The expression of the Mr 30,000 antigen in the third stage larvae of Brugia pahangi.

The expression of the Mr 30,000 surface antigen in the third stage larvae (L3) of Brugia pahangi has been investigated. The antigen could be detected only with great difficulty in the mosquito derived L3 externally labelled with 125I but was more easily labelled in 24 and 48 h post-infective larvae harvested from the vertebrate host. Labelling of a detergent extract of mosquito derived L3 with 125I demonstrated that the Mr 30,000 antigen was indeed present in this life cycle stage, presumably in an internal localization. It seems likely that the Mr 30,000 antigen is not fully expressed in the parasite cuticle until after infection of the vertebrate host. The data presented also suggest that there are major differences in the surface properties of the mosquito derived L3 compared to the p.i. L3 harvested from the vertebrate host.