The flavivirus nonstructural protein NS1 is a highly conserved secreted glycoprotein that does not package with the virion. Immunization with NS1 elicits a protective immune response against yellow fever, dengue, and tick-borne encephalitis flaviviruses through poorly defined mechanisms. In this study, we purified a recombinant, secreted form of West Nile virus (WNV) NS1 glycoprotein from baculovirus-infected insect cells and generated 22 new NS1-specific monoclonal antibodies (MAbs). By performing competitive binding assays and expressing truncated NS1 proteins on the surface of yeast (Saccharomyces cerevisiae) and in bacteria, we mapped 21 of the newly generated MAbs to three NS1 fragments. Prophylaxis of C57BL/6 mice with any of four MAbs (10NS1, 14NS1, 16NS1, and 17NS1) strongly protected against lethal WNV infection (75 to 95% survival, respectively) compared to saline-treated controls (17% survival). In contrast, other anti-NS1 MAbs of the same isotype provided no significant protection. Notably, 14NS1 and 16NS1 also demonstrated marked efficacy as postexposure therapy, even when administered as a single dose 4 days after infection. Virologic analysis showed that 17NS1 protects at an early stage in infection through a C1q-independent and Fc ␥ receptor-dependent pathway. Interestingly, 14NS1, which maps to a distinct region on NS1, protected through a C1q-and Fc ␥ receptor-independent mechanism. Overall, our data suggest that distinct regions of NS1 can elicit protective humoral immunity against WNV through different mechanisms.West Nile virus (WNV) is a single-stranded, positive-senseenveloped RNA virus that is maintained in nature through a mosquito-bird-mosquito transmission cycle. It is endemic in parts of Africa, Europe, the Middle East, and Asia, and outbreaks now occur annually in North America. Humans, which are dead-end hosts, can develop a febrile illness that progresses to a meningitis or encephalitis syndrome (32). At present, treatment is supportive, and no vaccine exists for human use.A member of the Flaviviridae family, WNV is closely related to other major human pathogens such as yellow fever (YF), dengue (DEN), tick-borne encephalitis (TBE), Japanese encephalitis (JEV), and Murray Valley encephalitis (MVE) viruses. The 10.7-kilobase genome is translated as a single polyprotein, which is then cleaved into three structural proteins (C, prM/M, and E) and seven nonstructural (NS) proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) by both virus-and host-encoded proteases (5). The NS proteins include an RNA-dependent RNA polymerase (NS5), a helicase/protease (NS3), and other proteins that form part of the viral replication complex (36, 37).NS1 is a highly conserved 48-kDa glycoprotein with 12 invariant cysteine residues. Although the disulfide linkage arrangement of MVE and DEN NS1 has been described (4, 66), structural analysis is currently lacking. NS1 is inserted into the lumen of the endoplasmic reticulum via a signal peptide that is cleaved cotranslationally by a cellular signalase to gene...
Previous studies have suggested that monoclonal antibodies (MAbs) to flavivirus nonstructural protein-1 (NS-1) protect against infection in mice through an Fc-␥ receptor-dependent pathway. To identify a specific mechanism, we evaluated the protective activity of anti-NS1 MAbs to WNV using mice and cells with deficiencies of specific Fc-␥ receptors. Our results suggest that only MAbs that recognize cell surface-associated NS1 trigger Fc-␥ receptor I-and/or IV-mediated phagocytosis and clearance of WNV-infected cells. These findings may be relevant for generating novel therapeutic MAbs or vaccines against flaviviruses that target the NS1 protein.
Defining the precise cellular mechanisms of neutralization by potently inhibitory antibodies is important for understanding how the immune system successfully limits viral infections. We recently described a potently inhibitory monoclonal antibody (MAb E16) against the envelope (E) protein of West Nile virus (WNV) that neutralizes infection even after virus has spread to the central nervous system. Herein, we define its mechanism of inhibition. E16 blocks infection primarily at a post-attachment step as antibody-opsonized WNV enters permissive cells but cannot escape from endocytic compartments. These cellular experiments suggest that E16 blocks the acid-catalyzed fusion step that is required for nucleocapsid entry into the cytoplasm. Indeed, E16 directly inhibits fusion of WNV with liposomes. Additionally, low-pH exposure of E16–WNV complexes in the absence of target membranes did not fully inactivate infectious virus, further suggesting that E16 prevents a structural transition required for fusion. Thus, a strongly neutralizing anti–WNV MAb with therapeutic potential is potently inhibitory because it blocks viral fusion and thereby promotes clearance by delivering virus to the lysosome for destruction.
Lipopolysaccharide (LPS) has long been known to enhance innate and adaptive immune responses; however, its extreme toxicity precludes its use in clinical settings. The combined toxicity and adjuvanticity of LPS have contributed to the view that immunological adjuvants need to be highly inflammatory to be maximally effective. Here, we compared the effects of LPS with its less-toxic derivatives, monophosphoryl lipid A (MPL) and a chemical mimetic, RC529, on CD4+ T cell clonal expansion, long-term survival, and T helper cell type 1 (Th1) differentiation. We found that LPS, MPL, and RC529 had similar effects on CD4+ T cell clonal expansion, cell division, and ex vivo survival. Analysis of the ability of activated CD4+ T cells to produce interferon-gamma following a 21-day immunization and challenge protocol with LPS and MPL resulted in similar Th1 differentiation. In contrast, we found that LPS was more effective in promoting long-term CD4+ T cell responses, as we recovered nearly sixfold more cells following immunization/challenge as compared with treatment with MPL. Our results indicate that low-inflammation adjuvants, such as MPL and RC529, are capable of enhancing short-term CD4+ T cell clonal expansion and Th1 differentiation, but inflammatory signaling aids in the long-term retention of antigen-specific T cells.
Background: Despite advances in the treatment of multiple myeloma (MM) almost all patients relapse and high risk features continue to portend a short median survival. The adoptive transfer of B-Cell Maturation Antigen (BCMA) chimeric antigen receptor (CAR) T cells is demonstrating early promise in MM, but the durability of response has not been established. The infusion of genetically modified CD8+ and CD4+ T cells of a defined composition facilitates the evaluation of each subset's function and has contributed to reproducible efficacy and safety in clinical trials with CD19-specific CAR T cells. In this phase I first-in-human study employing a human scFv containing BCMA CAR T cell construct, we report rapid and deep objective responses at a low CAR T cell dose level (5 x 107) suggesting that construct specific features and differences in product formulation may substantially impact efficacy. Methods: Eligible patients had relapsed or treatment refractory MM, ≥10% CD138+ bone marrow (BM) plasma cells (PC), and ≥5% BCMA expression by flow cytometry (FC). Patients were stratified by tumor burden (CD138+ IHC) into two cohorts; 10-30% MM cells [cohort A] or >30% BM involvement [cohort B] to facilitate assessment of impact of disease burden on outcome. Eligible patient's CD8+ and CD4+ T cells were isolated via positive selection, enriched separately by immunomagnetic selection and cryopreserved. The CD8+ and CD4+ T cells were stimulated in independent cultures with anti-CD3/anti-CD28 paramagnetic beads and transduced with a 3rd generation lentiviral vector encoding a fully human BCMA scFv and 4-1BB and CD3 zeta signaling domains. After in vitro expansion, the cell product for infusion was formulated in a 1:1 ratio of CD4+:CD8+ BCMA CAR T cells. A truncated non-functional human epidermal growth factor receptor (EGFRt) was encoded in the transgene cassette to identify transduced T cells. Lymphodepleting chemotherapy preceded infusion of EGFRt+ CAR T cells at a starting dose of 5 x 107 EGFRt+ cells (n=5) for each cohort. Results: Seven patients (median age of 63 years; range 49 to 76) with a median of 8 prior regimens (range 6 to 11) have received treatment. The median %PC in BM (IHC) at enrollment was 58% (range 20% to >80%). In cohort B the dose has been escalated to 15 x107 EGFRt+ cells (n=2). All patients (7/7) had at least one high risk cytogenetic feature (17p- [n=4], t(4;14) [n=2], t(14;16) [n=1]), 71% had ≥ 2 high risk cytogenetic features, 71% had prior autologous stem cell transplant, 43% had prior allogeneic transplant, and one patient (14%) had PCL. The median involved free light chain (FLC) at enrollment was 180 mg/dL (range 40.37 to 502.96 mg/dL; n=5) and the median monoclonal protein was 3.8 g/dL (range 1.6 to 6.5 g/dL; n=5). The overall response rate at 28 days was 100%; at this time all evaluable patients (n=6) had no detectable abnormal BM PC clone by both IHC and high sensitivity FC. Within 28 days of treatment the involved FLC was normal or sub-normal in all patients and the M-protein had decreased by a median of 73% (range 56.25 to 83% reduction). BCMA CAR T cells remained detectable 90 days after infusion, representing up to 41.5 percent of CD3+ lymphocytes. All patients were surviving at a median of 16 wks (range 2 to 26 wks). One patient relapsed (day +60) and a tumor biopsy demonstrated the presence of a BCMAneg PC population, a 70% reduction in the fraction of MM cells expressing BCMA by FC and a fivefold reduction in BCMA antigen binding capacity on MM cells retaining target expression. A cytotoxic T lymphocyte response to the trans-gene product was not identified in this patient. No dose limiting toxicity has been observed during the 28 day monitoring window and treatment has been well tolerated with no cytokine release syndrome (CRS) observed in one patient and grade 2 or lower CRS (Lee Criteria) for all other patients. No neurological toxicity has been observed. Conclusion: BCMA CAR T cells harboring a fully human scFv with a defined composition of CD4+:CD8+ T cells were well tolerated and potent, demonstrating complete objective responses in heavily pretreated high-risk MM at total cell doses as low as 5 x 107. Next generation sequencing and multiparameter high sensitivity flow cytometry studies to evaluate for minimal residual disease are ongoing. Peak expansion levels and persistence of the CAR T cells are being monitored with early findings suggesting an absence of transgene product immunogenicity. Disclosures Green: Juno Therapeutics: Patents & Royalties, Research Funding. Sather:Juno Therapeutics: Employment. Cowan:Janssen: Research Funding; Abbvie: Research Funding; Juno Therapeutics: Research Funding; Sanofi: Research Funding. Turtle:Caribou Biosciences: Consultancy; Gilead: Consultancy; Bluebird Bio: Consultancy; Precision Biosciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Aptevo: Consultancy; Eureka Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Nektar Therapeutics: Consultancy, Research Funding; Juno Therapeutics / Celgene: Consultancy, Patents & Royalties, Research Funding; Adaptive Biotechnologies: Consultancy. Till:Mustang Bio: Patents & Royalties, Research Funding. Becker:GlycoMimetics: Research Funding. Blake:Celgene: Employment, Equity Ownership. Works:Juno Therapeutics: Employment. Maloney:GlaxoSmithKline: Research Funding; Juno Therapeutics: Research Funding; Seattle Genetics: Honoraria; Roche/Genentech: Honoraria; Janssen Scientific Affairs: Honoraria. Riddell:Cell Medica: Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding; Adaptive Biotechnologies: Consultancy; NOHLA: Consultancy.
Mucosal Associated Invariant T (MAIT) cells are an “innate” T cell population expressing an invariant TCRα chain, mVαl9 in mice and hVα7.2 in humans. Strikingly similar to CD 1d‐restricted iNKT cells, MAIT cells have a memory phenotype and rapidly release IFN‐γ, IL‐4, 5, and 10 upon TCR ligation. Interestingly, MAIT cells are also restricted by an MHC class I like molecule, MR1. But, unlike iNKT cells, MAIT cells require B cells and gut commensal flora for development and/or expansion. Although the ligand presented by MR1 is unknown, evidence strongly suggests that MAIT cell activation is ligand‐dependent. Here we demonstrate that MR1 antigen presentation is not affected by either the proteasome or the class I chaperones. However, the class II chaperone invariant chain, Ii, physically associates with MR1 and promotes its endosomal trafficking. Functionally, MAIT cell activation is enhanced by Ii overexpression but strikingly diminished by silencing endogenous Ii. Furthermore, confocal microscopy confirms localization of MR1 in late endosomes and inhibiting the acidification of these compartments reduces MR1 surface expression and ablates MAIT cell activation. These data indicate that MR1 traffics through endocytic compartments, thereby allowing MAIT cells to potentially sample both endocytosed and endogenous antigens.
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