Quantification of parasite loads in tissues and organs of chronically TcCOL-NLuc-infected mice at 126 dpi by bioluminescence and qPCR.

(A) Luminescence signal quantified for each individual organ/tissue shown in Fig 5 and expressed as radiance (photons/second/cm²/sr). Data represent fold-changes in bioluminescence intensity for organs from infected mice compared to the matching organ from the non-infected control mouse. The detection threshold (grey dashed line) was estimated using the fold-change in radiance for an empty region determined in images taken for the infected mice compared with a matching empty region in images obtained for the infected mouse control. (B) qPCR evaluation of tissue-specific parasite loads. Reactions were conducted using 50 ng of tissue DNA isolated from four TcCOL-NLuc- infected mice and one non-infected mouse. T. cruzi-specific threshold cycle (Ct) values were converted to inferred numbers of parasite equivalents by reference to a standard curve with a range of 1 x10⁴ to 1 x10^-2 parasite equivalents/50 ng of tissue DNA. The IL12 p40 genomic region was used as endogenous control to verify that equal amounts of purified DNA were present in all PCR amplifications. Grey dashed lines indicate the limit of detection (1 x10^-2 parasite equivalents). Data represent the median with interquartile range. Statistical differences among tissues were calculated using one-way ANOVA analysis in GraphPad Prism. *: p < 0.05 indicates significant difference with the heart; ns: no significant difference with the heart.