TIME-COURSE CHANGES IN ANTIBODY-RESPONSES TO DIFFERENT STAGES OF ANGIOSTRONGYLUS-CANTONENSIS IN EXPERIMENTALLY INFECTED-RATS

Sprague-Dawley rats were infected by stomach intubation of 200 third-s tage larvae of Angiostrongylus cantonensis. Sera were collected at 2, 4, 6 and 8 weeks after infection. Sera from uninfected rats were used as the control. Humoral immune responses to different antigens were mo nitored by enzyme-linked immunosorbent assay (ELISA) and by crossed im munoelectrophoresis (CIE). Soluble antigens prepared from 3rd- and 5th -stage larvae and adult worms by homogenization and sonication were ad justed to the same protein concentrations and employed in ELISA and CI E. No antibodies against the 3 stages of the parasite were detected in the control sera or in sera collected from rats in the 2nd week of in fection. Antibodies specific for 3rd-stage larvae appeared in the bloo d of the infected rats during the 4th week of infection as detected by ELISA but not by CIE. Peak ELISA levels against 5th-stage larvae and adults were observed in the 8th week of infection. Sera collected in t he 4th and 8th week of infection contained detectable antibodies again st 5th-stage larvae by CIE. Antigens extracted from 5th-stage larvae d eveloped 8 and 4 peaks with sera collected in the 4th and 8th week, re spectively, while those from adults formed 7 and 5 peaks, respectively .