Chronic infection by atypical Toxoplasma gondii strain induces disturbance in microglia population and altered behaviour in mice

Rapid genotyping of Toxoplasma gondii isolates via Nanopore-based multi-locus sequencing

Toxoplasma gondii is an obligate intracellular parasite associated with severe disease, especially in the immunosuppressed. It is also a cause of congenital malformation and abortion in both animals and humans and is considered one of the most important foodborne pathogens worldwide with different strains showing variable distribution and differing pathogenicity. Thus, strain-level differentiation of T. gondii isolates is an essential asset in the understanding of parasite's diversity, geographical distribution, epidemiology and health risk. Here, we designed and implemented an Oxford Nanopore MinION protocol to analyse genomic sequence variation including single nucleotide polymorphisms (SNPs) and insertion/deletion polymorphisms (InDel's) of four different genomic loci, part of protein coding genes SAG2, SAG3, ROP17 and ROP21. This method provided results with the sequencing depth necessary for accurate differentiation of T. gondii strains and represents a rapid approach compared to conventional techniques which we further validated against environmental samples isolated from wild wood mice. In summary, multi-locus sequence typing (MLST) of both highly conserved and more polymorphic areas of the genome, provided robust data for strain classification in a platform ready for further adaption for other strains and pathogens.

Observing astrocyte polarization in brains from mouse chronically infected with Toxoplasma gondii

Toxoplasma gondii (T. gondii) is a protozoan parasite that infects approximately one-third of the global human population, often leading to chronic infection. While acute T. gondii infection can cause neural damage in the central nervous system and result in toxoplasmic encephalitis, the consequences of T. gondii chronic infection (TCI) are generally asymptomatic. However, emerging evidence suggests that TCI may be linked to behavioral changes or mental disorders in hosts. Astrocyte polarization, particularly the A1 subtype associated with neuronal apoptosis, has been identified in various neurodegenerative diseases. Nevertheless, the role of astrocyte polarization in TCI still needs to be better understood. This study aimed to establish a mouse model of chronic TCI and examine the transcription and expression levels of glial fibrillary acidic protein (GFAP), C3, C1q, IL-1α, and TNF-α in the brain tissues of the mice. Quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay, and Western blotting were employed to assess these levels. Additionally, the expression level of the A1 astrocyte-specific marker C3 was evaluated using indirect fluorescent assay (IFA). In mice with TCI, the transcriptional and expression levels of the inflammatory factors C1q, IL-1α, and TNF-α followed an up-down-up pattern, although they remained elevated compared to the control group. These findings suggest a potential association between astrocyte polarization towards the A1 subtype and synchronized changes in these three inflammatory mediators. Furthermore, immunofluorescence assay (IFA) revealed a significant increase in the A1 astrocytes (GFAP+C3+) proportion in TCI mice. This study provides evidence that TCI can induce astrocyte polarization, a biological process that may be influenced by changes in the levels of three inflammatory factors: C1q, IL-1α, and TNF-α. Additionally, the release of neurotoxic substances by A1 astrocytes may be associated with the development of TCI.

Toxoplasma gondii infection and brain inflammation: A two-sample mendelian randomization analysis

Background

Toxoplasma gondii is an opportunistic parasitic protozoan that can cause highly fatal toxoplasmic encephalitis when the host immune system is compromised. However, the transition from chronic to acute infection remains poorly understood. In this study, we conducted a 180-day observation of tissue damage and inflammation in the brains of mice infected with T. gondii. Subsequently, we investigated the inflammatory factors that T. gondii infection may alter using two-sample Mendelian randomization (MR) analysis.

Methods

We first established a mouse model of T. gondii infection. Subsequently, the mice were euthanized, the brain tissue collected, and immunohistochemistry and hematoxylin and eosin staining performed to observe tissue damage and inflammatory conditions at various time points. Our study also included a published large-scale genome-wide association study meta-analysis that encompassed the circulating concentrations of 41 cytokines. This dataset included 8293 individuals from three independent population cohorts in Finland. Genetic association data for T. gondii were sourced from the Integrative Epidemiology Unit and European Bioinformatics Institute datasets, which included 5010 and 559 individuals of European ancestry, respectively. To assess the causal relationship between T. gondii infection and inflammatory biomarkers, we applied a two-sample MR.

Results

Inflammation and damage resulting from T. gondii infection varied among the distinct regions of the mouse brain. Based on the MR analysis results, three inflammatory biomarkers were chemically assigned to Chemokines and Others, including IP10 (interferon gamma inducible protein-10), MCP1 (monocyte chemoattractant protein-1), and TRAIL (TNF-related apoptosis-inducing ligand).

Conclusion

Our study commenced with the assessment of tissue damage and progression of inflammation in distinct regions of the mouse brain after T. gondii infection. Subsequently, using MR analysis, we detected potential alterations in inflammatory factors associated with this infection. These findings offer valuable insights into the mechanisms underlying toxoplasmic encephalitis and suggest directions for the prevention and treatment of T. gondii infections.

Genetic diversity of Toxoplasma gondii in South America: occurrence, immunity, and fate of infection

Toxoplasma gondii is an intracellular parasite with a worldwide distribution. Toxoplasma gondii infections are of great concern for public health, and their impact is usually most severe in pregnant women and their foetuses, and in immunocompromised individuals. Displaying considerable genetic diversity, T. gondii strains differ widely according to geographical location, with archetypal strains predominantly found in the Northern Hemisphere and non-archetypal (atypical) strains, with highly diverse genotypes, found mainly in South America. In this review, we present an overview of the identification and distribution of non-archetypal strains of T. gondii. Special attention is paid to the strains that have been isolated in Brazil, their interaction with the host immunological response, and their impact on disease outcomes. The genetic differences among the strains are pivotal to the distinct immunological responses that they elicit. These differences arise from polymorphisms of key proteins released by the parasite, which represent important virulence factors. Infection with divergent non-archetypal strains can lead to unusual manifestations of the disease, even in immunocompetent individuals.