Monoclonal antibodies to secreted antigens of Brugia malayi define a cross-reactive non-phosphocholine determinant on helminth parasites.

The excretory-secretory (ES) antigens of the filarial parasite Brugia malayi adult (BmA) and microfilariae (MF) were analysed for differences in their protein composition by two-dimensional gel electrophoresis. Both BmA and MF biosynthetically labelled with [3H]-leucine released a 200 kD molecule with pI (isoelectric point) ranging from 5.1 to 6.8. A monoclonal antibody (MoAb) to phosphocholine (PC) immunoprecipitated the 200 kD molecule with a PI of 5.1-5.3 from both BmA and MF. Immunization of CBA/N mice with ES antigens resulted in MoAb that reacted with PC, as well as some that did not (ES-1, ES-2 and ES-3). The epitopes recognized by these non-PC MoAb varied greatly in their molecular weight, heat-resistance, TCA-solubility and metaperiodate-sensitivity, which suggests a proteoglycan nature of the epitope. An antigen capture assay using ES-1 and ES-3 detected a circulating filarial antigen not only in patients infected with Wuchereria bancrofti (77-83% of those with asymptomatic microfilaraemia and 52-60% of those with chronic lymphatic obstruction) but also in serum from patients infected with other helminth parasites (12-100%). Indeed, the epitope recognized by these MoAb was also present on other helminth parasites, which suggests conservation of a carbohydrate-like prosthetic group(s) on diverse helminth species.