Strong Inter-individual Variation Research Articles

Morphology and anatomical variability of the external auditory canal: A population-based MRI study

BackgroundThe external auditory canal (EAC) exhibits a complex morphology and strong inter-individual variations. However, these have not yet been comprehensively described in the literature. PurposeThis study aims to determine the width, height and cross-sectional area of the cartilaginous portion of the EAC and to describe the three-dimensional morphology and variability of different EACs. MethodsMagnetic resonance imaging was performed on 870 subjects (401 male, 469 female, resulting in 1740 EACs) who participated in the longitudinal, population-based cohort study ‘Study of Health in Pomerania–START-3’. The height and width were measured in the cartilaginous part of the EAC, between the first and second bend. The variability of the EAC morphology was visualized in three-dimensional models. ResultsThe mean height (vertical length) of the EAC was 8.62 mm (SD = 2.42) on the right, 8.47 mm (SD = 2.36) on the left. The width (horizontal length) was 4.08 mm (SD = 1.6) on the right, 3.93 mm (SD = 1.64) on the left. The EAC cross-section was 28.6 mm2 (SD = 15.19) on the right, 27.15 mm2 (SD = 14.33) on the left. The average cross-sectional area of the EAC in men was higher than in women. Subjects with larger body size had larger cross-sectional areas. Subjects with higher body mass index tended to have smaller cross-sections. Although the average EAC had an oval shape, a three-dimensional comparison of different EACs revealed strong individual variation in morphology. ConclusionThis study enhances the understanding of otolaryngologists and anatomists regarding the complex morphology and variability of the cartilaginous portion of the EAC.

Natural variability in bee brain size and symmetry revealed by micro-CT imaging and deep learning.

Analysing large numbers of brain samples can reveal minor, but statistically and biologically relevant variations in brain morphology that provide critical insights into animal behaviour, ecology and evolution. So far, however, such analyses have required extensive manual effort, which considerably limits the scope for comparative research. Here we used micro-CT imaging and deep learning to perform automated analyses of 3D image data from 187 honey bee and bumblebee brains. We revealed strong inter-individual variations in total brain size that are consistent across colonies and species, and may underpin behavioural variability central to complex social organisations. In addition, the bumblebee dataset showed a significant level of lateralization in optic and antennal lobes, providing a potential explanation for reported variations in visual and olfactory learning. Our fast, robust and user-friendly approach holds considerable promises for carrying out large-scale quantitative neuroanatomical comparisons across a wider range of animals. Ultimately, this will help address fundamental unresolved questions related to the evolution of animal brains and cognition.

Analysis of reproductive traits reveals complex population dynamics on a small geographical scale in Atlantic herring

Atlantic herring (Clupea harengus) has a complex population structure and displays a variety of reproductive strategies. Differences in reproductive strategies among herring populations are linked to their time of spawning, as well as to their reproductive investment which can be an indicator for migratory vs. stationary behavior. These differences are reflected in the number of oocytes (fecundity) and the size of the oocytes prior spawning. We studied potential mixing of herring with different reproductive strategies during the spring spawning season on a coastal spawning ground. It has been hypothesized that both spring and autumn spawning herring co-occur on this specific spawning ground. Therefore, we investigated the reproductive traits oocyte size, fecundity, fertilization success as well as length of the hatching larvae during the spring spawning season from February to April. We used a set of 11 single nucleotide polymorphism markers (SNPs), which are associated with spawning season, to genetically identify autumn and spring spawning herring. Reproductive traits were investigated separately within these genetically distinct spawning types. Furthermore, we used multivariate analyses to identify groups with potentially different reproductive strategies within the genetic spring spawners. Our results indicate that mixing between ripe spring and autumn spawners occurs on the spawning ground during spring, with ripe autumn spawners being generally smaller but having larger oocytes than spring spawners. Within spring spawners, we found large variability in reproductive traits. A following multivariate cluster analysis indicated two groups with different reproductive investment. Comparisons with other herring populations along the Norwegian coastline suggest that the high variability can be explained by the co-occurrence of groups with different reproductive investments potentially resulting from stationary or migratory behavior. Fertilization success and the length of the hatching larvae decreased with progression of the spawning season, with strong inter-individual variation, supporting our findings. Incorporating such complex population dynamics into management strategies of this species will be essential to build its future population resilience.

Cardiac activity in walleye (Sander vitreus) during exposure to and recovery from chemical anaesthesia, electroanaesthesia and electrostunning.

Handling and conducting invasive procedures are necessary for aspects of fisheries science, invariably inducing a stress response and imposing energetic demands on fish. Anaesthesia or immobilisation techniques are often used in an attempt to mitigate stress and improve welfare, yet these also come with their own impacts on post-release recovery. Here, the authors investigated whether changes in cardiac activity (heart rates over time, heart rate maxima, and scopes) differed in adult walleye (Sander vitreus) anaesthetised with AQUI-S® 20E (eugenol), electroanaesthetised with a transcutaneous electrical nerve stimulation (TENS) unit or electrostunned with a commercially developed stunning unit. This experiment was divided into two trials. In the first trial, fish were implanted with heart rate loggers and left to recover for c. 4 days. In the second trial, fish were implanted with heart rate loggers, given 3 days to recover and re-exposed to their initial treatments (excluding surgery). Post-treatment cardiac activity was quantified for both trials. Although highly variable across individuals, the authors found no significant differences in heart rate changes over time or recovery times among treatments. Maximum heart rates were consistent among treatment groups, yet significant differences in heart rate scope provided further evidence of strong interindividual variation in the second trial. Based on these results, the authors did not identify any welfare-relevant differences or concerns associated with one treatment over another. Further investigations of the relationships between measures of cardiac function and other physiological stress markers would be beneficial towards identifying best practices for fish handling in fisheries science.

Individual, sexual and temporal variation in the winter home range sizes of GPS-tagged Eurasian Curlews Numenius arquata

ABSTRACT Capsule: Eurasian Curlews Numenius arquata were faithful to foraging and roosting areas on their coastal wintering grounds, including a habitat creation site. Home range sizes were greater at night than during the day, and showed high inter-individual variability which was not related to sex. Aims: To examine factors affecting variation in the winter home range size of the largest European wader species: the near-threatened Eurasian Curlew Numenius arquata. Methods: We examined individual, sexual and temporal (day/night, seasonal and annual) variation in the size of the home ranges of 18 GPS tagged Curlews captured at two sites on the Humber Estuary, UK. Results: Home ranges were small (mean ± SD = 555.5 ± 557.9 ha) and varied slightly in size through the non-breeding season (September–March). We found some annual differences in home range size, and there was some evidence that home range size was greater at night compared to daytime. There was strong inter-individual variation in home range size, which was not related to the species’ sexual size dimorphism and thus potential differences in resource use. Conclusions: Our results highlight that wintering Curlews on the Humber Estuary maintain small home ranges which vary strongly between individuals. Knowledge of the home range size of wintering waders is vital to inform management responses to the potential impacts of environmental changes such as sea-level rise and improving the efficacy of compensatory habitats.

The influence of sham feedback on physiological processing during fear-driven stimulation

Biofeedback constitutes a well-established, non-invasive method to voluntary interfere in emotional processing by means of cognitive strategies. However, treatment durations exhibit strong inter-individual variations and first successes can often be achieved only after a large number of sessions. Sham feedback constitutes a rather untapped approach by providing feedback that does not correspond to the participant’s actual state. The current study aims to gain insights into mechanisms of sham feedback processing in order to support new techniques in biofeedback therapy. We carried out two experiments and applied different types of sham feedback on skin conductance responses and pupil size changes during affective processing. Results indicate that standardized but context-sensitive sham signals based on skin conductance responses exert a stronger influence on emotional regulation compared to individual sham feedback from ongoing pupil dynamics. Also, sham feedback should forego unnatural signal behavior to avoid irritation and skepticism among participants. Altogether, a reasonable combination of stimulus features and sham feedback characteristics enables to considerably reduce the actual bodily responsiveness already within a single session.

Cellular Uptake of Psychostimulants – Are High- and Low-Affinity Organic Cation Transporters Drug Traffickers?

Psychostimulants are used therapeutically and for illegal recreational purposes. Many of these are inhibitors of the presynaptic noradrenaline, dopamine, and serotonin transporters (NET, DAT, and SERT). According to their physicochemical properties, some might also be substrates of polyspecific organic cation transporters (OCTs) that mediate uptake in liver and kidneys for metabolism and excretion. OCT1 is genetically highly polymorphic, with strong effects on transporter activity and expression. To study potential interindividual differences in their pharmacokinetics, 18 psychostimulants and hallucinogens were assessed in vitro for transport by different OCTs as well as by the high-affinity monoamine transporters NET, DAT, and SERT. The hallucinogenic natural compound mescaline was found to be strongly transported by wild-type OCT1 with a K m of 24.3 µM and a v max of 642 pmol × mg protein−1 × min−1. Transport was modestly reduced in variants *2 and *7, more strongly reduced in *3 and *4, and lowest in *5 and *6, while *8 showed a moderately increased transport capacity. The other phenylethylamine derivatives methamphetamine, para-methoxymethamphetamine, (-)-ephedrine, and cathine ((+)-norpseudoephedrine), as well as dimethyltryptamine, were substrates of OCT2 with K m values in the range of 7.9–46.0 µM and v max values between 70.7 and 570 pmol × mg protein−1 × min−1. Affinities were similar or modestly reduced and the transport capacities were reduced down to half in the naturally occurring variant A270S. Cathine was found to be a substrate for NET and DAT, with the Km being 21-fold and the v max 10-fold higher for DAT but still significantly lower compared to OCT2. This study has shown that several psychostimulants and hallucinogens are substrates for OCTs. Given the extensive cellular uptake of mescaline by the genetically highly polymorphic OCT1, strong interindividual variation in the pharmacokinetics of mescaline might be possible, which could be a reason for highly variable adverse reactions. The involvement of the polymorphic OCT2 in the renal excretion of several psychostimulants could be one reason for individual differences in toxicity.

Impact of healthy aging on active bacterial assemblages throughout the gastrointestinal tract

ABSTRACT The adaption of gut microbiota (GM) throughout human life is a key factor in maintaining health. Interventions to restore a healthy GM composition may have the potential to improve health and disease outcomes in the elderly. We performed a comprehensive characterization of changes in the luminal and mucosa-associated microbiota composition in elderly compared with younger healthy individuals. Samples from saliva and feces, and biopsies from the upper and lower gastrointestinal tract (UGIT, LGIT), were collected from 59 asymptomatic individuals grouped by age: 40–55, 56–70, and 71–85 years). All underwent anthropometric, geriatric, and nutritional assessment. RNA was extracted and reverse-transcribed into complementary DNA; the V1–V2 regions of 16S ribosomal RNA genes were amplified and sequenced. Abundances of the taxa in all taxonomic ranks in each sample type were used to construct sample-similarity matrices by the Bray–Curtis algorithm. Significant differences between defined groups were assessed by analysis of similarity. The bacterial community showed strong interindividual variations and a clear distinction between samples from UGIT, LGIT, and feces. While in saliva some taxa were affected by aging, this number was considerably greater in UGIT and was subsequently higher in LGIT. Unexpectedly, aging scarcely influenced the bacterial community of feces over the age range of 40–85 years. The development of interventions to preserve and restore human health with increased age by establishing a healthy gut microbiome should not rely solely on data from fecal analysis, as the intestinal mucosa is affected by more significant changes, which differ from those observed in fecal analyses.

(Dé)formations du processus de néophobie. Une approche sociologique des particularités alimentaires des enfants avec un trouble du spectre autistique

Many researchers, professionals and parents underline that children with Autism Spectrum Disorders (ASD) have “eating disorders”. This research proposes to go beyond the approach in terms of “selectivity” or eating “problems”. It focuses, through the process of neophobia, on the vagaries of the construction of their eating repertoire, from birth to adolescence. The approach combines qualitative and quantitative methods. The first takes the form of interviews with parents of children with ASD aged 4 to 13 (n=21) and the second of a questionnaire with parents of adolescents with ASD aged 12 to 16 (n=322). While for parents difficulties in eating are not a warning sign of autism, they are identified very early on and make sense in retrospect with the diagnosis. Food refusals between the ages of 3 and 7 are considered the most problematic behaviors. The data show a strong inter-individual variation among children with ASD. A typology was constructed according to the forming/distortion of the neophobic process. The population studied is divided into six categories: supratypical (20.8%), normotypical (16.1%), infratypical (18.6%), progressive (17.7%), late (9.0%), and neophile (17.7%). The discussion opens with an analysis of the dietary particularities of the autistic population based on the work carried out on neophobia in the general population. It thus emerges that phenomena often identified as specific to the autistic population can reveal variations in the neophobic process. It therefore seems appropriate to speak of food neophobia in the plural.

Inter-Individual Nectar Chemistry Changes of Field Scabious, Knautia arvensis.

Nectar is crucial to maintain plant-pollinator mutualism. Nectar quality (nutritional composition) can vary strongly between individuals of the same plant species. The factors driving such inter-individual variation have however not been investigated closer. We investigated nectar quality of field scabious, Knautia arvensis in different grassland plant communities varying in species composition and richness to assess whether nectar quality can be affected by the surrounding plant community. We analyzed (with high performance liquid chromatography) the content of carbohydrates, overall amino acids, and essential amino acids. Amino acid and carbohydrate concentrations and proportions varied among plant individuals and with the surrounding plant community but were not related to the surrounding plant species richness. Total and individual carbohydrate concentrations were lowest, while proportions of the essential amino acids, valine, isoleucine, leucine (all phagostimulatory), and lysine were highest in plant species communities of the highest diversity. Our results show that K. arvensis nectar chemistry varies with the composition of the surrounding plant community, which may alter the taste and nutritional value and thus affect the plant’s visitor spectrum and visitation rate. However, the strong inter-individual variation in nectar quality requires additional studies (e.g., in semi-field studies) to disentangle different biotic and abiotic factors contributing to inter-individual nectar chemistry in a plant-community context.

Highly Variable Pharmacokinetics of Tyramine in Humans and Polymorphisms in OCT1, CYP2D6, and MAO-A.

Tyramine, formed by the decarboxylation of tyrosine, is a natural constituent of numerous food products. As an indirect sympathomimetic, it can have potentially dangerous hypertensive effects. In vitro data indicated that the pharmacokinetics of tyramine possibly depend on the organic cation transporter OCT1 genotype and on the CYP2D6 genotype. Since tyramine is a prototypic substrate of monoamine oxidase A (MAO-A), genetic polymorphisms in MAO-A may also be relevant. The aims of this study were to identify to what extent the interindividual variation in pharmacokinetics and pharmacodynamics of tyramine is determined by genetic polymorphisms in OCT1, CYP2D6, and MAO-A. Beyond that, we wanted to evaluate tyramine as probe drug for the in vivo activity of MAO-A and OCT1. Therefore, the pharmacokinetics, pharmacodynamics, and pharmacogenetics of tyramine were studied in 88 healthy volunteers after oral administration of a 400 mg dose. We observed a strong interindividual variation in systemic tyramine exposure, with a mean AUC of 3.74 min*µg/ml and a high mean CL/F ratio of 107 l/min. On average, as much as 76.8% of the dose was recovered in urine in form of the MAO-catalysed metabolite 4-hydroxyphenylacetic acid (4-HPAA), confirming that oxidative deamination by MAO-A is the quantitatively most relevant metabolic pathway. Systemic exposure of 4-HPAA varied only up to 3-fold, indicating no strong heritable variation in peripheral MAO-A activity. Systolic blood pressure increased by more than 10 mmHg in 71% of the volunteers and correlated strongly with systemic tyramine concentration. In less than 10% of participants, individually variable blood pressure peaks by >40 mmHg above baseline were observed at tyramine concentrations of >60 µg/l. Unexpectedly, the functionally relevant polymorphisms in OCT1 and CYP2D6, including the CYP2D6 poor and ultra-rapid metaboliser genotypes, did not significantly affect tyramine pharmacokinetics or pharmacodynamics. Also, the MOA-A genotypes, which had been associated in several earlier studies with neuropsychiatric phenotypes, had no significant effects on tyramine pharmacokinetics or its metabolism to 4-HPAA. Thus, variation in tyramine pharmacokinetics and pharmacodynamics is not explained by obvious genomic variation, and human tyramine metabolism did not indicate the existence of ultra-low or -high MAO-A activity.

Biological market effects predict cleaner fish strategic sophistication

Abstract Market-like situations emerge in nature when trading partners exchange goods and services. However, how partner choice option contributes to the expression of social strategic sophistication (i.e., the ability to adjust behavior flexibly given the specifics of a situation) is still poorly understood. A suitable study system to explore this question is the “cleaner” fish Labroides dimidiatus. Cleaners trade parasite removal in exchange for food with a variety of “client” species. Previous research documented strong interindividual variation in two features of their strategic sophistication, namely, the ability to adjust service quality to the presence of an audience and to give priority to clients with access to alternative cleaners (“visitor clients”) over clients lacking such choice options (“resident clients”). Here, we sampled various demes (i.e., group of individuals) of the same population of cleaner fish in order to investigate the extent to which factors describing fish densities and cleaning interaction patterns predict the strategic sophistication in two laboratory experiments. These experiments tested whether cleaners could increase their food intake through reputation management and/or learning to provide service priority to a visitor-like ephemeral food plate. We found that high “outbidding competition,” characterized by high densities of cleaners and visitor clients, along with visitor’s behavior promoting such competition, consistently predicted high strategic sophistication in cleaners. A better understanding of the role of learning versus potential genetic factors, interacting with local market conditions to affect strategic sophistication, is needed to clarify how natural selection has promoted the evolution and maintenance of cooperation in this cleaning mutualism.

Migration triggers in a large herbivore: Galápagos giant tortoises navigating resource gradients on volcanoes.

To understand how migratory behavior evolved and to predict how migratory species will respond to global environmental change it is important to quantify the fitness consequences of intra- and inter-individual variation in migratory behavior. Intra-individual variation includes behavioral responses to changing environmental conditions and hence behavioral plasticity in the context of novel or variable conditions. Inter-individual variation determines the degree of variation on which selection can act and the rate of evolutionary responses to changes in average and extreme environmental conditions. Here we focus on variation in the partial migratory behavior of giant Galápagos tortoises (Chelonoidis spp.) and its energetic consequences. We evaluate the extent and mechanisms by which tortoises adjust migration timing in response to varying annual environmental conditions, and integrate movement data within a bioenergetic model of tortoise migration to quantify the fitness consequences of migration timing. We find strong inter-individual variation in the timing of migration, which was not affected by environmental conditions prevailing at the time of migration but rather byaverage expectations estimated from multi-annual averaged conditions. This variation is associated with an average annual loss in efficiency of ~15% relative to optimal timing based on year-specific conditions. These results point towards a limited ability of tortoises to adjust the timing of their migrations based on prevailing (and, by extension, future) conditions, suggesting that the adaptability of tortoise migratory behavior to changing conditions is predicated more by past "normal" conditions than responses to prevailing, changing conditions. Our work offers insights into the level of environmental-tuning in migratory behavior and a general framework for future research across taxa.

Role of melanoma cell-intrinsic RIG-I and STING signaling for checkpoint inhibitor-mediated anticancer immunity.

3081Background: Strong inter-individual variation in clinical response to immune checkpoint inhibitors (ICB) including anti-CTLA-4 remains a major challenge, but the molecular pathways that modulat...

Rate of individuals with clearly increased radiosensitivity rise with age both in healthy individuals and in cancer patients

BackgroundThe question of an age dependence of individual radiosensitivity has only marginally been studied so far. Therefore, we analyzed blood samples of healthy individuals and cancer patients of different ages to determine individual radiosensitivity.MethodsEx vivo irradiated blood samples of 595 individuals were tested. Chromosomes 1, 2 and 4 were stained by 3-color fluorescence in situ hybridization and aberrations were analyzed. Radiosensitivity was determined by the mean breaks per metaphase (B/M).ResultsHealthy individuals (mean age 50.7 years) had an average B/M value of 0.42 ± 0.104 and an increase of 0.0014B/M per year. The patients (mean age 60.4 years) had an average B/M value of 0.44 ± 0.150 and radiosensitivity did not change with age. In previous studies we found that from a value of 0.6B/M on an individual is considered to be distinctly radiosensitive. The portion of radiosensitive individuals (B/M > 0.6) increased in both cohorts with age.ConclusionIndividual radiosensitivity rises continuously with age, yet with strong interindividual variation. No age related increase of radiosensitivity can be demonstrated in patients due to the strong interindividual variation. However among old cancer patients there is a higher probability to have patients with clearly increased radiosensitivity than at younger age.

Distribution of cone density, spacing and arrangement in adult healthy retinas with adaptive optics flood illumination.

The aim of this article is to analyse cone density, spacing and arrangement using an adaptive optics flood illumination retina camera (rtx1™) on a healthy population. Cone density, cone spacing and packing arrangements were measured on the right retinas of 109 subjects at 2°, 3°, 4°, 5° and 6° of eccentricity along 4 meridians. The effects of eccentricity, meridian, axial length, spherical equivalent, gender and age were evaluated. Cone density decreased on average from 28 884 ± 3 692 cones/mm2, at 2° of eccentricity, to 15 843 ± 1 598 cones/mm2 at 6°. A strong inter-individual variation, especially at 2°, was observed. No important difference of cone density was observed between the nasal and temporal meridians or between the superior and inferior meridians. However, the horizontal and vertical meridians differed by around 14% (T-test, p<0.0001). Cone density, expressed in units of area, decreased as a function of axial length (r2 = 0.60), but remained constant (r2 = 0.05) when cone density is expressed in terms of visual angle supporting the hypothesis that the retina is stretched during the elongation of the eyeball. Gender did not modify the cone distribution. Cone density was slightly modified by age but only at 2°. The older group showed a smaller density (7%). Cone spacing increased from 6,49 ± 0,42 μm to 8,72 ± 0,45 μm respectively between 2° and 6° of eccentricity. The mosaic of the retina is mainly triangularly arranged (i.e. cells with 5 to 7 neighbors) from 2° to 6°. Around half of the cells had 6 neighbors.

Tumor-Intrinsic RIG-I Signaling Promotes Anti-CTLA-4 Checkpoint Inhibitor-Mediated Anticancer Immunity

Strong inter-individual variation in clinical response to checkpoint inhibitors such as anti-CTLA-4 remains a major challenge. In a retrospective analysis, expression of viral defense genes in human melanomas including the cytosolic RNA receptor RIG-I (DDx58) has been associated with clinical benefit to CTLA-4 blockade. However, possible interconnections of these two distinct pathways remain unknown. Using CRISPR/Cas9 technology to generate B16 melanoma cells lines that lack nucleic acid receptors or downstream signaling molecules (RIG-I, STING, IRF3/7) together with available genetically deficient mouse models, we addressed the importance of nucleic acid receptor signaling in both tumor and host cells for the efficacy of anti-CTLA-4 immunotherapy. We here provide experimental proof that anti-CTLA-4 immunotherapy relies on tumor cell-intrinsic RIG-I but not STING signaling. Following anti-CTLA-4 treatment, tumor-intrinsic RIG-I signaling critically impacts on cross-presentation of tumor-associated antigen by CD103+ dendritic cells, the expansion of tumor antigen-specific CD8+ T cells and ultimately the accumulation of CD8+ T cells within tumor tissue. Consistently, therapeutic targeting of RIG-I with 5'-phosphorylated-RNA in both tumor and non-malignant cells potently augmented the efficacy of CTLA-4 checkpoint blockade. These processes were additionally dependent on host STING, MAVS and type I interferon signaling and were closely linked to RIG-I-mediated tumor cell death. In summary, our study identifies both tumor- and host-intrinsic RIG-I signaling as fundamental requirements for anti-CTLA-4-mediated antitumor immunity. Our data predict that targeting RIG-I may serve as a basis for the development of new combination strategies to increase the response rate of checkpoint inhibitor-based immunotherapy of malignancy including lymphoma, particularly in individuals that do not have a sufficient spontaneous antitumor T-cell immune response. Disclosuresvan den Brink:Jazz Pharmaceuticals: Consultancy; Seres: Research Funding; PureTech Health: Consultancy; Therakos Institute: Other: Speaking engagement.

High variability in migration and wintering strategies of brown skuas (Catharacta antarctica lonnbergi) in the Indian Ocean

Movements of brown skuas (Catharacta antarctica lonnbergi) originating from two populations in the southern Indian Ocean were studied during the nonbreeding period using geolocation. A total of 33 individuals were equipped resulting in 34 annual tracks recovered from 50 deployments. Brown skuas varied extensively in their post-breeding movements, from true long range migrations to reach distant wintering zones, to short movements in the vicinity of breeding grounds. Overall, brown skuas migrated northward to overwinter in different areas in the southern hemisphere; individuals remained in the Indian Ocean, except two that overwintered in the Benguela Current (Atlantic Ocean). Wintering grounds were generally situated in productive dynamic upwelling waters or frontal systems. Brown skuas avoided the less productive area of the South Subtropical Gyre in the Central Indian Ocean. Individuals clearly differed in migratory strategies, targeting areas in a continuum from the sub-Antarctic to the tropics. Inter-individual differences were not sex-dependent. The migration dates varied between sexes with females leaving the breeding sites earlier and returning later compared to males. The duration of migration depended on wintering area and sex. Males had shorter migrations than females, regardless of the wintering area. Isotopic signatures clearly indicated that birds moulted in the wintering area and during migration. The low δ 15N values of feathers that grew in mixed subtropical-sub-Antarctic waters suggest that skuas fed on low trophic level prey in these areas. The origin and consequences of such strong inter-individual variation in migratory strategies requires further investigation.

Pharmacokinetics of Bevacizumab in Three Patients Under the Age of 3 Years with CNS Malignancies

BackgroundBevacizumab is a recombinant antibody that is increasingly used in pediatric malignancies. The pharmacokinetics of bevacizumab in pediatric patients have been shown to be influenced by tumor localization and body weight. In this report, we present data on the pharmacokinetics and safety of bevacizumab in children under the age of 3 years with central nervous system (CNS) malignancies.MethodsThree patients (mean age 22 months) were treated with intravenous bevacizumab 10 mg/kg every 2 weeks. In total, 20 trough and peak bevacizumab concentrations of 10 treatment cycles were obtained at steady state.ResultsBevacizumab was generally well-tolerated in this age group. The mean trough concentration was 127 ± 29 µg/ml (range 77–155), and the mean peak concentration was 149 ± 13 µg/ml (range 113–157). Trough and peak levels were stable upon repeated treatment cycles in the same patient. In contrast, we determined strong interindividual variations in trough levels. Whereas the plasma concentration of the oldest patient matched the prediction of a previously published model, younger patients showed markedly higher trough levels.ConclusionsSerum peak concentrations of bevacizumab in children under the age of 3 years with CNS malignancies are in a similar magnitude to that found in older children and adults. Thus, a dosing schedule of bevacizumab 10 mg/kg every 2 weeks can be considered sufficient and safe, even in very young children. We further show that very young children with CNS malignancies show a markedly reduced plasma clearance, possibly related to lower body weight or differences in clearance mechanisms of antibodies.

Abstract A005: Tumor- and host-intrinsic RIG-I signaling promote anticancer immunity by CTLA-4 blockade

Abstract Introduction: Targeting inhibitory T-cell receptors such as CTLA-4 has shown great promise in cancer therapy. However, strong inter-individual variation in clinical response to checkpoint inhibitors remains a major challenge. Expression of viral defense genes in human melanomas including the cytosolic RNA receptor RIG-I (DDx58) has recently been associated with clinical benefit to CTLA-4 blockade. Methods: Using CRISPR/Cas9 technology to generate B16 melanoma cells lines that lack nucleic acid receptors or downstream signaling molecules (RIG-I, STING, IRF3/7) together with available genetically deficient mouse models, we address the importance of nucleic acid receptor signaling for the efficacy of anti-CTLA-4 immunotherapy. Results: We provide experimental proof that anti-CTLA-4 immunotherapy indeed relies on tumor cell-intrinsic RIG-I/MAVS but not cGAS/STING signaling. Consistently, therapeutic targeting of RIG-I with the specific ligand 5'‑triphosphate-RNA (3pRNA) potently augments the efficacy of CTLA-4 checkpoint blockade. In situ vaccination by intratumoral 3pRNA injection enhanced cross-presentation of tumor-associated antigens by CD103+ migratory DCs in local draining lymph nodes. Subsequent expansion of tumor-specific CD8+ T cells resulted in control of local and distant tumors, otherwise resistant to anti-CTLA‑4 monotherapy. These processes were critically dependent on tumor cell-intrinsic RIG-I-mediated immunogenic cell death (ICD), but not tumor-derived type I IFN release. In such, the synergistic therapeutic effect of RIG-I activation and anti-CTLA-4 was restricted to tumor models that showed susceptibility to RIG‑I-mediated ICD. Furthermore, systemic antitumor immunity following anti-CTLA-4 +/- 3pRNA treatment required RIG-I signaling in both tumor and non-malignant host cells. Conclusion: Our study identifies a hitherto unrecognized role of RIG-I signaling in tumors and their microenvironment as a crucial component for checkpoint inhibitor-mediated immunotherapy of cancer. Therapeutic targeting of RIG-I using specific agonists strongly augments the efficacy of anti-CTLA-4 blockade and may thus serve as the basis for new combinatorial approaches. Citation Format: Simon Heidegger, Alexander Wintges, Diana Kreppel, Sarah Bek, Michael Bscheider, Martina Schmickl, Marcel R.M. van den Brink, Christian Peschel, Tobias Haas, Hendrik Poeck. Tumor- and host-intrinsic RIG-I signaling promote anticancer immunity by CTLA-4 blockade [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A005.