TrkA is targeted by T cruzi for upregulation of NGF in cardiac fibroblasts.

<p><b>A</b>) Antibodies against TrkA, but not against TrkB, TrkC or pan-neurotrophin receptor p75 (p75^NTR) significantly abrogate T cruzi-induced upregulation of NGF on cardiac fibroblasts. Primary cardiac fibroblasts were preincubated with the indicated antibodies (1 µg/ml), infected with T cruzi for 24 h, and the concentration of NGF in the culture overlays determined by ELISA. The results are the mean ± sd of triplicate points and represent the difference between NGF secreted by infected and uninfected cardiac fibroblasts; ***, P<0.001.<b>B</b>) shRNA against TrkA abrogates T cruzi-induced upregulation of NGF on cardiac fibroblasts. Cardiac fibroblasts were transfected with lentivirus encoding shRNA constructs against GFP, TrkA (two distinct vectors), or TrkC (one vector). Seven days later, fibroblasts were infected with T cruzi for 24 h, and NGF content in the culture overlays determined by ELISA. Results are the mean ± SEM of five separate experiments with similar results, and represent the difference between NGF secreted by infected and uninfected cardiac fibroblasts; *, P<0.05, **, P<0.005.