Helminth-induced intestinal inflammation

Structural relationships between immune cells and longitudinal muscle during a Trichinella spiralis infection in the rat intestine

A Trichinella spiralis infection produces an acute inflammatory reaction and tissue damage in the mucosa, and, in addition, functional changes occur in the external muscle layers. The aim of the present study was to characterize structural changes in the musculature that occur during early infection, and to identify relationships between immune cells and muscle cells, as part of an ongoing investigation into the immune modulation of motor function in the gut. Rats were infected with T. spiralis larvae and the gut fixed at 12 h, 24 h, 48 h and 6 days post-infection for electron microscopy of the longitudinal muscle. Macrophages and lymphocytes penetrated the longitudinal musculature 12-24 h post-infection. Distinct contacts were observed between specific cell types; cellular protrusions from macrophages or lymphocytes made close apposition contacts with smooth muscle cells. Resident macrophages in the subserosal space, fibroblast-like cells as well as smooth muscle cells showed marked activation during inflammation. Fibroblast-like cells were frequently seen intercalated between lymphocytes and smooth muscle cells, hence they may mediate communication between immune cells and the musculature.

Pathology of infection with Paramphistomum ichikawai in sheep

Lambs were given 40,000 or 50,000 metacercariae of Paramphistomum ichikawai by injection into the rumen and necropsied at 21, 42 and 84 days after infection. Pathological changes were observed grossly and confirmed histologically in the small intestine and rumen. The numbers of flukes and their location in the gastrointestinal tract were recorded and the populations of eosinophils, mast cells and globule leucocytes estimated. Changes varied, according to the numbers of flukes present, from a localised enteritis and villous atrophy in the duodenum in light infections to severe destruction of the mucosa extending into most of the jejunum in heavy infections. As the infection progressed changes were characterised by extensive thickening and fibroplasia in the mucosa and submucosa. Severe damage to the mucosa of the rumen was also observed in heavy infections. Heavy infections were associated with increased infiltration with eosinophils. Mast cells were generally depleted and globule leucocytes only appeared after the flukes had left the small intestine. Migration of the flukes from the small intestine was delayed in heavy infections exacerbating the effect of the infection. It is suggested that the presence of 20,000 to 25,000 flukes would result in clinical disease; smaller numbers would cause significant subclinical disease.

Expression of cytokines in the longitudinal muscle myenteric plexus of the inflamed intestine of rat

BACKGROUND/AIMS

Trichinella spiralis infection in the rat produces mucosal injury and inflammation and causes changes in muscle function and neurotransmitter release in the longitudinal muscle myenteric plexus (LMMP). Whether these changes in LMMP reflect the production of inflammatory mediators in the LMMP remains unknown. The objective of this study was to investigate the profile of interleukins (IL) 1-alpha, 1-beta, and 6 and tumor necrosis factor (TNF) alpha in the LMMP of infected rats. Because muscle changes are T-cell dependent, we also studied the cytokine profile in infected athymic rats.

METHODS

Cytokine messenger RNA (mRNA) was examined using semiquantitative polymerase chain reaction, and protein was measured by enzyme-linked immunosorbent assay, radioimmunoassay, or bioassay.

RESULTS

There was increased expression of IL1-alpha and -beta, IL-6, and TNF-alpha mRNA and protein in the LMMP of both euthymic and athymic infected rats. Increased expression of each cytokine was observed by 24 hours postinfection and, in the case of IL1-beta and TNF-alpha, remained elevated by day 6 postinfection.

CONCLUSIONS

Mucosal injury following T. spiralis infection is accompanied by enhanced expression of proinflammatory cytokines in the LMMP. The expression of IL1-, IL-6, and TNF-alpha in infected athymic rats suggests that these cytokines do not contribute to the changes in muscle growth or contraction but may mediate the previously described changes in neurotransmitter release in this model.

Local eosinophil- and mast cell-related responses in abomasal nematode infections of lambs

Eosinophil numbers in peripheral blood and eosinophil potentiating activity (EPA) and sheep mast cell protease (SMCP) in efferent gastric lymph were monitored in lambs during infections with Ostertagia circumcincta. Worm burdens, eosinophil numbers in bone marrow, abomasal mucosa and gastric lymph node, as well as mast cell numbers and SMCP concentrations in mucosa and mucus, were determined in post mortem samples. In naive lambs, high and relatively uniform worm burdens were present 10 days after primary infection and these were associated with only mild blood and tissue eosinophilia. By day 21 worm burdens were markedly lower and more variable. There was more evidence of eosinophil and mast cell accumulation in mucosa, and numbers in bone marrow were also higher than on day 10. However, neither EPA nor SMCP were detectable in lymph. By contrast, EPA and SMCP were present in substantial amounts in draining lymph within 48 h of challenge (secondary) infection of previously exposed lambs. EPA was inversely related to worm burdens recovered on day 10, as were abomasal mucosal and mucus SMCP concentrations. Elevated eosinophil numbers were also consistently detected in blood, bone marrow, mucosa and gastric lymph node. The results suggest that host immune defence against secondary, but not primary, exposure to O. circumcincta involves a rapidly mobilised local inflammatory component.

Infection course of the strobilar stage of Taenia crassiceps in golden hamsters, with reference to host responses

The time course of intestinal infection of golden hamsters (Mesocricetus auratus) with Taenia crassiceps was monitored every 2 days up to day 26 postinfection (p.i.). The isolate used was originally obtained from Clethrionomys rutilus on St. Lawrence Island, Bering Sea (USA), and shows a high level of enteral establishment without parenteral infection. Following oral administration of various numbers (3, 15, 30, or 60) of metacestodes, proportional numbers of cestodes attached their scolices to the mucosa of the middle (one-third) segment of the small intestine. Except for animals given 3 metacestodes, dislocation of cestodes to the posterior parts of the intestine was noted on days 10-14 p.i. and began faster in animals that had received larger numbers of metacestodes. Concurrent with dislocation or elimination of cestodes, there existed distinct increases in intestinal eosinophil peroxidase and myeloperoxidase activities. The number of mast cells in the lamina propria peaked on day 16 p.i., and specific serum IgG began to increase within 1 week p.i. The level of all these changes was dose-dependent. In prednisolone-treated animals that received 60 metacestodes, dislocation of cestodes was not evident, and mucosal inflammatory changes were suppressed to a considerable extent. The findings of this study are discussed as a model for the study of canine taeniasis.

Ascaris reinfection of slum children: relation with the IgE response

Total and Ascaris-specific serum IgE levels were measured in a group of 98 Ascaris-infected children from a slum area of Caracas, Venezuela, in whom the infections were eliminated by regular treatment for 22 months with the anthelmint Oxantel/Pyrantel ('Quantrel'). The children were re-evaluated at the end of the treatment programme, and then 8 months later, at which time reinfection was assessed. Total IgE levels at the beginning of the study were significantly higher in the children who became reinfected after treatment, compared with those who did not. The anthelmint treatment caused a significant decrease in the total IgE levels in most of the children, and after a period of 8 months without treatment these continued to decrease in the non-reinfected group, but increased again in the reinfected children. The reverse pattern was found for Ascaris-specific IgE antibody levels, and in fact an inverse correlation was found between total and anti-Ascaris IgE levels. Striking associations were found between reinfection and high pretreatment values of total IgE, but low levels of specific IgE antibody. These data support the concept that specific IgE antibody may participate in the protection against helminthic infection, and suggest that the polyclonal stimulation of IgE synthesis caused by these parasites may reduce the effectiveness of such responses. The results also indicate that different individuals have varying propensities to respond polyclonally to the helminths, and this influences their resistance to infection.

Relationship between the degree of poverty and the IgE response to Ascaris infection in slum children

We examined a group of urban slum children in Caracas, Venezuela, and demonstrated the relationship that exists between poverty, conditions of hygiene and the prevalence of helminth infection. Concordant with the high prevalence of helminth infection in these children, the total serum levels of immunoglobulin E (IgE) and blood eosinophilia were elevated and were directly related to the degree of poverty and lack of sanitary facilities. However, in contrast, the reverse pattern was observed for the specific allergic response to these parasites. Thus, the immediate hypersensitivity skin test reactivity to Ascaris antigens, and the serum levels of specific anti-Ascaris IgE antibody, were lowest in the poorest children, who had the highest prevalence of helminth infection and the highest total IgE levels. As allergic-type reactions may participate in protective mechanisms against helminths, these results suggest that poverty and poor sanitary conditions may, by influencing the IgE response, compromise the resistance of such children to parasitic infections.

Neutrophil recruitment to the gastrointestinal tract

The infiltration of an organ or tissue by neutrophils is the hallmark of acute inflammation. Recent work from many laboratories suggests that neutrophils may play a role in the development of tissue injury in a variety of disease states in the gastrointestinal tract. These diseases include gastritis, necrotizing enterocolitis, ileitis, ulcerative colitis, and ischemia reperfusion injuries. In view of this recent interest in the neutrophil and its relationship to GI diseases, it seems timely to review what is known about neutrophil recruitment to the gastrointestinal tract. This review will therefore focus on the sojourn of the neutrophil from the circulation to its destination in the GI tract.

Increased levels of substance P in the myenteric plexus of Trichinella-infected rats

Changes in immunoreactive substance P concentrations were investigated in longitudinal muscle-myenteric plexus preparations from the inflamed jejunum of Trichinella spiralis-infected rats. The substance P concentration increased within 2 days of infection and increased fivefold by day 6; in contrast, there was no significant increase in substance P in the noninflamed ileum. In vitro exposure of preparations from infected rats to scorpion venom reduced substance P levels by 88%. In addition, no increase in substance P was observed in rats that had been treated with capsaicin as neonates or as adults before infection. Treatment of infected rats with betamethasone attenuated the inflammatory response to the infection and prevented the increase in substance P. Furthermore, no significant increase in substance P concentration was seen in congenitally athymic rats infected with T. spiralis. This study is consistent with the hypothesis that inflammation increases substance P in myenteric nerves by a process that involves T lymphocytes.

Impaired sympathetic nerve function in the inflamed rat intestine

The effect of intestinal inflammation on norepinephrine release from the myenteric plexus in the Trichinella spiralis-infected rat was assessed. Longitudinal muscle-myenteric plexus preparations were preincubated with [3H]norepinephrine and release was evoked by electrical field stimulation and KCl administration. Preincubation of preparations with desipramine or pretreatment of rats with 6-hydroxydopamine significantly suppressed the uptake and evoked release of [3H]norepinephrine; electrical field stimulation but not KCl-evoked release of [3H] norepinephrine was sensitive to tetrodotoxin. These results confirm the presence of functioning sympathetic nerves in the preparations. T. spiralis infection was associated with significant suppression of both electrical field stimulation and KCl-evoked release of [3H]norepinephrine on the sixth day postinfection, and the suppression persisted 100 days postinfection. No suppression of [3H]norepinephrine release was seen in the worm-free and noninflamed ileum of infected rats. Suppression of [3H]norepinephrine release from the jejunum of infected rats was attenuated by treatment with betamethasone (3.0 mg/kg SC daily). These results are consistent with the hypothesis that intestinal inflammation suppresses the release of norepinephrine from the myenteric plexus in the Trichinella-infected rat.

Trixacarus caviae infection of guinea pigs with genetically determined differences in susceptibility to Trichostrongylus colubriformis infection

Guinea pigs with genetically determined resistance or susceptibility to infection with the nematode parasite Trichostrongylus colubriformis were allowed to become infected with the sarcoptid mite Trixacarus caviae. Compared with nematode-susceptible guinea pigs, nematode-resistant animals had larger populations of mites and developed a more severe dermatitis, with greater mast cell hyperplasia and many more infiltrating eosinophils. The results suggest that animals bred for resistance to one parasite may have greater susceptibility to other parasites.