Effect of Ultra Violet Attenuated Cercariae on Antibody Response in Rabbits

Ultraviolet (UV) light is an electromagnetic radiation below the visible wavelengths. Their use in cercariae attenuation needs to be examined. In the present work, Schistosoma mansoni cercariae was exposed to UV radiation. Few studies showed previously an inflicted damage seen on the adult schistosome worms developed from irradiated cercariae. The aim of the study was to find out whether this damage was attributed to direct effect of UV-irradiation on cercariae or due to the host's immunogenicity induced by UVirradiated cercariae. Single as well as multiple exposures of cercariae to UV Light were examined. They were exposed to UV light, for 1, 2 and 3 hrs and then, were subjected to different treatments: the first one was for the assessment of cercarial viability after one hour of the 3 different treatments. The second one was for rabbit infection and the third one was for cercarial antigen preparation. The cercarial antigens (Ag) were recognized by protective antibodies (IgG1 fractions) which then, were separated and purified from vaccinated rabbit's serum. This cercarial Ag was identified as UVISmC1 gene encoding a protein showing 100% identity at the amino acid level with previously identified S. mansoni clones; theses clones are encoding 51.7 kDa antigens elicited as a result of direct effect of UV radiation on cercariae as well as host's immunogenicity induced by UV irradiated cercariae. This was verified by the recognition of this Ag prepared from E coli clones isolated from cDNA expression library. In conclusion, the data showed a remarkable potency of the UV-radiation-attenuated cercaria in eliciting differential high effectiveness in Ab response under laboratory conditions at 1, 2 and 3 hrs of UV light output at 254 nm. An understanding of the protective immune response elicited by RA cercaria may help in designing a candidate vaccine which is still needed.