Detection of multiple variable antigen types in metacyclic populations of Trypanosoma brucei

The identification of antigen types in tsetse salivary gland metacyclic populations of Trypanosoma brucei requires the production of monospecific antisera to the corresponding bloodstream variable antigen types. Monospecific antisera against clones from cyclically transmitted populations are difficult to prepare, however, owing to the antigenic lability of such clones. This problem has been overcome by isolating an antigenically stable clone from a syringe-infected rabbit at a time when its serum showed incipient activity towards metacyclic trypanosomes. Monospecific antisera raised against this clone reacted with up to 20% metacyclics in trypanolysis and immunofluorescence tests, confirming that a clone-derived metacyclic population of T. brucei is heterogeneous with respect to variable antigen type.