The role of Interferon-γ in the diagnosis of toxoplasmosis in pregnancy

The precise diagnosis of Toxoplasma gondii infection during pregnancy is crucial but not always so straightforward. Infections are usually asymptomatic and often pregnant women present with doubtful serologic tests, which make their interpretation very difficult for the clinician. In fact the differential diagnosis between early seroconversion and false positive IgM is always puzzling, furthermore therapy with spiramycin, given every time IgM are found to be positive, can delay IgG production and mask seroconversion. It appears clear that serology alone is not enough for a correct diagnosis. There is the need for new tests that are adequately sensitive and specific, standardized, easy to perform and to interpret. The demonstration of the importance of host cellular immunity in the control of T.gondii infection, with the production of IFN-γ mainly by sensitized T-cells mirrors the immune response in the course of the infection with Mycobacterium tuberculosis. Given the similarities between these two intracellular pathogens the idea emerged of exploiting IGRA tests (Interferon Gamma Release Assays) routinely used for the diagnosis of latent tuberculosis infection for a more precise diagnosis of toxoplasmosis. In this study we describe an experimental test based on the measurement of IFN-γ response after stimulation of whole blood by parasitic antigens in order to demonstrate how it is possible to adapt the same test designed for tuberculosis to manage every challenging serologic status, given the potential serious consequences for the foetus in case of confirmed maternal infection.