Mark A. Gilger

Norwalk virus shedding after experimental human infection.

Noroviruses are shed in feces up to 8 weeks after infection.

Recombinant Norwalk virus–like particles given orally to volunteers: Phase I study

BACKGROUND & AIMS Norwalk virus (NV) is a major cause of epidemic gastroenteritis. The NV capsid is composed of a single protein that forms recombinant (rNV) virus-like particles (VLPs). In mice, these VLPs are immunogenic when administered orally without adjuvant, and they elicit serum immunoglobulin (Ig) G and intestinal IgA responses. The aim of this study was to evaluate the safety and immunogenicity of rNV VLPs in healthy volunteers. METHODS Twenty antibody-positive adults were orally administered rNV VLPs in sterile Milli-Q water on days 1 and 21. Vaccine safety and serum rNV-specific total and subclass IgG and IgA antibody responses were monitored. The immune response induced by the VLPs was compared with the response elicited by replicating virus. RESULTS No side effects were observed or reported by the volunteers. Serum IgG responses to rNV VLPs were dose-dependent, and all vaccinees given 250 microgram of rNV VLPs responded with >/=4-fold increases in serum IgG titers. Most of the volunteers (83%; 15 of 18) responded after the first rNV VLP dose and showed no increase in serum IgG titer after the second dose. CONCLUSIONS Orally administered rNV VLPs are safe and immunogenic in healthy adults when administered without adjuvant and are useful to test the mucosal delivery of immunogens.

Serological Correlate of Protection against Norovirus-Induced Gastroenteritis

BACKGROUND Norovirus infection is the leading cause of acute nonbacterial gastroenteritis. Histoblood group antigens (HBGAs) are host susceptibility determinants for Norwalk virus (NV) infection. We hypothesized that antibodies that block NV-HBGA binding are associated with protection from clinical illness following NV exposure. METHODS We developed an HBGA blocking assay to examine the ability of human serum to block the interaction of NV viruslike particles with H type 1 and H type 3 glycans. Serum samples from persons who were experimentally challenged with NV were evaluated. RESULTS There was a high correlation between the H type 1 and H type 3 synthetic glycan assays (r = 0.977; P < .001); the H type 1 assay had higher quantitative sensitivity (P < .001). Among 18 infected secretor-positive individuals, blocking titers peaked by day 28 after challenge and were higher for individuals who did not develop gastroenteritis than for those who developed gastroenteritis on days 0, 14, 28, and 180 (P < .05 for each). In addition, 6 of 6 subjects without gastroenteritis had measurable prechallenge blocking titers (>25), compared with 2 of 12 subjects with gastroenteritis (P = .002). CONCLUSIONS Blocking antibodies correlate with protection against clinical NV gastroenteritis. This knowledge will help guide the evaluation of new vaccine strategies and the elucidation of the nature of immunity to the virus. Trial registration. ClinicalTrials.gov identifier: NCT00138476.

Determination of the 50% Human Infectious Dose for Norwalk Virus

BACKGROUND  Noroviruses are the most common cause of gastroenteritis in the United States. An understanding of the infectious dose of these viruses is important for risk assessment studies. METHODS  Healthy adults were enrolled in a randomized, double-blind, placebo-controlled evaluation of different dosages of Norwalk virus. Eligible subjects were monitored for clinical gastroenteritis, and infection status was determined. The presence of virus in vomitus was also assessed. RESULTS  Fifty-seven persons were enrolled; 8 received placebo and an additional 8 persons were considered to be nonsusceptible on the basis of being secretor negative. Twenty-one persons were infected (all blood group O or A), and 67% of those infected developed viral gastroenteritis. The 50% human infectious dose was calculated to be 3.3 reverse transcription polymerase chain reaction units (approximately 1320 genomic equivalents [gEq]) for secretor-positive blood group O or A persons and 7.0 (approximately 2800 gEq) for all secretor-positive persons. The time of illness onset was inversely correlated with inoculum dose. The maximal concentration of virus shedding was higher for persons with gastroenteritis. Norwalk virus was identified in 15 of 27 (56%) vomitus samples at a median concentration of 41 000 gEq/mL. CONCLUSIONS  The 50% human infectious dose measured is higher than previous estimates and similar to that of other RNA viruses. Clinical Trials Registration NCT00138476.

Extraintestinal rotavirus infections in children with immunodeficiency

Some rotavirus strains, including vaccine candidates, have been demonstrated to cause hepatitis in immunodeficient and malnourished mice and to grow in human liver cells. To determine whether rotavirus spreads outside the intestine in naturally infected children, we examined tissues from four immunodeficient children affected with severe combined immunodeficiency disease, acquired immunodeficiency disease syndrome, or DiGeorge syndrome. Chronic rotavirus-related diarrhea, which persisted until death, had also developed in each child. Using indirect immunoperoxidase techniques, we identified rotavirus antigen in the liver and kidney with a hyperimmune guinea pig antiserum prepared to double-shelled rotavirus particles. Similar immunostaining with an antiserum to a rotavirus nonstructural protein (NS26) provided evidence of active virus replication. The observed reactivity was eliminated specifically when serial sections were immunostained with the same antiserum that had been absorbed with either double-shelled rotavirus particles or NS26. Immunostaining was not observed in the liver of children with other diseases (alpha 1-antitrypsin deficiency, inspissated bile syndrome, and acute rejection of a transplanted liver). These findings demonstrate that rotavirus infections in children can extend beyond the intestinal tract. Further studies are warranted to determine whether extraintestinal rotavirus replication occurs in children without severe immunodeficiency, such as malnourished children.

Norwalk Virus Vaccines: Challenges and Progress

Human caliciviruses (HuCVs) are the major cause of outbreaks of acute nonbacterial gastroenteritis throughout the world. An increasing recognition of the clinical significance of these viruses as human pathogens causing foodborne and waterborne disease indicates that an effective vaccine would be useful. This article reviews the current challenges that exist for the development of a vaccine for the HuCVs as well as the status of development of a candidate vaccine. HuCVs are viruses that exhibit a restricted tropism for infection of the gastrointestinal tract of humans, and a volunteer model of infection and disease is available. As pathogens with a restricted host range, the HuCVs are excellent models for understanding the mechanisms that mediate and regulate viral infection of the gastrointestinal tract and mucosal immunity in humans.

Gastroesophageal Reflux and Asthma in Children: A Systematic Review

CONTEXT: The relationship between gastroesophageal reflux disease (GERD) and asthma in children has been investigated; however, the nature of the association (if any) between these 2 conditions is unclear. OBJECTIVE: We performed a systematic review of the literature to examine the association between GERD and asthma in children. METHODS: A search of the medical literature was conducted by using PubMed and Embase (1966 through December 2008). Full-length articles in English that described at least 20 subjects younger than 18 years were included if they reported the prevalence of GERD (symptoms, pH studies, endoscopy/histology) in individuals with asthma or the prevalence of asthma in individuals with GERD. We calculated pooled odds ratios from studies that examined control groups, and we pooled prevalence estimates from all studies. RESULTS: A total of 20 articles that described 5706 patients fulfilled the inclusion and exclusion criteria. Seventeen studies used objective methods for documenting reflux (eg, pH probe, contrast imaging, impedance, esophagogastroduodenoscopy), 2 studies relied on symptom-based questionnaires, and 1 study used diagnostic codes. Most studies (n = 19) examined the prevalence of GERD in 3726 individuals with asthma and reported highly variable estimates (19.3%–80.0%) and a pooled average of 22.8% with GERD symptoms, 62.9% of 789 patients with abnormal esophageal pH, and 34.8% of 89 patients with esophagitis. Only 5 studies included controls and enrolled 1314 case-patients with asthma and 2434 controls without asthma. The average prevalence of GERD was 22.0% in asthma cases and 4.8% in controls (pooled odds ratio: 5.6 [95% confidence interval: 4.3–6.9]). CONCLUSIONS: There is a possible association between GERD and asthma in pediatric patients seen with asthma in referral settings. However, because of methodologic limitations of existing studies, the paucity of population-based studies, and a lack of longitudinal studies, several aspects of this association are unclear.

Childhood GERD is a risk factor for GERD in adolescents and young adults.

OBJECTIVE:The clinical course of gastroesophageal reflux disease (GERD) in children without comorbid illness (neurological deficits, congenital esophageal anomalies, chronic obstructive airway conditions) is unclear. Whether GERD in childhood progresses or predisposes to GERD in adulthood remains unknown.METHODS:We identified a cohort of individuals endoscopically diagnosed with GERD in childhood between 1990 and 1996. We excluded patients with comorbid illnesses. Eligible persons were contacted by telephone in person or through a household member and requested to complete a validated (in adults) symptom questionnaire between February 2001 and February 2003. Respondents were invited to undergo an upper endoscopy or to share results of any endoscopic examination performed within the past 12 months. We calculated the proportion of persons with GERD symptoms (monthly, weekly), and with current use of antisecretory medications (histamine-2-receptror antagonists [H2RA], proton pump inhibitors [PPI]).RESULTS:A total of 207 persons satisfied the inclusion and exclusion criteria and were contacted. Of those, 80 (39%) completed the questionnaire and 14/80 (18%) had an upper endoscopy. The mean age of participants was 20 years (SD = 4, range 10–40); most were Caucasian (73%), and 60% were female. GERD was documented at a mean age of 5 years (approximately a 15-yr duration of follow-up). Most participants (64/80, 80%) had at least monthly heartburn and/or acid regurgitation reported within the past 12 months; 18/80 (23%) reported at least weekly symptoms, and an additional three patients were asymptomatic but taking antisecretory therapy (H2RA or PPI). If all nonresponders were considered free of symptoms, then at least 31% had monthly symptoms, and 9% had weekly symptoms. Overall, 24 (30%) were currently taking either H2RA or PPI, and 19 patients had undergone fundoplication. There were no statistically significant differences between those who reported monthly GERD symptoms, weekly GERD symptoms, or no GERD symptoms as far as demographic features, age of GERD onset, receipt of fundoplication, or current GERD treatment. At endoscopy, three patients had mild to moderate erosive esophagitis.CONCLUSIONS:GERD in otherwise normal children can persist through adolescence and adulthood in a significant proportion of patients who continue to have GERD symptoms and signs, and use antisecretory medications. Childhood GERD is a risk factor for GERD in adolescence and adulthood.

Management of ingested magnets in children.

ABSTRACT We describe a comprehensive algorithm for the management of ingested rare-earth magnets in children. These newer and smaller neodymium magnets sold as adult toys are much stronger than the traditional magnets, and can attract each other with formidable forces. If >1 magnet is swallowed at the same time, or a magnet is co-ingested with another metallic object, the loops of intestine can be squeezed between them resulting in bowel damage including perforations. An algorithm that uses the number of magnets ingested, location of magnets, and the timing of ingestion before intervention helps to delineate the roles of the pediatric gastroenterologists and surgeons in the management of these cases.

Prevalence of endoscopic findings of erosive esophagitis in children: a population-based study.

Purpose: Symptoms of gastroesophageal reflux disease (GERD) occur in 2% to 7% of children. The manifestations of GERD can be limited to symptoms (eg, heartburn, regurgitation) or can be more complicated, such as erosive esophagitis, esophageal strictures, or Barrett esophagus. The prevalence of such GERD complications in children is unknown. The purpose of this study was to determine the prevalence of endoscopic findings of erosive esophagitis in children. Patients and Methods: All children ages 0 to 17 years, 11 months who underwent upper endoscopy that was recorded in the Pediatric Endoscopic Database System-Clinical Outcomes Research Initiative between 1999 and 2002 were included. Endoscopic reports that were incomplete or that did not include demographic features, indications for endoscopy, or endoscopic findings were excluded. Erosive esophagitis was defined either descriptively or by the Los Angeles classification. Esophageal biopsy was not evaluated. Results: A total of 7188 children who underwent upper endoscopy fulfilled the inclusion and exclusion criteria. Of those, 888 (12.4%) had erosive esophagitis. The median age of children with erosive esophagitis was 12.7 ± 4.9 years versus 10.0 ± 5.1 years in those without erosive esophagitis (P ≤ 0.0001). Of those with erosive esophagitis, 55.2% (490/888) were male, compared with 48.2% (3040/6300) in those without erosive esophagitis (P = 0.0001). Erosive esophagitis was found in 29 of 531 (5.5%) children ages 0 to 1 years and progressively increased to 106 in 542 individuals (19.6%) by age 17. Hiatal hernia was found in 68 (7.7%) of children with erosive esophagitis, compared with 157 (2.5%) without erosive esophagitis (P ≤ 0.0001. The prevalence of Barrett esophagus, esophageal stricture, ulcer, previous surgery, nodules, foreign body or retained food, and anatomic abnormalities was not significantly different between children with erosive esophagitis and those without. Conclusions: The frequency of erosive esophagitis is slightly higher in male children and increases with age. In contrast to erosive esophagitis in adults, there were no significant variations according to race or ethnicity. Hiatal hernia is the only endoscopic observation that predicts erosive esophagitis.