Primary Toxoplasma gondii infection-associated with hemophagocytic syndrome in a man with HIV infection: a case report

Background Reactivation of latent Toxoplasma gondii (T. gondii) infection is more common than primary infection in patients with human immunodeficiency virus (HIV). We report a rare case of primary T. gondii infection-associated hemophagocytic syndrome (HPS). Case presentation A man with HIV infection presented with fever, dyspnea and pancytopenia. He was diagnosed with primary T. gondii infection by the seroconversion from single-positive IgM antibody to double-positive IgM and IgG antibody. Metagenomic next-generation sequencing (mNGS) of a plasma sample yielded high reads of T. gondii DNA. He responded well to combined anti-Toxoplasma medicines and glucocorticoid treatment. Conclusions In patients with HPS and positive T. gondii IgM antibody, mNGS analysis of a peripheral blood sample is helpful in diagnosing disseminated T. gondii infection. The dynamic changes by serological detection for IgM and IgG of T. gondii further supported the inference that the patient has experienced a primary T. gondii infection.

Toxoplasma gondii infection in pet cats and their owners in northeastern China:an important public health concern

Background Limited information about Toxoplasma gondii infection in pet cats and their owners is available in China. Methods In this study, blood samples were randomly collected from 306 pet cats and 397 corresponding pet owners in Jilin province, northeastern China. Sera from the pet cats and the pet owners were tested for anti-T. gondii antibodies using an modified agglutination test (MAT) and an enzyme-linked immunosorbent assay (ELISA), respectively. Moreover, the risk factors for T. gondii infection in pet cats and corresponding pet owners were explored. Result In total, 62 sera out of 306 examined pet cats (20.3%) and 18.1% (72/397) pet cat owners were seropositive for T. gondii, respectively. The results of statistical analysis showed that both pet cats and their owners from rural area had significantly higher T. gondii seroprevalence than those from urban area (p < 0.001). Moreover, owners of pet cas who have the knowledge of zoonotic protozoan diseases had a significantly lower T. gondii seroprevalence than those without the knowledge of zoonotic protozoan diseases (p < 0.001). Conclusions The present results revealed that the seroprevalence of T. gondii infection are widespread in pet cats and their owners in Jilin province, northeastern China. Residence area and understanding knowledge of zoonotic protozoan diseases are considered to be raleted to the T. gondii infection. Hence, it is necessary to highlight the dangers and protection methods of zoonotic protozoan diseases caused by pet cats, especially in rural area.

Cell-based screen identifies human type I interferon-stimulated regulators of Toxoplasma gondii Infection

Macrophages activated with interferons (IFNs) respond with transcriptional changes that enhance clearance of intracellular pathogens such as Toxoplasma, a ubiquitous apicomplexan parasite that infects more than a billion people worldwide. Although IFNs generally inhibit Toxoplasma, the parasite can also induce components of the host IFN signalling pathway to enhance survival in host cells. Compared to the type II IFN gamma (IFNγ), the role of type I IFNs in macrophage response to Toxoplasma is relatively not well characterized. Here, using fluorescent Toxoplasma and a CRISPR/Cas9 knockout library that only targets interferon-stimulated genes (ISGs), we adapted a loss-of-function flow cytometry-based approach to systematically identify type I ISGs that control Toxoplasma growth in THP-1 cells, a human macrophage cell line. The system enabled the rapid screening of more than 1900 ISGs for type I (IFNα)-induced inhibitors and enhancers of Toxoplasma growth in THP-1 cells. We identified 26 genes that are associated with Toxoplasma growth arrest out of which we confirmed MAX, SNX5, F2RL2, and SSB, as potent IFNα-induced inhibitors of Toxoplasma in THP1 cells. These findings provide a genetic and experimental roadmap to elucidate type I IFN-induced cell-autonomous responses to Toxoplasma.

Impact of Toxoplasma gondii infection on human health

Toxoplasmosis is one of the most prevalent infectious disease around the globe and it is caused by the parasite named Toxoplasma gondii. Infections normally lead to asymptomatic parasite persistence in immunocompetent warm-blooded hosts, including up to 30-50% of humans. However, T. gondii infection has also a major medical concern and can lead to life-threatening diseases, after reactivation in immunocompromized individuals, particularly in patients with human immunodeficiency virus/cancer or organ transplant recipients, after vertical transmission to fetuses of pregnant women and by inducing recurrent uveitis in immunocompetent adults. More importantly, T. gondii undergoes stage conversion from its fast-replicating tachyzoite to slow replicating dormant bradyzoite preferentially in the brain and skeletal muscles, and lesser extent in the eye, liver, kidney and lung which enable the parasite to persist for the whole life of an individual. Due to the persistence behavior of the parasite in different parts of human body, T. gondii can develop multiple human diseases with severe clinical symptoms. In this study, we have summarized the association of T. gondii in multiple human diseases for instance Encephalitis, Parkinson’s disease, Schizophrenia, Heart disease, Ocular Toxoplasmosis, Congenital abnormalities, Cancer and Diabetes. This highlights the potential role of T. gondii in developing fatal diseases, particularly in immunocompromised individuals despite having asymptomatic nature of the parasite. Bioresearch Commu. 8(1): 1093-1099, 2022 (January)

Disseminated Toxoplasma gondii Infection in an Adult Osprey (Pandion haliaetus)

An adult female osprey (Pandion haliaetus) was found weak and unable to fly in Auburn, Alabama in August 2019. The bird was captured and submitted to the Southeastern Raptor Center of the Auburn University College of Veterinary Medicine for evaluation. On presentation, the bird was thin with a body condition score of approximately 1.5 out of 5. The bird died during the examination and was submitted for necropsy. At the necropsy, there was a severe loss of muscle mass over the body, and the keel was prominent. The liver and spleen were moderately enlarged with pale tan to red foci randomly scattered throughout the parenchyma. A histopathologic observation revealed multifocal to coalescing areas of necrosis and hemorrhage with intralesional protozoans in the liver, spleen, lungs, kidney, sciatic nerve, esophagus, cerebrum, heart, and proventriculus. Immunohistochemistry using anti-Toxoplasma gondii-specific antibodies showed a strong positive labeling of the parasite. Semi-nested PCR, specific for the B1 gene of T. gondii, successfully identified T. gondii. This is the first confirmed case of T. gondii infection in an osprey.

Defining the Location of T-bet-expressing Myeloid Cells During Acute Intestinal Toxoplasma gondii Infection

Background/Objective: The protozoan parasite Toxoplasma gondii is the second leading cause of foodborne pathogen-related deaths in the United States. The transcription factor T-bet is indispensable for host immunity against T. gondii. The absence of T-bet results in rapid susceptibility during parasite infection. T-bet has been considered essential for T-cell-derived IFN-g during T. gondii infection; yet, recent research has shown that T-bet is not required for lymphocyte-derived IFN-g responses. Our preliminary research shows that T-bet-deficient mice succumb to parasite infection significantly quicker than mice lacking lymphocytes. This has led to our hypothesis that T-bet-dependent myeloid cells are critical for host resistance during acute intestinal T. gondii infection. The objective of this project was to define the location of the T-bet-expressing myeloid cells in the medial small intestines (MSI) of naïve and infected mice during acute mucosal parasite infection. Methods: We used immunofluorescence microscopy to determine the location of T-bet-expressing myeloid cells in the MSI of naïve and T. gondii infected mice. Mice were orally infected with 40 cysts of the ME49 strain of T. gondii. On days 0 and 5, one-inch MSI segments were harvested, fixed with 4% paraformaldehyde for at least one hour, and then frozen in OCT compound. Tissues were then cut into 8mm sections and placed onto slides for staining. Sections were stained for nuclei, CD11c, T-bet, and T. gondii. Results: Our results revealed T-bet-expressing CD11c+ cells in both the MSI and spleen on days 0 and 5 of T. gondii infection. Summary: These data indicate that T-bet-expressing myeloid cells are present in the MSI during T. gondii infection. Defining the position of these cells will allow us to determine T-bet’s role in mediating myeloid cell-dependent T. gondii clearance. Due to the limited treatment options for patients suffering from toxoplasmosis it is critical to define new mechanisms for eliminating T. gondii.

Over-expression screen of interferon-stimulated genes identifies RARRES3 as a restrictor of Toxoplasma gondii infection

Toxoplasma gondii is an important human pathogen infecting an estimated 1 in 3 people worldwide. The cytokine interferon gamma (IFNγ) is induced during infection and is critical for restricting T. gondii growth in human cells. Growth restriction is presumed to be due to the induction interferon stimulated genes (ISGs) that are upregulated to protect the host from infection. Although there are hundreds of ISGs induced by IFNγ, their individual roles in restricting parasite growth in human cells remain somewhat elusive. To address this deficiency, we screened a library of 414 IFNγ induced ISGs to identify factors that impact T. gondii infection in human cells. In addition to IRF1, which likely acts through induction of numerous downstream genes, we identified RARRES3 as a single factor that restricts T. gondii infection by inducing premature egress of the parasite in multiple human cell lines. Overall, while we successfully identified a novel IFNγ induced factor restricting T. gondii infection, the limited number of ISGs capable of restricting T. gondii infection when individually expressed suggests that IFNγ mediated immunity to T. gondii infection is a complex, multifactorial process.