Retinal scar shaped like DNA, representing genetic influence on ocular toxoplasmosis.

Decoding Toxoplasmosis: How Your Genes Influence Scarring

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Nico Varela in Health & Wellness December 2025 • 5 min read.

"New research reveals how genetic variations in the interferon-gamma (IFN-γ) gene impact the severity of retinal damage from Toxoplasma gondii infections, offering insights into personalized treatment approaches."


Ocular toxoplasmosis, a common cause of visual impairment, arises from infection by the parasite Toxoplasma gondii. While many infected individuals remain asymptomatic, others develop severe retinal scarring that can lead to vision loss. The severity of these lesions varies widely, prompting researchers to investigate the underlying factors that contribute to these differences.

A groundbreaking study published in Memórias do Instituto Oswaldo Cruz has shed light on the role of genetics in determining the severity of retinal damage caused by toxoplasmosis. The research focuses on single nucleotide polymorphisms (SNPs) within the interferon-gamma (IFN-γ) gene (IFNG), a critical component of the immune system's response to T. gondii.

The study's findings suggest that specific genetic variations in IFNG are associated with distinct types of retinochoroidal scar lesions, offering a potential explanation for the diverse clinical outcomes observed in patients with ocular toxoplasmosis. This discovery paves the way for more personalized approaches to managing and treating this prevalent eye condition.

Genetic Clues: How IFNG SNPs Shape Toxoplasmosis Outcomes

Retinal scar shaped like DNA, representing genetic influence on ocular toxoplasmosis.

The research team, led by Ricardo Guerra Peixe and Lilian MG Bahia-Oliveira, conducted a cross-sectional, population-based genetic study involving individuals living in Campos dos Goytacazes, Brazil, an area known for its high prevalence of toxoplasmosis. The study included 411 participants, carefully categorized based on their serological status for T. gondii and the presence and severity of retinal lesions.

The researchers investigated ten SNPs within the IFNG gene, focusing on their association with different types of retinal scar lesions. The lesions were classified into three categories (A, B, and C) based on severity, with type A representing the most severe and type C the least severe scarring. After rigorous statistical analysis, including Bonferroni correction to account for multiple testing, two SNPs, rs2069718 and rs3181035, showed significant associations with specific types of retinal lesions.

  • rs2069718 and Type A Lesions: The GG genotype of the rs2069718 SNP was associated with a significantly higher risk of developing severe (type A) retinal scars. Individuals with this genotype also exhibited lower levels of IFN-γ production. The presence of the A allele, in either homozygous (AA) or heterozygous (AG) form, appeared to be protective.
  • rs3181035 and Type C Lesions: The presence of the T allele in the rs3181035 SNP, either in homozygous (TT) or heterozygous (CT) form, was linked to an increased susceptibility to less severe (type C) retinal lesions. Conversely, the homozygous CC genotype seemed to offer protection.
  • No Direct Correlation with IFN-γ Levels: Interestingly, the study did not find a direct correlation between the rs3181035 SNP and IFN-γ secretion levels, suggesting that the SNP's influence on disease severity might involve other mechanisms beyond IFN-γ production.
These findings suggest that different inflammatory mechanisms, influenced by genetic variations in IFNG, contribute to the development of distinct types of retinal lesions in ocular toxoplasmosis. The study highlights the complex interplay between genetics, the immune response, and the clinical manifestations of this disease.

Implications and Future Directions

The study's findings have significant implications for understanding and managing ocular toxoplasmosis. By identifying specific genetic markers associated with disease severity, clinicians may be able to:<ul><li><b>Assess Individual Risk:</b> Determine an individual's genetic predisposition to developing severe retinal lesions following T. gondii infection.</li><li><b>Personalize Treatment Strategies:</b> Tailor treatment approaches based on an individual's genetic profile, potentially optimizing outcomes and minimizing the risk of vision loss.</li></ul>Future research should focus on:<ul><li><b>Larger, More Diverse Populations:</b> Validating these findings in larger and more diverse populations to ensure generalizability.</li><li><b>Functional Studies:</b> Investigating the precise mechanisms by which these IFNG SNPs influence IFN-γ production and other immune responses relevant to T. gondii infection.</li><li><b>Longitudinal Studies:</b> Following individuals with different IFNG genotypes over time to assess the long-term impact of these genetic variations on disease progression and treatment outcomes.</li></ul>By unraveling the complex interplay between genetics and the immune response in ocular toxoplasmosis, researchers can pave the way for more effective prevention and treatment strategies, ultimately preserving vision and improving the quality of life for millions affected by this prevalent eye condition.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

What is ocular toxoplasmosis?

Ocular toxoplasmosis is an eye disease caused by infection with the parasite *Toxoplasma gondii*. While many people infected with *Toxoplasma gondii* don't show any symptoms, some develop retinal scarring that can severely impact vision. The extent of this scarring varies, prompting investigation into the underlying causes. This condition is significant because it's a common cause of visual impairment, and understanding its causes is crucial for developing effective treatments.

2

Why is the *interferon-gamma* (IFN-γ) gene (IFNG) important in toxoplasmosis?

The *interferon-gamma* (IFN-γ) gene (IFNG) is important because it plays a critical role in the immune system's response to *Toxoplasma gondii*. *Interferon-gamma* (IFN-γ) is a cytokine crucial for activating immune cells to fight intracellular pathogens like *Toxoplasma gondii*. Genetic variations in IFNG can influence how effectively the body clears the parasite, impacting the severity of the infection. Without a strong IFN-γ response, the parasite can cause more damage to the retina.

3

What are single nucleotide polymorphisms (SNPs), and how are they related to toxoplasmosis?

Single nucleotide polymorphisms (SNPs) in the *interferon-gamma* (IFN-γ) gene (IFNG) are variations in a single nucleotide (building block of DNA) at a specific position in the gene. These SNPs can affect how much *interferon-gamma* (IFN-γ) is produced or how well it functions. Because *interferon-gamma* (IFN-γ) is crucial for controlling *Toxoplasma gondii* infection, SNPs in the *interferon-gamma* (IFN-γ) gene (IFNG) can influence the severity of ocular toxoplasmosis. Some SNPs may lead to a weaker immune response, resulting in more severe retinal scarring.

4

What specific SNPs were identified in the study, and what were their associations with retinal lesions?

The study identified two specific SNPs, rs2069718 and rs3181035, within the *interferon-gamma* (IFN-γ) gene (IFNG) that are associated with different types of retinal lesions in ocular toxoplasmosis. The GG genotype of the rs2069718 SNP was linked to more severe (type A) retinal scars and lower levels of *interferon-gamma* (IFN-γ) production. The presence of the T allele in the rs3181035 SNP was linked to less severe (type C) retinal lesions. Understanding these associations could help assess an individual's risk of developing severe retinal damage and tailor treatment strategies accordingly. It is important to note that the study did not find a direct correlation between the rs3181035 SNP and *interferon-gamma* (IFN-γ) secretion levels, suggesting that the SNP's influence on disease severity might involve other mechanisms beyond *interferon-gamma* (IFN-γ) production.

5

What are the potential implications of these genetic findings for treating ocular toxoplasmosis?

These findings could lead to personalized treatment approaches for ocular toxoplasmosis. By identifying individuals at higher risk of developing severe retinal lesions based on their *interferon-gamma* (IFN-γ) gene (IFNG) SNPs, clinicians can tailor treatment strategies to optimize outcomes and minimize vision loss. For example, individuals with the GG genotype of the rs2069718 SNP might benefit from more aggressive or earlier treatment interventions. Further research is needed to fully understand how these SNPs influence the immune response and to develop targeted therapies.

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