Effect of Hemolymph from Biomphalaria glabrata on Schistosoma mansoni Infection in Mice ∗

Abstract

Discussion and Summary

Recent studies have indicated that when foreign blood components are injected into mice infected with S. mansoni, the metabolism of the worms is affected resulting in changes in oviposition and death. Intraperitoneal injection of washed erythrocytes from Macaca mulatta injected into mice resulted in diminution of egg laying capacity and death of females (2). Also injection of Forssman antigen, prepared from guinea pig kidney resulted in an increased pigment formation in the worms and eggs laid in the tissues (3).

Injection of hemoglobin from nonmammalian sources, and thus very foreign to mice, was thought of as a good prospect, with the idea that the metabolism of the worm could be altered more efficiently. Michelson (4) reported that the hemolymph from B. glabrata has at least four major hemoglobin components, thus the hemolymph from this snail was used since they are easily available.

Injections of snail hemolymph into infected mice resulted first in changes in the oogram with the disappearance of immature eggs indicating a rapid effect on the females, and finally death of both sexes. After death of the worms, the eggs remaining in the tissues were rapidly absorbed, and the liver returned to normal gross and microscopic contexture.

The mechanism by which the worms are killed is not totally understood. The hemocyanins and hemolymphs are markedly immunogenic substances, which makes it easy to postulate that death of the worms is caused by an immunological reaction between antibodies in mouse plasma and hemolymph antigen in the intestinal ceca of worms.

Since mice developed high titered antibodies against the hemolymph, as shown by the agar gel reactions in which a 1:64 dilution of hemolymph was still positive, the antigen-antibody reaction could take place between the antibodies in plasma against homologous or heterologous hemoglobins within the worm. Such reaction might cause disturbances in the metabolism of pigment which deposits in large amounts and is not properly disposed. The marked accumulation of pigment observed in the dead worms suggests that this may be the case (Fig. 1).

It could also be speculated that the snail hemolymph or its degradation products become toxic to the worm, without postulating an immunological reaction. This, however, is unlikely since the snail serves as the intermediate host for the parasite, in which development takes successfully.

Changes observed in the livers of infected mice injected with snail hemolymph are very significant. The tissue returns to a normal histological structure and gross appearance. These observations are being investigated in more detail.