Isolation and escape mapping of broadly neutralizing antibodies against emerging delta-coronaviruses.

Porcine delta-coronavirus (PDCoV) spillovers were recently detected in febrile children, underscoring the recurrent zoonoses of divergent CoVs. To date, no vaccines or specific therapeutics are approved for use in humans against PDCoV. To prepare for possible future PDCoV epidemics, we isolated PDCoV spike (S)-directed monoclonal antibodies (mAbs) from humanized mice and found that two, designated PD33 and PD41, broadly neutralized a panel of PDCoV variants. Cryoelectron microscopy (cryo-EM) structures of PD33 and PD41 in complex with the S receptor-binding domain (RBD) and ectodomain trimer revealed the epitopes recognized by these mAbs, rationalizing their broad inhibitory activity. We show that both mAbs competitively interfere with host aminopeptidase N binding to neutralize PDCoV and used deep-mutational scanning epitope mapping to associate RBD antigenic sites with mAb-mediated neutralization potency. Our results indicate a PD33-PD41 mAb cocktail may heighten the barrier to escape. PD33 and PD41 are candidates for clinical advancement against future PDCoV outbreaks.

A potent pan-sarbecovirus neutralizing antibody resilient to epitope diversification.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolution has resulted in viral escape from clinically authorized monoclonal antibodies (mAbs), creating a need for mAbs that are resilient to epitope diversification. Broadly neutralizing coronavirus mAbs that are sufficiently potent for clinical development and retain activity despite viral evolution remain elusive. We identified a human mAb, designated VIR-7229, which targets the viral receptor-binding motif (RBM) with unprecedented cross-reactivity to all sarbecovirus clades, including non-ACE2-utilizing bat sarbecoviruses, while potently neutralizing SARS-CoV-2 variants since 2019, including the recent EG.5, BA.2.86, and JN.1. VIR-7229 tolerates extraordinary epitope variability, partly attributed to its high binding affinity, receptor molecular mimicry, and interactions with RBM backbone atoms. Consequently, VIR-7229 features a high barrier for selection of escape mutants, which are rare and associated with reduced viral fitness, underscoring its potential to be resilient to future viral evolution. VIR-7229 is a strong candidate to become a next-generation medicine.

Recurrent Ileocolic Intussusception With the Appendix as the Pathologic Lead Point in Children: A Report of Two Cases and Review of Literature.

Ileocolic intussusception is a consideration in young pediatric patients with acute abdominal pain. Meckel's diverticulum is the most common pathologic lead point for intussusception in children and the appendix acting as the lead point is rare. In addition, management guidelines for recurrent ileocolic intussusception (RICI) are lacking. We present two cases of RICI in which the pathological lead point was the appendix. The first patient, a two-year-old with no medical history, had intermittent abdominal pain and non-bloody vomiting for a month. Ultrasound revealed ileocolic intussusception, successfully managed with pneumatic reduction. However, symptoms recurred and a repeat ultrasound showed partial intussusception of the appendix into the cecum. Laparoscopic reduction and appendectomy were then performed. Symptomatic intussusception recurred, and a second laparoscopic reduction with stump appendectomy resolved all symptoms. The second patient, a three-year-old with no medical history, had colicky abdominal pain for 24 hours. Ultrasound revealed ileocolic intussusception that was pneumatically reduced. As pain recurred, laparoscopic reduction and appendectomy were performed, revealing ileocolic intussusception with a dilated appendix as the pathologic lead point. Recurrent ileocolic intussusception (RICI) with the appendix as the lead point is common, but RICI with the appendix as the lead point is rare. These cases demonstrate the role of the appendix as a pathologic lead point, and a review of the literature supports the need for surgical reduction. While enema reduction is the first line for recurrent intussusception, surgical reduction is preferred when a pathological lead point is suspected.

Broadly neutralizing antibodies against emerging delta-coronaviruses.

Porcine deltacoronavirus (PDCoV) spillovers were recently detected in children with acute undifferentiated febrile illness, underscoring recurrent zoonoses of divergent coronaviruses. To date, no vaccines or specific therapeutics are approved for use in humans against PDCoV. To prepare for possible future PDCoV epidemics, we isolated human spike (S)-directed monoclonal antibodies from transgenic mice and found that two of them, designated PD33 and PD41, broadly neutralized a panel of PDCoV variants. Cryo-electron microscopy structures of PD33 and PD41 in complex with the PDCoV receptor-binding domain and S ectodomain trimer provide a blueprint of the epitopes recognized by these mAbs, rationalizing their broad inhibitory activity. We show that both mAbs inhibit PDCoV by competitively interfering with host APN binding to the PDCoV receptor-binding loops, explaining the mechanism of viral neutralization. PD33 and PD41 are candidates for clinical advancement, which could be stockpiled to prepare for possible future PDCoV outbreaks.

The Extremes of Constipation: A Case of Stercoral Perforation From Fecal Impaction in a Teenager.

Stercoral perforation is a rare sequela of poorly controlled constipation that is more commonly seen in older, bedridden patients than in pediatric patients. We present the case of a 13-year-old patient requiring a divided sigmoid colostomy following rectal perforation, one of the few examples in the pediatric literature of stercoral perforation from chronic constipation. The current report highlights the importance of appropriate treatment of functional constipation at onset and the life-threatening complications that can occur without appropriate follow-up.

Neutralization, effector function and immune imprinting of Omicron variants.

Currently circulating SARS-CoV-2 variants have acquired convergent mutations at hot spots in the receptor-binding domain1 (RBD) of the spike protein. The effects of these mutations on viral infection and transmission and the efficacy of vaccines and therapies remains poorly understood. Here we demonstrate that recently emerged BQ.1.1 and XBB.1.5 variants bind host ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1, XBB.1 and BN.1 RBDs bound to the fragment antigen-binding region of the S309 antibody (the parent antibody for sotrovimab) and human ACE2 explain the preservation of antibody binding through conformational selection, altered ACE2 recognition and immune evasion. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1 and hamsters challenged with XBB.1.5. Vaccine-elicited human plasma antibodies cross-react with and trigger effector functions against current Omicron variants, despite a reduced neutralizing activity, suggesting a mechanism of protection against disease, exemplified by S309. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring the role of persistent immune imprinting.

An Extreme Case of Lethal Abdominal Compartment Syndrome in Pediatric Patient With Synovial Sarcoma.

There is a relative paucity of literature on abdominal compartment syndrome (ACS) in children compared to adults and even less describing ACS in pediatric oncologic patients. We present this case of ACS in a 14-year-old patient to highlight the acuity of lethal consequences despite swift adequate management. Our patient is a 14-year-old male with a history of non-verbal autism and large synovial sarcoma of the left chest wall. He was admitted for scheduled inpatient chemotherapy and radiation. On day 3 of admission, the patient's clinical condition rapidly deteriorated, and a surgical abdomen was found on the exam. In the operating room (OR), massive gaseous distention of the stomach, small intestines, and colon were noted. A loop of small bowel was under such high pressure that the force of evisceration sheared the bowel from the associated mesentery. Due to the severity of the dilated bowel loops, we could not return the eviscerated bowel back inside the abdomen, which led us to leave the Abthera wound vac as sole coverage. The patient was transferred to the PICU, and medical treatment was aimed toward palliative care. The patient passed away three hours later. This case illustrates the acute and lethal nature of ACS in a less studied population, the pediatric oncologic patient. Prompt detection and treatment of ACS are essential for the management of critically ill pediatric patients, especially in those with space occupying tumors within the abdominal cavity. However, extreme presentations of ACS can have lethal consequences despite swift surgical intervention and adequate management.

Vacuum-Assisted Closure Treats Refractory Esophageal Leak in a Pediatric Patient.

Esophageal perforations can have iatrogenic and non-iatrogenic causes. Early identification is a predictor of good outcomes. When identified, perforations can be managed conservatively with wide drainage or repaired surgically. Endoscopic esophageal vacuum-assisted closure may be used as a definitive treatment, particularly in scenarios where conservative management and primary surgical repair fail to achieve complete healing. We present such a scenario advocating for the consideration of endoscopic esophageal vacuum-assisted closure in patients with refractory esophageal leaks.

Therapeutic and vaccine-induced cross-reactive antibodies with effector function against emerging Omicron variants.

Currently circulating SARS-CoV-2 variants acquired convergent mutations at receptor-binding domain (RBD) hot spots. Their impact on viral infection, transmission, and efficacy of vaccines and therapeutics remains poorly understood. Here, we demonstrate that recently emerged BQ.1.1. and XBB.1 variants bind ACE2 with high affinity and promote membrane fusion more efficiently than earlier Omicron variants. Structures of the BQ.1.1 and XBB.1 RBDs bound to human ACE2 and S309 Fab (sotrovimab parent) explain the altered ACE2 recognition and preserved antibody binding through conformational selection. We show that sotrovimab binds avidly to all Omicron variants, promotes Fc-dependent effector functions and protects mice challenged with BQ.1.1, the variant displaying the greatest loss of neutralization. Moreover, in several donors vaccine-elicited plasma antibodies cross-react with and trigger effector functions against Omicron variants despite reduced neutralizing activity. Cross-reactive RBD-directed human memory B cells remained dominant even after two exposures to Omicron spikes, underscoring persistent immune imprinting. Our findings suggest that this previously overlooked class of cross-reactive antibodies, exemplified by S309, may contribute to protection against disease caused by emerging variants through elicitation of effector functions.

Maturation of SARS-CoV-2 Spike-specific memory B cells drives resilience to viral escape.

Memory B cells (MBCs) generate rapid antibody responses upon secondary encounter with a pathogen. Here, we investigated the kinetics, avidity, and cross-reactivity of serum antibodies and MBCs in 155 SARS-CoV-2 infected and vaccinated individuals over a 16-month time frame. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals. Whereas MBCs of infected individuals targeted both prefusion and postfusion Spike (S), most vaccine-elicited MBCs were specific for prefusion S, consistent with the use of prefusion-stabilized S in mRNA vaccines. Furthermore, a large fraction of MBCs recognizing postfusion S cross-reacted with human betacoronaviruses. The avidity of MBC-derived and serum antibodies increased over time resulting in enhanced resilience to viral escape by SARS-CoV-2 variants, including Omicron BA.1 and BA.2 sublineages, albeit only partially for BA.4 and BA.5 sublineages. Overall, the maturation of high-affinity and broadly reactive MBCs provides the basis for effective recall responses to future SARS-CoV-2 variants.

Surgical Reconstruction Options for a Case of Near Total Intestinal Aganglionosis.

Hirschsprung's disease is a congenital anomaly affecting neural crest cell migration and proliferation in the myenteric plexi resulting in dysmotility, which can present as bilious emesis, delayed meconium passage, and bowel obstruction in neonates, or chronic constipation in older children. Depending on the extent of aganglionosis, this disease can involve the whole gut. Treatment involves a temporary ostomy and interval definitive surgical reconstruction. In patients with near or total intestinal aganglionosis, however, there is no consensus on the most effective surgical reconstruction as consideration of the length and function of the normal remnant bowel create concerns for complications with short bowel syndrome post-operatively. We present a case of near-total intestinal aganglionosis highlighting the various options for definitive surgical reconstruction.

Traumatic Left Anterior Descending Artery Dissection in a Case of Pediatric Blunt Chest Trauma.

Despite the reserve for recovery in pediatric trauma, blunt force chest trauma can cause insidious injuries that are easy to miss. Coronary artery dissection is a rare injury associated with blunt force chest trauma in the pediatric population and can present with vague or atypical symptoms. Pediatric patients can be unreliable in reporting symptoms, and providers can mistake coronary artery injuries for myocardial contusion, especially with improving laboratory tests and equivocal imaging. We report a case showing the importance of a high index of suspicion when presented with this trauma pattern in a pediatric patient.

Presenting a Case of an Extralobar and Extrapleural Pulmonary Sequestration in a Four-Month-Old Infant.

Pulmonary sequestration is a congenital disease formed by embryogenic separation of the lung parenchyma, halting development and function. It has an aberrant blood supply and can provide a nidus for infection and respiratory compromise. It can be diagnosed prenatally with surgical resection after delivery reserved as the best mode of treatment. In literature, six to twelve months is the most optimal time for elective surgical repair giving time for some maturation to withstand single lung ventilation and operation before the risk of infection heightens after 12 months. We present a case of an infant that had an elective repair at four months of age with no postoperative sequelae highlighting that surgeons can perform elective repair sooner than six months of age and that surgical decision-making should be on a case-by-case basis.

Single-Incision Laparoscopic Appendectomy Using Standard 5 mm Trocars: Single Pediatric Center Experience.

Purpose: Single-incision laparoscopic appendectomy (SILA) for the treatment of appendicitis has been documented. Typically, SILA requires the use of specialized ports, instruments, and materials. The SILA technique at our institution utilizes the same instrumentation as the conventional laparoscopic approach (CLA), thus obviating the need for these specialized products. This study aims to further demonstrate the noninferiority of our SILA technique for the treatment of uncomplicated appendicitis. Materials and Methods: This is a single-institution retrospective review of patients who underwent SILA from 2011 to 2020 to treat uncomplicated appendicitis. Outcomes including demographics, operative time, length of stay (LOS), and common postsurgical complications were evaluated. These SILA cases were matched with up to 3 CLA controls based on age, gender, and weight utilizing the Greedy match method. Patients with an operative diagnosis of perforated appendicitis were excluded. Results: A total of 137 patients underwent SILA at a single institution. A total of 128 patients were in the final cohort after excluding perforated appendicitis. Mean age was 11.9 years. Case-control matching was conducted with 349 controls included. Between cases and controls, SILA had shorter operative time (27.2 minutes versus 43.7 minutes, P < .001) with no difference in mean LOS (42.4 hours versus 42.4 hours, P = .88). There was no difference in complication rate (5.4% versus 8.5%, P = .06). There was no difference in readmission rate (0.8% versus 3.4%, P = .108). Conclusion: These data suggest that for appropriately selected patients, our SILA technique is noninferior to CLA with shortened operative time.

Maturation of SARS-CoV-2 Spike-specific memory B cells drives resilience to viral escape.

Memory B cells (MBCs) generate rapid antibody responses upon secondary encounter with a pathogen. Here, we investigated the kinetics, avidity and cross-reactivity of serum antibodies and MBCs in 155 SARS-CoV-2 infected and vaccinated individuals over a 16-month timeframe. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals. Whereas MBCs of infected individuals targeted both pre- and postfusion Spike (S), most vaccine-elicited MBCs were specific for prefusion S, consistent with the use of prefusion-stabilized S in mRNA vaccines. Furthermore, a large fraction of MBCs recognizing postfusion S cross-reacted with human betacoronaviruses. The avidity of MBC-derived and serum antibodies increased over time resulting in enhanced resilience to viral escape by SARS-CoV-2 variants, including Omicron BA.1 and BA.2 sub-lineages, albeit only partially for BA.4 and BA.5 sublineages. Overall, the maturation of high-affinity and broadly-reactive MBCs provides the basis for effective recall responses to future SARS-CoV-2 variants.

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron sublineages carry distinct spike mutations resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters elicit plasma-neutralizing antibodies against Omicron BA.1, BA.2, BA.2.12.1, and BA.4/5, and that breakthrough infections, but not vaccination alone, induce neutralizing antibodies in the nasal mucosa. Consistent with immunological imprinting, most antibodies derived from memory B cells or plasma cells of Omicron breakthrough cases cross-react with the Wuhan-Hu-1, BA.1, BA.2, and BA.4/5 receptor-binding domains, whereas Omicron primary infections elicit B cells of narrow specificity up to 6 months after infection. Although most clinical antibodies have reduced neutralization of Omicron, we identified an ultrapotent pan-variant-neutralizing antibody that is a strong candidate for clinical development.

A Case of Delayed Cecal Perforation After Abdominal (Seat Belt) Injury.

Seatbelts have reduced the number of fatal head, facial, and chest injuries. They have, however, introduced a set of injuries comprising abdominal wall bruising, Intra-abdominal injuries, and lumbar spine fractures collectively termed the seat belt syndrome. Surgical repair is the treatment for encountered bowel injuries. We present a case of delayed bowel perforation following presentation with signs of seat belt trauma identifying a decisional dilemma in the surgical management of serosal tears with no apparent signs of perforation.

Imprinted antibody responses against SARS-CoV-2 Omicron sublineages.

SARS-CoV-2 Omicron sublineages carry distinct spike mutations and represent an antigenic shift resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters result in potent plasma neutralizing activity against Omicron BA.1 and BA.2 and that breakthrough infections, but not vaccination-only, induce neutralizing activity in the nasal mucosa. Consistent with immunological imprinting, most antibodies derived from memory B cells or plasma cells of Omicron breakthrough cases cross-react with the Wuhan-Hu-1, BA.1 and BA.2 receptor-binding domains whereas Omicron primary infections elicit B cells of narrow specificity. While most clinical antibodies have reduced neutralization of Omicron, we identified an ultrapotent pan-variant antibody, that is unaffected by any Omicron lineage spike mutations and is a strong candidate for clinical development.

Poor neutralization and rapid decay of antibodies to SARS-CoV-2 variants in vaccinated dialysis patients.

Patients on dialysis are at risk of severe course of SARS-CoV-2 infection. Understanding the neutralizing activity and coverage of SARS-CoV-2 variants of vaccine-elicited antibodies is required to guide prophylactic and therapeutic COVID-19 interventions in this frail population. By analyzing plasma samples from 130 hemodialysis and 13 peritoneal dialysis patients after two doses of BNT162b2 or mRNA-1273 vaccines, we found that 35% of the patients had low-level or undetectable IgG antibodies to SARS-CoV-2 Spike (S). Neutralizing antibodies against the vaccine-matched SARS-CoV-2 and Delta variant were low or undetectable in 49% and 77% of patients, respectively, and were further reduced against other emerging variants. The fraction of non-responding patients was higher in SARS-CoV-2-naïve hemodialysis patients immunized with BNT162b2 (66%) than those immunized with mRNA-1273 (23%). The reduced neutralizing activity correlated with low antibody avidity. Patients followed up to 7 months after vaccination showed a rapid decay of the antibody response with an average 21- and 10-fold reduction of neutralizing antibodies to vaccine-matched SARS-CoV-2 and Delta variant, which increased the fraction of non-responders to 84% and 90%, respectively. These data indicate that dialysis patients should be prioritized for additional vaccination boosts. Nevertheless, their antibody response to SARS-CoV-2 must be continuously monitored to adopt the best prophylactic and therapeutic strategy.

Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift.

The recently emerged SARS-CoV-2 Omicron variant encodes 37 amino acid substitutions in the spike protein, 15 of which are in the receptor-binding domain (RBD), thereby raising concerns about the effectiveness of available vaccines and antibody-based therapeutics. Here we show that the Omicron RBD binds to human ACE2 with enhanced affinity, relative to the Wuhan-Hu-1 RBD, and binds to mouse ACE2. Marked reductions in neutralizing activity were observed against Omicron compared to the ancestral pseudovirus in plasma from convalescent individuals and from individuals who had been vaccinated against SARS-CoV-2, but this loss was less pronounced after a third dose of vaccine. Most monoclonal antibodies that are directed against the receptor-binding motif lost in vitro neutralizing activity against Omicron, with only 3 out of 29 monoclonal antibodies retaining unaltered potency, including the ACE2-mimicking S2K146 antibody1. Furthermore, a fraction of broadly neutralizing sarbecovirus monoclonal antibodies neutralized Omicron through recognition of antigenic sites outside the receptor-binding motif, including sotrovimab2, S2X2593 and S2H974. The magnitude of Omicron-mediated immune evasion marks a major antigenic shift in SARS-CoV-2. Broadly neutralizing monoclonal antibodies that recognize RBD epitopes that are conserved among SARS-CoV-2 variants and other sarbecoviruses may prove key to controlling the ongoing pandemic and future zoonotic spillovers.