Dynamic regulation of functionally distinct virus-specific T cells

Dynamical Modeling and Qualitative Analysis of a Delayed Model for CD8 T Cells in Response to Viral Antigens

Although the immune effector CD8 T cells play a crucial role in clearance of viruses, the mechanisms underlying the dynamics of how CD8 T cells respond to viral infection remain largely unexplored. Here, we develop a delayed model that incorporates CD8 T cells and infected cells to investigate the functional role of CD8 T cells in persistent virus infection. Bifurcation analysis reveals that the model has four steady states that can finely divide the progressions of viral infection into four states, and endows the model with bistability that has ability to achieve the switch from one state to another. Furthermore, analytical and numerical methods find that the time delay resulting from incubation period of virus can induce a stable low-infection steady state to be oscillatory, coexisting with a stable high-infection steady state in phase space. In particular, a novel mechanism to achieve the switch between two stable steady states, time-delay-based switch, is proposed, where the initial conditions and other parameters of the model remain unchanged. Moreover, our model predicts that, for a certain range of initial antigen load: 1) under a longer incubation period, the lower the initial antigen load, the easier the virus infection will evolve into severe state; while the higher the initial antigen load, the easier it is for the virus infection to be effectively controlled and 2) only when the incubation period is small, the lower the initial antigen load, the easier it is to effectively control the infection progression. Our results are consistent with multiple experimental observations, which may facilitate the understanding of the dynamical and physiological mechanisms of CD8 T cells in response to viral infections.

AIM™ platform: A new immunotherapy approach for viral diseases

In addition to complications of acute diseases, chronic viral infections are linked to both malignancies and autoimmune disorders. Lack of adequate treatment options for Epstein-Barr virus (EBV), Human T-lymphotropic virus type 1 (HTLV-1), and human papillomavirus (HPV) remains. The NexImmune Artificial Immune Modulation (AIM) nanoparticle platform can be used to direct T cell responses by mimicking the dendritic cell function. In one application, AIM nanoparticles are used ex vivo to enrich and expand (E+E) rare populations of multi-antigen-specific CD8⁺ T cells for use of these cells as an AIM adoptive cell therapy. This study has demonstrated using E+E CD8⁺ T cells, the functional relevance of targeting EBV, HTLV-1, and HPV. Expanded T cells consist primarily of effector memory, central memory, and self-renewing stem-like memory T cells directed at selected viral antigen peptides presented by the AIM nanoparticle. T cells expanded against either EBV- or HPV-antigens were highly polyfunctional and displayed substantial in vitro cytotoxic activity against cell lines expressing the respective antigens. Our initial work was in the context of exploring T cells expanded from healthy donors and restricted to human leukocyte antigen (HLA)-A*02:01 serotype. AIM Adoptive Cell Therapies (ACT) are also being developed for other HLA class I serotypes. AIM adoptive cell therapies of autologous or allogeneic T cells specific to antigens associated with acute myeloid leukemia and multiple myeloma are currently in the clinic. The utility and flexibility of the AIM nanoparticle platform will be expanded as we advance the second application, an AIM injectable off-the-shelf nanoparticle, which targets multiple antigen-specific T cell populations to either activate, tolerize, or destroy these targeted CD8⁺ T cells directly in vivo, leaving non-target cells alone. The AIM injectable platform offers the potential to develop new multi-antigen specific therapies for treating infectious diseases, cancer, and autoimmune diseases.

Rapid Expansion of Highly Functional Antigen-Specific T Cells from Patients with Melanoma by Nanoscale Artificial Antigen-Presenting Cells

PURPOSE

Generation of antigen-specific T cells from patients with cancer employs large numbers of peripheral blood cells and/or tumor-infiltrating cells to generate antigen-presenting and effector cells commonly requiring multiple rounds of restimulation ex vivo. We used a novel paramagnetic, nanoparticle-based artificial antigen-presenting cell (nano-aAPC) that combines anti-CD28 costimulatory and human MHC class I molecules that are loaded with antigenic peptides to rapidly expand tumor antigen-specific T cells from patients with melanoma.

EXPERIMENTAL DESIGN

Nano-aAPC-expressing HLA-A*0201 molecules and costimulatory anti-CD28 antibody and HLA-A*0201 molecules loaded with MART-1 or gp100 class I-restricted peptides were used to stimulate CD8 T cells purified from the peripheral blood of treatment-naïve or PD-1 antibody-treated patients with stage IV melanoma. Expanded cells were restimulated with fresh peptide-pulsed nano-aAPC at day 7. Phenotype analysis and functional assays including cytokine release, cytolysis, and measurement of avidity were conducted.

RESULTS

MART-1-specific CD8 T cells rapidly expanded up to 1,000-fold by day 14 after exposure to peptide-pulsed nano-aAPC. Expanded T cells had a predominantly stem cell memory CD45RA⁺/CD62L⁺/CD95⁺ phenotype; expressed ICOS, PD-1, Tim3, and LAG3; and lacked CD28. Cells from patients with melanoma were polyfunctional; highly avid; expressed IL2, IFNγ, and TNFα; and exhibited cytolytic activity against tumor cell lines. They expanded 2- to 3-fold after exposure to PD-1 antibody in vivo, and expressed a highly diverse T-cell receptor V beta repertoire.

CONCLUSIONS

Peptide-pulsed nano-aAPC rapidly expanded polyfunctional antigen-specific CD8 T cells with high avidity, potent lytic function, and a stem cell memory phenotype from patients with melanoma.

Live-attenuated bivalent measles virus-derived vaccines targeting Middle East respiratory syndrome coronavirus induce robust and multifunctional T cell responses against both viruses in an appropriate mouse model

Cases of Middle East respiratory syndrome coronavirus (MERS-CoV) continue to occur, making it one of the WHO´s targets for accelerated vaccine development. One vaccine candidate is based on live-attenuated measles virus (MV) vaccine encoding the MERS-CoV spike glycoprotein (MERS-S). MV_vac2-MERS-S(H) induces robust humoral and cellular immunity against MERS-S mediating protection. Here, the induction and nature of immunity after vaccination with MV_vac2-MERS-S(H) or novel MV_vac2-MERS-N were further characterized. We focused on the necessity for vector replication and the nature of induced T cells, since functional CD8⁺ T cells contribute importantly to clearance of MERS-CoV. While no immunity against MERS-CoV or MV was detected in MV-susceptible mice after immunization with UV-inactivated virus, replication-competent MV_vac2-MERS-S(H) triggered robust neutralizing antibody titers also in adult mice. Furthermore, a significant fraction of MERS CoV-specific CD8⁺ T cells and MV-specific CD4⁺ T cells simultaneously expressing IFN-γ and TNF-α were induced, revealing that MV_vac2-MERS-S(H) induces multifunctional cellular immunity.

Long-lasting multifunctional CD8+ T cell responses in end-stage melanoma patients can be induced by dendritic cell vaccination

Cytotoxic T cells are considered crucial for antitumor immunity and their induction is the aim of various immunotherapeutic strategies. High frequencies of tumor-specific CD8⁺ T cells alone, however, are no guarantee for long-term tumor control. Here, we analyzed the functionality of tumor-specific CD8⁺ T cells in melanoma patients upon dendritic cell vaccination by measuring multiple T cell effector functions considered crucial for anticancer immunity, including the expression of pro-inflammatory cytokines, chemokines and cytotoxic markers (IFNγ, TNFα, IL-2, CCL4, CD107a). We identified small numbers of multifunctional (polyfunctional) tumor-specific CD8⁺ T cells in several patients and dendritic cell therapy was able to improve the functionality of these pre-existing tumor-specific CD8⁺ T cells. Generated multifunctional CD8⁺ T cell responses could persist for up to ten years and within the same patient functionality could vary greatly for the different vaccination antigens. Importantly, after one cycle of DC vaccination highly functional CD8⁺ T cells were only detected in patients displaying prolonged overall survival. Our results shed light on the dynamics of multifunctional tumor-specific CD8⁺ T cells during metastatic melanoma and reveal a new feature of dendritic cell vaccination in vivo.

Linking form to function: Biophysical aspects of artificial antigen presenting cell design

Artificial antigen presenting cells (aAPCs) are engineered platforms for T cell activation and expansion, synthesized by coupling T cell activating proteins to the surface of cell lines or biocompatible particles. They can serve both as model systems to study the basic aspects of T cell signaling and translationally as novel approaches for either active or adoptive immunotherapy. Historically, these reductionist systems have not been designed to mimic the temporally and spatially complex interactions observed during endogenous T cell-APC contact, which include receptor organization at both micro- and nanoscales and dynamic changes in cell and membrane morphologies. Here, we review how particle size and shape, as well as heterogenous distribution of T cell activating proteins on the particle surface, are critical aspects of aAPC design. In doing so, we demonstrate how insights derived from endogenous T cell activation can be applied to optimize aAPC, and in turn how aAPC platforms can be used to better understand endogenous T cell stimulation. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.

Diversified phenotype of antigen specific CD8+ T cells responding to the immunodominant epitopes of IE and pp65 antigens of human cytomegalovirus

To study the cytomegalovirus (CMV)-specific CD8+ T cells in individuals with HLA A*1101, A*0201 and A*2402, our findings showed that peptide SK-10-2, KI-10 and KV-10 of CMV IE and pp65 antigens were immunodominant in 198 individuals with HLA A*1101, A*0201 and A*2402, the most frequent genotypes in Chinese. Interestingly, SK-10-2 induced the strongest T cell response to produce IFN-γ whereas the others did not induce prominent IFN-γ production despite they all induced remarkable T cell proliferation. The peptides induced different phenotypes including IFN-γ(high)TNF-α(low) and TNF-α(low)Foxp3(low). It suggests that only some of CMV-reactive CD8+ T cells are real protective IFN-γ(high) cytotoxic T cells.

CD47 Enhances In Vivo Functionality of Artificial Antigen-Presenting Cells

PURPOSE

Artificial antigen-presenting cells, aAPC, have successfully been used to stimulate antigen-specific T-cell responses in vitro as well as in vivo. Although aAPC compare favorably with autologous dendritic cells in vitro, their effect in vivo might be diminished through rapid clearance by macrophages. Therefore, to prevent uptake and minimize clearance of aAPC by macrophages, thereby increasing in vivo functionality, we investigated the efficiency of "don't eat me" three-signal aAPC compared with classical two-signal aAPC.

EXPERIMENTAL DESIGN

To generate "don't eat me" aAPC, CD47 was additionally immobilized onto classical aAPC (aAPC(CD47+)). aAPC and aAPC(CD47+) were analyzed in in vitro human primary T-cell and macrophage cocultures. In vivo efficiency was compared in a NOD/SCID T-cell proliferation and a B16-SIY melanoma model.

RESULTS

This study demonstrates that aAPC(CD47+) in coculture with human macrophages show a CD47 concentration-dependent inhibition of phagocytosis, whereas their ability to generate and expand antigen-specific T cells was not affected. Furthermore, aAPC(CD47+)-generated T cells displayed equivalent killing abilities and polyfunctionality when compared with aAPC-generated T cells. In addition, in vivo studies demonstrated an enhanced stimulatory capacity and tumor inhibition of aAPC(CD47+) over normal aAPC in conjunction with diverging biodistribution in different organs.

CONCLUSIONS

Our data for the first time show that aAPC functionalized with CD47 maintain their stimulatory capacity in vitro and demonstrate enhanced in vivo efficiency. Thus, these next-generation aAPC(CD47+) have a unique potential to enhance the application of the aAPC technology for future immunotherapy approaches.

Sprouty-2 regulates HIV-specific T cell polyfunctionality

The ability of individual T cells to perform multiple effector functions is crucial for protective immunity against viruses and cancer. This polyfunctionality is frequently lost during chronic infections; however, the molecular mechanisms driving T cell polyfunctionality are poorly understood. We found that human T cells stimulated by a high concentration of antigen lacked polyfunctionality and expressed a transcription profile similar to that of exhausted T cells. One specific pathway implicated by the transcription profile in control of T cell polyfunctionality was the MAPK/ERK pathway. This pathway was altered in response to different antigen concentrations, and polyfunctionality correlated with upregulation of phosphorylated ERK. T cells that were stimulated with a high concentration of antigen upregulated sprouty-2 (SPRY2), a negative regulator of the MAPK/ERK pathway. The clinical relevance of SPRY2 was confirmed by examining SPRY2 expression in HIV-specific T cells, where high levels of SPRY2 were seen in HIV-specific T cells and inhibition of SPRY2 expression enhanced the HIV-specific polyfunctional response independently of the PD-1 pathway. Our findings indicate that increased SPRY2 expression during chronic viral infection reduces T cell polyfunctionality and identify SPRY2 as a potential target for immunotherapy.

Particle shape dependence of CD8+ T cell activation by artificial antigen presenting cells

Previous work developing particle-based acellular, artificial antigen presenting cells (aAPCs) has focused exclusively on spherical platforms. To explore the role of shape, we generated ellipsoidal PLGA microparticles with varying aspect ratios (ARs) and synthesized aAPCs from them. The ellipsoidal biomimetic aAPCs with high-AR showed significantly enhanced in vitro and in vivo activity above spherical aAPCs with particle volume and antigen content held constant. Confocal imaging indicates that CD8+ T cells preferentially migrate to and are activated by interaction with the long axis of the aAPC. Importantly, enhanced activity of high-AR aAPCs was seen in a mouse melanoma model, with high-AR aAPCs improving melanoma survival compared to non-cognate aAPCs (p = 0.004) and cognate spherical aAPCs (p = 0.05). These findings indicate that particle geometry is a critical design criterion in the generation of aAPCs, and may offer insight into the essential role of geometry in the interaction between CD8+ T cells and biological APCs.

Nanoengineering approaches to the design of artificial antigen-presenting cells

Artificial antigen-presenting cells (aAPCs) have shown great initial promise for ex vivo activation of cytotoxic T cells. The development of aAPCs has focused mainly on the choice of proteins to use for surface presentation to T cells when conjugated to various spherical, microscale particles. We review here biomimetic nanoengineering approaches that have been applied to the development of aAPCs that move beyond initial concepts about aAPC development. This article also discusses key technologies that may be enabling for the development of nano- and micro-scale aAPCs with nanoscale features, and suggests several future directions for the field.

Biomimetic delivery with micro- and nanoparticles

The nascent field of biomimetic delivery with micro- and nanoparticles (MNP) has advanced considerably in recent years. Drawing inspiration from the ways that cells communicate in the body, several different modes of "delivery" (i.e., temporospatial presentation of biological signals) have been investigated in a number of therapeutic contexts. In particular, this review focuses on (1) controlled release formulations that deliver natural soluble factors with physiologically relevant temporal context, (2) presentation of surface-bound ligands to cells, with spatial organization of ligands ranging from isotropic to dynamically anisotropic, and (3) physical properties of particles, including size, shape and mechanical stiffness, which mimic those of natural cells. Importantly, the context provided by multimodal, or multifactor delivery represents a key element of most biomimetic MNP systems, a concept illustrated by an analogy to human interpersonal communication. Regulatory implications of increasingly sophisticated and "cell-like" biomimetic MNP systems are also discussed.

Polyfunctional T cells accumulate in large human cytomegalovirus-specific T cell responses

Large cytomegalovirus (CMV)-specific CD8 T-cell responses are observed in both young and, somewhat more often, old people. Frequent CMV reactivation is thought to exhaust these cells and render them dysfunctional so that larger numbers of them are needed to control CMV. Expansions of CMV-specific CD4 T cells are also seen but are less well studied. In this study, we examined the T-cell response to the dominant CMV pp65 and IE-1 antigens in healthy CMV-infected people across a wide age range (20 to 84 years) by using multicolor flow cytometry. CMV-specific T cells were characterized by the activation markers CD40 ligand (CD40L), interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) and the memory markers CD27 and CD45RA. The proportions of effector memory T cells increased in large responses, as did the proportions of polyfunctional CD8 (IFN-γ(+) IL-2(+/-) TNF-α(+)) and CD4 (CD40L(+/-) IFN-γ(+) IL-2(+) TNF-α(+)) T-cell subsets, while the proportion of naïve T cells decreased. The bigger the CD4 or CD8 T-cell response to pp65, the larger was the proportion of T cells with an advanced memory phenotype in the entire (including non-CMV-specific) T-cell compartment. In addition, the number of activation markers per cell correlated with the degree of T-cell receptor downregulation, suggesting increased antigen sensitivity in polyfunctional cells. In summary, our findings show that polyfunctional CMV-specific T cells were not superseded by dysfunctional cells, even in very large responses. At the same time, however, the memory subset composition of the entire T-cell compartment correlated with the size of the T-cell response to CMV pp65, confirming a strong effect of CMV infection on the immune systems of some, but not all, infected people.

A high-throughput single-cell analysis of human CD8⁺ T cell functions reveals discordance for cytokine secretion and cytolysis

CD8+ T cells are a key component of the adaptive immune response to viral infection. An inadequate CD8+ T cell response is thought to be partly responsible for the persistent chronic infection that arises following infection with HIV. It is therefore critical to identify ways to define what constitutes an adequate or inadequate response. IFN-γ production has been used as a measure of T cell function, but the relationship between cytokine production and the ability of a cell to lyse virus-infected cells is not clear. Moreover, the ability to assess multiple CD8+ T cell functions with single-cell resolution using freshly isolated blood samples, and subsequently to recover these cells for further functional analyses, has not been achieved. As described here, to address this need, we have developed a high-throughput, automated assay in 125-pl microwells to simultaneously evaluate the ability of thousands of individual CD8+ T cells from HIV-infected patients to mediate lysis and to produce cytokines. This concurrent, direct analysis enabled us to investigate the correlation between immediate cytotoxic activity and short-term cytokine secretion. The majority of in vivo primed, circulating HIV-specific CD8+ T cells were discordant for cytolysis and cytokine secretion, notably IFN-γ, when encountering cognate antigen presented on defined numbers of cells. Our approach should facilitate determination of signatures of functional variance among individual effector CD8+ T cells, including those from mucosal samples and those induced by vaccines.

Identification and visualization of CD8+ T cell mediated IFN-γ signaling in target cells during an antiviral immune response in the brain

CD8(+) T cells infiltrate the brain during an anti-viral immune response. Within the brain CD8(+) T cells recognize cells expressing target antigens, become activated, and secrete IFNγ. However, there are no methods to recognize individual cells that respond to IFNγ. Using a model that studies the effects of the systemic anti-adenoviral immune response upon brain cells infected with an adenoviral vector in mice, we describe a method that identifies individual cells that respond to IFNγ. To identify individual mouse brain cells that respond to IFNγ we constructed a series of adenoviral vectors that contain a transcriptional response element that is selectively activated by IFNγ signaling, the gamma-activated site (GAS) promoter element; the GAS element drives expression of a transgene, Cre recombinase (Ad-GAS-Cre). Upon binding of IFNγ to its receptor, the intracellular signaling cascade activates the GAS promoter, which drives expression of the transgene Cre recombinase. We demonstrate that upon activation of a systemic immune response against adenovirus, CD8(+) T cells infiltrate the brain, interact with target cells, and cause an increase in the number of cells expressing Cre recombinase. This method can be used to identify, study, and eventually determine the long term fate of infected brain cells that are specifically targeted by IFNγ. The significance of this method is that it will allow to characterize the networks in the brain that respond to the specific secretion of IFNγ by anti-viral CD8(+) T cells that infiltrate the brain. This will allow novel insights into the cellular and molecular responses underlying brain immune responses.

CD8+ T cell immunity to 2009 pandemic and seasonal H1N1 influenza viruses

A novel strain of H1N1 influenza A virus (pH1N1) emerged in 2009, causing a worldwide pandemic. Several studies suggest that this virus is antigenically more closely related to human influenza viruses that circulated prior to 1957 than viruses of more recent seasonal influenza varieties. The extent to which individuals who are naïve to the 2009 pH1N1 virus carry cross-reactive CD8+ T cells is not known, but a certain degree of reactivity would be expected since there is substantial conservation among the internal proteins of the virus. In the present study, we examined the production of multiple cytokines in response to virus from CD8+ T cells in healthy adult subjects, between 18 and 50 years of age (born post 1957), who had no evidence of exposure to the 2009 pH1N1 virus, and had blood collected prior to the emergence of the pandemic in April of 2009. Human peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with a panel of live viruses, and assayed by intracellular cytokine staining and flow cytometry. Although results were variable, most subjects exhibited cytokine positive CD8+ T cells in response to pH1N1. Cytokine producing cells were predominantly single positive (IL2, IFNγ, or TNFα); triple-cytokine producing cells were relatively rare. This result suggests that although many adults carry cross-reactive T cells against the emergent pandemic virus, these cells are in a functionally limited state, possibly because these subjects have not had recent exposure to either seasonal or pandemic influenza strains.

Human leukocyte antigens A*3001 and A*3002 show distinct peptide-binding patterns of the Mycobacterium tuberculosis protein TB10.4: consequences for immune recognition

High-tuberculosis (TB)-burden countries are located in sub-Saharan Africa. We examined the frequency of human leukocyte antigen (HLA) alleles, followed by recombinant expression of the most frequent HLA-A alleles, i.e., HLA-A*3001 and HLA-A*3002, to study differences in mycobacterial peptide presentation and CD8(+) T-cell recognition. We screened a peptide library (9-mer peptides with an 8-amino-acid overlap) for binding, affinity, and off-rate of the Mycobacterium tuberculosis-associated antigen TB10.4 and identified only three TB10.4 peptides with considerable binding to HLA-A*3001. In contrast, 22 peptides bound to HLA-A*3002. This reflects a marked difference in the binding preference between the two alleles, with A*3002 tolerating a more promiscuous peptide-binding pattern and A*3001 accommodating only a very selective peptide repertoire. Subsequent analysis of the affinity and off-rate of the binding peptides revealed a strong affinity (8 nM to 7 μM) and moderate off-rate (20 min to 3 h) for both alleles. Construction of HLA-A*3001 and HLA-A*3002 tetramers containing selected binding peptides from TB10.4, including a peptide which was shared among both alleles, QIMYNYPAM (TB10.4(3-11)), allowed us to enumerate epitope-specific T cells in HLA-A*3001- and HLA-A*3002-typed patients with active TB. HLA-A*3001 and HLA-A*3002 major histocompatibility complex-peptide complexes were recognized in individuals with active TB, irrespective of their homozygous HLA-A*3001 or HLA-A*3002 genetic background. The antigen-specific T cells exhibited the CD45RA(+) CCR7(+) precursor phenotype and the interleukin-7 receptor (CD127), which were different from the phenotype and receptor exhibited by the parental CD8(+) T-cell population.

Artificial antigen-presenting cells for use in adoptive immunotherapy

The observation that T cells can recognize and specifically eliminate cancer cells has spurred interest in the development of efficient methods to generate large numbers of T cells with specificity for tumor antigens that can be harnessed for use in cancer therapy. Recent studies have demonstrated that during encounter with tumor antigen, the signals delivered to T cells by professional antigen-presenting cells can affect T-cell programming and their subsequent therapeutic efficacy. This has stimulated efforts to develop artificial antigen-presenting cells that allow optimal control over the signals provided to T cells. In this review, we will discuss the advantages and disadvantages of cellular and acellular artificial antigen-presenting cell systems and their use in T-cell adoptive immunotherapy for cancer.

Novel cellular microarray assay for profiling T-cell peptide antigen specificities

We present a novel cellular microarray assay using soluble peptide-loaded HLA A2-Ig dimer complexes that optimizes the avidity of peptide-HLA binding by preserving the molecular flexibility of the dimer complex while attaining much higher concentrations of the complex relative to cognate T-cell receptors. A seminal advance in assay development is made by separating the molecular T-cell receptor recognition event from the binding interactions that lead to antigen-specific cell capture on the microarray. This advance enables the quantitative determination of antigen-specific frequencies in heterogeneous T-cell populations without enumerating the number of cells captured on the microarray. The specificity of cell capture, sensitivity to low antigen-specific frequencies, and quantitation of antigenic T-cell specificities are established using CD8 T-cell populations with prepared antigen-specific CTL frequencies and heterogeneous T cells isolated from peripheral blood. The results demonstrate several advantages for high-throughput broad-based, quantitative assessments of low-frequency antigen specificities. The assay enables the use of cellular microarrays to determine the stability and flux of antigen-specific T-cell responses within and across populations.

T-cell receptor signals direct the composition and function of the memory CD8+ T-cell pool

SH2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) nucleates a signaling complex critical for T-cell receptor (TCR) signal propagation. Mutations in the tyrosines of SLP-76 result in graded defects in TCR-induced signals depending on the tyrosine(s) affected. Here we use 2 strains of genomic knock-in mice expressing tyrosine to phenylalanine mutations to examine the role of TCR signals in the differentiation of effector and memory CD8(+) T cells in response to infection in vivo. Our data support a model in which altered TCR signals can determine the rate of memory versus effector cell differentiation independent of initial T-cell expansion. Furthermore, we show that TCR signals sufficient to promote CD8(+) T-cell differentiation are different from those required to elicit inflammatory cytokine production.

GM-CSF increases mucosal and systemic immunogenicity of an H1N1 influenza DNA vaccine administered into the epidermis of non-human primates

Background

The recent H5N1 avian and H1N1 swine-origin influenza virus outbreaks reaffirm that the threat of a world-wide influenza pandemic is both real and ever-present. Vaccination is still considered the best strategy for protection against influenza virus infection but a significant challenge is to identify new vaccine approaches that offer accelerated production, broader protection against drifted and shifted strains, and the capacity to elicit anti-viral immune responses in the respiratory tract at the site of viral entry. As a safe alternative to live attenuated vaccines, the mucosal and systemic immunogenicity of an H1N1 influenza (A/New Caledonia/20/99) HA DNA vaccine administered by particle-mediated epidermal delivery (PMED or gene gun) was analyzed in rhesus macaques.

Methodology/Principal Findings

Macaques were immunized at weeks 0, 8, and 16 using a disposable single-shot particle-mediated delivery device designed for clinical use that delivers plasmid DNA directly into cells of the epidermis. Significant levels of hemagglutination inhibiting (HI) antibodies and cytokine-secreting HA-specific T cells were observed in the periphery of macaques following 1–3 doses of the PMED HA DNA vaccine. In addition, HA DNA vaccination induced detectable levels of HA-specific mucosal antibodies and T cells in the lung and gut-associated lymphoid tissues of vaccinated macaques. Importantly, co-delivery of a DNA encoding the rhesus macaque GM-CSF gene was found to significantly enhance both the systemic and mucosal immunogenicity of the HA DNA vaccine.

Conclusions/Significance

These results provide strong support for the development of a particle-mediated epidermal DNA vaccine for protection against respiratory pathogens such as influenza and demonstrate, for the first time, the ability of skin-delivered GM-CSF to serve as an effective mucosal adjuvant for vaccine induction of immune responses in the gut and respiratory tract.