Patients with diffuse uveitis and inactivetoxoplasmicretinitis lesions test PCR positive forToxoplasma gondiiin their vitreous and blood

Abstract

Background/aims To determine if patients with inactive chorioretinitis lesions who experience chronic toxoplasmic uveitis test PCR positive for Toxoplasma in their ocular fluids. Methods Two patients undergoing long-term anti-toxoplasmic treatment developed chronic uveitis and vitritis. They underwent therapeutic and diagnostic pars plana vitrectomy. Patient specimens were tested for toxoplasmosis by real-time PCR and nested PCR. Patient specimens were also tested for the presence of Toxoplasma antibodies that recognise allelic peptide motifs to determine parasite serotype. Results Patients tested positive for Toxoplasma by real-time PCR at the B1 gene in the vitreous and aqueous humours of patient 1, but only the vitreous of patient 2. Patients were not parasitemic by real-time PCR in plasma and blood. During surgery, only old hyperpigmented toxoplasmic scars were observed; there was no sign of active retinitis. Multilocus PCR–DNA sequence genotyping at B1, NTS2 and SAG1 loci established that two different non-archetypal Toxoplasma strains had infected patients 1 and 2. A peptide-based serotyping ELISA confirmed the molecular findings. Conclusions No active lesions were observed, but both patients possessed sufficient parasite DNA in their vitreous to permit genotyping. Several hypotheses to explain the persistence of the vitritis and anterior uveitis in the absence of active retinitis are discussed.

Ocular Toxoplasmosis: Lessons From Brazil

“…24 Another important observation was the finding that positive intraocular polymerase chain reaction for Toxoplasma is still possible despite an observed lack of active ocular lesions. 25 Finally, the first cross-sectional comparison performed between France and another South American country (Colombia) identified striking differences in vitreous inflammation, vasculitis, and cytokine responses, consistent with South American strains causing more severe ocular toxoplasmosis by altering protective levels of IFN- γ and IL-17 in the aqueous humor of infected eyes. 26 …”

Ocular Toxoplasmosis: an Update

“…However, it should be borne in mind, that toxoplasmosis is a systemic affection with local clinical manifestations. Toxoplasmic DNA is regularly detected in the blood, even in the absence of an active ocular disease [6,44,45]. Hence, an intravitreal therapeutic intervention does not prevent the occurrence of manifestations in the partner eye.…”

Development of Sensitive Nested Real-time PCR for Diagnosis of Acute and Chronic Phases of Toxoplasmosis in Mice Model

“…Serological techniques such as antibody detection and IgG avidity test have been established to diagnose the acute and chronic toxoplasmosis, but these methods are not specific enough in immunodeficient patients [17][18][19]. Molecular techniques, mostly PCR has been broadly used as a fast, sensitive and specific diagnostic technique in comparison with conventional parasitological and serological methods [20] and different molecular methods have been developed to increase the diagnostic accuracy of the several forms of toxoplasmosis [21,22]. Nested PCR is a modification of PCR intended to reduce non-specific binding in products due to the amplification of unexpected primer binding sites and heighten the specificity of the test.…”