Surface-associated antigens of Brugia malayi L2 and L3 parasites during vector-stage development

Surface and metabolic labeling procedures were used to characterize the composition and the time of expression of Brugia malayi L2 and L3 surface-associated molecules as the larvae develop within the mosquito vector. Larvae were harvested from mosquito tissues at 5 (early L2), 8(late L2) and 11 (l3) days post-infection and labeled with ¹²⁵I-Iodo-Gen. The results of one-dimensional analysis showed that there is a progressive increase in the complexity of peptides associated with the surface of developing larvae, culminating in the expression of 7 major labeled components on L3s. Both L2 and L3 parasites have surface-associated components of 42,35,33,19 and 17 kDa. Between days 8 and 11 of development in the insect vector, Brugia malayi undergoes the L2 to L3 molt and acquires additional major immunogenic peptides of 40 and 22 kDa. Two-dimensional analyses of extracts from ¹²⁵I-labeled L2s and L3s revealed that the major 35-,33-,19- and 17-kDa molecules are part of a peptide complex that forms a 'ladder' between 17 and 150kDa. To gain information on the times during which the major surface-associated molecules are produced by the parasite, larvae were labeled with [³⁵]methionine either in situ as they developed within the mosquito or during culture after exiting the vector For in situ labeling. [³⁵S]methionine was introduced into the hemolymph of infected mosquitoes by micro-injection at days 2, 5 and 8 post-infection and larvae were allowed to develop for an additional 3 days. The results of 1- and 2-dimensional analyses of [³⁵S]methionine-labeled extracts from vector-stage or post-vector-stage larvae indicate that the molecules associated with the surface of B. malayi L3s are synthesized between day 5 and day 11 of development in the insect host. Immediately after the larvae exit the vector, the synthesis of the 40 and 22-kDa peptides is drastically reduced or terminated.