SummaryRespiratory syncytial virus (RSV) is a worldwide public health concern for which no vaccine is available. Elucidation of the prefusion structure of the RSV F glycoprotein and its identification as the main target of neutralizing antibodies have provided new opportunities for development of an effective vaccine. Here, we describe the structure-based design of a self-assembling protein nanoparticle presenting a prefusion-stabilized variant of the F glycoprotein trimer (DS-Cav1) in a repetitive array on the nanoparticle exterior. The two-component nature of the nanoparticle scaffold enabled the production of highly ordered, monodisperse immunogens that display DS-Cav1 at controllable density. In mice and nonhuman primates, the full-valency nanoparticle immunogen displaying 20 DS-Cav1 trimers induced neutralizing antibody responses ∼10-fold higher than trimeric DS-Cav1. These results motivate continued development of this promising nanoparticle RSV vaccine candidate and establish computationally designed two-component nanoparticles as a robust and customizable platform for structure-based vaccine design.

A recombinant vaccine containing Aventis Pasteur’s canarypox vector (ALVAC)–HIV and gp120 alum decreased the risk of HIV acquisition in the RV144 vaccine trial. The substitution of alum with the more immunogenic MF59 adjuvant is under consideration for the next efficacy human trial. We found here that an ALVAC–simian immunodeficiency virus (SIV) and gp120 alum (ALVAC–SIV + gp120) equivalent vaccine, but not an ALVAC–SIV + gp120 MF59 vaccine, was efficacious in delaying the onset of SIVmac251 in rhesus macaques, despite the higher immunogenicity of the latter adjuvant. Vaccine efficacy was associated with alum-induced, but not with MF59-induced, envelope (Env)-dependent mucosal innate lymphoid cells (ILCs) that produce interleukin (IL)-17, as well as with mucosal IgG to the gp120 variable region 2 (V2) and the expression of 12 genes, ten of which are part of the RAS pathway. The association between RAS activation and vaccine efficacy was also observed in an independent efficacious SIV-vaccine approach. Whether RAS activation, mucosal ILCs and antibodies to V2 are also important hallmarks of HIV-vaccine efficacy in humans will require further studies.

Summary Analysis of hematopoietic stem cell function in non-human primates provides insights that are relevant for human biology and therapeutic strategies. In this study, we applied quantitative genetic barcoding to track the clonal output of transplanted autologous rhesus macaque hematopoietic stem and progenitor cells over a time period of up to 9.5 months. We found that uni-lineage short-term progenitors reconstituted myeloid and lymphoid lineages at one month, but were supplanted over time by multi-lineage clones, initially myeloid-restricted, then myeloid-B clones, and then stable myeloid-B-T multi-lineage long-term repopulating clones. Surprisingly, reconstitution of the natural killer cell lineage, and particularly the major CD16+/CD56− peripheral blood NK compartment, showed limited clonal overlap with T, B or myeloid lineages, and therefore appears to be ontologically distinct. Thus, in addition to providing insights into clonal behavior over time, our analysis suggests an unexpected paradigm for the relationship between NK cells and other hematopoietic lineages in primates.

Optimal Ag targeting and activation of APCs, especially dendritic cells (DCs), are important in vaccine development. In this study, we report the effects of different Toll-like receptor (TLR)-binding compounds to enhance immune responses induced by human APCs, including CD123+ plasmacytoid DCs (PDCs), CD11c+ myeloid DCs (MDCs), monocytes, and B cells. PDCs, which express TLR7 and TLR9, responded to imidazoquinolines (imiquimod and R-848) and to CpG oligodeoxynucleotides stimulation, resulting in enhancement in expression of costimulatory molecules and induction of IFN-α and IL-12p70. In contrast, MDCs, which express TLR3, TLR4, and TLR7, responded to poly(I:C), LPS, and imidazoquinolines with phenotypic maturation and high production of IL-12 p70 without producing detectable IFN-α. Optimally TLR ligand-stimulated PDCs or MDCs exposed to CMV or HIV-1 Ags enhanced autologous CMV- and HIV-1-specific memory T cell responses as measured by effector cytokine production compared with TLR ligand-activated monocytes and B cells or unstimulated PDCs and MDCs. Together, these data show that targeting specific DC subsets using TLR ligands can enhance their ability to activate virus-specific T cells, providing information for the rational design of TLR ligands as adjuvants for vaccines or immune modulating therapy.

vaccine ͉ dendritic cell ͉ cross-presentation ͉ cellular immunity

The tyrosine kinase inhibitor imatinib (imatinib, STI571, Glivec, and Gleevec) is increasingly used in patients undergoing allogeneic transplantation for leukemia. However, little is known regarding its potential immunoregulatory effects. Here, we investigate the effect of imatinib on T-cell receptor ( IntroductionImatinib mesylate (imatinib, STI571, Glivec, and Gleevec; Novartis, Basel, Switzerland) is a potent selective inhibitor of the tyrosine kinases (TKs) ABL, ARG, PDGFR ␣ and ␤, and c-KIT. It has proven clinical efficacy in the treatment of malignancies characterized by constitutive activation of these TKs: chronic myeloid leukemia (CML), Philadelphia chromosome-positive (Ph ϩ ) acute lymphocytic leukemia (ALL), myleoproliferative disorders due to chromosomal rearrangements in the PDGF-R locus and gastrointestinal stromal tumors (GIST) with mutations in c-KIT. [1][2][3][4][5] Imatinib can induce reversible dose-dependent hematologic side effects, predominantly neutropenia and thrombocytopenia. 3,6 In CML, this may in part be attributed to compromised normal hematopoiesis in addition to suppression of the BCR-ABLpositive clone that can dominate myelopoiesis. An additional mechanism may be inhibition of c-KIT in normal hematopoietic progenitor cells, which could account for the mild imatinib-induced myelosuppression observed in some patients with GIST. 2 However, these mechanisms are unlikely to account fully for the observed lymphopenia and hypogammaglobulinemia in patients with CML on long-term imatinib therapy. In one study, 25% of patients with CML on 400 mg imatinib daily developed mild lymphopenia and a gradual reduction in serum immunoglobulin levels over 3 to 12 months of therapy. 7 Another recent study found an inhibitory effect of imatinib on the development of progenitor cell-derived dendritic cells (DCs) and demonstrated that DCs exposed to imatinib were less potent at inducing primary cytotoxic T-cell reactions against tumor antigens and recall antigens in vitro. 8 The molecular target of imatinib in DCs was not defined but a role for c-KIT inhibition appeared unlikely. This raises the possibility that imatinib could affect normal hematopoiesis and immune function through inhibition of additional TKs.Effects of imatinib on T-cell activation and function have not been well defined. However, TKs play a prominent role in T-cell receptor (TCR) signal transduction and thus it is conceivable that imatinib may interfere with this process. Physiologic activation of T lymphocytes in response to antigen is controlled by the TCR. 9,10 The TCR is comprised of ␣ and ␤ chains, the signaling subunits CD3 ⑀, ␥, and ␦ chains, and TCR . TCR binding to cognate foreign peptide bound to major histocompatibility complex (MHC) molecules on the surface of antigenpresenting cells (APCs) triggers a signaling cascade that includes activation of the TKs LCK and FYN. 11 LCK phosphorylates the immunoreceptor tyrosine-based activation motifs (ITAMs) on the TCR subunits to which ZAP70 is recruited. LCK activates ZAP70, which...

Key Points Neutrophils can present cognate antigens to antigen-specific memory CD4+ T cells. MHC-II and costimulatory molecules are induced on neutrophils in the presence of antigen and antigen-specific memory CD4+ T cells.

There is a remarkable heterogeneity in the functional profile (quality) of T cell responses. Importantly, the magnitude and/or quality of a response required for protection may be different depending on the infection. Here, we assessed the capacity of different Toll like receptor (TLR)-binding compounds to influence T helper cell (Th)1 and CD8+ T cell responses when used as adjuvants in nonhuman primates (NHP) with HIV Gag as a model antigen. NHP were immunized with HIV Gag protein emulsified in Montanide ISA 51, an oil-based adjuvant, with or without a TLR7/8 agonist, a TLR8 agonist, or the TLR9 ligand cytosine phosphate guanosine oligodeoxynucleotides (CpG ODN), and boosted 12 wk later with a replication-defective adenovirus-expressing HIV-Gag (rAD-Gag). Animals vaccinated with HIV Gag protein/Montanide and CpG ODN or the TLR7/8 agonist had higher frequencies of Th1 responses after primary immunization compared to all other vaccine groups. Although the rAD-Gag boost did not elevate the frequency of Th1 memory cytokine responses, there was a striking increase in HIV Gag-specific CD8+ T cell responses after the boost in all animals that had received a primary immunization with any of the TLR adjuvants. Importantly, the presence and type of TLR adjuvant used during primary immunization conferred stability and dramatically influenced the magnitude and quality of the Th1 and CD8+ T cell responses after the rAD-Gag boost. These data provide insights for designing prime-boost immunization regimens to optimize Th1 and CD8+ T cell responses.