Changes in the lipophilicity of the surfaces of Meloidogyne incognita and Haemonchus contortus during exposure to host signals.

The surfaces of plant and animal parasitic nematodes share certain lipids, which seem to be important in the infection process. The surfaces of 2 parasitic nematodes, Meloidogyne incognita and Haemonchus contortus, were activated by different pH buffers to allow the insertion of different fluorescent probes. The lipid analogue PKH26 and the surface charge indicator, cationized ferritin, were used as probes with these nematodes but labelled only the retaining 2nd-stage moulted cuticle of H. contortus 3rd-stage larvae (L3). Shedding of the second moult of H. contortus L3 was also visualized with PKH26 and cationized ferritin. The fluorescent anionic lipid probe 5-N-(octadecanoyl)-aminofluorescein (AF18) was inserted into the epicuticle layer of M. incognita 2nd-stage juveniles (J2) and H. contortus L3, and also of the second moult of H. contortus L3. Incubation with tomato root diffusate caused modifications of the M. incognita surface allowing the insertion of AF18. Fluorescence with AF18 was significantly decreased after treating M. incognita J2 with amiloride, a potent blocker of hydrogen and sodium (H+/Na+) antiporter. No surface fluidity was observed in M. incognita J2 and H. contortus L3 pre-treated with alkaline buffer when the lipid analogue AF18 was used in fluorescence recovery after photobleaching experiments. The significance of these findings to host infection processes is discussed.

Identification and characterization of excreted-secreted products and surface coat antigens of animal and plant-parasitic nematodes.

Nematode surface coat (SC) proteins and excreted-secreted products (E-S) are likely to play important roles in the host-parasite interaction and considerable similarities can be found in SC proteins and E-S products from certain plant and animal parasitic nematodes. Monoclonal antibodies raised to E-S products of plant-parasitic nematodes were shown to cross-react with E-S products and the surface coats of the animal parasites Trichinella spiralis and Haemonchus contortus. Most of the antibodies recognized carbohydrate epitopes but the activity of 2 MAbs (IACR-CCNj.2a.15 and IACR-Misec.8D.3) which recognized proteic epitopes in these nematodes were further characterized. Antibody 2a.15 recognized the SC and oral exudate of Meloidogyne incognita, T. spiralis and H. contortus. This antigen was also immunolocalized in the lining of the oesophagus and gut and in the exudate present during ecdysis of H. contortus L3. Antibody 8D.3 reacted with the SC of these nematodes on cryosections but on live nematodes the immunofluorescence was very patchy and was shed from the nematode SC.