Spatiotemporal immune atlas of a clinical-grade gene-edited pig-to-human kidney xenotransplant

Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. Here, we transplant a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and study the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells are uncommon in the porcine kidney cortex early after xenotransplantation and consist of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages express genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft is detectable. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression may be able to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

Crohn's patients and healthy infants share immunodominant B cell response to commensal flagellin peptide epitopes

About half of patients with Crohn's disease (CD) develop selective serum IgG response to flagellin proteins of the Lachnospiraceae family. Here, we identified a dominant B cell peptide epitope in CD, locating in the highly conserved "hinge region" between the D0 and D1 domains at the amino-terminus of Lachnospiraceae flagellins. Serum IgG reactive to this epitope is present at an elevated level in adult CD patients and in pediatric CD patients at diagnosis. Most importantly, high levels of serum IgG to the hinge epitope were found in most infants from 3 different geographic regions (Uganda, Sweden, and the USA) at one year of age. This vigorous homeostatic response decrements with age as it is not present in healthy adults. These data identify a distinct subset of CD patients, united by a shared reactivity to this dominant flagellin epitope that may represent failure of a homeostatic response beginning in infancy.

Alloreactivity and autoreactivity converge to support B cell epitope targeting in transplant rejection

Antibody (Ab) responses against human leukocyte antigen (HLA) proteins mismatched between donor and recipient are leading cause of allograft loss in kidney transplantation. However, therapies targeting alloreactive B cell and Ab-secreting cell (ASC) are lacking, motivating the need to understand how to prevent and abrogate these alloresponses. Using molecular, structural, and proteomic techniques, we profiled the B cell response in a kidney transplant recipient with antibody-mediated rejection and graft loss. We found that this response spanned the rejected organ and peripheral blood, stimulated the differentiation of multiple B cell subsets, and produced a high-affinity, donor-specific, anti-HLA response. We found epitopic immunodominance that relied on highly exposed, solvent-accessible mismatched HLA residues as well as structural and biomolecular evidence of autoreactivity against the recipient's self-HLA allele. These alloreactive and autoreactive signatures converged in the recipient's circulating donor-specific Ab repertoire, suggesting that rejection requires both the recognition of non-self and breaches of tolerance to lead to alloinjury and graft loss.

Spatiotemporal immune atlas of the first clinical-grade, gene-edited pig-to-human kidney xenotransplant

Pig-to-human xenotransplantation is rapidly approaching the clinical arena; however, it is unclear which immunomodulatory regimens will effectively control human immune responses to pig xenografts. We transplanted a gene-edited pig kidney into a brain-dead human recipient on pharmacologic immunosuppression and studied the human immune response to the xenograft using spatial transcriptomics and single-cell RNA sequencing. Human immune cells were uncommon in the porcine kidney cortex early after xenotransplantation and consisted of primarily myeloid cells. Both the porcine resident macrophages and human infiltrating macrophages expressed genes consistent with an alternatively activated, anti-inflammatory phenotype. No significant infiltration of human B or T cells into the porcine kidney xenograft was detected. Altogether, these findings provide proof of concept that conventional pharmacologic immunosuppression is sufficient to restrict infiltration of human immune cells into the xenograft early after compatible pig-to-human kidney xenotransplantation.

COVID-19 Vaccination and Remdesivir are Associated With Protection From New or Increased Levels of Donor-Specific Antibodies Among Kidney Transplant Recipients Hospitalized With COVID-19

Alloimmune responses in kidney transplant (KT) patients previously hospitalized with COVID-19 are understudied. We analyzed a cohort of 112 kidney transplant recipients who were hospitalized following a positive SARS-CoV-2 test result during the first 20 months of the COVID-19 pandemic. We found a cumulative incidence of 17% for the development of new donor-specific antibodies (DSA) or increased levels of pre-existing DSA in hospitalized SARS-CoV-2-infected KT patients. This risk extended 8 months post-infection. These changes in DSA status were associated with late allograft dysfunction. Risk factors for new or increased DSA responses in this KT patient cohort included the presence of circulating DSA pre-COVID-19 diagnosis and time post-transplantation. COVID-19 vaccination prior to infection and remdesivir administration during infection were each associated with decreased likelihood of developing a new or increased DSA response. These data show that new or enhanced DSA responses frequently occur among KT patients requiring admission with COVID-19 and suggest that surveillance, vaccination, and antiviral therapies may be important tools to prevent alloimmunity in these individuals.

First clinical-grade porcine kidney xenotransplant using a human decedent model

A radical solution is needed for the organ supply crisis, and the domestic pig is a promising organ source. In preparation for a clinical trial of xenotransplantation, we developed an in vivo pre-clinical human model to test safety and feasibility tenets established in animal models. After performance of a novel, prospective compatible crossmatch, we performed bilateral native nephrectomies in a human brain-dead decedent and subsequently transplanted two kidneys from a pig genetically engineered for human xenotransplantation. The decedent was hemodynamically stable through reperfusion, and vascular integrity was maintained despite the exposure of the xenografts to human blood pressure. No hyperacute rejection was observed, and the kidneys remained viable until termination 74 h later. No chimerism or transmission of porcine retroviruses was detected. Longitudinal biopsies revealed thrombotic microangiopathy that did not progress in severity, without evidence of cellular rejection or deposition of antibody or complement proteins. Although the xenografts produced variable amounts of urine, creatinine clearance did not recover. Whether renal recovery was impacted by the milieu of brain death and/or microvascular injury remains unknown. In summary, our study suggests that major barriers to human xenotransplantation have been surmounted and identifies where new knowledge is needed to optimize xenotransplantation outcomes in humans.

Single-Dose Intranasal Administration of AdCOVID Elicits Systemic and Mucosal Immunity against SARS-CoV-2 and Fully Protects Mice from Lethal Challenge

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the urgent need for effective prophylactic vaccination to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Intranasal vaccination is an attractive strategy to prevent COVID-19 as the nasal mucosa represents the first-line barrier to SARS-CoV-2 entry. The current intramuscular vaccines elicit systemic immunity but not necessarily high-level mucosal immunity. Here, we tested a single intranasal dose of our candidate adenovirus type 5-vectored vaccine encoding the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein (AdCOVID) in inbred, outbred, and transgenic mice. A single intranasal vaccination with AdCOVID elicited a strong and focused immune response against RBD through the induction of mucosal IgA in the respiratory tract, serum neutralizing antibodies, and CD4+ and CD8+ T cells with a Th1-like cytokine expression profile. A single AdCOVID dose resulted in immunity that was sustained for over six months. Moreover, a single intranasal dose completely protected K18-hACE2 mice from lethal SARS-CoV-2 challenge, preventing weight loss and mortality. These data show that AdCOVID promotes concomitant systemic and mucosal immunity and represents a promising vaccine candidate.

Memory B Cells in Pregnancy Sensitization

Memory B cells play an important role in immunity to pathogens as these cells are poised to rapidly differentiate into antibody-secreting cells upon antigen re-encounter. Memory B cells also develop over the course of HLA-sensitization during pregnancy and transplantation. In this review, we discuss the potential contribution of memory B cells to pregnancy sensitization as well as the impact of these cells on transplant candidacy and outcomes. We start by summarizing how B cell subsets are altered in pregnancy and discuss what is known about HLA-specific B cell responses given our current understanding of fetal antigen availability in maternal secondary lymphoid tissues. We then review the molecular mechanisms governing the generation and maintenance of memory B cells during infection - including the role of T follicular helper cells - and discuss the experimental evidence for the development of these cells during pregnancy. Finally, we discuss how memory B cells impact access to transplantation and transplant outcomes for a range of transplant recipients.

Single-dose intranasal administration of AdCOVID elicits systemic and mucosal immunity against SARS-CoV-2 in mice

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the urgent need for effective preventive vaccination to reduce burden and spread of severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) in humans. Intranasal vaccination is an attractive strategy to prevent COVID-19 as the nasal mucosa represents the first-line barrier to SARS-CoV-2 entry before viral spread to the lung. Although SARS-CoV-2 vaccine development is rapidly progressing, the current intramuscular vaccines are designed to elicit systemic immunity without conferring mucosal immunity. Here, we show that AdCOVID, an intranasal adenovirus type 5 (Ad5)-vectored vaccine encoding the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, elicits a strong and focused immune response against RBD through the induction of mucosal IgA, serum neutralizing antibodies and CD4+ and CD8+ T cells with a Th1-like cytokine expression profile. Therefore, AdCOVID, which promotes concomitant systemic and local mucosal immunity, represents a promising COVID-19 vaccine candidate.

A Predictive Model for a Reputation-Based General Surgery Residency Match and a Novel Online Calculator

OBJECTIVE

This study aimed to identify medical student characteristics that predict a successful categorical match into a general surgery residency and a match based upon Doximity program rankings.

DESIGN

This was a retrospective study that analyzed academic and personal predictors of a successful general surgery residency match.

SETTING

This study was set at the University of Alabama at Birmingham School of Medicine, a public medical school.

PARTICIPANTS

This study included 173 fourth-year medical students at a public medical school who matched into general surgery residency programs.

METHODS

Our cohort comprised students graduating from our institution between 2004 and 2015 that matched into preliminary or categorical general surgery positions. We collected academic variables and performed univariate analyses and logistic regression to examine the likelihood of specific match outcomes.

RESULTS

Of 173 students, 132 (76%) matched into a categorical position and 41 (24%) matched into a preliminary position. Of all variables, clinical ranking quartile was most effective in predicting a categorical match (R² = 0.35). Models for a match based upon Doximity ranking lacked the same predictive power.

CONCLUSIONS

This research identifies students that are at risk for not matching into a categorical position and predicts competitiveness for certain programs. It provides a novel calculator to give applicants easily interpretable match probabilities.

Scoliosis in Rett Syndrome: Progression, Comorbidities, and Predictors

BACKGROUND

Scoliosis is prominent in Rett syndrome (RTT). Following the prior report from the US Natural History Study, the onset and progression of severe scoliosis (≥40° Cobb angle) and surgery were examined regarding functional capabilities and specific genotypes, addressing the hypothesis that abnormal muscle tone, poor oral feeding, puberty, and delays or absence of sitting balance and ambulation may be responsible for greater risk in RTT.

METHODS

The multicenter RTT Natural History Study gathered longitudinal data for classic RTT, including mutation type, scoliosis, muscle tone, sitting, ambulation, hand function, and feeding. Cox regression models were used to examine the association between scoliosis and functional characteristics. All analyses utilized SAS 9.4; two-sided P values of <0.05 were considered significant.

RESULTS

A total of 913 females with classic RTT were included. Scoliosis frequency and severity increased with age. Severe scoliosis was found in 251 participants (27%), 113 of whom developed severe scoliosis during the follow-up assessments; 168 (18%) had surgical correction. Severe MECP2 mutations (R106W, R168X, R255X, R270X, and large deletions) showed a higher proportion of scoliosis. Individuals developing severe scoliosis or requiring surgery were less likely to sit, ambulate, or use their hands and were more likely to have begun puberty. Significant differences were absent for epilepsy rates, sleep problems, or constipation.

DISCUSSION

Scoliosis requires vigilance regarding the risk factors noted, particularly specific mutations and the role of puberty and motor abilities. Bracing is recommended for moderate curves and surgery for severe curves in accordance with published guidelines for scoliosis management.

Improved percutaneous slipped capital femoral epiphysis treatment: continuous biplanar fluoroscopy and proper guide wire selection

In 1990, a report was published outlining a technique of percutaneous fixation of slipped capital femoral epiphyses dramatically diminishing the morbidity associated with the open technique. Technical difficulties are still encountered with the morbidly obese child and the percutaneous technique. Two fluoroscopic units used continuously during the technique facilitate placement of the guide wire in a more acceptable anatomic location. Guide wire stiffness was also measured and used in preoperative planning. Ten hips were treated with this technique, and a prospective analysis of the surgical time and fluoroscopy time was done. Using the new technique, we found a significant reduction in surgical and fluoroscopic times.

Treatment of unicameral bone cyst with demineralized bone matrix

Eleven patients with active unicameral bone cysts were treated primarily with placement of demineralized bone matrix in the cyst by using a two-needle technique and a custom large-bore needle. Cyst healing was rated according to the Neer classification, and the average time of healing was 4.5 months. The demineralized bone matrix demonstrated an ability to obliterate the cyst in nine of 11 patients by using a single injection within 4-5 months, and at 2 years' follow-up, no cysts were deemed active or recurrent.

Pediatric vertebral osteomyelitis: diagnosis using computed tomography

The diagnosis of pediatric vertebral osteomyelitis has been enhanced through the use of computed tomography scan and magnetic resonance imaging. A retrospective analysis of seven patients with vertebral osteomyelitis was done to determine the studies used in medical management decisions and the outcome of these studies. Computed tomography scans were valuable in predicting if a patient would respond to medical management. The presence of a phlegmon on the computer-assisted tomography scan uniformly resulted in a failure of medical management or an indication for primary surgical management.

Improved treatment of femoral shaft fractures in children utilizing the pontoon spica cast: a long-term follow-up

This prospective study looked at 91 pediatric femur fractures. Patients were randomized into two groups: (a) A traditional group treated with 3 weeks in traction followed by spica; and (b) a pontoon spica group in which patients were treated first with only a few days in traction and then with a 90-90 pins-in-plastic spica. The pontoon spica provides excellent short- and long-term results. These include (a) providing substantial cost savings; (b) causing much less inconvenience to the family and child; (c) reducing the number of inpatient days, thereby freeing hospital beds; (d) permitting early motion; (e) reducing the number of short-term complications; and (f) preventing excessive shortening while controlling rotation.

Evaluation of acute gait abnormalities in preschool children

The charts of 60 consecutive children aged less than 5 years hospitalized for evaluation of a new onset limp or refusal to bear weight were reviewed. Only 1 of 22 patients with a normal complete blood count (CBC), erythrocyte sedimentation rate (ESR), and temperature had an infection. Of the 14 patients with a diagnosis of infection, only one had a normal CBC, ESR, and temperature. Radiographs were diagnostic in only four cases, whereas aspiration identified nine of 13 infections. Thirty-five bone scans were performed; 18 led to a definitive diagnosis including synovitis osteomyelitis, Perthes disease, juvenile rheumatoid arthritis, (JRA), fracture, soft tissue infection, and discitis.

Transient osteoporosis

Six hips in four patients with hip pain, limited range of motion, no antecedent trauma, and normal laboratory studies demonstrated roentgenographic evidence of periarticular osteoporosis. The subchondral cortex was attenuated. There was little or no cartilage loss. The preliminary diagnosis was transient osteoporosis (migratory osteolysis, regional osteoporosis). This problem is most frequently seen in the hip joint in two population groups: men near 40 and women in the third trimester of pregnancy. Other joints may be involved and the process may regress in one joint but recur in another. Diagnosis is based on typical clinical and roentgenographic observations including an aspiration of sterile joint fluid. Radioisotope scanning may be helpful. Bone or synovial biopsy sampling is not necessary. Proper management requires accurate diagnosis and conservative treatment of a cooperative patient. Pain may persist for six months or longer. Treatment consists of analgesics, protection against stress fractures, and physical therapy for prevention of contractures.

Closed Zickel nailing

A closed technique for Zickel nail insertion decreases morbidity, blood loss, and operative time. The Zickel intramedullary nail was originally developed as an open fixation device for fractures of the proximal third of the femur and subtrochanteric area. The open technique requires a lengthy incision, moderate blood loss, and time for insertion. For pathologic or impending pathologic fractures in sick patients, such a major operation is undesirable. The closed technique has been used successfully in five impending pathologic, three pathologic, and two traumatic subtrochanteric fractures. For these ten patients, the average operating time was one hour and 28 minutes with an average blood loss of 400 ml, a reduction of 40 minutes and 460 ml, respectively, over other available data. Time to ambulation and length of hospital stay are comparable to fractures treated openly. The closed technique is ideal for impending pathologic fractures, but may also be applicable to any pathologic or traumatic fractures that do not require an open procedure for alignment or supplementary fixation.

Preoperative skeletal traction in Legg-Perthes disease

In four of 11 patients with Legg-Perthes disease for which a varus femoral osteotomy was planned, routine split Russell traction failed to produce complete preoperative containment. Preoperative skeletal traction was used to distract the joint, displace the extruded lateral physis below the acetabular margin, and then reintroduce the femoral head into the acetabulum with progressive abduction. The femoral heads were rated postoperatively as good (two cases), fair (two cases), and poor (one case). Preoperative skeletal traction is an adjunctive treatment method for patients with "hinge abduction" in whom a varus femoral osteotomy is indicated.