Lectins as carbohydrate recognition proteins other than enzymes or immunoglobulins play important roles in living systems, e.g., in celi celi recognition. They are considered to be involved in snail-trematode immune interactions, i.e., in a system where antibodies are lacking and lectins might at least partially substitute immunoglobulin functions. From the snail side, lectins can be located on haemocyte surfaces as receptors for foreignness and they can be found freely in plasma. The latter can function as agglutinins/opsonins helping in the recognition of parasites by haemocytes. They may also link immune cells and pathogens by recognition of surface carbohydrates on both. Lectins of parasite origin could also be involved in snail-trematode interactions. They might function as trematode surface receptors for snail glycoconjugates in parasite masking strategies. Functions other than the involvement in the snail's immune response or the parasite’s evasion strategies might be fulfilled by lectins as well. Among these may be host-finding, penetration, orientation in the host, nutrition. It cannot be omitted that lectin-saccharide reactions represent only a part of the snail-trematode interactions and thus, results obtained from lectin experiments are a rough simplification of the actual, very complicated situation. An array of immune and other reactions comprised of yet unknown bioactive molecules certainly exists in snails and, on the other hand, trematode mechanisms to escape or otherwise interact with these, might be involved at the same time. But we can certainly conclude that a more complete view of the complex snail-trematode interactions also necessitates a more profound knowledge of the identity and functioning of lectins and their ligands, in host and parasite.
Motolice jsou úspěšnou a rozšířenou skupinou parazitů člověka a zvířat. Jejich životní cykly jsou však často komplikované a zahrnují několik ontogenetických stadií i obligátních hostitelů. Pro přenos z hostitele na hostitele mohou motolice využívat potravní řetězce; někdy za tímto účelem ovlivňují i chování napadeného hostitele. Některé skupiny motolic na potravní řetězce nespoléhají a jejich stadia ve vnějším prostředí aktivně vyhledávají hostitele pomocí receptorů. Úspěšným nalezením hostitele však "boj o přežití" nekončí – motolice musí rychle reagovat na vnitřní prostředí hostitele, zejména zvládnout zpracování živin a odvrátit útok jeho imunitního systému. and Trematodes are widespread group of human/animal parasites. Their life cycles are complex and comprise several developmental stages and obligatory hosts. Food chains are frequently used by trematodes for host-to-host transmission; for this purpose host behavior is sometimes influenced by these parasites. Some trematodes produce actively swimming larvae that are able to identify hosts in the outer environment. Host-recognition and -invasion must be accompanied by subsequent rapid morphological, physiological and other changes in trematodes, in order to acquire host nutrients, prevent host immune attack and the like.
Trichobilharzia regenti is a neurotropic bird schistosome, causing cercarial dermatitis in humans. In this study, ZAP cDNA expression library from Radix peregra s. lat. hepatopancreases containing intramolluscan stages of T. regenti was constructed and screened using PCR with specific and degenerate primers, designed according to previously described serine and cysteine peptidases of other parasite species. Full-length sequences of cathepsins B1 and L, and two serine peptidases, named RpSP1 and RpSP2, were obtained. The protein-protein BLAST analysis and parallel control reactions with template from hepatopancreases of T. regenti non-infected snails revealed that only cathepsin B1 was of parasite origin. The remaining sequences were derived from the snail intermediate host, which implies that the initial source of parasite mRNA was contaminated by snail tissue. Regardless of this contamination, the cDNA library remains an excellent molecular tool for detection and identification of bioactive molecules in T. regenti cercariae.