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Interferon-Gamma Release Assay: An Effective Tool to Detect Early Toxoplasma gondii Infection in Mice
Qing Yin1, Saeed El-Ashram2, Hongbin Liu3
1State Key Laboratory for Agrobiotechnology, China Agricultural University, Beijing, 100193, China; National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
Abstract:
Early diagnosis of Toxoplasma gondii infection before the formation of tissue cysts is vital for treatment, as drugs available for toxoplasmosis cannot kill bradyzoites contained in the cysts. However, current methods, such as antibody-based ELISA, are ineffective for detection of early infection. Here, we developed an interferon-gamma release assay (IGRA), measuring the IFN-γ released by T lymphocytes stimulated by Toxoplasma antigen peptides in vitro, for the detection of T. gondii infection in mice. Splenocytes isolated from infected mice were stimulated by peptides derived from dense granule proteins GRA4 and GRA6 and rhoptry protein ROP7, and released IFN-γ was measured by ELISA. Results showed that both acute and chronic infection could be detected by IGRA. More importantly, IGRA detected infection as early as the third day post infection; while serum IgM and IgG were detected 9 days and 13 days post infection, respectively. Our findings demonstrated that an IGRA-positive and ELISA-negative sample revealed an early infection, indicating the combination of IGRA and ELISA can be employed for the early diagnosis of T. gondii infection in human beings, cats and livestock.
Insights
Detecting Toxoplasma gondii infection early is crucial for effective treatment. A new interferon-gamma release assay (IGRA) shows promise for diagnosing infections sooner than current antibody tests.
Area of Science:
- Immunology
- Parasitology
- Infectious Diseases
Background:
- Toxoplasma gondii infection requires early diagnosis for effective treatment, as current drugs are ineffective against tissue-cysteine bradyzoites.
- Existing antibody-based methods like ELISA are insufficient for detecting early-stage T. gondii infections.
Purpose of the Study:
- To develop and evaluate an interferon-gamma release assay (IGRA) for the early detection of Toxoplasma gondii infection.
- To compare the diagnostic sensitivity and timing of IGRA with traditional antibody-based methods (ELISA) in a mouse model.
Main Methods:
- Splenocytes from T. gondii-infected mice were stimulated in vitro with specific Toxoplasma antigen peptides (GRA4, GRA6, ROP7).
- Interferon-gamma (IFN-γ) release was quantified using ELISA.
- Serum IgM and IgG antibody levels were measured to determine infection onset and duration.
Main Results:
- The IGRA successfully detected both acute and chronic T. gondii infections in mice.
- IGRA identified infection as early as day 3 post-infection, significantly preceding the detection of IgM (day 9) and IgG (day 13) antibodies.
- IGRA-positive and ELISA-negative results indicated early-stage infection.
Conclusions:
- The developed IGRA is a sensitive tool for early diagnosis of T. gondii infection.
- Combining IGRA with ELISA offers a potential strategy for early and accurate diagnosis of toxoplasmosis in humans, cats, and livestock.
- Early detection via IGRA can facilitate timely treatment before the formation of resistant tissue cysts.
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