Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 31. (Budapest, 1998)

DISCUSSION Only three out of the six partially purified protein fractions were found to be involved in the immune response. Fractions Fl and F6 ( Mr > 90 and < 17 kD ) were found to be the most immunoreactive as they reacted with both the cellular and humoral components of immunity from PI days 4 and 8 as revealed by results of the MIT and dot blot analysis. Fraction F2 (Mr 64.5 KD) also detects the circulating IgG but lacks potential for detecting CMI. Gasser et al. (1989) have identified some antigens of Mr range < 14 kD to 94 kD from protoscoleces having sérodiagnostic potential foris. granulosus infection in dogs. Gasser et al. (1990) identified and cloned an antigen that has 100% specificity but low sensitivity. The use of glutathione S-transferase fusion protein (lOpl) was promising in the immunodiagnosis but its origin, location and occurrence in the developmental stages have not been ascertained. In another study > 90 kD and 45 kD polypeptides were detected by immunoblotting using dog sera (Ali 1991). Schantz and Gottstein (1986) reviewed data on the antigens mostly from the hydatid cyst, but studies on the immune response of the definitive host against the adult tapeworms are very scanty. In the present study it was revealed by the MIT that CMI appears on PI day 4 (Table 1). Herd (1977) detected delayed type hypersensitivity in dogs at 24-48 hours by intradermal test after 6 weeks of immunization. The present findings are at variance with the observations of Al-Khalidi (1982), who claimed that CMI elicited by E. granulosus infection develops slowly in the dog and manifests first in the peripheral lymphocytes. Since Al-Khalidi tested CMI as late as PI day 29 only, his experimental schedule was not suitable to ascertain the time of onset of CMI in the earlier phase of infection. In ovine hydatidosis Petrova (1968) observed neutrophilia at PI days 3-5, followed by leukocytosis at PI day 25-30. Ali-Khan and Siboo (1983) found accumulation of eosinophils, lymphocytes and monocytes in the peritoneal cavity of mice 48 days after infection with E. multilocularis. In conclusion, by using the Fl antigen MIT can be employed for the diagnosis of Echinococcus infection of dogs, particularly in the early phase of the prepatent period. The detection of humoral antibody response as early as PI day 4 reflects the strong antigenic potential of Fl, F2 and F6 fractions. Similarly Ali (1991) has demonstrated the IgG response on PI day 4 by immunoblotting using the surface membrane of the protoscoleces as antigen. Contrary to these observations, Movsesijan and Mladenovic (1971) found antibody in dog serum on day 14 after infection with E. granulosus. It is evident that antigenic components were best recognized by sera taken at PI days 16-24. This seems to be the most critical phase in the prepatent period of E. granulosus. During this period not only stabilization and development of reproductive and accessory organs are completed but marked haematological and pathophysiological changes as host reactions have also been observed (Irshadullah and Nizami 1992; Irshadullah 1994 ). Ali (1991) detected the most powerful antigenic polypeptides of the protoscolex membranes in sera from PI day 24, indicating the synthesis and secretion of new proteins, thus stimulating IgG production. Finally, it can be concluded that of the antigenic fractions tested Fl antigen appears to be involved both in the sensitization of cells playing a part in the cellular