Identification of a potential protective microfilarial antigen from Litomosoides carinii (Nematoda, Filarioidea).

The proteins of the filarial parasite Litomosoides carinii that are presented to the host in the course of a natural infection were assessed by surface and intrinsic labelling, microfilarial agglutination assays and ELISA. Surface labelling revealed several proteins present on all parasite stages which were recognised by infected animals. Only one major surface protein of 55 KD was found on microfilariae, while in all other stages (adult males, adult females and infective larvae isolated from pool animals) a range of proteins could be labelled. Immunisation with live microfilariae obtained from blood provoked sera which agglutinated microfilariae in vitro and co-precipitated the 55 KD surface protein. A proportion of animals quantitatively infected with 30 infective larvae (L3) developed antibodies during prepatency that were capable of agglutinating microfilariae, suggesting a common epitope between L3/L4 and microfilariae. Intrinsic labelling of microfilarial proteins was used to identify three additional proteins of 16, 29 and 43 KD which may also be important during infection. The anti-microfilarial antibody titre was quantified by ELISA using microfilarial antigen and sera from various time points during the course of a natural infection.