[Progress of researches on the antiparasitic activity of antimicrobial peptide LL-37]

Parasitic diseases caused by protozoan and helminth infections are still widespread across the world, notably in tropical and subtropical areas, which threaten the children and adult health. Long-term use of anti-parasitic drugs may result in reduced drug susceptibility and even drug resistance. Antimicrobial peptides have been demonstrated to inhibit parasite growth and development, which has potential antiparasitic values. LL-37, the only human antimicrobial peptide in the cathelicidin family, has been widely investigated. This paper reviews the progress of researches on the antiparasitic activity of LL-37, and discusses the prospects of LL-37 in the research of parasites.

Single-Cell Transcriptomic Analysis of Dental Pulp and Periodontal Ligament Stem Cells

The regeneration of periodontal, periapical, and pulpal tissues is a complex process requiring the direct involvement of cells derived from pluripotent stem cells in the periodontal ligament and dental pulp. Dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) are spatially distinct with the potential to differentiate into similar functional and phenotypic cells. We aimed to identify the cell heterogeneity of DPSCs and PDLSCs and explore the differentiation potentials of their specialized organ-specific functions using single-cell transcriptomic analysis. Our results revealed 7 distinct clusters, with cluster 3 showing the highest potential for differentiation. Clusters 0 to 2 displayed features similar to fibroblasts. The trajectory route of the cell state transition from cluster 3 to clusters 0, 1, and 2 indicated the distinct nature of cell differentiation. PDLSCs had a higher proportion of cells (78.6%) at the G1 phase, while DPSCs had a higher proportion of cells at the S and G2/M phases (36.1%), mirroring the lower cell proliferation capacity of PDLSCs than DPSCs. Our study suggested the heterogeneity of stemness across PDLSCs and DPSCs, the similarities of these 2 stem cell compartments to be potentially integrated for regenerative strategies, and the distinct features between them potentially particularized for organ-specific functions of the dental pulp and periodontal ligament for a targeted regenerative dental tissue repair and other regeneration therapies.

Modes and Mechanisms of Pacific Decadal-Scale Variability

The modes of Pacific decadal-scale variability (PDV), traditionally defined as statistical patterns of variance, reflect to first order the ocean's integration (i.e., reddening) of atmospheric forcing that arises from both a shift and a change in strength of the climatological (time-mean) atmospheric circulation. While these patterns concisely describe PDV, they do not distinguish among the key dynamical processes driving the evolution of PDV anomalies, including atmospheric and ocean teleconnections and coupled feedbacks with similar spatial structures that operate on different timescales. In this review, we synthesize past analysis using an empirical dynamical model constructed from monthly ocean surface anomalies drawn from several reanalysis products, showing that the PDV modes of variance result from two fundamental low-frequency dynamical eigenmodes: the North Pacific-central Pacific (NP-CP) and Kuroshio-Oyashio Extension (KOE) modes. Both eigenmodes highlight how two-way tropical-extratropical teleconnection dynamics are the primary mechanisms energizing and synchronizing the basin-scale footprint of PDV. While the NP-CP mode captures interannual- to decadal-scale variability, the KOE mode is linked to the basin-scale expression of PDV on decadal to multidecadal timescales, including contributions from the South Pacific.

Comparison of clinical diagnostic value of spiral CT with different dose in patients with early-stage peripheral lung cancer

PURPOSE

To compare the clinical diagnostic value of spiral CT scan with different dose in patients with early-stage peripheral lung cancer.

METHODS

A total of 163 cases of patients with early-stage peripheral lung cancer who came to People's Hospital of Rizhao for treatment from June 2014 to January 2017 were retrospectively analyzed. A total of 78 cases of patients who received low-dose CT scanning were the low-dose group, another 84 cases of patients who received routine dose CT scanning were the routine dose group. Multislice helical CT (MSCT) scanning was performed in both groups, with tube voltage of 120 kV. Tube current was 25 m A in the low-dose group and 250 m A in the routine dose group. In addition, a total of 80 patients with lobar pneumonia were added as the control group of diagnostic sensitivity, specificity and accuracy. Pathological diagnosis was taken as the gold standard to compare the diagnostic sensitivity, specificity and accuracy of the two groups.

RESULTS

The image quality, nodules and signs of the two groups were compared, and the results of radiation dose of the two groups were compared. The diagnostic sensitivity, specificity and accuracy of the low-dose group were 82.05%, 87.50% and 84.81%, respectively. The diagnostic sensitivity, specificity and accuracy of the routine dose group were 85.71%, 86.25% and 85.97%, respectively. The diagnostic value of the two groups was not statistically significant (p > 0.05). However, the radiation dose in the low-dose group was significantly lower than that in the routine group.

CONCLUSION

Low-dose MSCT scanning can meet the clinical requirements for imaging diagnosis of peripheral lung cancer, and can reduce the radiation dose of patients.

Coronavirus disease 2019: a bibliometric analysis and review

OBJECTIVE

On December 8, 2019, many cases of pneumonia with unknown etiology were first reported in Wuhan, China, subsequently identified as a novel coronavirus infection aroused worldwide concern. As the outbreak is ongoing, more and more researchers focused interest on the COVID-19. Therefore, we retrospectively analyzed the publications about COVID-19 to summarize the research hotspots and make a review, to provide reference for researchers in the world.

MATERIALS AND METHODS

We conducted a search in PubMed using the keywords "COVID-19" from inception to March 1, 2020. Identified and analyzed the data included title, corresponding author, language, publication time, publication type, research focus.

RESULTS

183 publications published from 2020 January 14 to 2020 February 29 were included in the study. The first corresponding authors of the publications were from 20 different countries. Among them, 78 (42.6%) from the hospital, 64 (35%) from the university and 39 (21.3%) from the research institution. All the publications were published in 80 different journals. Journal of Medical Virology published most of them (n=25). 60 (32.8%) were original research, 29 (15.8%) were review, 20 (10.9%) were short communications. 68 (37.2%) epidemiology, 49 (26.8%) virology and 26 (14.2%) clinical features.

CONCLUSIONS

According to our review, China has provided a large number of research data for various research fields, during the outbreak of COVID-19. Most of the findings play an important role in preventing and controlling the epidemic around the world. With research on the COVID-19 still booming, new vaccine and effective medicine for COVID-19 will be expected to come out in the near future with the joint efforts of researchers worldwide.

Numerical and experimental studies of water disinfection in UV reactors

Performance of UV reactors for water disinfection is investigated in this paper. Both experimental and numerical studies are performed on base reactor LP24. Enterobacteria phage MS2 is chosen as the challenge microorganism in the experiments. Experiments are conducted to evaluate the effect of different parameters, i.e. flow rate and UV transmission, on the reactor performance. Simulation is carried out based on the commercial software ANSYS FLUENT with user defined functions (UDFs) implemented. The UDF is programmed to calculate UV dose absorbed by different microorganisms along their flow trajectories. The effect with boundary layer mesh and without boundary layer mesh for LP24 is studied. The results show that the inclusion of boundary layer mesh does not have much effect on the reactor performance in terms of reduction equivalent dose (RED). The numerical results agree well with the experimental measurements, hence validating the numerical model. With this achieved, the numerical model is applied to study other scaled reactors: LP12, LP40, LP60 and LP80. Comparisons show that LP40 has the highest RED and log inactivation among all the reactors while LP80 has the lowest RED and log inactivation.

A polymorphic MYC response element in KBTBD11 influences colorectal cancer risk, especially in interaction with an MYC-regulated SNP rs6983267

Background

MYC is a well-established cancer driver gene regulating the expression of numerous genes, indicating that polymorphisms in MYC response elements could affect tumorigenesis through altering MYC regulation. We performed integrative multistage study to evaluate the effects of variants in MYC response elements and colorectal cancer (CRC) risk.

Patients and methods

We systematically integrated ChIP-Seq, DNase-Seq and transcription factor motif data to screen variants with potential ability to affect the MYC binding affinity. Then, we conducted a two-stage case-control study, totally consisting of 4830 CRC cases and 4759 controls in Chinese population to identify risk polymorphisms and interactions. The effects of risk variants were confirmed by functional assays in CRC LoVo, SW480 and HCT15 cells.

Results

We identified a novel polymorphism rs11777210 in KBTBD11 significantly associated with CRC susceptibility (P = 2.43 × 10-12). Notably, we observed a significant interaction between rs11777210 and MYC nearby rs6983267 (P-multi = 0.003, P-add = 0.005), subjects carrying rs6983267 GG and rs11777210 CC genotypes showing higher susceptibility to CRC (2.83-fold) than those carrying rs6983267 TT and rs11777210 TT genotypes. We further demonstrated that rs6983267 T > G increased MYC expression, and MYC bound to and negatively regulated KBTBD11 expression when the rs11777210 C risk allele was present. KBTBD11 was downregulated in tumor tissues, and KBTBD11 knockdown promoted cell proliferation and inhibited cell apoptosis.

Conclusion

The rs11777210 is a potential predictive biomarker of CRC susceptibility, and KBTBD11 functions as a putative tumor suppressor in tumorigenesis. Our study highlighted the high CRC risk of people carrying rs6983267 G and rs11777210 C alleles, and provided possible biological mechanism of the interaction.

Establishment of a Quantitative Polymerase Chain Reaction Assay for Monitoring Chimeric Antigen Receptor T Cells in Peripheral Blood

BACKGROUND

The chimeric antigen receptor (CAR) consists of an antigen recognition moiety from a monoclonal antibody fused to an intracellular signalling domain capable of activating T cells. The specific structure of the CAR molecule has been used in various basic research and clinical settings to detect CAR expression, but it is necessary to develop more specific and simpler monitoring methods to observe real-time changes.

MATERIALS AND METHODS

To develop a quantitative assay for the universal detection of DNA from anti-CD19 CAR-T cells, a TaqMan real-time quantitative polymerase chain reaction (qPCR) assay was developed using primers based on FMC63-28Z gene sequences. We identified the numbers of copies of CAR gene on T cells transduced with the CAR gene that were obtained from peripheral blood.

RESULTS

The assay had a minimum detection limit of 10 copies/μL and a strong linear standard curve (y = -3.3682x + 38.594; R² = 0.999) within the range of the input CAR gene (10-10⁷ copies/μL). The reproducibility test showed a coefficient of variation ranging from 0.63%-1.65%. Real-time qPCR is a highly sensitive, specific, reproducible, and universal method that can be used to detect anti-CD19 CAR-T cells in peripheral blood.

Dysfunction of the WT1-MEG3 signaling promotes AML leukemogenesis via p53-dependent and -independent pathways

Long non-coding RNAs (lncRNAs) play a pivotal role in tumorigenesis, exemplified by the recent finding that lncRNA maternally expressed gene 3 (MEG3) inhibits tumor growth in a p53-dependent manner. Acute myeloid leukemia (AML) is the most common malignant myeloid disorder in adults, and TP53 mutations or loss are frequently detected in patients with therapy-related AML or AML with complex karyotype. Here, we reveal that MEG3 is significantly downregulated in AML and suppresses leukemogenesis not only in a p53-dependent, but also a p53-independent manner. In addition, MEG3 is proven to be transcriptionally activated by Wilms’ tumor 1 (WT1), dysregulation of which by epigenetic silencing or mutations is causally involved in AML. Therefore MEG3 is identified as a novel target of the WT1 molecule. Ten–eleven translocation-2 (TET2) mutations frequently occur in AML and significantly promote leukemogenesis of this disorder. In our study, TET2, acting as a cofactor of WT1, increases MEG3 expression. Taken together, our work demonstrates that TET2 dysregulated WT1-MEG3 axis significantly promotes AML leukemogenesis, paving a new avenue for diagnosis and treatment of AML patients.

Fabrication of HA/PEI-functionalized carbon dots for tumor targeting, intracellular imaging and gene delivery

Carbon quantum dots (CDs) as emerging carbon nano-materials have attracted tremendous attention in biomedical fields due to unique properties.

Effect of ozone on vascular endothelial growth factor (VEGF) and related inflammatory cytokines in rats with diabetic retinopathy

The aim of this study was to investigate the effect of ozone on inflammatory cytokines in diabetic retinopathy (DR) rats. Male rats (40) weighing 300-360 g were included in this study. Thirty rats were randomly divided into the model and ozone groups after DR was induced by streptozotocin. Ten rats served as the blank group. After the diabetic models were established for one month, the rats in the ozone group were treated with 50 mg/kg ozone coloclysis for one month (three times a week). After the rats were anesthetized by intraperitoneal injection, blood samples from the abdominal aorta were collected, and the supernatant was obtained by centrifugation. Vascular endothelial growth factor (VEGF) and inflammatory cytokine content in the serum was detected by enzyme linked immunosorbent assay. The values of VEGF, intercellular cell adhesion molecule-1, interleukin-1 beta, tumor necrosis factor-a, and IL-6 were significantly different among the three groups (P < 0.05). The cytokine levels in the model group were higher than those in the blank group (P < 0.05). The level of each cytokine in the ozone group was higher than that in the blank group. Compared with the model group, the cytokine levels in the ozone group were significantly reduced (P < 0.05). Ozone had no effect on the blood glucose of diabetic rats. Treatment with ozone coloclysis may effectively reduce the secretion of VEGF and inflammatory cytokines in diabetic retinopathy rats.

Resonant surface plasmon-exciton interaction in hybrid MoSe2@Au nanostructures

In this work we investigate the interaction between plasmonic and excitonic resonances in hybrid MoSe2@Au nanostructures. The latter were fabricated by combining chemical vapor deposition of MoSe2 atomic layers, Au disk processing by nanosphere lithography and a soft lift-off/transfer technique. The samples were characterized by scanning electron and atomic force microscopy. Their optical properties were investigated experimentally using optical absorption, Raman scattering and photoluminescence spectroscopy. The work is focused on a resonant situation where the surface plasmon resonance is tuned to the excitonic transition. In that case, the near-field interaction between the surface plasmons and the confined excitons leads to interference between the plasmonic and excitonic resonances that manifests in the optical spectra as a transparency dip. The plasmonic-excitonic interaction regime is determined using quantitative analysis of the optical extinction spectra based on an analytical model supported by numerical simulations. We found that the plasmonic-excitonic resonances do interfere thus leading to a typical Fano lineshape of the optical extinction. The near-field nature of the plasmonic-excitonic interaction is pointed out experimentally from the dependence of the optical absorption on the number of monolayer stacks on the Au nanodisks. The results presented in this work contribute to the development of new concepts in the field of hybrid plasmonics.

Prenatal Iron Deficiency and Auditory Brainstem Responses at 3 and 10 Months: A Pilot Study

PURPOSE

To examine whether prenatal iron deficiency delays auditory brainstem response (ABR) maturation in infancy.

METHODS

One hundred and fifteen full-term healthy Chinese infants with maternal and cord blood haemoglobin and serum ferritin determinations were recruited into this study. Forty-eight infants received ABR testing at 3 months, and 45 infants were tested at 10 months. Comparison of the ABR variables were made between infants with and those without evidence of prenatal iron deficiency (maternal 3rd trimester haemoglobin <110 g/L, cord blood ferritin <75 μg/L); or anaemia at 10 months (haemoglobin <110 g/L).

RESULTS

Latencies for wave V and wave III-V and I-V intervals were prolonged at 3 months in infants of anaemic mothers (effect sizes 1.02-1.19 SD). At 10 months, infants with low cord blood serum ferritin (indicating low iron stores at birth) showed longer wave I latency and possibly wave V latency also, besides demonstrating a smaller wave V amplitude (effect sizes 0.58-0.62 SD). Infants with low ferritin at birth and anemia at 10 months had longer wave III-V latency than other groups.

CONCLUSION

In full-term healthy infants, prenatal iron deficiency appears to have adverse effects on the developing central nervous system and auditory system as assessed by ABRs at 3 and/or 10 months.

Hyaluronic acid functionalized nitrogen-doped carbon quantum dots for targeted specific bioimaging

Schematic illustration of the preparation of HA-CQDs (A) and the following bioimaging application (B).

A meta analysis of cetuximab plus oxaliplatin based chemotherapy regimen for metastatic colorectal cancer

BACKGROUND

Oxaliplatin based chemotherapy regimen was one of the most used chemotherapy modality for metastatic colorectal cancer. The purpose of this meta-analysis was to assess the clinical activity and toxicities of cetuximab plus oxaliplatin-based chemotherapy regimen for metastatic colorectal Cancer.

METHODS

We searched the clinical studies about the cetuximab plus oxaliplatin-based chemotherapy regimen versus oxaliplatin-based chemotherapy alone for metastatic colorectal cancer in the databases of PubMed, EMBASE, Cochran, and CNKI. The data of response and toxicities were extracted and pooled by random or fixed effects model. And publication bias was evaluated by begg's funnel plot and egger's regression test.

RESULTS

Seven papers were included in this study. Adding cetuximab to oxaliplatin-based chemotherapy regime can significant increase response rate in K-RAS mutation metastatic colorectal patients (odds ratio [OR]: 1.45, 95% confidence interval [CI]: 1.17-1.80, Z = 3.38, P = 0.001) and metastatic colorectal patients without knowing the K-RAS status (OR: 1.36, 95% CI: 1.11-1.65, Z = 1.89, P = 0.003). But for patients with mutated K-RAS, the improvement for objective response rate was not statistical significant (OR: 0.70, 95% CI: 0.49-1.01, Z = 3.00, P = 0.058) when adding cetuximab to oxaliplatin-based chemotherapy regime. The pooled results indicating the rash and diarrhea risk was significantly increased in the combined treatment group (P < 0.05). The toxicity of peripheral neuritis was decreased by adding the cetuximab (P < 0.05). And other toxicities were not statistical different between the two groups (P > 0.05). Significant publication bias was found in toxicities evaluation.

CONCLUSION

Cetuximab plus oxaliplatin-based chemotherapy regimen significant increase the response rate for metastatic colorectal cancer. But the some toxicities such rash and diarrhea risk was also increased.

Effect of different time phases of radionuclide hepatobiliary scintigraphy on the differential diagnosis of congenital biliary atresia

To investigate the value and essentiality of 6- and 24-h delay hepatobiliary scintigraphy in the differential diagnosis of biliary atresia (BA), we retrospectively analyzed 197 infants (121 boys/76 girls; age range, 3-205 days; average age, 63.9 days) admitted to Jiangxi Children's Hospital for persistent jaundice (> 2 weeks), hepatosplenomegaly, and abnormal liver function. After receiving anti-inflammatory treatment and cholagogic pre-treatment for 7-10 days without a clear diagnosis, the children underwent 99mTc-labeled diethylacetanilide-iminodiacetic acid hepatobiliary scintigraphy. BA and infant hepatitis syndrome were diagnosed in 107 and 90 infants, respectively after laparoscopic cholangiography, surgical pathology, or 6-month clinical follow-up. The diagnostic efficiencies of hepatobiliary scintigraphy for BA were evaluated within 50 min and at 6 and 24 h. The areas under the receiver operating characteristic curves within 50 min, at 6 and 24 h were 0.696, 0.829 , and 0.779 , suggesting poor diagnostic value within 50 min, but improvement at 6 and 24 h. The compliance rate of 6- and 24-h imaging for BA diagnosis was 89.34% (176/197; paired chi-square test Kappa value, 0.77; P > 0.05), signifying high consistency. The diagnostic efficiency values of 6-/24-h imaging for BA diagnosis were sensitivity (90.65/89.72%), specificity (74.44/78.89%), accuracy (83.25/84.77%), positive and negative predictive values (80.83/83.48% and 87.01/86.59%), with no significant difference (P > 0.05). To provide optimal treatment in early BA, the- 6-h hepatobiliary scintigraphy had practical value, especially when combined with tomographic or dynamic imaging; 24-h delay imaging was deemed unnecessary because it was not significantly superior.

On-chip lithium cells for electrical and structural characterization of single nanowire electrodes

We present a transmission electron microscopy (TEM)-compatible, hybrid nanomachined, on-chip construct for probing the structural and electrical changes in individual nanowire electrodes during lithium insertion. We have assembled arrays of individual β-phase manganese dioxide (β-MnO2) nanowires (NWs), which are employed as a model material system, into functional electrochemical cells through a combination of bottom-up (dielectrophoresis) and top-down (silicon nanomachining) unit processes. The on-chip NWs are electrochemically lithiated inside a helium-filled glovebox and their electrical conductivity is studied as a function of incremental lithium loading during initial lithiation. We observe a dramatic reduction in NW conductivity (on the order of two to three orders in magnitude), which is not reversed when the lithium is extracted from the nanoelectrode. This conductivity change is attributed to an increase in lattice disorder within the material, which is observed from TEM images of the lithiated NWs. Furthermore, electron energy loss spectroscopy (EELS) was employed to confirm the reduction in valence state of manganese, which occurs due to the transformation of MnO2 to LixMnO2.

Quantitative analysis of the temperature dependency in Raman active vibrational modes of molybdenum disulfide atomic layers

Raman spectroscopy is utilized to quantify the temperature dependency of the vibrational modes in molybdenum disulfide (MoS2) atomic layers. These analyses are essential for understanding the structural properties and phononic behaviors of this two-dimensional (2D) material. We quantitatively analyze the temperature dependent shifts of the Raman peak positions in the temperature range from 300 to 550 K, and find that both planar and out-of-plane characteristic modes are highly sensitive to temperature variations. This temperature dependency is linear and can be fully explained by the first-order temperature coefficient. Using a semi-quantitative model, we evaluate the contributions of the material's thermal expansion and intrinsic temperature effects to this dependency. We reveal that the dominating source of shift in the peak position of planar mode E2g(1) for samples of all thicknesses investigated is the four-phonon process. In addition to the four-phonon process, thermal expansion plays a significant role in the temperature dependency of the out-of-plane mode, A1g. The thickness dependency of the temperature coefficient for MoS2 and a drastic change in behaviors of samples from bi- to single-layered are also demonstrated. We further explore the role of defects in the thermal properties of MoS2 by examining the temperature dependency of Raman modes in CVD-grown samples.

Humidity effects on anisotropic nanofriction behaviors of aligned carbon nanotube carpets

We evaluated the interfacial properties of vertically and transversely aligned multiwalled carbon nanotubes (CNTs) carpets using atomic force microscopy (AFM) under ambient (26%-52% relative humidity (RH)), mild (10% RH), and dry conditions (<3.3% RH). The frictional forces on a transversely aligned CNT (TAMWCNT) surface are lower than those on a vertically aligned CNT (VAMWCNT) surface, and they decrease as the relative humidity decreases for both TAMWCNT and VAMWCNT surfaces. Similar trends are found for adhesion forces on both surfaces. Contact mechanics theories are applied and compared in an attempt to better understand these results. The tribological behavior of CNT carpets unveiled in this paper is expected to inspire tunable friction surface engineering strategies.

Microwave frequency performance and high magnetic anisotropy of nanocrystalline Fe70Co30-B films prepared by composition gradient sputtering

The fabrication and high-frequency ferromagnetic performances of nanocrystalline Fe70Co30-B soft magnetic films were investigated. It is revealed that the composition gradient sputtering method dramatically improves the high-frequency soft magnetic properties of the as-prepared films. This method gives rise to almost a linearly-increased distribution of compositions and residual stress. As a result, a very high ferromagnetic resonance frequency up to 6.7 GHz, high uniaxial magnetic anisotropic field up to 450 Oe, and low magnetic loss were obtained in as-deposited samples, which are particularly in favor of the integration between magnetic films and microwave components.

Tunable microwave frequency performance of nanocomposite Co2MnSi/PZN-PT magnetoelectric coupling structure

Nanocrystalline Co2MnSi Heusler alloy films were deposited on the PZN-PT substrates by a composition gradient sputtering method. It is revealed that this multiferroic heterostructure shows very strong magnetoelectric coupling, leading to continuously tunable microwave frequency characteristics by electric field. With the increase of electric field intensity from 0 to 6 kV/cm, the magnetic anisotropy field H(K) increases from 90 Oe to 182 Oe with an increment of 102%, corresponding to a ME coefficient of 15.3 Oe cm/kV; the ferromagnetic resonance frequency f(FMR) shifts from 3.38 to 4.82 GHz with an increment of deltaf(FMR) = 1440 MHz or deltaf(FMR)/f(FMR) = 43%; moreover, the damping constant alpha dramatically decreases from 0.035 to 0.018. These merits demonstrate that this nanocomposite multiferroic structure is promising in fabrication of tunable microwave components.

Neutralizing human monoclonal antibodies binding multiple serotypes of botulinum neurotoxin

Botulism, a disease of humans characterized by prolonged paralysis, is caused by botulinum neurotoxins (BoNTs), the most poisonous substances known. There are seven serotypes of BoNT (A-G) which differ from each other by 34-64% at the amino acid level. Each serotype is uniquely recognized by polyclonal antibodies, which originally were used to classify serotypes. To determine if there existed monoclonal antibodies (mAbs) capable of binding two or more serotypes, we evaluated the ability of 35 yeast-displayed single-chain variable fragment antibodies generated from vaccinated humans or mice for their ability to bind multiple BoNT serotypes. Two such clonally related human mAbs (1B18 and 4E17) were identified that bound BoNT serotype A (BoNT/A) and B or BoNT/A, B, E and F, respectively, with high affinity. Using molecular evolution techniques, it proved possible to both increase affinity and maintain cross-serotype reactivity for the 4E17 mAb. Both 1B18 and 4E17 bound to a relatively conserved epitope at the tip of the BoNT translocation domain. Immunoglobulin G constructed from affinity matured variants of 1B18 and 4E17 were evaluated for their ability to neutralize BoNT/B and E, respectively, in vivo. Both antibodies potently neutralized BoNT in vivo demonstrating that this epitope is functionally important in the intoxication pathway. Such cross-serotype binding and neutralizing mAbs should simplify the development of antibody-based BoNT diagnostics and therapeutics.

Glycogen Formation by the Ruminal Bacterium Prevotella ruminicola

Prevotella ruminicola is an important ruminal bacteria. In maltose-grown cells, nearly 60% of cell dry weight consisted of high-molecular-weight (>2 x 10(sup6)) glycogen. The ratio of glycogen to protein (grams per gram) was relatively low (1.3) during exponential growth, but when cell growth slowed during the transition to the stationary phase, the ratio increased to 1.8. As much as 40% of the maltose was converted to glycogen during cell growth. Glycogen accumulation in glucose-grown cells was threefold lower than that in maltose-grown cells. In continuous cultures provided with maltose, much less glycogen was synthesized at high (>0.2 per h) than at low dilution rates, where maltose was limiting (28 versus 60% of dry weight, respectively). These results indicated that glycogen synthesis was stimulated at low growth rates and was also influenced by the growth substrate. In permeabilized cells, glycogen was synthesized from [(sup14)C]glucose-1-phosphate but not radiolabelled glucose, indicating that glucose-1-phosphate is the initial precursor of glycogen formation. Glycogen accumulation may provide a survival mechanism for P. ruminicola during periods of carbon starvation and may have a role in controlling starch fermentation in the rumen.

Affinity maturation of human botulinum neurotoxin antibodies by light chain shuffling via yeast mating

Botulism is caused by the botulinum neurotoxins (BoNTs), the most poisonous substance known. Because of the high potency of BoNT, development of diagnostic and therapeutic antibodies for botulism requires antibodies of very high affinity. Here we report the use of yeast mating to affinity mature BoNT antibodies by light chain shuffling. A library of immunoglobulin light chains was generated in a yeast vector where the light chain is secreted. The heavy chain variable region and the first domain of the constant region (V(H)-C(H)1) from a monoclonal antibody was cloned into a different yeast vector for surface display as a fusion to the Aga2 protein. Through yeast mating of the two haploid yeasts, a library of light chain-shuffled Fab was created. Using this approach, the affinities of one BoNT/A and two BoNT/B scFv antibody fragments were increased from 9- to more than 77-fold. Subcloning the V-genes from the affinity-matured Fab yielded fully human IgG1 with equilibrium binding constants for BoNT/A and BoNT/B of 2.51 x 10(-11) M or lower for all three monoclonal antibodies. This technique provides a rapid route to antibody affinity maturation.

Paediatric PNET: pre-surgical MRI features

AIM

To describe the preoperative magnetic resonance imaging (MRI) characteristics of primitive neuroectodermal tumours (PNETs), in particular the diffusion-weighted imaging (DWI), MR spectroscopy (MRS) features and cerebrospinal fluid (CSF) tumour dissemination.

MATERIAL AND METHODS

Twelve patients with PNETs were reviewed: nine with medulloblastoma and three with supratentorial PNETs (SPNETs). The MRI examination included contrast-enhanced intracranial and spinal MRI, and in some patients, gradient recalled echo, fluid-attenuated inversion recovery (FLAIR), DWI, and MRS.

RESULTS

All PNETs were either hypointense or isointense on T1-weighted images. Ten of the 12 tumours were either isointense or hypointense on T2-weighted images, and 11 were isointense on FLAIR images. Patients with SPNETs had large, vascular and haemorrhagic tumours. On DWI, all PNETs were hyperintense and had restricted apparent diffusion coefficient. MRS (two patients with medulloblastoma and one with a SPNET), showed elevated choline, decreased N-acetyl aspartate, and a small taurine peak in all three patients. Intraspinal tumour dissemination, visible as uniform or nodular enhancement coating the conus medullaris, was detected in six of 12 patients, two of whom also had intracranial dissemination.

CONCLUSION

PNETs have a characteristic imaging appearance on FLAIR, DWI and MRS, which may help in differentiating these highly cellular neoplasms from other tumours. There is CSF tumour dissemination in a high proportion of patients, and spinal imaging is important for disease staging and to formulate treatment protocols.

High affinity promotes more effective ADCC by anti-HER2/neu monoclonal antibodies

2538

Background: Although monoclonal antibodies have emerged as useful cancer therapeutics, the antibody structural features and biologic properties that maximize therapeutic benefit are not fully understood. Antibody-dependent cellular cytotoxicity (ADCC) is believed to be a major mechanism of some anti-cancer antibodies. Herein, we describe the relationship between antibody affinity and the biologic properties of ADCC. Methods: A series of human IgG1 antibodies was created from the anti-HER2/neu C6.5 scFv and its affinity mutants (affinity ranging from 10−7 to 10−11 M). The IgGs were tested for their ability to elicit ADCC using a standard 51Cr-release assay. The ability of these IgGs to inhibit tumor cell proliferation and to induce apoptosis was evaluated using a colorimetric cell proliferation assay and homogeneous caspase assay/Annexin-V-FLUOS assay, respectively. Three tumor cell lines with differing levels of HER2/neu expression were used as target cells, and unactivated human PBMC from healthy donors were the effector cells. Results: There was a clear influence of both intrinsic and functional affinity on ADCC, with higher levels of peak cytotoxicity as apparent affinity approached 10−11 M. Among the antibodies with apparent affinity of 10−11 M, antibodies with higher intrinsic affinities elicited more ADCC. There also was an affinity-dependent increase in cytotoxicity at lower antibody concentrations and lower effector: target ratios. These antibodies elicited more cytotoxicity against tumor cells expressing high levels of HER2/neu than against cells expressing lower amounts of HER2/neu. None of these IgGs inhibited tumor cell proliferation, or induced apoptosis. Conclusions: Additional studies are needed to determine why, at the same functional avidity, ADCC is improved in antibodies with higher intrinsic affinities. These findings justify the examination of high affinity antibodies for ADCC promotion, although the impaired tumor targeting associated with high affinity may be an important confounding factor in the design of unconjugated anti-tumor antibodies. A careful examination of antibody structure: function relationships is required to develop optimized therapeutic unconjugated antibodies.

No significant financial relationships to disclose.