G. W. Hunter

Studies on schistosomiasis. XVII. Non-reciprocal acquired resistance between Schistosoma mansoni and Schistosomatium douthitti in mice.

Abstract Attempts to study “cross immunity” reactions between Schistosoma mansoni and Schistosomatium douthitti revealed a non-reciprocal, partial acquired resistance. Mice which were “immunized” by 5 exposures of 10 cercariae each to S. douthitti and challenged with 50 S. mansoni cercariae did not show any reduction in the number of S. mansoni adults recovered when compared with the challenge control. However, the reciprocal cross in which the mice were “immunized” with similar numbers of S. mansoni cercariae and challenged with S. douthitti , showed a highly significant reduction in S. douthitti in comparison with the challenge control. The homologous crosses showed little evidence of “immunity” upon challenge.

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

Abstract 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.

Studies on schistosomiasis. XVI. The effect of immune serum upon egg production by Schistosoma mansoni in mice

Data are presented concerning egg production by Schistosoma mansoni in the mouse host after the administration of homologous immune serum during the 29th to 49th days of infection. Estimates of egg production and distribution in the tissues were made to the 54th day of infection. There were no statistically significant differences in worm development, egg production, or distribution of eggs between host groups receiving immune serum, normal serum, or physiological saline. The average daily production of eggs per mature female worm was estimated to range from 202 to 274. The great majority of eggs occurred in the liver and small intestine.

Studies on schistosomiasis. XX. Further studies on the immunogenic significance of Schistosoma mansoni eggs in albino mice when subjected to homologous challenge.

A group of experimental mice was given ten subcutaneous injections of living S. mansoni eggs at 4to 7-day intervals. Each mouse received an approximate total of 5,500 eggs. One group of control mice received a like number of injections of the supernate from the egg suspensions; another control group remained untreated. All groups were challenged by percutaneous exposure to 100 S. mansoni cercariae at intervals ranging from 2 to 42 days after the last egg injection. Antibody response due to the egg injections was demonstrated by the miracidial immobilization test, but no increased resistance to S. mansoni challenge infection attributable to the egg injections could be demonstrated. The immunogenic significance of schistosome eggs deposited in the tissues of the mammalian host remains uncertain. Antibody reactive with eggs has been demonstrated by Oliver-Gonzalez (1954) and Oliver-Gonzalez, Bauman, and Benenson (1955) who showed that the anti-egg precipitins were species specific. Circumstantial evidence that eggs in tissues are necessary for the development of acquired resistance to Schistosomatium douthitti and Schistosoma mansoni in mice has been presented (Kagan and Lee, 1953; Crandall and Hunter, 1961; Hunter et al., 1962a). Hunter and Crandall (1962b) in preliminary experiments produced some resistance to homologous challenge infection in mice by the injection of living schistosome eggs, but the results were not entirely consistent. Recently Hsui and Hsii (1961) and Sadun, Yamaki, and Burke (1961) using the zoophilic Formosan strain of S. japonicum as an immunizing infection and the human Japanese strain as a challenge infection have suggested that eggs in the tissues are not necessary to demonstrate some degree of resistance in experimental animals. Hsui, Hsii, and Osborne (1962) using X-irradiated cercariae of S. japonicum for immunization of monkeys produced evidence of partial resistance to homologous challenge as manifested by reduced egg production in immunized animals. Villella, Gomberg, and Gould (1961, 1962) working with S. mansoni in mice have shown that irradiation of cercariae with cobalt 60 results in sterile worms, and that mice infected with irradiated cercariae exhibit some degree of resistance to challenge infections. Smithers (1962) using X-irradiated S. mansoni cercariae and monkeys as the test animal generally confirmed the work of Villella et al. and Hsui et al. in that a partial resistance to reinfection was produced by exposure to irradiated cercariae. Smithers states that even large numbers of irradiated cercariae produce only an incomplete protection against S. mansoni in rhesus monkeys. In some of the studies on irradiation complete sterilization of the worms was not always attained. Ritchie, Garson, and Erickson (1962) failed to demonstrate resistance to S. mansoni in mice after the injection of homogenates of lyophilized cercariae, adult worms, and eggs. These recent findings do not exclude the possibility that eggs, when present, contribute significantly to immunity in schistosome infections. Because previous experiments on inoculation Received for publication 27 August 19Q2. * With the aid of Grants E-1893 and E-2500 from the Division of Allergy and Infectious Diseases of the National Institutes of Health, U. S. Public Health Service. t Department of Microbiology, The University of Texas Southwestern Medical School, Dallas. + Department of Microbiology, College of Medicine, University of Florida, Gainesville. ? Resident Coordinator, L.S.U.-International Center for Medical Research and Training, San Jose, Costa Rica on leave, Department of Microbiology, College of Medicine, University of Florida, Gainesville.

Studies on schistosomiasis: XXII. Cross resistance in Schistosoma mansoni and Nippostrongylus brasiliensis infections in albino mice☆

Abstract Immunization by infective larvae of Nippostrongylus brasiliensis and a challenge by Schistosoma mansoni cercariae resulted in a significantly lower recovery of worms when compared with the controls. The reciprocal of this experiment did not yield statistically significant results. Passive-hemagglutination tests utilized S. mansoni and N. brasiliensis antigens and mouse serum from S. mansoni and N. brasiliensis infected mice. Immunoelectrophoresis showed that these two helminth species shared at least one antigenic component.