Evaluation of Nested PCRs targeting the BI and SAG2 Genes For Detection of Toxoplasma gondii Genome in Aqueous Humor From HIV Positive Toxoplasma Retinochoroiditis Patients in a Tertiary Eye Hospital

Abstract: Problem statement: To evaluate nPCR targeting B1 gene (primer set 1) with 3 other nPCRs targeting B1 gene (primer set 2), 3' end of SAG2 and 5' end of SAG2 gene, for detection of Toxoplasma gondii (T. gondii) genome on AH from HIV positive TRC patients. Approach: DNA extracted from AH of 12 TRC patients and 12 controls (patients with ocular inflammation of non-Toxoplasma origin) were subjected to all the 4 nPCRs. Results: Toxoplasma gondii genome was detected by atleast one of the 4 nPCRs in 8 (66%) of 12 TRC patients and in none of the 12 controls. nPCR targeting B1 gene (primer set 1) was positive in 6, B1 gene (primer set 2) in 2 and both 3'end of SAG2 and 5' end of SAG2 in 4 respectively. The sensitivity of B1 gene (primer I) was higher compared to the other 3 nPCRs (Yates correction-Chi square test; p = 0.028). Conclusion: Among the 4 nPCRs, nPCR targeting B1 gene (primer set 1) was the most sensitive and reliable nucleic acid amplification technique for the laboratory diagnosis of TRC in HIV patients.