Adoptive transfer of the intestinal mast cell response in rats infected with Nippostrongylus brasiliensis.

The intestinal mast cells (IMC) were examined in normal and adoptively immunized rats infected with Nippostrongylus brasiliensis. An increase in the numbers of IMC was observed in infected recipients of thoracic duct lymphocytes (TDL) obtained from donor rats which had themselves been infected 10 days previously (Day 10 TDL). The increase in the number of IMC in the mucosa was related to the number of Day 10 TDL transferred into infected recipients. When TDL were fractionated into populations of cells either bearing (sIg⁺) or lacking (sIg^?) surface immunoglobulin, only sIg^? cells were able to confer the IMC response. Antigenic stimulation was necessary for the differentiation of intestinal mast cells. There was a marked difference between different strains of rats with regard to worm burden and intestinal mast cell kinetics although the increase in intestinal mast cells was always closely related to the final stage of the rapid phase of worm expulsion. These results are compatible with the concept that intestinal mast cells are derived from T cells and suggest that sIg⁺ cells do not influence IMC differentiation. Alternatively, the possibility that the transferred TDL regulate the differentiation of cells of host origin into IMC cannot be excluded.     

The influence of Trypanosoma brucei infection on local immunoglobulin responses of rats to Nippostrongylus brasiliensis

Wedrychowicz H., Maclean J. M. and Holmes P. H., 1984. The influence of Trypanosoma brucei infection on local immunoglobulin responses of rats to Nippostrongylus brasiliensis. International Journalfor Parasitology14: 453–458. Serum, intestinal and lung immunoglobulin and antibody isotype responses to Nippostrongylus brasiliensis infection were studied in normal and trypanosome-infected Hooded Lister rats. Rats which received trypanosomes 7 days before N. brasiliensis infection had impaired responses of serum IgG and IgA. Bronchial and intestinal mucosal IgG was not reduced whilst IgA concentration in these sites was markedly diminished. Total immunoglobulin M levels in T. brucei parasitised rats were higher in both sera and mucosal sites. However, tests with radiolabelled adult nematode excretory-secretory antigens indicated that specific lung and intestinal IgM responses were reduced. Immunoglobulin A antibody responses were diminished most markedly in sera and lungs and also in the intestine while IgG antibodies were decreased in sera and intestine mucosae T. brucei infected rats had higher worm burdens than rats infected with N. brasiliensis alone but worm expulsion was not delayed. The results indicate that local as well as systemic antibody responses are reduced in trypanosome infected animals.     

Egg Laying Capacity of Haplorchis taichui (Digenea: Heterophyidae) in Humans

Quantitative fecal egg counts represented as the number of eggs per gram of feces (EPG) are generally a reliable parameter to estimate the worm burden of intestinal and hepatic parasitoses. Although Haplorchis taichui (Digenea: Heterophyidae) is one of the most common minute human intestinal flukes, little is known about the relationship between EPG and the actual worm burden in patients or the severity of the disease. In the present study, fecal samples were collected from 25 villagers in northern Thailand before and after praziquantel treatment. The EPG values of each participant were determined by the modified cellophane thick smear method, and adult worms were collected from the whole stool after the treatment. Eggs per day per worm (EPDPW) of H. taichui were estimated 82 from egg counts and expelled worms. The EPG was not well correlated with the worm burden, and a reverse correlation was observed between the EPDPW and the worm burden.     

IL-6 is required for protective immune responses against early filarial infection

IL-6 has a wide range of biological activities that includes anti- and pro-inflammatory aspects. In this study, we investigated the role of IL-6 in immune responses to the rodent filarial nematode Litomosoides sigmodontis, a model for human filarial infections. IL-6^?/? mice had a significantly increased worm burden after natural infection compared with wild type controls at early time points p.i. Given that the worm burden in IL-6^?/? mice was already increased at the time point the infective larvae reached the pleural cavity, immune responses that may facilitate the migration from the site of infection (skin) via the lymphatics to the pleural cavity were analysed. Increased vascular permeability may facilitate larval migration, but blocking of histamine receptors had no effect on worm burden and vascular permeability was similar between IL-6^?/? mice and wild type controls. In contrast, blocking mast cell degranulation reduced the worm burden in IL-6^?/? mice partially, suggesting that release of mast cell-derived mediators improves larval migration to some degree. Protective immune responses within the skin were involved, as bypassing the skin barrier by inoculating infective L3s subcutaneously resulted in a comparable worm recovery in both mouse strains. Analysis of the cellular composition by flow cytometry and PCR array in the skin after exposure to filarial extract or L3s, respectively, indicate that the absence of IL-6 results in a delayed recruitment of neutrophils and macrophages to the site of initial infection. These results demonstrate that IL-6 is essentially involved in protective immune responses within the skin that impair migration of infective L3s.     

The phospholipase B content of the intestines of rats infected with varied larvae doses of Nippostrongylus brasiliensis.

Phospholipase B activity, bone marrow eosinophilia and worm burden were measured in separate groups of rats that received initial infections of 100, 400, 800, 1200, 2400, and 4800 Nippostrongylus brasiliensis larvae. The results indicated that as the numbers of larvae in the inocula were increased, the resulting higher worm burdens caused the development of earlier and more intense bone marrow eosinophilias and earlier and greater phospholipase B activities. The expulsion of the adult worms from the host was followed by equally rapid decreases in bone marrow eosinophilia and enzyme activity. It was found that as the number of intestinal adult worms was increased from low to large numbers, the degree of the inflammatory response changed from mild to severe. This suggests that the inflammatory response was responsible for the elevated phospholipase B levels.     

The phospholipase B content of the intestines of sensitized rats challenged with varied larvae doses of Nippostrongylus brasiliensis.

The effects of challenging previously infected (sensitized) groups of rats with 25, 100 and 400 Nippostrongylus brasiliensis larvae on the relation between phospholipase B activity, bone marrow eosinophilia and worm burden were studied. The results indicated that the immune expulsion of worms from sensitized rats was temporally related to an increased phospholipase B activity and bone marrow eosinophilia. All three parameters demonstrated an anamnestic-type of response in the previously infected rats when compared to the infected control animals. The results also demonstrated that the size of the worm burden influenced the induction and concentration of phospholipase B and the numbers of bone marrow eosinophilis.     

Nippostrongylus brasiliensis: intestinal goblet-cell response in adoptively immunized rats.

Goblet-cell differentiation was studied in the intestinal epithelium of rats infected with the nematode Nippostrongylus brasiliensis. An increase in the proportion of goblet cells occurred at the time of worm expulsion in rats infected with 1000 or 4000 third stage larvae. Adoptive immunization of infected rats with immune-thoracic duct lymphocytes (TDL) induced extensive goblet-cell differentiation whereas the transfer of immune-TDL into normal rats had no effect. The extent of goblet-cell differentiation in adoptively immunized infected rats was proportional to the number of cells transferred. A goblet-cell response also occurred in adoptively immunized rats harboring implanted “normal” and “damaged” worms but recipients of normal worms which were not given cells were unable either to expel their worm burden or to induce a goblet-cell response. Experiments in which the parasites were expelled with an anthelmintic drug suggested that the goblet-cell increase was not simply a repair process associated with the expulsion of the parasites. In all situations where immune expulsion of the parasites occurred, there was a concomitant rise in the proportion of goblet cells. These experiments suggest that thoracic duct lymphocytes either directly or indirectly regulate the differentiation of intestinal goblet cells.     

Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni

Knopf P. M. and Soliman M. 1980. Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni. International Journal for Parasitology, 10: 197–204. The capacity of Schistosoma mansoni to complete its life cycle was compared in CD-1 mice (permissive hosts) and Sprague-Dawley rats (nonpermissive hosts) from which the pituitary gland had been removed prior to infection with cercariae. Except for a modest decrease in egg burden, none of the parameters of worm life cycle assessed were affected in hypophysectomized mice. In contrast, all these parameters were affected in hypophysectomized rats, e.g. onset of adult worm elimination was delayed, worm development improved, oviposition increased and miracidia developed. Effects of removal from rats of the thyroid/parathyroid glands on the parasite life cycle were similar to hypophysectomy; adrenalectomy or gonadectomy were without affect. Differences between thyroidectomized and thymectomized rats are discussed. It is concluded that host hormones contribute to the nonpermissive status of rats to Schistosoma mansoni infections.     

Strongyloides ratti: in vitro and in vivo activity of tribendimidine

Background

Strongyloidiasis is a truly neglected tropical disease, but its public health significance is far from being negligible. At present, only a few drugs are available for the treatment and control of strongyloidiasis.

Methodology/Principal Findings

We investigated the activity of tribendimidine against third-stage larvae (L₃) of Strongyloides ratti in vitro and against juvenile and adult stages of the parasite in vivo. S. ratti larvae incubated in PBS buffer containing 10–100 µg/ml tribendimidine died within 24 hours. A single 50 mg/kg oral dose of tribendimidine administered to rats infected with 1-day-old S. ratti showed no effect. The same dose administered to rats harboring a 2-day-old infection showed a moderate reduction of the intestinal parasite load. Three days post-exposure a significant reduction of the immature worm burden was found. Administration of tribendimidine at doses of 50 mg/kg and above to rats harboring mature S. ratti resulted in a complete elimination of the larval and adult worm burden. For comparison, we also administered ivermectin at a single 0.5 mg/kg oral dose to rats infected with adult S. ratti and found a 90% reduction of larvae and a 100% reduction of adult worms.

Conclusion/Significance

Tribendimidine exhibits activity against S. ratti in vitro and in vivo. The effect of tribendimidine in humans infected with S. stercoralis should be assessed.     

Hymenolepis diminuta: effect on the oxidation-reduction potential in the mammalian gastrointestinal canal.

The oxidation-reduction potential (Eh) of the small intestine of uninfected and parasitized (ten 16-day-old Hymenolepis diminuta) rats has been determined under three different types of experimental conditions. On an ad lib. feeding regime at 10.00 hr there were highly significant (P < 0.001) differences between the intestinal Eh of uninfected and parasitized rats in every region of the small intestine. While the entire uninfected gut displayed relatively strong reducing tendencies (?28 to ?195 mV), in the parasitized gut the Eh was predominantly positive (+75 to ?76 mV) and reflected worm biomass distribution. Changes in intestinal Eh were also measured over a period of 6 hr after the feeding of a 1-g glucose meal. The Eh in uninfected animals increased from ?232 to +118 mV; in parasitized animals from ?31 to +189 mV. While the changes were greater in the former group, those of the latter reflected the changing worm biomass distribution. The most positive regional Eh value was always associated with the maximum % worm biomass distribution. Third, using surgical intestinal-loop preparations there were significantly (P < 0.05) higher positive Eh values in parasitized (+185 mV) than in uninfected (+128 mV) rats; in both animal groups the Eh of the duodenal-jejunal loops were more positive than that of the ileal loops (P < 0.05).The results are discussed in terms of the close inter-relationship between intestinal pH, Eh, the microflora and luminal pO₂ tensions.     

Increased Intestinal Epithelial Cell Turnover and Intestinal Motility in Gymnophalloides seoi-Infected C57BL/6 Mice

The changing patterns of goblet cell hyperplasia, intestinal epithelial cell turnover, and intestinal motility were studied in ICR and C57BL/6 mice infected with Gymnophalloides seoi (Digenea: Gymnophallidae). Whereas ICR mice retained G. seoi worms until day 7 post-infection (PI), C57BL/6 mice showed a rapid worm expulsion within day 3 PI. Immunosuppression with Depo-Medrol significantly delayed the worm expulsion in C57BL/6 mice. Goblet cell counts were increased in both strains of mice, peaking at day 1 PI in C57BL/6 mice and slowly increasing until day 7 PI in ICR mice. In C57BL/6 mice infected with G. seoi, newly proliferating intestinal epithelial cells were remarkably increased in the crypt, and the increase was the highest at day 1 PI. However, in ICR mice, newly proliferating intestinal epithelial cells increased slowly from day 1 to day 7 PI. Intestinal motility was increased in G. seoi-infected mice, and its chronological pattern was highly correlated with the worm load in both strains of mice. Meanwhile, immunosuppression of C57BL/6 mice abrogated the goblet cell proliferation, reduced the epithelial cell proliferation, and suppressed the intestinal motility. Goblet cell hyperplasia, increased intestinal epithelial cell turnover, and increased intestinal motility should be important mucosal defense mechanisms in G. seoi-infected C57BL/6 mice.     

Trickle infections with Nippostrongylus brasiliensis in rats: larval migration through the lungs

The effects of exposure of rats to repeated low-level (trickle) infections with Nippostrongylus brasiliensis were assessed by measuring intestinal and lung worm burdens. Worm recoveries from the intestine, made during a period of trickle infection in rats of different ages, showed a virtually complete rejection of intestinal worms in old rats and a partial rejection in young rats. Recoveries from lungs were made in young rats after challenge infection with 500 third-stage (L3) larvae, given after a 2- or 4-wk period of sensitization, during which rats were infected with 10 or 20 doses of 25 larvae. Such trickle infections elicited a strong host response to a challenge infection, manifested by low recoveries of larvae and an increased duration of larval retention in lungs. In another group of rats sensitized by a single dose of 250 L3 larvae, the recovery of larvae from challenge infection and their clearance from the lungs were similar to these observed in rats uninfected prior to challenge. The effect of trickle infections on preintestinal stages was most pronounced and consistent in rats exposed to larvae the greater numbers of times and over the longest period.     

Strongyloides ratti: Mast cell and goblet cell responses in the small intestine of infected rats

Kinetics of intestinal mast cells and goblet cells were examined in relation to worm localization at various sites in the small intestine of rats infected with 3000 filariform (stage 3) larvae of Strongyloides ratti. The most marked intestinal mastocytosis was observed on Day 20 at the anterior site of the small intestine where the majority of the worms had concentrated. The number of mast cells in the posterior small intestine increased in parallel with the posterior shift of parasites at the later stage of the infection. In contrast to the intestinal mast cell response, the number of goblet cells was not significantly affected by the infection. These results strongly suggest that intestinal mastocytosis is closely related to the presence of the worms and that mast cells may play an important role for the expulsion of S. ratti.     

Rapid and specific alterations of goblet cell mucin in rat airway and small intestine associated with resistance against Nippostrongylus brasiliensis reinfection

The intestinal parasitic nematode Nippostrongylus brasiliensis is expelled rapidly from the rat in reinfection challenge compared with that of the primary infection owing to the host defense mechanisms raised against the pre-intestinal- and intestinal-stage larvae. We examined the relationship between the mucin alterations in airway and jejunal mucosae and the worm expulsion after third-stage larva reinfection. When rats had been inoculated with fourth-stage larvae and immunized with only the intestinal-stage worms for more than 8 days, the challenge larvae were expelled during the intestinal stage along with a rapid increase of the specific sialomucin in jejunal mucosa, without any effect on the bronchial mucus. When rats had been infected with third-stage larvae and immunized with only the pre-intestinal stage larvae by killing with antihelminthic, the challenge larvae were rejected during the pre-intestinal stage along with marked goblet cell hyperplasia and Muc5AC mucin hyperproduction on the bronchial mucosa, but not as a result of jejunal mucin alteration. Taking these finding together, immunization with pre-intestinal- and intestinal-stage worms independently increases the airway and intestinal goblet cell mucins, respectively, and in both cases, the mucin alterations may contribute to rapid worm expulsion upon reinfection.     

Comparison of rapid expulsion of Trichinella spiralis in mice and rats

Alizadeh H. and Wakelin D. 1982. Comparison of rapid expulsion of Trichinella spiralis in mice and rats. International Journal for Parasitology12: 65–73. Primary infections of Tricliinella spiralis in both NIH mice and Wistar rats resulted in increased levels of mucosal mast cells and goblet cells. In mice the numbers of both cell types rose sharply before worm expulsion (days 8–10), remained at an increased level for a short time and declined quickly, reaching control levels on day 14 for goblet cells and between days 28 and 35 for mast cells. In contrast, in rats, the numbers of goblet cells and mast cells increased during worm expulsion and remained above control levels for a prolonged period. Challenge infections given shortly after expulsion of a primary infection (day 14) were expelled rapidly, worm loss being virtually complete with 24 h. In mice this response to challenge was short-lived and persisted only until day 16 after primary infection. After this time, challenge worms were expelled more slowly after infection. In rats the rapid expulsion response was expressed for at least 7 weeks after primary infection. Mice and rats showed differences in the conditions of infection necessary to prime for rapid expulsion, mice requiring larger and longer duration primary infections, but the expression of the response appeared to be similar in both species. In mice it was shown that rapid expulsion of T. spiralis was a response evoked specifically by prior infection with this species; infections with other intestinal nematodes had no effect. Similarly, the effect upon challenge infection was also specific to T. spiralis. The rapidity with which challenge infections are expelled suggests that either the specific inflammatory changes generated during primary infection result in an environment that is unsuitable for establishment of subsequent infections or that challenge infections provide a stimulus that can provoke an almost instantaneous response in the primed intestine. The relationship of the observed cellular changes to such mechanisms is discussed.     

Increased Enterocyte Production in Gnotobiotic Rats Mono-Associated with Lactobacillus rhamnosus GG

There is increasing scientific and commercial interest in using beneficial microorganisms (i.e., probiotics) to enhance intestinal health. Of the numerous microbial strains examined, Lactobacillus rhamnosus GG has been most extensively studied. Daily intake of L. rhamnosus GG shortens the course of rotavirus infection by mechanisms that have not been fully elucidated. Comparative studies with germfree and conventional rats have shown that the microbial status of an animal influences the intestinal cell kinetics and morphology. The present study was undertaken to study whether establishment of L. rhamnosus GG as a mono-associate in germfree rats influences intestinal cell kinetics and morphology. L. rhamnosus GG was easily established in germfree rats. After 3 days of mono-association, the rate of mitoses in the upper part of the small intestine (jejunum 1) increased as much as 14 and 22% compared to the rates in germfree and conventional counterparts, respectively. The most striking alteration in morphology was an increase in the number of cells in the villi. We hypothesis that the compartmentalized effects of L. rhamnosus GG may represent a reparative event for the mucosa.     

The effect of a single dose of tumor necrosis factor alpha inhibitor on gut permeability in rats during exposure to a heat stress

Heat stroke is a life threatening illness characterized by a core body temperature of >40 °C, delirium and convulsions, and often results in multi-organ dysfunction, due to the release of endotoxin through the intestinal wall into the circulation. While playing a major role in the gastrointestinal tract permeability changes seen in Crohn's disease, it is not clear whether tumor necrosis factor alpha (TNF-α) mediates the increase in intestinal permeability and the release of endotoxin into the circulation in heat stroke. The aim of the present study was to determine the acute effects of a single dose of TNF-α antibody on gut permeability in rats during heat stress. Fifty-five Sprague-Dawley rats (28 male and 27 female) were treated with either saline or infliximab (a monoclonal antibody to TNF-α), anesthetized with pentobarbitone (50 mg kg⁻¹) and then exposed to either normothermic conditions or an ambient temperature of between 41 and 42 °C for 70 min. Fluorescent isothiocyanate labeled dextrans (FITC-dextrans) were administered intragastrically as a marker of intestinal permeability. Liver enzymes, endotoxin and TNF-α were analyzed in the blood. Exposure to a heat stress significantly increased intestinal permeability to FITC-dextrans compared to the controls (P<0.05). Infliximab did not have an effect on the intestinal permeability to the FITC-dextrans. Heat stress had no significant effect on liver enzymes or endotoxin concentration versus controls (P>0.05). TNF-α was not detectable in any of the samples. TNF-α did not mediate the release of endotoxin into the circulation after an acute bout of heat stroke.     

Schistosoma mansoni and Fasciola hepatica: Cross-resistance in mice with single-sex schistosome infections

Primary Schistosoma mansoni single-sex infections in mice, i.e., either male only or female only, did not stimulate any detectable level of heterologous resistance to challenge with Fasciola hepatica after 22 to 76 days, while statistically significant resistance to a challenge with F. hepatica was demonstrated in the presence of patent mixed-sex S. mansoni infections. Simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction in the number of schisto-some worms established, i.e., the burden being reduced by 40.1 and 43.9%, respectively. There was no reduction of the F. hepatica worm burden. Similar features could be observed with a time interval of 48 hr between the S. mansoni infection and the F. hepatica challenge, i.e., the schistosome burden being reduced by 34.2 and 45.6%, respectively. Furthermore, simultaneous infections with S. mansoni and F. hepatica induced a statistically significant reduction of the egg production capacity per paired female schistosome worm as compared with that of the S. mansoni control group. Tissue egg counts of the various intestinal sections were reduced by 92.8–99.6%.     

Nematoda: Aerobic respiratory pathways of adult parasitic species

Aerobic respiratory pathways have been compared in adult parasitic nematodes, including Trichostrongylus colubriformis, Nippostrongylus brasiliensis, Ostertagia ostertagi, Cooperia oncophora, Haemonchus contortus, Oesophagostomum venulosum, Chabertia ovina, Dictyocaulus filaria, Dictyocaulus viviparus, and Ascaridia galli. Respiration was measured in both whole worm or tissue homogenates and isolated mitochondrial fractions, and delineated into the mammalian type or alternative respiratory pathways on the basis of their inhibition by antimycin A. The alternative, antimycin A-insensitive respiratory pathway was of comparable activity in all parasitic nematodes studied, irrespective of the body diameter or habitat of the worm. The mammalian-type, antimycin A-sensitive respiratory pathway showed variations; the extent of this pathway correlated with both the body diameter and habitat of the worm, being greater in thinner worms and those worms whose habitat is supposedly more aerobic.     

The magnitude of physical exercise-induced hyperthermia is associated with changes in the intestinal permeability and expression of tight junction genes in rats

We investigated whether the magnitude of exercise-induced hyperthermia influences intestinal permeability and tight junction gene expression. Twenty-nine male Wistar rats were divided into four groups: rest at 24 °C and exercise at 13 °C, 24 °C or 31 °C. The exercise consisted of a 90-min treadmill run at 15 m/min, and different ambient temperatures were used to produce distinct levels of exercise-induced hyperthermia. Before the experimental trials, the rats were treated by gavage with diethylenetriaminepentaacetic acid labeled with technetium-99 metastable as a radioactive probe. The rats' core body temperature (T_CORE) was measured by telemetry. Immediately after the trials, the rats were euthanized, and the intestinal permeability was assessed by measuring the radioactivity of blood samples. The mRNA levels of occludin and zonula occludens-1 (ZO-1) genes were determined in duodenum samples. Exercise at 24 °C increased T_CORE to values close to 39 °C, without changing permeability compared with the resting trial at the same environment. Meanwhile, rats’ T_CORE exceeded 40 °C during exercise at 31 °C, leading to greater permeability relative to those observed after exercise in the other ambient temperatures (e.g., 0.0037%/g at 31 °C vs. 0.0005%/g at 13 °C; data expressed as medians; p < 0.05). Likewise, the rats exercised at 31 °C exhibited higher mRNA levels of ZO-1 and occludin genes than the rats exercised at 24 °C or 13 °C. The changes in permeability and gene expression were positively and significantly associated with the magnitude of hyperthermia. We conclude that marked hyperthermia caused by exercise in the warmer environment increases intestinal permeability and mRNA levels of tight junction genes.