Differences In Worm Burdens Research Articles

Protective immunity to Schistosoma mansoni in mice is dependent on antibody and complement but not on radiosensitive leukocytes

The role of complement in the control of the Schistosoma mansoni infection in mice was investigated in vivo. The number of schistosomula recovered from the lung 5 days post-infection was used as a parasitological criterion of immunity. A significant difference in worm burden was observed between normal and immune mice. In contrast, when cobra venom factor (CVF) was injected into normal or immune mice 3 h before challenge, a significant increase in worm burden was noticed compared to untreated mice. We also investigated the protective mechanisms in mice that had been exposed to 650 rads of 60Co gamma radiation before challenge infection. Our results show that gamma-irradiated immune mice, depleted of more than 90% of their circulating or tissue leukocytes, are still able to destroy most of the parasites of a challenge infection with cercariae, suggesting that the radiosensitive leukocytes are not essential in the effector mechanisms of this protective immunity to S. mansoni. These results provide evidence of a role for the complement system, in association with radioresistant effector cells, in protective immunity occurring in the first hours after infection with S. mansoni.

Comparative development of Australian strains of Echinococcus granulosus in dingoes ( Canis familiaris dingo) and domestic dogs ( C.f. familiaris), with further evidence for the origin of the Australian syl vatic strain

The growth and development of Australian strains of E. granulosus were compared in domestic dogs and pure-bred dingoes. The sylvatic strain, which is maintained in a cycle between dingoes and wallabies on the Australian mainland, was found to develop far more rapidly in dingoes than in dogs. Development of this strain in dogs was markedly retarded. However, domestic strains of E. granulosus originating from sheep in Tasmania and the Australian mainland developed at a comparable rate in dingoes and dogs. Dingoes were also found to be more susceptible to infection with the sylvatic strain than dogs, as evidenced by considerable differences in worm burdens. No such differences in susceptibility were seen with the domestic strains. These results not only emphasise the inherent differences between the sylvatic and domestic strains of E. granulosus, but also support previous suggestions that the strains were introduced into Australia independently. The fact that the sylvatic strain appears to be physiologically adapted to the dingo indicates that it was brought into Australia many thousands of years before the original domestic strain.

Immunological studies on Metastrongylus apri infection. IV. Influence of whole body X-irradiation or anti-guinea pig thymocyte serum injection on acquired immunity in thymectomized guinea pigs.

Two experiments, I and II, were carried out on guinea pigs to elucidate the defense mechanism against Metastrongylus apri infection. In Experiment I, to produce the status of scarcencss in thymus-derived cells (T-cells) animals were exposed to whole body X-irradiation (300 R) seven days after thymectomy. Immediately after exposure they were vaccinated orally with 1, 000 larvae attenuated by 5×104R of X-rays (Group A). On the 25th day after vaccination they were subjected to challenge infection with 500 normal larvae. Two control groups, B and C, were set up. In Group B, animals were not treated, but vaccinated and challenged. In Group C, animals were not treated nor vaccinated, but challenged. All the guinea pigs were killed on the 21st day after challenge to examine the presence of worms in the lungs. The number of worms recovered from the lungs was 0-77 (mean, 22.8) for Group A, 0-2 (mean, 0.3) for Group B and 1-116 (mean, 43.4) for Group C. There was a significant difference in worm burdens, as determined by Mann-Whitney's "U" test, between Groups A and B, but not between Groups A and C (P&lt0.05). These results showed that T-cells might play an important role in the identification of larval antigen. In Experiment II, thymectomized guinea pigs were vaccinated orally with 1, 000 larvae attenuated by 5×104R of X-rays. Then 25 days later they were subjected to challenge infection with 500 normal larvae. They were given intraperitoneally with 1.0 ml of antithymocyte serum (ATS) on the day of challenge infection and then with 0.5ml every two days until 9 injections were made (totalling 5.5ml each), so that T-cells might be suppressed (Group A). Two control Groups, B and C, were set up. In Group B, animals were not treated, but vaccinated and challenged. In Group C, animals were not treated nor vaccinated, but challenged. On the 21st day after challenge, all the animals were killed to examine the presence of worms in the lungs. The number of worms recovered from the lungs was 4-254 (mean, 44.7), 0-5 (mean, 1.2) and 29-274 (mean, 95.8) for Groups A, B and C, respectively. There was a significant difference in worm burdens, as determined by Wilcoxon's "U" test, between Groups A and B, as well as between Groups A and C (P&lt0.05). These results showed that T-cells, which had a close relationship to cell-mediated immunity, might be suppressed by thymectomy and ATS injection, suggesting the important role of these cells in the defense mechanism against M. apri infection.

Ostertagia circumcincta infection in lambs originating from larvae which survived the winter

Four worm-free lambs were grazed from May to October 1972 on a paddock carrying a low residual infection of O. circumcincta larvae whilst another group grazed a similar paddock carrying a substantial residual larval infection. On the first paddock the lambs acquired low worm burdens of mature worms passing large numbers of eggs, but in spite of this, pasture larval infection remained low. On the second paddock the lambs acquired high worm burdens, a large proportion of which were immature. On this paddock a rise in pasture larval count was observed and this reached a peak in July and August. In spite of the differences in worm burden of the two groups there was no significant difference in weight gain. The mechanism by which the differences in worm burdens may have developed as well as their implications in worm control are discussed.

Immunization of Laboratory Mice against Tetrathyridia of Mesocestoides corti (Cestoda) Using a Secretory and Excretory Antigen and a Soluble Somatic Antigen

A secretory and excretory (ES) antigen was prepared by incubating tetrathyridia in Krebs-Ringer solution for 24 hr. A soluble somatic antigen was prepared by homogenization and subsequent centrifugation of M. corti larvae. Laboratory mice were given a series of injections of the antigen materials, and then challenged with 100 tetrathyridia of M. corti. Autopsy 10 days postinfection revealed that mice receiving ES antigen, and infected either orally or intraperitoneally, harbored approximately 60% fewer larvae as compared to control mice. Mice receiving somatic antigen and infected intraperitoneally showed no significant difference in worm burden as compared to control mice. Mice receiving somatic antigen and infected orally harbored 30.4% fewer larvae as compared to control mice. No precipitate was seen around larvae incubated in serum collected from uninfected mice immunized with somatic antigen; however, a light precipitate was seen around larvae incubated in serum collected from uninfected mice immunized with ES antigen. Several studies have demonstrated that antigen extracted from larval or adult cestode tissue can be used to stimulate levels of immunity to challenge with tissue-invading larvae or intestinal tapeworms (for references see Weinmann, 1970). Excretory and secretory (ES) antigens, however, have not been used to stimulate immunity against cestode infection. This is in spite of the fact that the effectiveness of ES antigen has been successfully demonstrated in nematode and trematode infections (Thorson, 1953; Kagan and Oliver-Gonzalez, 1958; Sadun and Lin, 1959). In this paper, we present our attempts to immunize mice against challenge infections with tetrathyridia of Mesocestoides corti using ES and somatic antigens. MATERIALS AND METHODS

Schistosoma mansoni and S. haematobium: Homocytotropic reagin-like antibodies in infections of man and experimental animals

The immunological response of human beings, chimpanzees, rhesus and cercopithecus monkeys, rabbits, guinea pigs, and mice to infection with Schistosoma mansoni or S. haematobium was studied. Antibodies detected by fluorescent and flocculating techniques were heat stable, not sensitive to 2-mercaptoethanol, and were eluted from Sephadex G-200 in the IgG fraction. Antibodies detected by anaphylactic reactions were destroyed by heating, were inactivated by reduction and alkylation, had a faster electrophoretic mobility than IgG, and were eluted from Sephadex G-200 after IgM and before IgG. Differences in passive cutaneous anaphylactic (PCA) antibody reactions among animals of a given species could not be attributed to differences in worm burdens, organ involvement, or egg excretion. Conversely, the percentage of animals in each species producing PCA antibodies correlated directly with the degree of resistance to the various species studied as determined by the percentage of worm recovery, the general appearance of worm development, the pattern of egg excretion, and the clinical and pathological observations.

Studies on the Transfer of Immunity to Ascaris suum in Mice by Serum, Parabiotic Union, and Cells

Transfer of immunity to Ascaris suum larval infections was accomplished by parabiotic union of C57BL mice. A significantly lower worm burden after a challenge infection was found in the nonimmune partners of immune mice as compared to nonimmune partners of normal mice. Passive transfer of immunity by serum was attempted three times. In only a single experiment did injection of immune serum result in a decreased worm burden. An attempt was made to transfer immunity to ascaris larvae by peritoneal exudate cells and spleen cells. No significant difference in worm burden was found in the group of mice receiving cells from donors as compared to that of control groups of mice. Numerous investigations have demonstrated acquired immunity to ascaris infection in several animal species; however, the immunologic basis of acquired resistance to this helminth is not well defined. Circulating antibody can be measured in the immune animal but the protective capacity of antibody to ascaris infections has not been demonstrated with certainty. In 1938, Kerr attempted to transfer immunity to ascaris passively in guinea pigs by serum and showed some protection to a lethal infection. Sprent and Chen (1949) were unable to transfer immunity in mice but their immune sera were obtained from animals immunized with nonviable ascaris materials. Recently Kelley and Nayak (1963) reported that immunity to ascaris larvae was produced by passive transfer of homologous immune serum to young pigs. Oliver-Gonzalez (1943) and Taffs (1961) found that immune serum had a parasiticidal effect on ascaris larvae. On the other hand, Crandall and Arean (1964) showed that humoral factors in mice were responsible for inhibiting growth of ascaris larvae in diffusion chambers but had no parasiticidal activity. The present investigation was undertaken in an attempt to elucidate the mechanisms of acquired resistance to ascaris infection by a study of the transfer of immunity by (1) immune sera, (2) parabiotic union, and (3) peritoneal exudate and spleen cells. Received for publication 6 January 1965. * This investigation was supported in whole by Public Health Service Research Grant AI-0321205 from NIH. EXPERIMENTAL PROCEDURES AND RESULTS

Studies on schistosomiasis. XIV. Effects of cortisone upon the Schistosoma mansoni burden in mice

The effects of cortisone acetate administered to mice at different times relative to an initial infection with Schistosoma mansoni was studied. The criterion of hormone influence upon the course of infection was the number of parasites recovered from treated and control mice six to eight weeks after infection. There was a small but statistically significant reduction in worm burden in the majority of cortisone-treated mice. It was found that essentially the same effect upon worm burden was produced whether the hormone was administered up to shortly before exposure to cercariae or commencing on the fifteenth day after infection when the parasites are in the liver or portal system. No significant difference in worm burden was detected in mice that were treated with cortisone in the fourth and fifth weeks.