Potentialisation de la réponse immunitaire anti-tumorale par le cyclophosphamide

À ce jour, il est connu que le succès des traitements chimiothérapeutiques, outre l’effet cytotoxique direct sur les cellules tumorales, repose sur la contribution du système immunitaire. Nos travaux de recherche montrent que le traitement au cyclophosphamide de souris DBA/2 porteuses du mastocytome P815 induit le rejet de la tumeur, ainsi qu’une protection à long terme, de façon dépendante de la présence des lymphocytes T CD4+ et CD8+. De plus, le rejet du mastocytome P815 corrèle avec une augmentation de l’infiltration au sein de la tumeur de lymphocytes T CD8+ spécifiques d’un antigène muté. Lors de ce travail, nous avons tenté d’identifier les mécanismes moléculaires et cellulaires impliqués dans le rejet du mastocytome P815 induit suite à un traitement au cyclophosphamide. Dans ce but, les lymphocytes T CD8+ spécifiques de l’antigène muté, infiltrant un mastocytome P815 en progression ou en régression (suite à un traitement au cyclophosphamide), ont été analysés afin de mettre en évidence des caractéristiques phénotypiques et/ou fonctionnelles associées à ces populations de cellules T CD8+. Le traitement au cyclophosphamide conduit à l’infiltration de lymphocytes T CD8+ effecteurs en phase terminale de différenciation (KLRG1+ CD27- Eomes+ Perforin+) au sein de la tumeur, alors que les lymphocytes T CD8+ présents dans le microenvironnement tumoral du mastocytome P815 en progression possèdent un phénotype de cellules dysfonctionnelles (PD-1+ LAG-3+ Ki67-). Les IFN-I sont impliqués, au moins partiellement, dans l’acquisition du phénotype effecteur des cellules puisque leur inhibition entraine une augmentation de l’expression du récepteur PD-1.Ces résultats amènent à une meilleure compréhension des mécanismes par lesquels le cyclophosphamide régule l’amplitude et la qualité des réponses immunes spécifiques de la tumeur. Outre un effet quantitatif qui se traduit par l’expansion et l’infiltration dans la tumeur de lymphocytes T CD8+ spécifiques de l’antigène muté, cet agent chimiothérapeutique contribue au rejet du mastocytome P815 en favorisant le développement de lymphocytes T CD8+ effecteurs. La compréhension des effets immunomodulateurs d’un traitement chimiothérapeutique présente un intérêt majeur pour l’amélioration des thérapies en oncologie, tant en ce qui concerne l’immunothérapie que les combinaisons de traitement.An important question is how chemotherapy may (re-)activate tumor-specific immunity. In this study, we provide a phenotypic, functional and genomic analysis of tumor-specific CD8+ T cells in tumor (P815)-bearing mice, treated or not with cyclophosphamide. Our data show that chemotherapy favors the development of effector-type lymphocytes in tumor bed, characterized by higher KLRG-1 expression, lower PD-1 expression and increased cytotoxicity. This suggests re-engagement of T lymphocytes into the effector program since most T cells are dysfunctional in the tumor microenvironment before cyclophosphamide treatment. IFN-I appears involved in this remodelling. Our findings provide some insight into how cyclophosphamide regulates the amplitude and quality of tumor-specific immune responses.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

L’immunothérapie au service de la chimiothérapie, de nouvelles avancées

De nombreuses évidences expérimentales obtenues ces dernières années mettent en évidence le rôle majeur de l’immunosurveillance des tumeurs. Le système immunitaire reconnaît les tumeurs et peut provoquer leur rejet, mais il est freiné par des mécanismes d’échappement induits par la tumeur elle-même. De façon intéressante, l’efficacité de la chimiothérapie semble dépendre de la réponse immunitaire qui est elle-même potentialisée par les traitements chimiques, créant une boucle de rétroaction positive qui peut conduire à une résistance antitumorale à long terme. Dans cette revue, nous résumons certains mécanismes créant une synergie entre chimio- et immunothérapie

Nationwide Harmonization Effort for Semi-Quantitative Reporting of SARS-CoV-2 PCR Test Results in Belgium

From early 2020, a high demand for SARS-CoV-2 tests was driven by several testing indications, including asymptomatic cases, resulting in the massive roll-out of PCR assays to combat the pandemic. Considering the dynamic of viral shedding during the course of infection, the demand to report cycle threshold (Ct) values rapidly emerged. As Ct values can be affected by a number of factors, we considered that harmonization of semi-quantitative PCR results across laboratories would avoid potential divergent interpretations, particularly in the absence of clinical or serological information. A proposal to harmonize reporting of test results was drafted by the National Reference Centre (NRC) UZ/KU Leuven, distinguishing four categories of positivity based on RNA copies/mL. Pre-quantified control material was shipped to 124 laboratories with instructions to setup a standard curve to define thresholds per assay. For each assay, the mean Ct value and corresponding standard deviation was calculated per target gene, for the three concentrations (107, 105 and 103 copies/mL) that determine the classification. The results of 17 assays are summarized. This harmonization effort allowed to ensure that all Belgian laboratories would report positive PCR results in the same semi-quantitative manner to clinicians and to the national database which feeds contact tracing interventions.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Nationwide Harmonization Effort for Semi-Quantitative Reporting of SARS-CoV-2 PCR Test Results in Belgium

From early 2020, a high demand for SARS-CoV-2 tests was driven by several testing indications, including asymptomatic cases, resulting in the massive roll-out of PCR assays to combat the pandemic. Considering the dynamic of viral shedding during the course of infection, the demand to report cycle threshold (Ct) values rapidly emerged. As Ct values can be affected by a number of factors, we considered that harmonization of semi-quantitative PCR results across laboratories would avoid potential divergent interpretations, particularly in the absence of clinical or serological information. A proposal to harmonize reporting of test results was drafted by the National Reference Centre (NRC) UZ/KU Leuven, distinguishing four categories of positivity based on RNA copies/mL. Pre-quantified control material was shipped to 124 laboratories with instructions to setup a standard curve to define thresholds per assay. For each assay, the mean Ct value and corresponding standard deviation was calculated per target gene, for the three concentrations (107, 105 and 103 copies/mL) that determine the classification. The results of 17 assays are summarized. This harmonization effort allowed to ensure that all Belgian laboratories would report positive PCR results in the same semi-quantitative manner to clinicians and to the national database which feeds contact tracing interventions.0info:eu-repo/semantics/publishe

Two Separate Clusters of SARS-CoV-2 Delta Variant Infections in A Group of 41 Students Travelling from India: An Illustration of the Need for Rigorous Testing and Quarantine

We report two clusters of SARS-CoV-2 B.1.617.2 (Delta variant) infections in a group of 41 Indian nursing students who travelled from New Delhi, India, to Belgium via Paris, France. All students tested negative before departure and had a second negative antigen test upon arrival in Paris. Upon arrival in Belgium, the students were quarantined in eight different houses. Four houses remained COVID-free during the 24 days of follow-up, while all 27 residents of the other four houses developed an infection during quarantine, including the four residents who were fully vaccinated and the two residents who were partially vaccinated. Genome sequencing revealed two distinct clusters affecting one and three houses, respectively. In this group of students, vaccination status did not seem to prevent infection nor decrease the viral load. No severe symptoms were reported. Extensive contact tracing and 3 months of nationwide genomic surveillance confirmed that these outbreaks were successfully contained and did not contribute to secondary community transmission in Belgium. These clusters highlight the importance of repeated testing and quarantine measures among travelers coming from countries experiencing a surge of infections, as all infections were detected 6 days or more after arrival.0SCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe

PHD2 Constrains Antitumor CD8+ T-cell Activity.

The prolyl hydroxylase domain/hypoxia-inducible factor (PHD/HIF) pathway has been implicated in a wide range of immune and inflammatory processes, including in the oxygen-deprived tumor microenvironment. To examine the effect of HIF stabilization in antitumor immunity, we deleted Phd2 selectively in T lymphocytes using the cre/lox system. We show that the deletion of PHD2 in lymphocytes resulted in enhanced regression of EG7-OVA tumors, in a HIF-1α-dependent manner. The enhanced control of neoplastic growth correlated with increased polyfunctionality of CD8+ tumor-infiltrating lymphocytes, as indicated by enhanced expression of IFNγ, TNFα, and granzyme B. Phenotypic and transcriptomic analyses pointed to a key role of glycolysis in sustaining CTL activity in the tumor bed and identified the PHD2/HIF-1 pathway as a potential target for cancer immunotherapy.info:eu-repo/semantics/publishe

Molecular profiling of CD8 T cells in autochthonous melanoma identifies Maf as driver of exhaustion.

T cells infiltrating neoplasms express surface molecules typical of chronically virus-stimulated T cells, often termed "exhausted" T cells. We compared the transcriptome of "exhausted" CD8 T cells infiltrating autochthonous melanomas to those of naïve and acutely stimulated CD8 T cells. Despite strong similarities between transcriptional signatures of tumor- and virus-induced exhausted CD8 T cells, notable differences appeared. Among transcriptional regulators, Nr4a2 and Maf were highly overexpressed in tumor-exhausted T cells and significantly upregulated in CD8 T cells from human melanoma metastases. Transduction of murine tumor-specific CD8 T cells to express Maf partially reproduced the transcriptional program associated with tumor-induced exhaustion. Upon adoptive transfer, the transduced cells showed normal homeostasis but failed to accumulate in tumor-bearing hosts and developed defective anti-tumor effector responses. We further identified TGFβ and IL-6 as main inducers of Maf expression in CD8 T cells and showed that Maf-deleted tumor-specific CD8 T cells were much more potent to restrain tumor growth in vivo. Therefore, the melanoma microenvironment contributes to skewing of CD8 T cell differentiation programs, in part by TGFβ/IL-6-mediated induction of Maf

SARS-CoV-2 Transmission in Belgian French-Speaking Primary Schools: An Epidemiological Pilot Study

Schools have been a point of attention during the pandemic, and their closure one of the mitigating measures taken. A better understanding of the dynamics of the transmission of SARS-CoV-2 in elementary education is essential to advise decisionmakers. We conducted an uncontrolled non-interventional prospective study in Belgian French-speaking schools to describe the role of attending asymptomatic children and school staff in the spread of COVID-19 and to estimate the transmission to others. Each participant from selected schools was tested for SARS-CoV-2 using a polymerase chain reaction (PCR) analysis on saliva sample, on a weekly basis, during six consecutive visits. In accordance with recommendations in force at the time, symptomatic individuals were excluded from school, but per the study protocol, being that participants were blinded to PCR results, asymptomatic participants were maintained at school. Among 11 selected schools, 932 pupils and 242 school staff were included between January and May 2021. Overall, 6449 saliva samples were collected, of which 44 came back positive. Most positive samples came from isolated cases. We observed that asymptomatic positive children remaining at school did not lead to increasing numbers of cases or clusters. However, we conducted our study during a period of low prevalence in Belgium. It would be interesting to conduct the same analysis during a high prevalence period

Investigation of an international water polo tournament in Czechia as a potential source for early introduction of the SARS-CoV-2 Omicron variant into Belgium, Switzerland and Germany, November 2021.

BackgroundThe earliest recognised infections by the SARS-CoV-2 Omicron variant (Pango lineage B.1.1.529) in Belgium and Switzerland suggested a connection to an international water polo tournament, held 12-14 November 2021 in Brno, Czechia.AimTo study the arrival and subsequent spread of the Omicron variant in Belgium and Switzerland, and understand the overall importance of this international sporting event on the number of infections in the two countries.MethodsWe performed intensive forward and backward contact tracing in both countries, supplemented by phylogenetic investigations using virus sequences of the suspected infection chain archived in public databases.ResultsThrough contact tracing, we identified two and one infected athletes of the Belgian and Swiss water polo teams, respectively, and subsequently also three athletes from Germany. In Belgium and Switzerland, four and three secondary infections, and three and one confirmed tertiary infections were identified. Phylogenetic investigation demonstrated that this sporting event played a role as the source of infection, but without a direct link with infections from South Africa and not as a superspreading event; the virus was found to already be circulating at that time in the countries involved.ConclusionThe SARS-CoV-2 Omicron variant started to circulate in Europe several weeks before its identification in South Africa on 24 November 2021. Accordingly, it can be assumed that travel restrictions are usually implemented too late to prevent the spread of newly detected SARS-CoV-2 variants to other regions. Phylogenetic analysis may modify the perception of an apparently clear result of intensive contact tracing.SCOPUS: ar.jinfo:eu-repo/semantics/publishe