[State of play of adolescent-adult transition platforms]

Transition support is an integral part of the care of adolescents in clinical services. To avoid disruptions in the care pathway, transition spaces in pediatric and adult hospitals are emerging. There are currently fifteen in France. The professionals working there and the tools and methods used are heterogeneous, but with a common challenge which is the reduction of the major risk of disruption of the care pathway and support for the life course.

Abstract PD4-01: PD4-01 Spatial transcriptomics reveals a substantial heterogeneity in TNBC tumor and stroma compartments with potential clinical implications

Background Triple negative breast cancer (TNBC) is a heterogeneous disease characterized by at least five molecular subtypes, namely basal like (BL), immunomodulatory (IM), luminal androgen receptor (LAR), mesenchymal (M) and mesenchymal stem like (MSL), associated with distinct gene expression, genomic and tumor microenvironment (TME) profiles. Recent technological advances allow to investigate intratumor geographic heterogeneity ignored by bulk tumor analyses. Here, we deployed spatial transcriptomics (ST) to interrogate tumor and stroma compartments heterogeneity and assess its association with clinical outcome. Methods Spatial transcriptomics (Visium® Spatial Gene Expression, 10X Genomics) was performed on a retrospective series of 94 case-control TNBC samples matched for known clinic-pathological parameters with available long term outcome. Detailed morphological annotations spanning 11 histomorphological categories were performed by a breast dedicated pathologist assisted by the automated QuPath digital pathology software. Bioinformatic analyses were performed using in house pipelines. Results We investigated the distribution of each morphological category across the five TNBC molecular subtypes. We found that LAR, M and MSL, even though they had less tumor cells, had more patches of very small size (p< 0.0001). On the other hand, BL and IM had few large and dense patches. Stroma had an opposite distribution compared to tumor, with LAR and MSL being enriched with stroma (p< 00001). Tumor infiltrating lymphocytes were specific of the IM (p< 0.0001) and to a lesser extent the BL subtype. Normal structures, like fat tissue (p< 0.008), lactiferous ducts (p< 0.03) and vessels (p< 0.02), were more present in MSL and LAR. The differences between the molecular subtypes are mirrored at the level of their cell composition and tumor organization, suggesting the possibility to assess TNBC molecular subtypes from imaging data alone. At the gene expression level, spatial deconvolution analyses revealed the co-existence of tumor and stroma compartments from different TNBC subtypes within a tumor sample of a given subtype as defined by bulk tumor analysis. Interestingly, these different tumor-stroma combinations were associated with prognosis. For example, M tumors associated with MSL stroma seem to have a better prognosis than M tumors with an M stroma (p=0.001). Furthermore, spatial resolution of the gene expression identified 418 individual clusters (median 4 clusters per sample) associated with specific molecular and cellular features highlighting a substantial intra-patient heterogeneity. These clusters were further grouped into 11 ecotypes associated with distinct hallmarks and pathways, including EMT, angiogenesis, DNA repair and immune profiles revealing an important inter-patient heterogeneity beyond TNBC classification. Interestingly, 2 ecotypes were identified within the IM subtype associated with distinct clinical outcome, with ecotype 6 characterized by high EMT, mesenchymal stroma and worse prognosis (p = 0,021). Conclusion To our knowledge, this is the largest study demonstrating the substantial intra- and inter-patient heterogeneity characterizing TNBC at an unprecedented level, with differences both in tumor and stroma composition as well as spatial organization and clinical outcome. Our results hightlight the need to consider TNBC heterogeneity for patient care and future clinical development including immunotherapy.

Citation Format: Xiaoxiao Wang, David Venet, Frédéric Lifrange, Denis Larsimont, Mattia Rediti, Linnea Stenbeck, David Gacquer, Floriane Dupont, Ghizlane Rouas, Matteo Serra, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. PD4-01 Spatial transcriptomics reveals a substantial heterogeneity in TNBC tumor and stroma compartments with potential clinical implications [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD4-01.

Device Processing Challenges for Miniaturized Sensing Systems Targeting Biological Fluids

This article presents a review of device processing technologies used in the fabrication of biomedical systems, and highlights the requirements of advanced manufacturing technology. We focus on biomedical systems that perform diagnostics of fluidic specimens, with analytes that are in the liquid phase. In the introduction, we define biomedical systems as well as their versatile applications and the essential current trends. The paper gives an overview of the most important biomolecules that typically must be detected or analyzed in several applications. The paper is structured as follows. First, the conventional architecture and construction of a biosensing system is introduced. We provide an overview of the most common biosensing methods that are currently used for the detection of biomolecules and its analysis. We present an overview of reported biochips, and explain the technology of biofunctionalization and detection principles, including their corresponding advantages and disadvantages. Next, we introduce microfluidics as a method for delivery of the specimen to the biochip sensing area. A special focus lies on material requirements and on manufacturing technology for fabricating microfluidic systems, both for niche and mass-scale production segments. We formulate requirements and constraints for integrating the biochips and microfluidic systems. The possible impacts of the conventional microassembly techniques and processing methods on the entire biomedical system and its specific parts are also described. On that basis, we explain the need for alternative microassembly technologies to enable the integration of biochips and microfluidic systems into fully functional systems.

Étude MUMI-19 (mothers undergoing mental impact of COVID-19 pandemic) : évaluation de l’impact de l’isolement maternel dans le post-partum immédiat sur le taux de dépression du post-partum en période de pandémie COVID-19

Introduction

La pandémie de COVID-19 a bouleversé le monde en imposant des mesures sanitaires inédites, notamment en suites de couches. Cette étude a pour but d’évaluer l’impact de l’isolement maternel dans le post-partum immédiat sur le taux de dépression du post-partum (DPP) dans une maternité de type 3.

Méthodes

Nous avons mené une étude de cohorte prospective de type exposés–non exposés, entre le 22 avril et le 29 octobre 2020, en utilisant des questionnaires anonymes sur 265 parturientes (129 pendant le confinement et 135 en dehors). L’échelle postnatale d’Edimbourg (EPDS) a été utilisée. Nous avons utilisé un modèle de régression logistique univariée pour l’association entre les facteurs de risques et la DPP.

Résultats

Il n’y avait pas de différence entre les deux groupes concernant la DPP évaluée par un score > 10,5 à l’EPDS à j30 et/ou j60 (23,1 % vs 29,3 %, p = 0,661). En revanche, dans le groupe « confiné », le score à j3 était plus élevé (31 % vs 17,8 %, p = 0,015) et les conjoints davantage impactés sur le plan psychologique (48,3 % vs 10,5 %, p < 0,001). La parité ?1 était un facteur protecteur de DPP (OR = 0,2, IC95 % [0,1–0,6], p = 0,003). Les antécédents de violence psychologiques (OR = 6,4, IC95 % [1,1–37,6], p = 0,04), la présence d’un stress durant la grossesse (OR = 4,5, IC95 % [1,6–12,6], p = 0,004) et le vécu traumatique de l’accouchement (OR = 5,1, IC95 % [1,4–17,8], p = 0,012) étaient associés à un sur-risque de DPP.

Conclusion

L’isolement maternel dans le post-partum immédiat est associé à un sur-risque de symptômes sévères de blues du post-partum.

Abstract 182: Recapitulating spatial tumor morphology using automated classifier in triple negative breast cancer

Introduction Triple negative breast cancer (TNBC) is a heterogeneous disease. Spatial transcriptomics (ST) interrogates gene expression in spatially defined spots. Here, we assessed whether ST expression data could identify specific histomorphologic features from TNBC samples, the ultimate goal being to develop a tool allowing to automatically annotate ST slides from gene expression data.

Methods ST expression profiles were obtained from 41 TNBC samples. T and B cell immune phenotyping was performed on a consecutive slide using double CD3/CD20 IHC. All samples were manually annotated in 11 histomorphological categories (see Table). ST spots with artifacts or less than 500 reads were removed from the analysis. Each spot was assigned to its most common annotation. A linear booster classifier was used to classify the spots into 11 histomorphological categories based on gene expression. Classification accuracy was summarized by area under the ROC curve (AUC), assessed using leave-a-patient-out (LPO) or in-patient 10-fold cross-validation (xVal).

Results Most ST spots were annotated as invasive tumor and stroma with low TILs as well stroma with high TILs (see Table). Overall, the performance of the classifier was very high. However, xVal method obtained higher AUC than the LPO method, reflecting higher interpatient than intrapatient variations. Necrosis, in situ carcinoma and B cells were very variable between patients, but not intrapatient, as shown by low LPO and high xVal AUCs. Of note, misclassification of B cells could be due to poor distinction of B vs T cells on HE slides despite IHC support. Spots with multiple annotations were also more difficult to classify.

Conclusion Here, we developed a high-performance classifier based on the biggest series of ST data allowing to identify several histomorphological features from TNBC tissues, representing a unique tool for further ST research.

SupercategoriesCategoriesAbbreviationsN spotsN samplesAUC LPO (%)AUC Xval (%)StromaStroma220484180.292.5Stroma with low TILslow sTILs140924178.291.8Stroma with high TILshigh sTILs75543984.394.8Blood vesselsBV1912774.283.6Lymphoid nodulesLN185148994.9High lymphocytes B areasBcell26564.495.9Invasive tumorIT126364088.894.7Invasive tumor with low or no intratumoral TILslow iTILs101773987.594.6Invasive tumor with high intratumoral TILshigh iTILs24592484.897.1OthersFat tissuesFT27212292.897.4NecrosisN10621975.295.4In situ carcinomaIS289749.399.1Normal glandsNG1741686.794.4

Citation Format: Xiaoxiao Wang, David Venet, Floriane Dupont, Ghizlane Rouas, Linnea Stenberg, Annelie Mollbrink, Denis Larsimont, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Recapitulating spatial tumor morphology using automated classifier in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 182.

Abstract 609: Contribution of the tumor and stroma compartments for TNBC molecular classification using spatial transcriptomics analysis

Introduction Triple negative breast cancer (TNBC) is a heterogeneous disease associated at least with five distinct molecular subtypes namely basal like (BL), immunomodulatory (IM), luminal AR (LAR), mesenchymal (M) and mesenchymal-stem like (MSL). Spatial transcriptomics (ST) interrogates gene expression in spatially defined spots. Here, we aimed to assess the contribution of tumor and stroma compartments in defining each TNBC molecular subtype by comparing bulk tumor RNAseq, pseudo-bulk (PB) derived from ST, tumor and stroma ST spots.

Methods Spatially resolved gene expression profiles were obtained from 94 TNBC samples using ST, spots with artifacts or less than 500 reads being excluded from further analysis. Forty-one TNBC samples were manually annotated by a breast pathologist into 3 different classes: tumor, stroma and the rest. Manual histological annotation was used to build a classifier to assign each ST spot to tumor or stroma compartment. Bulk RNAseq data was obtained from consecutive sections for all tumors using RiboZero kit. PB profiles were obtained by summing the reads from all the spots of a given tumor, as well as from all spots classified as tumor and stroma compartment. A linear booster classifier was used to classify the spots based on gene expression. Each bulk and PB was assigned to one of 5 TNBC molecular subtypes.

Results PB data derived from ST analysis identified 18 BL, 26 IM, 10 LAR, 27 M and 13 MSL among the 94 TNBC tumor samples. An 87% concordance in the subtyping was observed between the bulk and PB data, with half of the discordant cases being between BL and IM subtypes. All LAR and BL tumors, as well as most M (96%) were consistently classified using tumor spots only whereas all MSL (100%) and the majority of LAR (91%) and IM (92%) samples were concordant using stroma spots only. In half of the IM samples, the signal derived from both the tumor and the stroma compartments while in the other half derived from the stroma. Misclassification mainly occurred between BL and IM subtypes, as well as between M and MSL. LAR subtype appeared to be the most stable one.

Conclusion The use of spatial transcriptomics allowed to show the relative contribution of the tumor and stroma compartments for TNBC molecular classification. The LAR, BL and M subtypes were driven by signals from the tumor compartment while MSL was driven by the stroma compartment. The IM signal was derived by both the tumor and stroma compartments.

Citation Format: David Venet, Xiaoxiao Wang, Floriane Dupont, Ghizlane Rouas, Linnea Stenbeck, Annelie Mollbrink, Denis Larsimont, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Contribution of the tumor and stroma compartments for TNBC molecular classification using spatial transcriptomics analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 609.

Unraveling Triple-Negative Breast Cancer Tumor Microenvironment Heterogeneity: Towards an Optimized Treatment Approach

Background

Recent efforts of gene expression profiling analyses recognized at least four different triple-negative breast cancer (TNBC) molecular subtypes. However, little is known regarding their tumor microenvironment (TME) heterogeneity.

Methods

Here, we investigated TME heterogeneity within each TNBC molecular subtype, including immune infiltrate localization and composition together with expression of targetable immune pathways, using publicly available transcriptomic and genomic datasets from a large TNBC series totaling 1512 samples. Associations between molecular subtypes and specific features were assessed using logistic regression models. All statistical tests were two-sided.

Results

We demonstrated that each TNBC molecular subtype exhibits distinct TME profiles associated with specific immune, vascularization, stroma, and metabolism biological processes together with specific immune composition and localization. The immunomodulatory subtype was associated with the highest expression of adaptive immune-related gene signatures and a fully inflamed spatial pattern appearing to be the optimal candidate for immune check point inhibitors. In contrast, most mesenchymal stem-like and luminal androgen receptor tumors showed an immunosuppressive phenotype as witnessed by high expression levels of stromal signatures. Basal-like, luminal androgen receptor, and mesenchymal subtypes exhibited an immune cold phenotype associated with stromal and metabolism TME signatures and enriched in margin-restricted spatial pattern. Tumors with high chromosomal instability and copy number loss in the chromosome 5q and 15q regions, including genomic loss of major histocompatibility complex related genes, showed reduced cytotoxic activity as a plausible immune escape mechanism.

Conclusions

Our results demonstrate that each TNBC subtype is associated with specific TME profiles, setting the ground for a rationale tailoring of immunotherapy in TNBC patients.

Natural History of Perianal Fistulising Lesions in Patients With Elderly-onset Crohn's Disease: A Population-based Study

INTRODUCTION

Most studies of elderly-onset Crohn's disease [CD; diagnosed in patients aged 60 or over] have described a mild course. However, data on the natural history of perianal fistulising CD [pfCD] in this population are scarce. In a population-based cohort study, we described the prevalence, natural history, and treatment of pfCD in patients with elderly-onset CD vs patients with paediatric-onset CD.

METHOD

All patients diagnosed with CD at or after the age of 60 between 1988 and 2006, were included [n = 372]. Logistic regression, Cox models, and a nested case-control method were used to identify factors associated with pfCD.

RESULTS

A total of 34 elderly patients [9% of the 372] had pfCD at diagnosis. After a median follow-up of 6 years (interquartile range [IQR]: 3; 10), 59 patients [16%] had pfCD; the same prevalence [16%] was observed in paediatric-onset patients. At last follow-up, anal incontinence was more frequent in elderly patients with pfCD than in elderly patients without pfCD [22% vs 4%, respectively; p < 10-4]. Rectal CD at diagnosis was associated with pfCD: hazard ratio (95% confidence interval [CI] = 2.8 [1.6-5.0]). Although 37% of the patients received immunosuppressants and 17% received anti-tumour necrosis factor agents, 24% [14 out of 59] had a definitive stoma at last follow-up.

CONCLUSION

During the first 6 years of disease, the prevalence of pfCD was similar in elderly and paediatric patients. Rectal involvement was associated with the appearance of pfCD in elderly-onset patients. Around a quarter of patients with elderly-onset CD will have a stoma. Our results suggest that treatment with biologics should be evaluated in these patients.

Abstract P4-06-03: Unravelling triple-negative breast cancer tumor microenvironment heterogeneity using an integrative multiomic analysis

Introduction: Triple negative breast cancer (TNBC) constitute 10-20% of all breast cancers and is associated with a worse prognosis and limited treatment options. Recent trials evaluating immune checkpoint blockade in TNBC demonstrated encouraging results for a subset of patients. TNBC is highly heterogeneous and its tumour microenvironment (TME) has been recognized as a critical determinant of its behavior and clinical outcome. Genome-wide gene expression profiling analyses have already improved our understanding of the complexity of this disease and have defined 6 different molecular subtypes namely Basal-like 1 (BL1), basal-like 2 (BL2), immunomodulatory (IM), mesenchymal (M), mesenchymal stem-like (MSL) and luminal androgen receptor (LAR), exhibiting distinct biological and clinical characteristic.

In this study, we aim to dissect the molecular diversity of the TME and more specifically to assess the immune landscape according to TNBC molecular subtypes.

Methods: A cohort of 485 TNBC patient with publicly available data (RNA-Seq and Illumina HT-12 v3) from the METABRIC and the TCGA consortia were used in the gene expression analysis. Gene signatures reflecting different features or cellular components (immune, stromal, angiogenesis, lymphangiogenesis, hypoxia, metabolism) of the TME were used to evaluate multiple biological processes known to contribute to tumorogenesis. A compendium of 17 immune specific gene signatures and T cell localisation classification were used to evaluate the immune composition and spatial pattern of immune infiltrates. All parameters were compared using a logistic regression model to evaluate their relative contribution according to each molecular subtype.

Results: Our analyses demonstrated that each molecular subtype exhibits different TME profiles, as well as specific immune composition and localisation. IM tumors were associated with the highest expression of immune-related gene signatures, enriched with adaptive immune cells and with a fully inflamed spatial pattern. MSL tumors were mostly associated with the expression of Lymphangiogenesis and Stromal TME signatures. They also exhibited some immune activity through the expression of immune gene signatures capturing innate immune and adaptive immunosuppressive cells. This subtype was mainly associated with margin restricted and to some extent with fully inflamed spatial pattern. BL1 tumors were associated with the expression of Metabolism TME signatures, along with fully inflamed and stroma restricted spatial pattern. To a lesser extent, this subtype was also associated with activated DC and CD4 Tem cells. LAR and M tumors exhibited an immune cold phenotype. They were associated with Stromal and Metabolism TME signatures, enriched in margin restricted spatial pattern and negatively associated with every immune cells.

Conclusions: Our results demonstrate for the first time the huge heterogeneity that characterizes the TME of TNBCs. Identification of specific TME profiles could help to design more rationale and appropriate synergistic therapeutic combinations targeting TME elements in this high-risk disease.

Citation Format: Bareche Y, Buisseret L, Gruosso T, Girard E, Venet D, Dupont F, Desmedt C, Park M, Rothé F, Stagg J, Sotiriou C. Unravelling triple-negative breast cancer tumor microenvironment heterogeneity using an integrative multiomic analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-06-03.

Abstract 3801: Functional relevance of A-to-I RNA editing on the immune response in breast cancer

INTRODUCTION: RNA editing is a post-transcriptional modification that changes double stranded RNA sequences (dsRNA). The most common way of editing in humans is the Adenosine-to-Inosine type, which is catalyzed by members of the ADAR enzymes family. A-to-I RNA editing has been shown to be essential for normal tissue development but also plays a crucial role in many cancers. We have notably shown that in breast cancer the editing frequency is increased in tumors as compared to normal tissue and correlates with ADAR expression. We also showed that type I IFN response and ADAR DNA copy number together explain 53% of ADAR expression in breast cancers. Moreover, the implication of ADAR-mediated RNA editing in preventing the sensing of endogenous dsRNA leading to inhibition of the immune response has been recently reported. ADAR-mediated RNA editing may play a crucial role in tumor progression by modulating immune response through the dsRNA sensing pathway. Here, we aim to assess the influence of ADAR-mediated RNA editing in the sensing of endogenous dsRNA and the immune response in breast cancer.

MATERIAL & METHODS: ADAR expression was modulated in MDAMB231 breast cancer cell line using shRNA lentiviral transduction and lentiviral plasmid transduction for ADAR inhibition and ADAR wild-type and editing-deficient mutant overexpression respectively. ADAR expression was assessed by RTqPCR/Western blotting. dsRNA level was evaluated by immunofluorescence using the dsRNA-specific J2 antibody (Scicons).

RESULTS: Poly I:C transfection, mimicking dsRNAs, as well as IFN Type I exposure induced the immune response in BC cell lines, in particular it increases the expression of RIG-I, MDA5 and IRF7 involved in the dsRNA sensing pathway. DNMTi treatment, known as an inducer of dsRNA level, also activated cytosolic dsRNA response in these cells in a dose dependent manner. In order to assess the role of ADAR-mediated RNA editing in the activation of the dsRNA sensing pathway, we exposed MDAMB231 cell lines in which ADAR expression was modulated to DNMTi. A wide range of doses of DNMTi, from 0.3 to 50μM, and time of exposure, from 3h to 72h, were tested. The cytosolic dsRNA pathway was induced in a dose dependent manner after DNMTi exposure. However, no effect of ADAR modulation on the activation of the pathway was observed. No difference in dsRNA levels was observed after activation of the immune pathway by DNMTi or IFN exposure, nor after ADAR modulation.

CONCLUSION & PERSPECTIVES: dsRNA pathway activation by DNMTi, poly I:C transfection or IFN Type I treatment is not dependent of ADAR in MDAMB231 cell lines. Moreover, in contrast to data in colorectal cell lines, our data suggest that DNMTi exposure does not increase cytosolic dsRNA level.

Citation Format: Floriane Dupont, Florian Clatot, David Venet, Véronique Kruys, Debora Fumagalli, Vincent Detours, Françoise Rothé, Christos Sotiriou. Functional relevance of A-to-I RNA editing on the immune response in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3801.

Abstract P2-05-04: Deregulation of A-to-I RNA editing is associated with poor prognosis in HER2+ breast cancers in the neoALTTO trial

Background

A-to-I RNA editing, a post-transcriptional modification of the RNA catalyzed by the ADAR family of enzymes, is emerging as a widespread phenomenon in breast cancer (BC). A-to-I RNA editing is more frequent in the highly repetitive Alu regions but can affect both coding and non-coding regions. It has been shown to greatly impact cell functionality. In a recent report, we have shown that A-to-I RNA editing is regulated both by ADAR copy number and type I interferon response (Fumagalli et al. Cell Rep 2015). The main aim of the current study was to investigate the extent and profile of A-to-I RNA editing in HER2+ BC patients (pts) treated in the NeoALTTO trial, and to explore its impact on pathologic complete response (pCR) and survival.

Methods

Aligned RNAseq reads of sufficient quality and quantity were obtained for 252 of the 455 pts enrolled in the study, as described previously (Fumagalli et al. JAMA Oncol 2016). Editing sites from the rediPortal database were assessed. The editing level at a given site was computed by counting the number of Gs and As. Sites with coverage more than 10 were considered for further analyses. Editing in normal tissues was obtained from the GTEx project of the rediPortal database. Tumor infiltrating lymphocytes (TILs) and copy number aberrations were previously reported. Correlations between different parameters were assessed using Spearman correlations (ρ). The Mann-Whitney test was used to relate binary and numerical features. Event-free survival (EFS) analysis was performed using the Cox proportional hazard model.

Results

There was a median of 71470 edited sites per sample. As expected, mean editing per sample correlated with ADAR expression (ρ=59%, p&lt;10-16) and ADAR copy number (ρ=54%, p&lt;10-16). It was also correlated with the IFN-gamma driven signature (ρ=22%, p=0.0005), as well as with ESR1 gene expression (ρ=24%, p=0.0002). Neither ADAR expression nor mean editing was correlated with TILs (ρ=-0.5% and ρ=3%). No relationship between mean editing and pCR or EFS was found. The correlations between editing in NeoALTTO tumor samples and GTEx normal tissues were computed, and the median editing per sample was taken. These median correlations, ranging from 32% to 56%, were not associated with ADAR expression (ρ=-25%, p=6x10-5) nor mean editing (ρ=8%, p=0.19). Of interest, patients whose tumors showed low correlation with editing in normal tissues were associated with poor EFS (p=0.028, HR=0.56 to 0.96) suggesting that deregulation of RNA editing may impact disease progression and outcome. Similar results were obtained when the correlations were assessed between tumor samples instead of between tumor and normal samples (ρ between the two median editing: 76%; p-value survival: 0.013). The median correlations were not predictive for pCR (p=0.44). There was no interaction between editing and treatment arm.

Conclusions

Our study shows for the first time that deregulated RNA editing, as compared to editing in normal tissues, is a widespread phenomenon in HER2+ BC patients treated in the NeoALTTO trial and is associated with poor outcome. These results may provide new perspectives for the treatment of HER2+ disease by developing therapies targeting RNA editing.

Citation Format: Venet D, Rothé F, Dupont F, Maetens M, Fumagalli D, Salgado R, Bradbury I, Pusztai L, Harbeck N, Izquierdo M, de la Pena L, Ignatiadis M, de Azambuja E, Huober J, Nuciforo P, Baselga J, Piccart M, Loi S, Sotiriou C. Deregulation of A-to-I RNA editing is associated with poor prognosis in HER2+ breast cancers in the neoALTTO trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-05-04.

Dramatic Increase in Incidence of Ulcerative Colitis and Crohn's Disease (1988-2011): A Population-Based Study of French Adolescents

OBJECTIVES

Few data are available to describe the changes in incidence of pediatric-onset inflammatory bowel disease (IBD). The aim of this study was to describe changes in incidence and phenotypic presentation of pediatric-onset IBD in northern France during a 24-year period.

METHODS

Pediatric-onset IBD (<17 years) was issued from a population-based IBD study in France between 1988 and 2011. Age groups and digestive location were defined according to the Paris classification.

RESULTS

1,350 incident cases were recorded (8.3% of all IBD) including 990 Crohn's disease (CD), 326 ulcerative colitis (UC) and 34 IBD unclassified (IBDU). Median age at diagnosis was similar in CD (14.4 years (Q1=11.8-Q3=16.0)) and UC (14.0 years (11.0-16.0)) and did not change over time. There were significantly more males with CD (females/males=0.82) than UC (females/males=1.25) (P=0.0042). Median time between onset of symptoms and IBD diagnosis was consistently 3 months (1-6). Mean incidence was 4.4/10⁵ for IBD overall (3.2 for CD, 1.1 for UC and 0.1 for IBDU). From 1988-1990 to 2009-2011, a dramatic increase in incidences of both CD and UC were observed in adolescents (10-16 years): for CD from 4.2 to 9.5/10⁵ (+126%; P<0.001) and for UC, from 1.6 to 4.1/10⁵ (+156%; P<0.001). No modification in age or location at diagnosis was observed in either CD or UC.

CONCLUSIONS

In this population-based study, CD and UC incidences increased dramatically in adolescents across a 24-year span, suggesting that one or more strong environmental factors may predispose this population to IBD.

Extra-intestinal Manifestations at Diagnosis in Paediatric- and Elderly-onset Ulcerative Colitis are Associated With a More Severe Disease Outcome: A Population-based Study

BACKGROUND AND AIMS

Data on extra-intestinal manifestations [EIM] and their impact on the disease course of ulcerative colitis [UC] in population-based cohorts are scarce, particularly in paediatric- and elderly-onset UC patients. The aims of this population-based study were to assess: 1] the occurrence of EIM in paediatric- and elderly-onset UC; 2] the factors associated with EIM; and 3] their impact on long-term disease outcome.

METHODS

Paediatric-onset [< 17 years at diagnosis] and elderly-onset UC patients [> 60 years at diagnosis] from a French prospective population-based registry [EPIMAD] were included. Data on EIM and other clinical factors at diagnosis and at maximal follow-up were collected.

RESULTS

In all, 158 paediatric- and 470 elderly-onset patients were included [median age at diagnosis 14.5 and 68.8 years, median follow-up 11.2 and 6.2 years, respectively]. EIM occurred in 8.9% of childhood- and 3% of elderly-onset patients at diagnosis and in 16.7% and 2.2% of individuals during follow-up [p < 0.01], respectively. The most frequent EIM was joint involvement [15.8% of paediatric onset and 2.6% of elderly-onset]. Presence of EIM at diagnosis was associated with more severe disease course [need for immunosuppressants or biologic therapy or colectomy] in both paediatric- and elderly-onset UC (hazard ratio [HR] = 2.0, 95% confidence interval [CI]: 1.0-4.2; and HR = 2.8, 0.9-7.9, respectively). Extensive colitis was another independent risk factor in both age groups.

CONCLUSIONS

Elderly-onset UC patients had lower risk of EIM either at diagnosis or during follow-up than paediatric-onset individuals. EIM at diagnosis predicted more severe disease outcome, including need for immunosuppressive or biologic therapy or surgery, in both paediatric- and elderly-onset UC.

A simple reconstructed human epidermis: preparation of the culture model and utilization in in vitro studies

The preparation of a reconstructed human epidermis is described with examples of its utilization in in vitro studies. The model was obtained by culturing normal human keratinocytes at high cell density for 14 days in serum-free and high calcium (1.5 m M) medium on an inert polycarbonate filter at the air-liquid interface. These stratified cultures showed histological features similar to those observed in vivo in the epidermis: a proliferating basal layer and differentiating spinous, granular, and cornified layers. Electron microscopy illustrated lamellar bodies, junctions and keratohyalin granules. Immunofluorescent localization of epidermal markers (keratins 14 and 10, involucrin and filaggrin) revealed typical differentiation. This in vitro reconstructed tissue was used in studies of toxic effects of chemicals. The modelled tissue showed progressive cytotoxicity of a skin irritant (benzalkonium chloride) and a sensitizer (dinitrochlorobenzene) as assessed by MTT assay. Moreover, differential release of interleukin-1alpha and interleukin-8 were measured after 20 h of incubation allowing the irritant to be distinguished from the sensitizer. Permeation studies indicated efficient barrier function of the reconstructed epidermis, as well as metabolizing properties towards hormones. This model can be custom-made and is potentially useful for studies involving keratinocytes in the epidermis, in basic science, dermatology or toxicology.

A novel MVMp-based vector system specifically designed to reduce the risk of replication-competent virus generation by homologous recombination

Recent work highlights the potential usefulness of MVM-based vectors as selective vehicles for cancer gene therapy (Dupont et al, Gene Therapy, 2000; 7: 790-796). To implement this strategy, however, it is necessary to develop optimized methods for producing high-titer, helper-free parvovirus stocks. Recombinants of MVMp (rMVMp) are currently generated by transiently co-transfecting permissive cell lines with a plasmid carrying the vector genome and a helper plasmid expressing the capsid genes (replaced with a foreign gene in the vector genome). The resulting stocks, however, are always heavily contaminated with replication-competent viruses (RCV), which precludes their use in vivo and particularly in gene therapy. In the present work we have developed a second-generation MVMp-based vector system specifically designed to reduce the probability of RCV generation by homologous recombination. We have constructed a new MVMp-based vector and a new helper genome with minimal sequence overlap and have used the degeneracy of the genetic code to further decrease vector-helper homology. In this system, the left homologous region was almost completely eliminated and the right sequence overlap was reduced to 74 nt with only 61% homology. We were thus able to substantially reduce ( approximately 200 x), but not completely eliminate, generation of contaminating viruses in medium-scale rMVMp preparations. Since the remaining sequence homology between the new vector and helper genomes is weak, our results suggest that contaminating viruses in this system are generated by nonhomologous recombination. It is important to note, unlike the autonomously replicating helper viruses produced from the first-generation vector/helper genomes, the contaminating viruses arising from the new packaging system cannot initiate secondary infection rounds (so they are not 'replication-competent viruses'). Our findings have important implications for the design of new MVMp-based vectors and for the construction of trans-complementing packaging cell lines.

Changes in regional myocardial function after coronary artery bypass graft surgery are predicted by intraoperative low-dose dobutamine echocardiography

BACKGROUND

Left ventricular dysfunction is often reversed after coronary artery bypass graft (CABG) surgery; however, this change is not easily predicted. The authors hypothesized that functional changes after a low dose of dobutamine (5 microgram. kg-1. min-1) intraoperatively would predict functional changes when complete revascularization was achieved.

METHODS

The authors analyzed 560 segments in 40 patients scheduled for elective CABG surgery for regional wall motion (1-5 scoring system) at four stages: baseline (after induction and intubation), with administration of low-dose dobutamine before cardiopulmonary bypass, after separation from cardiopulmonary bypass (early), and after administration of protamine (late). Two independent observers scored the myocardial regions according to a 16-segment model in multiple imaging planes. For each segment, the response to dobutamine was dichotomized as improved or not improved from baseline and analyzed with logistic regression. The influence of covariates (ejection fraction, myocardial infarction, diabetes mellitus, and beta blockers) was also determined with logistic regression models. P < 0.05 was considered significant.

RESULTS

Changes in myocardial function after low-dose dobutamine were highly predictive for early (P < 0.0001) and late (P < 0.0001) changes in myocardial function from baseline regional scores. The overall odds ratio for early and late improvement increased by 20.7 and 34.6, respectively, when improvement was observed after low-dose dobutamine was administered. The overall positive predictive value of improved regional wall motion after CABG did not vary with left ventricular ejection fraction, a history of myocardial infarction, or beta blocker use, and it varied little with diabetic status (range, 0.86-0.96) if regional wall motion improved with low-dose dobutamine before CABG. The overall negative predictive value was 0.70; however, the range varied with diabetic status (i.e., lowest in diabetic patients and highest in nondiabetic patients).

CONCLUSION

Intraoperative low-dose dobutamine is a reliable method to predict myocardial functional reserve and to determine functional recovery expected after coronary revascularization.

Tumor-selective gene transduction and cell killing with an oncotropic autonomous parvovirus-based vector

A recombinant MVMp of the fibrotropic strain of minute virus of mice (MVMp) expressing the chloramphenicol acetyltransferase reporter gene was used to infect a series of biologically relevant cultured cells, normal or tumor-derived, including normal melanocytes versus melanoma cells, normal mammary epithelial cells versus breast adenocarcinoma cells, and normal neurons or astrocytes versus glioma cells. As a reference cell system we used normal human fibroblasts versus the SV40-transformed fibroblast cell line NB324K. After infection, we observed good expression of the reporter gene in the different tumor cell types, but only poor expression if any in the corresponding normal cells. We also constructed a recombinant MVMp expressing the green fluorescent protein reporter gene and assessed by flow cytometry the efficiency of gene transduction into the different target cells. At a multiplicity of infection of 30, we observed substantial transduction of the gene into most of the tumor cell types tested, but only marginal transduction into normal cells under the same experimental conditions. Finally, we demonstrated that a recombinant MVMp expressing the herpes simplex virus thymidine kinase gene can, in vitro, cause efficient killing of most tumor cell types in the presence of ganciclovir, whilst affecting normal proliferating cells only marginally if at all. However, in the same experimental condition, breast tumor cells appeared to be resistant to GCV-mediated cytotoxicity, possibly because these cells are not susceptible to the bystander effect. Our data suggest that MVMp-based vectors could prove useful as selective vehicles for anticancer gene therapy, particularly for in vivo delivery of cytotoxic effector genes into tumor cells.

Oncoselective transduction of CD80 and CD86 in tumor cell lines using an autonomous recombinant parvovirus

BACKGROUND

The aim of this study was to enhance selectively the immunostimulatory properties of tumor cells. Based on their oncotropic properties, we used autonomous recombinant parvoviruses to transduce the genes coding for the constimulatory molecules CD80 (B7-1) or CD86 (B7-2) specifically into tumor cells without transducing normal cells.

MATERIALS AND METHODS

After infection of tumor cells by these viruses, surface expression of CD80 and CD86 molecules was assessed by FACS and enhancement of immunostimulatory properties was assessed in alloreactions with G-10 purified T cells.

RESULTS

Infection of normal and transformed cells with recombinant MVM- B7-1 or B7-2 viruses leads to expression of costimulatory molecules only by tumor cells and confers on them the capacity to sensitize naive T cells in vitro.

CONCLUSION

This approach should ultimately lead to selective expression of costimulatory molecules in tumor tissues in vivo without affecting normal cells.

Method for concentrating and purifying recombinant autonomous parvovirus vectors designed for tumour-cell-targeted gene therapy

Recent work has highlighted the use of parvoviruses as potential vectors for tumour-cell-targeted gene therapy. The oncotropic properties of the prototype strain of minute virus of mice (MVMp) suggest that this virus might be a useful vehicle for introducing selectively therapeutic genes, e.g. lymphokine or suicide genes, into tumour cells and preferentially expressing them. But the low titre of recombinant virus stocks (10(5)-10(6) infectious units per ml) and their high level of contamination by cell proteins make it practically impossible to evaluate their efficacy in in vivo systems. A technique is described for producing cellular contaminant-free stocks of recombinant virus particles, with titres up to 5 x 10(8) IU/ml.

Brachmann-de Lange syndrome: pre- and postnatal findings

Brachmann-de Lange syndrome (BDLS) is a well-delineated and relatively common syndrome. However, prenatal diagnosis has never been reported, even if in some cases ultrasonography demonstrated one or more manifestations of the syndrome. We report on 3 cases: in the first 2 cases, prenatal ultrasonography demonstrated some signs of the condition. The third represents, to our knowledge, the first prenatal diagnosis of BDLS. We also present a review of the literature concerning pre- and postnatal findings in this syndrome.

Gene therapy for cancer

This review looks at various gene therapy strategies that are currently being investigated either in experimental studies or in clinical trials. These approaches attempt to either enhance the antitumor immune response of the host, express conditional toxins specifically in tumor cells, reverse the transformed phenotype of tumor cells, or protect normal tissues against the toxicities of conventional treatments.

Cruciform structure of a DNA motif of parvovirus minute virus of mice (prototype strain) involved in the attenuation of gene expression

It has previously been reported that the region between nucleotides 259 and 383 immediately downstream from the P4 early promoter of parvovirus minute virus of mice, prototype strain (MVMp) is responsible for transcriptional attenuation. Attenuation results from the premature pausing of RNA polymerase II within this sequence (designated to as att) and seems to depend on potential RNA secondary structure. To assess the attenuation capacity of att under near physiological conditions, the early transcription unit of MVMp was replaced by the chloramphenicol acetyltransferase reporter gene under control of the early P4 promoter, in the presence or absence of att. The resulting recombinant vectors were encapsidated in parvovirus particles and replicated in cells after co-infection with the wild-type virus. The att fragment reduced the rate of expression of the reporter gene by approximately threefold, confirming previously reported data from transfection experiments performed in the same cellular system. This attenuation factor is unexpectedly high, considering that the 'readthrough' fold of the nascent viral transcript is thermodynamically more stable than the 'attenuation' configuration. In an attempt to elucidate this point, we sought for the presence of secondary structures in the template DNA molecule. In vitro nuclease probing of viral dsDNA revealed that the att fragment had a cruciform configuration with both complementary strands folding into the computer-predicted stem-loop 'attenuation' structure. These observations lead us to propose that the secondary structure of the DNA template may prompt the formation of the 'attenuation' stem-loop in nascent mRNAs by bringing corresponding self-complementary sequences into close proximity.

Use of an autonomous parvovirus vector for selective transfer of a foreign gene into transformed human cells of different tissue origins and its expression therein

In this work, we report the transduction of a chloramphenicol acetyltransferase (CAT) reporter gene into a variety of normal and transformed human cells of various tissue origins. The vector used was MVM/P38cat, a recombinant of the prototype strain of the autonomous parvovirus minute virus of mice (MVMp). The CAT gene was inserted into the capsid-encoding region of the infectious molecular clone of MVMp genome, under the control of the MVM P38 promoter. When used to transfect permissive cells, the MVM/P38cat DNA was efficiently replicated and expressed the foreign CAT gene at high levels. By cotransfecting with a helper plasmid expressing the capsid proteins, it was possible to produce mixed virus stocks containing MVM/P38cat infectious particles and variable amounts of recombinant MVM. MVM/P38cat viral particles were successfully used to transfer the CAT gene and to express it in a variety of human cells. Both viral DNA replication and P38-driven CAT expression were achieved in fibroblasts, epithelial cells, T lymphocytes, and macrophages in a transformation-dependent way, but with an efficiency depending on the cell type. In transformed B lymphocytes, however, the vector was not replicated, nor did it express the CAT gene.

Fetal diagnosis of toxoplasmosis in 190 women infected during pregnancy

One hundred and ninety women who contracted toxoplasmosis after the seventh week of pregnancy underwent antenatal diagnosis, including ultrasound examination and biological tests. Tests included Toxoplasma isolation in fetal blood and amniotic fluid by mouse inoculation, specific IgM and IgA in fetal blood, and non-specific tests. Twenty fetuses had positive specific as well as non-specific tests for Toxoplasma infection. At birth, four of these presented with clinical congenital toxoplasmosis and 12 with subclinical forms. Antenatal diagnosis enabled the detection of 83 per cent of the infected fetuses. Under specific conditions, cordocentesis permits early diagnosis and considerably reduces the number of terminations of pregnancy.

Inhibition of heterologous DNA replication by the MVMp nonstructural NS-1 protein: identification of a target sequence

The nonstructural protein NS-1 of minute virus of mice (MVMp), an autonomous parvovirus, trans-inhibits the replication of a chimeric plasmid containing the SV40 origin of replication (ori) embedded in the MVMp genome. It appears that a 157-bp 5' proximal sequence of MVMp DNA is sufficient, in the presence of NS-1, to cause the inhibition of DNA replication driven by the SV40 ori placed on the same molecule. This effect is not dependent on the orientation of the MVMp target sequence and results from both a reduced level of utilization of SV40 ori and the blockage of progressing replication forks at the level of the target. Furthermore, replication driven by Epstein-Barr virus origin (oriP) is trans-inhibited by MVMp but this inhibition does not require the presence of parvoviral sequences in cis. On the basis of sequence homologies between EBV oriP and MVMp 5' terminal sequence, it is proposed that the direct or indirect interaction of NS-1 with parvovirus-like sequences present in heterologous viral and possibly also cellular genomes may result in an inhibition of DNA replication.

Immunoradiometric assay of pro-cathepsin D in breast cancer cytosol: relative prognostic value versus total cathepsin D

In breast cancer cell lines, the maturation of pro-cathepsin D into enzymatically active cathepsin D is altered, leading to its increased secretion. In order to specifically assay pro-cathepsin D (52 kD form) in breast cancer cytosol, we monitored a solid phase sandwich radioimmunoassay using D9H8 and D7E3 monoclonal antibodies raised against human pro-cathepsin D from MCF7 cells. Pro-cathepsin D was assayed in 108 primary breast cancer cytosols in which total cathepsin D was previously found to be correlated with metastasis. Pro-cathepsin D concentrations were found to be correlated with total cathepsin D and with lymph node invasion, and was slightly higher in premenopausal patients. By contrast, Cox multiparametric analysis showed that pro-cathepsin D status had no prognostic value for survival, or metastasis free survival contrary to total cathepsin D status. This first study shows the technical validity of the pro-cathepsin D assay but indicates that it has less value as a prognostic marker than total cathepsin D. This study also shows that the proportion of pro-cathepsin D recovered in vivo (1-6%) is much less than that produced in cell lines and suggests that the secreted pro-enzyme might be activated in the tumour extracellularly or following its reinternalisation.

99Tcm-methoxy-isobutyl-isonitrile SPECT to evaluate a perfusion index from regional myocardial uptake after exercise and at rest. Results of a four hour protocol in patients with coronary heart disease and in controls

In 70 patients with angiographically confirmed coronary heart disease and in 10 controls, a 4 h exercise (E) (injection of 150 MBq 99Tcm-MIBI) rest (R) (800 MBq) protocol was employed. Of these, 10 patients with 21 myocardial defects after E received a third injection 24 h after. SPECT was used to image myocardial distribution, and visual findings separated three patterns of perfusion defects after E v. R (reversible [REV], partial reversible (PREV), irreversible (IRR)). Relative regional uptake was obtained from a target-like (33 ROIs) evaluation of short-axis cuts, establishing a perfusion index (PI) by relating the defect uptake to individual maximum uptake (100%) after exercise (PIE), at rest (PIR) and the respective differences Delta PI (PIR-PIE, i.e. filling in by the second 99Tcm-MIBI injection). Visually, the sensitivity was 86% in patients or 69% in involved vessels (stenoses of greater than 33%). Vascular supply areas revealed minimal PIE values of 74.7 +/- 10.6% (control), 62.4 +/- 9.2% (REV), 46.1 +/- 7.7% (PREV) and 33.5 +/- 9.9% (IRR) (p less than 0.01). Delta PI was +13.2% or +10.1% in REV or PREV (n.s.) and +2.1% in IRR (p less than 0.01) or -0.2% in controls. PIE values did not correlate to the degree of stenosis. In areas with old myocardial infarction, the same sequence of significant decrease of PIE with reversibility occurred, independent of the patency of the supplying vessel. 33 of 35 IRR defects (94.3%) revealed PIE of less than 45%, thus predicting IRR already after the E examination. PIR values from the 4 h protocol correlated to PIR values 24 h thereafter with r = 0.94 (n = 21). 99Tcm-MIBI may be employed in a short one day E-R protocol in clinical routine. Evaluation of PI seems to be a promising tool to quantify visual defects aimed at describing the perfusional state of the terminal vascular supply area.

Methoxyisobutylisonitrile (MIBI) Tc 99m SPECT to establish a correlate to coronary flow reserve, the perfusion reserve, from global and regional myocardial uptake after exercise and rest

With 99mTc-MIBI SPECT and a 4 h exercise (E: 150 MBq iv) and rest (R; 800 MBq iv) protocol, global and regional left ventricular (LV) myocardial uptake was determined in 70 patients with angiographically confirmed coronary heart disease (CHD) and in 10 controls. The aim was to establish an E/R ratio as a correlate to coronary vascular reserve, representing perfusion reserve (PR). E/R ratios, obtained from total LV myocardium or from normal or impaired regions, were greater than 1.19 under all conditions, indicating the presence of higher flow during exercise than at rest (even in areas of low flow). Global PR separated (P less than 0.01) controls (1.63 +/- 0.21; mean +/- SD) from severely diseased patients (1.29 +/- 0.14 in 2- or 3-vessel disease) only. Improved differential diagnosis was gained from calibrating the regional E/R ratio to regional differences (E minus R) of uptake. For the left ventricle regional PRs (RPR) for 25 ROIs of the target, framing the myocardium, were determined. RPR at the regional maximum of 99mTc-MIBI uptake was similar in both controls (1.66) and patients (1.63), indicating a high probability of meeting some areas with functionally normal perfusion in patients with CHD. RPR allowed sufficient separation (P less than 0.025) concerning the degree of coronary artery stenosis (RPR in occlusion, 0.26; stenosis greater than 75%, 0.39; less than 75%, 0.56). In controls, the overall value for RPR was 1.14 +/- 0.28 (P less than 0.001). LV global PR and RPR were useful in separating patients with CHD vs controls and in classifying the severity of vascular stenosis.

Positive selection of human cells lacking several transformation parameters from an SV40-transformed culture by means of parvovirus H-1

The simian virus 40 (SV40)-transformed, newborn human kidney cell line NB-F was found to be heterogeneous with respect to its sensitivity to parvovirus H-1. The majority of the cells sustain a productive H-1 infection which eventually causes their lysis. Yet, a small fraction of the cells appears to be much less susceptible to H-1. Such a resistance to H-1 infection is a stable, transmissible property of this subpopulation of cells which was denoted NB-FR. The heterogeneity of NB-F cells is also apparent from the distribution of their karyotypes, which is bimodal and peaks at 114 and 46 chromosomes/cell. In contrast, the great majority of NB-FR cells contain 41-50 chromosomes. H-1-resistant and -sensitive cells appear to be related in several respects: they both contain morphologically human chromosomes as well as multiple SV40 DNA inserts, and could not be distinguished by isoenzyme typing. It was investigated whether the degree of sensitivity to H-1 infection correlated with other phenotypic properties of the human cell derivatives. NB-F cultures exhibit a series of transformation parameters, such as SV40 T-antigen expression, poor contact inhibition, clonogenicity in semi-solid medium and high lectin agglutinability, which are all much reduced or even undetectable in NB-FR cells. These observations suggest that cell susceptibility to H-1 segregates with marker(s) of in vitro malignant transformation. Moreover, the data indicate that parvoviruses can be used to preferentially remove transformants from a mixed culture of normal and transformed cells.

The concept of specificity in the procercoid-copepod system: Bothriocephalus claviceps (Cestoda) a parasite of the eel (Anguilla anguilla)

This paper describes experimental work on parasite specificity in the copepod-procercoid system of Bothriocephalus claviceps. Two criteria were used to characterize five potential host species Macrocyclops albidus, Macrocyclops fuscus, Eucyclops serrulatus, Acanthocyclops robustus and Macrocyclops viridis viridis. The first criterion involves susceptibility of the copepods to infection. The results show random or aggregative distributions and variable susceptibilities according to the species. We observed an ethological barrier to infection in M. viridis viridis and M. fuscus. The second criterion involves the growth and development of the procercoid. Three factors modify the profiles of the growth curves: host species, sex and intensity of infection. The growth of the procercoids is density-dependent, whereas their development is independent of density. This last characteristic is interpreted as a factor favouring the aggregation of procercoid populations. The two most susceptible hosts are M. albidus and A. robustus.

[Study of communities of Monogenea Dactylogyridae parasites of the Cyprinidae in Lake Mikri Prespa (northern Greece). Description of 3 new species from an endemic Barbus: Barbus cyclolepis prespensis Karaman, 1924]

In this paper are described 17 species of Monogenea Dactylogyridae, parasites of Cyprinidae from lake Mikri Prespa, in Greece: 14 species have been already reported in mediterranean region; 3 new species have been harvested on an endemic Barbus, B. cyclolepis prespensis, Dactylogyrus balkanicus n. sp., Dactylogyrus crivellius n. sp., Dactylogyrus prespensis n. sp. For these communities of Dactylogyrus, we discuss some problems of parasite specificity, speciation and biogeography. From the morphological types, we suggest for D. crivellius and D. prespensis an allopatric speciation and for D. balkanicus, a synxenic sympatric speciation.

[Experimental approach to the role of the paratenic host in the circulation of the parasite Bothriocephalus claviceps Goeze, 1782 (Cestoda, Pseudophyllidea)]

This article concerns an experimental work monitored in 5 species of fishes in the order to evaluate their value of paratenic hosts, in the cycle of Bothriocephalus claviceps, a parasite of the eel, Anguilla anguilla. The intestinal localisation and the lack of development of parasites are the two principal characters of this parasitism. The second character is sometimes contradicted. The effective evolution has been observed during 20 days. The more important losses of parasites coincide with the invasion of fishes. After that stage, the decrease of effectives is slower. The authors are led to consider that two modes of circulation are required for the parasite: the direct transmission and the transmission with intercalation of paratenic hosts.

Trypanosoma brucei: the extent of conversion in antigen genes may be related to the DNA coding specificity

The boundaries of gene conversion in variant-specific antigen genes have been determined in six clones of Trypanosoma brucei. In each clone, antigenic switching involved interaction between two telomeric members of the AnTat 1.1 multigene family, which share extensive homology throughout their coding regions. All conversion events occurred by substitution of faithful copies of donor sequences. Conversion endpoints were nonrandomly distributed. In four clones, the 5' conversion limit was near the antigen translation initiation codon, while in three clones, the 3' conversion limit was located at the "hinge" between the two major antigen domains. In one case, two segmental conversions were involved in antigen switching. These observations reveal that antigen gene conversion can occur without generating point mutations, and suggest that postrecombinational selection may impose a limit on the number of possible rearrangements within antigen genes.