Identification and X-ray Co-crystal Structure of a Small-Molecule Activator of LFA-1-ICAM-1 Binding

The integrin Leucocyte function associated antigen 1 (LFA-1) is a heterodimeric immune receptor ubiquitously expressed on all leucocytes. Its interaction with Intercellular adhesion molecule 1 (ICAM-1) provides a critical recognition event between T-cells and antigen presenting cells in the immune systems efforts to pull off an early stage cell mediated immune response.[1–3] The LFA-1/ICAM-1 axis has thus been explored as a target interaction for drug discovery.[4–7] Furthermore, the structural changes of LFA-1 upon activation and interaction with ICAM-1 also make the LFA-1/ICAM-1 interaction an interesting example of protein-protein interaction (PPI) inhibition by small molecule inhibitors.[8,9] While protein-protein interaction inhibition by small molecules is considered to be the ultimate art in drug design, even fewer examples of true agonists of PPIs have been reported.[10–12] As for LFA-1, such activators would have interesting applications in rare hereditary genetic disorders called Leucocyte adhesion deficiency (LAD) or as potential enhancers of tumour immunotherapy.[13,14] Although, one such activator has been described recently, closer biological investigation has shown that it ultimately worked as an inhibitor on a cellular level by locking the LFA-1/ICAM-1 interaction when reversibility was needed for detachment of immune cells from endothelial surfaces and tissue infiltration.[15] Herein we describe the identification and structural biology of IBE-667, an ICAM-1 binding enhancer for LFA-1 from on-bead screening of tagged one-bead one-compound combinatorial libraries by confocal nanoscanning and bead picking (CONA).[16] Cellular assays demonstrate the activity of IBE-667 in promoting the binding of LFA-1 on activated immune cells to ICAM-1. X-ray structure based analysis did not only allow us to explain the molecular features of IBE-667 binding to LFA-1 but also offers an explanation for its mode of action

Identification of a Small Molecule Inhibitor of Importin β Mediated Nuclear Import by Confocal On-Bead Screening of Tagged One-Bead One-Compound Libraries

In eukaryotic cells, proteins and RNAs are transported between the nucleus and the cytoplasm by nuclear import and export receptors. Over the past decade, small molecules that inhibit the nuclear export receptor CRM1 have been identified, most notably,leptomycin B. However, up to now no small molecule inhibitors of nuclear import have been described. Here we have used our automated confocal nanoscanning and bead picking method (CONA) for on-bead screening of a one-bead one-compound library to identify the first such import inhibitor, karyostatin 1A. Karyostatin 1A binds importin beta with high nanomolar affinity and specifically inhibits importin alpha/beta mediated nuclear import at low micromolar concentrations in vitro and in living cells, without perturbing transportin mediated nuclear import or CRM1 mediated nuclear export. Surface plasmon resonance binding-experiments suggest that karyostatin 1A acts by disrupting the interaction between importin p and the OPase Ran. As a selective inhibitor of the importin alpha/beta import pathway, karyostatin 1A will provide a valuable tool for future studies of nucleocytoplasmic trafficking.</p

Analysis of the functional WT1-specific T-cell repertoire in healthy donors reveals a discrepancy between CD4(+) and CD8(+) memory formation

The Wilms' tumour-1 (WT1) protein is considered a prime target for cancer immunotherapy based on its presumptive immunogenicity and widespread expression across a variety of malignancies. However, little is known about the naturally occurring WT1-specific T-cell repertoire because self-derived antigens typically elicit low frequency responses that challenge the sensitivity limits of current detection techniques. In this study, we used highly efficient cell enrichment procedures based on CD137, CD154, and pHLA class I tetramer staining to conduct a detailed analysis of WT1-specific T cells from the peripheral blood. Remarkably, we detected WT1-specific CD4(+) and CD8(+) T-cell populations in the vast majority of healthy individuals. Memory responses specific for WT1 were commonly present in the CD4(+) T-cell compartment, whereas WT1-specific CD8(+) T cells almost universally displayed a naive phenotype. Moreover, memory CD4(+) and naive CD8(+) T cells with specificity for WT1 were found to coexist in some individuals. Collectively, these findings suggest a natural discrepancy between the CD4(+) and CD8(+) T-cell lineages with respect to memory formation in response to a self-derived antigen. Nonetheless, WT1-specific T cells from both lineages were readily activated ex vivo and expanded in vitro, supporting the use of strategies designed to exploit this expansive reservoir of self-reactive T cells for immunotherapeutic purposes

The chemical hunt for the identification of drugable targets.

Chemical biology has emerged as a new scientific discipline to change the way scientists approach and study the interface between chemistry, biology, and physics. By integrating the knowledge base of the human genome with the power of diverse and flexible chemical technology platforms, the ultimate goal is to define the 'rules of engagement' for small molecules and their use in basic biology and in drug discovery. Herein, we highlight the current counterpoles of the chemical biology philosophy in the framework between conformational diversity and informational complexity. Expanding the growing molecular recognition information matrix into classification of diseases and immediate mechanistic in-vivo proof of concept models represent the next development phase in a field that, unlike any other due to its multidisciplinary nature, unifies basic scientists and drug discoverers

A Lower CD4 Count Predicts Most Causes of Death except Cardiovascular Deaths. The Austrian HIV Cohort Study

(1) Objective: To investigate changes in mortality rates and predictors of all-cause mortality as well as specific causes of death over time among HIV-positive individuals in the combination antiretroviral therapy (cART) era. (2) Methods: We analyzed all-cause as well as cause-specific mortality among the Austrian HIV Cohort Study between 1997 and 2014. Observation time was divided into five periods: Period 1: 1997-2000; period 2: 2001-2004; period 3: 2005-2008; period 4: 2009-2011; and period 5: 2012-2014. Mortality rates are presented as deaths per 100 person-years (d/100py). Potential risk factors associated with all-cause mortality and specific causes of death were identified by using multivariable Cox proportional hazard models. Models were adjusted for time-updated CD4, age and cART, HIV transmission category, population size of residence area and country of birth. To assess potential nonlinear associations, we fitted all CD4 counts per patient using restricted cubic splines with truncation at 1000 cells/mm$^{3}$. Vital status of patients was cross-checked with death registry data. (3) Results: Of 6848 patients (59,704 person-years of observation), 1192 died: 380 (31.9%) from AIDS-related diseases. All-cause mortality rates decreased continuously from 3.49 d/100py in period 1 to 1.40 d/100py in period 5. Death due to AIDS-related diseases, liver-related diseases and non-AIDS infections declined, whereas cardiovascular diseases as cause of death remained stable (0.27 d/100py in period 1, 0.10 d/100py in period 2, 0.16 d/100py in period 3, 0.09 d/100py in period 4 and 0.14 d/100py in period 5) and deaths due to non-AIDS-defining malignancies increased. Compared to latest CD4 counts of 500 cells/mm$^{3}$, lower CD4 counts conferred a higher risk of deaths due to AIDS-related diseases, liver-related diseases, non-AIDS infections and non-AIDS-defining malignancies, whereas no significant association was observed for cardiovascular mortality. Results were similar in sensitivity analyses where observation time was divided into two periods: 1997-2004 and 2005-2014. (4) Conclusions: Since the introduction of cART, risk of death decreased and causes of death changed. We do not find evidence that HIV-positive individuals with a low CD4 count are more likely to die from cardiovascular diseases