Biomedical subjects

Christine L Moe

Publications and source records attributed to Christine L Moe.

13 recordsLinked to original sources

PubMed2025

Variation in Severity of Symptoms Associated With Two Snow Mountain Virus Inocula.

Snow Mountain Virus (SMV), the prototype of genogroup II and genotype II Norovirus (NoV), was used in human challenge studies to examine the infectivity, pathogenicity, and immune response to NoV. Clinical and laboratory data from two previously completed SMV human challenge trials using two different inocula (primary and secondary) were analyzed to compare the infectivity, illness, viral shedding, and serum IgG conversion. The primary and secondary SMV inocula were sequenced for detecting single nucleotide mutations. Of 15 subjects challenged with the primary inoculum between 2000 and 2002, nine were infected, and seven presented with acute gastroenteritis. Of 33 subjects challenged with the secondary inoculum between 2016 and 2018, 25 were infected, and nine presented with acute gastroenteritis. There were no statistically significant differences in overall infection and illness rates between subjects challenged with the primary inoculum versus the secondary inoculum. However, subjects infected with the primary inoculum experienced more severe clinical symptoms of acute gastroenteritis, showing higher severity scores (6.00 vs. 2.94, p = 0.003) compared with those infected with the secondary inoculum. We also observed that infection with the secondary inoculum resulted in longer viral shedding compared with the primary inoculum. Partial sequencing of the SMV genome identified three mutations in both inocula. Understanding the differences between these two SMV inocula is critical for NoV vaccine evaluation and using a less pathogenic inoculum for a vaccine trial will require more participants to meet the target reduction in illness when evaluating the efficacy of candidate vaccines.

Humans↗

PubMed2006

A field study of the microbiological quality of fresh produce of domestic and Mexican origin.

Produce is responsible for an increasingly larger proportion of foodborne disease outbreaks. In particular, the globalization of the food supply may introduce new food safety risks and allow widespread distribution of contaminated food, particularly produce. The objectives of this study were to: (i) compare the overall quality of domestic and Mexican produce throughout the packing process; (ii) examine changes in microbiological quality of both domestic and Mexican produce at each stage of production and processing; and (iii) evaluate the prevalence of select pathogens on fresh produce, including leafy green, herbs, melons, and vegetables. Furthermore, we also sought to characterize the antibiotic resistance profiles of Enterococcus faecium and Enterococcus faecalis strains isolated from fresh produce. A total of 466 produce and matching environmental swab samples was collected from various locations in packing sheds in the southern US from November 2002 through December 2003. These samples were assayed by enumerative tests for total aerobic bacteria (APC), total coliforms, total Enterococcus, and E. coli. Produce samples were also analyzed for the presence of Salmonella, Listeria monocytogenes, Shigella, and E. coli O157:H7. A total of 112 E. faecium and E. faecalis isolates were further screened for antibiotic resistance using a panel of seventeen antibiotics. Overall, the microbiological quality of fresh produce ranged from 4.0 to 7.9 log(10) CFU/g (APC); less than 1.0 log(10) to 4.5 log(10) CFU/g (coliforms); less than 1.0 log(10) to 4.0 log(10) CFU/g (E. coli); and less than 1.0 log(10) to 5.4 log(10) CFU/g (Enterococcus). No Salmonella, Shigella, or E. coli O157:H7 were detected from the 466 25-g produce samples tested. However, three domestic cabbage samples were found to be positive for L. monocytogenes. Of the Enterococcus isolates, E. faecium had a higher degree of resistance to antibiotics in general, while Enterococcus spp. isolated from Mexican produce had a higher degree of antibiotic resistance when compared to strains isolated from produce samples of domestic origin. Despite increased attention to the role of imported produce in foodborne disease, this study does not support the assumption that domestic produce is of higher microbial quality than Mexican produce.

Anti-Bacterial Agents↗

PubMed2006

Multivalent norovirus vaccines induce strong mucosal and systemic blocking antibodies against multiple strains.

Noroviruses are important agents of human gastroenteritis characterized by extensive sequence variation in the major capsid structural protein that likely encodes critical antigenic determinants of protective immunity. The lack of an infection model has limited detailed characterizations of viral antigenic relationships and identification of the essential components for protective immunity. This information would contribute to efficacious vaccine design against a broad array of norovirus strains. To understand the extent of heterotypic norovirus antibody specificity to inter- and intra-genogroup strains and its applicability to vaccine design, we collected sera from humans infected with different norovirus strains and from mice inoculated with alphavirus vectors expressing strain-specific recombinant norovirus-like particles (VLPs). We used VLPs that were assembled from Norwalk virus (NV), Hawaii virus (HV), Snow Mountain virus (SM) and Lordsdale virus (LV) as antigens to define and compare heterotypic antibody responses in humans and mice. We also examined if these heterotypic antibodies could block specific binding of ABH histo-blood group antigens, putative receptors for norovirus binding and entry, to norovirus VLPs. Furthermore, we examined the effect of multivalent inocula on the specificity, titer, and ligand blockade properties of systemic and mucosal norovirus-specific antibodies in mice. Our studies suggest that infection with one of several different genogroup I (GI) strains in humans induces heterotypic antibodies that block NV binding to ABH antigens, although comparable findings were not evident following infection with genogroup (GII) strains. Additionally, inoculating mice with vaccine cocktails encoding multiple norovirus VLPs enhances heterotypic and ligand attachment-blocking antibody responses against the LV strain not included in the cocktail. These data suggest that multivalent vaccination may provide better protection from a broader range of noroviruses than monovalent vaccination.

Amino Acid Sequence↗

PubMed2006

Association between intestinal parasitic infections and type of sanitation system in rural El Salvador.

OBJECTIVE: To identify demographic, behavioural and environmental determinants of intestinal parasitic infection, evaluate the impact of a variety of dry sanitation systems on intestinal parasitic infection, and evaluate the safety of using stored biosolids in agriculture in order to guide future sanitation interventions in rural areas of El Salvador. METHODS: Interviews were conducted with 109 households in eight communities where double-vaulted and solar urine-diverting desiccating latrines, pit latrines or no latrines were used. Faecal samples from 499 individuals were tested for enteric helminths and protozoa. RESULTS: Users of solar desiccating latrines had the lowest prevalence of enteric parasite infection. Double-vault, urine-diverting desiccating latrines effectively reduced the transmission of some pathogens, but may not achieve the conditions sufficient for the complete destruction of the more environmentally persistent pathogens, Ascaris lumbricoides and Trichuris trichiura. Contact with inadequately treated latrine biosolids was associated with an increased risk of Ascaris infection. CONCLUSIONS: Solar latrines were associated with the overall lowest prevalence of enteric parasitic infections. Members of households where latrine biosolids were used in agriculture had a higher prevalence of infection than those where biosolids were buried. We therefore recommend the promotion of solar latrines in rural areas of El Salvador over other dry sanitation systems, and recommend that stored biosolids not be used in agriculture.

Adolescent↗

PubMed2006

Global challenges in water, sanitation and health.

The year 2005 marks the beginning of the "International Decade for Action: Water for Life" and renewed effort to achieve the Millennium Development Goals (MDGS) to reduce by half the proportion of the world's population without sustainable access to safe drinking water and sanitation by 2015. Currently, UNICEF and WHO estimate that 1.1 billion people lack access to improved water supplies and 2.6 billion people lack adequate sanitation. Providing safe water and basic sanitation to meet the MDGs will require substantial economic resources, sustainable technological solutions and courageous political will. We review five major challenges to providing safe water and sanitation on a global basis: (1) contamination of water in distribution systems, (2) growing water scarcity and the potential for water reuse and conservation, (3) implementing innovative low-cost sanitation systems, (4) providing sustainable water supplies and sanitation for megacities, and (5) reducing global and regional disparities in access to water and sanitation and developing financially sustainable water and sanitation services.

Agriculture↗

PubMed2005

A field study of the microbiological quality of fresh produce.

The Centers for Disease Control and Prevention has reported that foodborne disease outbreaks associated with fruits and vegetables increased during the past decade. This study was conducted to characterize the routes of microbial contamination in produce and to identify areas of potential contamination from production through postharvest handling. We report here the levels of bacterial indicator organisms and the prevalence of selected pathogens in produce samples collected from the southern United States. A total of 398 produce samples (leafy greens, herbs, and cantaloupe) were collected through production and the packing shed and assayed by enumerative tests for total aerobic bacteria, total coliforms, total Enterococcus, and Escherichia coli. These samples also were analyzed for Salmonella, Listeria monocytogenes, and E. coli O157:H7. Microbiological methods were based on methods recommended by the U.S. Food and Drug Administration. For all leafy greens and herbs, geometric mean indicator levels ranged from 4.5 to 6.2 log CFU/g (aerobic plate count); less than 1 to 4.3 log CFU/g (coliforms and Enterococcus); and less than 1 to 1.5 log CFU/g (E. coli). In many cases, indicator levels remained relatively constant throughout the packing shed, particularly for mustard greens. However, for cilantro and parsley, total coliform levels increased during the packing process. For cantaloupe, microbial levels significantly increased from field through packing, with ranges of 6.4 to 7.0 log CFU/g (aerobic plate count); 2.1 to 4.3 log CFU/g (coliforms); 3.5 to 5.2 log CFU/g (Enterococcus); and less than 1 to 2.5 log CFU/g (E. coli). The prevalence of pathogens for all samples was 0, 0, and 0.7% (3 of 398) for L. monocytogenes, E. coli O157:H7, and Salmonella, respectively. This study demonstrates that each step from production to consumption may affect the microbial load of produce and reinforces government recommendations for ensuring a high-quality product.

Bacteria↗

PubMed2004

Diagnosis of norwalk virus infection by indirect enzyme immunoassay detection of salivary antibodies to recombinant norwalk virus antigen.

Simple diagnostic tests are needed for the detection of norovirus (NoV) outbreaks. Salivary antibody assays provide an attractive alternative to collecting and testing serum or stool samples. Antibodies to Norwalk virus (NV) in oral fluid samples were compared with NV antibodies in serum collected from 38 volunteers challenged with NV inoculum. Pre- and postchallenge (day 4, 8, 14, and 21) saliva and serum samples were examined by enzyme immunoassay (EIA) using recombinant NV antigen. Of 18 infected subjects (those who shed NV in stool or who demonstrated immunoglobulin G [IgG] seroconversion), 15 (83%) had > or =4-fold increases in NV-specific salivary IgA and 15 (83%) had > or =4-fold increases in NV-specific salivary IgG when prechallenge and postchallenge saliva samples were compared. When the results of the IgA and IgG assays were combined, all 18 infected subjects showed > or =4-fold increases in NV-specific salivary IgG or IgA postchallenge titers compared to their prechallenge titers. One of 19 uninfected subjects had a > or =4-fold increase in NV-specific salivary IgG. The sensitivity of the combined assay results was 100%, and the specificity was 95%. NV-specific salivary IgA titers peaked around 14 days postchallenge. NV-specific salivary IgG and serum IgG titers continued to rise through 21 days postchallenge. The application of this EIA to an elementary school outbreak indicated that 67% of the subjects with confirmed infections had >4-fold rises in anti-NoV IgA when an antigen in the same genetic cluster as the outbreak virus was used. This is the first documented mucosal antibody response to NoV in children. This EIA provides a useful approach for diagnosing NoV outbreaks.

Adult↗

PubMed2004

Norovirus capture with histo-blood group antigens reveals novel virus-ligand interactions.

Noroviruses are genetically diverse, uncultivable, positive-sense RNA viruses and are the most common cause of epidemic acute gastroenteritis in humans in the United States. Recent studies of norovirus attachment in vitro by using recombinant virus-like particles (VLPs) suggest that various norovirus strains exhibit different patterns of attachment to ABH histo-blood group antigens, which are carbohydrate epitopes present in high concentrations on mucosal cell surfaces of the gut. However, attachment of live norovirus strains to histo-blood group antigens has not been investigated to date. Utilizing a newly designed magnetic bead-virus capture method, we characterized histo-blood group antigen attachment properties of various norovirus strains obtained from clinical stool specimens to compare the attachment properties of wild-type virus and VLPs and to further map norovirus attachment. Consistent with previous reports using VLPs, various strains of noroviruses exhibited different patterns of attachment to histo- blood group antigens. Norwalk virus bound specifically to H type 1, H type 3, and Le(b). Two genogroup II noroviruses, one representing the Toronto genotype and the other from a novel genotype, bound specifically to Le(b). A Desert Shield-like strain did not attach to H types 1, 2, or 3, H type 1 and 3 precursors, Le(a), or Le(b). Surprisingly, wild-type Snow Mountain virus (SMV) attached specifically to H type 3, which contradicted previous findings with SMV VLPs. On further investigation, we found that stool components promote this attachment, providing the first known observation that one or more components of human feces could promote and enhance norovirus attachment to histo-blood group antigens.

ABO Blood-Group System↗

PubMed2004

Human challenge pilot study with Cyclospora cayetanensis.

We describe a pilot study that attempted to infect human volunteers with Cyclospora cayetanensis. Seven healthy volunteers ingested an inoculum of Cyclospora oocysts (approximately 200-49,000 oocysts). The volunteers did not experience symptoms of gastroenteritis, and no oocysts were detected in any stool samples during the 16 weeks volunteers were monitored.

Adult↗

PubMed2003

Evaluation of the NucliSens Basic Kit assay for detection of Norwalk virus RNA in stool specimens.

Norwalk-like viruses (NLVs) are a genetically diverse group of human caliciviruses that are the most common cause of epidemic gastroenteritis and are detected typically in stool by reverse transcription (RT)-PCR or electron microscopy (EM). The application of a rapid nucleic acid sequence-based amplification (NASBA) assay for the detection of NLV RNA in stool is described using the NucliSens Basic Kit. Primers and probes for the NLV Basic Kit assay were based on the RNA polymerase region of the prototype NLV, Norwalk virus (NV) genome and could consistently detect 10(4) RT-PCR detectable units of NV RNA in a stool filtrate. When compared directly with RT-PCR on a dilution series of NV stool filtrate, the NucliSens Basic Kit assay was equally sensitive. Cross-reactivity studies with a representative panel of other enteric pathogens were negative. When applied to 15 stool specimens from NV-challenged volunteers, the NASBA Basic Kit application for NV detection yielded 100% sensitivity, 50% specificity, and 67% concordance, using RT-PCR as the 'gold standard'. Despite the specificity of the NASBA primer/probe sequences for NV, other representatives from both NLV genogroups I and II could be detected by the Basic Kit assay in outbreak stool specimens, although the results were inconsistent. Our results suggest that the NucliSens Basic Kit assay provides a rapid and sensitive alternative to RT-PCR for detecting NV RNA in stool specimens. However, improvements in test specificity and primer design will be needed before the assay can be used routinely in the clinical setting.

Caliciviridae Infections↗

PubMed2002

Improved detection of human enteric viruses in foods by RT-PCR.

Human enteric viruses (including hepatitis A virus (HAV) and Norwalk-like viruses (NLVs)) are now recognized as common causes of foodborne disease. While methods to detect these agents in clinical specimens have improved significantly over the last 10 years, applications to food samples have progressed more slowly. In an effort to improve the sensitivity and speed of virus detection from non-shellfish food commodities by reverse transcription-polymerase chain reaction (RT-PCR), we (i) evaluated multiple RNA extraction methods; (ii) compared alternative NLV primer sets; and (iii) developed a one-step RT-PCR method. Hamburger and lettuce samples, processed for virus concentration using a previously reported filtration-extraction-precipitation procedure, were inoculated with HAV or NV. Several RNA extraction methods (guanidinium isothiocyanate, microspin column, QIAshredder Homogenizer, and TRIzol) and primer pairs were compared for overall RNA yield (microg/ml), purity (A(260)/A(280)), and RT-PCR limits of detection. The use of TRIzol with the QIAshredder Homogenizer (TRIzol/Shred) yielded the best RT-PCR detection limits (<1 RT-PCR amplifiable units/reaction for NV), and the NVp110/NVp36 primer set was the most efficient for detecting NV from seeded food samples. A one-step RT-PCR protocol using the TRIzol/Shred extraction method and the NVp110/NVp36 or HAV3/HAV5 primer sets demonstrated improved sensitivity (>10-fold) over the routinely used two-step method. HAV RNA was detected by RT-PCR at initial inoculum levels corresponding to <10 and <100 PFU per 300 microl sample concentrate (corresponding to 6 g food sample) for hamburger and lettuce, respectively. NV RNA was detected by RT-PCR at initial inoculum levels <5 and <50 RT-PCR amplifiable units per 300 microl concentrate (corresponding to 6 g food sample) for hamburger and lettuce, respectively. Residual RT-PCR inhibitors were effectively removed as evidenced by the ability to detect viral RNA in food concentrates without prior dilution. The methods reported here show promise for rapid, sensitive detection of human enteric viruses in foods.

DNA Primers↗

PubMed2002

Binding of Norwalk virus-like particles to ABH histo-blood group antigens is blocked by antisera from infected human volunteers or experimentally vaccinated mice.

Attachment of Norwalk (NV), Snow Mountain (SMV), and Hawaii (HV) virus-like particles (VLPs) to specific ABH histo-blood group antigens was investigated by using human saliva and synthetic biotinylated carbohydrates. The three distinct Norwalk-like viruses (NLVs) have various capacities for binding ABH histo-blood group antigens, suggesting that different mechanisms for NLV attachment likely exist. Importantly, antisera from NV-infected human volunteers, as well as from mice inoculated with packaged Venezuelan equine encephalitis virus replicons expressing NV VLPs, blocked the ability of NV VLPs to bind synthetic H type 1, Le(b), and H type 3, suggesting a potential mechanism for antibody-mediated neutralization of NV.

ABO Blood-Group System↗

PubMed2002

Expression and self-assembly of norwalk virus capsid protein from venezuelan equine encephalitis virus replicons.

The Norwalk virus (NV) capsid protein was expressed using Venezuelan equine encephalitis virus replicon particles (VRP-NV1). VRP-NV1 infection resulted in large numbers of recombinant NV-like particles that were primarily cell associated and were indistinguishable from NV particles produced from baculoviruses. Mutations located in the N-terminal and P1 domains of the NV capsid protein ablated capsid self-assembly in mammalian cells.

Animals↗