Evolving Approach to Antibiotic Treatment of Pediatric Spondylodiscitis.

OBJECTIVE: To describe for intervertebral spondylodiscitis (IS) its clinical characteristics, treatment approaches with intravenous (IV) antibiotics, and clinical implications of changes in treatment approach. STUDY DESIGN: This retrospective study included all children aged 0 through18 years diagnosed with imaging-confirmed thoracic and lumbar IS from 2000 to 2022 at a tertiary pediatric hospital. Patients with longer intravenous (IV) treatment regimen were compared with those with a shorter clinically directed IV to oral regimen. RESULTS: In all, 124 cases were included with median age 14.9 months (IQR 12.7-19.4) at diagnosis. Irritability and pain while changing diapers were common symptoms (52.4% and 49.2%, respectively). Elevated erythrocyte sedimentation rate (ESR) was the most common laboratory finding (95%, median 50 [IQR 34-64] mm/h). Elevated ESR was found in higher proportions (95%) compared with elevated CRP (76%, median 1.8 mg/dL; P< 0.001). Since implementing the shorter clinically directed IV treatment duration for patients with thoracic and lumbar IS, hospitalization duration was reduced from a median of 12 to 8 days (P =0.008) and IV treatment duration by a median of 14 to 8 days (P<0.001). Only 1(1.6%) patient in the clinically directed treatment group required re-hospitalization due to failure of therapy. Conversely, 9/124 children in the cohort suffered from IV treatment related complications; all had been treated IV for prolonged periods. CONCLUSION: Early transition to oral treatment in pediatric spondylodiscitis appears to be appropriate clinically, and shortens hospital stay and intravenous treatment duration without major negative clinical impact.

The effect of environmental noise isolation on bronchiolitis severity in hospitalised children.

AIM: Bronchiolitis is an infectious disease, with no effective treatment. Music and Mozart's works specifically are known to have a positive effect on physiological parameters, while noise is considered harmful. We aim to evaluate the short-term effect of environmental noise detachment and/or music listening on the course of bronchiolitis in hospitalised children. METHODS: This is a prospective, double-blinded randomised controlled trial. Patients were divided into three intervention groups: 1-Mozart's Sonata, 2-instrumental music, 3-silence. Music was heard via media players and soundproof headphones. Disease severity was evaluated before and after intervention using the Modified Tal score. RESULTS: Seventy music sessions were included in the analysis (Mozart n = 23, instrumental n = 22, silence n = 25). A one-point drop in the average bronchiolitis severity score was observed in all three groups from 7.1 (CI 95%, 5 to 9.2) to 6.1 (CI 95%, 4.3 to 7.9), p < 0.001. No significant difference was found between the three groups with respect to change in the severity score before and after the intervention. CONCLUSION: Isolation from disturbing sounds heard in paediatric departments could be considered a simple non-invasive intervention in children hospitalised with bronchiolitis. Further studies are warranted to evaluate long-term effects of this intervention and the specific effect of music.

Polarizing receptor activation dissociates fibroblast growth factor 2 mediated inhibition of myelination from its neuroprotective potential.

Fibroblast growth factor (FGF) signaling contributes to failure of remyelination in multiple sclerosis, but targeting this therapeutically is complicated by its functional pleiotropy. We now identify FGF2 as a factor up-regulated by astrocytes in active inflammatory lesions that disrupts myelination via FGF receptor 2 (FGFR2) mediated activation of Wingless (Wnt) signaling; pharmacological inhibition of Wnt being sufficient to abrogate inhibition of myelination by FGF2 in tissue culture. Using a novel FGFR1-selective agonist (F2 V2) generated by deleting the N-terminal 26 amino acids of FGF2 we demonstrate polarizing signal transduction to favor FGFR1 abrogates FGF mediated inhibition of myelination but retains its ability to induce expression of pro-myelinating and immunomodulatory factors that include Cd93, Lif, Il11, Hbegf, Cxcl1 and Timp1. Our data provide new insights into the mechanistic basis of remyelination failure in MS and identify selective activation of FGFR1 as a novel strategy to induce a neuroprotective signaling environment in multiple sclerosis and other neurological diseases.

Short-Term High-Flow Nasal Cannula for Moderate to Severe Bronchiolitis Is Effective in a General Pediatric Ward.

We examined the clinical and physiological benefits of heated humidified high-flow nasal cannula (HHHFNC) in treating pediatric bronchiolitis in a general pediatric ward. Children aged 0 to 2 years, hospitalized with moderate to severe bronchiolitis, were connected to HHHFNC. Each child was evaluated at 4- to 10-hour intervals, both on and off the device, using the Wang et al Bronchiolitis Severity score and transcutaneous CO2 monitor. Sixteen children were included in the final analysis. The Bronchiolitis Severity score improved by 3 points during the first and second intervals (P = .001). Transcutaneous CO2 values were reduced by an average 8.7 mm Hg (P = .001). No adverse effects were noted in children connected to the device. The HHHFNC device used in a general pediatric ward setting served as a safe and efficacious tool in treating moderate to severe bronchiolitis. Immediate clinical and physiological improvement was observed and maintained 1 to 4 hours after disconnection from the device.

Neutralizing antibody to FGFR2 can act as a selective biomarker and potential therapeutic agent for gastric cancer with FGFR2 amplification.

Fibroblast growth factor receptor 2 (FGFR2) amplification has been reported in 5-10% of gastric cancer (GC) and is associated with poor prognosis. In this study, we characterized the anti-tumor effect of PRO-007, a newly developed recombinant monoclonal antibody that targets FGFR2, in GC cell lines KATO III (with FGFR2 amplification) and NCI-N87 (without FGFR2 amplification). Validation was performed in parallel using two patient-derived tumor cells (PDCs) from patients with GC. Cell viability assays were performed using FGFR2-transfected NCI-N87 cells and FGFR2-knockdown KATO III cells that were generated using short hairpin RNA (shRNA). PRO-007 reduced KATO III cell viability (P = 0.0034) but not that of NCI-N87 cells (P = 0.3710). PRO-007 also significantly reduced KATO III cell invasiveness (P < 0.0001) but not NCI-N87 cell invasiveness (P = 0.8136). Immunoblot analysis showed that PRO-007 treatment decreased the levels of phosphorylated AKT and ERK. The FGFR2-inhibitory activity of PRO-007 was confirmed in genetically modified GC cell lines. Cell viability of FGFR2-overexpressing NCI-N87 cells was significantly decreased by PRO-007, while KATO III cells were significantly resistant to the treatment when FGFR2 was knocked down by FGFR2 shRNA transfection. Furthermore, PRO-007 had a synergistic effect with ramucirumab on the invasiveness of cancer cells with FGFR2 amplification. Consistent results were obtained using PDCs from patients with GC. Overall, these preclinical data support the further clinical development of PRO-007 as a potential therapeutic agent for patients with FGFR2-amplified GC.

Efficacy and Safety of a Weight-based Dosing Regimen of Valganciclovir for Cytomegalovirus Prophylaxis in Pediatric Solid-organ Transplant Recipients.

BACKGROUND: Valganciclovir has been widely used for cytomegalovirus (CMV) prophylaxis in solid-organ transplant recipients. However, the optimal dosing protocol and target exposure in children are still unclear. Specific data as to the efficacy and safety of low-dose/low-exposure regimens are lacking and urgently needed. METHODS: During 2010 to 2015, the clinical efficacy and safety of a weight-based regimen of valganciclovir of 17 mg/kg/day, with a stratified dose reduction for impaired creatinine clearance, given as a CMV prophylaxis for 3 to 6 months, was retrospectively evaluated among pediatric kidney and liver transplant recipients, 12 months posttransplantation. Incidence of CMV infection was assessed by periodic measurements of viral load; adverse events were evaluated. RESULTS: Eighty-three children who had undergone 86 transplantations and were treated with 17 mg/kg of valganciclovir were included. Median age was 9.77 years (range, 0.6 to 18.9). Twelve (14%) developed CMV infection: 1 during prophylaxis and 11 during follow-up. These events comprised 6 cases of asymptomatic viremia and 6 cases of a clinically significant disease without occurrences of tissue-invasive disease. Treatment-related adverse effects occurred in 7 patients (8%), mostly hematological, resulting in premature drug cessation. CONCLUSIONS: Our results support the use of 17 mg/kg of valganciclovir for CMV prophylaxis in liver and kidney transplanted children as it showed satisfactory long-term efficacy and a good safety profile.

Pediatric Infectious Sacroiliitis: Characterization and Differentiation from Noninfectious Etiologies.

BACKGROUND: Pediatric sacroiliitis (SI) is an uncommon entity of infectious or inflammatory etiology. Recent data regarding pediatric SI are scarce. The study objective was to describe and compare the clinical features of pediatric infectious and noninfectious SI. METHODS: We reviewed files of children ≤18 years of age, admitted with SI in 2004-2017. Patients were grouped by etiology, infectious versus noninfectious. Clinical and laboratory indices, imaging, treatment protocols and outcome were compared. RESULTS: Study population included 40 patients with infectious SI (range: 3-192 months, median age: 15 months, 45% female) and 13 patients with noninfectious SI (range: 30-216 months, median age: 168 months, 62% females). Duration of symptoms before admission averaged 5.9 ± 7.5 days in the infectious group and 54.2 ± 96 days in the noninfectious group (P = 0.003). Symptoms observed solely in the infectious group included refusal to stand (n = 27, 77%); walk or crawl (n = 24, 65%); irritability (n = 20, 50%) and recent constipation event (n = 8, 20%). No significant differences in laboratory results were found. Infectious SI patients had uneventful medical history, rapid response to antibiotics and a higher rate of complete resolution of symptoms without recurrences. CONCLUSIONS: An acute unilateral presentation in young patients ≤2 years of age, without chronic medical conditions, suggests an infectious etiology of SI anticipated to completely resolve with antibiotic treatment, not necessitating further workup for noninfectious etiologies.

Primary infection with human herpes virus type 6, post-pediatric liver transplantation-A pathogen to remember.

BACKGROUND: In recent years, liver transplantation (LT) has become a well-accepted therapeutic modality for children with end-stage liver disease, with transplantation surgery being performed at a younger age. Human herpes virus 6 (HHV-6) infection occurs in most children within the first 2 years of life, therefore, data on primary HHV-6 infection in pediatric liver transplant recipients is scarce. OBJECTIVE: To describe the course of primary HHV-6 infection after pediatric LT. METHODS: Medical files, between the years 2015-2016, of post-LT pediatric patients with suspected primary HHV-6 infection were reviewed. Clinical and laboratory data for enrolled cases were evaluated. Primary infection was defined as DNAemia in children who were seronegative prior to transplantation or seroconversion from negative to positive IgG posttransplantation. RESULTS: Four cases of primary HHV-6 (type B) infection were identified among the 26 children who had undergone LT at our center during the study period. All patients were <1 year old and presented with fever, hepatitis, and elevated inflammatory markers, most (75%) within a short-period posttransplantation. All were initially treated with empiric antibiotics for a suspected bacterial infection and three underwent liver biopsy, one showing signs of rejection. Three were treated with antiviral therapy with a gradual resolution of symptoms. DISCUSSION: Primary HHV-6 should be taken into account in young children shortly after LT, especially when presenting with fever and elevated liver enzymes. Treatment with antiviral therapy should be considered. CONCLUSIONS: In young infants post-LT, a high index of suspicion may promote early detection of HHV-6 primary infection and prevent serious complications.

Risk factors for early invasive fungal infections in paediatric liver transplant recipients.

Invasive fungal infections (IFIs) postliver transplantation are a frequent cause of morbidity and mortality; however, studies reporting on these infections in the paediatric population are scarce. To investigate the incidence and risk factors of IFIs in paediatric liver transplant recipients during the early posttransplantation period (≤3 months). Data were collected for all paediatric liver transplant recipients registered in a national transplantation center from 2004 to 2014. Using a stepwise logistic regression to identify independent risk factors for IFIs, a predictive model was formulated. Ten IFIs were identified in 81 liver transplant recipients (12.3%) all occurring during the first month posttransplantation. Candida species were responsible for nine cases (90%), of which four were non-albicans Candida (44%). Significant risk factors were identified; recipient of multiple blood product transfusions during transplantation, prolonged use of indwelling intravenous catheter, prolonged IV antibiotic treatment, surgical complications, pulse steroid treatment and living donor liver transplantation. The predictive model used two clinical parameters to define high-risk patients: a living donor transplantation and duration of IV antibiotic treatment (area under the ROC curve 0.918). IFIs are a significant complication occurring in the first month posttransplantation. Future studies are required to assess efficacy of targeted antifungal prophylaxis in high risk patients.

Protracted febrile myalgia syndrome treated with pulse of corticosteroids.

OBJECTIVE: This study describes our 5-year experience treating protracted febrile myalgia syndrome (PFMS) with pulsed doses of corticosteroids. METHODS: Eight patients with PFMS who received pulse corticosteroid therapy were identified from the electronic database of a tertiary pediatric medical center (2011-2016). Their clinical and laboratory data were collected. Differences in continuous variables between hospital admission and discharge were analyzed using Wilcoxon's matched pairs test. RESULTS: There were 6 female and 2 male patients of median age 10.45 years (range 6.2-17.1) Six patients were found to be homozygous for the M694V mutation. In 4 patients, PFMS was the first-ever manifestation of familial Mediterranean fever. Pulse corticosteroid therapy was administered at a dose of 10mg/kg for 3 days. Pain was alleviated (visual analog scale score, 0) within hours of initiation of therapy, although pain flare-ups lasting for minutes to hours were still observed during hospitalization. At discharge, all patients were prescribed continuous oral corticosteroids (1-2mg/kg) with gradual tapering down over 6 weeks. CONCLUSION: Pulse corticosteroid therapy is effective in alleviating PFMS pain; however, it does not completely abort a PFMS episode.

Real-life comparison of three general paediatric wards showed similar outcomes for children with bronchiolitis despite different treatment regimens.

AIM: This study evaluated the effectiveness of three different treatments for bronchiolitis in a tertiary paediatric facility. METHODS: Patients with bronchiolitis who were younger than two years of age and were randomly allocated to three general wards at Schneider Children's Medical Center, Israel, after admission were included. Different treatment protocols in the wards were retrospectively compared. RESULTS: The study comprised 286 children. The clinical and laboratory parameters on admission were similar between the wards. In Ward C where nebulised hypertonic saline was infrequently administered (6.7%), the mean number of days with oxygen saturation under 92% and the meanlength of hospital stay (1.8 and 3.8 days) were significantly lower than Ward A (2.8 and 5.3 days) and Ward B, (2.9 and 4.7 days) where nebulised hypertonic saline was given more frequently (38.7%-74.7%). Multivariate analysis indicated that low saturation on admission, leukocytosis and use of nebulised hypertonic saline or adrenalin were independent predictors of a longer period of desaturation and hospital stay. CONCLUSION: Different treatment protocols for bronchiolitis were used in three paediatric wards in this real-life study. No treatment regimen proved superior. Inhalations of hypertonic saline or adrenaline were associated with a longer hospital stay.

Valganciclovir Dosing for Cytomegalovirus Prophylaxis in Pediatric Solid-organ Transplant Recipients: A Prospective Pharmacokinetic Study.

BACKGROUND: Valganciclovir is extensively used for prophylaxis and treatment of cytomegalovirus (CMV) infection in solid-organ transplant recipients. However, pharmacokinetic data in children are scarce, and the pediatric dosing regimen is uncertain. This study sought to prospectively evaluate the pharmacokinetic profile, the clinical efficacy and safety of oral valganciclovir in pediatric transplant recipients and compare different dosing regimens. METHODS: The cohort included solid-organ transplant recipients treated with valganciclovir for CMV prophylaxis in 2014-2015 at a tertiary pediatric medical center. All received a weight-based once-daily oral dose of 17 mg/kg. Ganciclovir concentrations were measured and the area under the curve (AUC0-24) was calculated. RESULTS: Thirteen children of median age 7.3 years (interquartile range, 2.2-11.6) were included. Median ganciclovir AUC0-24 was 21.0 mcg·h/mL (interquartile range, 17.1-39.8); 10 patients (77%) attained AUC0-24 <40 mcg·h/mL. Exposure to ganciclovir was about 2-fold lower in young children (<9 years old; P = 0.01) and children with low body surface area (BSA; <0.7 m; P = 0.006) than in their counterparts. Significantly lower doses were recommended with our weight-based protocol than with the manufacturer-recommended BSA- and glomerular filtration rate-based protocol (P = 0.002), reaching a 3-fold difference in infants. No evidence of CMV viremia or disease was observed while prophylaxis was given. CONCLUSIONS: The weight-based regimen of 17 mg/kg/dose oral valganciclovir results in relatively low ganciclovir exposure, especially in young children with low BSA, yet showed satisfactory clinical efficacy for CMV prophylaxis. The manufacturer's dosing recommendation appears to result in supratherapeutic ganciclovir concentrations. Further studies are needed to establish target AUCs and valganciclovir dosing for CMV prophylaxis in pediatric transplant recipients.

Children after renal transplantation hospitalized for fever: Is empirical antibiotic treatment always justified?

Infections are a major cause of morbidity and mortality after renal transplantation. However, data focusing on children are scarce. The objective of this study was to investigate the frequency and predictors of bacterial infection in pediatric renal transplant recipients in a specific setting of hospitalization due to fever. Clinical and laboratory data were retrospectively collected for all pediatric renal transplant recipients hospitalized for fever in a national renal transplantation center from 2004 to 2012. One hundred and sixty-eight hospital admissions for fever of 52 children were analyzed. A bacterial etiology was diagnosed in 85 admissions (50.6%); 49 cases (57.6%) were documented microbiologically and 36 (42.4%) clinically. Risk factors and markers of bacterial infection included older age, presence of a central venous catheter, sonographic findings, and elevated inflammatory indices. C-reactive protein level was a more sensitive marker than white blood cell count and absolute neutrophil count. In patients without identified risk factors, no bacterial infections were diagnosed. Pediatric renal transplant recipients hospitalized for fever are at high risk of bacterial infections and usually require empirical antibiotic treatment at admission. However, there is a minority of low-risk patients in whom clinicians may consider withholding antibiotic treatment with close follow-up.

[INSPIRATORY STRIDOR OF A NON-TRADITIONAL CAUSE].

INTRODUCTION: Stridor is a respiratory sound caused by turbulent air flow through narrow airways. The most common cause for acute inspiratory stridor is a viral infection of the upper airways, causing laryngotracheitis (Croup). Other common causes include an allergic reaction, foreign body aspiration and trauma. BACKGROUND: A nine week old infant with a history of meningomyelocele repair perinatally presented to the emergency room with alternating inspiratory stridor. The infant did not have a history of a recent febrile illness, and he did not suffer from cough or any other symptoms suggesting a foreign body aspiration. After the common causes of stridor were ruled out, an MRI was performed - demonstrating Chiari malformation Type 2, with herniation of the cerebellar tonsils and medullary compression. Bronchoscopy demonstrated the rare cause of the intermittent stridor - intermittent vocal cord paralysis, caused by the raised intracranial pressure and medullary compression. Due to rapid clinical deterioration, emergent surgical decompression was performed with complete recovery. CONCLUSIONS: This case report raises a rare and important cause of inspiratory stridor. Physicians should be alert to the symptoms suggesting a Chiari malformation in every child with a relevant medical history presenting with stridor. DISCUSSION: Intermittent stridor is mostly caused by an upper respiratory infection in a child with narrowed airways, allergic laryngotracheitis, or laryngomalacia. A less common cause of stidor of this kind is vocal cord paralysis, which may be caused by a symptomatic Chiari malformation.

Inhibition of tumor angiogenesis and growth by a small-molecule multi-FGF receptor blocker with allosteric properties.

Receptor tyrosine kinases (RTK) are targets for anticancer drug development. To date, only RTK inhibitors that block orthosteric binding of ligands and substrates have been developed. Here, we report the pharmacologic characterization of the chemical SSR128129E (SSR), which inhibits fibroblast growth factor receptor (FGFR) signaling by binding to the extracellular FGFR domain without affecting orthosteric FGF binding. SSR exhibits allosteric properties, including probe dependence, signaling bias, and ceiling effects. Inhibition by SSR is highly conserved throughout the animal kingdom. Oral delivery of SSR inhibits arthritis and tumors that are relatively refractory to anti-vascular endothelial growth factor receptor-2 antibodies. Thus, orally-active extracellularly acting small-molecule modulators of RTKs with allosteric properties can be developed and may offer opportunities to improve anticancer treatment.

Fibroblast growth factor 4 and its novel splice isoform have opposing effects on the maintenance of human embryonic stem cell self-renewal.

Human embryonic stem cells (HESCs) are unique in their capacity to self-renew while remaining pluripotent. This undifferentiated state must be actively maintained by secreted factors. To identify autocrine factors that may support HESC growth, we have taken a global genetic approach. Microarray analysis identified fibroblast growth factor 4 (FGF4) as a prime candidate for autocrine signaling. Furthermore, the addition of recombinant FGF4 to HESCs supports their proliferation. We show that FGF4 is produced by multiple undifferentiated HESC lines, along with a novel fibroblast growth factor 4 splice isoform (FGF4si) that codes for the amino-terminal half of FGF4. Strikingly, although FGF4 supports the undifferentiated growth of HESCs, FGF4si effectively counters its effect. Furthermore, we show that FGF4si is an antagonist of FGF4, shutting down FGF4-induced Erk1/2 phosphorylation. Expression analysis shows that both isoforms are expressed in HESCs and early differentiated cells. However, whereas FGF4 ceases to be expressed in mature differentiated cells, FGF4si continues to be expressed after cell differentiation. Targeted knockdown of FGF4 using small interfering RNA increased differentiation of HESCs, demonstrating the importance of endogenous FGF4 signaling in maintaining their pluripotency. Taken together, these results suggest a growth-promoting role for FGF4 in HESCs and a putative feedback inhibition mechanism by a novel FGF4 splice isoform that may serve to promote differentiation at later stages of development.

The inhibitory anti-FGFR3 antibody, PRO-001, is cytotoxic to t(4;14) multiple myeloma cells.

The association of fibroblast growth factor receptor 3 (FGFR3) expression with t(4;14) multiple myeloma (MM) and the demonstration of the transforming potential of this receptor tyrosine kinase (RTK) make it a particularly attractive target for drug development. We report here a novel and highly specific anti-FGFR3-neutralizing antibody (PRO-001). PRO-001 binds to FGFR3 expressed on transformed cells and inhibits FGFR3 autophosphorylation and downstream signaling. The antibody inhibited the growth of FGFR3-expressing FDCP cells (IC(50) of 0.5 microg/mL) but not that of cells expressing FGFR1 or FGFR2, and potently inhibited FGFR3-dependent solid tumor growth in a mouse xenograft model. Furthermore, PRO-001 inhibited the growth of the FGFR3-expressing, human myeloma cell line, UTMC2. Inhibition of viability was still observed when cells were cocultured with stroma or in the presence of IL-6 or IGF-1. PRO-001 did not inhibit constitutive activation of K650E, G384D, and Y373C FGFR3 in myeloma cell lines and failed to inhibit the growth of these cells. Most importantly, however, PRO-001 induced cytotoxic responses in primary t(4;14)(+) MM samples with an increase in apoptotic index of 20% to 80% as determined by annexin V staining. The data demonstrate that PRO-001 is a potent and specific inhibitor of FGFR3 and deserves further study for the treatment of FGFR3-expressing myeloma.

Distinct fibroblast growth factor (FGF)/FGF receptor signaling pairs initiate diverse cellular responses in the oligodendrocyte lineage.

Fibroblast growth factors (FGFs) have been implicated in numerous cellular processes, including proliferation, migration, differentiation, and survival. Whereas FGF-2, the prototypic ligand in a family of 22 members, activates all four tyrosine kinase FGF receptors (FGFR1-FGFR4), other members demonstrate a higher degree of selectivity. Oligodendrocytes (OLs), the myelin-producing cells of the CNS, are highly influenced by FGF-2 at all stages of their development. However, how other FGFs and their cognate receptors orchestrate the development of OLs is essentially undefined. Using a combination of specific FGF ligands and receptor blocking antibodies, we now show that FGF-8 and FGF-17 target OL progenitors, inhibiting their terminal differentiation via the activation of FGFR3, whereas FGF-9 specifically targets differentiated OLs, triggering increases in process growth via FGFR2 signaling; FGF-18 targets both OL progenitors and OLs via activation of both FGFR2 and FGFR3. These events are highly correlated with changes in FGF receptor expression from FGFR3 to FGFR2 as OL progenitors differentiate into mature OLs. In addition, we demonstrate that, although activation of FGFR1 by FGF-2 leads to proliferation of OL progenitors, it produces deleterious effects on differentiated OLs (i.e., aberrant reentry into cell cycle and down-regulation of myelin proteins with a loss of myelin membrane). These data suggest that ligand availability, coupled with changes in FGF receptor expression, yield a changing repertoire of ligand-receptor signaling complexes that contribute critically to the regulation of both normal OL development and potential OL/myelin pathogenesis.

Human combinatorial Fab library yielding specific and functional antibodies against the human fibroblast growth factor receptor 3.

The human combinatorial antibody library Fab 1 (HuCAL-Fab 1) was generated by transferring the heavy and light chain variable regions from the previously constructed single-chain Fv library (Knappik, A., Ge, L., Honegger, A., Pack, P., Fischer, M., Wellnhofer, G., Hoess, A., Wölle, J., Plückthun, A., and Virnekäs, B. (2000) J. Mol. Biol. 296, 57-86), diversified in both complementarity-determining regions 3 into a novel Fab display vector, yielding 2.1 x 10(10) different antibody fragments. The modularity has been retained in the Fab display and screening plasmids, ensuring rapid conversion into various antibody formats as well as antibody optimization using prebuilt maturation cassettes. HuCAL-Fab 1 was challenged against the human fibroblast growth factor receptor 3, a potential therapeutic antibody target, against which, to the best of our knowledge, no functional antibodies could be generated so far. A unique screening mode was designed utilizing recombinant functional proteins and cell lines differentially expressing fibroblast growth factor receptor isoforms diversified in expression and receptor dependence. Specific Fab fragments with subnanomolar affinities were isolated by selection without any maturation steps as determined by fluorescence flow cytometry. Some of the selected Fab fragments completely inhibit target-mediated cell proliferation, rendering them the first monoclonal antibodies against fibroblast growth factor receptors having significant function blocking activity. This study validates HuCAL-Fab 1 as a valuable source for the generation of target-specific antibodies for therapeutic applications.

Insight into Schmid metaphyseal chondrodysplasia from the crystal structure of the collagen X NC1 domain trimer.

Collagen X is expressed specifically in the growth plate of long bones. Its C1q-like C-terminal NC1 domain forms a stable homotrimer and is crucial for collagen X assembly. Mutations in the NC1 domain cause Schmid metaphyseal chondrodysplasia (SMCD). The crystal structure at 2.0 A resolution of the human collagen X NC1 domain reveals an intimate trimeric assembly strengthened by a buried cluster of calcium ions. Three strips of exposed aromatic residues on the surface of NC1 trimer are likely to be involved in the supramolecular assembly of collagen X. Most internal SMCD mutations probably prevent protein folding, whereas mutations of surface residues may affect the collagen X suprastructure in a dominant-negative manner.