A stage-specific calcium-binding protein from microfilariae of Brugia malayi (Filariidae).

The monoclonal antibody MF1 has been shown to cause transient clearance of blood-borne microfilariae in gerbils infected with Brugia malayi. The present study demonstrates that the MF1 antibody recognizes a proteinaceous determinant on two polypeptides of 70 and 75 kDa. Both the monoclonal antibody and antisera raised to the gel-purified antigen show binding restricted to mature microfilariae. Intrauterine and recently shed microfilariae apparently lack the MF1 molecules. Prominent 45Ca-binding molecules comigrate with the MF1 antigens in one-dimensional electrophoresis (under both reducing and non-reducing conditions), and co-purify through ion exchange chromatography. The MF1 antigen thus appears to be a developmentally regulated calcium-binding protein(s).