Relative Insensitivity of a Kenyan Strain of Leishmania donovani to Pentavalent Antimony Therapy in Hamsters

Abstract

racidium and the eggshell retained stainability with immunofluorescence (Fig. 2). When nonheated sections were used for titration of sera by the IIF technique, the titer differed at different sites on the sections (Table II). The intraoval space showed stainability at higher dilutions than miracidia or host tissues. The positive titers against the antigen in this space ranged from 1: 80 to 1: 2,560. These titers were much higher than those measured by the COP test. When autoclaved sections were used, the titers of these sera against the antigen in the intraoval space were reduced at least fourfold. Furthermore, there seemed to be a correlation between the COP titer and the IIF titer detected on the autoclaved sections. Using histochemical techniques, Smith and von Lichtenberg(1967, Am. J. Pathol. 50:933-1007) have demonstrated a variety of substances associated with the contents of S. mansoni eggs, and they reported the existence of periodic acidSchiff (PAS) positive materials in the space beracidium and the eggshell retained stainability tween the miracidium and the eggshell. Booter et al. (1979, J. Immunol. 122: 39-43) isolated a polysaccharide antigen from S. mansoni eggs. Similarly, Long et al. (1981, Infect. Immun. 34: 389-396) obtained glycoprotein fractions from crude egg antigens of S. japonicum that contained COP inhibitory activity. We have demonstrated that there was amylase-resistant PAS positive material in the intraoval space of S. japonicum where the stainability by IIF technique was retained after autoclaving. We also demonstrated that the stainability with PAS was not altered by autoclaving (Fig. 3). These results show that the heat-stable antigen taking part in the COP reaction is most probably a polysaccharide and is located in the area between the miracidium and the eggshell. Infections of rabbits with S. japonicum and collections of the sera were done at the Schistosomiasis Control and Research Project (SCRP), Palo, Leyte, Philippines, for which we thank their staff.