Vaccine-specific CD8 Research Articles

Nanoparticulate STING agonists are potent lymph node-targeted vaccine adjuvants.

Cyclic dinucleotides (CDNs) are agonists of stimulator of IFN genes (STING) and have potential as vaccine adjuvants. However, cyclic di-GMP (cdGMP) injected s.c. shows minimal uptake into lymphatics/draining lymph nodes (dLNs) and instead is rapidly distributed to the bloodstream, leading to systemic inflammation. Here, we encapsulated cdGMP within PEGylated lipid nanoparticles (NP-cdGMP) to redirect this adjuvant to dLNs. Compared with unformulated CDNs, encapsulation blocked systemic dissemination and markedly enhanced dLN accumulation in murine models. Delivery of NP-cdGMP increased CD8+ T cell responses primed by peptide vaccines and enhanced therapeutic antitumor immunity. A combination of a poorly immunogenic liposomal HIV gp41 peptide antigen and NP-cdGMP robustly induced type I IFN in dLNs, induced a greater expansion of vaccine-specific CD4+ T cells, and greatly increased germinal center B cell differentiation in dLNs compared with a combination of liposomal HIV gp41 and soluble CDN. Further, NP-cdGMP promoted durable antibody titers that were substantially higher than those promoted by the well-studied TLR agonist monophosphoryl lipid A and comparable to a much larger dose of unformulated cdGMP, without the systemic toxicity of the latter. These results demonstrate that nanoparticulate delivery safely targets CDNs to the dLNs and enhances the efficacy of this adjuvant. Moreover, this approach can be broadly applied to other small-molecule immunomodulators of interest for vaccines and immunotherapy.

Long-term central and effector SHIV-specific memory T cell responses elicited after a single immunization with a novel lentivector DNA vaccine.

Prevention of HIV acquisition and replication requires long lasting and effective immunity. Given the state of HIV vaccine development, innovative vectors and immunization strategies are urgently needed to generate safe and efficacious HIV vaccines. Here, we developed a novel lentivirus-based DNA vector that does not integrate in the host genome and undergoes a single-cycle of replication. Viral proteins are constitutively expressed under the control of Tat-independent LTR promoter from goat lentivirus. We immunized six macaques once only with CAL-SHIV-IN− DNA using combined intramuscular and intradermal injections plus electroporation. Antigen-specific T cell responses were monitored for 47 weeks post-immunization (PI). PBMCs were assessed directly ex vivo or after 6 and 12 days of in vitro culture using antigenic and/or homeostatic proliferation. IFN-γ ELISPOT was used to measure immediate cytokine secretion from antigen specific effector cells and from memory precursors with high proliferative capacity (PHPC). The memory phenotype and functions (proliferation, cytokine expression, lytic content) of specific T cells were tested using multiparametric FACS-based assays. All immunized macaques developed lasting peripheral CD8+ and CD4+ T cell responses mainly against Gag and Nef antigens. During the primary expansion phase, immediate effector cells as well as increasing numbers of proliferating cells with limited effector functions were detected which expressed markers of effector (EM) and central (CM) memory phenotypes. These responses contracted but then reemerged later in absence of antigen boost. Strong PHPC responses comprising vaccine-specific CM and EM T cells that readily expanded and acquired immediate effector functions were detected at 40/47 weeks PI. Altogether, our study demonstrated that a single immunization with a replication-limited DNA vaccine elicited persistent vaccine-specific CM and EM CD8+ and CD4+ T cells with immediate and readily inducible effector functions, in the absence of ongoing antigen expression.

Nanogel-based immunologically stealth vaccine targets macrophages in the medulla of lymph node and induces potent antitumor immunity.

Because existing therapeutic cancer vaccines provide only a limited clinical benefit, a different vaccination strategy is necessary to improve vaccine efficacy. We developed a nanoparticulate cancer vaccine by encapsulating a synthetic long peptide antigen within an immunologically inert nanoparticulate hydrogel (nanogel) of cholesteryl pullulan (CHP). After subcutaneous injection to mice, the nanogel-based vaccine was efficiently transported to the draining lymph node, and was preferentially engulfed by medullary macrophages but was not sensed by other macrophages and dendritic cells (so-called "immunologically stealth mode"). Although the function of medullary macrophages in T cell immunity has been unexplored so far, these macrophages effectively cross-primed the vaccine-specific CD8(+) T cells in the presence of a Toll-like receptor (TLR) agonist as an adjuvant. The nanogel-based vaccine significantly inhibited in vivo tumor growth in the prophylactic and therapeutic settings, compared to another vaccine formulation using a conventional delivery system, incomplete Freund's adjuvant. We also revealed that lymph node macrophages were highly responsive to TLR stimulation, which may underlie the potency of the macrophage-oriented, nanogel-based vaccine. These results indicate that targeting medullary macrophages using the immunologically stealth nanoparticulate delivery system is an effective vaccine strategy.

ESAT-6 (EsxA) and TB10.4 (EsxH) Based Vaccines for Pre- and Post-Exposure Tuberculosis Vaccination

The ESX systems from Mycobacterium tuberculosis are responsible for the secretion of highly immunogenic proteins of key importance for bacterial survival and growth. The two prototypic proteins, ESAT-6 (EsxA from ESX-1) and TB10.4 (EsxH from ESX-3) share a lot of characteristics regarding genome organization, size, antigenic properties, and vaccine potential but the two molecules clearly have very different roles in bacterial physiology. To further investigate the role of ESAT-6 and TB10.4 as preventive and post-exposure tuberculosis vaccines, we evaluated four different fusion-protein vaccines; H1, H4, H56 and H28, that differ only in these two components. We found that all of these vaccines give rise to protection in a conventional prophylactic vaccination model. In contrast, only the ESAT-6-containing vaccines resulted in significant protection against reactivation, when administered post-exposure. This difference in post-exposure activity did not correlate with a difference in gene expression during infection or a differential magnitude or quality of the vaccine-specific CD4 T cells induced by ESAT-6 versus TB10.4-containing vaccines. The post-exposure effect of the ESAT-6 based vaccines was found to be influenced by the infectious load at the time-point of vaccination and was abolished in chronically infected animals with high bacterial loads at the onset of vaccination. Our data demonstrate that there are specific requirements for the immune system to target an already established tuberculosis infection and that ESAT-6 has a unique potential in post-exposure vaccination strategies.

Pulmonary vaccination against influenza virus induces a protective CD8 T cell response, which is regulated by APCs within the lungs (P6154)

Abstract Recently there has been a renewed interest in the development of novel pulmonary influenza A virus (IAV) vaccines. CD8 T cells play an important role in clearance of IAV, and our prior studies demonstrate a key role for dendritic cells (DCs) in activation of IAV-specific CD8 T cells in the lymph nodes and maintenance in the lungs during IAV infections. Herein, we determined the role of pulmonary vaccine-induced CD8 T cells in protection from IAV challenge and the requirements for generation and maintenance of such CD8 T cell immunity. Our data demonstrates vaccination with IAV virus-like particles (VLPs) containing IAV HA and M1 leads to a significant increase in HA533-specific CD8 T cells. These VLP-specific CD8 T cells mediate protection of mice challenged with lethal doses of either homo- or heterosubtypic IAVs containing the HA533 epitope. Our preliminary results suggest interactions between DCs and effector T cells within the lungs are required following vaccination for maximal pulmonary VLP-specific CD8 T cell responses. Currently, we are investigating the contribution of inflammation and the APC subsets required in generation, boosting, and maintenance of vaccine-specific CD8 T cells during pulmonary vaccination. Collectively, our results highlight an important role for CD8 T cell mediated protection after i.n. vaccination and the seminal role pulmonary APCs play in activating and maintaining local vaccine-specific CD8 T cell responses against IAV in the lungs.

Intravaginal TLR agonists increase local vaccine-specific CD8 T cells and human papillomavirus-associated genital-tumor regression in mice.

Human papillomaviruses (HPV)-related cervical cancer is the second leading cause of cancer death in women worldwide. Despite active development, HPV E6/E7 oncogene-specific therapeutic-vaccines have had limited clinical efficacy to date. Here we report that intravaginal instillation of CpG-ODN (TLR9-agonist) or poly-(I:C) (TLR3-agonist) after subcutaneous E7 vaccination increased approximately 5-fold the number of vaccine-specific IFN-γ-secreting CD8 T-cells in the genital mucosa (GM) of mice, without affecting the E7-specific systemic response. The intravaginal treatment locally increased both E7-specific and total CD8 T-cells, but not CD4 T-cells. This previously unreported selective recruitment of CD8 T-cells from the periphery by intravaginal CpG-ODN or poly-(I:C) was mediated by TLR9 and TLR3/Mda5 signaling-pathways, respectively. For CpG, this recruitment was associated with a higher proportion of GM-localized CD8 T-cells expressing both CCR5 and CXCR3 chemokine receptors and E-selectin ligands. Most interestingly, intravaginal CpG-ODN following vaccination led to complete regression of large genital HPV-tumors in 75% of mice, instead of 20% with vaccination alone. These findings suggest that mucosal application of immunostimulatory molecules might substantially increase the effectiveness of parenterally administered vaccines.

Plasmodium inui Infection Reduces the Efficacy of a Simian Immunodeficiency Virus DNA Vaccine in a Rhesus Macaque Model Through Alteration of the Vaccine-Induced Immune Response

Human immunodeficiency virus type 1 and malaria are co-endemic in many areas. We evaluated the effects of Plasmodium inui infection on the performance of a simian immunodeficiency virus (SIV) DNA vaccine. Rhesus macaques were infected with P. inui by transfusion of whole blood from a persistently infected animal. Animals with and animals without P. inui infection were then vaccinated 4 times with an SIV DNA vaccine encoding SIVgag, SIVpol, and SIVenv. Animals were subsequently challenged with thirty 50% rhesus monkey infectious doses of SIVmac251 6 weeks after the last vaccination. P. inui-infected immunized animals showed a significantly higher viral load than animals without P. inui infection (P=.010, by the Wilcoxon rank sum test). The higher viral loads in the P. inui-infected animals were durable and were observed at all sampling time points across the study (P=.00245, by the Wilcoxon rank test). The P. inui-infected animals also had correspondingly lower CD4(+) cell counts. There were fewer vaccine-specific CD4(+) and CD8(+) cells in the P. inui-infected animals, compared with uninfected animals. Of importance, P. inui infection seemed to decrease the number of CD8(+) cells that could proliferate or secrete interferon γ, although the number of CD8(+) cells capable of secreting tumor necrosis factor α following in vitro stimulation was increased. This study demonstrated that P. inui infection had an influence on the immune response to an SIV DNA vaccine and decreased the vaccine's efficacy.

Intradermal Immunization Triggers Epidermal Langerhans Cell Mobilization Required for CD8 T-Cell Immune Responses

The potential of the skin immune system for the generation of both powerful humoral and cellular immune responses is now well established. However, the mechanisms responsible for the efficacy of skin antigen-presenting cells (APCs) during intradermal (ID) vaccination still remain to be elucidated. We have previously demonstrated in clinical trials that preferential targeting of Langerhans cells (LCs) by transcutaneous immunization shapes the immune response toward vaccine-specific CD8 T cells. Others have shown that ID inoculation of a vaccine, which targets dermal APCs, mobilizes both the cellular and humoral arms of immunity. Here, we investigated the participation of epidermal LCs in response to ID immunization. When human or mouse skin was injected ID with a particle-based vaccine, we observed significant modifications in the morphology of epidermal LCs and their mobilization to the dermis. We further established that this LC recruitment after ID administration was essential for the induction of antigen-specific CD8 T cells, but was, however, dispensable for the generation of specific CD4 T cells and neutralizing antibodies. Thus, epidermal and dermal APCs shape the outcome of the immune responses to ID vaccination. Their combined potential provides new avenues for the development of vaccination strategies against infectious diseases.

Peripheral immunization induces functional intrahepatic Hepatitis C specific immunity following selective retention of vaccine-specific CD8 T cells by the liver

It is believed that an effective HCV vaccine must induce strong HCV-specific cytotoxic IFN-γ+ CD8+ T cells able to migrate into and become fully activated within the liver, an organ known to suppress T cell responses and induce tolerance. Given the importance of intrahepatic HCV-specific T cells in the clearance of acute infection, the goal of this present study was to determine if peripheral immunization was able to induce functional intrahepatic HCV-specific T cell based immunity both in the presence and absence of HCV antigen expression within the liver. Using a novel HCV NS3/NS4A DNA vaccine, we show that peripheral immunization of C57BL/6 mice results in the formation of a large pool of fully functional HCV-specific cytotoxic IFN-γ+ CD8+ T cells within the liver and that these cells were highly enriched within the liver as compared to the spleen. Following hepatic expression of cognate HCV antigen using a previously described liver transfection method, we show that this pool of vaccine-induced HCV-specific CD8+ T cells retained its ability to become highly activated as shown by the upregulation of IFN-γ and CCR5 expression, as well as by the clearance of HCV NS3 expressing hepatocytes. Taken together, these findings suggest that T cell effector function is preserved within the liver and that selective recruitment of antigen-specific T cells to the liver may play a previously unappreciated role in the process of immune surveillance, which may be exploited for future T cell based HCV vaccines.

First-in-human trial focusing on the immunologic effects of the survivin-derived multiepitope vaccine EMD640744.

2515 Background: Survivin is a promising antigen for cancer immunotherapy based on two major criteria: tumor cells depend on its actions, and it has demonstrated immunogenicity in patients with different cancers. Here we report immunomonitoring results of a first-in-man Phase I study (EMR 200032-001) with EMD640744, a cocktail of survivin-derived partially modified HLA class I-restricted peptides in Montanide ISA 51 VG. This multicenter, open-label, parallel group, randomized study compared the immunologic efficacy, safety, tolerability and clinical activity of 3 dosages of sc EMD640744 (30, 100 or 300 µg) in patients with different types of metastatic or locally advanced solid tumors positive for at least one relevant HLA antigen (A1, A2, A3, A24, B7). Methods: Routine immunomonitoring to analyze peptide-specific T cell responses at baseline and at weeks 4, 8, 12, 16, and 17 was performed by IFN-γ ELISpot and peptide/HLA-multimer staining (primary endpoint). Additional analyses were performed by intracellular cytokine staining (ICS) to IL-2, IFNγ, TNFα and degranulation marker CD107a after a single in vitro presensitization for 2 weeks with EMD640744. Results: Routine monitoring displayed T cell responses against the vaccine in 14 of 38 patients (37%) assessed by IFNγ-ELISpot and in 31 of 42 patients (74%) by HLA-multimer staining; 16 responses (38%) were clearly de novo induced. ICS revealed 3 relevant findings: 1) 15 of 22 (68%) analyzed patients showed vaccine-specific CD4+ T cells that could be blocked by anti-HLA-Class II antibodies; 2) survivin-specific CD8+ and CD4+ specific T cells often were polyfunctional, responding with degranulation and production of one or more cytokines; and 3) CD8+ responses against native homologues of modified vaccination peptides were demonstrated in 12 of 13 analyzed patients, and CD4+ responses in 5 of 9 patients. Dose dependency was not observed. Conclusions: Vaccination with EMD640744 elicited de novo T cell responses against survivin peptides in many patients, demonstrating immunological efficacy of EMD640744. The capability of EMD640744 to promote CD4-specific T cell help might explain the remarkable number of successfully induced immune responses.

Pitfalls of vaccinations with WT1-, Proteinase3- and MUC1-derived peptides in combination with MontanideISA51 and CpG7909

T cells with specificity for antigens derived from Wilms Tumor gene (WT1), Proteinase3 (Pr3), and mucin1 (MUC1) have been demonstrated to lyse acute myeloid leukemia (AML) blasts and multiple-myeloma (MM) cells, and strategies to enhance or induce such tumor-specific T cells by vaccination are currently being explored in multiple clinical trials. To test safety and immunogenicity of a vaccine composed of WT1-, Pr3-, and MUC1-derived Class I-restricted peptides and the pan HLA-DR T helper cell epitope (PADRE) or MUC1-helper epitopes in combination with CpG7909 and MontanideISA51, four patients with AML and five with MM were repetitively vaccinated. No clinical responses were observed. Neither pre-existing nor naive WT1-/Pr3-/MUC1-specific CD8+ T cells expanded in vivo by vaccination. In contrast, a significant decline in vaccine-specific CD8+ T cells was observed. An increase in PADRE-specific CD4+ T helper cells was observed after vaccination but these appeared unable to produce IL2, and CD4+ T cells with a regulatory phenotype increased. Taken into considerations that multiple clinical trials with identical antigens but different adjuvants induced vaccine-specific T cell responses, our data caution that a vaccination with leukemia-associated antigens can be detrimental when combined with MontanideISA51 and CpG7909. Reflecting the time-consuming efforts of clinical trials and the fact that 1/3 of ongoing peptide vaccination trails use CpG and/or Montanide, our data need to be taken into consideration.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-010-0929-7) contains supplementary material, which is available to authorized users.

Plasmid DNA vaccination using skin electroporation promotes poly‐functional CD4 T‐cell responses

Plasmid DNA vaccination using skin electroporation (EP) is a promising method able to elicit robust humoral and CD8(+) T-cell immune responses while limiting invasiveness of delivery. However, there is still only limited data available on the induction of CD4(+) T-cell immunity using this method. Here, we compare the ability of homologous prime/boost DNA vaccinations by skin EP and intramuscular (i.m.) injection to elicit immune responses by cytokine enzyme-linked immunosorbent spot (ELISPOT) assay, as well as study the complexity of CD4(+) T-cell responses to the human immunodeficiency virus antigen Gag, using multiparamater flow cytometry. We find that DNA vaccinations by skin EP and i.m. injection are capable of eliciting both single- and poly-functional vaccine-specific CD4(+) T cells. However, although DNA delivered by skin EP was administered at a five-fold lower dose it elicited significant increases in the magnitude of multiple-cytokine producers compared with i.m. immunization suggesting that the skin EP could provide greater poly-functional T-cell help, a feature associated with successful immune defense against infectious agents.

Immunization with Cocktail of HIV-Derived Peptides in Montanide ISA-51 Is Immunogenic, but Causes Sterile Abscesses and Unacceptable Reactogenicity

BackgroundA peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA).MethodsLow-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, 51Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens.Results24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions.ConclusionsThe severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events.Trial RegistrationClinicalTrials.gov NCT00000886

Preferential Amplification of CD8 Effector-T Cells after Transcutaneous Application of an Inactivated Influenza Vaccine: A Randomized Phase I Trial

BackgroundCurrent conventional vaccination approaches do not induce potent CD8 T-cell responses for fighting mostly variable viral diseases such as influenza, avian influenza viruses or HIV. Following our recent study on vaccine penetration by targeting of vaccine to human hair follicular ducts surrounded by Langerhans cells, we tested in the first randomized Phase-Ia trial based on hair follicle penetration (namely transcutaneous route) the induction of virus-specific CD8 T cell responses.Methods and FindingsWe chose the inactivated influenza vaccine – a conventional licensed tetanus/influenza (TETAGRIP®) vaccine – to compare the safety and immunogenicity of transcutaneous (TC) versus IM immunization in two randomized controlled, multi-center Phase I trials including 24 healthy-volunteers and 12 HIV-infected patients. Vaccination was performed by application of inactivated influenza vaccine according to a standard protocol allowing the opening of the hair duct for the TC route or needle-injection for the IM route. We demonstrated that the safety of the two routes was similar. We showed the superiority of TC application, but not the IM route, to induce a significant increase in influenza-specific CD8 cytokine-producing cells in healthy-volunteers and in HIV-infected patients. However, these routes did not differ significantly for the induction of influenza-specific CD4 responses, and neutralizing antibodies were induced only by the IM route. The CD8 cell response is thus the major immune response observed after TC vaccination.ConclusionsThis Phase Ia clinical trial (Manon05) testing an anti-influenza vaccine demonstrated that vaccines designed for antibody induction by the IM route, generate vaccine-specific CD8 T cells when administered transcutaneously. These results underline the necessity of adapting vaccination strategies to control complex infectious diseases when CD8 cellular responses are crucial. Our work opens up a key area for the development of preventive and therapeutic vaccines for diseases in which CD8 cells play a crucial role.Trial RegistrationClinicaltrials.gov NCT00261001

Peptide Vaccination Breaks Tolerance to HER-2/neuby Generating Vaccine-Specific FasL+ CD4+ T Cells: First Evidence for Intratumor Apoptotic Regulatory T Cells

BALB/c mice transgenic (Tg) for the transforming rat neu oncogene (BALB-neuT) are genetically predestined to develop mammary carcinogenesis in a process similar to that in humans. We crossed HLA-A2.1/HLA-DR1 (A2.1/DR1) Tg mice with BALB-neuT mice to generate A2.1/DR1 x BALB-neuT triple Tg (A2.1/DR1 x neuT(+)) mice, which represent an improvement over BALB-neuT mice for evaluating vaccination regimens to overcome tolerance against HER-2/neu. A vaccine formulation strategy, consisting of synthetic peptides from the rat HER-2/neu oncogene combined with granulocyte macrophage colony-stimulating factor, was highly effective in preventing the growth of established transplantable tumors in male A2.1/DR1 x neuT(+) mice. Vaccination with HER-2(435-443) (p435) CTL peptide alone induced weak antitumor responses, which were characterized by increased numbers of regulatory T cells (Treg) and low numbers of vaccine-specific CD8(+) CTL and helper T cells (Th). The administration of p435 plus HER-2(776-790) (p776; helper peptide) reversed this situation, inducing functionally active, peptide-specific CTL and Th. There was a striking change in the intratumoral balance of Tregs (decrease) and vaccine-specific Th (increase) that directly correlated with tumor rejection. Intratumoral administration of anti-FasL antibody promoted tumor growth. The decrease in Tregs (Fas(+)) was due to apoptosis induced by cell contact with Fas ligand(+) (L)(+) Th. Mice vaccinated with p435 plus p776 exhibited long-lasting antitumor immunity. Our vaccine regimen also significantly delayed the outgrowth of mammary carcinomas in female A2.1/DR1 x neuT(+) animals. We provide a mechanism to overcome tolerance against HER-2/neu, which proposes a combined vaccination with two (Th and CTL) HER-2 peptides against HER-2/neu-expressing tumors.

Characterization of T-Cell Responses in Macaques Immunized with a Single Dose of HIV DNA Vaccine

The optimization of immune responses (IR) induced by HIV DNA vaccines in humans is one of the great challenges in the development of an effective vaccine against AIDS. Ideally, this vaccine should be delivered in a single dose to immunize humans. We recently demonstrated that the immunization of mice with a single dose of a DNA vaccine derived from pathogenic SHIV(KU2) (Delta4SHIV(KU2)) induced long-lasting, potent, and polyfunctional HIV-specific CD8(+) T-cell responses (G. Arrode, R. Hegde, A. Mani, Y. Jin, Y. Chebloune, and O. Narayan, J. Immunol. 178:2318-2327, 2007). In the present work, we expanded the characterization of the IR induced by this DNA immunization protocol to rhesus macaques. Animals immunized with a single high dose of Delta4SHIV(KU2) DNA vaccine were monitored longitudinally for vaccine-induced IR using multiparametric flow cytometry-based assays. Interestingly, all five immunized macaques developed broad and polyfunctional HIV-specific T-cell IR that persisted for months, with an unusual reemergence in the blood following an initial decline but in the absence of antibody responses. The majority of vaccine-specific CD4(+) and CD8(+) T cells lacked gamma interferon production but showed high antigen-specific proliferation capacities. Proliferative CD8(+) T cells expressed the lytic molecule granzyme B. No integrated viral vector could be detected in mononuclear cells from immunized animals, and this high dose of DNA did not induce any detectable autoimmune responses against DNA. Taken together, our comprehensive analysis demonstrated for the first time the capacity of a single high dose of HIV DNA vaccine alone to induce long-lasting and polyfunctional T-cell responses in the nonhuman primate model, bringing new insights for the design of future HIV vaccines.

Delaying BCG vaccination from birth to 10 weeks of age may result in an enhanced memory CD4 T cell response

Background In most tuberculosis (TB) endemic countries, bacillus Calmette–Guérin (BCG) is usually given around birth to prevent severe TB in infants. The neonatal immune system is immature. Our hypothesis was that delaying BCG vaccination from birth to 10 weeks of age would enhance the vaccine-induced immune response. Methods In a randomized clinical trial, BCG was administered intradermally either at birth ( n = 25) or at 10 weeks of age ( n = 21). Ten weeks after vaccination, and at 1 year of age, vaccine-specific CD4 and CD8 T cell responses were measured with a whole blood intracellular cytokine assay. Results Infants who received delayed BCG vaccination demonstrated higher frequencies of BCG-specific CD4 T cells, particularly polyfunctional T cells co-expressing IFN-γ, TNF-α and IL-2, and most strikingly at 1 year of age. Conclusions Delaying BCG vaccination from birth to 10 weeks of age enhances the quantitative and qualitative BCG-specific T cell response, when measured at 1 year of age.

AIDSVAX immunization induces HIV-specific CD8+ T-cell responses in high-risk, HIV-negative volunteers who subsequently acquire HIV infection

Correlates of immune protection from HIV vaccines remain undefined. The first HIV vaccine efficacy trial in the US and Europe VAX004, was designed to assess whether rgp120 envelope subunits (AIDSVAX B/B, VaxGen) can induce partial or complete protection from HIV-1 infection. No effectiveness in the reduction of either the acquisition of infection or levels of plasma viremia after HIV infection was noted. We found evidence of vaccine-specific CD8+ T cells in volunteers who received the vaccine, regardless of behavioral risk. Surprisingly, the CD8-response is significantly higher in participants who would go on to contract HIV infection. These results suggest that AIDSVAX immunization may boost preexisting immune responses—due to pre-infection exposure, and a vaccine-induced immune profile may serve as a biological marker for HIV susceptibility.

Developing an HIV cytotoxic T‐lymphocyte vaccine: issues of CD8 T‐cell quantity, quality and location

Issues of quantity, quality and location impact the ability of CD8 T cells to mediate protection from infection. These issues are considered in light of human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) vaccination. Methods are reviewed that result in 100- to 1000-fold higher frequencies of vaccine-specific memory CD8 T cells than that achieved by current HIV/SIV vaccine approaches. Data demonstrating that location within mucosal tissues has a direct impact on memory CD8 T-cell function are discussed. Arguments are made that establishing memory CD8 T cells within mucosal sites of transmission, a priori to natural infection, may be essential for conferring optimal and rapid protection. Lastly, it is proposed that heterologous prime-boost vaccination with recombinant live replicating vectors, which has the potential to induce tremendous numbers of cytolytic memory CD8 T cells within mucosal tissues, would provide a far more stringent test of the hypothesis that memory CD8 T cells could, in principal, form the basis for a preventative HIV vaccine.

Immunogenicity and Antileukemic Activity of Dendritic Cells Electroporated with Wilms' Tumor WT1 mRNA: A Phase I/II Trial in Acute Myeloid Leukemia

The Wilms' tumor protein WT1 is a target for immunotherapy in malignancies, such as acute myeloid leukemia (AML). Following our demonstration that dendritic cells (DC) can be efficiently transfected by messenger (m)RNA electroporation (Van Tendeloo VF et al. Blood 2001; 98:49–56) and that WT1 mRNA-electroporated DC stimulate WT1-specific T cells in vitro (Van Driessche A et al. Leukemia 2005; 19:1863–1871), we performed a phase I/II dose-escalation trial, in which patients with AML in remission but at high risk of relapse and without a direct sib allo-transplant option (9 patients) or with slowly progressive AML (1 patient) received intradermal injections of WT1 RNA-loaded DC. Following apheresis and CD14 immunomagnetic monocyte separation, DC were generated in 6-day cultures in clinical-grade medium supplemented with serum, granulocytemacrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, matured with prostaglandin (PG)E2 and tumor necrosis factor (TNF)-alpha, harvested, electroporated with WT1 mRNA and used as vaccines. The patients received four biweekly DC vaccines and a delayed-type hypersensitivity (DTH) test was performed 2 weeks following the last vaccination. Patients were monitored for minimal residual disease (MRD) by analyzing WT1 RNA expression in peripheral blood by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) (Cilloni D et al. Leukemia 2002; 16:2115–2121 & Cilloni D et al. Haematologica 2008; 93:921–924). Before and after vaccination, peripheral blood was collected for immunomonitoring purposes. Feasibility, safety, immunogenicity and effect on MRD were investigated. There was successful DC generation and vaccine production in all 10 patients. No serious adverse events or toxicity were observed and vaccinations were well tolerated. A decrease in WT1 RNA expression was observed during the course of the vaccination in 4/7 patients who had an increased WT1 mRNA level in peripheral blood. Three of those patients are still in complete hematological remission. An in vivo vaccine-specific immune response was demonstrated in 10/10 patients by DTH. Ex vivo immunomonitoring analysis showed a significant increase in circulating activated HLA-DR+ CD4+ T cells and in IL-2 plasma levels following vaccination. Importantly, in vitro restimulation assays of peripheral blood mononuclear cells revealed a significant postvaccination increase in interferon (IFN)-gamma-producing WT1-specific CD8+ T cells (n= 8 evaluable patients), but not in cytokine-producing WT1-specific CD4+ T cells. There was no significant change in WT1-specific antibodies following vaccination. We conclude that vaccination of AML patients with WT1 RNA-loaded DC is feasible and safe. Furthermore, the DC elicit vaccine-specific and WT1-specific CD8+ T-cell responses. The correlation between reduction of circulating WT1 mRNA and the administration of the DC vaccines strongly suggests that this DC vaccine elicits an antileukemic activity.