Chimeric antigen receptor (CAR) T-cells targeting CD19 mediate potent effects in relapsed/refractory pre-B cell acute lymphoblastic leukemia (B-ALL) but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed on most B-ALL and usually retained following CD19 loss. We report results from a phase I trial testing a novel CD22-CAR in twenty-one children and adults, including 17 previously treated with CD19-directed immunotherapy. Dose dependent anti-leukemic activity was observed with complete remission in 73% (11/15) of patients receiving ≥ 1 × 106 CD22-CART cells/kg, including 5/5 patients with CD19dim/neg B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted escape from killing by CD22-CART cells. These results are the first to eastablish the clinical activity of a CD22-CAR in pre-B cell ALL, including in leukemia resistant to anti-CD19 immunotherapy, demonstrating comparable potency to CD19-CART at biologically active doses in B-ALL. They also highlight the critical role played by antigen density in regulating CAR function. (Funded by NCI Intramural Research Program)

Liposome formation and lipid swelling on platinum electrodes in distilled water and water solutions in d.c. electrical fields have been investigated for different amounts of a negatively charged lipid (mixture from 71% PC, 21.5% PE and 7.5% PS), and a neutral lipid (DMPC). Negatively charged lipids do not form liposomes without field when the thickness of the dried lipid layer is of the order or less than that corresponding to 90 bilayers. The rate and extent of swelling of layers thicker than 90 bilayers is largest on the cathode, smaller without fields and smallest on the anode. The theory, based on the assumption that osmotic and electrostatic forces drive lipid swelling and liposome formation, is in semi-quantitative agreement with the experimental data; in particular, it gives the observed linear dependence of the rate of swelling on the inverse lipid layer thickness. To induce liposome formation for layers thinner than 90 bilayers it was necessary to apply a negative potential which is proportional to the logarithm of the inversed layer thickness. The characteristic critical potential is proportional to RTk/F; R being the gas constant, Tk the absolute temperature and F the Faraday constant. This indicates that redistribution of counterions may be the cause which increases the repulsive electrostatic intermembrane forces to overcome van der Waals attraction. For thicknesses below 10 bilayers, formation of very thin-walled liposomes of narrow size distribution and mean diameter of the order of 30 p m was observed. These liposomes grow in size before detachment and a formula for the kinetics of growth has been derived, which is in very good agreement with the experimental data. The effects of d.c. fields on DMPC swelling are smaller and lead to formation of liposome-like structures of different appearence. Bilayer separation and bending are prerequisites for liposome formation from hydrating lipids. Therefore, a possible molecular mechanism is that membranes should be destabilized to bend and fuse to form liposomes. This requires the right proportion between structured regions, in the form of bilayers, and defects and/or non-bilayer structures, and in many cases external constraints, in particular, electrical fields.Liposome formation from dried lipid in water solutions requires bilayer separation and bending. External electrical fields can facilitate both: they can decrease the intermembrane attraction and can induce instability of bending. This work suggests some experimental evidence and theoretical estimates that electrical fields can induce lipid swelling and liposome formation.After the pioneering work of Bangham et aL' liposomes have been thoroughly investigated [see, e.g. ref.(2)] because of their great application and potential in membrane research, medicine and technology. Relatively little is known, however, of the mechanism of their Helfrich3 and later LasiC4 have used the concept for the curvature elastic energy and boundary interaction energy to explain the formation of liposomes in a bulk liquid...

The remarkable diversity, glycosylation and conformational flexibility of the human immunodeficiency virus type 1 (HIV-1) envelope (Env), including substantial rearrangement of the gp120 glycoprotein upon binding the CD4 receptor, allow it to evade antibody-mediated neutralization. Despite this complexity, the HIV-1 Env must retain conserved determinants that mediate CD4 binding. To evaluate how these determinants might provide opportunities for antibody recognition, we created variants of gp120 stabilized in the CD4-bound state, assessed binding of CD4 and of receptor-binding-site antibodies, and determined the structure at 2.3 Å resolution of the broadly neutralizing antibody b12 in complex with gp120. b12 binds to a conformationally invariant surface that overlaps a distinct subset of the CD4-binding site. This surface is involved in the metastable attachment of CD4, before the gp120 rearrangement required for stable engagement. A site of vulnerability, related to a functional requirement for efficient association with CD4, can therefore be targeted by antibody to neutralize HIV-1.The human immunodeficiency virus type 1 (HIV-1) crossed from chimpanzees to humans early in the twentieth century and has since infected ~1% of the world's adult population 1,2 . ThisCorrespondence and requests for materials should be addressed to P.D.K. (pdkwong@nih.gov). Author Contributions T.Z. and P.D.K. carried out structure-based stabilization, SPR analyses and structural determinations; L.X. and G.J.N. constructed gp120 substitutions and developed and implemented a high-throughput gp120-production system suitable for crystallization; B.D. and R.W. carried out ITC characterizations; A.J.H., M.B.Z. and D.R.B. provided b12, b3, b6, b11 and b13, and mutant b12 binding; D.V.R. and J.A. provided D1D2-Igαtp and associated SPR analyses; S.-H.X., X.Y. and J.S. provided OD1 and preliminary design and antigenic analyses; and M.-Y.Z. and D.S.D. provided m6, m14 and m18. All authors contributed to the manuscript preparation.Author Information Coordinates and structure factors have been deposited in the Protein Data Bank and may be obtained from the authors (accession codes 2nxy-2ny6 for the nine variant gp120 molecules with CD4 and 17b; accession code 2ny7 for the b12-gp120 complex). Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests. spread and the absence of an effective vaccine are to a large degree a consequence of the ability of HIV-1 to evade antibody-mediated neutralization 3-5 . On HIV-1, the only viral target available for neutralizing antibodies is the envelope spike, which is composed of three copies of the gp120 exterior envelope glycoprotein and three gp41 transmembrane glyco-protein molecules 6,7 . Genetic, immunological and structural studies of the HIV-1 envelope glycoproteins have revealed extraordinary diversity, manifest in a variety of immunodominant loops, as well as multiple overlapping mechanisms of humoral evasion, including se...

The third variable region (V3) of the HIV-1 gp120 envelope glycoprotein is immunodominant and contains features essential for coreceptor binding. We determined the structure of V3 in the context of an HIV-1 gp120 core complexed to the CD4 receptor and to the X5 antibody at 3.5 angstrom resolution. Binding of gp120 to cell-surface CD4 would position V3 so that its coreceptor-binding tip protrudes 30 angstroms from the core toward the target cell membrane. The extended nature and antibody accessibility of V3 explain its immunodominance. Together, the results provide a structural rationale for the role of V3 in HIV entry and neutralization.

Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1-mediated (PD-1-mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB-based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies.

Identifying the immunologic and virologic consequences of discontinuing antiretroviral therapy in HIV-infected patients is of major importance in developing long-term treatment strategies for patients with HIV-1 infection. We designed a trial to characterize these parameters after interruption of highly active antiretroviral therapy (HAART) in patients who had maintained prolonged viral suppression on antiretroviral drugs. Eighteen patients with CD4 ؉ T cell counts > 350 cells͞l and viral load below the limits of detection for >1 year while on HAART were enrolled prospectively in a trial in which HAART was discontinued. Twelve of these patients had received prior IL-2 therapy and had low frequencies of resting, latently infected CD4 cells. Viral load relapse to >50 copies͞ml occurred in all 18 patients independent of prior IL-2 treatment, beginning most commonly during weeks 2-3 after cessation of HAART. The mean relapse rate constant was 0.45 (0.20 log 10 copies) day ؊1 , which was very similar to the mean viral clearance rate constant after drug resumption of 0.35 (0.15 log 10 copies) day ؊1 (P ‫؍‬ 0.28). One patient experienced a relapse delay to week 7. All patients except one experienced a relapse burden to >5,000 RNA copies͞ml. Ex vivo labeling with BrdUrd showed that CD4 and CD8 cell turnover increased after withdrawal of HAART and correlated with viral load whereas lymphocyte turnover decreased after reinitiation of drug treatment. Virologic relapse occurs rapidly in patients who discontinue suppressive drug therapy, even in patients with a markedly diminished pool of resting, latently infected CD4 ؉ T cells.HIV-1 infection ͉ antiretroviral drugs ͉ viral load ͉ relapse ͉ CD4

Viruses have evolved to enter cells from all three domains of life--Bacteria, Archaea and Eukaryotes. Of more than 3,600 known viruses, hundreds can infect human cells and most of those are associated with disease. To gain access to the cell interior, animal viruses attach to host-cell receptors. Advances in our understanding of how viral entry proteins interact with their host-cell receptors and undergo conformational changes that lead to entry offer unprecedented opportunities for the development of novel therapeutics and vaccines.

Key Points• We have created a new highly active chimeric antigen receptor (CAR) specific for CD22.• The design of new CARs may benefit more from target antigen epitope selection than from optimizing affinity.Immune targeting of B-cell malignancies using chimeric antigen receptors (CARs) is a promising new approach, but critical factors impacting CAR efficacy remain unclear. To test the suitability of targeting CD22 on precursor B-cell acute lymphoblastic leukemia (BCP-ALL), lymphoblasts from 111 patients with BCP-ALL were assayed for CD22 expression and all were found to be CD22-positive, with median CD22 expression levels of 3500 sites/cell. Three distinct binding domains targeting CD22 were fused to various TCR signaling domains ؎ an IgG heavy chain constant domain (CH2CH3) to create a series of vector constructs suitable to delineate optimal CAR configuration. CARs derived from the m971 anti-CD22 mAb, which targets a proximal CD22 epitope demonstrated superior antileukemic activity compared with those incorporating other binding domains, and addition of a 4-1BB signaling domain to CD28.CD3 constructs diminished potency, whereas increasing affinity of the anti-CD22 binding motif, and extending the CD22 binding domain away from the membrane via CH2CH3 had no effect. We conclude that second-generation m971 mAb-derived anti-CD22 CARs are promising novel therapeutics that should be tested in BCP-ALL. (Blood. 2013;121(7):1165-1174) IntroductionDespite great progress in the treatment of children and adults with acute lymphoblastic leukemia (ALL), substantial numbers of patients continue to die of this disease and the short and long-term toxicities of standard therapy are substantial. 1-3 Monoclonal antibody-based therapies offer promise for overcoming chemoresistance and potentially diminishing the toxicities associated with therapy. 4 Among the most promising of these therapies involve the engineering of mature T lymphocytes to recognize MHC nonrestricted tumor antigens by transducing chimeric antigen receptors (CARs), reviewed by Lee at al. 5 CARs incorporate an extracellular binding domain (often derived from the antigen binding region of an antibody) with transmembrane and signaling motifs to render T cells capable of targeting any surface antigen that is amenable to antibody-like recognition. Early clinical results have demonstrated impressive antitumor effects in patients with leukemia, 6-10 although the ideal CAR design with respect to structural and signaling features remains unclear and has been the topic of intense inquiry.B-cell antigens are compelling targets for CAR-based therapies because normal tissue expression of these antigens is restricted to the B-cell lineage and clinical tolerance for B-cell ablation is high using modern supportive care. Indeed, CARs targeting CD19 have demonstrated activity against B-cell malignancies with acceptable toxicity 6-8 as have anti-CD20 antibodies in CD20 ϩ malignancies, including CD20-expressing ALL. 11 CD22 is another member of the B-cell antigen family with a tis...