[Humoral immune responses to stages of Brugia pahangi in experimentally infected rats].

In the present experiment, Sprague-Dawley rats were inoculated with Brugia pahangi, a lymphatic dwelling filarial parasite. Each rat received 100 third stage larvae (L3) of B. pahangi freshly harvested from Aedes togoi. Rats in the control group were injected with saline. After inoculation, tail vein blood was collected from each rat at 2-week intervals. The immune responses of the infected rats to B. pahangi were measured by the enzyme-linked immunosorbent assay (ELISA). Four types of antigen were prepared from different stages of B. pahangi. The antigen extracts were prepared from microfilaria, L3, and male and female adult worms by homogenization, eight times of freezing and thawing, and centrifugation at 11,000 X g for 45 min at 4 degrees C. Aliquots of supernatant extracts were stored at -20 degrees C. These antigens were adjusted to the same concentration of their protein contents and employed in the ELISA test. Serial serum dilutions were made to determine the concentrations of stage-specific antibodies in each serum sample collected during the infection course. Microfilaria specific antibodies appeared in the blood of infected rats at the 6th week of infection. Peak titer was observed at the 10th week. Subsequently, a gradual decrease was seen in the following month. Serum antibody titers against L3 and adult antigens rised since the 4th week and reached to the peak at 14th week. The exist of common antigens shared by the mature adults and infective larvae were detected by the ELISA and conformed by disc gel electrophoresis.