A novel HIV vaccine adjuvanted by IC31 induces robust and persistent humoral and cellular immunity.

The HIV vaccine strategy that, to date, generated immune protection consisted of a prime-boost regimen using a canarypox vector and an HIV envelope protein with alum, as shown in the RV144 trial. Since the efficacy was weak, and previous HIV vaccine trials designed to generate antibody responses failed, we hypothesized that generation of T cell responses would result in improved protection. Thus, we tested the immunogenicity of a similar envelope-based vaccine using a mouse model, with two modifications: a clade C CN54gp140 HIV envelope protein was adjuvanted by the TLR9 agonist IC31®, and the viral vector was the vaccinia strain NYVAC-CN54 expressing HIV envelope gp120. The use of IC31® facilitated immunoglobulin isotype switching, leading to the production of Env-specific IgG2a, as compared to protein with alum alone. Boosting with NYVAC-CN54 resulted in the generation of more robust Th1 T cell responses. Moreover, gp140 prime with IC31® and alum followed by NYVAC-CN54 boost resulted in the formation and persistence of central and effector memory populations in the spleen and an effector memory population in the gut. Our data suggest that this regimen is promising and could improve the protection rate by eliciting strong and long-lasting humoral and cellular immune responses.

An essential role for transmembrane TNF in the resolution of the inflammatory lesion induced by Leishmania major infection.

TNF is an essential player in infections with Leishmania major, contributing to the control of the inflammatory lesion and, to a lesser degree, to parasite killing. However, the relative contribution of the soluble and transmembrane forms of TNF in these processes is unknown. To investigate the role of transmembrane TNF (mTNF) in the control of L. major infections, mTNF-knock-in (mTNF(Delta/Delta)) mice, which express functional mTNF but do not release soluble TNF, were infected with L. major, and the development of the inflammatory lesion and the immune response was compared to that occurring in L. major-infected TNF(-/-) and wild-type mice. mTNF(Delta/Delta) mice controlled the infection and resolved their inflammatory lesion as well as wild-type mice, a process associated with the early clearance of neutrophils at the site of parasite infection. In contrast, L. major-infected TNF(-/-) mice developed non-healing lesions, characterized by an elevated presence of neutrophils at the site of infection and partial control of parasite number within the lesions. Altogether, the results presented here demonstrate that mTNF, in absence of soluble TNF, is sufficient to control infection due to L. major, enabling the regulation of inflammation, and the optimal killing of Leishmania parasites at the site of infection.

Enrichment of human CD4+ V(alpha)24/Vbeta11 invariant NKT cells in intrahepatic malignant tumors.

Invariant NKT cells (iNKT cells) recognize glycolipid Ags via an invariant TCR alpha-chain and play a central role in various immune responses. Although human CD4(+) and CD4(-) iNKT cell subsets both produce Th1 cytokines, the CD4(+) subset displays an enhanced ability to secrete Th2 cytokines and shows regulatory activity. We performed an ex vivo analysis of blood, liver, and tumor iNKT cells from patients with hepatocellular carcinoma and metastases from uveal melanoma or colon carcinoma. Frequencies of Valpha24/Vbeta11 iNKT cells were increased in tumors, especially in patients with hepatocellular carcinoma. The proportions of CD4(+), double negative, and CD8alpha(+) iNKT cell subsets in the blood of patients were similar to those of healthy donors. However, we consistently found that the proportion of CD4(+) iNKT cells increased gradually from blood to liver to tumor. Furthermore, CD4(+) iNKT cell clones generated from healthy donors were functionally distinct from their CD4(-) counterparts, exhibiting higher Th2 cytokine production and lower cytolytic activity. Thus, in the tumor microenvironment the iNKT cell repertoire is modified by the enrichment of CD4(+) iNKT cells, a subset able to generate Th2 cytokines that can inhibit the expansion of tumor Ag-specific CD8(+) T cells. Because CD4(+) iNKT cells appear inefficient in tumor defense and may even favor tumor growth and recurrence, novel iNKT-targeted therapies should restore CD4(-) iNKT cells at the tumor site and specifically induce Th1 cytokine production from all iNKT cell subsets.

Lack of Mycobacterium tuberculosis-specific interleukin-17A-producing CD4(+) T cells in active disease.

Protective immunity to Mycobacterium tuberculosis (Mtb) is commonly ascribed to a Th1 profile; however, the involvement of Th17 cells remains to be clarified. Here, we characterized Mtb-specific CD4(+) T cells in blood and bronchoalveolar lavages (BALs) from untreated subjects with either active tuberculosis disease (TB) or latent Mtb infection (LTBI), considered as prototypic models of uncontrolled or controlled infection, respectively. The production of IL-17A, IFN-γ, TNF-α, and IL-2 by Mtb-specific CD4(+) T cells was assessed both directly ex vivo and following in vitro antigen-specific T-cell expansion. Unlike for extracellular bacteria, Mtb-specific CD4(+) T-cell responses lacked immediate ex vivo IL-17A effector function in both LTBI and TB individuals. Furthermore, Mtb-specific Th17 cells were absent in BALs, while extracellular bacteria-specific Th17 cells were identified in gut biopsies of healthy individuals. Interestingly, only Mtb-specific CD4(+) T cells from 50% of LTBI but not from TB subjects acquired the ability to produce IL-17A following Mtb-specific T-cell expansion. Finally, IL-17A acquisition by Mtb-specific CD4(+) T cells correlated with the coexpression of CXCR3 and CCR6, currently associated to Th1 or Th17 profiles, respectively. Our data demonstrate that Mtb-specific Th17 cells are selectively undetectable in peripheral blood and BALs from TB patients.

The early IL-4 response to Leishmania major responsible for progressive disease in BALB/c mice is subject to the control of autocrine IL-2 production and regulatory CD4+C25+ T cells

Résumé : La majorité des souches de souris de laboratoire sont résistantes à l'infection par le parasite Leishmania major (L. major). A l'opposé, les souris de la souche BALB développent une maladie évolutive. La résistance et la sensibilité sont corrélées avec l'apparition de lymphocytes T CD4+ spécifiques du parasite, Th1 (de l'anglais T helper) ou Th2 respectivement. La réponse aberrante Th2 chez les souris de la souche BALB/c dépend, au moins en partie, de façon critique de la production rapide d'IL-4 suite à l'infection. Ce pic précoce d'IL-4 est produit par une population de lymphocytes T CD4+ restreinte aux molécules du MHC de classe II, exprimant les chaînes du récepteur des cellules T Vß4-Va8. Ces lymphocytes sont spécifiques d'un épitope de l'homologue Leishmania de la molécule RACK1 des mammifères, appelée LACK. Il a été clairement démontré que l'IL-4 rapidement produite par ces cellules T CD4+ Vß4-Va8 induit la maturation Th2 responsable de la sensibilité vis-à-vis de L. major. Des expériences ont été entreprises pour étudier la régulation de cette réponse précoce d'IL-4. Dans ce travail, nous avons documenté, dans les cellules provenant des ganglions de souris sensibles infectées par L. major, une augmentation de la transcription de l'ARNm de l'IL-2 qui précède la réponse précoce d'IL-4. La neutralisation de l'IL-2 durant les premiers jours d'infection induit la maturation des cellules Thl et la résistance vis-à-vis de L. major. Ces effets de l'anticorps anti-IL-2 neutralisant sont liés à sa capacité d'interférer avec la transcription rapide d'IL-4 des cellules CD4+ réactives à l'antigène LACK. Une augmentation similaire d'IL-2 survient chez les souris résistantes C57BL/6 qui sont incapables de générer la réponse précoce d'IL-4. Cependant, la protéiné LACK induit une transcription précoce d'IL-2 uniquement chez les souris sensibles. Des expériences de reconstitution utilisant des souris C.B.-17 SCID et des cellules T CD4+ réactives à LACK provenant de souris BALB/c IL-2-~démontrent un mode d'action autocrine de l'IL-2 sur la régulation de la réponse précoce d'IL4. Par conséquent, chez les souris C57BL/6, l'absence du pic précoce d'ARNm de l'IL-4 important pour la progression de la maladie paraît liée à l'incapacité des cellules T CD4+ réactives à LACK de produire de l'IL-2. Un rôle dans le contrôle de la production précoce d'IL-4 par les cellules T régulatrices CD4+CD25+ a été investigué en déplétant in vivo cette population de cellules. La déplétion induit une élévation du pic précoce de l'ARNm de l'IL-4 dans les ganglions drainant de souris BALB/c, ainsi qu'une exacerbation du cours de la maladie avec des taux augmentés d'IL-4 dans les ganglions. La réponse rapide d'IL-2 vis-à-vis de L. major est aussi significativement augmentée chez les souris BALB/c déplétées en cellules CD4+CD25+. De plus, nous avons démontré que le transfert de 10puissance(7) cellules provenant de la rate de souris BALB/c déplétées en cellules T régulatrices CD4+CD25+ rend les souris SCID sensibles à l'infection et permet la différentiation Th2. Au contraire, les souris SCID reconstituées avec 10' cellules de la rate de souris BALB/c contrôle sont résistantes à infection par L. major et développent une réponse Thl. Chez les souris SCID reconstituées avec des cellules de rate déplétées en cellules exprimant le marqueur CD25, le traitement avec un anticorps neutralisant l'IL-4 au moment de l'infection par L. major prévient le développement de la réponse Th2 et rend ces souris résistantes à l'infection. Ces résultats démontrent que les cellules T régulatrices CD4+CD25+ jouent un rôle dans la régulation du pic précoce d'IL-4 responsable du développement cellulaire Th2 dans ce modèle d'infection. Summary Mice from most strains are resistant to infection with Leishmania major (L. major). In contrast, BALB mice develop progressive disease. Resistance and susceptibility result from parasite-specific CD4+ Thl or Th2 cells, respectively. The aberrant Th2 response in BALB/c mice depends, at least in part, upon the production of IL-4 early after infection. The CD4+ T cells responsible for this early IL-4 response to L. major express a restricted TCR repertoire (Vß4-Va8) and respond to an I-Ad-restricted epitope of the Leishmania homologue of mammalian RACK1, designated LACK. The role of these cells and the IL-4 they produce for subsequent Th2 cell development and disease progression in BALB/c mice was demonstrated. Experiments have been undertaken to study the regulation of the rapid IL-4 production to L. major. In this report, we document an IL-2 mRNA burst, preceding the reported early IL-4 response, in draining lymph nodes of susceptible mice infected with L. major. Neutralization of IL-2 during the first days of infection redirected Thl cell maturation and resistance to L. major, through interference with the rapid IL-4 transcription in LACKreactive CD4+ cells. A burst of IL-2 transcripts also occurred in infected C57BL/6 mice that do not mount an early IL-4 response. However, although the LACK protein induced IL-2 transcripts in susceptible mice, it failed to trigger this response in resistant C57BL/6 mice. Reconstitution experiments using C.B.-17 SCID mice and LACK-reactive CD4+ T cells from IL-2-/- BALB/c mice showed that triggering of the early IL-4 response required autocrine IL2. Thus, in C57BL/6 mice, the inability of LACK-reactive CD4+ T cells to express early IL-4 mRNA transcription, important for disease progression, appears due to an incapacity of these cells to produce IL-2. A role for CD4+CD25+ regulatory T cells in the control of this early IL-4 production was investigated by depleting in vivo this regulatory T cell population. Depletion induced an increase in the early burst of IL-4 mRNA in the draining lymph nodes of BALB/c mice, and exacerbated the course of disease with higher levels of IL-4 mRNA and protein in their lymph nodes. The rapid IL-2 response to L. major is also significantly enhanced in BALB/c mice depleted of CD4+CD25+ cells. We further showed that transfer of 10~ BALB/c spleen cells that were depleted of CD4+CD25+ regulatory T cells rendered SCID mice susceptible to infection and allowed Th2 differentiation while SCID mice reconstituted with 10 control BALB/c spleen cells were resistant to infection with L. major and developed a Thl response. Treatment with a mAb against IL-4 upon infection with L. major in SCID mice reconstituted with CD25-depleted spleen cells prevented the development of Th2 polarization and rendered them resistant to infection. These results demonstrate that CD4+CD25+ regulatory T cells play a role in regulating the early IL-4 mRNA and the subsequent development of a Th2 response in this model of infection.

CD1d-antibody fusion proteins target iNKT cells to the tumor and trigger long-term therapeutic responses.

Despite the well-established antitumor activity of CD1d-restricted invariant natural killer T lymphocytes (iNKT), their use for cancer therapy has remained challenging. This appears to be due to their strong but short-lived activation followed by long-term anergy after a single administration of the CD1d agonist ligand alpha-galactosylceramide (αGC). As a promising alternative, we obtained sustained mouse iNKT cell responses associated with prolonged antitumor effects through repeated administrations of tumor-targeted recombinant sCD1d-antitumor scFv fusion proteins loaded with αGC. Here, we demonstrate that CD1d fusion proteins bound to tumor cells via the antibody fragment specific for a tumor-associated antigen, efficiently activate human iNKT cell lines leading to potent tumor cell lysis. The importance of CD1d tumor targeting was confirmed in tumor-bearing mice in which only the specific tumor-targeted CD1d fusion protein resulted in tumor inhibition of well-established aggressive tumor grafts. The therapeutic efficacy correlated with the repeated activation of iNKT and natural killer cells marked by their release of TH1 cytokines, despite the up-regulation of the co-inhibitory receptor PD-1. Our results demonstrate the superiority of providing the superagonist αGC loaded on recombinant CD1d proteins and support the use of αGC/sCD1d-antitumor fusion proteins to secure a sustained human and mouse iNKT cell activation, while targeting their cytotoxic activity and cytokine release to the tumor site.

Expansion of gamma delta+ T cells in BALB/c mice infected with Leishmania major is dependent upon Th2-type CD4+ T cells.

T cells belong to either the alpha beta+ or gamma delta+ lineage as defined by their antigen receptor. Although both T-cell subsets have been shown to be involved in the immune response to the parasite Leishmania major, very little is known about possible interactions between these two populations. In this study, using a mouse model of infection with L. major, we showed that expansion of a subset of gamma delta+ T cells in vivo is dependent upon the presence of alpha beta+ CD4+ T cells. Moreover, this effect appears to be mediated via the secretion of lymphokines by CD4+ cells with a T-helper 2 (Th2) functional phenotype. Results showing that activation of Th2-type cells in mice treated with anti-immunoglobulin D antibodies or infected with Nippostrongylus brasiliensis also results in gamma delta+ T-cell expansion suggest that this effect of the Th2-type CD4+ cells is a general phenomenon not restricted to infection with L. major.

Cytokines in parasitic diseases: the example of cutaneous leishmaniasis.

The essential role of cytokines in parasitic diseases has been emphasised since the in vivo description of the importance of T helper 1 (Th1) and T helper 2 (Th2) CD4+ T cell responses in resistance and susceptibility to infection with L. major in mice. Th1 cells produced IL-2, IFN-gamma and Lymphotoxin T (LT) and Th2 cells produce IL-4, IL-5 and IL-13. In this model of infection the correlation between on the one hand resistance to infection and the development of a Th1 response and on the other hand susceptibility and Th2 cell development allowed the identification of the mechanisms directing the differentiation of CD4+ T cell precursors towards either Th1 type or Th2 type responses. Cytokines are the crucial inducer of functional CD4+ T cell subset differentiation during infection with L. major. IL-12 and IFN-gamma direct the differentiation of Th1 response and IL-4 of a Th2 response. In susceptible mice, careful analysis of IL-4 production during the first days of infection has shown that the IL-4 produced as a result of a very early burst of IL-4 mRNA expression (16 hours) plays a essential role in the maturation of a Th2 CD4+ T cell response by rendering the CD4+ T cell precursors unresponsive to IL-12. Activation of a restricted population of CD4+ T cells expressing the V beta 4 V alpha 8 TCR heterodimer after recognition of a single antigen, the LACK (Leishmania Activated c Kinase) antigen, resulted in this rapid production of IL-4 required for the subsequent CD4+ T cell differentiation. Thus, tolerization of these cells might contribute a strategy for preventing infection with L. major.

Functional plasticity of the LACK-reactive Vbeta4-Valpha8 CD4(+) T cells normally producing the early IL-4 instructing Th2 cell development and susceptibility to Leishmania major in BALB / c mice.

Early production of IL-4 by LACK-reactive Vbeta4-Valpha8 CD4(+) T cells instructs aberrant Th2 cell development and susceptibility to Leishmania major in BALB / c mice. This was demonstrated using Vbeta4(+)-deficient BALB / c mice as a result of chronic infection with MMTV (SIM), a mouse mammary tumor virus expressing a Vbeta4-specific superantigen. The early IL-4 response was absent in these mice which develop a Th1 response to L. major. Here, we studied the functional plasticity of LACK-reactive Vbeta4-Valpha8 CD4(+) T cells using BALB/ c mice inoculated with L. major shortly after infection with MMTV (SIM), i. e. before deletion of Vbeta4(+) cells. These mice fail to produce the early IL-4 response to L. major and instead exhibit an IFN-gamma response that occurs within LACK-reactive Vbeta4-Valpha8 CD4(+) T cells. Neutralization of IFN-gamma restores the production of IL-4 by these cells. These data suggest that the functional properties of LACK-reactive Vbeta4-Valpha8 CD4(+) T cells are not irreversibly fixed.

Role of Toll-Like Receptor 9 Signaling in Experimental Leishmania braziliensis Infection.

Infection with Leishmania braziliensis causes cutaneous or mucocutaneous leismaniasis in humans. Toll-like receptor 9 (TLR9) expression has been found in granulomas of lesions in L. braziliensis-infected individuals. L. braziliensis inoculation in mice induces very small lesions that are self-healing, whereas deficiency in the TLR adaptor molecule, MyD88, renders mice susceptible to infection. The TLR involved has not been identified, prompting us to investigate if TLR9 triggering by the parasite contributes to the strong resistance to infection observed in L. braziliensis-inoculated mice. The parasites activated wild-type (WT) dendritic cells (DCs) in vitro but not DCs derived from TLR9(-/-) mice. TLR9(-/-) mice inoculated with L. braziliensis exhibited a transient susceptibility characterized by increased lesion size and parasite burden compared to those of WT mice. Surprisingly, elevated levels of gamma interferon (IFN-γ) were measured at the site of infection and in draining lymph node T cells of TLR9(-/-) mice at the peak of susceptibility, suggesting that unlike observations in vitro, the parasite could induce DC activation leading to the development of Th1 cells in the absence of TLR9 expression. Taken together, these data show that TLR9 signaling is important for the early control of lesion development and parasite burden but is dispensable for the differentiation of Th1 cells secreting IFN-γ, and the high levels of this cytokine are not sufficient to control early parasite replication following L. braziliensis infection.

Mice from a genetically resistant background lacking the interferon gamma receptor are susceptible to infection with Leishmania major but mount a polarized T helper cell 1-type CD4+ T cell response.

Mice with homologous disruption of the gene coding for the ligand-binding chain of the interferon (IFN) gamma receptor and derived from a strain genetically resistant to infection with Leishmania major have been used to study further the role of this cytokine in the differentiation of functional CD4+ T cell subsets in vivo and resistance to infection. Wild-type 129/Sv/Ev mice are resistant to infection with this parasite, developing only small lesions, which resolve spontaneously within 6 wk. In contrast, mice lacking the IFN-gamma receptor develop large, progressing lesions. After infection, lymph nodes (LN) and spleens from both wild-type and knockout mice showed an expansion of CD4+ cells producing IFN-gamma as revealed by measuring IFN-gamma in supernatants of specifically stimulated CD4+ T cells, by enumerating IFN-gamma-producing T cells, and by Northern blot analysis of IFN-gamma transcripts. No biologically active interleukin (IL) 4 was detected in supernatants of in vitro-stimulated LN or spleen cells from infected wild-type or deficient mice. Reverse transcription polymerase chain reaction analysis with primers specific for IL-4 showed similar IL-4 message levels in LN from both types of mice. The IL-4 message levels observed were comparable to those found in similarly infected C57BL/6 mice and significantly lower than the levels found in BALB/c mice. Anti-IFN-gamma treatment of both types of mice failed to alter the pattern of cytokines produced after infection. These data show that even in the absence of IFN-gamma receptors, T helper cell (Th) 1-type responses still develop in genetically resistant mice with no evidence for the expansion of Th2 cells.

Definition of key variables for the induction of optimal NY-ESO-1-specific T cells in HLA transgene mice.

An attractive treatment of cancer consists in inducing tumor-eradicating CD8(+) CTL specific for tumor-associated Ags, such as NY-ESO-1 (ESO), a strongly immunogenic cancer germ line gene-encoded tumor-associated Ag, widely expressed on diverse tumors. To establish optimal priming of ESO-specific CTL and to define critical vaccine variables and mechanisms, we used HLA-A2/DR1 H-2(-/-) transgenic mice and sequential immunization with immunodominant DR1- and A2-restricted ESO peptides. Immunization of mice first with the DR1-restricted ESO(123-137) peptide and subsequently with mature dendritic cells (DCs) presenting this and the A2-restriced ESO(157-165) epitope generated abundant, circulating, high-avidity primary and memory CD8(+) T cells that efficiently killed A2/ESO(157-165)(+) tumor cells. This prime boost regimen was superior to other vaccine regimes and required strong Th1 cell responses, copresentation of MHC class I and MHC class II peptides by the same DC, and resulted in upregulation of sphingosine 1-phosphate receptor 1, and thus egress of freshly primed CD8(+) T cells from the draining lymph nodes into circulation. This well-defined system allowed detailed mechanistic analysis, which revealed that 1) the Th1 cytokines IFN-gamma and IL-2 played key roles in CTL priming, namely by upregulating on naive CD8(+) T cells the chemokine receptor CCR5; 2) the inflammatory chemokines CCL4 (MIP-1beta) and CCL3 (MIP-1alpha) chemoattracted primed CD4(+) T cells to mature DCs and activated, naive CD8(+) T cells to DC-CD4 conjugates, respectively; and 3) blockade of these chemokines or their common receptor CCR5 ablated priming of CD8(+) T cells and upregulation of sphingosine 1-phosphate receptor 1. These findings provide new opportunities for improving T cell cancer vaccines.

Innate Immune Sensing of Fusarium culmorum by Mouse Dendritic Cells.

Chronic inhalation of grain dust is associated with asthma and chronic bronchitis in grain worker populations. Exposure to fungal particles was postulated to be an important etiologic agent of these pathologies. Fusarium species frequently colonize grain and straw and produce a wide array of mycotoxins that impact human health, necessitating an evaluation of risk exposure by inhalation of Fusarium and its consequences on immune responses. Data showed that Fusarium culmorum is a frequent constituent of aerosols sampled during wheat harvesting in the Vaud region of Switzerland. The aim of this study was to examine cytokine/chemokine responses and innate immune sensing of F. culmorum in bone-marrow-derived dendritic cells and macrophages. Overall, dendritic cells and macrophages responded to F. culmorum spores but not to its secreted components (i.e., mycotoxins) by releasing large amounts of macrophage inflammatory protein (MIP)-1α, MIP-1β, MIP-2, monocyte chemoattractant protein (MCP)-1, RANTES, and interleukin (IL)-12p40, intermediate amounts of tumor necrosis factor (TNF), IL-6, IL-12p70, IL-33, granulocyte colony-stimulating factor (G-CSF), and interferon gamma-induced protein (IP-10), but no detectable amounts of IL-4 and IL-10, a pattern of mediators compatible with generation of Th1 or Th17 antifungal protective immune responses rather than with Th2-dependent allergic responses. The sensing of F. culmorum spores by dendritic cells required dectin-1, the main pattern recognition receptor involved in β-glucans detection, but likely not MyD88 and TRIF-dependent Toll-like receptors. Taken together, our results indicate that F. culmorum stimulates potently innate immune cells in a dectin-1-dependent manner, suggesting that inhalation of F. culmorum from grain dust may promote immune-related airway diseases in exposed worker populations.

Nanoparticle conjugation enhances the immunomodulatory effects of intranasally delivered CpG in house dust mite-allergic mice.

An emerging strategy in preventing and treating airway allergy consists of modulating the immune response induced against allergens in the lungs. CpG oligodeoxynucleotides have been investigated in airway allergy studies, but even if promising, efficacy requires further substantiation. We investigated the effect of pulmonary delivery of nanoparticle (NP)-conjugated CpG on lung immunity and found that NP-CpG led to enhanced recruitment of activated dendritic cells and to Th1 immunity compared to free CpG. We then evaluated if pulmonary delivery of NP-CpG could prevent and treat house dust mite-induced allergy by modulating immunity directly in lungs. When CpG was administered as immunomodulatory therapy prior to allergen sensitization, we found that NP-CpG significantly reduced eosinophilia, IgE levels, mucus production and Th2 cytokines, while free CpG had only a moderate effect on these parameters. In a therapeutic setting where CpG was administered after allergen sensitization, we found that although both free CpG and NP-CpG reduced eosinophilia and IgE levels to the same extent, NP conjugation of CpG significantly enhanced reduction of Th2 cytokines in lungs of allergic mice. Taken together, these data highlight benefits of NP conjugation and the relevance of NP-CpG as allergen-free therapy to modulate lung immunity and treat airway allergy.

Reversible Reprogramming of Circulating Memory T Follicular Helper Cell Function during Chronic HIV Infection.

Despite the overwhelming benefits of antiretroviral therapy (ART) in curtailing viral load in HIV-infected individuals, ART does not fully restore cellular and humoral immunity. HIV-infected individuals under ART show reduced responses to vaccination and infections and are unable to mount an effective antiviral immune response upon ART cessation. Many factors contribute to these defects, including persistent inflammation, especially in lymphoid tissues, where T follicular helper (Tfh) cells instruct and help B cells launch an effective humoral immune response. In this study we investigated the phenotype and function of circulating memory Tfh cells as a surrogate of Tfh cells in lymph nodes and found significant impairment of this cell population in chronically HIV-infected individuals, leading to reduced B cell responses. We further show that these aberrant memory Tfh cells exhibit an IL-2-responsive gene signature and are more polarized toward a Th1 phenotype. Treatment of functional memory Tfh cells with IL-2 was able to recapitulate the detrimental reprogramming. Importantly, this defect was reversible, as interfering with the IL-2 signaling pathway helped reverse the abnormal differentiation and improved Ab responses. Thus, reversible reprogramming of memory Tfh cells in HIV-infected individuals could be used to enhance Ab responses. Altered microenvironmental conditions in lymphoid tissues leading to altered Tfh cell differentiation could provide one explanation for the poor responsiveness of HIV-infected individuals to new Ags. This explanation has important implications for the development of therapeutic interventions to enhance HIV- and vaccine-mediated Ab responses in patients under ART.