Synergistic antiviral effect of hydroxychloroquine and azithromycin in combination against SARS-CoV-2: What molecular dynamics studies of virus-host interactions reveal.

The emergence of SARS-coronavirus-2 (SARS-CoV-2) has led to a global pandemic disease referred to as coronavirus disease 19 (COVID-19). Hydroxychloroquine (CLQ-OH)/azithromycin (ATM) combination therapy is currently being tested for the treatment of COVID-19, with promising results. However, the molecular mechanism of action of this combination is not yet established. Using molecular dynamics (MD) simulations, this study shows that the drugs act in synergy to prevent any close contact between the virus and the plasma membrane of host cells. Unexpected molecular similarity is shown between ATM and the sugar moiety of GM1, a lipid raft ganglioside acting as a host attachment cofactor for respiratory viruses. Due to this mimicry, ATM interacts with the ganglioside-binding domain of SARS-CoV-2 spike protein. This binding site shared by ATM and GM1 displays a conserved amino acid triad Q-134/F-135/N-137 located at the tip of the spike protein. CLQ-OH molecules are shown to saturate virus attachment sites on gangliosides in the vicinity of the primary coronavirus receptor, angiotensin-converting enzyme-2 (ACE-2). Taken together, these data show that ATM is directed against the virus, whereas CLQ-OH is directed against cellular attachment cofactors. We conclude that both drugs act as competitive inhibitors of SARS-CoV-2 attachment to the host-cell membrane. This is consistent with a synergistic antiviral mechanism at the plasma membrane level, where therapeutic intervention is likely to be most efficient. This molecular mechanism may explain the beneficial effects of CLQ-OH/ATM combination therapy in patients with COVID-19. Incidentally, the data also indicate that the conserved Q-134/F-135/N-137 triad could be considered as a target for vaccine strategies.

Natural killer cells and pigment epithelial-derived factor control the infiltrative and nodular growth of hepatic metastases in an Orthotopic murine model of ocular melanoma.

BACKGROUND: Metastases account for 90% of all cancer-related deaths, becoming a therapeutic problem. Approximately 50% of all uveal melanoma (UM) patients will develop metastases, mainly in the liver. Post-mortem analyses of livers from metastatic UM patients showed two different metastatic growth patterns: infiltrative and nodular. The infiltrative pattern exhibits tumor infiltration directly to the hepatic lobule and minimal angiogenesis. The nodular pattern shows clusters of tumor cells around the portal venules that efface the liver parenchyma. We recently demonstrated Natural Killer (NK) cells play a pivotal role in the control of hepatic metastases and the pigment epithelial-derived factor (PEDF) controls angiogenesis in the liver using our established ocular melanoma animal model. In this study we investigated the role of NK cells and PEDF in the development of metastatic growth patterns, as this can contribute to the development of novel therapeutics specific towards each growth pattern. METHODS: We utilize our established ocular melanoma animal model by inoculation of B16-LS9 melanoma cells into C57BL/6 J mice (WT), anti-asialo GM1-treated C57BL/6 J mice (NK-depleted), and PEDF-/- C57BL/6 J mice. Three weeks after inoculation we evaluated the metastatic growth patterns and stratified them based of the numbers of tumor cells. To evaluate angiogenesis the mean vascular density (MVD) was calculated. The immune compartment of the liver was analyzed by flow cytometry. RESULTS: Our in vivo work showed two distinct metastatic growth patterns, the infiltrative and nodular, recapitulating the post-mortem analyses on human liver tissue. We discovered NK cells control the infiltrative growth. In contrast, PEDF controlled anti-angiogenic responses, showing higher MVD values compared to NK-depleted and WT animals. The myeloid lineage, comprised of monocytes, macrophages, and myeloid-derived suppressor cells, was reduced in the absence of NK cells or PEDF. CONCLUSIONS: Our animal model recapitulates the metastatic growth patterns observed in the human disease. We demonstrated a role for NK cells in the development of the infiltrative growth pattern, and a role for PEDF in the development of the nodular pattern. The understanding of the complexity associated with the metastatic progression has profound clinical implications in the diagnostic and disease-management as we can develop and direct more effective therapies.

A Novel, Fully Human Anti-fucosyl-GM1 Antibody Demonstrates Potent In Vitro and In Vivo Antitumor Activity in Preclinical Models of Small Cell Lung Cancer.

Purpose: The ganglioside fucosyl-GM1 (FucGM1) is a tumor-associated antigen expressed in a large percentage of human small cell lung cancer (SCLC) tumors, but absent in most normal adult tissues, making it a promising target in immuno-oncology. This study was undertaken to evaluate the preclinical efficacy of BMS-986012, a novel, nonfucosylated, fully human IgG1 antibody that binds specifically to FucGM1.Experimental Design: The antitumor activity of BMS-986012 was evaluated in in vitro assays using SCLC cells and in mouse xenograft and syngeneic tumor models, with and without chemotherapeutic agents and checkpoint inhibitors.Results: BMS-986012 showed a high binding affinity for FcγRIIIa (CD16), which resulted in enhanced antibody-dependent cellular cytotoxicity (ADCC) against FucGM1-expressing tumor cell lines. BMS-986012-mediated tumor cell killing was also observed in complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP) assays. In several mouse SCLC models, BMS-986012 demonstrated efficacy and was well tolerated. In the DMS79 xenograft model, tumor regression was achieved with BMS-986012 doses of 0.3 mg/kg and greater; antitumor activity was enhanced when BMS-986012 was combined with standard-of-care cisplatin or etoposide. In a syngeneic model, tumors derived from a genetically engineered model of SCLC were treated with BMS-986012 or anti-FucGM1 with a mouse IgG2a Fc and their responses evaluated; when BMS-986012 was combined with anti-PD-1 or anti-CD137 antibody, therapeutic responses significantly improved.Conclusions: Single-agent BMS-986012 demonstrated robust antitumor activity, with the addition of chemotherapeutic or immunomodulatory agents further inhibiting SCLC growth in the same models. These preclinical data supported evaluation of BMS-986012 in a phase I clinical trial of patients with relapsed, refractory SCLC. Clin Cancer Res; 24(20); 5178-89. ©2018 AACR.

Revealing the Raft Domain Organization in the Plasma Membrane by Single-Molecule Imaging of Fluorescent Ganglioside Analogs.

Gangliosides have been implicated in a variety of physiological processes, particularly in the formation and function of raft domains in the plasma membrane. However, the scarcity of suitable fluorescent ganglioside analogs had long prevented us from determining exactly how gangliosides perform their functions in the live-cell plasma membrane. With the development of new fluorescent ganglioside analogs, as described by Komura et al. (2017), this barrier has been broken. We can now address the dynamic behaviors of gangliosides in the live-cell plasma membrane, using fluorescence microscopy, particularly by single-fluorescent molecule imaging and tracking. Single-molecule tracking of fluorescent GM1 and GM3 revealed that these molecules are transiently and dynamically recruited to monomers (monomer-associated rafts) and homodimer rafts of the raftophilic GPI-anchored protein CD59 in quiescent cells, with exponential residency times of 12 and 40ms, respectively, in a manner dependent on raft-lipid interactions. Upon CD59 stimulation, which induces CD59-cluster signaling rafts, the fluorescent GM1 and GM3 analogs were recruited to the signaling rafts, with a lifetime of 48ms. These results represent the first direct evidence that GPI-anchored receptors and gangliosides interact in a cholesterol-dependent manner. Furthermore, they show that gangliosides continually move in and out of rafts that contain CD59 in an extremely dynamic manner, with much higher frequency than expected previously. Such studies would not have been possible without fluorescent ganglioside probes, which exhibit native-like behavior and single-molecule tracking. In this chapter, we review the methods for single-molecule tracking of fluorescent ganglioside analogs and the results obtained by applying these methods.

Natural killer cells play an essential role in resolution of antigen-induced inflammation in mice.

This study examined whether NK cells are important for resolution of antigen-induced inflammation. C57BL/6 mice were immunized twice with methylated BSA (mBSA) and inflammation induced by intraperitoneal injection of mBSA. Mice were injected intravenously with anti-asialo GM1 (αASGM1) or a control antibody 24h prior to peritonitis induction and peritoneal exudate collected at different time points. Expression of surface molecules and apoptosis on peritoneal cells was determined by flow cytometry and concentration of chemokines, cytokines, soluble cytokine receptors and lipid mediators by ELISA and LC-MS/MS. Apoptosis in parathymic lymph nodes and spleens was determined by TUNEL staining. Mice administered αASGM1 had lower peritoneal NK cell numbers and a higher number of peritoneal neutrophils 12h after induction of inflammation than control mice. The number of neutrophils was still high in the αASGM1 treated mice when their number had returned to baseline levels in the control mice, 48h after induction of inflammation. Peritoneal concentrations of the neutrophil regulators G-CSF and IL-12p40 were higher at 12h in the αASGM1 treated mice than in the control mice, whereas concentrations of lipid mediators implicated in resolution of inflammation, i.e. LXA4 and PGE2, were lower. Reduced apoptosis was detected in peritoneal neutrophils as well as in draining lymph nodes and spleens from the αASGM1 treated mice compared with that in the control mice. In addition, αASGM1 treated mice had lower number of peritoneal NK cells expressing NKp46 and NKG2D, receptors implicated in NK cell-induced neutrophil apoptosis. Furthermore, αASGM1 treatment completely blocked the increase in CD27+ NK cells that occurred in control mice following induction of inflammation, but CD27+ NK cells have been suggested to have a regulatory role. These results indicate a crucial role for NK cells in resolution of antigen-induced inflammation and suggest their importance in tempering neutrophil recruitment and maintaining neutrophil apoptosis.

Protection against Experimental Stroke by Ganglioside GM1 Is Associated with the Inhibition of Autophagy.

UNLABELLED: Ganglioside GM1, which is particularly abundant in the central nervous system (CNS), is closely associated with the protection against several CNS disorders. However, controversial findings have been reported on the role of GM1 following ischemic stroke. In the present study, using a rat middle cerebral artery occlusion (MCAO) model, we investigated whether GM1 can protect against ischemic brain injury and whether it targets the autophagy pathway. GM1 was delivered to Sprague-Dawley male rats at 3 doses (25 mg/kg, 50 mg/kg, 100 mg/kg) by intraperitoneal injection soon after reperfusion and then once daily for 2 days. The same volume of saline was given as a control. Tat-Beclin-1, a specific autophagy inducer, was administered by intraperitoneal injection at 24 and 48 hours post-MCAO. Infarction volume, mortality and neurological function were assessed at 72 hours after ischemic insult. Immunofluorescence and Western blotting were performed to determine the expression of autophagy-related proteins P62, LC3 and Beclin-1 in the penumbra area. No significant changes in mortality and physiological variables (heart rate, blood glucose levels and arterial blood gases) were observed between the different groups. However, MCAO resulted in enhanced conversion of LC3-I into LC3-II, P62 degradation, high levels of Beclin-1, a large area infarction (26.3±3.6%) and serious neurobehavioral deficits. GM1 (50 mg/kg) treatment significantly reduced the autophagy activation, neurobehavioral dysfunctions, and infarction volume (from 26.3% to 19.5%) without causing significant adverse side effects. However, this biological function could be abolished by Tat-Beclin-1. IN CONCLUSION: GM1 demonstrated safe and robust neuroprotective effects that are associated with the inhibition of autophagy following experimental stroke.

Tissue-Resident NK Cells Mediate Ischemic Kidney Injury and Are Not Depleted by Anti-Asialo-GM1 Antibody.

NK cells are innate lymphoid cells important for immune surveillance, identifying and responding to stress, infection, and/or transformation. Whereas conventional NK (cNK) cells circulate systemically, many NK cells reside in tissues where they appear to be poised to locally regulate tissue function. In the present study, we tested the contribution of tissue-resident NK (trNK) cells to tissue homeostasis by studying ischemic injury in the mouse kidney. Parabiosis experiments demonstrate that the kidney contains a significant fraction of trNK cells under homeostatic conditions. Kidney trNK cells developed independent of NFIL3 and T-bet, and they expressed a distinct cell surface phenotype as compared with cNK cells. Among these, trNK cells had reduced asialo-GM1 (AsGM1) expression relative to cNK cells, a phenotype observed in trNK cells across multiple organs and mouse strains. Strikingly, anti-AsGM1 Ab treatment, commonly used as an NK cell-depleting regimen, resulted in a robust and selective depletion of cNKs, leaving trNKs largely intact. Using this differential depletion, we tested the relative contribution of cNK and trNK cells in ischemic kidney injury. Whereas anti-NK1.1 Ab effectively depleted both trNK and cNK cells and protected against ischemic/reperfusion injury, anti-AsGM1 Ab preferentially depleted cNK cells and failed to protect against injury. These data demonstrate unanticipated specificity of anti-AsGM1 Ab depletion on NK cell subsets and reveal a new approach to study the contributions of cNK and trNK cells in vivo. In total, these data demonstrate that trNK cells play a key role in modulating local responses to ischemic tissue injury in the kidney and potentially other organs.

Impaired ganglioside metabolism in Huntington's disease and neuroprotective role of GM1.

Huntington's disease (HD) is a neurodegenerative disorder caused by the expansion of a polyglutamine stretch in the protein huntingtin (Htt). HD neurons are dysfunctional at multiple levels and have increased susceptibility to stress and apoptotic stimuli. We have discovered that synthesis of the ganglioside GM1 is reduced in fibroblasts from HD patients and in cell and animal models of HD, and that decreased GM1 levels contribute to heighten HD cell susceptibility to apoptosis. The apoptotic susceptibility is recapitulated through inhibition of ganglioside synthesis in wild-type striatal cells, suggesting that decreased GM1 levels might be one of the key events leading to HD pathogenesis and progression. Administration of GM1 restores ganglioside levels in HD cells and promotes activation of AKT and phosphorylation of mutant Htt, leading to decreased mutant Htt toxicity and increased survival of HD cells. Our data identify GM1 as a potential treatment for HD.

NK depletion results in increased CCL22 secretion and Treg levels in Lewis lung carcinoma via the accumulation of CCL22-secreting CD11b+CD11c+ cells.

Tumor-induced immune suppression involves the accumulation of suppressive infiltrates in the tumor microenvironment such as regulatory T-cells (Tregs). Previous studies demonstrated that NK-dependant increases in CCL22 secretion selectively recruit Tregs toward murine lungs bearing Lewis Lung Carcinoma (LLC). To extend the in vitro studies, the present studies utilized in vivo depletion of NK cells to ascertain the contribution of NK-derived CCL22 toward total CCL22 and subsequent Treg levels in both normal and LLC-bearing lungs. However, NK depletion had the unexpected effect of increasing both CCL22 secretion and Treg levels in the lungs of NK-depleted LLC-bearing mice. This was concurrent with an increase in tumor burden. Flow cytometry and a series of both immunomagnetic and FACS isolations were used to identify the CCL22-producing cellular fractions in LLC-bearing lungs. A novel CD11b(+)CD11c(+) cell population was identified that accumulates in large numbers in NK-depleted LLC-bearing lung tissue. These CD11b(+)CD11c(+) cells secreted large amounts of CCL22 that may overcompensate for the loss of NK-derived CCL22 in the lungs of NK-depleted LLC-bearing mice. Taken together, these data suggest that NK cells play both a positive and negative role in the regulation of CCL22 secretion and, in turn, the recruitment of Tregs toward LLC-bearing lungs.

L-NAME prevents GM1 ganglioside-induced vasodilation in the rat brain.

Monosialoganglioside (GM1) is a glycosphingolipid present in most cell membranes that displays antioxidant and neuroprotective properties. It has been recently described that GM1 induces vasodilation. However, the mechanisms underlying GM1-induced vasodilation were not evaluated to date. Therefore, in this study we investigated whether the nonspecific NOS inhibitor l-NAME prevents GM1-induced vasodilation in rats. The systemic injection of GM1 (50mg/kg, i.p.) increased the outer diameter of pial vessels by 50% in anesthetized animals at 30min, and this effect was fully prevented by the administration of the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME, 60mg/kg, i.p. 15min before GM1 injection). A 30min exposure of cerebral cortex slices to GM1 (100microM) increased the content of nitrite plus nitrate (NOx) by 50%. Addition of l-NAME (100microM) to the incubation medium fully prevented GM1-induced NOx increase. Conversely, a 60min exposure of slices to GM1 (100microM) decreased NOx content, revealing a biphasic effect of GM1. Our results suggest that NO plays an important role in the vasodilation induced by GM1.

NK but not CD1-restricted NKT cells facilitate systemic inflammation during polymicrobial intra-abdominal sepsis.

Evidence suggests that NK and NKT cells contribute to inflammation and mortality during septic shock caused by cecal ligation and puncture (CLP). However, the specific contributions of these cell types to the pathogenesis of CLP-induced septic shock have not been fully defined. The goal of the present study was to determine the mechanisms by which NK and NKT cells mediate the host response to CLP. Control, NK cell-deficient, and NKT cell-deficient mice underwent CLP. Survival, cytokine production, and bacterial clearance were measured. NK cell trafficking and interaction with myeloid cells was also studied. Results show that mice treated with anti-asialoGM1 (NK cell deficient) or anti-NK1.1 (NK/NKT cell deficient) show less systemic inflammation and have improved survival compared with IgG-treated controls. CD1 knockout mice (NKT cell deficient) did not demonstrate decreased cytokine production or improved survival compared with wild type mice. Trafficking studies show migration of NK cells from blood and spleen into the inflamed peritoneal cavity where they appear to facilitate the activation of peritoneal macrophages (F4-80(+)GR-1(-)) and F4-80(+)Gr-1(+) myeloid cells. These findings indicate that NK but not CD1-restricted NKT cells contribute to acute CLP-induced inflammation. NK cells appear to mediate their proinflammatory functions during septic shock, in part, by migration into the peritoneal cavity and amplification of the proinflammatory activities of specific myeloid cell populations. These findings provide new insights into the mechanisms used by NK cells to facilitate acute inflammation during septic shock.

Measurement of the binding of cholera toxin to GM1 gangliosides on solid supported lipid bilayer vesicles and inhibition by europium (III) chloride.

In this paper the immobilization of small unilamellar DMPC/GM1 lipid vesicles containing a water-soluble bodipy dye is described. The binding of the complete alphabeta toxin expressed by Vibrio cholerae to the attached vesicles was measured using Surface Plasmon Resonance (SPR) and a value of the dissociation constant K d obtained. Further measurements showed that the interaction of both the alphabeta-toxin and the beta-subunit alone resulted in the permeation of the lipid membrane, with release of a fluorophore contained within the vesicle being measured by combined SPR and Surface Plasmon enhanced Fluorescence Spectroscopy (SPFS). The leakage of dye through the membrane, measured by following the change in fluorescence, was fitted to a simple diffusion model. Finally, SPFS measurements of the effect of europium(III) chloride (EuCl 3) showed that cholera toxin binding and subsequent membrane permeation could be blocked by 1 micromol dm (-3) europium chloride. In view of the low oral toxicity of europium chloride, we speculate on the potential pharmaceutical applications of this molecule in the treatment of cholera infection.

Thematic review series: sphingolipids. Ganglioside GM3 suppresses the proangiogenic effects of vascular endothelial growth factor and ganglioside GD1a.

Gangliosides are sialic acid-containing glycosphingolipids that have long been associated with tumor malignancy and metastasis. Mounting evidence suggests that gangliosides also modulate tumor angiogenesis. Tumor cells shed gangliosides into the microenvironment, which produces both autocrine and paracrine effects on tumor cells and tumor-associated host cells. In this study, we show that the simple monosialoganglioside GM3 counteracts the proangiogenic effects of vascular endothelial growth factor (VEGF) and of the complex disialoganglioside GD1a. GM3 suppressed the action of VEGF and GD1a on the proliferation of human umbilical vein endothelial cells (HUVECs) and inhibited the migration of HUVECs toward VEGF as a chemoattractant. Enrichment of added GM3 in the HUVEC membrane also reduced the phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR-2) and downstream Akt. Moreover, GM3 reduced the proangiogenic effects of GD1a and growth factors in the in vivo Matrigel plug assay. Inhibition of GM3 biosynthesis with the glucosyl transferase inhibitor, N-butyldeoxynojirimycin (NB-DNJ), increased HUVEC proliferation and the phosphorylation of VEGFR-2 and Akt. The effects of NB-DNJ on HUVECs were reversed with the addition of GM3. We conclude that GM3 has antiangiogenic action and may possess therapeutic potential for reducing tumor angiogenesis.

Atorvastatin inhibits T cell activation through 3-hydroxy-3-methylglutaryl coenzyme A reductase without decreasing cholesterol synthesis.

The localization of the TCR and other signaling molecules in membrane rafts (MR) is essential for the activation of T lymphocytes. MR are stabilized by sphingolipids and cholesterol. Activation of T lymphocytes leads to the confluence of small MR and the formation of an immunological synapse that is essential for sustained activation and proliferation. In this study, we investigated the effect of statins on MR and T cell activation in superantigen-stimulated human PBMC. Atorvastatin significantly inhibited cellular activation and proliferation. The binding of cholera toxin B subunit to isolated MR and to whole cells was inhibited by low doses of statins. Statins reduce the association of critical signaling proteins such as Lck and linker of activation in T cells with MR in stimulated T cells. The expression of activation markers CD69 and CD25 was inhibited. Several statin-mediated mechanisms, such as a lower stimulation with MHC-II, an inhibition of costimulation by direct binding of statins to LFA-1, a reduced secretion of cytokines, or a depletion of cellular cholesterol pools, were excluded. Inhibition of protein prenylation had a similar effect on T cell proliferation, suggesting that a reduced protein prenylation might contribute to the statin-mediated inhibition of T cell activation. Statins induce both lower levels of low-density lipoprotein cholesterol and inhibition of T cell activation, which might contribute to an inhibition of atherosclerosis.

Maternal fumonisin exposure and risk for neural tube defects: mechanisms in an in vivo mouse model.

BACKGROUND: Fumonisin B1 (FB1) is a mycotoxin produced by the fungus Fusarium verticillioides, a common contaminant of corn worldwide. FB1 disrupts sphingolipid biosynthesis by inhibiting the enzyme ceramide synthase, resulting in an elevation of free sphingoid bases and depletion of downstream glycosphingolipids. A relationship between maternal ingestion of FB1-contaminated corn during early pregnancy and increased risk for neural tube defects (NTDs) has recently been proposed in human populations around the world where corn is a dietary staple. The current studies provide an in vivo mouse model of FB1 teratogenicity. METHODS: Pregnant LM/Bc mice were injected with increasing doses of FB1 on GD 7.5 and 8.5, and exposed fetuses were examined for malformations. Sphingolipid profiles and (3)H-folate concentrations were measured in maternal and fetal tissues. Immunohistochemical expression of the GPI-anchored folate receptor (Folbp1) and its association with the lipid raft component, ganglioside GM1, were characterized. Rescue experiments were performed with maternal folate supplementation or administration of gangliosides. RESULTS: Maternal FB1 administration (20 mg/kg of body weight) during early gestation resulted in 79% NTDs in exposed fetuses. Sphingolipid profiles were significantly altered in maternal and embryonic tissues following exposure, and (3)H-folate levels and immunohistochemical expression of Folbp1 were reduced. Maternal folate supplementation partially rescued the NTD phenotype, whereas GM1 significantly restored folate concentrations and afforded almost complete protection against FB1-induced NTDs. CONCLUSIONS: Maternal FB1 exposure altered sphingolipid metabolism and folate concentrations in LM/Bc mice, resulting in a dose-dependent increase in NTDs that could be prevented when adequate folate levels were maintained.

Expression of IL-27 in murine carcinoma cells produces antitumor effects and induces protective immunity in inoculated host animals.

A novel cytokine interleukin-27 (IL-27), composed of p28 and Epstein-Barr virus-induced gene 3 (EBI3), is produced from activated dendritic cells and is involved in an early phase of T-helper type I differentiation. We examined whether Colon 26 murine colon carcinoma cells that were retrovirally transduced with the p28-linked EBI3 gene (Colon 26/IL-27) could produce antitumor effects in inoculated mice. Although proliferation in vitro of Colon 26/IL-27 cells was not different from that of parent cells, syngeneic BALB/c mice rejected Colon 26/IL-27 tumors inoculated and subsequently acquired tumor-specific protective immunity. In contrast, mice inoculated with Colon 26 cells transduced with either the p28 or EBI3 gene developed tumors and survival of the mice remained the same as that of the mice inoculated with parent cells. Syngeneic nude mice developed Colon 26/IL-27 tumors, but the growth was retarded compared to that of parent tumors. Depletion of natural killer cells from nude mice with anti-asialo GM(1) antibody diminished the growth retardation of Colon 26/IL-27 tumors. Survival of severe combined immunodeficient mice that received subcutaneous inoculation of Colon 26/IL-27 cells was not different from that of the immunodeficient mice inoculated with parent cells. Interferon-gamma was produced from CD4(+) and CD8(+) T, and natural killer cells of the mice that rejected Colon 26/IL-27 tumors and cytotoxic activity against Colon 26 cells were also detected from the mice. These data collectively suggest that expressed IL-27 in tumors produces T cell-dependent and-independent antitumor effects and is a possible therapeutic strategy for cancer.

Beta2-microglobulin knockout mice treated with anti-asialoGM1 exhibit improved hemodynamics and cardiac contractile function during acute intra-abdominal sepsis.

We previously showed that beta2-microglobulin knockout mice treated with anti-asialoGM1 (beta2M/alphaAsGM1 mice) exhibit less hypothermia, reduced production of proinflammatory cytokines, less metabolic acidosis, and improved survival after cecal ligation and puncture (CLP) compared with wild-type mice. The present study was designed to assess hemodynamics and left ventricular contractility at 18 h after CLP. Arterial pressure was measured by carotid artery cannulation, and left ventricular pressure-volume loops were obtained by insertion of a 1.4-F conductance catheter into the left ventricle. Heart rate, stroke volume, and cardiac output were not significantly different between wild-type and beta2M/alphaAsGM1 mice after CLP. However, beta2M/alphaAsGM1 mice exhibited improved mean arterial pressure and systemic vascular resistance compared with wild-type mice. Myocardial function was also better preserved in beta2M/alphaAsGM1 mice as indicated by improved left ventricular pressure development over time, time-varying maximum elastance, endsystolic pressure-volume relationship, and preload recruitable stroke work. Overall, this study shows that cardiovascular collapse characterized by hypotension, myocardial depression, and low systemic vascular resistance occurs after CLP in wild-type mice. However, beta2M/alphaAsGM1 mice exhibit improved hemodynamics and cardiac contractile function after CLP that may account, in part, for our previously observed survival benefit.

Loss of hepatocyte co-operative activity after inhibition of ganglioside GM1 synthesis and shedding.

Pretreatment of hepatocyte cultures with 1 microM d-l-threo-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol-HCL (PPPP) for 24 h decreased the ganglioside GM1 content of the cells by approximately 50% and that of the conditioned medium by 90%. No rhythm in the rate of protein synthesis was detected in dense cultures pretreated with PPPP, but was observed in control dense cultures. Conditioned medium from control dense cultures induced synchrony in sparse cultures, which were non-synchronous in their own medium. In contrast, conditioned medium from dense cultures pretreated with PPPP did not synchronize sparse cultures. Since protein synthesis rhythm is a marker of cell synchronization, i.e. their co-operative activity, then non-oscillatory behavior means loss of cell co-operation. The protein synthesis rhythm was restored 24 h after hepatocytes were transferred to PPPP-free medium. Restoration was more rapid when 0.9 microM gangliosides (standard mixture from bovine brain) were added to the medium just after the withdrawal of PPPP. These novel results concerning the loss of rhythm of protein synthesis in low GM1 ganglioside medium support the conclusion that ganglioside is implicated in the regulation of cell co-operative activity.

Beta 2 microglobulin knockout mice are resistant to lethal intraabdominal sepsis.

beta 2 microglobulin knockout (beta2M-/-) mice lack CD8+ T and natural killer T cells. We hypothesized that beta 2M-/- mice are resistant to lethal intraabdominal sepsis. To test this hypothesis, mortality, cytokine production, and physiologic function were assessed in beta 2M-/- mice during sepsis caused by cecal ligation and puncture (CLP). beta 2M-/- mice survived significantly longer than wild-type mice after CLP but ultimately exhibited 100% mortality. Treatment of beta 2M-/- mice with anti-asialoGM1 to deplete natural killer cells conferred greater than 70% long-term survival. Compared with wild-type mice, beta 2M-/- mice treated with anti-asialoGM1 produced decreased amounts of proinflammatory cytokines and did not exhibit hypothermia or metabolic acidosis after CLP. Adoptive transfer of CD8+ T and natural killer cells into beta 2M-/- mice treated with anti-asialoGM1 re-established CLP-induced mortality. CD8 knockout mice treated with anti-asialoGM1, which are specifically deficient in CD8+ T and natural killer cells, exhibited 40% long-term survival after CLP. Furthermore, treatment of wild-type mice with antibodies to CD8 and asialoGM1 conferred a significant survival benefit compared with wild-type mice treated with nonspecific IgG. These findings demonstrate that beta 2M-/- mice treated with anti-asialoGM1 are resistant to CLP-induced mortality and that depletion of CD8+ T and natural killer cells largely accounts for the survival benefit observed in these mice.

Solution and crystallographic studies of branched multivalent ligands that inhibit the receptor-binding of cholera toxin.

The structure-based design of multivalent ligands offers an attractive strategy toward high affinity protein inhibitors. The spatial arrangement of the receptor-binding sites of cholera toxin, the causative agent of the severe diarrheal disease cholera and a member of the AB(5) bacterial toxin family, provides the opportunity of designing branched multivalent ligands with 5-fold symmetry. Our modular synthesis enabled the construction of a family of complex ligands with five flexible arms each ending with a bivalent ligand. The largest of these ligands has a molecular weight of 10.6 kDa. These ligands are capable of simultaneously binding to two toxin B pentamer molecules with high affinity, thus blocking the receptor-binding process of cholera toxin. A more than million-fold improvement over the monovalent ligand in inhibitory power was achieved with the best branched decavalent ligand. This is better than the improvement observed earlier for the corresponding nonbranched pentavalent ligand. Dynamic light scattering studies demonstrate the formation of concentration-dependent unique 1:1 and 1:2 ligand/toxin complexes in solution with no sign of nonspecific aggregation. This is in complete agreement with a crystal structure of the branched multivalent ligand/toxin B pentamer complex solved at 1.45 A resolution that shows the specific 1:2 ligand/toxin complex formation in the solid state. These results reiterate the power of the structure-based design of multivalent protein ligands as a general strategy for achieving high affinity and potent inhibition.