The detection and measurement of coproantibodies to Nippostrongylus brasiliensis in rats following a primary infection

The effect of vaccination with a recombinant Nippostrongylus brasiliensis acetylcholinesterase on infection outcome in the rat

Nippostrongylus brasiliensis, the rodent hookworm, is a commonly used model of gastrointestinal nematode infection. This parasite, hookworms and several livestock nematode parasites of importance secrete distinct forms of acetylcholinesterases (AChE) that have been ascribed a putative parasite protective function. We tested the hypothesis that vaccination with the secreted enzyme would be deleterious to the parasite. Rats were immunised with a recombinant AChE isoform B via the subcutaneous, intra-peritoneal and intra-nasal routes using different adjuvants dependent on the mode of delivery and subsequently challenged with N. brasiliensis. Rats immunised via the subcutaneous and intra-nasal routes showed a modest but significant decrease in egg output of between 23 and 48%. This was mirrored by differences in the titre of specific antibody isotypes in the serum and mucosa following infection and serum from vaccinated animals was demonstrated to inhibit the activity of recombinant and native AChE. The utility of this model for future development of hookworm and veterinary nematode vaccines is discussed.

The effect of adjuvant and specific or non-specific vaccination on development of protective immunity of rabbits against Trichostrongylus colubriformis infection

Adult New Zealand rabbits were vaccinated subcutaneously with one dose of 100 micrograms adult nematode phosphate buffered saline-soluble proteins (PBS-ASP, groups I and II), a detergent-soluble fraction of adult somatic proteins (DS-ASP, group III) or three doses of 1 mg normal rabbit serum proteins (group IV). Injections of the immunogens in groups II, III and IV were accompanied with beryllium hydroxide, Be(OH)2 as an adjuvant. Vaccinated rabbits and also those of group V (naive) were challenged orally with 10,000 infective larvae of T. colubriformis 14 days after antigen injection and necropsied 2 weeks later. A single dose of PBS-ASP induced 33.5% protection when the antigen was given alone (group I) and 69.4% when injected with Be(OH)2 (group II). A detergent-soluble fraction of ASP given with the adjuvant provided 87.2% protection (group III), whilst non-specific vaccination with serum proteins plus Be(OH)2 elicited 99% protection (group IV). Mesenteric lymph node leukocyte responses were measured using a leukocyte migration inhibition assay. A significant response was observed only in group IV. In ELISA tests IgA antibodies specific to PBS-ASP reached the highest level in the intestinal mucosa of groups I and II and in the bile of groups I and III. Antibody levels of IgG isotype were similar in the intestinal mucosa of all the immunized groups. Nematode antigen was detected using a 'sandwich' ELISA method in faecal protein extracts of rabbits of groups II and III on days 2-6 after challenge.

A rapid method to determine the isotype and specificity of coproantibodies in mice infected with Trichinella or fed cholera toxin

A method was developed to isolate and test coproantibodies from mice infected with Trichinella or mice fed cholera toxin. It was rapid as results were obtained within 3 h, and it was applicable to a single faecal pellet. It reduced the number of experimental animals required 7-fold, and reduced variability, since samples were obtained from the same experimental animal over time. As it was noninvasive, it did not alter normal gut physiology, nor the course of the parasitic infection. The immune response was monitored over time in individual mice, and specific sIgA and IgG isotypes were detected for both Trichinella and cholera toxin by ELISA.

The role of free oxygen radicals in the expulsion of primary infections of Nippostrongylus brasiliensis

The many and varied pathological, immunological and physiological manifestations of infection with Nippostrongylus brasiliensis may be unified by considering the role of leukocyte-generated free oxygen radicals in worm expulsion. Aside from directly damaging the adult stage of N.brasiliensis and possibly leading to its elimination from the small intestine, free radicals may also damage intestinal cells, thereby contributing to the gut pathology characteristic of infection. gamma-Interferon (and possibly tumour necrosis factor) may be involved in the initiation of free radical generation in response to N. brasiliensis and may also contribute to various side effects of infection such as hypertriglyceridaemia and cachexia. gamma-Interferon may initiate free radical generation via the agency of protein kinase C, an enzyme that can induce various additional responses including lysosomal enzyme and amine secretion and arachidonic acid metabolism. The possible interactions between these mediators and free radicals are subtle and diverse and may profoundly affect the course of infection.

Inhibition phenomena mechanisms in experimental obeliscoidosis in rabbits. II. Local and systemic antibody responses

A series of experiments was carried out using adult outbred Polish race rabbits of both sexes infected, during spring or autumn, with 10,000 larvae of Obeliscoides cuniculi, either fresh or stored at 4 degrees C. Extracts of mucosal proteins and bile were collected at postmortem 6 or 12 weeks after infection. Antibody levels were determined in antisera, bile and stomach mucosa by haemagglutination and precipitation tests. Local antibody responses were demonstrated in the stomach and bile, and reactions were obtained with the tissue fluids by haemagglutination and precipitation tests with worm antigens and ES products. Additionally, some specific immunological response was observed in the circulation during the primary infection. These results suggest a clear-cut relationship between increased levels of these antibodies and either larval inhibition or worm expulsion during O. cuniculi infections.

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.

Local and systemic antibody responses in gerbils following vaccination with irradiated or non-irradiated Trichostrongylus colubriformis larvae

Groups of 10 Mongolian gerbils, Meriones unguiculatus, were vaccinated with 1,500 gamma-irradiated Trichostrongylus colubriformis infective larvae (L3) or with non-irradiated larvae. 25 days later five gerbils from each group were necropsied and the remaining gerbils challenged with 1,500 non-irradiated T. colubriformis infective larvae. Systemic, local intestinal and coproantibody levels were compared in each group of gerbils 25 days after vaccination and 26 days after challenge. Strong local intestinal and faecal antibody responses were detected. Coproantibodies reflected antibody levels in the intestinal contents and in mucosal extracts. The results gave further support to the view that coproantibody measurements provide a sensitive index of immunity at mucosal surfaces to intestinal parasites.

Secretory IgA responses in rats to antigens of various developmental stages of Nippostrongylus brasiliensis

Intestinal and faecal IgA responses against different developmental stages of Nippostrongylus brasiliensis were studied in Hooded Lister rats vaccinated subcutaneously with infective larvae or intragastrically with 4th-stage larvae, adult nematodes, adult worm somatic and metabolic antigens. It was found that intragastric administration of L4 or adult worms produced as high resistance to challenge as normal infection. Oral vaccination with adult nematode excretory-secretory (ES) and somatic antigens produced 69 and 17% protection respectively. All vaccination regimes induced a considerable IgA response against somatic and metabolic antigens of the intestinal stages. However, no correlation could be seen between the IgA levels and degree of protection. Analysis of intestinal mucosal, intestinal contents and faecal IgA specific to larval or adult antigens suggests that the IgA is probably induced by antigen(s) common to all intestinal stages. Also secretory IgA responses against surface antigens of intestinal L4 did not show stage specificity, although this was detected in sera.

Nippostrongylus brasiliensis: local humoral responses in the lungs and intestines of rats following vaccination with irradiated larvae

Groups of rats were infected with 2000 normal larvae of Nippostrongylus brasiliensis or larvae irradiated with 10 to 120 kR. On Day 10 after infection half the animals from each group were autopsied. The remainder were challenged with 5000 unirradiated larvae on Day 15 and killed ten days later. During the experiment enteric antibody levels were estimated by coproantibody measurement. At autopsy the worm burdens were determined and worm-specific antibodies evaluated in lung extracts and serum. It was found that the levels of coproantibody detected with adult worm metabolites were positively correlated with the number of adult nematodes recovered from the intestine after primary infection. The challenge induced a similar increase of these antibodies in all immunised rats which reflected a high immunity to reinfection of vaccinated animals. Preliminary immunochemical studies suggested that the coproantibodies had SIgA properties. In lung extracts of rats immunised with larvae irradiated at 40, 80, or 120 kR and in all animals after challenge, antibodies reacting with infective larval antigens were found. Their titres were negatively correlated with serum antibody levels. The significance of bronchial and enteric antibodies in conferring protection against challenge remains to be elucidated.