After invading the host organism, a battle occurs between the parasitic protists and the host's immune system, the result of which determines not only whether and how well the host survives and recovers, but also the fate of the parasite itself. The exact weaponry of this battle depends, among others, on the parasite localisation. While some parasitic protists do not invade the host cell at all (extracellular parasites), others have developed successful intracellular lifestyles (intracellular parasites) or attack only the surface of the host cell (epicellular parasites). Epicellular and intracellular protist parasites have developed various mechanisms to hijack host cell functions to escape cellular defences and immune responses, and, finally, to gain access to host nutrients. They use various evasion tactics to secure the tight contact with the host cell and the direct nutrient supply. This review focuses on the adaptations and evasion strategies of parasitic protists on the example of two very successful parasites of medical significance, Cryptosporidium and Leishmania, while discussing different localisation (epicellular vs. intracellular) with respect to the host cell.

• Klíčová slova
• Cryptosporidium, Leishmania, adaptation to parasitism, epicellular, evasion strategies, extracellular, host defence, intracellular, parasitic protist, parasitophorous sac, parasitophorous vacuole, unicellular parasite,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Apicomplexa are unicellular eukaryotes that parasitise a wide spectrum of invertebrates and vertebrates, including humans. In their hosts, they occupy a variety of niches, from extracellular cavities (intestine, coelom) to epicellular and intracellular locations, depending on the species and/or developmental stages. During their evolution, Apicomplexa thus developed an exceptionally wide range of unique features to reach these diversified parasitic niches and to survive there, at least long enough to ensure their own transmission or that of their progeny. This review summarises the current state of knowledge on the attachment/invasive and nutrient uptake strategies displayed by apicomplexan parasites, focusing on trophozoite stages of their so far poorly studied basal representatives, which mostly parasitise invertebrate hosts. We describe their most important morphofunctional features, and where applicable, discuss existing major similarities and/or differences in the corresponding mechanisms, incomparably better described at the molecular level in the more advanced Apicomplexa species, of medical and veterinary significance, which mainly occupy intracellular niches in vertebrate hosts.

• Klíčová slova
• apical complex, attachment, epimerite, feeder organelle, mucron, myzocytosis, nutrition, parasitophorous vacuole/sac, pores, trophozoite,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Recent studies on motility of Apicomplexa concur with the so-called glideosome concept applied for apicomplexan zoites, describing a unique mechanism of substrate-dependent gliding motility facilitated by a conserved form of actomyosin motor and subpellicular microtubules. In contrast, the gregarines and blastogregarines exhibit different modes and mechanisms of motility, correlating with diverse modifications of their cortex. This study focuses on the motility and cytoskeleton of the blastogregarine Siedleckia nematoides Caullery et Mesnil, 1898 parasitising the polychaete Scoloplos cf. armiger (Müller, 1776). The blastogregarine moves independently on a solid substrate without any signs of gliding motility; the motility in a liquid environment (in both the attached and detached forms) rather resembles a sequence of pendular, twisting, undulation, and sometimes spasmodic movements. Despite the presence of key glideosome components such as pellicle consisting of the plasma membrane and the inner membrane complex, actin, myosin, subpellicular microtubules, micronemes and glycocalyx layer, the motility mechanism of S. nematoides differs from the glideosome machinery. Nevertheless, experimental assays using cytoskeletal probes proved that the polymerised forms of actin and tubulin play an essential role in the S. nematoides movement. Similar to Selenidium archigregarines, the subpellicular microtubules organised in several layers seem to be the leading motor structures in blastogregarine motility. The majority of the detected actin was stabilised in a polymerised form and appeared to be located beneath the inner membrane complex. The experimental data suggest the subpellicular microtubules to be associated with filamentous structures (= cross-linking protein complexes), presumably of actin nature.

• MeSH
• Apicomplexa cytologie   účinky léků   fyziologie   ultrastruktura   MeSH
• cytoskelet účinky léků   metabolismus   MeSH
• mikroskopie MeSH
• pohyb účinky léků   MeSH
• trofozoiti účinky léků   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH

• MeSH
• antigeny protozoální chemie   genetika   metabolismus   MeSH
• Apicomplexa imunologie   fyziologie   MeSH
• apikoplasty imunologie   fyziologie   MeSH
• biologická adaptace MeSH
• biologická evoluce MeSH
• druhová specificita MeSH
• extracelulární prostor imunologie   metabolismus   parazitologie   MeSH
• interakce hostitele a parazita * MeSH
• lidé MeSH
• membránové proteiny chemie   genetika   metabolismus   MeSH
• protozoální infekce zvířat imunologie   metabolismus   parazitologie   MeSH
• protozoální infekce imunologie   metabolismus   parazitologie   MeSH
• protozoální proteiny chemie   genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• antigeny protozoální MeSH
• membránové proteiny MeSH
• protozoální proteiny MeSH