IMMU-12. Exploring and modulating the tumour immune microenvironment to facilitate the selection of immunotherapies for paediatric-type diffuse high-grade glioma

Immune cells have the potential to selectively eradicate high-risk brain tumours such as paediatric-type diffuse high-grade glioma (PDHGG). We aim to characterize the tumour immune microenvironment (TIME) of intra-cranial syngeneic mouse models of diffuse hemispheric glioma, H3G34 (DHG-H3G34) and diffuse midline glioma, H3K27 (DMG-H3K27). We also demonstrate how an oncolytic reovirus (Reolysin) can “heat-up” the TIME of our syngeneic models. Orthotopic immunocompetent mouse models of DHG-H3G34 (C57BL/6, NRASG12V + shp53 + shATRX +/- H3.3G34R) and DMG-H3K27 (Nestin-Tv-a/p53fl/fl, RCAS-ACVR1R206H + RCAS-H3.1K27M) were profiled using single-cell RNA-sequencing (scRNA-seq) (10x genomics), a 22-colour custom flow cytometry immune panel and spatial transcriptomics. Differential marker expression was validated with immunohistochemistry and immunofluorescence in tissue sections. Syngeneic mouse tumours treated systemically with Reolysin were also profiled to evaluate the effects of the oncolytic virus on the TIME. Cell type predictions in scRNA-seq using singleR, ssGSEA and expression of individual marker genes suggested that the predominant immune cell types within hemispheric tumours were monocytes (11-21%) and macrophages (10-19%) with much smaller proportions of CD4+ and CD8+ T-cells (4-10%). By contrast, much smaller proportions of monocytes (2%) and macrophages (3%) were observed in the H3.1K27M pontine model. Flow cytometry, immunohistochemistry and immunofluorescence validated scRNA-seq immune profiles and characterised signalling of the PD-1/PD-L1 checkpoint pathway. Spatial transcriptomics allowed immune cell populations to be positioned within tumour sections and showed significant co-localization of CD4+ and CD8+ lymphocytes at tumour margins. Treatment of syngeneic mouse tumours with Reolysin resulted in reduced tumour volumes and altered the TIME, in particular increasing cytotoxic T-cell tumour infiltration. Our results highlight immunological heterogeneity within molecular subgroups of PDHGG and demonstrate ability of a systemically delivered oncolytic virus, Reolysin, to “heat-up” the TIME, contributing to a more immune actionable profile. Future work will help to identify optimal combinations for the next generation of immunotherapies in PDHGG.

Niche Overlap and Network Specialization of Flower-Visiting Bees in an Agricultural System

Different resource use strategies manifest as differences in the realized niches of species. Niche segregation may involve several dimensions of the niche, such as diet, space, and time. We measured the level of redundancy and complementarity of a bee-plant interaction network in an agricultural system. Because flower resource diversity is high and resource abundance associated with flowering phenology varies throughout the year, we hypothesized that trophic overlap in the community would be low (i.e., high niche complementarity). In contrast, we expected a combination of physiological constraints and exploitation competition to create high temporal overlap, leading to high redundancy in the time of use of floral resources. Dietary overlap was low (NOih = 0.18): niches of 88% of species pairs had less than 30% overlap. In contrast, temporal overlap was intermediate (NOih = 0.49): niches of 65% of species pairs had 30% to 60% overlap. Network analysis showed that bees separated their dietary niches and had intermediate complementary specialization (H2' = 0.46). In terms of their temporal niches (H2' = 0.12), bees were generalists, with high temporal redundancy. Temperature was not a key factor in the determination of niche overlap, suggesting that environmental factors do not likely have a primary role in determining high redundancy in the temporal use of floral resources. Rather, temporal overlap is likely associated with the timing of nectar production by flowers. Our results suggest that bees partition a wide variety of available floral resources, resulting in low dietary overlap and intermediate temporal overlap.

Biannual fluoride varnish applications and caries incidence in preschoolers: a 24-month follow-up randomized placebo-controlled clinical trial

Sound evidence on the effectiveness of fluoride varnishes (FV) to reduce caries incidence in preschool children is lacking.

OBJECTIVE

To assess whether the application of FV in preschool children at 6-month intervals decreases the incidence of caries and produces any adverse effects.

METHODS

A randomized, examiner- and patient-blind, placebo-controlled, parallel-group design, clinical trial, comprising 1- to 4-year-old children, 100 in each group (FV or placebo varnish, PV), was conducted in Rio de Janeiro, Brazil. Two trained pediatric dentists performed the clinical examinations (kappa = 0.85). Dental caries was recorded at the d2 (cavitated enamel) and d3 (dentine) levels using the International Caries Diagnosis and Assessment System.

RESULTS

At baseline, the mean age of the participants was 2.4 years (SD 0.9) and the mean d3mfs was 0.8 (SD 1.9). Most of the children brushed their teeth with fluoride toothpaste and consumed fluoridated tap water. After 24 months, 89 and 92 children of the test and the control groups were analyzed, respectively. A total of 32 (35.9%) children in the FV group and 43 (46.7%) in the PV group presented new dentine caries lesions (χ(2) test; p = 0.14), showing relative and absolute risk reductions of 23% (95% CI: -9.5 to 45.9) and 11% (95% CI: -3.5 to 25.0). The mean caries increment differences between the test and control groups were -0.8 (95% CI: -2.0 to 0.4) at the d2 level and -0.7 (95% CI: -1.9 to 0.4) at the d3 level. Only 2 minor complaints regarding the intervention were reported.

CONCLUSION

Although safe and well accepted, twice-yearly professional FV application, during 2 years, did not result in a significant decrease in caries incidence.

Microbiological epidemiological history of meningococcal disease in Rio de Janeiro, Brazil

The main objectives of the present study were to investigate the clinical and laboratory features of meningococcal disease in the city of Rio de Janeiro, Brazil, during the overlap of 2 epidemics in the 1990s. We conducted a study of a series of cases of meningococcal disease admitted in a Meningitis Reference Hospital. All clinical isolates available were analyzed by means of microbiological epidemiological markers. In 1990, Neisseria meningitidis serogroup B:4,7:P1.19,15, 1.7,1 sulfadiazine-resistant of the ET-5 complex emerged causing epidemic disease. Despite mass vaccination campaign (VaMengoc B+C®), the ET-5 clone remained hyperendemic after the epidemic peaked. In 1993 to 1995, an epidemic of serogroup C belonged to the cluster A4 overlapped, with a significant shift in the age distribution toward older age groups and an increase of sepsis. Serogroup C epidemics are a recurrent problem in Rio de Janeiro, which can be hindered with the introduction of a conjugate vaccine. We hope the data presented here brings useful information to discuss vaccines strategies and early management of suspected cases.