Diagnosis of Cerebral Toxoplasmosis in AIDS Patients in Brazil: Importance of Molecular and Immunological Methods Using Peripheral Blood Samples

Abstract

Cerebral toxoplasmosis is the most common cerebral focal lesion in AIDS and still accounts for high morbidity and mortality in Brazil. Its occurrence is more frequent in patients with low CD4 ؉ T-cell counts. It is directly related to the prevalence of anti-Toxoplasma gondii antibodies in the population. Therefore, it is important to evaluate sensitive, less invasive, and rapid diagnostic tests. We evaluated the value of PCR using peripheral blood samples on the diagnosis of cerebral toxoplasmosis and whether its association with immunological assays can contribute to a timely diagnosis. We prospectively analyzed blood samples from 192 AIDS patients divided into two groups. The first group was composed of samples from 64 patients with cerebral toxoplasmosis diagnosed by clinical and radiological features. The second group was composed of samples from 128 patients with other opportunistic diseases. Blood collection from patients with cerebral toxoplasmosis was done before or on the third day of anti-toxoplasma therapy. PCR for T. gondii, indirect immunofluorescence, enzyme-linked immunosorbent assay, and an avidity test for toxoplasmosis were performed on all samples. The PCR sensitivity and specificity for diagnosis of cerebral toxoplasmosis in blood were 80% and 98%, respectively. Patients with cerebral toxoplasmosis (89%) presented higher titers of anti-T. gondii IgG antibodies than patients with other diseases (57%) (P < 0.001). These findings suggest the clinical value of the use of both PCR and high titers of anti-T. gondii IgG antibodies for the diagnosis of cerebral toxoplasmosis. This strategy may prevent more invasive approaches.

Non-association between anti-Toxoplasma gondii antibodies and ABO blood group system

“…It is possible that the B antigen exerts a small influence on the adherence of T. gondii to the gastrointestinal mucosa and its contribution is obscured by the high prevalence of infection by these parasites in the Brazilian population, as well as by the molecular variability of its strains identified in Brazilian patients (35)(36)(37)(38). Moreover, the use of only female patients in this study and in the one performed in France might not be sufficient to reveal possible influences of gender in the association of the ABO blood group system with infection by T. gondii (10).…”

The role of MHC haplotypes H2d/H2b in mouse resistance/susceptibility to cyst formation is influenced by the lineage of infective Toxoplasma gondii strain

“…Infection is asymptomatic in most individuals, whereas severe pathology and lethality due to toxoplasmosis is a common finding in congenitally infected or immunodeficient patients (Desmonts and Couvreur 1974). In addition, toxoplasmosis is one of the most common causes of infectious uveitis in both immunocompetent and immunocompromised persons (Holland 1999, Colombo et al 2005. Importantly, some studies indicate that toxoplasmic retinocoroiditis and ocular disease is frequently found in cases of acquired toxoplasmosis (Glasner et al 1992).…”

Importance of high IgG anti-Toxoplasma gondii titers and PCR detection of T. gondii DNA in peripheral blood samples for the diagnosis of AIDS-related cerebral toxoplasmosis: a case-control study

“…5,15 Recently, we reported our experience with conventional PCR assay using peripheral blood samples in patients with AIDSrelated CT, showing a sensitivity of 80% and a specificity of 98%. 7 These very divergent results can be due, at least in part, to several reasons: choice of target DNA and primers, PCR techniques, conditions and time of sample storage, and collection of blood samples before or in the first days after introduction of specific treatment. 5,15,16 It was reported that genotypes of T. gondii strains isolated from patients with ocular toxoplasmosis in Brazil were highly divergent when compared to the previously described clonal lineages from North America and Europe, suggesting more frequent sexual recombinants resulting in mixed genotypes.…”

“…PCR and IFI methodologies were reported elsewhere. 7 For statistical analysis, the outcome variable in the present study was the diagnosis of CT. Univariate logistic regression analysis was performed to identify the independent variables that were associated with the diagnosis of CT. The list of potential variables included age, gender, prior CT, lymphocyte T-CD4+ cell count, use of CT prophylaxis at admission, positive IgG anti-T. gondii IFI, high titers of IgG anti-T. gondii IFI, and a positive PCR result for T. gondii DNA in blood samples.…”