Toxoplasma gondii: Redistribution of monoclonal antibodies on tachyzoites during host cell invasion

Lytic Cycle ofToxoplasma gondii

“…The exclusive nature of this structure has been demonstrated in two ways. First, antigen-antibody complexes, but not uncoupled antigen, are shed from the parasite surface as it passes through the moving junction (45). Second, host plasmalemma proteins are selectively excluded depending on the nature of their membrane association: GPI-anchored proteins pass through the moving junction and associate with the nascent vacuole, whereas transmembrane-anchored proteins are excluded from it (100).…”

A new release on life: emerging concepts in proteolysis and parasite invasion

“…1B) whereas capping is observed for apical invasion proteins. Shaving occurs continuously as the parasite penetrates and is (Dubremetz et al ., 1985;Grimwood and Smith, 1995) Yes (Mineo and Kasper, 1994;He et al ., 2002) Unknown TgMIC1/MIC4/MIC6 (Meissner et al ., 2002b) Yes (Fourmaux et al ., 1996;Brecht et al ., 2001) MPP1 TgMIC2/M2AP Yes (Carruthers et al ., 1999;Harper et al ., 2004) MPP1 Zhou et al ., 2004) TgMIC3/MIC8 (Meissner et al ., 2002b) Yes (Garcia-Reguet et al ., 2000;Meissner et al ., 2002b) MPP1 TgAMA1 (Donahue et al ., 2000;Hehl et al ., 2000) Unknown MPP1 (S. A. Howell, M. J. Blackman and V. B. Carruthers, unpublished) Plasmodium PfTRAP and PbTRAP (Bhanot et al, 2003;Silvie et al ., 2004) Yes (McCormick et al ., 1999;Akhouri et al ., 2004) Serine protease (Silvie et al .. 2004) PfCSP (Stewart and Vanderberg, 1988; Yes (Pinzon-Ortiz et al ., 2001) Unknown PfMSP1/MSP6/MSP7 (Stafford et al ., 1994) Yes (Goel et al ., 2003;Li et al ., 2004) MESH (Howell et al ., 2003) PkAMA1 and PfAMA1 (Deans et al ., 1984;Howell et al ., 2001) Yes (Fraser et al ., 2001) MESH (Howell et al ., 2003) EBL-DBP (Camus and Hadley, 1985;Haynes et al ., 1988) Yes (Camus and Hadley, 1985;Haynes et al ., 1988) Unknown Py235 (Ogun and Holder, 1996) Yes (Ogun and Holde...…”

“…First, it is conceivable that the intimate junction formed between the parasite surface and the neck of the nascent PV does not allow room for large ZSPs to pass and they must therefore be clipped off to allow parasite entry into the vacuole. This seems unlikely, however, as it is clear that intact immunoglobulin G (which has a molecular mass of around 160 kDa) can be carried into the invaded cell bound to ZSPs on the parasite cell surface (Dubremetz et al, 1985;Blackman et al, 1994). A second proposition, not unrelated to the immunological 'smokescreen' hypothesis of Burkot et al (1991), suggests that shedding of abundant, highly immunogenic and possibly even functionally redundant parasite surface components may act in vivo to divert the host effector immune system away from critical epitopes or surface molecules.…”

Conditional Expression ofToxoplasma gondiiApical Membrane Antigen-1 (TgAMA1) Demonstrates That TgAMA1 Plays a Critical Role in Host Cell Invasion

“…In T. gondii, the asexual stage tachyzoites move over solid surfaces, including cells, by an unusual form of substrate-dependent gliding motility (Sibley et al, 1998;Hakansson et al, 1999). After the apical end of a parasite comes in contact with the host cell membrane, apical secretory organelles (micronemes and rhoptries) sequentially discharge their contents (Dubremetz et al, 1993;Carruthers and Sibley, 1997) and a zone of tight interaction forms between the two cells (Nichols and O'Connor, 1981;Dubremetz et al, 1985;Grimwood and Smith, 1995). An invagination in the host cell plasma membrane develops at the point of entry and progressively deepens, ultimately surrounding the fully internalized parasite (Suss-Toby et al, 1996).…”