Sprague Dawley rats were infected by stomach intubation of 200 third-stage 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 monitored by enzyme-linked immunosorbent assay (ELISA) and by crossed immunoelectrophoresis (CIE). Soluble antigens prepared from 3rd- and 5th stage larvae and adult worms by homogenization and sonication were adjusted to the same protein concentrations and employed in ELISA and CIE. 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 infection. Antibodies specific for 3rd-stage larvae appeared in the blood 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 the 4th and 8th week of infection contained detectable antibodies against 5th-stage larvae by CIE. Antigens extracted from 5th-stage larvae developed 8 and 4 peaks with sera collected in the 4th and 8th week, respectively, while those from adults formed 7 and 5 peaks, respectively.
Angiostrongylus cantonensis, Experimental infection, ELISA, CIE, Stage-specificity
