Insights into interoceptive and emotional processing: Lessons from studies on insular HD-tDCS.

Interoception, the processing of internal bodily signals, is proposed as the fundamental mechanism underlying emotional experiences. Interoceptive and emotional processing appear distorted in psychiatric disorders. However, our understanding of the neural structures involved in both processes remains limited. To explore the feasibility of enhancing interoception and emotion, we conducted two studies using high-definition transcranial direct current stimulation (HD-tDCS) applied to the right anterior insula. In study one, we compared the effects of anodal HD-tDCS and sham tDCS on interoceptive abilities (sensibility, confidence, accuracy, emotional evaluation) in 52 healthy subjects. Study two additionally included physical activation through ergometer cycling at the beginning of HD-tDCS and examined changes in interoceptive and emotional processing in 39 healthy adults. In both studies, HD-tDCS was applied in a single-blind cross-over online design with two separate sessions. Study one yielded no significant effects of HD-tDCS on interoceptive dimensions. In study two, significant improvements in interoceptive sensibility and confidence were observed over time with physical preactivation, while no differential effects were found between sham and insula stimulation. The expected enhancement of interoceptive and emotional processing following insula stimulation was not observed. We conclude that HD-tDCS targeting the insula does not consistently increase interoceptive or emotional variables. The observed increase in interoceptive sensibility may be attributed to the activation of the interoceptive network through physical activity or training effects. Future research on HD-tDCS involving interoceptive network structures could benefit from protocols targeting larger regions within the network, rather than focusing solely on insula stimulation.

Enhancing Interoceptive Abilities and Emotional Processing: Effects of HD-tDCS.

BACKGROUND: Interoception, the processing and integration of bodily signals, is crucial for emotional experiences and overall well-being. The interoceptive network, including the somatosensory cortices, has been recognized for its role in interoceptive and emotional processing. High-definition transcranial, direct-current stimulation (HD-tDCS) has been demonstrated to modulate brain activity in the primary somatosensory cortex (S1). Based on those findings, we hypothesized that anodal HD-tDCS over the right S1 would enhance interoceptive abilities and heighten emotional perception. METHODS: Thirty-six healthy adults participated in two sessions separated by at least one week. A 20-min HD-tDCS stimulation (2 mA), and a sham stimulation, were applied in randomized order. Both conditions involved pre-tDCS physical activation by ergometer cycling. Interoceptive abilities were assessed before and after both sessions using a heartbeat-perception and respiratory-load task. Emotional perception was measured using four matched international affective picture system (IAPS) picture sets presented randomly. RESULTS: Active HD-tDCS did not significantly improve interoceptive accuracy, interoceptive emotion evaluation, or interoceptive sensibility. However, a notable increase in cardiac interoceptive awareness was observed after active HD-tDCS. The expected enhancement of emotional processing was not observed. CONCLUSIONS: This study represents the first attempt to modulate interoceptive and emotional processing using HD-tDCS over S1. Although consistent enhancement was not observed, our findings provide insights into the modulation of interoceptive and emotional processes with HD-tDCS, suggesting avenues for further research. Further studies should consider the nuanced effects of stimulation techniques and the complex interplay between interoception and emotion.

Processing of food stimuli in anorexia nervosa: An ERP-study comparing adolescents and adults.

BACKGROUND: Anorexia nervosa (AN) is associated with altered processing of disorder-relevant stimuli. Event-related potentials (ERP) - such as the Late Positive Potential (LPP) - give information about the underlying mechanisms of central nervous stimulus processing. METHODS: Patients with AN (22 adolescents, 23 adults) and healthy controls (HCs; 17 adolescents, 24 adults) were included. Neutral, low, and high calorie food-images were rated for valence and arousal; EEG activity was recorded and LPPs (early: 350-700 ms; late: 800-1200 ms) were extracted. Effects of patient status, age group, and stimulus category were analyzed via mixed 2 × 2 × 3-AN(C)OVAs. RESULTS: Patients with AN rated high calorie stimuli lower in valence and higher in arousal than HCs. Controlling for hunger, food stimuli elicited higher early LPPs than neutral ones in patients and HCs. For the late LPP, patients with AN showed larger amplitudes. CONCLUSION: Results suggest a highly automatic attentional bias towards low-calorie foods. Patients with AN seem to have more intense cognitive processing independent of stimulus material. More research is needed to validate and clarify differences between early and late LPP measures as well as the operationalization and relevance of hunger status.

Interoceptive abilities impairment correlates with emotional eating and taste abnormalities in children with overweight and obesity.

Weight problems in children are associated with emotional eating, which has been linked to interoceptive abilities. Previous research also shows altered olfactory and gustatory perception in children with obesity and overweight. Therefore, we aimed to investigate the connection of alterations in olfactory and gustatory perception to interoceptive abilities and emotional eating among children with obesity and overweight. 23 children with overweight and obesity and age-matched controls with normal weight (12-16 years old) underwent olfactory and gustatory testing. Interoceptive abilities were assessed, focusing on interoceptive accuracy and interoceptive sensibility. Children with overweight and obesity showed significantly higher accuracy for detection of sweet taste, but descriptively lower accuracy for all other taste qualities compared to normal weight children. We found no changes in olfactory abilities in children with overweight and obesity. Emotional eating scores were elevated for children with overweight and obesity, and interoceptive accuracy scores were significantly lower. In both groups, interoceptive accuracy was inversely correlated with emotional eating. Our results support prior findings of altered gustatory abilities in children with overweight and obesity. The observed link between impaired interoceptive processes and heightened emotional eating in this group implies that interventions for overweight in children could benefit from targeting interoceptive abilities. This study provides meaningful grounds for further investigations into the roles of taste, emotional eating, and interoceptive abilities for overweight in children and adolescents.

Elevated EEG heartbeat-evoked potentials in adolescents with more ADHD symptoms.

INTRODUCTION: Symptoms of attention deficit hyperactivity disorder (ADHD) are associated with a variety of mental abnormalities, but little is known about the perception and processing of internal signals, i.e., interoception, in individuals with ADHD symptoms. This study aimed to investigate the association between ADHD symptoms and the heartbeat-evoked potential (HEP), known as a neural correlate of automatic interoceptive processing of cardiac signals, in adolescents. METHODS: HEPs of 47 healthy adolescent participants (53.2 % female) with a mean age of 14.29 years were measured during an emotional face recognition task. In addition, participants completed a self-report screening for ADHD symptoms. RESULTS: ADHD symptoms were positively related to the HEP activity during the task in three of eight EEG sectors in the left hemisphere, as well as in all sectors in the right hemisphere. DISCUSSION: This study is the first to demonstrate preliminary a relationship between the strength of HEP activity and ADHD symptoms in awake subjects. This finding of higher HEP amplitudes in subjects with more ADHD symptoms can be interpreted in terms of (i) increased arousal, (ii) altered neural processing of internal processes in an emotion-relevant task, and (iii) a misaligned precision-weighting process of task-irrelevant stimuli according to the predictive coding framework. These different interpretations could be reflected by previous studies showing heterogeneity of psychological deficits in individuals with ADHD symptoms. However, the generalizability to patients with diagnosed ADHD is limited due to the measurement tool for ADHD symptoms and the sample characteristics.

Interaction Between Sex and Cardiac Interoceptive Accuracy in Measures of Induced Pain.

Pain perception is influenced by several factors, and among them, affect, sex, and perception of bodily signals are assumed to play a prominent role. The aim of the present study is to explore how sex, cardiac interoceptive accuracy, and the interaction of the latter two influence the perception of experimentally induced pain. We investigated a large sample of young adults (n = 159, 50.9% female, age: 23.45, SD = 3.767), assessing current positive and negative affective state with the Positive and Negative Affect Schedule (both involved as control variables), cardiac interoceptive accuracy with the mental heartbeat tracking task, and pain sensitivity with electrical stimulation on the back of the dominant hand, applying a repeated-measures staircase protocol. Males showed a significantly higher pain threshold and tolerance level than females, whereas cardiac interoceptive accuracy was not associated with pain sensitivity. The impact of sex × cardiac interoceptive accuracy interaction was significant for pain threshold only, while pain tolerance was predicted only by sex. According to these findings, the associations between pain sensitivity, cardiac IAc, and sex might be more complicated than it was supposed in previous studies. Interactions between factors impacting pain perception appear worthy of further investigation.

Concentrations of EpCAM ectodomain as found in sera of cancer patients do not significantly impact redirected lysis and T-cell activation by EpCAM/CD3-bispecific BiTE antibody MT110.

Ectodomains of target antigens for antibody-based therapies can be shed from the target cell surface and found in sera of patients. Shed ectodomains of therapeutic targets not only pose the risk of sequestering therapeutic antibodies but, in a multimeric form, of triggering T cell activation by bispecific antibodies binding to CD3 on T cells. Recently, epithelial cell adhesion molecule (EpCAM) has been shown to be activated by release of its ectodomain, called EpEX. Here, we show that only very low amounts of EpEX are detectable in sera of cancer patients. Among 100 cancer patient samples tested, only 17 (17%) showed serum levels of EpEX in excess of 0.05 ng/ml with highest EpEX concentrations of 5.29, 1.37 and 0.52 ng/ml. A recombinant form of human EpEX (recEpEX) was produced to assess its possible effect on redirected lysis and T cell activation by EpCAM/CD3-bispecific BiTE antibody MT110, currently being tested in patients with solid tumor malignancies. RecEpEX had a very minor effect on redirected lysis by MT110 with an approximate IC 50 value of 3,000 ng/ml, which is a concentration close to three orders of magnitude higher than the highest EpEX concentration found in cancer patients. Concentrations of 30 ng/ml EpEX in combination with 250 ng/ml MT110 were minimally required to induce a detectable activation of CD4 (+) and CD8 (+) T cells. We conclude that soluble EpEX in sera of cancer patients is unlikely to pose an issue for the efficacy or safety of MT110, and perhaps other antibodies binding to N-terminal epitopes of EpCAM.

Therapeutic window of MuS110, a single-chain antibody construct bispecific for murine EpCAM and murine CD3.

EpCAM (CD326) is one of the most frequently and highly expressed tumor-associated antigens known and recently has also been found on cancer stem cells derived from human breast, colon, prostate, and pancreas tumors. However, like many other tumor-associated antigens used for antibody-based immunotherapeutic approaches, EpCAM is expressed on normal tissues including epithelia of pancreas, colon, lung, bile ducts, and breast. To assess the therapeutic window of an EpCAM/CD3-bispecific single-chain antibody construct of the bispecific T-cell engager (BiTE) class, we constructed murine surrogate of MT110 (muS110) from single-chain antibodies specific for murine EpCAM and CD3 antigens. Immunhistochemical analysis showed that, with minor differences, the expression of EpCAM protein on a large variety of tissues from man and mouse was similar with respect to distribution and level. MuS110 exhibited significant antitumor activity at as low as 5 microg/kg in both syngeneic 4T1 orthotopic breast cancer and CT-26 lung cancer mouse models. Dosing of muS110 for several weeks up to 400 microg/kg by intraanimal dose escalation was still tolerated, indicating existence of a significant therapeutic window for an EpCAM-specific BiTE antibody in mice. MuS110 was found to have similar in vitro characteristics and in vivo antitumor activity as MT110, a human EpCAM/human CD3-bispecific BiTE antibody that currently is in formal preclinical development.

Exchanging human Fcgamma1 with murine Fcgamma2a highly potentiates anti-tumor activity of anti-EpCAM antibody adecatumumab in a syngeneic mouse lung metastasis model.

An important mode of action shared by human IgG1 antibody therapies is antibody-dependent cellular cytotoxicity (ADCC). ADCC relies on the interaction of the antibody's Fc portion with Fc-gama receptors (FcgammaR) on immune effector cells. The anti-tumor activity of human IgG1 antibodies is frequently assessed in mouse models. Binding of human IgG1 to murine FcgammaRs is however of reduced affinity. We here show that ADCC of adecatumumab (MT201), a fully human IgG1 antibody specific for epithelial cell adhesion molecule (EpCAM/CD326), is drastically lower if human peripheral blood mononuclear cells are replaced by murine splenocytes as effector cells. When the variable domains of adecatumumab were genetically fused to a murine IgG2a backbone (yielding mu-adecatumumab), ADCC with murine effector cells was much improved, but at the same time significantly reduced with human effector cells. The serum half-lives of adecatumumab and mu-adecatumumab were determined in mice and dosing schedules established that gave similar serum trough levels during a 4-week antibody treatment. The anti-tumor activities of adecatumumab and mu-adecatumumab were then compared side-by-side in a lung metastasis mouse model established with a syngeneic B16 melanoma line expressing human EpCAM at physiologically relevant levels. Treatment of mice with mu-adecatumumab led to an almost complete prevention of lung metastases, while the human version of the antibody was much less active. This shows that adecatumumab has high anti-tumor activity when tested in a form that is better compatible with the species' immune system. Moreover, our data suggest to routinely compare in mouse models human IgG1 and murine IgG2a versions of antibodies to properly assess the contribution of ADCC to overall anti-tumor activity.

T-cell activation and B-cell depletion in chimpanzees treated with a bispecific anti-CD19/anti-CD3 single-chain antibody construct.

BscCD19xCD3 is a bispecific single-chain antibody construct with exceptional cytotoxic potency in vitro and in vivo. Here, we have investigated the biological activity of bscCD19xCD3 in chimpanzee, the only animal species identified in which bscCD19xCD3 showed bispecific binding, redirected B-cell lysis and cytokine production comparable to human cells. Pharmacokinetic analysis following 2-h intravenous infusion of 0.06, 0.1 or 0.12 mug/kg of bscCD19xCD3 as part of a dose escalation study in a single female chimpanzee revealed a half-life of approximately 2 h and elimination of the bispecific antibody from circulation within approximately 8 h after the end of infusion. This short exposure to bscCD19xCD3 elicited a transient increase in serum levels of IFNgamma, IL-6, IL-2, soluble CD25, and transiently upregulated expression of CD69 and MHC class II on CD8-positive cells. Cytokine release and upregulation of T-cell activation markers were not observed with vehicle controls. A multiple-dose study using 5 weekly doses of 0.1 mug/kg in two animals also showed transient cytokine release and an activation of peripheral T cells with a first-dose effect, accompanied by a transient lymphopenia. While oscillations of T-cell counts were relatively even during repeated treatments, the amplitudes of peripheral B cells declined with every infusion, which was not observed in a vehicle control animal. Our data show that bscCD19xCD3 can be safely administered to chimpanzees at dose levels that cause fully reversible T-cell activation and, despite a very short exposure time, cumulative loss of peripheral B lymphocytes. A clinical trial testing prolonged administration of bscCD19xCD3 (MT103) for improving efficacy is currently ongoing.

High concentrations of therapeutic IgG1 antibodies are needed to compensate for inhibition of antibody-dependent cellular cytotoxicity by excess endogenous immunoglobulin G.

A common feature of human IgG1 antibodies used for cancer treatment is that their anti-tumour efficacy requires high serum trough levels and continued therapy for several months. Treatment cycles, thereby, consume several grams of IgG1 translating into significant drug needs and costs. The basis for the low in vivo efficacy, which is in contrast to high in vitro antibody-dependent cellular cytotoxicity (ADCC), is not well understood. Here, we have explored factors contributing to this discrepancy using adecatumumab (MT201), a fully human monoclonal IgG1 against epithelial cell adhesion molecule (Ep-CAM) and trastuzumab (Herceptin), a humanized IgG1 with specificity for the human epithelial growth factor receptor type 2 (HER-2) antigen. We found that physiological levels of human sera strongly inhibited ADCC of both IgG1 antibodies. Effects showed some dependence on the density of Ep-CAM and HER-2 targets, the tumour cell line tested and on effector cell and serum donors. Removal of IgG by affinity chromatography abolished the inhibitory effect of a serum pool. Inhibition of ADCC was fully restored by adding back the IgG fraction or by an equal amount of IgG from a commercial source. We further demonstrate that CD56-positive lymphocytes within human PBMC contributed >90% to ADCC and that normal serum levels of IgG effectively competed for in vitro binding of an IgG1 antibody to low-affinity Fcgamma receptor type III (CD16), as is present on natural killer (NK) cells. Competition of serum IgG for binding of therapeutic IgG1 to NK cell may be one important reason why high antibody doses are required in the clinic for treatment of cancer by an ADCC-based mechanism.

Potent inhibition of local and disseminated tumor growth in immunocompetent mouse models by a bispecific antibody construct specific for Murine CD3.

Bispecific single-chain antibody constructs specific for human CD3 have been extensively studied for antitumor activity in human xenograft models using severe combined immunodeficient mice supplemented with human T cells. High efficacy at low effector-to-target ratios, independence of T cell costimuli and a potent activation of previously unstimulated polyclonal T cells were identified as hallmarks of this class of bispecific antibodies. Here we studied a bispecific single-chain antibody construct (referred to as 'bispecific T cell engager', BiTE) in an immunocompetent mouse model. This was possible by the use of a murine CD3-specific BiTE, and a syngeneic melanoma cell line (B16F10) expressing the human Ep-CAM target. The murine CD3-specific BiTE, called 2C11x4-7 prevented in a dose-dependent fashion the outgrowth of subcutaneously growing B16/Ep-CAM tumors with daily i.v. injections of 5 or 50 microg BiTE which was most effective. Treatment with 2C11x4-7 was effective even when it was started 10 days after tumor cell inoculation but delayed treatments showed a reduction in the number of cured animals. 2C11x4-7 was also highly active in a lung tumor colony model. When treatment was started on the day of intravenous tumor cell injection, seven out of eight animals stayed free of lung tumors, and three out of eight animals when treatment was started on day 5. Our study shows that BiTEs also have a high antitumor activity in immunocompetent mice and that there is no obvious need for costimulation of T cells by secondary agents.

In vitro and in vivo activity of MT201, a fully human monoclonal antibody for pancarcinoma treatment.

In our study, a novel, fully human, recombinant monoclonal antibody of the IgG1 isotype, called MT201, was characterized for its binding properties, complement-dependent (CDC) and antibody-dependent cellular cytotoxicity (ADCC), as well as for its in vivo antitumor activity in a nude mouse model. MT201 was found to bind its target, the epithelial cell adhesion molecule (Ep-CAM; also called 17-1A antigen, KSA, EGP-2, GA733-2), with low affinity in a range similar to that of the clinically validated, murine monoclonal IgG2a antibody edrecolomab (Panorex(R)). MT201 exhibited Ep-CAM-specific CDC with a potency similar to that of edrecolomab. However, the efficacy of ADCC of MT201, as mediated by human immune effector cells, was by 2 orders of magnitude higher than that of edrecolomab. Addition of human serum reduced the ADCC of MT201 while it essentially abolished ADCC of edrecolomab within the concentration range tested. In a nude mouse xenograft model, growth of tumors derived from the human colon carcinoma line HT-29 was significantly and comparably suppressed by MT201 and edrecolomab. The fully human nature and the improved ADCC of MT201 with human effector cells will make MT201 a promising candidate for the clinical development of a novel pan-carcinoma antibody that is superior to edrecolomab.