Objective To investigate the binding and carrying effects of human serum albumin(HSA)from various sources on sphingosine-1-phosphate(S1P).Methods Utilizing human plasma-derived HSA(pHSA)and recombinant HSA(rHSA)samples as the focal points of our investigation,LC-MS/MS technology was employed to meticulously compare and an-alyze the disparities in S1P content among the aforementioned samples.Subsequently,under physiological concentration condi-tions,S1P was directly introduced to HSA samples for loading processing,facilitating a comprehensive comparison of the bind-ing efficacy of HSA from different sources to S1P.Within a serum-free culture setting,HSA samples from various sources were co-cultured with HUVEC cells.The alterations in S1P content within the cell culture supernatant across different treatment groups were meticulously analyzed,allowing for a nuanced comparison of the S1P carry effects exerted by HSA from different sources on cells.The interaction between HSA and S1P molecules from different sources was analyzed and their affinity was cal-culated using surface plasmon resonance(SPR)technology.Furthermore,leveraging AutoDock Vina software and the Mol-prophet platform,the molecular docking analysis of HSA and S1P was conducted,aiming to predict the key binding pocket do-main of S1P within HSA.Results All pHSA samples exhibited detectable levels of S1P(ranging from 3.31±0.03 to 30.35±0.07 μg/L),with significant variations observed among pHSA samples from different manufacturers(P＜0.001).Conversely,S1P was undetectable in all rHSA samples.Upon load treatment,the binding affinity of HSA from diverse sources to S1P dem-onstrated significant discrepancies(P＜0.001),with rHSA exhibiting approximately double the average S1P loading compared to pHSA(ΔCrHSA=801.75±142.45 μg/L vs ΔCpHSA=461.94±85.73 μg/L;P＜0.001,t=5.006).Co-culture treatment out-comes revealed a significant elevation in S1P concentration within the supernatant after 6 hours of co-culture across all HSA sample processing groups with HUVEC cells,while no changes were observed in the supernatant of the blank control group.Notably,significant differences in supernatant S1P concentration were observed among treatment groups at 6 h,12 h,and 24 h(P＜0.001).SPR analysis unveiled a stronger affinity of pHSA for S1P compared to rHSA(KDpHSA-S1P:2.38E-06,KDrHSA-S1P:3.72E-06).Molecular docking analysis and binding pocket prediction suggested that the key binding pocket of HSA and S1P may reside in the IB subdomain of the HSA molecule.Conclusion HSA from various sources exhibits distinct binding and carrying effects on S1P,which appear to be closely associated with the IB subdomain of the HSA molecule.

Comparing with conventional human intravenous immunoglobulin products (hIVIG), IgM-enriched hIVIG have more advantages in the neutralization of pathogens and related toxins, the regulation of complement activity, secretion of cytokines and immune cell activity, but attention should be paid on its potential adverse reactions. Establishing a more simple and efficient technology for IgM concentration and purification and exploring a superior and safer virus inactivation technique were two prominent concerns in the process of production. At present, only one type of IgM-enriched hIVIG is on sale in global market (Pentaglobin®), but relative experimental research and clinical application is lacking in China. This article aims to provide references for the research and development of production and clinical application of these products in China by reviewing the research progress of IgM-enriched hIVIG at home and abroad in recent years.

Objective To establish a method for determinating the antigen-dependent cell-mediated cytotoxicity (ADCC) of human immunoglobulin (pH4)for intravenous injection (IVIG) on luciferase reporter gene-modified cell assay. Methods As effector cells, Jurkat-NFAT-Luc-CD16 cells were used in the assay, and PLC/PRF/5 cells were used as target cells. After incubation of effector cells and target cells with IVIG, the method for determinating ADCC biological activity of IVIG was established by detecting luciferase released by activated T nuclear factor after binding of IVIG Fc fragment to effector cells. Meanwhile, the experimental assay conditions were optimized, and the methodology was verified subsequently. Results IVIG had a dose-response relationship in this method, which was consistent with four parameter logistic model. And the PLC/PRF/5 cells were finally determined as the target cells. The initial dilution concentration of antibody was 20 mg/mL, and the ratio dilution was 1∶2, and the effector to target ratio was 1∶3, and co-incubation time of two cells and IVIG was 24 hours. Within-run and between-run analysis including three independent tests, initial working concentration relative light unit (RLU) and the relative standard deviation (RSD) of the concentration for 50% of maximal effect(EC50) were less than 11%. The relative titers of the recovery samples of the two different dilution groups were (23.50±1.69)% and (49.30±2.97)%, respectively, and the corresponding recovery rates were (93.50±6.30)% and (96.24±5.43)%, respectively, with RSD less than 11%. Conclusion The method for determinating ADCC biological activity of IVIG based on luciferase reporter gene-modified cell assay was successfully established. It could be applied in determinating the ADCC biological activity of IVIG, and has the advantages of satisfactory linearity, accuracy, precision and specificity.