Toxoplasma gondii: Ultrastructural localization of specific antigens and inhibition of intracellular multiplication by monoclonal antibodies

Lee, Boo-Young; Ahn, Myoung-Hee; Kim, Hyun-Chul; Min, Duk Young

doi:10.3347/kjp.2001.39.1.67

Cited by 8 publications

(4 citation statements)

References 26 publications

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“…We confirmed by IF and TEM that NcROP2Fam-1 indeed belongs to the set of rhoptry proteins. NcROP2Fam-1 was found in the subapical region of free or intracellular parasites and was associated with rhoptry bulbs, consistent with the findings of other ultrastructural localization studies of ROP2 family proteins in T. gondii (Sadak et al 1988;Saffer et al 1992;Soldati et al 1998;Lee et al 2001;Carey et al 2004;Taylor et al 2006;Sloves et al 2012).…”

Section: Discussionsupporting

confidence: 88%

Molecular cloning and characterization ofNcROP2Fam-1, a member of the ROP2 family of rhoptry proteins inNeospora caninumthat is targeted by antibodies neutralizing host cell invasionin vitro

et al. 2013

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S U M M A R YRecent publications demonstrated that a fragment of a Neospora caninum ROP2 family member antigen represents a promising vaccine candidate. We here report on the cloning of the cDNA encoding this protein, N. caninum ROP2 family member 1 (NcROP2Fam-1), its molecular characterization and localization. The protein possesses the hallmarks of ROP2 family members and is apparently devoid of catalytic activity. NcROP2Fam-1 is synthesized as a pre-pro-protein that is matured to 2 proteins of 49 and 55 kDa that localize to rhoptry bulbs. Upon invasion the protein is associated with the nascent parasitophorous vacuole membrane (PVM), evacuoles surrounding the host cell nucleus and, in some instances, the surface of intracellular parasites. Staining was also observed within the cyst wall of 'cysts' produced in vitro. Interestingly, NcROP2Fam-1 was also detected on the surface of extracellular parasites entering the host cells and antibodies directed against NcROP2Fam-1-specific peptides partially neutralized invasion in vitro. We conclude that, in spite of the general belief that ROP2 family proteins are intracellular antigens, NcROP2Fam-1 can also be considered as an extracellular antigen, a property that should be taken into account in further experiments employing ROP2 family proteins as vaccines.

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Section: Discussionsupporting

confidence: 88%

Molecular cloning and characterization ofNcROP2Fam-1, a member of the ROP2 family of rhoptry proteins inNeospora caninumthat is targeted by antibodies neutralizing host cell invasionin vitro

et al. 2013

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“…The central peptide sequence of SAG1 seems to be conserved in all members of the SRS family (37). It is unclear whether Tox203 is reactive with all proteins in the SRS family; however, confocal microscopy in the present study demonstrated that the antigen recognized by Tox203 was located across the entire surface of both intra-and extracellular tachyzoites (18).…”

Section: Discussionmentioning

confidence: 47%

Generation of a Neutralizing Human Monoclonal Antibody Fab Fragment to Surface Antigen 1 ofToxoplasma gondiiTachyzoites

Feng

Ohnishi

et al. 2011

Infect Immun

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A combinatorial immunoglobulin gene library was constructed from lymphocytes in peripheral blood of a patient with toxoplasmosis and screened for production of human monoclonal antibody Fab fragments to recombinant surface antigen 1 (SAG1) of Toxoplasma gondii. Two Fab clones, Tox203 and Tox1403, which consisted of a common heavy chain and different light chains, showed positive staining on the entire surface of tachyzoites in confocal microscopy. Sequence analysis of the heavy-chain gene revealed that the closest germ line V segments were VH3-23. The germ line D segment was D1-7, and the closest germ line J segment was JH4. In the light-chain genes, the closest germ line V segment was V1-17 with the J1 or J4 segments. The dissociation constants of these Fab fragments with recombinant SAG1 were 3.09 ؋ 10 ؊9 M for Tox203 and 2.01 ؋ 10 ؊8 M for Tox1403, indicating that the affinity of Tox203 was 7 times higher than that of Tox1403. Preincubation of T. gondii tachyzoites with Tox203 significantly inhibited their attachment to cultured MDBK cells. Passive immunization of mice with Tox203 also significantly reduced mortality after challenge with T. gondii tachyzoites. This is the first report of bacterial expression of human monoclonal antibody Fab fragments to SAG1 of T. gondii. These results also demonstrate that human Fab fragments to SAG1 might be applicable for immunoprophylaxis of toxoplasmosis.Toxoplasma gondii is an obligate intracellular parasite in the phylum Apicomplexa and infects a variety of warm-blooded domestic and wild animals worldwide. It is an important foodborne parasite transmitted primarily from animals to humans through meat, as well as through oocysts shed by cats into the environment (25). Infection in humans is usually asymptomatic in immunocompetent hosts. However, primary infection during pregnancy can result in severe neonatal malformations and ocular complications in the fetus. In immunocompromised hosts such as patients with human immunodeficiency virus/ AIDS, reactivation of the latent infection results in symptomatic diseases such as toxoplasmic encephalitis (14,22). Transmission of T. gondii by organ transplantation from a seropositive donor to a seronegative recipient is also an important potential cause of disease in heart, heart-lung, kidney, liver, and liver-pancreas transplant patients (25).The surface of T. gondii is the first component to contact the host cells. The T. gondii surface is coated by closely related antigens that belong to the surface antigen 1 (SAG1)-related sequences (SRS) superfamily (13, 16). SAG1 is the most abundant and immunogenic of these antigens and is important for the process of invasion. Treatment of T. gondii with mouse monoclonal or rabbit polyclonal antibodies to SAG1 inhibits parasite attachment to host cells (24). Fab fragments derived from a mouse monoclonal antibody also showed dose-dependent inhibition of parasite attachment (23). Therefore, human monoclonal antibodies to SAG1 may be applicable for prevention of transmission and reactivation ...

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“…Subsequently parasites were harvested and washed once in ice cold PBS. SDS – PAGE and Western Blot analysis were performed as described previously [54] , using 6–12% polyacrylamide gels under reducing condition with 100 mM DTT. Per experiment an equal number of parasites were loaded.…”

Section: Methodsmentioning

confidence: 99%

Rab11A-Controlled Assembly of the Inner Membrane Complex Is Required for Completion of Apicomplexan Cytokinesis

et al. 2009

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The final step during cell division is the separation of daughter cells, a process that requires the coordinated delivery and assembly of new membrane to the cleavage furrow. While most eukaryotic cells replicate by binary fission, replication of apicomplexan parasites involves the assembly of daughters (merozoites/tachyzoites) within the mother cell, using the so-called Inner Membrane Complex (IMC) as a scaffold. After de novo synthesis of the IMC and biogenesis or segregation of new organelles, daughters bud out of the mother cell to invade new host cells. Here, we demonstrate that the final step in parasite cell division involves delivery of new plasma membrane to the daughter cells, in a process requiring functional Rab11A. Importantly, Rab11A can be found in association with Myosin-Tail-Interacting-Protein (MTIP), also known as Myosin Light Chain 1 (MLC1), a member of a 4-protein motor complex called the glideosome that is known to be crucial for parasite invasion of host cells. Ablation of Rab11A function results in daughter parasites having an incompletely formed IMC that leads to a block at a late stage of cell division. A similar defect is observed upon inducible expression of a myosin A tail-only mutant. We propose a model where Rab11A-mediated vesicular traffic driven by an MTIP-Myosin motor is necessary for IMC maturation and to deliver new plasma membrane to daughter cells in order to complete cell division.

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Toxoplasma gondii: Ultrastructural localization of specific antigens and inhibition of intracellular multiplication by monoclonal antibodies

Cited by 8 publications

References 26 publications

Molecular cloning and characterization ofNcROP2Fam-1, a member of the ROP2 family of rhoptry proteins inNeospora caninumthat is targeted by antibodies neutralizing host cell invasionin vitro

Molecular cloning and characterization ofNcROP2Fam-1, a member of the ROP2 family of rhoptry proteins inNeospora caninumthat is targeted by antibodies neutralizing host cell invasionin vitro

Generation of a Neutralizing Human Monoclonal Antibody Fab Fragment to Surface Antigen 1 ofToxoplasma gondiiTachyzoites

Rab11A-Controlled Assembly of the Inner Membrane Complex Is Required for Completion of Apicomplexan Cytokinesis

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