Worm and larval burden, histopathological and ultrastructural evaluation of T spiralis vaccination using crude worms and/or larvae antigens: experimental studies

ABSTRACT

Currently, there is no vaccine for T spiralis; however, several studies have been made towards understanding the immune mechanisms that contribute to host protection against it. The aim of the present study is to evaluate the protective effect of vaccination by T spiralis adult, larval and combinea adult and larval crude antigens against trichinellosis in experimental mice. Swiss male albino mice [No. = 125] were divided mm 5 groups. Groups A, h and C were immunized by T spiralis crude larval antigen, crude worm antigen, and combined larval and worm antigens, respectively. One week after the last dose of injection, each mouse was injected orally with 150-200 larvae. Two other groups [D and E] served as infected non immunized control groups. Group E. received adjuvant and phosphate buffer saline before infection. At the 8tn day post-infection [PI], 12 mice from each group were sacrificed and the intestinal worm burden was assessed, while the muscle larval burden was evaluated at 28th day P1 in the remaining mice of each group. Intestinal and skeletal muscle specimens were prepared for histopathological study. Meanwhile, adults and larvae were examined by scanning electron microscopic [SEM] and infected muscle sections were examined by transmission electron microscope [TEM]. Combined antigen gave the highest reduction% in intestinal worm and larval muscle burdens 92% and 96%, respectively], followed by larval antigen [86% and 91%], then worm antigen [73% and 88%], compared with infected non immunized control groups. Compared with groups [A and B], group C gave significant reduction in both intestinal and muscle burdens. Histopathological examination revealed marked decrease in intestinal inflammatory infiltrates, and marked reduction of encysted larvae with mild infiltration around the degenerated larvae in mice of group C. SEM and TEM results confirmed the significant effect of the combined vaccine [Group C]. Vaccination with combined worms and larval antigens gave the most protective action against T spiralis challenge infection. The use of combined antigen in mass vaccination of reservoir animals may decrease the risk of human infection