Quantitative estimation of toxoplasma B1gene using real time polymerase chain reaction (PCR) in infected symptomatic and asymptomatic clinical cases

Abstract

Serological diagnosis of active Toxoplasma infection is unreliable because reactivation of latent, 
hidden infection is not always accompanied by changes in antibody levels, and the presence of IgM 
does not necessarily indicate recent infection. Data concerning the relation between the severity of 
infection and the parasitic load especially at human level is limited. A trial was done in this work to 
study the relationship between the virulence of the parasite in different clinical forms and parasitic 
genomic load, via SYBR® Green quantitative PCR amplification assay and primers targeting 
Toxoplasma B1 gene.  Fluorescence signals were generated from 91 samples, which were as follow; 7 
cases with congenital manifestations, 19 cases with neurological disorders, and 65 asymptomatic 
cases.  The seven congenitally infected cases showed significantly higher parasite load (5.15x 108  to 9x 
1010). Other clinical forms showed genomic concentration ranged from 1.7x 104 to 4.1x 108. Equal copy 
numbers of template did not produce equal parameters on derivative melting curve plots. In conclusion, 
quantitative polymerase chain reaction (PCR) provides a sensitive and practical method not only for 
gene quantification, but also for gene scanning by melting curve analysis which is highly recommended 
for different Toxoplasma genes especially those with known pathological functions.