[Prediction of superantigen active sites and clonal expression of staphylococcal enterotoxin-like W]

Objective: The docking and superantigen activity sites of staphylococcal enterotoxin-like W (SElW) and T cell receptor (TCR) were predicted, and its SElW was cloned, expressed and purified. Methods: AlphaFold was used to predict the 3D structure of SElW protein monomers, and the protein models were evaluated with the help of the SAVES online server from ERRAT, Ramachandran plot, and Verify_3D. The ZDOCK server simulates the docking conformation of SElW and TCR, and the amino acid sequences of SElW and other serotype enterotoxins were aligned. The primers were designed to amplify selw, and the fragment was recombined into the pMD18-T vector and sequenced. Then recombinant plasmid pMD18-T was digested with BamHⅠand Hind Ⅲ. The target fragment was recombined into the expression plasmid pET-28a(+). After identification of the recombinant plasmid, the protein expression was induced by isopropyl-beta-D- thiogalactopyranoside. The SElW expressed in the supernatant was purified by affinity chromatography and quantified by the BCA method. Results: The predicted three-dimensional structure showed that the SElW protein was composed of two domains, the amino-terminal and the carboxy-terminal. The amino-terminal domain was composed of 3 α-helices and 6 β-sheets, and the carboxy-terminal domain included 2 α-helices and 7 antiparallel β-sheets composition. The overall quality factor score of the SElW protein model was 98.08, with 93.24% of the amino acids having a Verify_3D score ≥0.2 and no amino acids located in disallowed regions. The docking conformation with the highest score (1 521.328) was selected as the analysis object, and the 19 hydrogen bonds between the corresponding amino acid residues of SElW and TCR were analyzed by PyMOL. Combined with sequence alignment and the published data, this study predicted and found five important superantigen active sites, namely Y18, N19, W55, C88, and C98. The highly purified soluble recombinant protein SElW was obtained with cloning, expression, and protein purification. Conclusions: The study found five superantigen active sites in SElW protein that need special attention and successfully constructed and expressed the SElW protein, which laid the foundation for further exploration of the immune recognition mechanism of SElW.

Responsible genes in children with primary vesicoureteral reflux: findings from the Chinese Children Genetic Kidney Disease Database

BACKGROUND

Primary vesicoureteral reflux (VUR) is a common congenital anomaly of the kidney and urinary tract (CAKUT) in childhood. The present study identified the possible genetic contributions to primary VUR in children.

METHODS

Patients with primary VUR were enrolled and analysed based on a national multi-center registration network (Chinese Children Genetic Kidney Disease Database, CCGKDD) that covered 23 different provinces/regions in China from 2014 to 2019. Genetic causes were sought using whole-exome sequencing (WES) or targeted-exome sequencing.

RESULTS

A total of 379 unrelated patients (male: female 219:160) with primary VUR were recruited. Sixty-four (16.9%) children had extrarenal manifestations, and 165 (43.5%) patients showed the coexistence of other CAKUT phenotypes. Eighty-eight patient (23.2%) exhibited impaired renal function at their last visit, and 18 of them (20.5%) developed ESRD at the median age of 7.0 (IQR 0.9-11.4) years. A monogenic cause was identified in 28 patients (7.39%). These genes included PAX2 (n = 4), TNXB (n = 3), GATA3 (n = 3), SLIT2 (n = 3), ROBO2 (n = 2), TBX18 (n = 2), and the other 11 genes (one gene for each patient). There was a significant difference in the rate of gene mutations between patients with or without extrarenal complications (14.1% vs. 6%, P = 0.035). The frequency of genetic abnormality was not statistically significant based on the coexistence of another CAKUT (9.6% vs. 5.6%, P = 0.139, Chi-square test) and the grade of reflux (9.4% vs. 6.7%, P = 0.429). Kaplan-Meier survival curve showed that the presence of genetic mutations did affect renal survival (Log-rank test, P = 0.01). PAX2 mutation carriers (HR 5.1, 95% CI 1.3-20.0; P = 0.02) and TNXB mutation carriers (HR 20.3, 95% CI 2.4-168.7; P = 0.01) were associated with increased risk of progression to ESRD.

CONCLUSIONS

PAX2, TNXB, GATA3 and SLIT2 were the main underlying monogenic causes and accounted for up to 46.4% of monogenic VUR. Extrarenal complications and renal function were significantly related to the findings of genetic factors in children with primary VUR. Like other types of CAKUT, several genes may be responsible for isolated VUR.

Risk factors for loss of residual renal function in children with end-stage renal disease undergoing automatic peritoneal dialysis

BACKGROUND

This study analysed children with end-stage renal disease treated with automated peritoneal dialysis (APD) in our centre to explore the risk factors associated with residual renal function (RRF) loss.

METHODS

Children treated with APD as the initial renal replacement therapy regimen from January 2008 to December 2016 were included. All the children had a daily urine volume of ≥100 ml/m² when APD was initiated and a dialysis follow-up time of ≥12 months. A daily urine volume of <100 ml/m² after 12 months of APD treatment was defined as loss of RRF. Possible risk factors that may be associated with RRF loss were analysed.

RESULTS

A total of 66 children were included in the study. After 12 months of APD treatment, the daily urine volume decreased by 377.45 ± 348.80 ml/m², the residual glomerular filtration rate decreased by 6.39 ± 3.69 ml/min/1.73 m² and 29 of the patients (43.9%) developed RRF loss. The higher risk of RRF loss after 1 year of APD treatment was most pronounced in patients with daily urine volume of ≤400 ml/m² before treatment, higher glucose exposure and higher ultrafiltration volume, while the lower risk of RRF loss was in patients with administration of diuretics. Each increase of 1 g/m²/day glucose exposure was associated with a 5% increase in RRF loss (odds ratio (OR) 1.05, p = 0.023) and each increase of 1 ml/m²/day ultrafiltration volume was associated with a 1% increase in RRF loss (OR 1.01, p = 0.013).

CONCLUSION

In children undergoing APD, the risk for loss of RRF is associated with low urine volume at the start of APD, high glucose loading and high peritoneal ultrafiltration volume, while preservation of RRF is associated with the usage of diuretics.