Characterisation of TbSmee1 suggests endocytosis allows surface-bound cargo to enter the trypanosome flagellar pocket

All endocytosis and exocytosis in the African trypanosome Trypanosoma brucei occurs at a single subdomain of the plasma membrane. This subdomain, the flagellar pocket, is a small vase-shaped invagination containing the root of the single flagellum of the cell. Several cytoskeleton-associated multiprotein complexes are coiled around the neck of the flagellar pocket on its cytoplasmic face. One of these, the hook complex, was proposed to affect macromolecule entry into the flagellar pocket lumen. In previous work, knockdown of T. brucei (Tb)MORN1, a hook complex component, resulted in larger cargo being unable to enter the flagellar pocket. In this study, the hook complex component TbSmee1 was characterised in bloodstream form T. brucei and found to be essential for cell viability. TbSmee1 knockdown resulted in flagellar pocket enlargement and impaired access to the flagellar pocket membrane by surface-bound cargo, similar to depletion of TbMORN1. Unexpectedly, inhibition of endocytosis by knockdown of clathrin phenocopied TbSmee1 knockdown, suggesting that endocytic activity itself is a prerequisite for the entry of surface-bound cargo into the flagellar pocket.

POS1214 THE DYNAMICS OF INFLAMMATORY MARKERS IN COVID-19 PATIENTS TREATED WITH LEVILIMAB

Background:

Levilimab (LVL) is a novel anti-IL6Rmonoclonal antibody against IL6Rα. Cytokine release syndrome plays the key role in the pathogenesis of a range of life-threatening conditions including the acute respiratory distress syndrome in severely ill COVID-19 patients. Thus, the use of LVL could be considered as anti-cytokine therapy with a potency to prevent the complications and progression of respiratory failure in COVID-19.

Objectives:

We analyzed the changes in the serum concentrations of inflammatory markers (Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and IL-6) in patients treated with LVL or placebo as part of a phase III multicenter randomized double-blind placebo-controlled adaptive-design CORONA clinical study aimed to evaluate the efficacy and safety of LVL in subjects with severe COVID-19 (NCT04397562).

Methods:

A total of 217 patients were enrolled in the study, 206 patients were randomized, and 204 patients received the investigational product (IP, LVL or placebo).

Study included men and non-pregnant women aged ≥18 years, hospitalized for severe COVID-19 pneumonia, receiving standard therapy according to the national guidelines. Patients with acute respiratory failure with the need in invasive respiratory support, septic shock, multiple organ failure or life expectancy less than 24 hours could not participate in the study. The use of other monoclonal antibodies and glucocorticoids for the treatment of COVID-19 were not allowed.

Subjects were stratified according to the CRP level (CRP ≤ 7 mg/L; CRP > 7 mg/L) and then randomized (1:1) into 2 groups to receive LVL 324 mg or placebo. LVL/placebo were administered as a single subcutaneous injection, investigator and patients were unaware of the received therapy.

Among secondary endpoints of the study changes from baseline in ESR, CRP and IL-6 concentrations were assessed. CRP level and ESR were measured before the IP administration and on Days 3, 5, 7, 14, 21, 29 and 30. Blood samples for the measurement of IL-6 concentration were obtained before the IP administration and then every day for 2 weeks after administration.

Results:

We observed the pronounced decrease of ESR in LVL group compared to Placebo group. The difference was statistically significant on Days 3 and 7: the median ESR change from baseline was -3 mm/h and +3 mm/h on Day 3, -11 mm/h and -3.1 mm/h on Day 7, in LVL and Placebo groups, respectively (p=0.0319 and p=0.0110, Days 3 and 7). The statistically significant difference in the change of CRP level was detected between the groups on Day 3: -26.6±41.9 mg/L and -19.2±58.2 mg/L in LVL and Placebo groups, respectively (p=0.0241). Numerically the same dynamics of ESR and CRP was observed over entire study period.

The dynamics of IL-6 serum concentrations in LVL and Placebo groups was strikingly different. After LVL administration we detected the rapid significant increase in IL-6 concentration due to IL-6 receptors inhibition. Maximum change from baseline was observed on Day 3 (+91.9±117.7 pg/mL), on Day 14 the value was +31.9±62.7 pg/mL.

In the Placebo group, the IL-6 concentration increased slightly until Day 4 (+5,1±76,5 pg/mL), and then decreased significantly (-39.2±55.1 pg/mL on Day 14) due to clinical improvement in this group.

Conclusion:

The significant differences in the dynamics of ESR, CRP and IL-6 after LVL administration compared to placebo confirmed the pharmacodynamic effect and its potency to prevent the excessive release of inflammatory substances in severely ill COVID-19 patients.

References:

[1]Xu X, Han M, Li T, Sun W, Wang D, Fu B, Zhou Y, Zheng X, Yang Y, Li X, Zhang X, Pan A, Wei H. Effective treatment of severe COVID-19 patients with tocilizumab. Proc Natl Acad Sci U S A. 2020 May 19;117(20):10970-10975. doi: 10.1073/pnas.2005615117. Epub 2020 Apr 29. PMID: 32350134; PMCID: PMC7245089.

Acknowledgements:

We thank all contributors to the CORONA study.

Disclosure of Interests:

Nikita Lomakin: None declared, Bulat Bakirov: None declared, Gaziiavdibir Musaev: None declared, Denis Protsenko: None declared, Olga Moiseeva: None declared, Elena Pasechnik: None declared, Vladimir Popov: None declared, Elena Smolyarchuk: None declared, Ivan Gordeev: None declared, Michail Gilyarov: None declared, Daria Fomina: None declared, V Mazurov: None declared, Maria Morozova Employee of: JSC BIOCAD, Ekaterina Dokukina Employee of: JSC BIOCAD, Dmitrii Bogdan Employee of: JSC BIOCAD, Anton Lutskii Employee of: JSC BIOCAD, Arina Zinkina-Orihan Employee of: JSC BIOCAD, Iulia Linkova Employee of: JSC BIOCAD, Anton Seleznev Employee of: JSC BIOCAD.

Heterogeneity of 90Sr radioactive contamination at the head part of the East Ural radioactive trace (EURT)

1: We measured ⁹⁰Sr concentrations and beta particle flux density (BPFD) in 44 soil samples collected from four soil profiles across a central transect on the head of the East Ural Radioactive Trace (EURT). The relationship between BPFD and ⁹⁰Sr concentration of each soil sample can be characterised by a linear regression model; ⁹⁰Sr concentration in the upper 12 cm soil layer can thus be assessed by measuring BPFD in the soil surface. 2: The BPFD on the soil surface was measured at 969 points at seven sites with linear dimensions ranging from 140 × 20 m to 140 × 320 m. The correspondence of ⁹⁰Sr concentration in the 12 cm soil layer with its BPFD value was calculated for each of these seven sites. Eighty (80) % of ⁹⁰Sr concentration measurements in the 12 cm soil layer in each model site differed by a factor of 2.0-5. The variability of ⁹⁰Sr concentration increased significantly in the 12 cm upper soil layer over territories with visual features of landscape disturbance (pits, trenches). The ratio of maximum to minimum concentration of ⁹⁰Sr varied from 6.1 to 6.6 in the 12 cm soil layer over territories without visual features of anthropogenic soil disturbance. 3: The ⁹⁰Sr concentration was measured in the skeletons of 34 juvenile Microtus oeconomus individuals weighing less than 12.5 g and trapped at the four model sites in July. The assessment of ⁹⁰Sr concentration in the 12 cm soil layer was conducted for each point where an animal was trapped. The relationship between ⁹⁰Sr concentration in soil and in the skeleton was characterised by a linear regression model with a determination coefficient of 0.51. 4: The concentration ratio for ⁹⁰Sr from soil to skeleton (CR_{skeleton-soil}) was 2.0 ± 0.1 for M. oeconomus over the territory of the EURT, which is consistent with the minimum value of the same CR_{skeleton-soil} for M. oeconomus from the Chernobyl area (Chesser et al., 2000).

Geogenic and anthropogenic impacts on indoor radon in the Techa River region

Indoor radon concentration was studied in the 14 settlements located near the Techa River, which was contaminated by radioactive wastes in 1950-s. Results of the radon survey were used for analysis of the relationship between the indoor radon and main geologic factors (Pre-Jurassic formations, Quaternary sediments and faults), local geogenic radon potential and anthropogenic factors. Main influencing factors explain 58% of the standard deviation of indoor radon concentration. Association of the air exchange influence over radon concentration with underlying geological media was related to different contributions of geogenic advective and diffusive radon entries. The properties of geological formation to transfer radon gas in interaction with the house can be considered within the radon geogenic potential concept. The study of the radon exposure of the Techa River population can be used to estimate the contribution of natural radon to the overall radiation exposure of the local population during the period of radioactive waste discharges.