The reversibility of intestinal immune expulsion effects on adult Nippostrongylus brasiliensis

An attempt has been made to study the extent and nature of the damage occurring in adult Nippostrongylus brasiliensis undergoing immune expulsion from the rat. It was found that worms are not killed nor irreparably damaged when being rejected. On transfer into naive second recipient rats the rate of re-establishment of worms previously incubated in immune rat recipients for 4-17 hr was high (68-69%) and comparable to that shown by worms from normal recipient rats (48-56%). Similarly, worms taken on days 10, 11, and 12 of a primary infection, already passed to the distal half of the small intestine due to immune expulsion effects, on transfer into naive recipient rats re-established themselves well (rates varying from 62 to 80%) compared to those harvested from their normal habitat in the proximal half of the small intestine (rates varying from 44 to 87%). Worm damage is associated with decreased motility and impaired locomotion capacity. The phenomenon of mucosal trapping occurs during expulsion, but merely to the extent of some 30% of the worm population. It is suggested that in principle, worms subjected to immune expulsion are in a state of acute, transient metabolic crisis. The present results support the enteroallergic indirect mechanism for worm rejection.     

Effects of PGE1 or PGE2 on luteal function in pseudopregnant rats

Effects of PGE1 or PGE2 on luteal function were studied in 163 pseudopregnant rats. PGE1 (10, 100, or 300 micrograms) given intrauterine every 6 hr did not shorten pseudopregnancy (P greater than 0.05), however, the same doses of PGE2 given intrauterine every 6 hr advanced luteolysis (P less than 0.05). PGE1 (100 or 300 micrograms) given every 4 hr intramuscular maintained levels of progesterone in peripheral blood above controls (P less than 0.05) while 100 or 300 micrograms of PGE2 hastened the decline in progesterone (P less than 0.05). The antiluteolytic effect of PGE1 was not via an inhibition of PGF secretion (P greater than 0.05) by the uterus or by induction of ovulation in treated animals. Moreover, PGE1 (100, 200, or 500 micrograms) given intramuscular every 4 hr from day 4 of pseudopregnancy until the next proestrus delayed luteal regression around 3 days (P less than 0.05). PGE2 at doses of 100, 200, or 500 micrograms every 4 hr given intramuscular consistently shortened pseudopregnancy (P less than 0.05). Lower doses were without effect (P greater than 0.05). Based on the above data it is concluded that PGE2 is consistently luteolytic whereas PGE1 is not luteolytic in pseudopregnant rats and that PGE1 may be an antiluteolysin.     

Nippostrongylus brasiliensis: histamine and 5-hydroxytryptamine inhibition and worm expulsion

The daily administration of inhibitors of histamine and 5-hydroxytryptamine to rats infected with Nippostrongylus brasiliensis prevented the onset of the rapid phase of worm expulsion. These findings lend strong support to the importance of amine release and Mast cell discharge in worm expulsion.     

Nippostrongylus brasiliensis: reversibility of reduced-energy status associated with the course of expulsion from the small intestine in rats

Gastrointestinal nematodes require energy for active establishment in the gut against intestinal flow and peristaltic motion. In this study we employed CellTiter-Glo Luminescent Cell Viability Assay to measure the ATP value of individual adult Nippostrongylus brasiliensis during the course of immune-mediated expulsion from the small intestine in rats. The ATP values of adult worms taken from the lumen of the distal small intestine were lower than worms collected from the lumen of the proximal small intestine. Moreover, values from worms in the lumen of the proximal small intestine were lower than those from worms in the mucosa, the preferred site of adult N. brasiliensis. The reduction of ATP values in worms from each region was observed not only at expulsion phase, but also at established phases of the infection suggesting that energy metabolism of the parasites is independent of host immune response. When adult worms with low ATP values on day 12 post-infection were implanted surgically into the small intestine of na?ve rats, the worms re-established in recipients and completely restored the ATP values. Short in vitro culture of adult worms under low oxygen tension resulted in low ATP value in the worms. These results suggested that adult worms were dislodged from their preferred site by intact energy metabolism activity.     

Nippostrongylus brasiliensis infections in mice: the immunological basis of worm expulsion.

Nippostrongylus brasiliensis infections in mice were terminated more rapidly than in rats and immunologically induced damage occurred earlier. Like rats, mice expelled damaged worms more rapidly than normal worms. Recipients of cells from the spleen or mesenteric node of immune mice expelled their worms by day 8 of the infection. Recipients of cells alone or antiserum alone did not expel their worms by day 5 but mice given both cells and antiserum expelled their worms by this stage of the infection. Damaged worms were expelled more rapidly than normal worms from mice given immune cells, This work indicated that antibodies and cells collaborate to expel N. brasiliensis from mice as has been shown to occur in rats.     

Immunologic properties of mast cells from rats infected with Nippostrongylus brasiliensis.

The concentration of IgE in the serum of Sprague-Dawley rats increased after infection with Nippostrongylus brasiliensis (NB). The IgE concentration in normal rats was less than 1 mug/ml. After re-infection with NB, the concentration increased in 100 to 300 mug/ml. Mast cells were purified from peritoneal cells of both normal and NB-infected animals. Purified mast cells from the infected animals released histamine upon exposure to NB antigen. The antibody specific for IgE released histamine from purified mast cells of both normal and infected animals. Dose-reponse curves of histamine release suggested that mast cells from NB-infected animals bear more IgE molecules than normal mast cells. Binding of 125I-labeled rat E myeloma protein with normal mast cells was demonstrated by autoradiography. Under the same experimental conditions, mast cells of infected animals were not labeled with 125I-IgE. Mast cells from both normal and infected animals failed to combine 125I-labeled IgG. The number of IgE molecules bound per mast cell was determined by incubating 125I-labeled IgE with purified mast cells. When mast cells were incubated incubated in 0.6 to 2 mug/ml of IgE, the number of IgE molecules combined with the mast cells from infected animals was about 10% of that bound with normal mast cells. The results indicated that a large proportion of IgE receptors on mast cells of infected animals was occupied by their own IgE. No significant difference was observed between normal mast cells and those of infected animals with respect to histamine content and intracellular levels of cyclic nucleotides.     

Intestinally implanted Nippostrongylus brasiliensis adult worms decrease serum paraoxonase-1 activity in rats

We have previously reported a significant decrease in serum PON1 activity after Nippostrongylus brasiliensis infection in Wistar rats in association with the inflammatory response mounted against the parasite in the migratory phase of infection. However, the roles of intestinal phase and the associated oxidative stress during N. brasiliensis infection on PON1 activity have not yet been elucidated. In the present study, we observed a significant reduction in serum paraoxonase and arylesterase activity on days 6 and 9 post-implantation with N. brasiliensis adult worms in the absence of a significant increase in various serum pro-inflammatory cytokines. In addition, provision of the antioxidant butylated hydroxyanisole (BHA) to adult worm-implanted rats did not ameliorate the reduction in PON1 activity. Due to the prolonged intestinal phase of gastrointestinal nematode infections, alterations in PON1 activity during this phase need to be further examined to elucidate the mechanism of alteration in PON1 activity.     

Nippostrongylus brasiliensis: Effect of cyclophosphamide treatment on worm expulsion in rats

The precise immunological mechanisms associated with expulsion of the gastrointestinal nematode Nippostrongylus brasiliensis remain controversial. In order to investigate the effects of drug-induced immunosuppression on parasite burdens and expulsion, various regimens of cyclophosphamide were administered to parasitized Wistar rats. It was observed that both the number of worms established from an infective dose of 3000 larvae and the time of expulsion were markedly increased with higher doses of cyclophosphamide. Thus, at the highest sublethal level of treatment (100 mg/kg), 82% of the infective dose was recovered at Day 9 postinfection compared with 51% in nontreated controls. Furthermore, in such treated rats expulsion was delayed in 6 days beyond that of nontreated animals. As cyclophosphamide, at the levels used in the present study, is known to primarily effect B-cell function, the results support the view that antibody-mediated responses play an essential role in worm expulsion.     

Physiological responses of rats to primary infection with Nippostrongylus brasiliensis

The physiological responses of well-nourished rats to primary infection with the intestinal nematode Nippostrongylus brasiliensis were examined. Infected rats fed ad libitum were compared with uninfected control rats fed ad lib. and with uninfected rats which were pair-fed to the infected rats. Following infection with N. brasiliensis rat food intake was reduced from day 2 post infection (pi) and there were two periods of minimal food intake (days 2 to 3 and 8 to 9 pi). The water intake of infected rats was only reduced on days 2, 3 and 9 pi and not to the same extent as food intake. Muscle catabolism in infected rats was more severe than could be explained on the basis of their food intake reduction. The rectal temperature and rate of oxygen consumption per g body-weight of rats was not significantly altered by the infection. Host responses to N. brasiliensis are compared with those seen in microbial infections and some of them are found to be considerably different.     

Partial cross-resistance between Strongyloides venezuelensis and Nippostrongylus brasiliensis in rats.

Rats were immunized through an initial infection with 1,000 filariform larvae (L3) of Nippostrongylus brasiliensis and after complete expulsion of worms they were challenged with 1,000 L3 of Strongyloides venezuelensis to investigate whether cross-resistance developed against a heterologous parasite. Nippostrongylus brasiliensis-immunized rats developed a partial cross-resistance against S. venezuelensis migrating larvae (MSL3) in the lungs and adult worms in the small intestine. The population of MSL3 in the lungs were significantly lower (P < 0.05) in immunized rats (22.0 +/- 7.4) compared with controls (105.0 +/- 27.6). The populations of adult worms, egg output and fecundity were initially decreased but from day 14 post-challenge they did not show any significant difference between immunized and control rats. However, the length of worm in immunized rat was revealed as retardation. Peripheral blood eosinophilia was significantly decreased (P < 0.05) on day 7 post-challenge and then gradually increased, which peaked on day 42 post-challenge when most of the worms were expelled. These results suggest that peripheral blood eosinophilia is strongly involved in the worm establishment and expulsion mechanisms.     

Nippostrongylus brasiliensis: physiological and metabolic responses of rats to primary infection

Primary infection of rats with Nippostrongylus brasiliensis was associated with alterations in host protein, carbohydrate and lipid metabolism. Infected rats fed ad libitum were compared with uninfected, weight matched, pair fed rats. Metabolic changes detected were related to the level of infection (larvae/g body weight) and also the time course of development of the parasite. The intestinal stage of the infection was associated with marked catabolism of skeletal muscle which did not appear to be mediated by increased secretion of corticosteroids. Plasma concentrations of protein in infected rats were altered even at the lowest dose (27 l/g), and in a biphasic manner corresponding to larval and adult stages of the parasite. Plasma globulin concentrations were increased on Day 2 after infection while from Days 5-10 after infection, plasma concentrations of both globulin and albumin were much reduced. Hypoglycemia developed on Days 8-9 after infection in rats given a dose of greater than or equal to 39 l/g. Infected rats had increased plasma concentrations of non-esterified fatty acids and in marked contrast with their pair fed partners, plasma triglyceride concentration increased dramatically with both the dose of parasites given and the duration of infection. The responses of the rat to infection with N. brasiliensis are compared with host responses to other helminths and microorganisms, and suggestions are made as to their possible functions and significance.