Large-scale chemical-genetics yields new M. tuberculosis inhibitor classes.

New antibiotics are needed to combat rising levels of resistance, with new Mycobacterium tuberculosis (Mtb) drugs having the highest priority. However, conventional whole-cell and biochemical antibiotic screens have failed. Here we develop a strategy termed PROSPECT (primary screening of strains to prioritize expanded chemistry and targets), in which we screen compounds against pools of strains depleted of essential bacterial targets. We engineered strains that target 474 essential Mtb genes and screened pools of 100-150 strains against activity-enriched and unbiased compound libraries, probing more than 8.5 million chemical-genetic interactions. Primary screens identified over tenfold more hits than screening wild-type Mtb alone, with chemical-genetic interactions providing immediate, direct target insights. We identified over 40 compounds that target DNA gyrase, the cell wall, tryptophan, folate biosynthesis and RNA polymerase, as well as inhibitors that target EfpA. Chemical optimization yielded EfpA inhibitors with potent wild-type activity, thus demonstrating the ability of PROSPECT to yield inhibitors against targets that would have eluded conventional drug discovery.

Motor Branching Pattern of the Radial Nerve for Hyperselective Neurectomy: From Anatomy to Clinical Translation.

PURPOSE: Predominant or isolated spasticity of the triceps following upper motor neuron injury is rare and often unmasked once the spastic elbow flexors are addressed. The purpose of this study was to delineate the motor branching pattern of the radial nerve to determine the feasibility of hyperselective neurectomies (HSN) for triceps spasticity. METHODS: Dissections of the motor branch to each triceps head were performed on 11 upper-extremity specimens. The numbers of trunks, branching patterns, and muscle entry points were recorded in reference to the acromion to interepicondylar line. Based on anatomic studies, 10 patients underwent a combined fractional lengthening and HSN procedure for triceps spasticity. Patient demographics, time from diagnosis, and complications were recorded. Preoperative and postoperative Modified Ashworth Scale (MAS) and total active elbow arc of motion were compared. RESULTS: The first branch from the radial nerve was consistently a single trunk to the long triceps head. There were many variations in the branching pattern and number of trunks to the lateral and medial heads of the triceps with motor entry points between 31% and 95% of the acromion to interepicondylar line distance. Ten patients (six men and four women; mean age: 48.5 years) underwent the combined procedure. Mean total active elbow arc of motion improved from 78° before surgery to 111° after surgery, with a 17.5° increase in active elbow flexion. Compared with a mean preoperative triceps MAS of 2.75, nine patients had triceps MAS of 0 at a mean of 10.2 months of follow-up. There was no loss of functional elbow extension and no directly related complications. CONCLUSIONS: Given the variable motor entry points, HSN to each triceps head would require extensive dissection. Therefore, a combined approach consisting of fractional lengthening of the long head and lateral head with HSN of the triceps medial head is recommended to address triceps spasticity. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

The Effects of Radial Longitudinal Deficiency on Long-Term Use of the Thumb in Pediatric Patients Following Index Pollicization.

PURPOSE: To assess the effect of radial longitudinal deficiency on the function of pollicized digits as determined by the Thumb Grasp and Pinch (T-GAP) assessment. METHODS: We retrospectively evaluated 25 hands with thumb hypoplasia that underwent index finger pollicization. Patients were followed for an average of 10.4 years. Hands were divided by severity into two groups: no or mild radial longitudinal deficiency (RLD) (Group 1 = 16) and moderate to severe RLD (Group 2 = 9). We collected demographic information and completed physical examination measures, including hand strength, elbow, wrist, and hand range of motion, the Kapandji opposition score, active grasp span, and T-GAP total score. RESULTS: Patients with moderate to severe forms of RLD had stiffer long fingers, lower Kapandji opposition scores, and limited active and passive range of motion for elbow flexion, wrist ulnar deviation, and pollicized thumb interphalangeal flexion. They had shorter forearms, decreased active grasp span, and fewer thumb creases at the interphalangeal thumb joint. In addition, the T-GAP total score was significantly lower when comparing the two groups. Children with mild dysplasia were able to achieve 32% of age-matched normal grasp strength. Patients with more severe radial dysplasia averaged 17% less grasp strength compared with children with mild dysplasia. Patients with moderate to severe RLD also had lower T-GAP total scores and strength measurements if they had limited wrist ulnar deviation. CONCLUSIONS: Individuals with moderate to severe RLD have unique anatomical factors that affect outcomes after pollicization. These individuals use their thumbs for fewer activities, have weaker grasp, and retain more primitive grasp patterns compared with those who have milder forms of RLD. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic IV.

Nerve Transfers for Restoration of Elbow Flexion in Patients With Acute Flaccid Myelitis.

PURPOSE: The purpose of this study was to evaluate short- to midterm outcomes of patients with acute flaccid myelitis who underwent nerve transfers for restoration of elbow flexion. METHODS: Patients with a minimum of 10 months of follow up after undergoing nerve transfers to restore elbow flexion were clinically assessed using the Active Movement Scale (AMS). They were evaluated for any postoperative complications, particularly weakness in the distribution of the donor nerve(s). Fifteen of 25 consecutive patients who were treated using this surgical technique were included in the final analysis. RESULTS: All patients exhibited poor elbow flexion preoperatively (AMS 0 to 3). At a mean follow up of 17.3 months, 80% (15/25) of patients achieved excellent elbow flexion (AMS 6 or 7); 9 of these 15 had full active range of motion. Two patients achieved good elbow flexion (AMS 5) with antigravity movement to less than 50% of the passive range of motion. No cases of superficial or deep infection were reported, and all patients maintained identical motor function, relative to preoperative status, of the muscles innervated by the donor nerves. CONCLUSIONS: Nerve transfer surgery has shown promising short- to midterm results for recovery of nerve and muscle function, particularly for the restoration of elbow flexion. We recommend this treatment option for patients not demonstrating clinical improvement after 6 to 9 months of incomplete recovery. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Early results of nerve transfers for restoring function in severe cases of acute flaccid myelitis.

OBJECTIVE: To describe early functional outcomes of nerve transfer surgery in a relatively large cohort of patients with acute flaccid myelitis (AFM). METHODS: A retrospective case analysis was made of patients with AFM treated with nerve transfer surgery between 2007 and 2018. Surgical criteria were persistent motor deficits after 6 months from onset and available donor nerves. Thirty-two patients with AFM were evaluated; 16 underwent nerve transfer surgeries. Motor function was evaluated by a licensed occupational therapist using the Active Movement Scale preoperatively and during follow-up examinations. Patients with 6 or more months of follow-up were included in the analysis. Patients with procedures other than nerve transfers were excluded. RESULTS: Sixteen patients with AFM had nerve transfers, with a male predominance (75%) and median age of 2.5 years (range = 4 months-12 years). Eleven patients had a minimum 6 months of follow-up. Nerve transfers to restore elbow function had 87% excellent recovery for elbow flexion and 67% for elbow extension. Finger and thumb extension were full against gravity in 1 patient (100%). Shoulder external rotation was excellent in 50% of patients and shoulder abduction in only 20%. Nine of 10 patients (90%) had resolution of shoulder pseudosubluxation following nerve transfer to the suprascapular nerve. INTERPRETATION: Patients with AFM with persistent motor deficits 6 to 9 months after onset benefit from nerve transfer surgery. Restoration of elbow function was more reliable than restoration of shoulder function. We recommend early referral of patients with incomplete recovery to a center experienced in nerve transfers for timely evaluation and treatment. ANN NEUROL 2019;86:607-615.

What's New in Congenital Hand Surgery.

BACKGROUND: Congenital conditions of the hand and upper extremity are a frequent source of consultation among pediatric orthopaedists and hand surgeons. Advances in the fields of molecular biology and genetics have helped to better understand some of these conditions and redefine previous classification systems. New outcome measurement tools have been used to assess surgical results and have brought into focus a different aspect of the patients' experience. METHODS: We searched PubMed database for papers related to the treatment of congenital hand anomalies published from January 1, 2015 to October 31, 2018. The search was limited to English articles yielding 207 papers. Three pediatric hand surgeons selected the articles based upon the criteria that the topic was germane, the article fell under the subheadings within the manuscript, and the conclusions were meaningful. RESULTS: A total of 40 papers were selected for review, based upon their quality and new findings. Research articles with significant findings were included for syndactyly, symbrachydactyly, cleft hand, polydactyly, radial longitudinal deficiency, congenital radio-ulnar synostosis, and macrodactyly. CONCLUSIONS: Our knowledge of the embryology and pathophysiology of congenital upper extremity conditions continues to evolve. Functional assessments combined with patient and parent-reported outcomes have our understanding of the results following surgical procedures. Further research and standardization of our scientific data will provide better answers and higher quality of evidence. LEVEL OF EVIDENCE: Level V-literature review and expert opinion.

Regulation of adaptive immunity by the fractalkine receptor during autoimmune inflammation.

Fractalkine, a chemokine anchored to neurons or peripheral endothelial cells, serves as an adhesion molecule or as a soluble chemoattractant. Fractalkine binds CX3CR1 on microglia and circulating monocytes, dendritic cells, and NK cells. The aim of this study is to determine the role of CX3CR1 in the trafficking and function of myeloid cells to the CNS during experimental autoimmune encephalomyelitis (EAE). Our results show that, in models of active EAE, Cx3cr1(-/-) mice exhibited more severe neurologic deficiencies. Bone marrow chimeric mice confirmed that CX3CR1 deficiency in bone marrow enhanced EAE severity. Notably, CX3CR1 deficiency was associated with an increased accumulation of CD115(+)Ly6C(-)CD11c(+) dendritic cells into EAE-affected brains that correlated with enhanced demyelination and neuronal damage. Furthermore, higher IFN-γ and IL-17 levels were detected in cerebellar and spinal cord tissues of CX3CR1-deficient mice. Analyses of peripheral responses during disease initiation revealed a higher frequency of IFN-γ- and IL-17-producing T cells in lymphoid tissues of CX3CR1-deficient as well as enhanced T cell proliferation induced by CX3CR1-deficient dendritic cells. In addition, adoptive transfer of myelin oligodendrocyte glycoprotein35-55-reactive wild-type T cells induced substantially more severe EAE in CX3CR1-deficient recipients when compared with wild-type recipients. Collectively, the data demonstrate that besides its role in chemoattraction, CX3CR1 is a key regulator of myeloid cell activation contributing to the establishment of adaptive immune responses.

The fractalkine receptor but not CCR2 is present on microglia from embryonic development throughout adulthood.

Microglial cells are difficult to track during development because of the lack of specific reagents for myeloid subpopulations. To further understand how myeloid lineages differentiate during development to create microglial cells, we investigated CX3CR1 and CCR2 transcription unit activation in Cx3cr1(+/GFP)CCR2(+/RFP) knockin fluorescent protein reporter mice. The principal findings include: 1) CX3CR1(+) cells localized to the aorta-gonad-mesonephros region, and visualized at embryonic day (E)9.0 in the yolk sac and neuroectoderm; 2) at E10.5, CX3CR1 single-positive microglial cells were visualized penetrating the neuroepithelium; and 3) CX3CR1 and CCR2 distinguished infiltrating macrophages from resident surveillant or activated microglia within tissue sections and by flow cytometric analyses. Our results support the contribution of the yolk sac as a source of microglial precursors. We provide a novel model to monitor chemokine receptor expression changes in microglia and myeloid cells early (E8.0-E10.5) in development and during inflammatory conditions, which have been challenging to visualize in mammalian tissues.

Combined Hyperselective Neurectomy and Fractional Lengthening Technique for Triceps Spasticity.

Triceps spasticity can occur in patients with upper motor neuron syndrome. It is often undetected when there is predominant elbow flexion spasticity and/or contracture. This condition can become apparent after surgery for elbow flexor spasticity, leading to impaired active elbow. Although triceps muscle-tendon lengthening procedures can be performed, these techniques do not directly address the issue of spasticity which is neurally mediated. This article presents a surgical technique for addressing triceps spasticity with a combined approach of hyperselective neurectomy of the medial head of the triceps and muscle-tendon lengthening of the long and lateral heads.

Combined Wrist Extensor Tenodesis and Tendon Transfers for Severe Spastic Flexed Wrist Deformity: Surgical Technique and Case Series.

Spastic wrist flexion deformities both limit the functional use of the hand for grasp and pinch producing a stigmatizing appearance. Tendon transfers and total wrist arthrodesis are treatment options for this condition depending on the patient's characteristics, the latter the most commonly used in patients with severe wrist flexion deformities. Tendon transfers alone in this scenario have the tendency for recurrent deformity due to tenorrhaphy failure or soft tissue creep and resultant loss of tension. Total wrist arthrodesis is a more invasive procedure, which can have hardware or fusion problems and that is irreversible. We propose a novel technique that incorporates a distally based wrist extensor tendon slip and suture tape tenodesis to the distal radius. The rationale of this technique is to act as a protective, internal splint to prevent recurrent deformity after primary or revision tendon transfer for moderate to severe spastic flexed wrist deformities, avoiding the need to perform a total wrist arthrodesis.

Proximal Row Carpectomy With Soft Tissue Interposition: A Systematic Review of Clinical Outcomes.

Proximal row carpectomy (PRC) with soft tissue interposition arthroplasty (STIA) presents an alternative approach to addressing wrist arthritis patterns involving the capitate and/or lunate fossa, in lieu of wrist arthrodesis. This systematic review aimed to evaluate clinical outcomes and techniques associated with PRC-STIA in patients with advanced wrist arthritis. We conducted a systematic review using databases including PubMed, Embase, MEDLINE, and the Cochrane Central Register of Controlled Trials. Inclusion criteria involved articles reporting outcomes of patients who underwent PRC-STIA with at least 1 relevant outcome. The analysis encompassed 8 studies involving 106 patients (108 wrists) meeting the inclusion criteria. A majority of patients were men (69%, n = 88), with a mean age of 54.4 ± 12.7 years and an average follow-up of 4.8 ± 6.3 years. Dorsal capsule was the most commonly interposed tissue (63%, 5 out of 8 studies). Patients receiving STIA achieved comparable patient-reported outcome measures scores to those undergoing PRC alone. Postoperative pain, measured by the Visual Analog Scale, averaged 3.7 ± 0.6. The Disabilities of the Arm, Shoulder, and Hand score averaged 27.8 ± 8, while the Patient-Rated Wrist Evaluation score averaged 41.5 ± 25.9. Five complications were reported in three studies. The addition of STIA into PRC for patients with capitate and/or lunate fossa cartilage degeneration yielded outcomes akin to traditional PRC, improving wrist function, pain, and grip strength in a safe and straightforward manner. Future research should prioritize high-quality comparative studies, extended follow-up periods, and standardized core outcome measures for a more comprehensive understanding of its role in wrist arthritis treatment.

Human alveolar lining fluid from the elderly promotes Mycobacterium tuberculosis intracellular growth and translocation into the cytosol of alveolar epithelial cells.

The elderly population is highly susceptible to developing respiratory diseases, including tuberculosis, a devastating disease caused by the airborne pathogen Mycobacterium tuberculosis (M.tb) that kills one person every 18 seconds. Once M.tb reaches the alveolar space, it contacts alveolar lining fluid (ALF), which dictates host-cell interactions. We previously determined that age-associated dysfunction of soluble innate components in human ALF leads to accelerated M.tb growth within human alveolar macrophages. Here we determined the impact of human ALF on M.tb infection of alveolar epithelial type cells (ATs), another critical lung cellular determinant of infection. We observed that elderly ALF (E-ALF)-exposed M.tb had significantly increased intracellular growth with rapid replication in ATs compared to adult ALF (A-ALF)-exposed bacteria, as well as a dampened inflammatory response. A potential mechanism underlying this accelerated growth in ATs was our observation of increased bacterial translocation into the cytosol, a compartment that favors bacterial replication. These findings in the context of our previous studies highlight how the oxidative and dysfunctional status of the elderly lung mucosa determines susceptibility to M.tb infection, including dampening immune responses and favoring bacterial replication within alveolar resident cell populations, including ATs, the most abundant resident cell type within the alveoli.

Validation of Mycobacterium tuberculosis Rv1681 protein as a diagnostic marker of active pulmonary tuberculosis.

The development of an accurate antigen detection assay for the diagnosis of active tuberculosis (TB) would represent a major clinical advance. Here, we demonstrate that the Mycobacterium tuberculosis Rv1681 protein is a biomarker for active TB with potential diagnostic utility. We initially identified, by mass spectroscopy, peptides from the Rv1681 protein in urine specimens from 4 patients with untreated active TB. Rabbit IgG anti-recombinant Rv1681 detected Rv1681 protein in lysates and culture filtrates of M. tuberculosis and immunoprecipitated it from pooled urine specimens from two TB patients. An enzyme-linked immunosorbent assay formatted with these antibodies detected Rv1681 protein in unconcentrated urine specimens from 11/25 (44%) TB patients and 1/21 (4.8%) subjects in whom TB was initially clinically suspected but then ruled out by conventional methods. Rv1681 protein was not detected in urine specimens from 10 subjects with Escherichia coli-positive urine cultures, 26 subjects with confirmed non-TB tropical diseases (11 with schistosomiasis, 5 with Chagas' disease, and 10 with cutaneous leishmaniasis), and 14 healthy subjects. These results provide strong validation of Rv1681 protein as a promising biomarker for TB diagnosis.

Expert consensus on the surgical evaluation and management of upper extremity spasticity in adults.

In the last decade there has been incredible interest and advancement in the surgical care of adult patients with upper motor neuron (UMN) injuries. Spasticity represents a prevalent and debilitating feature of UMN syndrome, which can result from cerebral palsy, spinal cord injury, cerebrovascular accident and traumatic or anoxic brain injury. While several diagnostic tools and management strategies have been described for upper limb spasticity, evidence-based practice guidelines do not currently exist due to low patient volume and a paucity of surgeons routinely performing surgeries in UMN syndrome patients. As such, expert consensus may help provide guidance for patients, therapists and clinicians alike. In this article an expert panel was assembled, and the Delphi method was utilized to present diagnostic considerations, define operative indications, discuss surgical treatment modalities and encourage a standard set of outcome measures for patients with upper extremity spasticity.

Acute inflammation alters lung lymphocytes and potentiates innate-like behavior in young mouse lung CD8 T cells, resembling lung CD8 T cells from old mice.

Inflammation plays a significant role in lung infection including that caused by Mycobacterium tuberculosis, in which both adaptive and innate lymphocytes can affect infection control. How inflammation affects infection is understood in a broad sense, including inflammaging (chronic inflammation) seen in the elderly, but the explicit role that inflammation can play in regulation of lymphocyte function is not known. To fill this knowledge gap, we used an acute lipopolysaccharide (LPS) treatment in young mice and studied lymphocyte responses, focusing on CD8 T cell subsets. LPS treatment decreased the total numbers of T cells in the lungs of LPS mice while also increasing the number of activated T cells. We demonstrate that lung CD8 T cells from LPS mice became capable of an antigen independent innate-like IFN-γ secretion, dependent on IL-12p70 stimulation, paralleling innate-like IFN-γ secretion of lung CD8 T cells from old mice. Overall, this study provides information on how acute inflammation can affect lymphocytes, particularly CD8 T cells, which could potentially affect immune control of various disease states.

Animal Models of COVID-19: Transgenic Mouse Model.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), emerged in December 2019 in Wuhan, China, and rapidly spread throughout the world, threatening global public health. An animal model is a valuable and a crucial tool that allows understanding of nature in the pathogenesis of SARS-CoV-2 and its associated COVID-19 disease. Here we introduce detailed protocols of SARS-CoV-2 infection and COVID-19 disease using C57BL/6 (B6) transgenic mice expressing the human angiotensin-converting enzyme 2 (hACE2) from the human cytokeratin 18 promoter (K18 hACE2). To mimic natural SARS-CoV-2 infection, K18 hACE2 transgenic mice are infected intranasally under anesthesia. Upon infection, viral pathogenesis is determined by monitoring changes in body weight (morbidity) and monitoring survival (mortality), cytokine/chemokine responses, gross-lung pathology, histopathology, and viral replication in tissues. The presence of the virus and viral replication is evaluated by immunohistochemistry (IHC) and viral titrations, respectively, from the upper (nasal turbinate) and the lower (lungs) respiratory tracts, and nervous system (brain). Also, the immune response to SARS-CoV-2 infection is measured by cytokine/chemokine enzyme-linked immunosorbent assay (ELISA) from lung, spleen and brain homogenates to characterize the cytokine storm that hallmarks as one of the major causes of death caused by SARS-CoV-2 infection. This small rodent animal model based on the use of K18 hACE2 transgenic mice represents an excellent option to understand the pathogenicity of natural SARS-CoV-2 strains and its recently described Variants of Concern (VoC), and will be applicable to the identification and characterization of prophylactic (vaccine) and therapeutic (antiviral and/or neutralizing monoclonal antibodies) strategies for the prevention or treatment of SARS-CoV-2 infection or its associated COVID-19 disease.

GMP Manufacturing and IND-Enabling Studies of a Recombinant Hyperimmune Globulin Targeting SARS-CoV-2.

Conventionally, hyperimmune globulin drugs manufactured from pooled immunoglobulins from vaccinated or convalescent donors have been used in treating infections where no treatment is available. This is especially important where multi-epitope neutralization is required to prevent the development of immune-evading viral mutants that can emerge upon treatment with monoclonal antibodies. Using microfluidics, flow sorting, and a targeted integration cell line, a first-in-class recombinant hyperimmune globulin therapeutic against SARS-CoV-2 (GIGA-2050) was generated. Using processes similar to conventional monoclonal antibody manufacturing, GIGA-2050, comprising 12,500 antibodies, was scaled-up for clinical manufacturing and multiple development/tox lots were assessed for consistency. Antibody sequence diversity, cell growth, productivity, and product quality were assessed across different manufacturing sites and production scales. GIGA-2050 was purified and tested for good laboratory procedures (GLP) toxicology, pharmacokinetics, and in vivo efficacy against natural SARS-CoV-2 infection in mice. The GIGA-2050 master cell bank was highly stable, producing material at consistent yield and product quality up to >70 generations. Good manufacturing practices (GMP) and development batches of GIGA-2050 showed consistent product quality, impurity clearance, potency, and protection in an in vivo efficacy model. Nonhuman primate toxicology and pharmacokinetics studies suggest that GIGA-2050 is safe and has a half-life similar to other recombinant human IgG1 antibodies. These results supported a successful investigational new drug application for GIGA-2050. This study demonstrates that a new class of drugs, recombinant hyperimmune globulins, can be manufactured consistently at the clinical scale and presents a new approach to treating infectious diseases that targets multiple epitopes of a virus.

Acute Inflammation Confers Enhanced Protection against Mycobacterium tuberculosis Infection in Mice.

Inflammation plays a crucial role in the control of Mycobacterium tuberculosis infection. In this study, we demonstrate that an inflammatory pulmonary environment at the time of infection mediated by lipopolysaccharide treatment in mice confers enhanced protection against M. tuberculosis for up to 6 months postinfection. This early and transient inflammatory environment was associated with a neutrophil and CD11b+ cell influx and increased inflammatory cytokines. In vitro infection demonstrated that neutrophils from lipopolysaccharide-treated mice exhibited increased association with M. tuberculosis and had a greater innate capacity for killing M. tuberculosis. Finally, partial depletion of neutrophils in lipopolysaccharide-treated mice showed an increase in M. tuberculosis burden, suggesting neutrophils played a part in the protection observed in lipopolysaccharide-treated mice. These results indicate a positive role for an inflammatory environment in the initial stages of M. tuberculosis infection and suggest that acute inflammation at the time of M. tuberculosis infection can positively alter disease outcome. IMPORTANCE Mycobacterium tuberculosis, the causative agent of tuberculosis disease, is estimated to infect one-fourth of the world's population and is one of the leading causes of death due to an infectious disease worldwide. The high-level variability in tuberculosis disease responses in the human populace may be linked to immune processes related to inflammation. In many cases, inflammation appears to exasperate tuberculosis responses; however, some evidence suggests inflammatory processes improve control of M. tuberculosis infection. Here, we show an acute inflammatory stimulus in mice provides protection against M. tuberculosis for up to 6 months, suggesting acute inflammation can positively affect M. tuberculosis infection outcome.

Flexor Digitorum Superficialis Tendon Transfer for Wrist Extension.

Peripheral nerve injuries are among the most complex conditions facing upper-extremity surgeons. Loss of wrist extension can result in marked limitations, including loss of pinch and grip strength with discoordination of grasp and release. Tendon transfers represent the mainstay of operative treatment and have proven to be an effective method for restoring loss of wrist extension. The literature describes myriad techniques to restore loss of wrist extension. The best choice of transfers is dependent on what is available, depending on the level of injury. The present article describes a novel technique of transferring 2 flexor digitorum superficialis (FDS) tendons for wrist extension for patients with radial nerve lesions. The technique involves direct transfer of the long and ring finger FDS tendons to the third metacarpal bone. One FDS is routed through the interosseous membrane while the second FDS tendon is routed radially around the wrist to prevent a net supination or pronation force. If needed, the tendons can be alternatively routed to augment either pronation or supination. Passing both FDS tendons through the interosseous membrane creates a supination moment of the forearm, whereas routing both around the radius adds pronation. This article will review the relevant anatomy, indications, contraindications, operative technique, postoperative management, and outcomes. DESCRIPTION: The present article describes the technique of transferring 2 FDS tendons to restore wrist extension in patients who have lost wrist extension secondary to nerve lesions, such as radial nerve palsy and brachial plexus injuries. This technique involves the transfer of the long and ring finger FDS tendons around the base of the long metacarpal. One FDS tendon is routed through the interosseous membrane, and the second FDS tendon is routed radially around the wrist to add a pronation moment to the transfer. ALTERNATIVES: Alternatives include nerve transfers and tendon transfers1-5, such as:pronator teres to extensor carpi radialis longus and extensor carpi radialis brevis,palmaris longus to flexor carpi radialis,flexor carpi ulnaris to extensor digitorum communis III-V3,flexor carpi radialis to extensor indicis proprius, extensor digitorum communis, and extensor pollicis longus. RATIONALE: The pronator teres tendon has been the primary donor described to restore wrist extension. However, this tendon is often inadequate and requires a periosteal extension. In addition, the pronator muscle may be involved in brachial plexus injures and unavailable as a donor. Lastly, the FDS is synergistic with wrist extension, which facilitates rehabilitation. EXPECTED OUTCOMES: Child and adult patients are expected to have good control of function at 3 months postoperatively, with a full recovery at 6 months postoperatively. Because the FDS is synergistic with wrist extension, rehabilitation is straightforward. The wrist is immobilized in a sugar-tong for 3 to 4 weeks postoperatively, followed by the use of a removable thermoplastic wrist brace for 4 weeks full-time, except when bathing and performing physical therapy, and then for 4 weeks at night only. Physical therapy should focus on activation and training of the FDS under therapist supervision. Supervised active extension exercises can be initiated after week 4 postoperatively, taking care to avoid wrist flexion beyond neutral and resistive exercises. Functional exercises can be initiated at 6 weeks postoperatively, with light resistance only until week 12, coinciding with the discontinued use of the wrist brace. IMPORTANT TIPS: Surgery is performed through 4 primary incisions:○ a volar oblique incision in the distal palmar crease at the base of the long and ring fingers,○ a volar transverse incision at the mid-forearm,○ a dorsal transverse incision over the midshaft of the third metacarpal,○ a dorsal forearm transverse incision opposite to the volar forearm incision to shuttle the FDS tendon.The FDS donor tendons to the long and ring fingers are isolated first.Any adhesions between the FDS and flexor digitorum profundus are divided.The FDS tendons are left in the wounds until later to prevent desiccation.On occasion, the FDS tendons can become caught in the carpal canal during harvesting and will need to be pulled back into the distal palmar incision for further lysis of connections between the FDS and flexor digitorum profundus tendons.A wide window, not a slit, is cut in the interosseous membrane to pass 1 of the FDS tendons.A counter incision in the dorsal forearm is made with use of a long, curved clamp through the interosseous membrane. A Penrose drain is then passed through this tendon portal.Our preferred site for the FDS tendon attachments is around the base of the long metacarpal. ACRONYMS AND ABBREVIATIONS: FDS = flexor digitorum superficialisPT = pronator teresECRL = extensor carpi radialis longusECRB = extensor carpi radialis brevisFCU = flexor carpi ulnarisEDC = extensor digitorum communisFCR = flexor carpi radialisEIP = extensor indicis propriusEPL = extensor pollicis longusFDP = flexor digitorum profundusMC = metacarpal.

Lethality of SARS-CoV-2 infection in K18 human angiotensin-converting enzyme 2 transgenic mice.

Vaccine and antiviral development against SARS-CoV-2 infection or COVID-19 disease would benefit from validated small animal models. Here, we show that transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2) by the human cytokeratin 18 promoter (K18 hACE2) represent a susceptible rodent model. K18 hACE2 transgenic mice succumbed to SARS-CoV-2 infection by day 6, with virus detected in lung airway epithelium and brain. K18 ACE2 transgenic mice produced a modest TH1/2/17 cytokine storm in the lung and spleen that peaked by day 2, and an extended chemokine storm that was detected in both lungs and brain. This chemokine storm was also detected in the brain at day 6. K18 hACE2 transgenic mice are, therefore, highly susceptible to SARS-CoV-2 infection and represent a suitable animal model for the study of viral pathogenesis, and for identification and characterization of vaccines (prophylactic) and antivirals (therapeutics) for SARS-CoV-2 infection and associated severe COVID-19 disease.