Avian influenza A(H5) virus circulation in live bird markets in Vietnam, 2017-2022

BACKGROUND

Highly pathogenic avian influenza A(H5) human infections are a global concern, with many A(H5) human cases detected in Vietnam, including a case in October 2022. Using avian influenza virus surveillance from March 2017-September 2022, we described the percent of pooled samples that were positive for avian influenza A, A(H5), A(H5N1), A(H5N6), and A(H5N8) viruses in live bird markets (LBMs) in Vietnam.

METHODS

Monthly at each LBM, 30 poultry oropharyngeal swab specimens and five environmental samples were collected. Samples were pooled in groups of five and tested for influenza A, A(H5), A(H5N1), A(H5N6), and A(H5N8) viruses by real-time reverse-transcription polymerase chain reaction. Trends in the percent of pooled samples that were positive for avian influenza were summarized by LBM characteristics and time and compared with the number of passively detected avian influenza outbreaks using Spearman's rank correlation.

RESULTS

A total of 25,774 pooled samples were collected through active surveillance at 167 LBMs in 24 provinces; 36.9% of pooled samples were positive for influenza A, 3.6% A(H5), 1.9% A(H5N1), 1.1% A(H5N6), and 0.2% A(H5N8). Influenza A(H5) viruses were identified January-December and at least once in 91.7% of sampled provinces. In 246 A(H5) outbreaks in poultry; 20.3% were influenza A(H5N1), 60.2% A(H5N6), and 19.5% A(H5N8); outbreaks did not correlate with active surveillance.

CONCLUSIONS

In Vietnam, influenza A(H5) viruses were detected by active surveillance in LBMs year-round and in most provinces sampled. In addition to outbreak reporting, active surveillance for A(H5) viruses in settings with high potential for animal-to-human spillover can provide situational awareness.

Observation of high-energy neutrinos from the Galactic plane

The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, is unknown. Because of deflection by interstellar magnetic fields, cosmic rays produced within the Milky Way arrive at Earth from random directions. However, cosmic rays interact with matter near their sources and during propagation, which produces high-energy neutrinos. We searched for neutrino emission using machine learning techniques applied to 10 years of data from the IceCube Neutrino Observatory. By comparing diffuse emission models to a background-only hypothesis, we identified neutrino emission from the Galactic plane at the 4.5σ level of significance. The signal is consistent with diffuse emission of neutrinos from the Milky Way but could also arise from a population of unresolved point sources.

Synthesis of (±)-Emtricitabine and (±)-Lamivudine by Chlorotrimethylsilane-Sodium Iodide-Promoted Vorbrüggen Glycosylation

By simple combination of water and sodium iodide (NaI) with chlorotrimethylsilane (TMSCl), promotion of a Vorbrüggen glycosylation en route to essential HIV drugs emtricitabine (FTC) and lamivudine (3TC) is achieved. TMSCl-NaI in wet solvent (0.1 M water) activates a 1,3-oxathiolanyl acetate donor for N-glycosylation of silylated cytosine derivatives, leading to cis-oxathiolane products with up to 95% yield and >20:1 dr. This telescoped sequence is followed by recrystallization and borohydride reduction, resulting in rapid synthesis of (±)-FTC/3TC from a tartrate diester.

Functional genomics approaches to improve pre-clinical drug screening and biomarker discovery

Advances in sequencing technology have enabled the genomic and transcriptomic characterization of human malignancies with unprecedented detail. However, this wealth of information has been slow to translate into clinically meaningful outcomes. Different models to study human cancers have been established and extensively characterized. Using these models, functional genomic screens and pre-clinical drug screening platforms have identified genetic dependencies that can be exploited with drug therapy. These genetic dependencies can also be used as biomarkers to predict response to treatment. For many cancers, the identification of such biomarkers remains elusive. In this review, we discuss the development and characterization of models used to study human cancers, RNA interference and CRISPR screens to identify genetic dependencies, large-scale pharmacogenomics studies and drug screening approaches to improve pre-clinical drug screening and biomarker discovery.

Aerosolisation during tracheal intubation and extubation in an operating theatre setting

Aerosol‐generating procedures such as tracheal intubation and extubation pose a potential risk to healthcare workers because of the possibility of airborne transmission of infection. Detailed characterisation of aerosol quantities, particle size and generating activities has been undertaken in a number of simulations but not in actual clinical practice. The aim of this study was to determine whether the processes of facemask ventilation, tracheal intubation and extubation generate aerosols in clinical practice, and to characterise any aerosols produced. In this observational study, patients scheduled to undergo elective endonasal pituitary surgery without symptoms of COVID‐19 were recruited. Airway management including tracheal intubation and extubation was performed in a standard positive pressure operating room with aerosols detected using laser‐based particle image velocimetry to detect larger particles, and spectrometry with continuous air sampling to detect smaller particles. A total of 482,960 data points were assessed for complete procedures in three patients. Facemask ventilation, tracheal tube insertion and cuff inflation generated small particles 30–300 times above background noise that remained suspended in airflows and spread from the patient’s facial region throughout the confines of the operating theatre. Safe clinical practice of these procedures should reflect these particle profiles. This adds to data that inform decisions regarding the appropriate precautions to take in a real‐world setting.

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100  eV^{2}. The best-fit point is found to be at sin^{2}(2θ_{24})=0.10 and Δm_{41}^{2}=4.5  eV^{2}, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.

Total Synthesis of (±)-Sceptrin

A four-step synthesis of the dimeric pyrrole-imidazole alkaloid sceptrin is reported. The brevity of the route is based on a simple solution developed for selective assembly of the cyclobutane core of the natural product. The photochemical intermolecular [2 + 2] dimerization of a useful hymenidin surrogate enables direct entry to this enigmatic class of biologically active marine secondary metabolites.

Central nervous system-specific efficacy of CDK4/6 inhibitors in randomized controlled trials for metastatic breast cancer

Importance: Metastatic breast cancer with central nervous system (CNS) metastases carries a poor prognosis. Recently, CDK4/6 inhibitors have demonstrated a progression free survival (PFS) and overall survival benefit when combined with standard endocrine therapy in advanced hormone receptor (HR)+/HER2- breast cancer. Pre-clinical data suggests possible activity of CDK4/6 inhibitors in the brain, but their CNS-specific benefit has not been explored in clinical practice. Methods: We reviewed clinical trials investigating the efficacy of CDK4/6 inhibitors for advanced or metastatic HR+/HER2- breast cancer. We also reviewed pre-clinical studies that demonstrated the ability of CDK4/6 inhibitors to cross the blood-brain barrier (BBB) and halt the growth of brain metastases in animal models. Findings: An ongoing phase II trial (NCT02308020) was designed to investigate the safety and tolerability of abemaciclib for treatment of patients with CNS metastases, with preliminary data showing partial response in some patients. Review of key randomized phase III trials revealed a scarcity of data pertaining to the development of new CNS metastases. Pre-clinical models demonstrate that CDK4/6 inhibitors are able to cross the BBB and can delay the growth of brain metastases. Conclusions: Despite encouraging pre-clinical evidence, there is a lack of clinical data to inform CNS-specific response rates to CDK4/6 inhibitors among patients with metastatic breast cancer. Given that the treatment of patients with breast cancer brain metastases represents an area of unmet medical need, enrollment of patients with CNS metastases in ongoing clinical trials should be encouraged; innovative trials that examine response of CNS metastases to CDK4/6 inhibitors are also of interest.

Progressive reduction of hospital length of stay following minimally invasive repair of pectus excavatum: A retrospective comparison of three analgesia modalities, the role of addressing patient anxiety, and reframing patient expectations

PURPOSE

Management of postoperative pain is a significant challenge following the Nuss procedure. Epidurals, PCAs, and newer analgesia modalities have been used elsewhere without demonstrating consistent improvement in the reported length of hospital stays (LOS). We reviewed a large single surgeon experience identifying three different methods of analgesia used over time to highlight marked improvement in patient LOS.

METHODS

IRB approval was obtained and patient clinical information was retrospectively reviewed from 2001 to 2017. The primary outcome variable was length of hospital stay. An expanded preoperative consultation reviews the issue of pain, the negative impact of anxiety on recovery, and our current success of shortened hospital stays with our patients.

RESULTS

One hundred and seventy-three patients representing three different analgesia approaches had a LOS of 4.4 days (epidural); 2.2 days (PCA/intercostal nerve block); and 1.6 days (scheduled oral pain meds/intercostal nerve blocks). The current LOS for patients is 1.0 day. Patients successfully stop using narcotics by the end of the first week postoperatively.

CONCLUSIONS

Intraoperative intercostal nerve blocks, scheduled postoperative pain medications, and enhanced preoperative consultation aimed to educate patients about anxiety and reframe patient pain expectations have collectively decreased LOS, and reduced postoperative narcotic usage.

TYPE OF STUDY

Clinical research LEVEL OF EVIDENCE: Level III.

Modeling the process of human tumorigenesis

Modelling the genesis of human cancers is at a scientific turning point. Starting from primary sources of normal human cells, it is now possible to reproducibly generate several types of malignant cell populations. Powerful methods for clonally tracking and manipulating their appearance and progression in serially transplanted immunodeficient mice are also in place. These developments circumvent historic drawbacks inherent in analyses of cancers produced in model organisms, established human malignant cell lines, or highly heterogeneous patient samples. In this review, we survey the advantages, contributions and limitations of current de novo human tumorigenesis strategies and note several exciting prospects on the horizon.

A better understanding of the earliest stages of human cancer formation can enable future improvements in early detection, diagnosis and treatment. In this review, the authors summarize the methods enabling de novo tumorigenesis protocols to be applied to human cells and the insights derived from them to date, as well as the exciting and relevant technical developments anticipated to extend even further the utility of these strategies.

Shifting Clade Distribution, Reassortment, and Emergence of New Subtypes of Highly Pathogenic Avian Influenza A(H5) Viruses Collected from Vietnamese Poultry from 2012 to 2015

Whole-genome sequences of representative highly pathogenic avian influenza A(H5) viruses from Vietnam were generated, comprising samples from poultry outbreaks and active market surveillance collected from January 2012 to August 2015. Six hemagglutinin gene clades were characterized. Clade 1.1.2 was predominant in southern Mekong provinces throughout 2012 and 2013 but gradually disappeared and was not detected after April 2014. Clade 2.3.2.1c viruses spread rapidly during 2012 and were detected in the south and center of the country. A number of clade 1.1.2 and 2.3.2.1c interclade reassortant viruses were detected with different combinations of internal genes derived from 2.3.2.1a and 2.3.2.1b viruses, indicating extensive cocirculation. Although reassortment generated genetic diversity at the genotype level, there was relatively little genetic drift within the individual gene segments, suggesting genetic stasis over recent years. Antigenically, clade 1.1.2, 2.3.2.1a, 2.3.2.1b, and 2.3.2.1c viruses remained related to earlier viruses and WHO-recommended prepandemic vaccine strains representing these clades. Clade 7.2 viruses, although detected in only low numbers, were the exception, as indicated by introduction of a genetically and antigenically diverse strain in 2013. Clade 2.3.4.4 viruses (H5N1 and H5N6) were likely introduced in April 2014 and appeared to gain dominance across northern and central regions. Antigenic analyses of clade 2.3.4.4 viruses compared to existing clade 2.3.4 candidate vaccine viruses (CVV) indicated the need for an updated vaccine virus. A/Sichuan/26221/2014 (H5N6) virus was developed, and ferret antisera generated against this virus were demonstrated to inhibit some but not all clade 2.3.4.4 viruses, suggesting consideration of alternative clade 2.3.4.4 CVVs.IMPORTANCE Highly pathogenic avian influenza (HPAI) A(H5) viruses have circulated continuously in Vietnam since 2003, resulting in hundreds of poultry outbreaks and sporadic human infections. Despite a significant reduction in the number of human infections in recent years, poultry outbreaks continue to occur and the virus continues to diversify. Vaccination of poultry has been used as a means to control the spread and impact of the virus, but due to the diversity and changing distribution of antigenically distinct viruses, the utility of vaccines in the face of mismatched circulating strains remains questionable. This study assessed the putative amino acid changes in viruses leading to antigenic variability, underscoring the complexity of vaccine selection for both veterinary and public health purposes. Given the overlapping geographic distributions of multiple, antigenically distinct clades of HPAI A(H5) viruses in Vietnam, the vaccine efficacy of bivalent poultry vaccine formulations should be tested in the future.

A cross-sectional study to quantify the prevalence of avian influenza viruses in poultry at intervention and non-intervention live bird markets in central Vietnam, 2014

In Vietnam, live bird markets are found in most populated centres, providing the means by which fresh poultry can be purchased by consumers for immediate consumption. Live bird markets are aggregation points for large numbers of poultry, and therefore, it is common for a range of avian influenza viruses to be mixed within live bird markets as a result of different poultry types and species being brought together from different geographical locations. We conducted a cross-sectional study in seven live bird markets in four districts of Thua Thien Hue Province in August and December, 2014. The aims of this study were to (i) document the prevalence of avian influenza in live bird markets (as measured by virus isolation); and (ii) quantify individual bird-, seller- and market-level characteristics that rendered poultry more likely to be positive for avian influenza virus at the time of sale. A questionnaire soliciting details of knowledge, attitude and avian influenza practices was administered to poultry sellers in study markets. At the same time, swabs and faecal samples were collected from individual poultry and submitted for isolation of avian influenza virus. The final data set comprised samples from 1,629 birds from 83 sellers in the seven live bird markets. A total of 113 birds were positive for virus isolation; a prevalence of 6.9 (95% CI 5.8-8.3) avian influenza virus-positive birds per 100 birds submitted for sale. After adjusting for clustering at the market and individual seller levels, none of the explanatory variables solicited in the questionnaire were significantly associated with avian influenza virus isolation positivity. The proportions of variance at the individual market, seller and individual bird levels were 6%, 48% and 46%, respectively. We conclude that the emphasis of avian influenza control efforts in Vietnam should be at the individual seller level as opposed to the market level.

Abstract A63: Clonal analysis of normal and malignant human mammary epithelial cell responsiveness to radiation

Knowledge gap: Fatal breast cancers are characterized by biological, genomic and extensive treatment heterogeneity. Although many breast cancers can now be cured by established therapies, treatment failure remains a major problem and is difficult to predict. In the current era of “personalized medicine”, a possible solution is to develop a large-scale system for quantifying responses to candidate treatments of individual malignant human mammary cells with in vivo clonogenic activity. Such cells can be detected by their ability to produce uniquely barcoded clones of progeny in xenografted immunodeficient mice and the clones obtained can be assessed for their size and number using next generation sequencing of tumor extracts. However, to pursue this approach it is first critical to establish how the clone content of a tumor may vary according to the number or type of competent tumorigenic and/or other cells that are present in the inoculum used to initiate tumor formation, and hence whether and how these parameters may influence assessment of the treatment responsiveness of these cells.

Approach/methods: Here we describe the development and initial testing of a method to measure the treatment responsiveness of large numbers of tumorigenic cells using radiation as a prototypic treatment. Treatment sensitivity of in vitro colony-forming cells (CFCs) will then be compared with future measurements of in vivo clone-initiating tumorigenic cells obtained by sequencing the progeny of DNA-barcoded input cells.

Results: In an initial series of experiments we showed that normal human luminal progenitor (LP) CFCs are ~1.5-fold more radioresistant than basal cell (BC) CFCs, and both are more sensitive than either type of mouse mammary CFCs. In vitro CFC assays of 2 human breast cancer cell lines (MDA MB231 and SUM149, with in vitro CFC frequencies of 70% and 40%, respectively) showed these to be 1.2- and 1.5-fold more radioresistant than normal LPs. Limiting dilution analysis showed the corresponding frequency of in vivo tumor-initiating cells in these 2 cell lines to be 1/6 and 1/47. Assessment of their response to radiation is complicated by the finding that the barcoded clone content of tumors initiated with >20,000 of these cells (untreated) is inversely related to the number injected and, at these input cell doses, very heterogeneous clone dynamics are also seen in successive passages. However, evidence of a positive linear cell dose-clone yield relationship is seen at input transplants of <1,000 cells from these 2 lines and this relationship would be predicted to extend to initial transplants of <2-5,000 cells. Recently we have found that normal human mammary LPs and BCs transduced with KRASG12D generate tumors efficiently in immunodeficient mice. Thus a next step is to determine if and how the radiosensitivity of the tumorigenic cells changes during the transformation process.

Conclusion: These results highlight the complex clonal dynamics already operative in the growth of tumorigenic cells present in relatively homogeneous established human mammary cell lines and set the stage for future measurements of clone yields from irradiated cells derived from mammary tumors of different origins.

Citation Format: Sneha Balani, Nagarajan Kannan, Long V. Nguyen, Sylvain Lefort, Davide Pellacani, Connie J. Eaves. Clonal analysis of normal and malignant human mammary epithelial cell responsiveness to radiation. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A63.

DNA barcoding reveals diverse growth kinetics of human breast tumour subclones in serially passaged xenografts

Genomic and phenotypic analyses indicate extensive intra- as well as intertumoral heterogeneity in primary human malignant cell populations despite their clonal origin. Cellular DNA barcoding offers a powerful and unbiased alternative to track the number and size of multiple subclones within a single human tumour xenograft and their response to continued in vivo passaging. Using this approach we find clone-initiating cell frequencies that vary from ~1/10 to ~1/10,000 cells transplanted for two human breast cancer cell lines and breast cancer xenografts derived from three different patients. For the cell lines, these frequencies are negatively affected in transplants of more than 20,000 cells. Serial transplants reveal five clonal growth patterns (unchanging, expanding, diminishing, fluctuating or of delayed onset), whose predominance is highly variable both between and within original samples. This study thus demonstrates the high growth potential and diverse growth properties of xenografted human breast cancer cells.

Cancer cells within the same tumour are heterogeneous in their tumorigenic potential, differentiation status and sensitivity to treatments. Here Nguyen et al. use a sensitive DNA barcoding method to characterize the diversity of clonal growth behaviour within human breast tumours.

Two-year outcome of first-line antiretroviral therapy among HIV-1 vertically-infected children in Hanoi, Vietnam

A retrospective analysis of 86 HIV-1 vertically-infected Vietnamese children with a follow-up period >24 months after initiating antiretroviral therapy (ART) was performed from 2008 to 2012, to assess the outcome of first-line ART in resource-limited settings. Of the 86 children, 68 (79.1%) were treated successfully (plasma HIV-1 viral load [VL] <1000 copies/ml), and 63 (73.3%) had full viral suppression (VL <400 copies/ml) after 24 months of ART. No significant difference between successfully treated patients and failure groups was observed in VL, CD4(+) T-cell count or clinical stage at baseline; age at ART start; or ART regimen. All 14 children with VL >5000 copies/ml, one of four children with VL 1000-5000 copies/ml and none with VL <1000 copies/ml developed reverse transcriptase inhibitor (RTI)-resistance mutations by 24 months of ART. Y181C and M184V/I were the most dominant non-nucleoside and nucleoside RTI-resistance mutations, respectively (13/15, 86.7%). These findings suggest that VL testing after 24 months of ART can be used to efficiently differentiate ART failures among HIV-1 vertically-infected children in resource-limited settings.

Optimized inhibitors of soluble epoxide hydrolase improve in vitro target residence time and in vivo efficacy

Diabetes is affecting the life of millions of people. A large proportion of diabetic patients suffer from severe complications such as neuropathic pain, and current treatments for these complications have deleterious side effects. Thus, alternate therapeutic strategies are needed. Recently, the elevation of epoxy-fatty acids through inhibition of soluble epoxide hydrolase (sEH) was shown to reduce diabetic neuropathic pain in rodents. In this report, we describe a series of newly synthesized sEH inhibitors with at least 5-fold higher potency and doubled residence time inside both the human and rodent sEH enzyme than previously reported inhibitors. These inhibitors also have better physical properties and optimized pharmacokinetic profiles. The optimized inhibitor selected from this new series displayed improved efficacy of almost 10-fold in relieving pain perception in diabetic neuropathic rats as compared to the approved drug, gabapentin, and previously published sEH inhibitors. Therefore, these new sEH inhibitors could be an attractive alternative to treat diabetic neuropathy in humans.

Integrin β3 links therapy resistance and cancer stem cell properties

Heterogeneity in tumour cell properties underlies many treatment failures. Understanding the sources of such heterogeneity has proved to be challenging, but remains critical to improving patient outcomes. Integrin α(v)β₃ expression in multiple types of solid tumour stem cells is now shown to control a pro-survival pathway that contributes to therapy resistance.

Developmental changes in the in vitro activated regenerative activity of primitive mammary epithelial cells

Mouse fetal mammary cells display greater regenerative activity than do adult mammary cells when stimulated to proliferate in a new system that supports the production of transplantable mammary stem cells ex vivo.

Many normal adult tissues contain rare stem cells with extensive self-maintaining regenerative potential. During development, the stem cells of the hematopoietic and neural systems undergo intrinsically specified changes in their self-renewal potential. In the mouse, mammary stem cells with transplantable regenerative activity are first detectable a few days before birth. They share some phenotypic properties with their adult counterparts but are enriched in a subpopulation that displays a distinct gene expression profile. Here we show that fetal mammary epithelial cells have a greater direct and inducible growth potential than their adult counterparts. The latter feature is revealed in a novel culture system that enables large numbers of in vitro clonogenic progenitors as well as mammary stem cells with serially transplantable activity to be produced within 7 days from single fetal or adult input cells. We further show that these responses are highly dependent on novel factors produced by fibroblasts. These findings provide new avenues for elucidating mechanisms that regulate normal mammary epithelial stem cell properties at the single-cell level, how these change during development, and how their perturbation may contribute to transformation.

Many adult tissues are maintained by a rare subset of undifferentiated stem cells that can self-renew and give rise to specialized daughter cells that have a more limited regenerative ability. The recent identification of cells in the fetal and adult mammary gland that display the properties of stem cells provides a foundation for investigating their self-renewal and differentiation control. We now show that these stem cell properties can be elicited from single mouse mammary cells placed in 3D cultures if novel factors produced by fibroblasts are present. Moreover, a comparison of the clonal outputs of fetal and adult mammary cells in this in vitro system shows that the fetal mammary cells have superior regenerative activity relative to their adult counterparts. The ability to activate and quantify the regenerative capacity of single mouse mammary epithelial cells in vitro sets the stage for further investigations of the timing and mechanisms that alter their stem cell properties during development, the potential relevance of these events to other normal epithelial tissues, and how these processes might be involved in the genesis of breast cancer.

Synthesis and biological evaluation of sorafenib- and regorafenib-like sEH inhibitors

To reduce the pro-angiogenic effects of sEH inhibition, a structure-activity relationship (SAR) study was performed by incorporating structural features of the anti-angiogenic multi-kinase inhibitor sorafenib into soluble epoxide hydrolase (sEH) inhibitors. The structural modifications of this series of molecules enabled the altering of selectivity towards the pro-angiogenic kinases C-RAF and vascular endothelial growth factor receptor-2 (VEGFR-2), while retaining their sEH inhibition. As a result, sEH inhibitors with greater potency against C-RAF and VEGFR-2 were obtained. Compound 4 (t-CUPM) possesses inhibition potency higher than sorafenib towards sEH but similar against C-RAF and VEGFR-2. Compound 7 (t-CUCB) selectively inhibits sEH, while inhibiting HUVEC cell proliferation, a potential anti-angiogenic property, without liver cancer cell cytotoxicity. The data presented suggest a potential rational approach to control the angiogenic responses stemming from sEH inhibition.

Descriptive results of a prospective cohort study of avian influenza in the Mekong River Delta of Viet Nam

A prospective cohort study of avian influenza infection in poultry flocks was carried out in the Mekong River Delta of Viet Nam between December 2008 and April 2010. Our objectives were to (i) estimate the prevalence and incidence of avian influenza virus infection and (ii) assess the efficacy of H5N1 vaccination programmes as indicated by the presence of H5 antibody in vaccinated and unvaccinated poultry. Real-time PCR and H5 multiplex assays were used to detect the antigen of avian influenza viruses from swab samples. The haemagglutination inhibition test was used to detect H5 antibody. A total of 17 968 swab and 14 878 blood samples were collected from 5476 birds over the study period. The overall incidence rate of influenza type A virus infection was 5 (95% CI 4-7) positive birds per 100 bird-months at risk. The overall incidence rate of H5 virus infection was 0.2 (95% CI 0.1-0.5) positive birds per 100 bird-months at risk. Fifty (95% CI 48-52) birds per 100 tested birds were H5 HI positive in the unvaccinated group compared with 71 (95% CI 69-73) birds per 100 in the vaccinated group. Influenza type A and H5 viruses were circulating in village poultry throughout the study period with no recorded signs of clinical disease. This implies that interventions need to be carried out continuously throughout the year rather than only focusing on the established high-risk periods. Broiler ducks had an incidence rate of influenza H5 virus infection approximately four times greater than that of layer ducks and in-contact species. We conclude that broiler ducks are likely to be the main entry route for H5 virus into poultry flocks in the MRD. Control efforts would benefit from understanding why there is a difference between villages in H5 incidence and developing strategies to provide greater protection to broiler ducks.

Genetic engineering of a Lemna isoleucine auxotroph

Lemna, a member of the Lemnaceae or duckweed family, is a small aquatic plant that can be quickly transformed to produce recombinant proteins in a contained and controlled bioprocessing environment. The containment capability of Lemna has been further improved with the creation of an auxotroph platform that requires isoleucine supplementation for survival of transformed plant lines. Using an RNAi based approach, threonine deaminase (TD) expression was targeted and thus resulted in dramatically reduced expression of this key enzyme in the isoleucine biosynthesis pathway. Auxotrophic plants expressing RNAi for TD were generated in the presence of isoleucine and selected based on their inability to propagate without isoleucine supplementation. TD transcripts isolated from the superior auxotroph lines were shown to be less than 10% of wild type level and thus confirmed the auxotroph phenotype to be derived from the specific knock down of TD expression. When grown under optimal conditions with appropriate isoleucine supplementation, biomass accumulation of the auxotroph lines was equivalent to that of wild type plants. To demonstrate the application of this system for production of recombinant proteins, an avian influenza H5N1 hemagglutinin (HA) protein was expressed in the isoleucine auxotroph platform. The successful expression of H5N1 HA vaccine antigen, in the isoleucine auxotroph background demonstrates the applicability of using an auxotroph to express biotherapeutics and vaccines in a highly contained expression system.

Cancer stem cells: an evolving concept

The cancer stem cell (CSC) concept derives from the fact that cancers are dysregulated tissue clones whose continued propagation is vested in a biologically distinct subset of cells that are typically rare. This idea is not new, but has recently gained prominence because of advances in defining normal tissue hierarchies, a greater appreciation of the multistep nature of oncogenesis and improved methods to propagate primary human cancers in immunodeficient mice. As a result we have obtained new insights into why the CSC concept is not universally applicable, as well as a new basis for understanding the complex evolution, phenotypic heterogeneity and therapeutic challenges of many human cancers.

Nuclear replacement of in vitro-matured porcine oocytes by a serial centrifugation and fusion method

The objective of the present study was to establish a method for nuclear replacement in metaphase-II (M-II) stage porcine oocytes. Karyoplasts containing M-II chromosomes (K) and cytoplasts without chromosomes (C) were produced from in vitro-matured oocytes by a serial centrifugation method. The oocytes were then reconstructed by fusion of one karyoplast with 1, 2, 3 or 4 cytoplasts (K + 1C, K + 2C, K + 3C and K + 4C, respectively). Reconstructed oocytes, karyoplasts without fusion of any cytoplast (K) and zona-free M-II oocytes (control) were used for experiments. The rates of female pronucleus formation after parthenogenetic activation in all groups of reconstructed oocytes (58.2-77.4%) were not different from those of the K and control groups (58.2% and 66.0%, respectively). In vitro fertilization was carried out to assay the fertilization ability and subsequent embryonic development of the reconstructed oocytes. The cytoplast : karyoplast ratio did not affect the fertilization status (penetration and male pronuclear formation rates) of the oocytes. A significantly high monospermy rate was found in K oocytes (p < 0.05, 61.6%) compared with the other groups (18.2-32.8%). Blastocyst formation rates increased significantly as the number of the cytoplasts fused with karyoplasts increased (p < 0.05, 0.0-15.3%). The blastocyst rate in the K + 4C group (15.3%) was comparable with that of the control (17.8%). Total cell numbers in both the K + 3C and K + 4C groups (16.0 and 15.3 cells, respectively) were comparable with that of the control (26.2 cells). Our results demonstrate that a serial centrifugation and fusion (Centri-Fusion) is an effective method for producing M-II chromosome transferred oocytes with normal fertilization ability and in vitro development. It is suggested that the number of cytoplasts fused with a karyoplast plays a critical role in embryonic development.

TMV-peptide fusion vaccines induce cell-mediated immune responses and tumor protection in two murine models

Fusion of peptides to viral carriers has proven an effective method for improving cellular immunity. In this study we explore the ability of a plant virus, Tobacco mosaic virus (TMV), to stimulate cellular immunity by interacting directly with immune cells. Fluorescently labeled TMV was incubated in vitro with murine spleen or lymph node cells, and near quantitative labeling of lymphocytes was achieved after 2 h, which persisted for up to 48 h. Direct TMV uptake and upregulation of the CD86 activation marker was measured in nearly all dendritic cells (DCs) by flow cytometry. To demonstrate that TMV can also provide functional antigen delivery and immune stimulation in vivo, two well-characterized T-cell epitopes that provide protection against tumor challenge in mice were fused to TMV coat protein by genetic manipulation, or by chemical conjugation. Vaccination of C57BL/6 mice elicited measurable cellular responses by interferon gamma (IFN gamma) ELISpot and resulted in significantly improved protection from tumor challenge in both the EG.7-Ova and B16 melanoma models. From these results we conclude that TMV was an effective antigen carrier for inducing cellular immune responses to less than 1 microg of peptide.

Modified tobacco mosaic virus particles as scaffolds for display of protein antigens for vaccine applications

Display of peptides or proteins in an ordered, repetitive array, such as on the surface of a virus-like particle, is known to induce an enhanced immune response relative to vaccination with the "free" protein antigen. The coat protein of Tobacco mosaic virus (TMV) can accommodate short peptide insertions into the primary sequence, but the display of larger protein moieties as genetic fusions to the capsid protein has not been possible. We employed a randomized library approach to introduce a reactive lysine at the externally located amino terminus of the coat protein, which facilitated biotinylation of the capsid. To characterize display of heterologous proteins on the virion surface, we bound a model antigen (green fluorescent protein (GFP)-streptavidin (SA), expressed and purified from plants) to the biotinylated TMV particles, creating a GFP-SA decorated virus particle. A GFP-SA tetramer loading of 26% was obtained, corresponding to approximately 2200 GFP moieties displayed per intact virion. We evaluated the immunogenicity of GFP decorated virions in both mice and guinea pigs and found augmented humoral IgG titers in both species, relative to unbound GFP-SA tetramer. Next, we fused an N-terminal fragment of the Canine oral papillomavirus L2 protein to streptavidin. With TMV display, the L2 protein fragment was significantly more immunogenic than uncoupled antigen when tested in mice. By demonstrating the presentation of whole proteins, this study expands the utility of TMV as a vaccine scaffold beyond that which is possible by genetic manipulation.

Development of a plant viral-vector-based gene expression assay for the screening of yeast cytochrome p450 monooxygenases

Development of a gene discovery tool for heterologously expressed cytochrome P450 monooxygenases has been inherently difficult. The activity assays are labor-intensive and not amenable to parallel screening. Additionally, biochemical confirmation requires coexpression of a homologous P450 reductase or complementary heterologous activity. Plant virus gene expression systems have been utilized for a diverse group of organisms. In this study we describe a method using an RNA vector expression system to phenotypically screen for cytochrome P450-dependent fatty acid omega-hydroxylase activity. Yarrowia lipolytica CYP52 gene family members involved in n-alkane assimilation were amplified from genomic DNA, cloned into a plant virus gene expression vector, and used as a model system for determining heterologous expression. Plants infected with virus vectors expressing the yeast CYP52 genes (YlALK1-YlALK7) showed a distinct necrotic lesion phenotype on inoculated plant leaves. No phenotype was detected on negative control constructs. YlALK3-, YlALK5-, and YlALK7-inoculated plants all catalyzed the terminal hydroxylation of lauric acid as confirmed using thin-layer and gas chromatography/mass spectrometry methods. The plant-based cytochrome P450 phenotypic screen was tested on an n-alkane-induced Yarrowia lipolytica plant virus expression library. A subset of 1,025 random library clones, including YlALK1-YlALK7 constructs, were tested on plants. All YlALK gene constructs scored positive in the randomized screen. Following nucleotide sequencing of the clones that scored positive using a phenotypic screen, approximately 5% were deemed appropriate for further biochemical analysis. This report illustrates the utility of a plant-based system for expression of heterologous cytochrome P450 monooxygenases and for the assignment of gene function.

Immunomodulation of experimental autoimmune encephalomyelitis with ordered peptides based on MHC-TCR binding motifs

T cell-mediated destruction of the myelin sheath causes inflammatory damage of the CNS in multiple sclerosis (MS). The major T and B cell responses in MS patients who are HLA-DR2 (about two-thirds of MS patients) react to a region between residues 84 and 103 of myelin basic protein (1 ). The crystal structure of HLA-DR2 complexed with myelin basic protein(84-102) confirmed that Lys(91) is the major TCR contact site, whereas Phe(90) is a major anchor to MHC and binds the hydrophobic P4 pocket (2 ). We have tested peptides containing repetitive 4-aa sequences designed to bind critical MHC pockets and to interfere with T cell activation. One such sequence, EYYKEYYKEYYK, ameliorates experimental autoimmune encephalomyelitis in Lewis rats, an animal model of MS.

Transposon tagging of the sulfur gene of tobacco using engineered maize Ac/Ds elements

The Sulfur gene of tobacco is nuclearly encoded. A Su allele at this locus acts as a dominant semilethal mutation and causes reduced accumulation of chlorophyll, resulting in a yellow color in the plant. An engineered transposon tagging system, based upon the maize element Ac/Ds, was used to mutate the gene. High frequency of transposon excision from the Su locus produced variegated sectors. Plants regenerated from the variegated sector exhibited a similar variegated phenotype. Genetic analyses showed that the variegation was always associated with the transposase construct and the transposon was linked to the Su locus. Sequences surrounding the transposon were isolated, and five revertant sectors possessed typical direct repeats following Ds excisions. These genetic and molecular data are consistent with the tagging of the Su allele by the transposon.

The Pex16p homolog SSE1 and storage organelle formation in Arabidopsis seeds

Mature Arabidopsis seeds are enriched in storage proteins and lipids, but lack starch. In the shrunken seed 1 (sse1) mutant, however, starch is favored over proteins and lipids as the major storage compound. SSE1 has 26 percent identity with Pex16p in Yarrowia lipolytica and complements pex16 mutants defective in the formation of peroxisomes and the transportation of plasma membrane- and cell wall-associated proteins. In Arabidopsis maturing seeds, SSE1 is required for protein and oil body biogenesis, both of which are endoplasmic reticulum-dependent. Starch accumulation in sse1 suggests that starch formation is a default storage deposition pathway.

Suppressive immunization with DNA encoding a self-peptide prevents autoimmune disease: modulation of T cell costimulation

Usually we rely on vaccination to promote an immune response to a pathogenic microbe. In this study, we demonstrate a suppressive from of vaccination, with DNA encoding a minigene for residues 139-151 of myelin proteolipid protein (PLP139-151), a pathogenic self-Ag. This suppressive vaccination attenuates a prototypic autoimmune disease, experimental autoimmune encephalomyelitis, which presents clinically with paralysis. Proliferative responses and production of the Th1 cytokines, IL-2 and IFN-gamma, were reduced in T cells responsive to PLP139-151. In the brains of mice that were successfully vaccinated, mRNA for IL-2, IL-15, and IFN-gamma were reduced. A mechanism underlying the reduction in severity and incidence of paralytic autoimmune disease and the reduction in Th1 cytokines involves altered costimulation of T cells; loading of APCs with DNA encoding PLP139-151 reduced the capacity of a T cell line reactive to PLP139-151 to proliferate even in the presence of exogenous CD28 costimulation. DNA immunization with the myelin minigene for PLP-altered expression of B7.1 (CD80), and B7.2 (CD86) on APCs in the spleen. Suppressive immunization against self-Ags encoded by DNA may be exploited to treat autoimmune diseases.

Gene silencing from plant DNA carried by a Geminivirus

The geminivirus tomato golden mosaic virus (TGMV) replicates in nuclei and expresses genes from high copy number DNA episomes. The authors used TGMV as a vector to determine whether episomal DNA can cause silencing of homologous, chromosomal genes. Two markers were used to asses silencing: (1) the sulfur allele (su) of magnesium chelatase, an enzyme required for chlorophyll formation; and (2) the firefly luciferase gene (luc). Various portions of both marker genes were inserted into TGMV in place of the coat protein open-reading frame and the constructs were introduced into intact plants using particle bombardment. When TGMV vectors carrying fragments of su (TGMV::su) were introduced into leaves of wild type Nicotiana benthamiana, circular, yellow spots with an area of several hundred cells formed after 3-5 days. Systemic movement of TGMV::su subsequently produced varigated leaf and stem tissue. Fragments that caused silencing included a 786 bp 5' fragment of the 1392 bp su cDNA in sense and anti-sense orientation, and a 403 bp 3' fragment. TGMV::su-induced silencing was propogated through tissue culture, along with the viral episome, but was not retained through meiosis. Systemic downregulation of a constitutively expresse luciferase transgene in plants was achieved following infection with TGMV vectors carrying a 623 bp portion of luc in sense or anti-sense orientation. These results establish that homologous DNA sequences localized in nuclear episomes can modulate the expression of active chromosomal genes.

Development and characterization of a generalized gene tagging system for higher plants using an engineered maize transposon Ac

This report describes a series of transposon tagging vectors for dicotyledonous plants based on the maize transposable element Ac. This binary system includes the transposase (Ts) and the tagging element (Ds) on separate T-DNA vectors. Ts elements include versions in which transcription is driven either by the endogenous Ac promoter or by the cauliflower mosaic virus (CaMV) 35S promoter. Ds tagging element includes a gene conferring methotrexate (Mtx) resistance for selection and a supF gene to facilitate cloning of tagged sequences. The Ds element is flanked by a CaMV 35S promoter and the beta-glucuronidase (GUS) coding sequence so that GUS expression occurs upon excision of the element. We have transformed these Ts and Ds elements into tobacco and demonstrated that the Ts is functional with either promoter, and that the artificial Ds elements are capable of transposition. The amount of excision was found to depend upon both the individual Ts and Ds primary transformants used. Somatic excision of Ds was seen in up to 100% of progeny seedlings containing Ts and Ds. Germinal excision was detected in up to 48% of the progeny of plants containing both elements. Hence, this system can generate a sufficient number of events to be useful in gene tagging.