Characterization of a robust serine protease from Bacillus subtilis K‐1

Process apt microbial proteases due to their wide range industrial applications have become the focus of intense scientific research during recent years. Considering the hostile process milieu, the proteases intended for application must be robust enough to withstand the extremes of temperature and pH, and presence of organic solvents and other potential enzyme inhibitors. Current study presents the characterization of a robust protease from a previously isolated bacterium Bacillus subtilis K‐1 (BSK‐1). Purification of BSK‐1 protease (5.21‐fold) was achieved to homogeneity by salt (ammonium sulfate) precipitation, and ion‐exchange (diethyl‐aminoethyl‐sephadex) and size exclusion chromatography (Sephadex G‐100). Molecular weight of BSK‐1 protease was determined by SDS‐PAGE analysis (42 kDa). Though the optimum temperature and pH for BSK‐1 protease activity was 50 °C and 10, respectively, but, the protease exhibited remarkable activity and stability over elevated temperatures (60–80 °C) and a broad pH range (pH 7–11). Protease showed resistance towards several organic solvents/other potential enzyme inhibitors. Drastic activity loss in presence of phenylmethylsulfonyl fluoride indicated that the enzyme is a serine protease. Kinetic parameters (K_m and V_max) for BSK‐1 protease were found to be 0.14 mg ml^?1 and 1176 mg min^?1, respectively. Putative amino acid sequence of BSK‐1 protease (derived from nucleotide sequence of protease gene) suggested that the enzyme belonged to peptidases S8/S53 super family with multidomain of S8. BSK‐1 protease being stable under harsh conditions may serve a model system for understanding the molecular basis of stability, and may help designing novel proteases that are suitable for industrial applications.     

Positive flow cytometry crossmatch with discrepant antibody testing results following COVID-19 vaccination

The impact of COVID-19 vaccination on the alloimmunity of transplant candidates is unknown. We report a case of positive B cell flow cytometry crossmatch in a patient waiting for second kidney transplantation, 37 days after receiving the COVID-19 vaccine. The preliminary crossmatch, using sample collected before COVID-19 vaccination, was negative. The antibodies to mismatched donor HLA-DR7 were detected only with multi-antigen beads but not with single-antigen beads, excluding possible prozone effects in solid-phase antibody assays. The crossmatches were positive with HLA-DR7–positive surrogates (n = 2) while negative with HLA-DR7–negative surrogates (n = 3), which confirms the HLA-DR7 alloreactivity. The antigen configurations on B lymphocytes are similar to that on the multi-antigen beads while distinct from the single-antigen beads. HLA-DR7 was the repeating mismatched antigen with the failing first kidney allograft. The newly emerged antibody to HLA-DR7 probably is the consequence of bystander activation of memory response by the COVID-19 vaccination. This case highlights the importance of verifying allo-sensitization history and utilizing multiple assays, including cell-based crossmatch and solid-phase assays with multi-antigens. COVID-19 immunization may deserve special attention when assessing the immunological risk before and after organ transplantation.     

Biological approach for management of anterior tooth trauma: triple case report

Anterior crown fractures are a common form of injury that mainly affect children and adolescents. The position of maxillary incisors and their eruptive pattern carries a significant risk for trauma. In the pre-adhesive era, fractured teeth needed to be restored either with pin-retained inlays or cast restorations that sacrificed healthy tooth structure, and were a challenge for clinicians to match with adjacent teeth. The development of adhesive dentistry has allowed dentists to use the patient's own fragment to restore the fractured tooth. Three cases are presented here with complicated crown fracture of maxillary central incisors; the reattachment of the fractured tooth segment in these cases has been performed using different combinations of techniques, viz. simple reattachment, circumferential bevel and internal dentinal groove.     

Bilirubin,a new therapeutic for kidney transplant?

In patients with end-stage renal disease, kidney transplantation has been associated with numerous benefits, including increased daily activity, and better survival rates. However, over 20% of kidney transplants result in rejection within five years. Rejection is primarily due to a hypersensitive immune system and ischemia/reperfusion injury. Bilirubin has been shown to be a potent antioxidant that is capable of potentially reversing or preventing damage from reactive oxygen species generated from ischemia and reperfusion. Additionally, bilirubin has several immunomodulatory effects that can dampen the immune system to promote organ acceptance. Increased bilirubin has also been shown to have a positive impact on renal hemodynamics, which is critical post-transplantation. Lastly, bilirubin levels have been correlated with biomarkers of successful transplantation. In this review, we discuss a multitude of potentially beneficial effects that bilirubin has on kidney acceptance of transplantation based on numerous clinical trials and animal models. Exogenous bilirubin delivery or increasing endogenous levels pre- or post-transplantation may have therapeutic benefits.     

Short‐term adverse effects of early subclinical allograft inflammation in kidney transplant recipients with a rapid steroid withdrawal protocol

The impact of subclinical inflammation (SCI) noted on early kidney allograft biopsies remains unclear. This study evaluated the outcome of SCI noted on 3‐month biopsy. A total of 273/363 (75%) kidney transplant recipients with a functioning kidney underwent allograft biopsies 3‐months posttransplant. Among those with stable allograft function at 3 months, 200 biopsies that did not meet the Banff criteria for acute rejection were identified. These were Group I: No Inflammation (NI, n = 71) and Group II: Subclinical Inflammation (SCI, n = 129). We evaluated differences in kidney function at 24‐months and allograft histology score at 12‐month biopsy. SCI patients had a higher serum creatinine (1.6 ± 0.7 vs 1.38 ± 0.45; P = .02) at 24‐months posttransplant, and at last follow‐up at a mean of 42.5 months (1.69 ± 0.9 vs 1.46 ± 0.5 mg/dL; P = .027). The allograft chronicity score (ci + ct + cg + cv) at 12‐months posttransplant was higher in the SCI group (2.4 ± 1.35 vs 1.9 ± 1.2; P = .02). The incidence of subsequent rejections within the first year in SCI and NI groups was 24% vs 10%, respectively (P = .015). De novo donor‐specific antibody within 12 months was more prevalent in the SCI group (12/129 vs 1/71, P = .03). SCI is likely not a benign finding and may have long‐term implications for kidney allograft function.     

Remodeling of the plasma membrane in preparation for sperm–egg recognition: roles of acrosomal proteins

The interaction of sperm with the egg''s extracellular matrix, the zona pellucida (ZP) is the first step of the union between male and female gametes. The molecular mechanisms of this process have been studied for the past six decades with the results obtained being both interesting and confusing. In this article, we describe our recent work, which attempts to address two lines of questions from previous studies. First, because there are numerous ZP binding proteins reported by various researchers, how do these proteins act together in sperm–ZP interaction? Second, why do a number of acrosomal proteins have ZP affinity? Are they involved mainly in the initial sperm–ZP binding or rather in anchoring acrosome reacting/reacted spermatozoa to the ZP? Our studies reveal that a number of ZP binding proteins and chaperones, extracted from the anterior sperm head plasma membrane, coexist as high molecular weight (HMW) complexes, and that these complexes in capacitated spermatozoa have preferential ability to bind to the ZP. Zonadhesin (ZAN), known as an acrosomal protein with ZP affinity, is one of these proteins in the HMW complexes. Immunoprecipitation indicates that ZAN interacts with other acrosomal proteins, proacrosin/acrosin and sp32 (ACRBP), also present in the HMW complexes. Immunodetection of ZAN and proacrosin/acrosin on spermatozoa further indicates that both proteins traffic to the sperm head surface during capacitation where the sperm acrosomal matrix is still intact, and therefore they are likely involved in the initial sperm–ZP binding step.     

Risk factors for delayed graft function and their impact on graft outcomes in live donor kidney transplantation

International Urology and Nephrology - Delayed graft function (DGF) is a manifestation of acute kidney injury uniquely framed within the transplant process and a predictor of poor long-term graft...