Schistosoma mansoni: egg granuloma reduction in challenged mice after vaccination with irradiated-attenuated cercariae.

Response of Swiss albino mice vaccinated with irradiated-attenuated cercariae or repeatedly infected with normal cercariae of Schistosoma mansoni were known to develop resistance to reinfection. The mean (+/- SD) of the hepatic granuloma numbers and diameters for vaccinated-challenged group (I) were 2 +/- 0.89/1mm2 and 116 +/- 11.5 microns, for repeatedly infected group (II) were 2 +/- 0.63/1mm2 and 2 +/- 0.89/1mm2 and 195 +/- 11.8 microns and for control group (III) were 4 +/- 1.36/1mm2 and 140 +/- 12.3 microns respectively. Mean of the diameter of the granulomas were significantly smaller in the group vaccinated with irradiated cercariae than the other two groups. Most of the granulomas in groups I and II were fibro-cellular while all granulomas in group III were cellular. Predominent cell types of the granulomas were lymphocytes in groups I and II and eosinophils in group III. The incidence of focal hydropic and fatty degenerations, necrosis and prominent kupffer cell hyperplasia were lower in group I. These results supported that granuloma size reduction in all vaccinated animals were apparently effective in sequestering egg toxins and reduced hepatocytes damage. The present study gives encouragement that a vaccine to enhance protection against disease in human schistosomiasis is possible.