Diagnosis of infection with Toxoplasma gondii in pregnant women, neonates and immunocompromised patients

<p>Infection with Toxoplasma gondii poses unique diagnostic problems like long-term persistence of specific IgM-antibodies, which makes it difficult to use the presence of Toxoplasma-specific IgM-antibodies alone as a sign of acute infection. The importance of determining the time of infection in pregnant women is also a unique diagnostic challenge in Toxoplasma diagnostics.</p><p>The first paper in this thesis compares the performance of different enzyme immuno assays, immunofluorescence assays, immunosorbent agglutination assays and IgG-avidity assays. The study showed that a combination of an IgM assay followed by an IgG-avidity test was the best combination to estimate the time interval in which infection had taken place. Diagnosis of infection in newborns without Toxoplasma-specific IgM- or IgA antibodies is difficult and a two-dimensional immunoblot assay to distinguish between maternal and child IgG-antibodies with different specificities was developed having higher sensitivity than previous assays.</p><p>A new IgG-avidity assay based on recombinant antigens was developed, which effectively abolished the problem of long-term low IgG-avidity seen in samples analysed by assays using whole cell, lysed antigen. Enzyme immuno assays with whole cell, lysed antigen pose problems with poor discrimination between IgG negative and low-positive samples and recombinant antigens should provide assays with less background, however, the sensitivity may be reduced.</p><p>Two studies show how combinations of recombinant antigens perform in assays of Toxoplasma-specific IgG- and IgM-antibodies. The assays do not yet have the same sensitivity as whole cell, lysed antigen based assays, but the concept is promising and should be further explored. T. gondii infection is a problem in immunodeficient hosts as the parasite remains alive in the chronically infected.</p><p>Current strategies for diagnosing these infections rely on regular testing for Toxoplasma-specific DNA by PCR in blood and other fluids including bronchioalveolar lavage (BAL). We show that a new, real time PCR based assay can be used to detect Toxoplasma in BAL fluids from HIV patients.</p><h3>List of scientific papers</h3><p>I. Roberts A, Hedman K, Luyasu V, Zufferey J, Bessieres MH, Blatz RM, Candolfi E, Decoster A, Enders G, Gross U, Guy E, Hayde M, Ho-Yen D, Johnson J, Lecolier B, Naessens A, Pelloux H, Thulliez P, Petersen E (2001). Multicenter evaluation of strategies for serodiagnosis of primary infection with Toxoplasma gondii. Eur J Clin Microbiol Infect Dis. 20(7): 467-74. <br><a href="https://pubmed.ncbi.nlm.nih.gov/11561802">https://pubmed.ncbi.nlm.nih.gov/11561802</a><br><br> </p><p>II. Beghetto E, Buffolano W, Spadoni A, Del Pezzo M, Di Cristina M, Minenkova O, Petersen E, Felici F, Gargano N (2003). Use of an immunoglobulin G avidity assay based on recombinant antigens for diagnosis of primary Toxoplasma gondii infection during pregnancy. J Clin Microbiol. 41(12): 5414-8. <br><a href="https://doi.org/10.1128/JCM.41.12.5414-5418.2003">https://doi.org/10.1128/JCM.41.12.5414-5418.2003</a><br><br> </p><p>III. Pietkiewicz H, Hiszczynska-Sawicka E, Kur J, Petersen E, Nielsen HV, Stankiewicz M, Andrzejewska I, Myjak P (2004). Usefulness of Toxoplasma gondii-specific recombinant antigens in serodiagnosis of human toxoplasmosis. J Clin Microbiol. 42(4): 1779-81. <br><a href="https://doi.org/10.1128/JCM.42.4.1779-1781.2004">https://doi.org/10.1128/JCM.42.4.1779-1781.2004</a><br><br> </p><p>IV. Nielsen HV, Schmidt DR, Petersen E (2005). Diagnosis of congenital toxoplasmosis by two-dimensional immunoblot differentiation of mother and child immunoglobulin g profiles. J Clin Microbiol. 43(2): 711-5. <br><a href="https://doi.org/10.1128/JCM.43.2.711-715.2005">https://doi.org/10.1128/JCM.43.2.711-715.2005</a><br><br> </p><p>V. Petersen E, Thalib L, Gras L, Paul M, Wallon M, Evengard B, Hayde M, Gilbert R for the European Multicentre Study on Congenital Toxoplasmosis (EMSCOT) (2005). Screening for congenital toxoplasmosis: accuracy of IgM and IgA tests after birth. [Submitted]</p><p>VI. Petersen E, Borobio MV, Guy E, Liesenfeld O, Meroni V, Naessens A, Spranzi E, Thulliez P (2005). European multicenter study of the LIAISON automated diagnostic system for determination of Toxoplasma gondii-specific immunoglobulin G (IgG) and IgM and the IgG avidity index. J Clin Microbiol. 43(4): 1570-4. <br><a href="https://doi.org/10.1128/JCM.43.4.1570-1574.2005">https://doi.org/10.1128/JCM.43.4.1570-1574.2005</a><br><br> </p><p>VII. Petersen E, Edvinsson B, Benfield T, Lundgren B, Evengard B (2005). Diagnosis of pulmonary infection with toxoplasma gondii immunocompromised patients. [Manuscript]</p><p>VIII. Buffolano W, Baghetto E, Del Pezzo M, Spadoni A, Di Cristina M, Petersen E (2005). The use of recombinant antigens for the early postnatal diagnosis of congenital toxoplasmosis. [Submitted]</p>