Immunocytochemical localization of antigens recognized by human antisera in infective larvae of Wuchereria bancrofti

Identification and location of albumin-like antigens in third-stage larva of W. bancrofti, in adult forms of Litomosoides chagasfilhoi and in the free-living nematode Caenorhabditis elegans

Antigens resembling those of host proteins have been identified on the surface of several filarial parasites, such as immunoglobulins and serum albumins. The origin of albumin-like antigens on filarial parasites remains unclear. Several authors suggested that they have been adsorbed, or that they were metabolic waste products from nutritional utilization of human albumin, or perhaps a contamination with human products. This study searched for human albumin-like antigens by Western blot and ultrastructural analyses on filarial parasites, third stage of W. bancrofti and adult females of Litomosoides chagasfilhoi, and on the free-living Caenorhabditis elegans nematode. Our results showed approximately 67kDa proteins recognized by anti-human albumin antibodies on extracts and excretory-secretory (ES) products of the third-stage W. bancrofti. Similar albumin-like proteins were also detected on the filarial parasite L. chagasfilhoi and on C. elegans extracts. The immunocytochemistry analysis showed human albumin-like antigens on similar tissues of these nematodes. These results provide evidence that these proteins have antigenic similarity and similar distribution in nematodes tissues. Our observations suggest that albumin-like antigens presented on filarial parasites are not acquired from the host, but rather are shared antigenic determinants found even in the third-stage larvae recovered from the invertebrate host.

Cytochemical characterization of the third-stage larva of Wuchereria bancrofti (Nematoda: Filarioidea)

In the present paper, we report the results we obtained using several cytochemical techniques to analyze the infective larva of Wuchereria bancrofti. An imidazole osmium tetroxide solution was used to visualize unsaturated fatty acids. A highly contrasted material forming a continuous structure was observed on the larval surface and over the epicuticle. A strong reaction was observed on the esophagus and also on the inner secreted material. Carbohydrates containing vic-glycol groups were not observed on the cuticle of the third-stage larva of W. bancrofti submitted to the Thiéry technique. Using a panel of eight gold-labeled lectins, we found that the cuticle exhibited slight labeling with all lectins used, indicating residues of N-acetyl-D: -glucosamine, N-acetyl-galactosamine, D: -galactose, D: -manose, and L: -fucose. Surface anionic sites were visualized by using cationized ferritin particles. Treatment with trypsin partially inhibited the reaction, whereas the treatment with chondroitinase ABC, a specific enzyme for glycosaminoglycans, completely abolished the labeling with cationic particles.