Two mechanisms of the enhanced antibody-dependent cellular cytotoxicity (ADCC) efficacy of non-fucosylated therapeutic antibodies in human blood

<p>Abstract</p> <p>Background</p> <p>Antibody-dependent cellular cytotoxicity (ADCC) has recently been identified as one of the critical mechanisms underlying the clinical efficacy of therapeutic antibodies, especially anticancer antibodies. Therapeutic antibodies fully lacking the core fucose of the Fc oligosaccharides have been found to exhibit much higher ADCC in humans than their fucosylated counterparts. However, data which show how fully non-fucosylated antibodies achieve such a high ADCC in human whole blood have not yet been disclosed. The precise mechanisms responsible for the high ADCC mediated by fully non-fucosylated therapeutic antibodies, even in the presence of human plasma, should be explained based on direct evidence of non-fucosylated antibody action in human blood.</p> <p>Methods</p> <p>Using a human <it>ex vivo </it>B-cell depletion assay with non-fucosylated and fucosylated anti-CD20 IgG1s rituximab, we monitored the binding of the therapeutic agents both to antigens on target cells (target side interaction) and to leukocyte receptors (FcγR) on effector cells (effector side interaction), comparing the intensities of ADCC in human blood.</p> <p>Results</p> <p>In the target side interaction, down-modulation of CD20 on B cells mediated by anti-CD20 was not observed. Simple competition for binding to the antigens on target B cells between fucosylated and non-fucosylated anti-CD20s was detected in human blood to cause inhibition of the enhanced ADCC of non-fucosylated anti-CD20 by fucosylated anti-CD20. In the effector side interaction, non-fucosylated anti-CD20 showed sufficiently high FcγRIIIa binding activity to overcome competition from plasma IgG for binding to FcγRIIIa on natural killer (NK) cells, whereas the binding of fucosylated anti-CD20 to FcγRIIIa was almost abolished in the presence of human plasma and failed to recruit NK cells effectively. The core fucosylation levels of individual serum IgG1 from healthy donors was found to be so slightly different that it did not affect the inhibitory effect on the ADCC of fucosylated anti-CD20.</p> <p>Conclusion</p> <p>Our results demonstrate that removal of fucosylated antibody ingredients from antibody therapeutics elicits high ADCC in human blood by two mechanisms: namely, by evading the inhibitory effects both of plasma IgG on FcγRIIIa binding (effector side interaction) and of fucosylated antibodies on antigen binding (target side interaction).</p

Grain size distributions of radiocesium and Plutonium activity concentration in sediments collected off the Niida River estuary (新田川河口沖の堆積物中の粒径別の放射性セシウムとプルトニウム濃度)

After the accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) happened in March 2011, large amounts of radionuclides released from the FDNPS into the terrestrial and marine environments. The total amounts of 134Cs and 137Cs released from the accident were estimated as 18 PBq and 15 PBq, respectively. In contrast, those of 238Pu, 239Pu and 240Pu amounts were estimated as 0.0019 PBq, 0.0000032 PBq and 0.0000032 PBq and these amounts were not many compared to abundance before the accident (Report of Japan government to the IAEA Ministerial Conference on Nuclear safety, 2011). Based on the Pu atom ratio, it was estimated that the release of Pu from the accident was negligible in the marine environment (Bu et al., 2015). However, previous reports focused on the river (Evard et al., 2014) and offshore area (e.g. Zheng et al., 2012, Bu et al., 2013, 2015a,b) and the lack of information on the distribution and behavior of plutonium in the estuarine area hampered the understanding of the process of radionuclide transport from river to ocean. 　In this study, the Niida River estuary was focused on, because the upstream portion of this river is located in Iidate Village, which was an area of high radiocaeasium deposition from the accident. We discussed temporal and vertical distributions of radiocaeasium and plutonium based on the results of the radiocesium (134Cs, 137Cs) and plutonium (239Pu, 240Pu, 241Pu) activity concentrations and plutonium atom ratios (240Pu/239Pu, 241Pu/239Pu) according to grain size in sediments.　Sediment core samples at three monitoring stations (NR1: 37°39\u27 N, 141°04\u27 E, water depth: 25 m, NR2: 37°41\u27 N, 141°09\u27 E, water depth: 30 m, NR4: 37°38\u27 N, 141°08\u27 E, water depth: 35 m) were collected in mid-October 2013. Collected sediment cores were cut into 1 cm thick slices and dried. Then, the dried sediments were separated into four classes, based on grain sizes, using several mesh sizes: granules (grain size larger than 2 mm); very coarse to coarse sand particles (1-2 mm); coarse to very fine sand particles (0.063-1 mm); and silt to clay particles (smaller than 0.063 mm). Radiocesium (134Cs and 137Cs) activities were measured for each grain size class using high-purity gamma ray spectrometry and then corrected to the sampling date. Plutonium (239Pu, 240Pu and 241Pu) were extracted and concentrated based on Wang et al. (2017) and measured using SF-ICP-MS (Zheng et al., 2006; Zheng, 2015). 　Fractions for the classes of granules, very coarse sand, coarse to very fine sand, silt to clay particles were: 0.0-35%, 0.013-35%, 38-99%, and 0.0-29%, respectively. The fractions for coarse to very fine sand particles represented more than 70% of the total particle amount for each sediment layer and the highest fractions were obtained at NR1 and NR2, which are located northward from the river estuary. In contrast, fractions for granules and very coarse sand particle at NR4, which is located in an area of the same latitude as the river estuary, were relatively high and the total fraction for these particles ranged from 20-62 %. The 137Cs activities for very coarse sand, coarse to very fine sand, and silt to clay particles were in the ranges of 2.8-14 Bq/kg-dry, 4.1-751 Bq/kg-dry, and 731-837 Bq/kg-dry, respectively, and these activity concentrations tended to be higher with decreasing grain size. However, the profile patterns for the sand particles and silt to clay particles fraction were similar. 　In this presentation, we also report the results of grain-size distributions of Pu activity concentration and Pu atom ratio. This work was partially supported by Grants-in-Aid for Scientific Research on Innovative Areas, the Ministry of Education Culture, Sports, Science and Technology (MEXT), Japan (Nos. 24110004, 24110005), the JSPS KAKENHI (grant number JP17k00537) and Research and Development to Radiological Sciences in Fukushima Prefecture.JPGU-AGU Joint Meeting 201

Radiocaesium activity concentrations in overlying water collected off the coast of Fukushima Prefecture in 2014-2016 (福島県沖の堆積物と直上水中の放射性セシウム濃度分布)

After the accident at the Fukushima Dai-ichi Nuclear Power Station happened in March 2011, large amounts of radionuclides were dispersed by hydrogen explosions, and radionuclides also leaked from the FDNPS into the terrestrial and marine environments. In the seawater, Cs mainly exists in a dissolved state and parts of particulate radiocaesium have settled to seafloor. Radiocaesium accumulated in sediment have partly re-suspended as particulate form and re-eluted as dissolved form due to several factors such as bottom current and deformation. In this study conducted using dissolved radiocaesium activities in trapped water (~30 cm over seafloor) on sediment at thirteen stations collected using Multiple Corer, which is considered as overlying water, collected off the coast of Fukushima Prefecture in 2014-2017. Collected overlying waters were filtered through 0.45 μm and 0.20 μm pore sizes filter and these filtrate water was regarded as F1 and F2 fraction, respectively. Radiocaesium in the filtered overlying water was concentrated by the ammmonium phosphomolybdate (AMP) adsorption method (Aoyama and Hirose, 2008) and were measured using high-purity Ge-detector. Based on corrected sampling date 137Cs activity concentration in overlying water, we firstly performed F-test to confirm the equal variance as follow two topics: i) between F1 and F2 fractions at each station ii) between within 10 km and outside 10 km from the east coast of Japan. 137Cs activity concentrations in samples showing equal variance were also calculated by the t-test and we confirmed which of these activity concentrations had significant differences or not. Samples that not showed equal variance were verified by the Wilcoxon signed-rank test to confirm whether or not there was a significant difference (P <0.05 level). In overlying water, the dissolved 137Cs activity concentrations about F1 and F2 fractions were 2.3-27 mBq/L and 2.4-31 mBq/L, respectively. In 2014-2017, 137Cs activity between F1 and F2 fractions had not significant differences in all sampling periods. Thus, the dissolved 137Cs in overlying water generally exist as less than 0.2μm grain size. In both F1 and F2 fractions, the 137Cs activity concentrations between within 10 km and outside 10 km from the east coast of Japan had not significant differences.2018 Oean Science meetin

Factors controlling 134Cs activity concentrations in sediment collected off the coast of Fukushima Prefecture in 2013-2015

To elucidate the activity concentration and behavior of radiocaesium, we observed the spatial and vertical distributions of radiocaesium in sediment collected at 12 monitoring stations off the coast of Fukushima Prefecture in 2013-2015. In bulk surface-layer sediment (core depth: 0-3 cm), high 134Cs activity concentrations were observed at stations around the water depth of 100 m, where the sediment was rich in silt to clay particles and organic matter. The activity concentrations generally decreased with increasing core depth and the extent of the decrease was different between the stations. The difference trend for temporal change of 134Cs activity concentrations between the two zones of off Onahama and within 30 km of the FDNPS was partly attributed to the mobility of sediment particles reflecting water content, porosity and permeability. At some stations, shaped peaks for activity concentrations were temporarily observed in upper-layer sediment (core depth: 0-1 cm) or sediment below that. The 134Cs activity concentrations in the surface-layer sediment were not always accompanied by an increase in the contribution from fine (i.e., silt to clay) particle-bound 134Cs in the sediment. In October 2014, sediment collected at a station about 1.5 km from FDNPS was found to have broad 134Cs peaks in the middle-layer sediment (core depth: 5-16 cm). In this middle-layer sediment, both sand and silt to clay fractions contributed to the increased 134Cs activity concentrations. On the other hand, such broad peaks were not found in October 2015. These results suggest that the activity concentrations in sediment had changed significantly by a complicated process of sediment mixing, erosion or re-sedimentation that affected the broad peak for the activity concentration in the middle-layer sediment

Dissolved radiocaesium in seawater off the coast of Fukushima during 2013-2015

To discuss the factors influencing radiocaesium distributions and its variation in the marine environment, dissolved radiocaesium was measured in seawater samples collected off the coast of Fukushima Prefecture during 2013-2015. The 137Cs activity concentrations in the surface-layer seawater at NPE2, NP0, NP2, NPE1, AN7, I01, E and A stations, which are located within about 10 km from the east coast of Japan, were higher than those at other stations. These high activity concentrations seem to be affected by several factors, including increased river input or contaminated water input from the Fukushima Dai-ichi Nuclear Power Station due to heavy rain events