

The generation of tumor-specific T cells is hampered by the presentation of poorly immunogenic tumor-specific epitopes by the tumor. Here, we demonstrate that, although CD8+ T cells specific for the self/tumor Ag tyrosinase-related protein 2 (TRP2) are readily detected in tumor-bearing hosts, vaccination of either tumor-bearing or naive mice with an epitope derived from TRP2 fails to generate significant numbers of tetramer-staining TRP2-specific T cells or antitumor immunity. We identified an altered peptide epitope, called deltaV, which elicits T cell responses that are cross-reactive to the wild-type TRP2 epitope. Immunization with deltaV generates T cells with increased affinity for TRP2 compared with immunization with the wild-type TRP2 epitope, although TRP2 immunization often generates a greater number of TRP2-specific T cells based on intracellular IFN-gamma analysis. Despite generating higher affinity responses, deltaV immunization alone fails to provide any greater therapeutic efficacy against tumor growth than TRP2 immunization. This lack of tumor protection is most likely a result of both the deletion of high affinity and functional tolerance induction of lower affinity TRP2-specific T cells. Our data contribute to a growing literature demonstrating the ability of variant peptide epitopes to generate higher affinity T cell responses against tumor-specific Ags. However, consistent with most clinical data, simple generation of higher affinity T cells is insufficient to mediate tumor immunity.

Coinoculation with hepatitis B surface and core antigen promotes a Th1 immune response to a multiepitopic protein of HIV-1

It has been defined that strong and multispecific cellular immune responses correlate with a better prognosis during the course of chronic diseases. A cross-enhancing effect on the resulting immune response obtained by the coadministration of recombinant hepatitis B virus (HBV) surface and core Ag was recently observed. With the objective of studying the effect of such Ag on the immune response to coinoculated heterologous Ag and vice versa, several formulations containing the recombinant HBV Ag and a multiepitopic protein (CR3) composed by CTL and Th epitopes from HIV-1 were evaluated by s.c. and mucosal administration. Combinations of two and three Ag were evaluated for cellular and humoral immune responses. The results showed that the best Ag combination for nasal immunization was the mixture comprising the CR3 recombinant HIV protein and both HBV Ag. Similarly, it was also the best formulation for s.c. immunization in aluminium phosphate adjuvant. In conclusion, it is possible to induce a Th1 stimulation of the cellular immune response specific for a HIV-based recombinant protein by formulating this Ag with the recombinant HBV Ag.

Immunogenicity of Liposomes Containing Lipid Core Peptides and the Adjuvant Quil A

PURPOSE

The purpose of this study was to investigate the immunogenicity of liposomes containing mannosylated lipid core peptide (manLCP) constructs, both in vitro and in vivo, with or without the addition of the immune stimulating adjuvant Quil A.

METHODS

Mouse bone marrow dendritic cells (BMDC) were cultured with liposome formulations for 48 h, and the resulting level of BMDC activation was determined by flow cytometry. BMDC pulsed with liposome formulations were incubated with 5,6-carboxyfluoroscein diacetate succinimidyl ester-labeled T cells for 72 h and the resulting T cell proliferation was determined by flow cytometry. To investigate the immunogenicity of formulations in vivo, groups of C57Bl/6J mice were immunized by subcutaneous injection, and the resulting antigen-specific cytotoxic and protective immune responses toward tumor challenge evaluated.

RESULTS

Despite being unable to demonstrate the activation of BMDC, BMDC pulsed with liposomes containing manLCP constructs were able to stimulate the proliferation of naïve T cells in vitro. However, in vivo only liposomes containing both manLCP and Quil A were able to stimulate a strong antigen-specific cytotoxic immune response. Liposomes containing manLCP and Quil A within the same particle were able to protect against the growth of tumor cells to a similar level as if the antigen was administered in alum with CD4 help.

CONCLUSION

ManLCPs administered in liposomes are able to stimulate strong cytotoxic and protective immune responses if Quil A is also incorporated as an adjuvant.

Accumulation of CD8+T Cells in Advanced-Stage Tumors and Delay of Disease Progression following Secondary Immunization against an Immunorecessive Epitope

Self-reactive T cells that survive the process of positive and negative selection during thymocyte development represent potential effector cells against tumors that express these same self-Ags. We have previously shown that CD8+ T lymphocytes (T(CD8)) specific for an immunorecessive epitope, designated epitope V, from the SV40 large T Ag (Tag) escape thymic deletion in line SV11 Tag-transgenic mice. In contrast, these mice are tolerant to the three most dominant Tag epitopes. The majority of the residual epitope V-specific T(CD8) have a low avidity for the target epitope, but a prime/boost regimen can expand higher avidity clones in vivo. Whether higher avidity T(CD8) targeting this epitope are affected by Tag-expressing tumors in the periphery or can be recruited for control of tumor progression remains unknown. In the current study, we determined the fate of naive TCR-transgenic T(CD8) specific for Tag epitope V (TCR-V cells) following transfer into SV11 mice bearing advanced-stage choroid plexus tumors. The results indicate that TCR-V cells are rapidly triggered by the endogenous Tag and acquire effector function, but fail to accumulate within the tumors. Primary immunization enhanced TCR-V cell frequency in the periphery and promoted entry into the brain, but a subsequent booster immunization caused a dramatic accumulation of TCR-V T cells within the tumors and inhibited tumor progression. These results indicate that epitope V provides a target for CD8+ T cells against spontaneous tumors in vivo, and suggests that epitopes with similar properties can be harnessed for tumor immunotherapy.

Neuroprotection induced by mucosal tolerance is epitope-dependent: Conflicting effects in different strains

The ability to cope with ongoing neurodegeneration after injury to the central nervous system of mammals differs among strains and depends in part on the animal's ability to manifest a T-cell-mediated protective response. After CNS injury, strain-related differences were observed. Moreover, the post-injury effect of naturally occurring regulatory CD4+CD25+ T cells was found to differ in different strains. In this study, using partially injured optic nerves of Balb/c/OLA and C57BL/6J mice as models, we observed strain-related differences in the T-cell-mediated protection obtained by antigens administered via the nasal route. Active immunization with myelin-related antigens emulsified in complete Freund's adjuvant had a beneficial effect on both strains, whereas mucosal administration of the same antigens was destructive in mice of the Balb/c/OLA strain but protective in C57BL/6J mice.

An increase in antimycobacterial Th1-cell responses by prime-boost protocols of immunization does not enhance protection against tuberculosis

Bordetella pertussis adenylate cyclase (CyaA) toxoid is a powerful nonreplicative immunization vector targeting dendritic cells, which has already been used successfully in prophylactic and therapeutic vaccination in various preclinical animal models. Here, we investigated the potential of CyaA, harboring strong mycobacterial immunogens, i.e., the immunodominant regions of antigen 85A or the complete sequence of the 6-kDa early secreted antigenic target (ESAT-6) protein, to induce antimycobacterial immunity. By generating T-cell hybridomas or by using T cells from mice infected with mycobacteria, we first demonstrated that the in vitro delivery of 85A or ESAT-6 to antigen-presenting cells by CyaA leads to processing and presentation, by major histocompatibility complex class II molecules, of the same epitopes as those displayed upon mycobacterial infection. Importantly, compared to the recombinant protein alone, the presentation of ESAT-6 in vitro was 100 times more efficient upon its delivery to antigen-presenting cells in fusion to CyaA. Immunization with CyaA-85A or CyaA-ESAT-6 in the absence of any adjuvant induced strong antigen-specific lymphoproliferative, interleukin-2 (IL-2) and gamma interferon (IFN-gamma) cytokine responses, in the absence of any IL-4 or IL-5 production. When used as boosters after priming with a BCG expressing ESAT-6, the CyaA-85A and CyaA-ESAT-6 proteins were able to strikingly increase the sensitivity and intensity of proliferative and Th1-polarized responses and notably the frequency of antigen-specific IFN-gamma-producing CD4+ T cells. However, immunization with these CyaA constructs as subunit vaccines alone or as boosters did not allow induction or improvement of protection against Mycobacterium tuberculosis infection. These results question the broadly admitted correlation between the frequency of IFN-gamma-producing CD4+ T cells and the level of protection against tuberculosis.

Intranasal lipopeptide primes lung-resident memory CD8+ T cells for long-term pulmonary protection against influenza

The longevity of the influenza virus-specific CD8+ T cell response following intranasal delivery of a synthetic lipopeptide was investigated and the characteristics and location of the cells associated with viral clearance examined. The lipopeptide, incorporating an epitope for CD8+ T cells and another for CD4+ T cells with the lipid moiety S-[2,3-bis(palmitoyloxy)propyl]cysteine (Pam2Cys) attached, induced potent and long-lived pulmonary protection. Both the lipopeptide and its largely unprotective non-lipidated counterpart elicited comparable numbers of CD8+ T cells in the spleen, which was the main location of the memory pool. However, the lipopeptide, unlike the non-lipidated peptide, also induced a substantial memory population that remained in the lungs and was rapidly activated upon viral challenge months later. These lipopeptide-induced lung-resident CD8+ T cells were also very similar in number and IFN-gamma-secreting potential to those induced by prior exposure to the virus itself and are likely mediators of initial viral clearance prior to recruitment from the expanding lymph node T cell pool. Significant clearing responses were demonstrated as late as 9 months post-lipopeptide vaccination. This study shows that CD8+ T cells primed by the lipopeptide are not only long-lived but can take up residence in the lung where they are important early mediators of pulmonary protection.

Inducing systemic and mucosal immune responses to B-T construct of F1 antigen of Yersinia pestis in microsphere delivery

Plague is a zoonotic disease caused by Yersinia pestis, an etiological agent of pneumonic and bubonic plague. There is a need for an improved plague vaccine that may overcome the limitation of presently available whole cell vaccine. An alternative approach described here, is the use of protective epitopes from immunodominant antigen of Y. pestis. One such antigen is the F1 antigen, a major envelope and virulent protein that possess antiphagocytic and anti-microbial properties. The present study was aimed to develop a peptide-based vaccine, based upon the constructs made between B and T cell epitopes of F1 antigen of Y. pestis. The immunogenicity, IgG subclass pattern, affinity, avidity and in vivo protective efficacy of the antibodies generated for different B-T constructs were studied in murine model using microsphere as the delivery vehicle. The mode of immunization was both intranasal and intramuscular, with single and multiple doses of immunization, respectively. Intranasal immunization generated consistent high titre and long lasting immune response both for IgG and IgA in sera and sIgA in washes while intramuscular route generated peak IgG levels in sera only. The IgG isotypic levels pattern showed higher IgG2a/IgG2b levels in intranasal route while mixed isotypic levels of IgG1, IgG2a/IgG2b were observed in intramuscular route. The affinity and relative avidity of antibodies showed best results with intranasal route as compared to the intramuscular route. The specific activity measurement (IgG/IgA content) in sera and washes were well correlated with the antibody levels. Finally, in vivo protective studies showed that B1T1 and B2T1 conjugates protected the mice till day 15 while rest of the conjugates showed poor protection.

Immune deviation by mucosal antigen administration suppresses gene-transfer-induced inhibitor formation to factor IX

Formation of inhibitory antibodies is a serious complication of protein or gene replacement therapy for hemophilias, congenital X-linked bleeding disorders. In hemophilia B (coagulation factor IX [F.IX] deficiency), lack of endogenous F.IX antigen expression and other genetic factors may increase the risk of antibody formation to functional F.IX. Here, we developed a protocol for reducing inhibitor formation in gene therapy by prior mucosal (intranasal) administration of a peptide representing a human F.IX-specific CD4(+) T-cell epitope in hemophilia B mice. C3H/HeJ mice with a F.IX gene deletion produced inhibitory IgG to human F.IX after hepatic gene transfer with an adeno-associated viral vector. These animals subsequently lost systemic F.IX expression. In contrast, repeated intranasal administration of the specific peptide resulted in reduced inhibitor formation, sustained circulating F.IX levels, and sustained partial correction of coagulation following hepatic gene transfer. This was achieved through immune deviation to a T-helper-cell response with increased IL-10 and TGF-beta production and activation of regulatory CD4(+)CD25(+) T cells.

Identification of protective and non-protective T cell epitopes in influenza

Understanding the immune response to different CD8 T cell epitopes is important for the development of vaccines designed to promote protective cellular immunity. Recently, we have shown that vaccination with the PA(224-233)/D(b) epitope of influenza virus was poorly protective in terms of viral clearance. To determine if other influenza virus epitopes behave in this manner, we analyzed the ability of three newly identified CD8 T cell epitopes and three previously defined epitopes to provide protection following vaccination and viral challenge. All six of the peptide-based vaccinations resulted in significantly increased numbers of epitope-specific CD8 T cells in the spleen. Interestingly, we found that vaccination with three peptides (HA(332-340), M1(128-135), or PA(224-233)) resulted in delayed viral clearance following infection. These findings indicate that some epitopes have a detrimental impact on viral clearance and have important implications for the development of vaccination strategies designed to provide protection against subsequent influenza virus challenge.

Development of a novel Ag-specific immunotherapy using CpG oligodeoxynucleotides in a new, unique mouse cutaneous eosinophilic inflammation model

The number of patients with severe atopic dermatitis (AD) has been on the rise recently. We are therefore urgently in need of a treatment that can suppress Th2 cell-mediated responses in an Ag-specific fashion. Oligodeoxynucleotides (ODN)containing CpG motifs (CpG ODN) have been highlighted as immunomodulators that reduce Th2-mediated responses. To determine the effect of CpG ODN on Th2-mediated skin inflammation, we first developed a reproducible murine model of protein Ag-induced eosinophilic inflammation that is accompanied by epidermal acanthosis and increased serum IgE levels as seen in AD. In this model we found that treatment with CpG ODN during epicutaneous sensitization in previously i.p.-primed mice prevented the development of Th2-mediated responses. Furthermore, to evaluate the therapeutic effect of CpG ODN on established eosinophilic inflammation, mice were treated with a course of the immunotherapy at a skin site remote from the area of Ag application prior to the second 1-wk epicutaneous exposure to Ag. Therapeutic treatment with CpG ODN plus Ag, but not that with CpG ODN alone, could reverse the established eosinophilic inflammation. The presented results provide strong evidence for the feasibility of a novel Ag-specific immunomodulator to treat cutaneous eosinophilic inflammation such as that characteristically found in patients with severe AD.

Prevention of allergy by a recombinant multi-allergen vaccine with reduced IgE binding and preserved T cell epitopes

Novel approaches for the prevention of allergy are required, because of the inevitably increasing prevalence of allergic diseases during the last 30 years. Here, a recombinant chimeric protein, which comprises the whole amino acid sequences of three bee venom major allergens has been engineered and used in prevention of bee venom sensitization in mice. Phospholipase A2 (Api m 1), hyaluronidase (Api m 2) and melittin (Api m 3) fragments with overlapping amino acids were assembled in a different order in the Api m (1/2/3) chimeric protein, which preserved entire T cell epitopes, whereas B cell epitopes of all three allergens were abrogated. Accordingly, IgE cross-linking leading to mast cell and basophil mediator release was profoundly reduced in humans. Supporting these findings, the Api m (1/2/3) induced 100 to 1000 times less type-1 skin test reactivity in allergic patients. Treatment of mice with Api m (1/2/3) led to a significant reduction of specific IgE development towards native allergen, representing a protective vaccine effect in vivo. These results demonstrate a novel prototype of a preventive allergy vaccine, which preserves the entire T cell epitope repertoire, but bypasses induction of IgE against native allergen, and side effects related to mast cell/basophil IgE FcepsilonRI cross-linking in sensitized individuals.

Peptide-induced immune protection of CD8+ T cell-deficient mice against Friend retrovirus-induced disease

CD8+ CTLs and virus-neutralizing antibodies have been associated with spontaneous and vaccine-induced immune control of retroviral infections. We previously showed that a single immunization with an env gene-encoded CD4+ T cell epitope protected mice against fatal Friend retrovirus infection. Here, we analyzed immune cell components required for the peptide-induced anti-retroviral protection. Mice lacking CD8+ T cells were nevertheless protected against Friend virus infection, while mice lacking B cells were not. Virus-producing cells both in the spleen and bone marrow decreased rapidly in their number and became undetectable by 4 weeks after infection in the majority of the peptide-immunized animals even in the absence of CD8+ T cells. In the vaccinated animals the production and class switching of virus-neutralizing and anti-leukemia cell antibodies were facilitated; however, virus-induced erythroid cell expansion was suppressed before neutralizing antibodies became detectable in the serum. Further, the numbers of virus-producing cells in the spleen and bone marrow in the early stage of the infection were smaller in the peptide-immunized than in unimmunized control mice in the absence of B cells. Thus, peptide immunization facilitates both early cellular and late humoral immune responses that lead to the effective control of the retrovirus-induced disease, but CD8+ T cells are not crucial for the elimination of virus-infected cells in the peptide-primed animals.

A shared epitope of the interphotoreceptor retinoid-binding protein recognized by the CD4+ and CD8+ autoreactive T cells

We previously demonstrated that cultures of rat uveitogenic T cells rapidly become dominated by CD4+ cells, but activation of CD8+ autoreactive T cells also occurred during the in vitro culture of in vivo-primed T cells. In the present study, we show that the commonly used uveitogenic peptide, interphotoreceptor retinoid-binding protein (IRBP) 1-20, generated both CD4+ and CD8+ autoreactive T cells in the C57BL/6 (B6) mouse and that this 20-mer contains at least two distinct antigenic epitopes. To determine whether the CD8 response was Ag-specific and whether CD4+ and CD8+ IRBP1-20-specific T cells recognize distinct antigenic epitopes, we prepared highly purified CD4+ and CD8+ T cells from IRBP1-20-primed mice and tested their proliferative response to a large panel of truncated peptides derived from IRBP1-20. The results showed that both CD4+ and CD8+ T cells recognized the same spectrum of peptides. In addition, peptides P10-18 were found to bind effectively to CD8+ IRBP1-20-specific T cells when complexed with recombinant H-2K(b) and also stimulate the proliferation and cytokine production of CD4+ IRBP1-20-specific T cells. Our results document for the first time that CD8+ and CD4+ autoreactive T cells display characteristic epitope recognition and they both recognize the same core epitope.

Combined conjugate vaccines: enhanced immunogenicity with the N19 polyepitope as a carrier protein

The N19 polyepitope, consisting of a sequential string of universal human CD4(+)-T-cell epitopes, was tested as a carrier protein in a formulation of combined glycoconjugate vaccines containing the capsular polysaccharides (PSs) of Neisseria meningitidis serogroups A, C, W-135, and Y. Good antibody responses to all four polysaccharides were induced by one single immunization of mice with N19-based conjugates. Two immunizations with N19 conjugates elicited anti-MenACWY antibody titers comparable to those induced after three doses of glycoconjugates containing CRM197 as carrier protein. Compared to cross-reacting material (CRM)-based constructs, lower amounts of N19-MenACWY conjugates still induced high bactericidal titers to all four PSs. Moreover, N19-MenACWY-conjugated constructs induced faster and higher antibody avidity maturation against meningococcal C PS than CRM-based conjugates. Very importantly, N19-specific antibodies did not cross-react with the parent protein from which N19 epitopes were derived, e.g., tetanus toxoid and influenza virus hemagglutinin. Finally, T helper epitopes of the N19 carrier protein were effectively generated both in vivo (after immunization with the N19 itself) and in vitro (after restimulation of epitope-specific spleen cells). Taken together, these data show that the N19 polyepitope represents a strong and valid option for the generation of improved or new combined glycoconjugate vaccines.

Adult and cord blood T cells can acquire HA-1 specificity through HA-1 T-cell receptor gene transfer

BACKGROUND AND OBJECTIVES

Minor histocompatibility antigen (mHag)-specific graft-versus-leukemia reactivities are observed following unselected donor lymphocyte infusion for the treatment of relapse after HLA-matched mHag-mismatched stem cell transplantation (SCT). Adoptive transfer of donor-derived ex vivo-generated HA-1-specific oligoclonal T cells or HA-1 peptide patient vaccination are currently being explored as curative tools for stem cell based immunotherapy of hematologic malignancies. Another treatment modality to eradicate residual leukemic cells after SCT is the transfer of the HA-1 hematopoietic-specific T-cell receptor (TCR) into cells from the stem cell donor. This strategy would be particularly useful in case of relapse after cord blood transplantation (CBT) and is explored in this study.

DESIGN AND METHODS

HLA-A2(neg) adult peripheral blood and cord blood mononuclear cells were transduced with the genes encoding the HA-1 alpha and beta TCR chains derived from established HA-1 specific cytotoxic T lymphocyte clones.

RESULTS

The T cells transduced with HA-1 TCR alpha beta showed consistent marker gene expression, but low staining with HLA-A2/HA-1 tetrameric complexes. They did, however, show hematopoietic-restricted cytolytic activity against HLA-A2(pos)/HA-1(pos) target cells, including leukemic cells.

INTERPRETATION AND CONCLUSIONS

The low level of HA-1-specific tetramer staining of HA-1 TCR alpha beta transduced T cells may be caused by hybrid TCR formation of the transferred TCRalpha and beta chains with endogenous TCR alpha and beta chains. This may cause unwanted alloreactivity and requires attention. The HA-1 TCR alpha beta transduced T cells show that the HA-1 TCR can be functionally transferred into donor mononuclear cells, which can be exploited in immunotherapeutic settings of SCT and CBT for hematologic malignancies.

Inefficient cross-presentation limits the CD8+ T cell response to a subdominant tumor antigen epitope

CD8(+) T lymphocytes (T(CD8)) responding to subdominant epitopes provide alternate targets for the immunotherapy of cancer, particularly when self-tolerance limits the response to immunodominant epitopes. However, the mechanisms that promote T(CD8) subdominance to tumor Ags remain obscure. We investigated the basis for the lack of priming against a subdominant tumor epitope following immunization of C57BL/6 (B6) mice with SV40 large tumor Ag (T Ag)-transformed cells. Immunization of B6 mice with wild-type T Ag-transformed cells primes T(CD8) specific for three immunodominant T Ag epitopes (epitopes I, II/III, and IV) but fails to induce T(CD8) specific for the subdominant T Ag epitope V. Using adoptively transferred T(CD8) from epitope V-specific TCR transgenic mice and immunization with T Ag-transformed cells, we demonstrate that the subdominant epitope V is weakly cross-presented relative to immunodominant epitopes derived from the same protein Ag. Priming of naive epitope V-specific TCR transgenic T(CD8) in B6 mice required cross-presentation by host APC. However, robust expansion of these T(CD8) required additional direct presentation of the subdominant epitope by T Ag-transformed cells and was only significant following immunization with T Ag-expressing cells lacking the immunodominant epitopes. These results indicate that limited cross-presentation coupled with competition by immunodominant epitope-specific T(CD8) contributes to the subdominant nature of a tumor-specific epitope. This finding has implications for vaccination strategies targeting T(CD8) responses to cancer.