Molecular and Serological Evaluation of Toxoplasmosis in AIDS Cases in Southwest Iran

Background: Toxoplasma gondii has developed as an important opportunistic agent; recent acquired or reactivation of the parasite infection is a serious complication in HIV patients. Since the serological diagnosis may be unreliable in immunodeficient patients who fail to produce considerable titers of antibodies, molecular techniques are also required to detect toxoplasmosis in HIV patients. Objectives: This study was aimed to compare nested PCR assay with serological technique for diagnosis and their capability in determining the prevalence of toxoplasmosis in AIDS cases from southwest Iran. Methods: ELISA and PCR targeting B1 gene were used to analyze blood samples from 379 HIV-positive patients in Khuzestan province, southwest Iran. The amplicons were visualized and sequenced. Results: Out of 379 serum samples, 131 (34.56%) and 11 (2.90%) were positive regarding anti-T. gondii IgG and IgM antibodies, respectively. Of these, 12 samples were IgG+IgM+. Nested PCR results showed that 64 out of 379 (16.88%) of the samples had DNA molecules of the B1 gene. Of these, 63 seropositive samples and only one seronegative specimen were positive by the molecular method. DNA sequencing confirmed these results. In IgG avidity test, 43 (32.82%) and 88 (67.17%) had antibodies indicating the acute and chronic phase, respectively. All 43 samples, with low avidity (100%) and 9 samples of 88 samples with high avidity (10.9%), were positive by molecular method. Conclusions: This study showed a high prevalence of acute and chronic toxoplasmosis in HIV-positive patients and the findings suggested using IgG-avidity test in a condition where PCR testing is impossible, particularly to distinguish recently acquired infection from past infection.