Evidence for immune response of hamster against s mansoni

ABSTRACT

Immunity was employed according to the following protocol using adult male hamsters Group 1 [injected subcutaneously with normal saline], group 2 [immunized subcutaneously with 150 irradiated cercariae/hamster [20 kRad]], and group 3 [infected subcutaneously with 150 normal cercariae/hamster [concomitant immunity]]. A total of 36 hamsters/group were reclassified into six subgroups according to the following sensitization period 7, 14, 28, 42, 56 and 84 days post-vaccination. At the end of each sensitization period, six hamsters were challenged through abdominal infection with 100 cercariae/hamster. Sera of blood samples withdrawn weekly post-cercarial challenge for 12 weeks were employed for monitoring of antibodies titer by the following three coating antigens [cercarial, egg and adult worm homogenates] using ELISA technique. The data obtained revealed that both control group 1 and reinfected group 3 displayed progressive immune at 4th and 5th weeks post-challenge [around the time of worm formation and egg-laying commences]. Sera of group 2 revealed that the use of cercarial homogenates, as a coating antigen, displayed early +ve antibody formations. The use of egg homogenate revealed +ve antibody formations during the time of egg-laying commences. Meanwhile, a wide range of +ve antibody formations were concomitant with the use of adult worm homogenate as a coating antigen. Sacrificing the hamster at the end of 12 weeks post-challenge and counting the number of worms revealed that best vaccination was displayed by irradiated cercariae, which elicited progressive resistance to S. mansoni infection that was increased by time of sensitization reaching a very highly significant in magnitude