John I. Bruce

The cellular and humoral immune response to Schistosoma mansoni infections in inbred rats. I. Mechanisms during initial exposure.

Fisher rats were infected with Schistosoma mansoni by skin exposure to penetrating cercariae. The subsequent development of immunity was ascertained through the rechallenge of animals with cercariae and the simultaneous quantitative assessment of the development of the worm burdens which resulted from each of the two infections. The basic nature of the immune response to rechallenge by S. mansoni was investigated through the adoptive transfer of cells or serum obtained from normal or preexposed animals. The results indicate that the rat develops a strong, immunologically mediated, augmented resistance to infection by S. mansoni which begins within 1 week of initial exposure. This response is reflected in both quantitative and qualitative changes in the development of the reinfecting population and has a general characteristic of an anamnestic or secondary response judged by a variety of immunologic criteria. The developing immunity apparently is both stimulated by, and directed exclusively against, the very early stages of infection. Although the mechanism of this immunity is not clear, it apparently involved the production of significant quantities of protective immunoglobulin.

Schistosoma mekongi sp. n. from man and animals, compared with four geographic strains of Schistosoma japonicum.

Schistosoma mekongi sp. n. is described from man and animals in Cambodia. It is compared to 4 geographic strains of Schistosoma japonicum. It differs from S. japonicum in the size of embryonated eggs, in the length of the prepatent peroid in the mammalian host, and in its utilization of a different snail host. The relative usefulness of conventional morphologic criteria in the differentiation of Asian schistosomes is discussed.

Conventional Giemsa-stained and C-banded chromosomes of seven strains of Schistosoma mansoni.

Karyotypes stained with conventional Giemsa and with a C-banding method were compared among 7 strains of Schistosoma mansoni: 2 from Puerto Rico and 1 each from St. Lucia, Brazil, Venezuela, Egypt, and Kenya. A few differences were noted in relative lengths and centromeric indexes, but overall karyotypes of all strains were similar, with 2n = 16. The W chromosome of the female of all strains had a relatively large heterochromatic block, distinguishing the female from the male karyotype.

Susceptibility of wild mammals to infection by Schistosoma mansoni.

In the past it was believed that mlan was the only epidemiologically important malnmalian host of Schistosoma mansoni. Recent studies, however, have shown that a few other hosts may play a role in the dissemlination of this parasite (Barbosa et al 1958; Kuntz and Malakatis, 1955; Price, 1953; AMartins, 1958). The present investigation was undertaken to determine if wild lmanInals trapped in the Washington, D. C.-Baltimore, Maryland, area were susceptible to S. mansoni. It was regarded as unlikely that any of these aniimals were naturally infected because no recognized snail host of S. mansoni is present in this area. The degree of susceptibility of the various imammals tested was deteriiined by the percentage of parasites developing in the host; the growth and structural development of the worms; the ability of worims to produce eggs; the viability of eggs recovered from the feces, intestine and liver; the infectivity of miracidia for suitable snails; the sex ratio and location of the worms in the host; the length of the prepatent period; and the pathological manifestations of infection.

TRANSPLANTATION OF SCHISTOSOMA JAPONICUM DAUGHTER SPOROCYSTS IN ONCOMELANIA HUPENSIS

Schistosoma japonicum daughter sporocysts obtained from infected Oncomelania hupensis hupensis were successfully transplanted to parasite-free O. hupensis hupensis. Survival and infection rates of recipient snails were 80% and 75% respectively. Intramolluscan development of transplanted daughter sporocysts in recipient snails appears to proceed in a similar manner as those reported for transplanted S. mansoni and S. haematobium in their respective snail intermediate hosts. Complete colonization of the digestive gland of recipient snails by sporocysts was observed 80 days after transplantation. Cercarial production during a 10-day observation from recipient snails was characterized by periods of high and low and irregular daily emissions. The average daily cercarial production was 150 per snail. Cercariae produced by recipient snails were infective to mice. Of those cercariae exposed to mice, approximately 30% developed to adult schistosomes. These results have definitive utility in the maintenance of S. japonicum in the laboratory.

Proteolytic Activity of Schistosoma haematobium Eggs from Human Urines in Egypt

Harold L. Asch,*t Mohamed Fathy A. Saoud,f Adel A. Hassan,f and John I. Bruce,t *Department of Experimental Pathology, Roswell Park Memorial Institute, 666 Elm Street, Buffalo, New York 14263; tCenter for Tropical Diseases, University of Lowell, 450 Aiken Street, Lowell, Massachusetts 01854; and ::Laboratory for Snail and Parasite Biology, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt