Anti-inflammatory properties of secretory IgA on intestinal epithelial cells during infection by Shigella flexneri

The intestinal immune system hasthe complex task to protect the sterilecore of the organism against invasion.Most of invasive enterobacteria targetintestinal epithelial cells (IEC) inducingmajor damages to the mucosa.Shigella flexneri, by invading IECand inducing inflammatory responsesof the colonic mucosa, causes bacillarydysentery, a bloody diarrhea thatis endemic worldwide. The mechanismof entry of this bacterium is stilla matter of debate. Mcells participatingin sampling antigens from the gutlumen through Peyers patches arecommonly considered as the primarysite of entry of the bacteria. Once inthe lamina propria, Shigella can invadeIEC via their basolateral poleand spread from cell-to-cell leading tomassive tissue destruction. More recently,data are accumulating demonstratingthat bacteria can also enter thelamina propria directly via IEC, underscoringIEC as another gate of entry.In addition, the protective role ofsecretory IgA (SIgA) produced byplasmocytes of the lamina propria hasbeen established in shigellosis contextbut few is known about its role inmaintaining IEC monolayer integrity.Here, the impact of the bacterium wasstudied using polarized CaCo 2 cellmonolayer apically infected with avirulent strain of S. flexneri eitheralone or complexed with its cognateanti LPS SIgA. Parameters associatedwith the infection process includingcytokine measurements (IL-8, IL-18)and laser scanning confocal microscopydetection of Zonula Occludens-1, a tight junction (TJ) protein werestudied.We demonstrate that bacteriaare able to infect IEC through theirluminal-like pole as well, inducingthe complete disruption of TJ and thedestruction of the whole reconstitutedCaCo-2 cell monolayer. SIgA uponneutralization of bacteria led to themaintenance of TJ supporting IEC integrity,and the modulation of cytokinereleases. Together with anti-inflammatoryproperties of SIgA, thefact that apical bacteria can damagethe IEC without the intervention ofother cells such as Mcells offers newpossibilities in understanding thepathogenic mechanisms involved inshigellosis.

Drosophila intestinal response to bacterial infection: activation of host defense and stem cell proliferation.

Although Drosophila systemic immunity is extensively studied, little is known about the fly's intestine-specific responses to bacterial infection. Global gene expression analysis of Drosophila intestinal tissue to oral infection with the Gram-negative bacterium Erwinia carotovora revealed that immune responses in the gut are regulated by the Imd and JAK-STAT pathways, but not the Toll pathway. Ingestion of bacteria had a dramatic impact on the physiology of the gut that included modulation of stress response and increased stem cell proliferation and epithelial renewal. Our data suggest that gut homeostasis is maintained through a balance between cell damage due to the collateral effects of bacteria killing and epithelial repair by stem cell division. The Drosophila gut provides a powerful model to study the integration of stress and immunity with pathways associated with stem cell control, and this study should prove to be a useful resource for such further studies.

Secretory IgA and intestinal epithelial cells at the interface between homeostasis regulation and protection against infection

RESUME DESTINE A UN LARGE PUBLICL'intestin est le siège d'intenses agressions de la part de l'ensemble des aliments ingérés, de bactéries agressives dites pathogènes mais également de bactéries dites commensales peuplant naturellement les surfaces intestinales muqueuses. Pour faire face, notre organisme arbore de nombreux niveaux de protections tant physiques, chimiques, mécaniques mais aussi immunitaires. La présence d'un type particulier de cellules, les cellules épithéliales (IEC) assurant une protection physique, ainsi que la production d'anticorps spécialisés par le système immunitaire appelés immunoglobulines sécrétoires A (SlgA) servent conjointement de première ligne de défense contre ces agressions externes. Néanmoins, comment le dialogue s'articule entre ces deux partenaires reste incomplet.Nous avons donc décidé de mimer ces interactions en modélisant les surfaces muqueuses par une monocouche de cellules différenciées en laboratoire. Des souches bactériennes isolées de l'intestin humain seules ou associées à des SlgA non-spécifiques ont été mises au contact de ce modèle cellulaire nous permettant de conclure quant à la présence effective d'une modulation du dialogue bactérie/lEC impliquant une activation de la réponse cellulaire vers un état de tolérance mutuelle. De façon surprenante, nous avons par ailleurs mis en évidence un type d'interaction nouveau entre ces anticorps et ces bactéries. Une étude biochimique nous a permis de détailler un nouveau rôle des SlgA médié par les sucres présents à leur surface dans le maintien d'une relation pacifique avec les commensaux perpétuellement présents, relations qualifiées d'homésostase intestinale.Le rôle protecteur des SlgA a par ailleurs été abordé pour avoir une meilleure appréhension de leur impact au niveau cellulaire lors d'infection par Shigella flexneri, bactérie causant la Shigellose, diarrhée sanglante responsable de la mort de plus d'un million de personnes chaque année. Basée sur le même modèle cellulaire, cette étude nous a permis de démontrer une nouvelle entrée de ce pathogène directement via les IEC. La présence d'anticorps spécifiques à la surface des bactéries restreint leur champs d'action contre les cibles intracellulaires identifiées que sont les filaments soutenant le squelette de la cellule, les fibres d'actine ainsi que les jonctions serrées, réseaux de protéines clés des interactions entre cellules. Cette ouverture au niveau cellulaire apporte un nouvel élan quant à la compréhension du rôle protecteur des SlgA lors d'attaques de l'intestin, protection semblant dépendante d'une agrégation des bactéries.Pour finir, nous avons mis en évidence la détection directe par les cellules de la présence d'anticorps libres dans l'intestin ajoutant une nouvelle réplique dans le dialogue complexe entre ces deux piliers de l'équilibre intestinal que sont les SlgA et les cellules épithéliales.RESUMELa muqueuse intestinale est dotée d'un réseau complexe de protections physico-chimiques, mécaniques ou immunologiques. Associées à un système immunitaire omniprésent, les cellules épithéliales intestinales {IEC) bordant la lumière intestinale ont la double tâche de protéger l'intérieur de l'organisme stérile contre l'invasion et la dissémination d'agents pathogènes, et de maintenir une relation pacifique avec la flore intestinale, rôles également joués par les immunoglobulines sécrétoires A (SlgA), anticorps les plus abondamment présents à la surface des muqueuses. Tant les IEC que les SlgA sont ainsi décrites comme convergeant vers le même objectif ; néanmoins, les rouages de leurs interactions restent largement inconnus.Pour répondre à cette question, des monocouches épithéliales reconstituées in vitro ont été incubées avec des souches commensales telles que des Lactobacillus ou des Bifodobacteria, seules ou complexées avec des SlgA non-spécifiques, nous permettant de décrypter l'influence des SlgA sur la détection des bactéries par les IEC, favorisant l'adhésion bactérienne et la cohésion cellulaire, augmentant l'activation de la voie NF-κΒ ainsi que la sécrétion de la cytokine thymic stromal lymphopoietin contrairement à celle de médiateurs pro-inflammatoires qui reste inchangée. Par ailleurs, une interaction Fab-indépendante est suggérée dans l'interaction SlgA/bactéries. Comme une interaction de faible affinité a été décrite comme prenant naturellement place au niveau de l'intestin, nous avons donc disséqué les mécanismes sous- jacents en utilisant un large spectre de bactérie associés à des protéines soit recombinantes soit isolées à partir de colostrum, mettant en évidence un rôle crucial des N-glycanes présents sur la pièce sécrétoire et soulignant une nouvelle propriété des SlgA dans l'homéostase intestinale.Intrinsèquement liés aux caractéristiques des SlgA, nous nous sommes également focalisés sur leur rôle protecteur lors d'infection par l'enteropathogène Shigella flexneri reproduites in vitro sur des monocouches polarisées. Nous avons tout d'abord démontré une nouvelle porte d'entrée pour ce pathogène directement via les IEC. L'agrégation des bactéries par les SlgA confère aux cellules une meilleure résistance à l'infection, retardant croissance bactérienne et entrée cellulaire, affectant par ailleurs leur capacité à cibler le cytosquelette et les jonctions serrées. La formation de tels cargos détectés de façon biaisée par les IEC apparaît comme une explication plausible au maintien de la cohésion cellulaire médiée par les SlgA.Enfin, le retrotransport des SlgA à travers les IEC a été abordé soulignant une participation active de ces cellules dans la détection de l'environnement extérieur, les impliquant possiblement dans l'activation d'un état muqueux stable.Conjointement, ces résultats indiquent que les SlgA représentent l'un des éléments-clés à la surface de la muqueuse et soulignent la complexité du dialogue établi avec l'épithélium en vue du maintien d'un fragile équilibre intestinal.ABSTRACTThe intestinal mucosa is endowed with a complex protective network melting physiochemical, mechanical and immunological features. Beyond the ubiquitous intestinal immune system, intestinal epithelial cells (IEC) lying the mucosal surfaces have also the dual task to protect the sterile core against invasion and dissemination of pathogens, and maintain a peaceful relationship with commensal microorganisms, aims also achieved by the presence of high amounts of secretory immunoglobulins A (SlgA), the most abundant immunoglobulin present at mucosal surfaces. Both IEC and SlgA are thus described to converge toward the same goal but how their interplay is orchestrated is largely unknown.To address this question, in vitro reconstituted IEC monolayers were first apically incubated with commensal bacteria such as Lactobacillus or Bifodobacteria strains either alone or in complexes with non-specific SlgA. Favoring the bacterial adhesion and cellular cohesion, SlgA impacts on the cellular sensing of bacteria, increasing NF-κΒ activation, and leading to cytokine releases restricted to the thymic stromal lymphopoietin and unaffected expression of pro-inflammatory mediators. Of main interest, bacterial recognition by SlgA suggested a Fab-independent interaction. As this low affinity, called natural coating occurs in the intestine, we further dissected the underlying mechanisms using a larger spectrum of commensal strains associated with recombinant as well as colostrum-derived proteins and pinpointed a crucial role of N-glycans of the secretory component, emphasizing an underestimated role of carbohydrates and another properties of SlgA in mediating intestinal homeostasis.As mucosal protection is also anchored in SlgA and IEC features, we focused on the cellular role of SlgA. Using IEC apical infection by the enteropathogen Shigella flexneri, we have first demonstrated a new gate of entry for this pathogen directly via IEC. Specific SlgA bacterial aggregation conferred to the cells a better resistance to infection, delaying bacterial growth and cellular entry, affecting their ability to damage both the cytoskeleton and the tight junctions. Formation of such big cargos differentially detected by IEC appears as a plausible explanation sustaining at the cellular level the antibody-mediated mucosal protection.Finally, SlgA retrotransport across IEC has been tackled stressing an active IEC sensing of the external environment possibly involved in the steady-state mucosal activation.All together, these results indicate that SlgA represents one of the pivotal elements at mucosal surfaces highlighting the complexity of the dialogue established with the epithelium sustaining the fragile intestinal balance.The Intestinal mucosa is endowed with a complex protective network melting physiochemical, mechanical and immunological features. Beyond the ubiquitous intestinal immune system, intestinal epithelial cells (IEC) lying the mucosal surfaces have also the dual task to protect the sterile core against invasion and dissemination of pathogens, and maintain a peaceful relationship with commensal microorganisms, aims also achieved by the presence of high amounts of secretory immunoglobulins A (SlgA), the most abundant immunoglobulin present at mucosal surfaces. Both IEC and SlgA are thus described to converge toward the same goal but how their interplay is orchestrated is largely unknown.To address this question, in vitro reconstituted IEC monolayers were first apically incubated with commensal bacteria such as Lactobacillus or Bifodobacteria strains either alone or in complexes with non-specific SlgA. Favoring the bacterial adhesion and cellular cohesion, SlgA impacts on the cellular sensing of bacteria, increasing NF-κΒ activation, and leading to cytokine releases restricted to the thymic stromal lymphopoietin and unaffected expression of pro-inflammatory mediators. Of main interest, bacterial recognition by SlgA suggested a Fab-independent interaction. As this low affinity, called natural coating occurs in the intestine, we further dissected the underlying mechanisms using a larger spectrum of commensal strains associated with recombinant as well as colostrum-derived proteins and pinpointed a crucial role of N-glycans of the secretory component, emphasizing an underestimated role of carbohydrates and another properties of SlgA in mediating intestinal homeostasis.As mucosal protection is also anchored in SlgA and IEC features, we focused on the cellular role of SlgA. Using IEC apical infection by the enteropathogen Shigella flexneri, we have first demonstrated a new gate of entry for this pathogen directly via IEC. Specific SlgA bacterial aggregation conferred to the cells a better resistance to infection, delaying bacterial growth and cellular entry, affecting their ability to damage both the cytoskeleton and the tight junctions. Formation of such big cargos differentially detected by IEC appears as a plausible explanation sustaining at the cellular level the antibody-mediated mucosal protection.Finally, SlgA retrotransport across IEC has been tackled stressing an active IEC sensing of the external environment possibly involved in the steady-state mucosal activation.All together, these results indicate that SlgA represents one of the pivotal elements at mucosal surfaces highlighting the complexity of the dialogue established with the epithelium sustaining the fragile intestinal balance.

Loss of intestinal epithelial barrier function in Salmonella Enteritidis infection

Intestinal infection with Salmonella enterica serotype Enteritidis, a food-borne infection spread to humans especially through contaminated eggs and egg-products as well as undercooked contaminated fresh meat, is the most common cause of intestinal inflammation in the European Union. Enteritis caused by Salmonella Enteritidis is characterized by fever, diarrhoea and abdominal pain. The disruption of the intestinal epithelial barrier function contributes to diarrhoea and is responsible for the perpetuation of the inflammatory process. In this sense, oxidative stress and the proinflammatory cytokines TNF-α, IFN-γ and IL-1β are described to induce the disorganization of the tight junctions (TJ), the most apical epithelial intercellular junctions and responsible for the paracellular permeability. The interest of this chapter relies not only in the investigation dealing with the mechanisms of TJ regulation but also in the contribution to the development of new tools for the prevention of epithelial barrier disruption in enteritis caused by Salmonella Enteritidis.

Relationship of intestinal histology with the resistance to Trichostrongylus colubriformis infection in three breeds of sheep

The study was carried out to evaluate the relationship of inflammatory intestinal cells with the resistance to Trichostrongylus colubriformis infections in three breeds of sheep (Santa Ines, Suffolk and Ile de France), naturally infected. Mast cells, eosinophils, and globule leucocytes were enumerated in intestinal mucosa. Histamine concentration was estimated in intestinal tissue samples and the length of male and female specimens were determined. The three breeds of sheep showed similar cellular response in the small intestine mucosa (P>0.05). There was extensive variation among sheep in the parasitological and inflammatory cell variables, even in lambs of the same breed. In general, animals presenting less inflammatory cells had a larger worm burden, higher fecal egg counts, and larger T. colubriformis worms. The inflammatory cells possibly impaired the parasite's establishment, development, and survival.

Effects of infection with Toxoplasma gondii oocysts on the intestinal wall and the myenteric plexus of chicken (Gallus gallus)

This paper aims to analyze the effects of the Toxoplasma gondii infection in the intestinal wall and myenteric plexus of chicken (Gallus gallus). Ten 36-day-old chickens were separated into two groups: control and experimental, orally inoculated with oocysts of the T. gondii strain M7741 genotype III. After 60 days the birds were submitted to euthanasia and had their duodenum removed. Part of the intestinal segments was submitted to histological routine, HE staining, PAS histochemical technique, and Alcian Blue. Qualitative analysis of the intestinal wall and comparative measurements among the groups with respect to total wall thickness, muscle tunic, mucosa, and tunica mucosa were carried out. Caliciform cells were quantified. The other part of the intestinal segments was fixed in formol acetic acid and dissected having the tunica mucosa and the tela submucosa removed. Neurons were stained with Giemsa, counted, and measured. Chickens from the experimental group presented diarrhea and inflammatory infiltrates in the tunica mucosa, thickness reduction of all the parameters assessed in the intestinal wall, and an increase of the number of caliciform cells. There was a ~70% reduction regarding the intensity of myenteric neurons; and the remaining cells presented a reduction of ~2.4% of the perikarion and ~40.5% of the nucleus (p<0.05). Chronic infection induced by T. gondii oocysts resulted in intestinal wall atrophy, mucin secretion increase, death and atrophy of chicken myenteric plexus neurons. Death and atrophy of myenteric plexus neurons may be related with the causes of diarrhea observed in chickens with toxoplasmosis.

Studies on IL-18 in HIV infection : effects of the cytokine on intestinal integrity, and platelets as a new source of the cytokine

L'interleukine IL-18 (IL-18), un membre de la famille de l’IL-1, est une cytokine pro-inflammatoire multifonctionnelle. Elle est produite par les monocytes, les macrophages, les cellules dendritiques, les cellules épithéliales, les kératinocytes et le cortex surrénal dans le corps humain. Cette cytokine est d'abord produite comme une protéine précurseure inactive, qui est par la suite clivée en une forme mature par la caspase-1 activée. La caspase, en elle-même, existe comme précurseur inactif dans les cellules humaines et requiert l'assemblage d'inflammasomes pour son activation. L'IL-18 pour joue un rôle clé dans la médiation des conditions inflammatoires. Notre laboratoire et d'autres ont montré que l'infection par le VIH est accompagnée d'une augmentation des taux circulants d'IL-18 avec une diminution des niveaux de son antagoniste, l'interleukine-18 binding protein (IL-18BP). Dans cette thèse, nous démontrons pour que l'IL-18 est également produite et sécrétée par les plaquettes humaines lors de leur activation. Les plaquettes contiennent des composants de l'inflammasome. Ils assemblent et activent la caspase-1, qui ensuite traite le précurseur de l'IL-18 dans sa forme mature au cours du processus d'activation des plaquettes. La cytokine est synthétisée de novo lors de l'activation des plaquettes. Contrairement à l'IL-18, les plaquettes expriment constitutivement l’IL-18BP, et la libèrent de manière constitutive, ainsi que lors de l'activation. L'IL-18 et l'IL-18BP sont colocalisés avec CD63, un marqueur pour les granules α des plaquettes. L'IL-18 libéré des plaquettes constitue la source principale de cette cytokine dans la circulation humaine chez les individus sains. Nous avons identifié des concentrations faibles de cette cytokine dans les lysats de plaquettes chez les individus infectés par le VIH par rapport à ceux en santé. D'autre part, les concentrations ont été augmentées dans le sérum et le plasma pauvre en plaquettes chez les individus infectés. Des résultats similaires ont été obtenus avec l'IL-18BP dans les lysats de plaquettes d'individus sains et infectés par le VIH. Cependant, des quantités plus faibles de cet antagoniste ont été trouvées dans le sérum et le plasma pauvre en plaquettes d'individus infectés par le VIH par rapport à ceux en santé. Nos résultats ont des implications importantes pour les maladies inflammatoires chroniques dans laquelle une activité accrue de l'IL-18 joue un rôle pathogène. Le VIH est également accompagné par une inflammation intestinale et une diminution de l'intégrité intestinale, mesurée par la réparation de la muqueuse, la régénération et la perméabilité. Cependant, on en sait peu sur la relation entre le niveau élevé de l'IL-18 associé à l'infection au VIH et la perméabilité intestinale: ceci n'a jamais été étudié. Dans cette thèse, nous démontrons le rôle du virus et sa protéine Tat à augmenter la production d'IL-18 chez deux lignées de cellules épithéliales intestinales (HT29 et Caco2) ainsi qu'une diminution de l'IL-18BP. L'IL-18 induit une hyperperméabilité de la barrière épithéliale en perturbant à la fois les jonctions serrées et adhérentes, et ce, en modulant l'expression et la distribution de l'occludine, de claudine-2 et de la bêta-caténine. Une désorganisation de l'actine F a également été observée dans les cellules lors de l'incubation avec l'IL-18. Les mêmes observations ont été faites avec la protéine Tat du VIH-1. Après une incubation prolongée, l'IL-18 a causé la mort des cellules intestinales et induit l'apoptose par l'activation de la caspase-1 et la caspase-3. Fait intéressant, les taux plasmatiques de lipopolysaccharides chez trois catégories différentes de patients au VIH (ART-naïf, ART-traitée et contrôleurs élite) sont en corrélation avec les niveaux plasmatiques de l'IL-18. Enfin, nous avons étudié la voie de signalisation à travers laquelle l'IL-18 induit une perméabilité intestinale accrue. En bref, nos études identifient les plaquettes comme une source importante d'IL-18, et leur activation lors d'une infection à VIH contribue à des concentrations accrues de cette cytokine. Le virus entraine également l'augmentation de la production de cytokines par les cellules épithéliales intestinales. L'activité biologique accrue de ces cytokines contribue à la pathogenèse du sida en augmentant la perméabilité intestinale et en causant la mort des cellules intestinales. L'IL-18 pourrait servir de cible moléculaire pour retarder la progression du sida et réduire l'inflammation chronique dans un stade précoce d'une infection à VIH.

New evidence for the antiquity of the intestinal parasite Trichuris (whipworm) in Europe

The whipworm, Trichuris trichiura L., is one of the most common human intestinal parasites worldwide, yet little is known of its origin and global spread. Archaeological records for this nematode have all been of Neolithic or later date, suggesting a possible association between the spread of pastoral farming and human acquisition of whipworm. This paper reports the discovery of eggs of the genus Trichuris in late Mesolithic deposits from south Wales, indicating that whipworm was present in Europe before the arrival of agriculture. This raises the possibility that human infection by Trichuris arose through contact with wild animals in parts of the landscape frequented by both human and animal groups.

The pathology of Plasmodium chabaudi infection is not ameliorated by the secreted filarial nematode immunomodulatory molecule, ES-62

ES-62 is a phosphorylcholine-containing glycoprotein secreted by filarial nematodes. This molecule has been shown to reduce the severity of inflammation in collagen-induced arthritis (CIA) in mice, a model of rheumatoid arthritis, via down-regulation of anti-collagen type 1 immune responses. Malaria parasites induce a pro-inflammatory host immune response and many of the symptoms of malaria are immune system-mediated. Therefore we have asked whether the immunomodulatory properties of ES-62 can down-regulate the severity of malaria infection in BALB/c mice infected with Plasmodium chabaudi. We have found that ES-62 has no significant effect on the course of P. chabaudi parasitaemia, and does not significantly affect any of the measures of malaria-induced pathology taken throughout infection.

Nematicidal activity of Solanum nigrum and S. sisymbriifolium extracts against the root-lesion nematode Pratylenchus goodeyi and its effects on infection and gene expression

The control of Pratylenchus goodeyi a common nematode parasite of banana crop in Madeira Island can benefit from searching for natural nematicides through plants extracts. With this aim we submitted Solanum nigrum and S. sisymbriifolium dried plants to a sequential extraction in the solvent sequence of dichloromethane, acetone, ethanol and water, and to na aqueous extraction of the fresh and dried plants. Analyses with the extracts at several concentrations were used to assess mobility and mortality on P. goodeyi. Results showed that the water extract and aqueous extracts from both plants at a concentration of 10 mg/mL affected nematode mobility and caused mortality but the acetone extract from S. nigrum was the most efficient, causing 100% mortality whereas dichloromethane had no effect on P. goodeyi. Determination of the lipophilic and phenolic compounds present in the two most effective Solanum extracts (acetone and water) and in dichloromethane extract revealed that some of these compounds had nematicidal activity. S. nigrum acetone extract (10 mg/mL) was used to find out the nematicidal potential following the effect at gene expression level and nematode behaviour. Genes coding for calreticulin and beta-1,4- endoglucanase related to parasitism and translocon-associated protein putatively connected to stress were obtained and its relative expression assessed in nematodes exposed to the extract. Results revealed that expression of Pg-CRT decreased showing to influence the infection, Pg-ENG remained steady and Pg-TRAPδ was induced over time exposure. Biological assays showed that P. goodeyi mobility and ability to infect the banana roots were affected as a decrease in the number of nematodes that reached the roots was obtained with the increased exposure time to the extract being implicated in the infection success. The information obtained from this thesis showed that S. nigrum has potential to be used for the development of a new control strategy against plant-parasitic nematodes.

Prevention of Salmonella infection by contact using intestinal flora of adult birds and/or a mixture of organic acids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationship of intestinal histology with the resistance to Trichostrongylus colubriformis infection in three breeds of sheep

Avaliaram-se a associação entre o número de células inflamatórias no intestino delgado e a resistência à infecção por Trichostrongylus colubriformis em ovinos de três raças (Santa Inês, Suffolk e Ile de France), naturalmente infectados. Mastócitos, eosinófilos e leucócitos globulares foram quantificados na mucosa intestinal. A concentração de histamina foi estimada em amostras teciduais do intestino, bem como foi determinado o comprimento de machos e fêmeas de T. colubriformis. A resposta celular foi similar na mucosa intestinal das três raças ovinas (P>0,05). Houve grande variação entre os ovinos em relação aos resultados parasitológicos e celulares, mesmo nos animais de mesma raça. em geral, os animais que apresentaram número menor de células inflamatórias tiveram cargas parasitárias maiores, contagens de ovos por grama de fezes mais altas e exemplares de T. colubriformis maiores. Os resultados indicaram que mastócitos, eosinófilos e leucócitos globulares prejudicaram o estabelecimento, o desenvolvimento e a sobrevivência dos parasitas.

Prevalence of dog intestinal parasites and risk perception of zoonotic infection by dog owners in São Paulo State, Brazil

Coprological examination was used to estimate the prevalence of gastrointestinal parasites in stray and domiciled dogs from Botucatu, São Paulo State, Brazil. Risk factors for dog infection were assessed in relation to demographic, husbandry and management data. The dog owners completed a questionnaire survey on some aspects of dog parasitism such as parasite species, mechanisms of infection, awareness of zoonotic diseases and history of anthelmintic usage. Parasites were found in the faeces of 138 dogs, with an overall prevalence of 54.3%. Dogs harbouring one parasite were more common (31.4%) than those harbouring two (18.5%), three (3.2%) or four (1.2%). The following parasites and their respective frequencies were detected: Ancylostoma (37.8%), Giardia (16.9%), Toxocara canis (8.7%), Trichuris vulpis (7.1%), Dipylidium caninum (2.4%), Isospora (3.5%), Cryptosporidium (3.1%) and Sarcocystis (2.7%). Stray dogs were found more likely to be poliparasitized (P < 0.01) and presented higher prevalence of Ancylostoma, T. canis and Giardia (P < 0.01) than domiciled ones. Toxocara canis was detected more frequently in dogs with < 6 months of age (P < 0.05) and no effect of sex or breed could be observed (P > 0.05). Except for Ancylostoma, that showed a significantly higher prevalence in dogs living in a multi-dog household (P < 0.01), parasite prevalences were similar in single- and multi-dog household. The answers of dog owners to the questionnaire showed that the majority does not know the species of dog intestinal parasites, the mechanisms of transmission, the risk factors for zoonotic infections, and specific prophylactic measures. The predominance of zoonotic species in dogs in the studied region, associated with the elevated degree of misinformation of the owners, indicates that the risk of zoonotic infection by canine intestinal parasite may be high, even in one of the most developed regions of Brazil.

EFFECTS OF PROTEIN-DEFICIENCY AND NATURAL INTESTINAL INFECTION WITH GIARDIA-LAMBLIA ON JEJUNAL INTRAEPITHELIAL LYMPHOCYTES IN RATS OF DIFFERENT AGES

1. The interaction between experimental protein deprivation and natural intestinal infection by Giardia lamblia was studied in terms of its effects on the intraepithelial lymphocyte (IEL) population and morphology of the jejunal mucosa of rats of different ages.2. Young, adult and old male Wistar rats received a protein-deficient diet (2% casein) or a control diet (20% casein) for 42 days. Mucosal height and the number of lymphocytes located among 500 consecutive epithelial cells (EC) along the villi or crossing the basement membrane were determined in PAS-stained jejunal fragments.3. The number of IEL increased progressively with animal age, from 14 to 25 per 100 epithelial cells, with significant differences between age ranges. However, the number of IEL did not differ between control and protein-deficient rats in any of the age groups. The proportion of lymphocytes crossing the basement membrane was approximately two-fold greater in young (2.8/100 EC) and adult (5.8/100 EC) protein-deficient animals than in their respective controls (1.6 and 2.8/100 EC). The intensity of parasite colonization was moderate, from 3 to 5/100 EC and did not differ between groups. The pattern of morphologic changes of jejunal mucosa in protozoal infection did not differ between control and protein-deficient animals in any of the three age groups.4. We conclude that intestinal infection with Giardia lamblia probably stimulated the local immune response, masking the reduction of the IEL population induced by protein deficiency. The increase in lymphocyte numbers with age may be related to prolonged antigenic stimulation promoted by infection.