Shlomo Elias

Complex Locking Rather Than Complete Cessation of Neuronal Activity in the Globus Pallidus of a 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Treated Primate in Response to Pallidal Microstimulation

High-frequency stimulation of the globus pallidus (GP) has emerged as a successful tool for treating Parkinsons disease and other motor disorders. However, the mechanism governing its therapeutic effect is still under debate. To shed light on the basic mechanism of deep brain stimulation (DBS), we performed microstimulation in the GP of a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkey while recording with other microelectrodes in the same nucleus. We used robust methods to reduce the stimulus artifact, and 600-3000 repetitions of a single stimulus and of high-frequency short trains (10-40 stimuli), enabling high temporal resolution analysis of neural responses. Low-frequency stimulation yielded a typical three-stage response: short-term (2-3 msec duration) activity, followed by mid-term (15-25 msec) inhibition, and occasionally longer-term (30-40 msec) excitation. Trains of high-frequency stimuli elicited complex locking of the response to the stimuli in most neurons. The locking displayed a stereotypic temporal structure consisting of three short-duration (1-2 msec) phases: an initial (mean latency = 2.9 msec) excitation followed by an inhibition (4.6 msec) and a second excitation (6.3 msec). The change in the mean firing rate was mixed; the majority of the neurons displayed partial inhibition during the stimulus train. Slow inhibitory and excitatory multiphase changes in the firing rate were observed after the stimulus trains. The activity of neurons recorded simultaneously displayed rate correlations but no spike-to-spike correlations. Our results suggest that the effect of DBS on the GP is not complete inhibition but rather a complex reshaping of the temporal structure of the neuronal activity within that nucleus.

Statistical Properties of Pauses of the High-Frequency Discharge Neurons in the External Segment of the Globus Pallidus

The neurons of many basal ganglia nuclei, including the external and internal globus pallidus (GPe and GPi, respectively) and the substantia nigra pars reticulata (SNr) are characterized by their high-frequency (50–100 spikes/s) tonic discharge (HFD). However, the high firing rate of GPe neurons is interrupted by long pauses. We studied the extracellularly recorded spiking activity of 212 well-isolated HFD GPe and 52 GPi/SNr neurons from five monkeys during different states of behavioral activity. An algorithm that maximizes the surprise function was used to detect pauses and pauser cells (“pausers”). Only 6% of the GPi/SNr neurons versus as many as 56% of the GPe neurons were classified as pausers. The GPe average pause duration equals 0.62 s. The interpause intervals follow a Poissonian distribution with a frequency of 13 pauses/minute. No linear relationship was found between pause parameters (duration or frequency) and the firing rate of the cell. Pauses were preceded by various changes in firing rate but not dominantly by a decrease. The average amplitude and duration of the spike waveform was modulated only after the pause but not before it. Pauses of pairs of cells that were recorded simultaneously were not correlated. The probability of GPe cells to pause spontaneously was extremely variable among monkeys (30–90%) and inversely related to the degree of the monkeys motor activity. These findings suggest that spontaneous GPe pauses are related to low-arousal periods and are generated by a process that is independent of the discharge properties of the cells.

Computational physiology of the basal ganglia in Parkinson's disease.

The normal activity of basal ganglia neurons is characterized by Poisson-like (random) firing patterns. Correlations between neurons of the same structure are weak or non-existent. By contrast, synchronous oscillations are commonly found in the basal ganglia of human patients and animal models of Parkinsons disease. The frequency of these oscillations is often similar to that of the parkinsonian tremor, but their role in generating the tremor or other parkinsonian symptoms is still under debate. The tremor is intermittent and does not appear in all human patients. Similarly, primate models tend to develop tremor as a function of species of monkey. African green (vervet) monkeys usually demonstrate a high-amplitude, low-frequency (4-7Hz) tremor beyond their akinesia and bradykinesia, whereas macaques tend to be akinetic rigid and rarely demonstrate a low-amplitude high-frequency (10-12Hz) action-postural tremor. We took advantage of this fact and studied the appearance of the synchronicity and oscillations in six monkeys, three vervets and three macaques, before and after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) systemic treatment and induction of parkinsonism. Multiple extracellular recordings were conducted in the primary motor cortex of two monkeys and in the globus pallidus (GP) of all six monkeys. All the monkeys became akinetic and bradykinetic as a result of the MPTP treatment, but only vervets demonstrated prolonged episodes of low-frequency (4-6Hz) tremor, whereas macaques were non-tremulous. The GP population exhibited approximately 5Hz oscillatory activity in all six monkeys, whereas approximately 10Hz neural oscillations were only detected in the tremulous monkeys. The activity of the cortical neurons became strongly oscillatory at approximately 10Hz in one of these monkeys, but not the other, although both were tremulous and exhibited comparable pallidal oscillatory activity. Finally, synchronous oscillations, when present, were centred around the higher frequencies of oscillations. These findings suggest that there is a correlation between high-frequency GP neural oscillations and tremor. Furthermore, these pallidal 10Hz oscillations are probably transferred to the periphery through cortical and brainstem pathways.

Physiology and pathophysiology of the basal ganglia—thalamo—cortical networks

Low-frequency resting tremor is one of the cardinal signs of Parkinsons disease (PD) and occurs also in some of its animal models. Current physiological studies and models of the basal ganglia indicate that changes of discharge pattern and synchronization of basal ganglia neurons rather than modification in their discharge rate are crucial to the pathophysiology of PD. However, parkinsonian tremor is not strictly correlated with the synchronous oscillations in the basal ganglia networks. We therefore suggest that abnormal basal ganglia output enforces abnormal thalamo-cortical processing leading to akinesia, the main negative symptom of Parkinsons disease. The parkinsonian positive motor signs, such as tremor and rigidity, most likely evolve as a downstream compensatory mechanism.

The viral KSHV chemokine vMIP-II inhibits the migration of Naive and activated human NK cells by antagonizing two distinct chemokine receptors.

Natural killer (NK) cells are innate immune cells able to rapidly kill virus-infected and tumor cells. Two NK cell populations are found in the blood; the majority (90%) expresses the CD16 receptor and also express the CD56 protein in intermediate levels (CD56Dim CD16Pos) while the remaining 10% are CD16 negative and express CD56 in high levels (CD56Bright CD16Neg). NK cells also reside in some tissues and traffic to various infected organs through the usage of different chemokines and chemokine receptors. Kaposis sarcoma-associated herpesvirus (KSHV) is a human virus that has developed numerous sophisticated and versatile strategies to escape the attack of immune cells such as NK cells. Here, we investigate whether the KSHV derived cytokine (vIL-6) and chemokines (vMIP-I, vMIP-II, vMIP-III) affect NK cell activity. Using transwell migration assays, KSHV infected cells, as well as fusion and recombinant proteins, we show that out of the four cytokine/chemokines encoded by KSHV, vMIP-II is the only one that binds to the majority of NK cells, affecting their migration. We demonstrate that vMIP-II binds to two different receptors, CX3CR1 and CCR5, expressed by naïve CD56Dim CD16Pos NK cells and activated NK cells, respectively. Furthermore, we show that the binding of vMIP-II to CX3CR1 and CCR5 blocks the binding of the natural ligands of these receptors, Fractalkine (Fck) and RANTES, respectively. Finally, we show that vMIP-II inhibits the migration of naïve and activated NK cells towards Fck and RANTES. Thus, we present here a novel mechanism in which KSHV uses a unique protein that antagonizes the activity of two distinct chemokine receptors to inhibit the migration of naïve and activated NK cells.

Immune evasion by oncogenic proteins of acute myeloid leukemia.

PML-RARA and AML1-ETO are important oncogenic fusion proteins that play a central role in transformation to acute myeloid leukemia (AML). Whether these fusion proteins render the tumor cells with immune evasion properties is unknown. Here we show that both oncogenic proteins specifically downregulate the expression of CD48, a ligand of the natural killer (NK) cell activating receptor 2B4, thereby leading to decreased killing by NK cells. We demonstrate that this process is histone deacetylase (HDAC)-dependent, that it is mediated through the downregulation of CD48 messenger RNA, and that treatment with HDAC inhibitors (HDACi) restores the expression of CD48. Furthermore, by using chromatin immunoprecepitation (ChIP) experiments, we show that AML1-ETO directly interacts with CD48. Finally, we show that AML patients who are carrying these specific translocations have low expression of CD48.

Balance of Increases and Decreases in Firing Rate of the Spontaneous Activity of Basal Ganglia High-Frequency Discharge Neurons

Most neurons in the external and internal segments of the globus pallidus and the substantia nigra pars reticulata (GPe, GPi, and SNr) are characterized by a high-frequency discharge (HFD) rate (50-80 Hz) that, in most GPe neurons, is also interrupted by pauses. Almost all (approximately 90%) of the synaptic inputs to these HFD neurons are GABAergic and inhibitory. Nevertheless, their responses to behavioral events are usually dominated by increases in discharge rate. Additionally, there are no reports of prolonged bursts in the spontaneous activity of these cells that could reflect their disinhibition by GPe pauses. We recorded the spontaneous activity of 385 GPe, GPi, and SNr HFD neurons during a quiet-wakeful state from two monkeys. We developed three complementary methods to quantify the balance of increases and decreases in the spontaneous discharge of HFD neurons and validated them by simulations. Unlike the behavioral evoked responses, the spontaneous activity of pallidal and SNr neurons is not dominated by increases. Moreover, the activity of basal ganglia neurons does not include bursts that could reflect disinhibition by the spontaneous pauses of GPe neurons. These findings suggest that the discharge increase/decrease balance during a quiet-wakeful state better reflects the inhibitory input of the HFD basal ganglia neurons than during responses to behavioral events; however, the GPe pauses are not echoed by comparable bursts either in the GPe or in the output nuclei. Changes in the excitatory drive of these structures (e.g., during behavioral activity) thus may lead to a remarkable change in this balance.

Neighboring pallidal neurons do not exhibit more synchronous oscillations than remote ones in the MPTP primate model of Parkinson's disease

In the healthy primate, neurons of the external and internal segments of the globus pallidus (GP) present a primarily irregular firing pattern, and a negligible level of synchrony is observed between pairs of neurons. This holds even for neighboring cells, despite their higher probability to receive common inputs and to innervate each other via lateral connectivity. In the Parkinsonian primate, this changes drastically, and many pairs of GP cells show synchronous oscillations. To address the relation between distance and synchrony in the Parkinsonian state, we compared the synchrony of discharge of close pairs of neurons, recorded by the same electrode, with remote pairs, recorded by different ones. However, spike trains of neighboring cells recorded by the same extracellular electrode exhibit the shadowing effect; i.e., lack of detection of spikes that occur within a few milliseconds of each other. Here, we demonstrate that the shadowing artifact can both induce apparent correlations between non-correlated neurons, as well as conceal existing correlations between neighboring ones. We therefore introduced artificial shadowing in the remote pairs, similar to the effect we observed in the close ones. After the artificial shadowing, neighboring cells did not show a higher tendency to oscillate synchronously than remote ones. On the contrary, the average percentage (over all sessions) of artificially shadowed remote pairs exhibiting synchronous oscillations was 35.4% compared to 17.2% in the close ones. Similar trend was found when the unshadowed remote pairs were separated according to the estimated distance between electrode tips: 29.9% of pairs at approximate distance of less than 750 μm were significantly synchronized, in comparison with 28.5% of the pairs whose distance was more than 750 μm. We conclude that the synchronous oscillations in the GP of MPTP treated primates are homogenously distributed.

Enteroviral infection in patients treated with rituximab for non-Hodgkin lymphoma: a case series and review of the literature

In recent years, anti‐CD20 antibodies have been increasingly used to treat lymphoproliferative and immune disorders. Chronic viral infections are infrequently reported in patients receiving these therapies. Enteroviral infection can cause life‐threatening meningoencephalitis and other systemic chronic syndromes in immune deficient patients. We describe the clinical courses and outcomes of 6 patients from 2 tertiary care institutions who developed chronic enteroviral infection with neurological manifestations, after combined chemoimmunotherapy with rituximab for B‐cell lymphoma. We review the literature that includes 10 sporadic reported cases of chronic enteroviral meningoencephalitis attributed to rituximab therapy. It is a rare disease, and its diagnosis is often elusive. We propose that low immunoglobulin G levels are the main risk factor for developing chronic enteroviral infection and emphasize the need for a high index of suspicion, early diagnosis, and intervention in this iatrogenic and potentially fatal complication.

Obinutuzumab activates FcγRI more potently than other anti-CD20 antibodies in chronic lymphocytic leukemia (CLL)

ABSTRACT Treatment with monoclonal antibodies has revolutionized clinical medicine, especially in the fields of cancer and immunology. One of the oldest antibodies, which is widely used for the treatment of lymphomas and autoimmune diseases, is the anti-CD20 antibody rituximab. In recent years, new antibodies against CD20 have been developed including ofatumumab and obinutuzumab. An important mechanism of action of therapeutic monoclonal antibodies is activation of immune cells via Fc receptors (FcγRs). However, surprisingly, little is known about triggering of FcγRs by different therapeutic antibodies in general and anti-CD20 antibodies in particular. Here we establish a reporter assay to assess whether a particular antibody activates a certain Fc receptor. Using this assay we corroborated previous reports demonstrating obinutuzumabs ability to highly activate FcγRIIIa (CD16a). Importantly, we discovered that obinutuzumab also activates FcγRI (CD64) significantly more than rituximab and ofatumumab in response to chronic lymphocytic leukemia (CLL) cells obtained from patients. Mechanistically we show that this is due to the lack of FcγRIIb-mediated internalization of obinutuzumab following binding to CD20. Moreover, we show that obinutuzumab induces increased phagocytosis by primary macrophages in an FcγRI-dependent manner. Beyond the discovery of a new mechanism of obinutuzumab activity, the reporter assay can be applied to other therapeutic antibodies and may assist in developing antibodies with improved immunological properties.