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SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts.

ABSTRACT: BACKGROUND: Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22?kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts. METHODS: To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays. RESULTS: Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells. CONCLUSIONS: Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.

SUBMITTER: Macedo AG

PROVIDER: S-EPMC3706231 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts.

Macêdo Arlindo G AG Cunha Jair P JP Cardoso Thyago H S TH Silva Murilo V MV Santiago Fernanda M FM Silva João S JS Pirovani Carlos P CP Silva Deise A O DA Mineo José R JR Mineo Tiago W P TW

Parasites & vectors 20130605

<h4>Background</h4>Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts.<h4>Methods</h4>To accomp ...[more]

PMID: 23735002

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Project description:Toxoplasma gondii's propensity to infect its host and cause disease is highly dependent on its ability to modulate host cell functions. One of the strategies the parasite uses to accomplish this is via the export of effector proteins from the secretory dense granules. Dense granule (GRA) proteins are known to play roles in nutrient acquisition, host cell cycle manipulation, and immune regulation. Here, we characterize a novel dense granule protein named GRA83, which localizes to the parasitophorous vacuole (PV) in tachyzoites and bradyzoites. Disruption of GRA83 results in increased virulence, weight loss, and parasitemia during the acute infection, as well as a marked increase in the cyst burden during the chronic infection. This increased parasitemia was associated with an accumulation of inflammatory infiltrates in tissues in both acute and chronic infections. Murine macrophages infected with ∆gra83 tachyzoites produced less interleukin-12 (IL-12) in vitro, which was confirmed with reduced IL-12 and interferon-gamma in vivo. This dysregulation of cytokines correlates with reduced nuclear translocation of the p65 subunit of the nuclear factor-κB (NF-κB) complex. While GRA15 similarly regulates NF-κB, infection with ∆gra83/∆gra15 parasites did not further reduce p65 translocation to the host cell nucleus, suggesting these GRAs function in converging pathways. We also used proximity labeling experiments to reveal candidate GRA83 interacting T. gondii-derived partners. Taken together, this work reveals a novel effector that stimulates the innate immune response, enabling the host to limit the parasite burden. Importance Toxoplasma gondii poses a significant public health concern as it is recognized as one of the leading foodborne pathogens in the United States. Infection with the parasite can cause congenital defects in neonates, life-threatening complications in immunosuppressed patients, and ocular disease. Specialized secretory organelles, including the dense granules, play an important role in the parasite's ability to efficiently invade and regulate components of the host's infection response machinery to limit parasite clearance and establish an acute infection. Toxoplasma's ability to avoid early clearance, while also successfully infecting the host long enough to establish a persistent chronic infection, is crucial in allowing for its transmission to a new host. While multiple GRAs directly modulate host signaling pathways, they do so in various ways highlighting the parasite's diverse arsenal of effectors that govern infection. Understanding how parasite-derived effectors harness host functions to evade defenses yet ensure a robust infection is important for understanding the complexity of the pathogen's tightly regulated infection. In this study, we characterize a novel secreted protein named GRA83 that stimulates the host cell's response to limit infection.

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SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts.

Publications

SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts.

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