Recalls Associated with Food Allergens and Gluten in FDA-Regulated Foods from Fiscal Years 2013 to 2019

Allergens are one of the leading causes of food recalls in the US. The Food and Drug Administration (FDA) enforces requirements relating to major food allergens (MFAs) and gluten-free labeling to ensure food safety for allergic and celiac patients, respectively. Violative foods are subject to recalls. In this study, recall data for FDA-regulated foods were analyzed for fiscal years (FYs) 2013-2019 to identify trends and root causes associated with 1471 food allergen and gluten recalls. Of the 1471 recalls, 1415 recalls were due to MFAs, 34 recalls were due to gluten-free labeling violation and 23 recalls involved other allergens. Recalls due to MFAs overall increased during the study period with a peak incidence in FY 2017. MFA recall health hazard classifications were assessed as Class I (51.2%), Class II (45.5%), and Class III (3.3%). A majority of MFA recalls involved one allergen (78.8%). Milk was the most common MFA involved in MFA recalls (37.5%), followed by soy (22.5%) and tree nuts (21.6%). Almond, anchovy, and shrimp were the most common allergens recalled within the MFA groups of tree nuts, fish, and Crustacean shellfish, respectively. About 97% of MFA recalls involved one product category and among them, the category of 'bakery products, dough, bakery mixes and icings' ranked first (367 recalls), followed by the category of 'chocolate and cocoa products' (120 recalls). Labeling-associated errors accounted for 71.1% of MFA recalls with known root causes (914 out of 1286). It is important for the industry to develop and implement appropriate allergen controls to reduce the number of MFA recalls.

Effects of diet on skin sensitization by nickel, poison ivy, and sesquiterpene lactones

Skin contact or exposure to sensitizers often occurs as a consequence of occupational exposures (e.g. poison ivy in forestry), wearing jewelry (e.g. nickel), or use of cosmetics (e.g. fragrances). However, many of the known skin sensitizers or their chemical variants are also consumed orally through foods or other sources. Since oral exposure to antigenic substances can lead to tolerance, consumption of sensitizers may impact the development and potency of skin sensitization, especially if the sensitizer is consumed early in life, prior to the first skin contact. To address this issue, we have reviewed human clinical and epidemiological literature relevant to this subject and evaluated whether early oral exposures to relevant sensitizers, or their chemical variants, are associated with reduced prevalence of skin sensitization to three main allergic sensitizers - nickel, urushiols of poison ivy, and sesquiterpene lactones of chrysanthemum and other plants.

Neural activity of heterogeneous inhibitory spiking networks with delay

We study a network of spiking neurons with heterogeneous excitabilities connected via inhibitory delayed pulses. For globally coupled systems the increase of the inhibitory coupling reduces the number of firing neurons by following a winner-takes-all mechanism. For sufficiently large transmission delay we observe the emergence of collective oscillations in the system beyond a critical coupling value. Heterogeneity promotes neural inactivation and asynchronous dynamics and its effect can be counteracted by considering longer time delays. In sparse networks, inhibition has the counterintuitive effect of promoting neural reactivation of silent neurons for sufficiently large coupling. In this regime, current fluctuations are on one side responsible for neural firing of subthreshold neurons and on the other side for their desynchronization. Therefore, collective oscillations are present only in a limited range of coupling values, which remains finite in the thermodynamic limit. Out of this range the dynamics is asynchronous and for very large inhibition neurons display a bursting behavior alternating periods of silence with periods where they fire freely in absence of any inhibition.

Modeling driver cells in developing neuronal networks

Spontaneous emergence of synchronized population activity is a characteristic feature of developing brain circuits. Recent experiments in the developing neo-cortex showed the existence of driver cells able to impact the synchronization dynamics when single-handedly stimulated. We have developed a spiking network model capable to reproduce the experimental results, thus identifying two classes of driver cells: functional hubs and low functionally connected (LC) neurons. The functional hubs arranged in a clique orchestrated the synchronization build-up, while the LC drivers were lately or not at all recruited in the synchronization process. Notwithstanding, they were able to alter the network state when stimulated by modifying the temporal activation of the functional clique or even its composition. LC drivers can lead either to higher population synchrony or even to the arrest of population dynamics, upon stimulation. Noticeably, some LC driver can display both effects depending on the received stimulus. We show that in the model the presence of inhibitory neurons together with the assumption that younger cells are more excitable and less connected is crucial for the emergence of LC drivers. These results provide a further understanding of the structural-functional mechanisms underlying synchronized firings in developing circuits possibly related to the coordinated activity of cell assemblies in the adult brain.

A 28-year-old woman with fever, rash, and pancytopenia

A 28-year-old Hispanic woman was admitted to the hospital with fever, sore throat, arthralgia, and a generalized rash of 2 weeks' duration. Her medical history was significant for various food and medication allergies. Multiple antibiotics were given for suspected infection, and she subsequently developed a new skin rash, acute liver injury, eosinophilia, and pancytopenia. Additional studies showed hypertriglyceridemia; elevated interleukin-2 receptor levels; absent natural killer cell activity; and hemophagocytosis in skin, liver, and bone marrow biopsy specimens. Treatment with intravenous immunoglobulin and steroids resulted in complete remission.

Prevalence of self-reported food allergy in U.S. adults: 2001, 2006, and 2010

BACKGROUND

Epidemiologic evidence indicates that food allergies are increasing in the population. Information on a change in self-reported food allergy (srFA) in adults over time is lacking.

OBJECTIVE

To report the prevalence of srFA and compare differences at three time points over a decade.

METHODS

We analyzed srFA and reported physician-diagnosed food allergy in >4000 U.S. adults who participated in the 2010 U.S. Food and Drug Administration Food Safety Survey. Information on causative food(s), reaction severity characteristics, and various diagnostic factors was also analyzed. We compared 2010 Food Safety Survey data with 2006 and 2001 data, and highlighted relevant differences.

RESULTS

SrFA prevalence increased significantly, to 13% in 2010 and 14.9% in 2006 compared with 9.1% in 2001 (p < 0.001). Physician diagnosed food allergy was 6.5% in 2010, which was not significantly different compared with 7.6% in 2006 and 5.3% in 2001. SrFA increased in both men and women, non-Hispanic white and black adults, 50-59 year olds, and in adults with a high school or lower education. In 2010, milk, shellfish, and fruits were the most commonly reported food allergens, similar to 2001. Also, in 2010, 15% of reactions reportedly required a hospital visit and 8.4% were treated with epinephrine. Minor differences in reaction severity characteristics were noted among the surveys.

CONCLUSIONS

Analysis of survey results indicates that the prevalence of srFA increased among U.S. adults from 2001 to 2010 and that adults are increasingly self-reporting FAs without obtaining medical diagnosis. Improved education about food allergies is needed for this risk group.

Prevalence of self reported food allergy in US adults: 2001, 2006, and 2010

BACKGROUND

Epidemiologic evidence indicates that food allergies are increasing in the population. Information on a change in self-reported food allergy (srFA) in adults over time is lacking.

OBJECTIVE

To report the prevalence of srFA and compare differences at three time points over a decade.

METHODS

We analyzed srFA and reported physician-diagnosed food allergy in 4000 U.S. adults who participated in the 2010 U.S. Food and Drug Administration Food Safety Survey. Information on causative food(s), reaction severity characteristics, and various diagnostic factors was also analyzed. We compared 2010 Food Safety Survey data with 2006 and 2001 data, and highlighted relevant differences.

RESULTS

SrFA prevalence increased significantly, to 13% in 2010 and 14.9% in 2006 compared with 9.1% in 2001 (p less than 0.001). Physician diagnosed food allergy was 6.5% in 2010, which was not significantly different compared with 7.6% in 2006 and 5.3% in 2001. SrFA increased in both men and women, non-Hispanic white and black adults, 50-59 year olds, and in adults with a high school or lower education. In 2010, milk, shellfish, and fruits were the most commonly reported food allergens, similar to 2001. Also, in 2010, 15% of reactions reportedly required a hospital visit and 8.4% were treated with epinephrine. Minor differences in reaction severity characteristics were noted among the surveys.

CONCLUSIONS

Analysis of survey results indicates that the prevalence of srFA increased among U.S. adults from 2001 to 2010 and that adults are increasingly self-reporting FAs without obtaining medical diagnosis. Improved education about food allergies is needed for this risk group.

Clique of functional hubs orchestrates population bursts in developmentally regulated neural networks

It has recently been discovered that single neuron stimulation can impact network dynamics in immature and adult neuronal circuits. Here we report a novel mechanism which can explain in neuronal circuits, at an early stage of development, the peculiar role played by a few specific neurons in promoting/arresting the population activity. For this purpose, we consider a standard neuronal network model, with short-term synaptic plasticity, whose population activity is characterized by bursting behavior. The addition of developmentally inspired constraints and correlations in the distribution of the neuronal connectivities and excitabilities leads to the emergence of functional hub neurons, whose stimulation/deletion is critical for the network activity. Functional hubs form a clique, where a precise sequential activation of the neurons is essential to ignite collective events without any need for a specific topological architecture. Unsupervised time-lagged firings of supra-threshold cells, in connection with coordinated entrainments of near-threshold neurons, are the key ingredients to orchestrate population activity.

To which extent a single neuron can influence brain circuits/networks dynamics? Why only a few neurons display such a strong power? These open questions are inspired by recent experimental observations in developing and adult neuronal circuits, as well as by classical debates within the framework of the single neuron doctrine. In this work we identify and present a mechanism which can explain in neuronal circuits, at some early stage of their development, how and why only a few specific neurons can exhibit such power. For this purpose, we consider a standard neuronal network model whose population activity is characterized by bursting behavior. The introduction of a distribution of correlated neuronal excitabilities and degrees, inspired by the simultaneous presence of younger and older neurons in the network, leads to the emergence of functional hub neurons. These critical cells, whenever perturbed, are capable of suppressing network synchronization. Notably, we show that their strong influence on the population dynamics is not related to their structural properties, but to their operational and structural integration into a clique. These results highlight how network-wide effects can be induced by single neurons without any need for a specific topological architecture.

Infant feeding practices and reported food allergies at 6 years of age

OBJECTIVE

The goal of this study was to identify the frequency of physician-diagnosed food allergies among 6-year-old US children and study the impact of exclusive breastfeeding and complementary food introduction on this frequency.

METHODS

Data were analyzed from children who participated in the Infant Feeding Practices Study II Year 6 Follow-Up Study (Y6FU). Children with probable food allergy (pFA) were defined as children with report of physician-diagnosed food allergy at age 6 years. Subgroups of pFA included children who were not diagnosed before 1 year of age (new pFA) and those with atopic risk factors (high risk).

RESULTS

Prevalence of total pFA in the Y6FU was 6.34%. The majority of these children had new pFA and high-risk factors. Higher maternal education, higher family income, family history of food allergy, and reported eczema before 1 year of age were significantly associated with higher odds of total or new pFA. Exclusive breastfeeding duration and timing of complementary food introduction were not significantly associated with total pFA. However, exclusive breastfeeding of ≥4 months compared with no breastfeeding was marginally associated with lower odds of new pFA (adjusted odds ratio: 0.51; P = .07); this effect was not observed with high-risk children.

CONCLUSIONS

Analysis of infant and maternal variables in the Y6FU cohort of US children revealed that socioeconomic and atopic factors were the main predictors of pFA at age 6 years. Exclusive breastfeeding of ≥4 months may have a preventive effect on development of pFA after 1 year of age in non high-risk children.

An investigational report into the causes of pine mouth events in US consumers

Between July 2008 and June 2012, the US Food and Drug Administration received 501 consumer reports of prolonged taste disturbances consistent with pine mouth syndrome. Consumers consistently reported a delayed bitter or metallic taste beginning hours to days following consumption of pine nuts that recurred with intake of any food or meal. This dysgeusia lasted in some cases up to a few weeks, but would eventually resolve without serious health consequences. To evaluate these reports, a questionnaire was developed to address various characteristics of the pine nuts consumed, pertinent medical history of complainants and other dysgeusia-related factors. Pine nut samples associated with 15 complaints were collected for analysis. The investigation of reports found no clear evidence of an underlying medical cause or common trigger that could adequately explain the occurrence of dysgeusia in complainants. Rather, the results of our investigation suggest that the occurrence of "pine mouth syndrome" in US consumers is correlated with the consumption of the pine nut species Pinus armandii.

Collective dynamics in sparse networks

The microscopic and macroscopic dynamics of random networks is investigated in the strong-dilution limit (i.e., for sparse networks). By simulating chaotic maps, Stuart-Landau oscillators, and leaky integrate-and-fire neurons, we show that a finite connectivity (of the order of a few tens) is able to sustain a nontrivial collective dynamics even in the thermodynamic limit. Although the network structure implies a nonadditive dynamics, the microscopic evolution is extensive (i.e., the number of active degrees of freedom is proportional to the number of network elements).

Use of the chloroplast gene ycf1 for the genetic differentiation of pine nuts obtained from consumers experiencing dysgeusia

Pine nuts are a part of traditional cooking in many parts of the world and have seen a significant increase in availability/use in the United States over the past 10 years. The U.S. Food and Drug Administration (US FDA) field offices received 411 complaints from U.S. consumers over the past three years regarding taste disturbances following the consumption of pine nuts. Using analysis of fatty acids by gas chromatography with flame ionization detection, previous reports have implicated nuts from Pinus armandii (Armand Pine) as the causative species for similar taste disturbances. This method was found to provide insufficient species resolution to link FDA consumer complaint samples to a single species of pine, particularly when samples contained species mixtures of pine nuts. Here we describe a DNA based method for differentiating pine nut samples using the ycf1 chloroplast gene. Although the exact cause of pine nut associated dysgeusia is still not known, we found that 15 of 15 samples from consumer complaints contained at least some Pinus armandii, confirming the apparent association of this species with taste disturbances.

Discrete breathers in a realistic coarse-grained model of proteins

We report the results of molecular dynamics simulations of an off-lattice protein model featuring a physical force-field and amino-acid sequence. We show that localized modes of nonlinear origin, discrete breathers (DBs), emerge naturally as continuations of a subset of high-frequency normal modes residing at specific sites dictated by the native fold. DBs are time-periodic, space-localized vibrational modes that exist generically in nonlinear discrete systems and are known for their resilience and ability to concentrate energy for long times. In the case of the small β-barrel structure that we consider, DB-mediated localization occurs on the turns connecting the strands. At high energies, DBs stabilize the structure by concentrating energy on a few sites, while their collapse marks the onset of large-amplitude fluctuations of the protein. Furthermore, we show how breathers develop as energy-accumulating centres following perturbations even at distant locations, thus mediating efficient and irreversible energy transfers. Remarkably, due to the presence of angular potentials, the breather induces a local static distortion of the native fold. Altogether, the combination of these two nonlinear effects may provide a ready means for remotely controlling local conformational changes in proteins.

Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel

Food allergy is an important public health problem that affects children and adults and may be increasing in prevalence. Despite the risk of severe allergic reactions and even death, there is no current treatment for food allergy: the disease can only be managed by allergen avoidance or treatment of symptoms. The diagnosis and management of food allergy also may vary from one clinical practice setting to another. Finally, because patients frequently confuse nonallergic food reactions, such as food intolerance, with food allergies, there is an unfounded belief among the public that food allergy prevalence is higher than it truly is. In response to these concerns, the National Institute of Allergy and Infectious Diseases, working with 34 professional organizations, federal agencies, and patient advocacy groups, led the development of clinical guidelines for the diagnosis and management of food allergy. These Guidelines are intended for use by a wide variety of health care professionals, including family practice physicians, clinical specialists, and nurse practitioners. The Guidelines include a consensus definition for food allergy, discuss comorbid conditions often associated with food allergy, and focus on both IgE-mediated and non-IgE-mediated reactions to food. Topics addressed include the epidemiology, natural history, diagnosis, and management of food allergy, as well as the management of severe symptoms and anaphylaxis. These Guidelines provide 43 concise clinical recommendations and additional guidance on points of current controversy in patient management. They also identify gaps in the current scientific knowledge to be addressed through future research.

Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel

Food allergy is an important public health problem that affects children and adults and may be increasing in prevalence. Despite the risk of severe allergic reactions and even death, there is no current treatment for food allergy: the disease can only be managed by allergen avoidance or treatment of symptoms. The diagnosis and management of food allergy also may vary from one clinical practice setting to another. Finally, because patients frequently confuse nonallergic food reactions, such as food intolerance, with food allergies, there is an unfounded belief among the public that food allergy prevalence is higher than it truly is. In response to these concerns, the National Institute of Allergy and Infectious Diseases, working with 34 professional organizations, federal agencies, and patient advocacy groups, led the development of clinical guidelines for the diagnosis and management of food allergy. These Guidelines are intended for use by a wide variety of health care professionals, including family practice physicians, clinical specialists, and nurse practitioners. The Guidelines include a consensus definition for food allergy, discuss comorbid conditions often associated with food allergy, and focus on both IgE-mediated and non-IgE-mediated reactions to food. Topics addressed include the epidemiology, natural history, diagnosis, and management of food allergy, as well as the management of severe symptoms and anaphylaxis. These Guidelines provide 43 concise clinical recommendations and additional guidance on points of current controversy in patient management. They also identify gaps in the current scientific knowledge to be addressed through future research.

Irregular collective behavior of heterogeneous neural networks

We investigate a network of integrate-and-fire neurons characterized by a distribution of spiking frequencies. Upon increasing the coupling strength, the model exhibits a transition from an asynchronous regime to a nontrivial collective behavior. Numerical simulations of large systems indicate that, at variance with the Kuramoto model, (i) the macroscopic dynamics stays irregular and (ii) the microscopic (single-neuron) evolution is linearly stable.

Unfolding times for proteins in a force clamp

The escape process from the native valley for proteins subjected to a constant stretching force is examined using a model for a beta barrel. For a wide range of forces, the unfolding dynamics can be treated as one-dimensional diffusion, parametrized in terms of the end-to-end distance. In particular, the escape times can be evaluated as first passage times for a Brownian particle moving on the protein free-energy landscape, using the Smoluchowski equation. At strong forces, the unfolding process can be viewed as a diffusive drift away from the native state, while at weak forces thermal activation is the relevant mechanism. An escape-time analysis within this approach reveals a crossover from an exponential to an inverse Gaussian escape-time distribution upon passing from weak to strong forces. Moreover, a single expression valid at weak and strong forces can be devised both for the average unfolding time as well as for the corresponding variance. The analysis offers a possible explanation of recent experimental findings for the proteins ddFLN4 and ubiquitin.

Clinical reactivity to ingestion challenge with mixed mold extract may be enhanced in subjects sensitized to molds

Manifestations of mold allergy are classically associated with inhalation of mold spores leading to symptoms of asthma and other respiratory illnesses. It is largely unknown, however, whether ingestion of aeroallergenic molds, mold spores, or other fungi found in food can also elicit hypersensitivity reactions in mold-sensitive individuals. The aim of this study was to evaluate the association between exposure to molds by oral challenge and elicitation of symptoms in mold- versus nonmold-sensitive individuals. Thirty-four adult atopic subjects were randomized into mold-sensitive groups based on skin test reactivity by skin percutaneous testing (SPT) and/or intradermal (ID) testing to a mixed mold (MM) extract preparation. All subjects underwent a single-blinded, placebo-controlled food challenge to the MM preparation. A modified scoring system was used to grade the clinical severity of symptoms elicited by challenge. All subjects tolerated challenges to the maximal oral mold dose concentration. However, higher symptom scores after challenge were found in mold-sensitive subjects compared with nonmold-sensitive subjects (p = 0.01). When mold-sensitive subjects were compared based on SPT and/or ID reactivity, higher symptom scores and lower symptom-eliciting concentrations of mold were associated with the SPT reactive subgroup compared with the subgroup with ID reactivity alone. In summary, based on our challenge results and scoring model, mold-sensitive subjects compared with nonmold-sensitive subjects experienced cumulatively higher symptom scores after oral challenge to an MM extract preparation. Future studies are warranted to confirm whether ingestion of aeroallergenic molds in food may be another contributor to symptoms in mold-sensitive individuals.

Maternally reported food allergies and other food-related health problems in infants: characteristics and associated factors

OBJECTIVE

Our goal was to identify the frequency, demographics, and diagnostic characteristics associated with maternally reported food allergies and other food-related health problems among infants aged < or = 1 year.

METHODS

We analyzed data from the 2005-2007 Infant Feeding Practices Study II, a longitudinal survey of 2441 US mothers of healthy singletons from pregnancy through their infant's first year. Doctor diagnosis and symptoms-based criteria were used to identify a probable-food-allergic group from maternal reports of infant health problems with food.

RESULTS

More than one fifth of the 2441 mothers reported that their infant had a food-related problem; 6% (n = 143) had a probable food allergy, and 15% (n = 359) had other food-related problems. Forty percent of the infants with a food-related health problem were evaluated by a doctor. Gastrointestinal symptoms were more commonly reported in early infancy compared with skin-related symptoms, which were reported in later infancy, and 27% received medical treatment for the symptoms. Characteristics associated with increased incidence of probable food allergy included family histories of food allergy and type 1 diabetes, gestational diabetes, living in rural or urban areas, being black, and being male. Among all infants with a food-related health problem, the majority experienced their first problem by 6 months of age. Foods recognized to be major allergens were most commonly reported as the source of an allergy.

CONCLUSIONS

Food-related problems occurred at a high frequency in the first year of life. A better understanding of the demographics, family history, disease manifestations, and diagnoses may provide insight into public health efforts to minimize or prevent food allergies in infancy and to help differentiate food-allergic problems from nonallergic food problems in this age group.

Free-energy landscape of mechanically unfolded model proteins: extended Jarzinsky versus inherent structure reconstruction

The equilibrium free-energy landscape of off-lattice model heteropolymers as a function of an internal coordinate, namely the end-to-end distance, is reconstructed from out-of-equilibrium steered molecular dynamics data. This task is accomplished via two independent methods: By employing an extended version of the Jarzynski equality and the inherent structure formalism. A comparison of the free energies estimated with these two schemes with equilibrium results obtained via the umbrella sampling technique reveals a good quantitative agreement among all the approaches in a range of temperatures around the "folding transition" for the two examined sequences. In particular, for the sequence with good foldability properties, the mechanically induced structural transitions can be related to thermodynamical aspects of folding. Moreover, for the same sequence the knowledge of the landscape profile allows for a good estimation of the lifetimes of the native configuration for temperatures ranging from the folding to the collapse temperature. For the random sequence, mechanical and thermal unfolding appear to follow different paths along the landscape.

Analysis of food-allergic and anaphylactic events in the National Electronic Injury Surveillance System

BACKGROUND

The National Electronic Injury Surveillance System (NEISS) captures a nationally representative probability sample from hospital emergency departments (EDs) in the United States.

OBJECTIVE

Emergency department data from NEISS were analyzed to assess the magnitude and severity of adverse events attributable to food allergies.

METHODS

Emergency department events describing food-related allergic symptomatology were identified from 34 participating EDs from August 1 to September 30, 2003.

RESULTS

Extrapolation of NEISS event data predicts a total of 20,821 hospital ED visits, 2333 visits for anaphylaxis, and 520 hospitalizations caused by food allergy in the United States during the 2-month study period. The median age was 26 years; 24% of visits involved children < or =5 years old. Shellfish was the most frequently implicated food in persons > or =6 years old, whereas children < or =5 years old experienced more events from eggs, fruit, peanuts, and tree nuts. There were no reported deaths. Review of medical records found that only 19% of patients received epinephrine, and, using criteria established by a 2005 anaphylaxis symposium, 57% of likely anaphylactic events did not have an ED diagnosis of anaphylaxis.

CONCLUSION

Analysis of NEISS data may be a useful tool for assessing the magnitude and severity of food-allergic events. A criteria-based review of medical records suggests underdiagnosis of anaphylactic events in EDs.

Reconstructing the free-energy landscape of a mechanically unfolded model protein

The equilibrium free-energy landscape of an off-lattice model protein as a function of an internal (reaction) coordinate is reconstructed from out-of-equilibrium mechanical unfolding manipulations. This task is accomplished via two independent methods: by employing an extended version of the Jarzynski equality (EJE) and the protein inherent structures (ISs). In a range of temperatures around the "folding transition" we find a good quantitative agreement between the free energies obtained via EJE and IS approaches. This indicates that the two methodologies are consistent and able to reproduce equilibrium properties of the examined system. Moreover, for the studied model the structural transitions induced by pulling can be related to thermodynamical aspects of folding.

Double coherence resonance in neuron models driven by discrete correlated noise

We study the influence of correlations among discrete stochastic excitatory or inhibitory inputs on the response of the FitzHugh-Nagumo neuron model. For any level of correlation, the emitted signal exhibits at some finite noise intensity a maximal degree of regularity, i.e., a coherence resonance. Furthermore, for either inhibitory or excitatory correlated stimuli, a double coherence resonance is observable. Double coherence resonance refers to a (absolute) maximum coherence in the output occurring for an optimal combination of noise variance and correlation. All of these effects can be explained by taking advantage of the discrete nature of the correlated inputs.

Dynamical response of the Hodgkin-Huxley model in the high-input regime

The response of the Hodgkin-Huxley neuronal model subjected to stochastic uncorrelated spike trains originating from a large number of inhibitory and excitatory post-synaptic potentials is analyzed in detail. The model is examined in its three fundamental dynamical regimes: silence, bistability, and repetitive firing. Its response is characterized in terms of statistical indicators (interspike-interval distributions and their first moments) as well as of dynamical indicators (autocorrelation functions and conditional entropies). In the silent regime, the coexistence of two different coherence resonances is revealed: one occurs at quite low noise and is related to the stimulation of subthreshold oscillations around the rest state; the second one (at intermediate noise variance) is associated with the regularization of the sequence of spikes emitted by the neuron. Bistability in the low noise limit can be interpreted in terms of jumping processes across barriers activated by stochastic fluctuations. In the repetitive firing regime a maximization of incoherence is observed at finite noise variance. Finally, the mechanisms responsible for the different features appearing in the interspike-interval distributions (like multimodality and exponential tails) are clearly identified in the various regimes.

Differential modulation of allergic eye disease by chronic and acute ascaris infection

PURPOSE

To assess alterations in allergic ocular responses to nonparasite antigens in an experimental system in which mice were skewed toward a Th2 cytokine profile by helminth infection.

METHODS

Mice were inoculated with Ascaris suum (A. suum) eggs concurrent with ragweed (RW) sensitization (RW/acute) or by repeated inoculation before RW sensitization (RW/chronic). Control subjects were divided into RW, A. suum, and sham-sensitized groups. Animals were RW-challenged in the eye and examined for changes in ocular responses, inflammatory cell infiltrates, and in vitro assessment of cytokines after antigen restimulation. In subsequent experiments, CD4(+)/CD25+ T regulatory and CD4(+)/CD25- control T cells were adoptively transferred into mice before ocular challenge.

RESULTS

RW sensitization and challenge increased ocular symptoms and eosinophil infiltration into the conjunctiva over PBS control eyes. Acute A. suum infection significantly increased RW-induced clinical symptoms and eosinophil infiltrates in the conjunctiva (P = 0.0001) and resulted in the development of anterior uveitis. In contrast, RW/chronic infection provided protection from allergic responses to RW with significantly fewer eosinophils in the eye and reduced eotaxin levels. Transfer of CD4(+)/CD25+ T cells from RW/chronic mice into RW/acute animals also decreased disease intensity, suggesting that T regulatory cells may contribute to protection from allergic eye disease.

CONCLUSIONS

The current studies suggest acute parasitic infections exacerbate allergic symptoms, whereas chronic infections offer protection and provide possible explanations for the role of parasitic infection in susceptibility and resistance to nonparasite allergens.

Microbial-gut interactions in health and disease. Mucosal immune responses

The host gastrointestinal tract is exposed to countless numbers of foreign antigens and has embedded a unique and complex network of immunological and non-immunological mechanisms, often termed the gastrointestinal 'mucosal barrier', to protect the host from potentially harmful pathogens while at the same time 'tolerating' other resident microbes to allow absorption and utilization of nutrients. Of the many important roles of this barrier, it is the distinct responsibility of the mucosal immune system to sample and discriminate between harmful and beneficial antigens and to prevent entry of food-borne pathogens through the gastrointestinal (GI) tract. This system comprises an immunological network termed the gut-associated lymphoid tissue (GALT) that consists of unique arrangements of B cells, T cells and phagocytes which sample luminal antigens through specialized epithelia termed the follicle associated epithelia (FAE) and orchestrate co-ordinated molecular responses between immune cells and other components of the mucosal barrier. Certain pathogens have developed ways to bypass and/or withstand defence by the mucosal immune system to establish disease in the host. Some 'opportunistic' pathogens (such as Clostridium difficile) take advantage of host or other factors (diet, stress, antibiotic use) which may alter or weaken the response of the immune system. Other pathogens have developed mechanisms for invading gastrointestinal epithelium and evading phagocytosis/destruction by immune system defences. Once cellular invasion occurs, host responses are activated to limit local mucosal damage and repel the foreign influence. Some pathogens (Shigella spp, parasites and viruses) primarily establish localized disease while others (Salmonella, Yersinia, Listeria) use the lymphatic system to enter organs or the bloodstream and cause more systemic illness. In some cases, pathogens (Helicobacter pylori and Salmonella typhi) colonize the GI tract or associated lymphoid structures for extended periods of time and these persistent pathogens may also be potential triggers for other chronic or inflammatory diseases, including inflammatory bowel disease and malignancies. The ability of certain pathogens to avoid or withstand the host's immune assault and/or utilize these host responses to their own advantage (i.e. enhance further colonization) will dictate the pathogen's success in promoting illness and furthering its own survival.

F(ab)'2-mediated neutralization of C3a and C5a anaphylatoxins: a novel effector function of immunoglobulins

High-dose intravenous immunoglobulin (IVIG) prevents immune damage by scavenging complement fragments C3b and C4b. We tested the hypothesis that exogenous immunoglobulin molecules also bind anaphylatoxins C3a and C5a, thereby neutralizing their pro-inflammatory effects. Single-cell calcium measurements in HMC-1 human mast cells showed that a rise in intracellular calcium caused by C3a and C5a was inhibited in a concentration-dependent manner by IVIG, F(ab)2-IVIG and irrelevant human monoclonal antibody. C3a- and C5a-induced thromboxane (TXB2) generation and histamine release from HMC-1 cells and whole-blood basophils were also suppressed by exogenous immunoglobulins. In a mouse model of asthma, immunoglobulin treatment reduced cellular migration to the lung. Lethal C5a-mediated circulatory collapse in pigs was prevented by pretreatment with F(ab)2-IVIG. Molecular modeling, surface plasmon resonance (SPR) and western blot analyses suggested a physical association between anaphylatoxins and the constant region of F(ab)2. This binding could interfere with the role of C3a and C5a in inflammation.

IgE(+), Kit(-), I-A/I-E(-) myeloid cells are the initial source of Il-4 after antigen challenge in a mouse model of allergic pulmonary inflammation

BACKGROUND

IL-4 is generated within hours after antigen lung challenge and influences events that take place early in the induction of pulmonary inflammation. However, the cells responsible for this early IL-4 production in the lung are unknown.

OBJECTIVES

We sought to characterize the initial inflammatory events in the lung after antigen challenge and to identify cells responsible for producing IL-4 at early time points.

METHODS

Mice were sensitized with ovalbumin or passive IgE and challenged intranasally. Histologic measures of inflammation were used, and lung tissue cytokine production was analyzed by means of RT-PCR. Cells producing IL-4 were characterized by means of in situ hybridization and flow cytometry.

RESULTS

IL-4 mRNA was detectable 100 minutes after challenge in sensitized animals. Blockade of this early IL-4 downregulated vascular cell adhesion molecule 1 mRNA expression and attenuated the early recruitment of eosinophils to the lung. CD4-depleted and mast cell-deficient mice both expressed early IL-4. Cellular analysis revealed the presence of IL-4 protein at 100 minutes exclusively in IgE(+) myeloid cells that did not express CD3, Kit, or I-A/I-E. Moreover, IL-4 production induced by means of passive IgE sensitization and abrogated in FcR gamma-chain-deficient mice supports the conclusion that this IL-4 production is dependent on IgE/gamma-chain interaction.

CONCLUSION

IL-4 production by an IgE/gamma-chain-dependent mechanism occurs rapidly after allergen challenge. At these early time points, IL-4 is produced by a myeloid cell with the characteristics of a mouse basophil (IgE(+), Kit(-), I-A/I-E(-)). These data thus suggest that strategies targeting basophils should be considered in the treatment of early lung inflammation.

Studies of safety, infectivity and immunogenicity of a new temperature-sensitive (ts) 51-1 strain of Salmonella typhi as a new live oral typhoid fever vaccine candidate

This report describes the results of a phase 1 study evaluating the safety, infectivity, and immunogenicity of a new live oral Salmonella typhi temperature-sensitive (ts) 51-1 typhoid fever vaccine in the human. Three normal male subjects aged 23-32 years received three oral doses of S. typhi ts 51-1, each dose containing 10(9) organisms. Prior to and following immunization each subject was carefully monitored by clinical and laboratory parameters over a 2 week period during which serial specimens of blood and stool were analysed for the presence of the organism. Blood specimens were also obtained for the determination of serum antibody and cell-mediated immune responses and stool filtrates were analysed for the development of coproantibody. The results of these studies indicate that: (1) the vaccine is well tolerated with no clinical or laboratory evidence of adverse reactions; (2) ts 51-1 was detected in only one stool specimen from one volunteer; the organism recovered displayed characteristics of the ts 51-1 vaccine strain; and (3) although no significant humoral or cell-mediated lymphocytotoxic immune responses were detected in the blood, coproantibody was detected in stool specimens from all of the three immunized subjects and IgA-armed ADCC activity was detected in two of three subjects. These studies indicate that S. typhi ts 51-1 may be a suitable strain for the development of an improved oral typhoid fever vaccine. Studies are in progress to determine optimal methods of vaccine delivery preparatory to large phase 2 studies of efficacy.