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• The RBD domain has the most antigenicity in the SARS-CoV-2 spike protein sequence. • Recombinant production of re-RBD yielded 4 g/L protein with > 95% purity. • ELISA analysis of re-RBD yielded 100% specificity and 91.5% sensitivity. More than 3 y into the coronavirus 2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to undergo mutations. In this context, the Receptor Binding Domain (RBD) is the most antigenic region among the SARS-CoV-2 Spike protein and has emerged as a promising candidate for immunological development. We designed an IgG-based indirect enzyme-linked immunoassay (ELISA) kit based on recombinant RBD, which was produced from the laboratory to 10 L industry scales in Pichia pastoris. A recombinant-RBD comprising 283 residues (31 kDa) was constructed after epitope analyses. The target gene was initially cloned into an Escherichia coli TOP10 genotype and transformed into Pichia pastoris CBS7435 muts for protein production. Production was scaled up in a 10 L fermenter after a 1 L shake-flask cultivation. The product was ultrafiltered and purified using ion-exchange chromatography. IgG-positive human sera for SARS-CoV-2 were employed by an ELISA test to evaluate the antigenicity and specific binding of the produced protein. Bioreactor cultivation yielded 4 g/l of the target protein after 160 h of fermentation, and ion-exchange chromatography indicated a purity > 95%. A human serum ELISA test was performed in 4 parts, and the ROC area under the curve (AUC) was > 0.96 for each part. The mean specificity and sensitivity of each part was 100% and 91.5%, respectively. A highly specific and sensitive IgG-based serologic kit was developed for improved diagnostic purposes in patients with COVID-19 after generating an RBD antigen in Pichia pastoris at laboratory and 10 L fermentation scales. [ABSTRACT FROM AUTHOR]

• A significant proportion of couples undergoing IVF experience recurrent implantation failure (RIF). • Among all different elements that affect implantation failure, the immune system has been the most reasonable and debated. • By stimulation of immune system and initiation of humoral immunity, immunotolerance panel is completely changed in RIF. • Inflammatory responses as pNK cells, Th17 signaling pathway and TLR signaling pathway are activated in RIF patient. A significant part of couples in IVF-ICSI cycles experience Repeated Implantation Failure (RIF). Screening of the embryos with new methods like Next Generation Sequencing and arrays showed that even euploid embryos fail to implant. Immunology is a potent window maybe resolve the RIF problem. In this investigation we employed innate and adaptive immune system PCR array to compare the transcriptome profiles of endometrium in unexplained RIF and healthy fertile women. A total of 21 women were enrolled in the present study, 11women with unexplained RIF and 10 healthy fertile women. After RNA extraction and cDNA synthesis PCR array was performed using RT2 profiler PCR array human innate and adaptive immune responses kit (Qiagen, Cat.No: PAHS-052A). PCR Array data analysis identified significantly greater expression of IL6, IFNG, IL17A, IL23A, IFNA1, IFNB1, CD40 L, CCR4, CCR5, CCR6, CXR3, CCL2, IL2, TLR4, IRF3, STAT3, RAG1, IFNAR1 in unexplained RIF women than in controls (P < 0.05). However, expression of IL1B, IL8, NFKB, HLA-A, HLA-E, CD80, CD40 was significantly lower in unexplained RIF group than in controls (P < 0.05). Our results showed that modulation of immune system in RIF patient is shifted to inflammatory responses as pNK cells, Th17 signaling pathway and TLR signaling pathway are activated. So, by stimulation of immune system and initiation of humoral immune responses the panel of immunity and immunotolerance is completely changed in RIF patients comparing normal. It seems that attention to these alterations individually help physician to manage RIF patients better. [ABSTRACT FROM AUTHOR]