The effect of irradiation on the third stage larvae of Brugia pahangi.

The effect of irradiation on the third stage larvae of the filarial nematode Brugia pahangi was investigated. Labelling with 35S methionine of control or irradiated L3, post-infective L3 or L4 revealed no consistent alterations in the pattern of proteins synthesized. The only significant difference observed was in 125I labelling, where the specific activity of labelling of soluble cuticular proteins was lower in irradiated than in control parasites. This difference may be related to the reduced size of irradiated parasites rather than to a specific effect of irradiation on the expression of cuticular proteins. Irradiated parasites recovered on day 14 post-infection were significantly shorter than control parasites. Irradiation also appeared to have a lethal effect on male parasites, as no recognizable males were recovered from animals given irradiated L3, nor were microfilariae ever observed in these animals. The mechanisms by which irradiation may enhance the immunogenicity of L3 of filarial nematodes are discussed.