DRAQ5 for FISH counterstaining intracellular pathogens

In this new work to determine the role of purines in innate immunity a group led by scientists at UCSD used C elegans orthologs of enzymes human purine salvage pathway. 

In one aspect of this work they also treated HUVECs with concentrations of deoxyadenosine with and without anti-IFN antibody and then infected the cells with the intracellular parasite E. intestinalis.

DRAQ5 was used as counterstain for FISH on the HUVEC cells. The analysis contained E. intenstinalis 16S rRNA probe tagged with Quasar 570 chromophore (DsRed channel), Calcofluor White to detect bacterial cell wall (DAPI channel)

DRAQ5 to label nuclei (Cy5 channel).  The data were then used to quantify any significant impact on the infection load in the cells according to the dose of deoxyadenosine, as a measure of enhanced innate immunity.

Due to Calcofluor White's emission being in the DAPI channel DRAQ5 was chosen as DNA counterstain for these FISH experiments, showing its ideal utility for experiments to study intracellular parasitic infections since there is also great value in combining the FISH labeling with Calcafluor White's ability to label the prokaryotic cell wall. 

Reference:
Wernet, N.D., Tecle, E., Sarmiento, M.B., Kuo, C.-J., Chhan, C.B., Baick,
I., Batachari, L.E., Franklin, L., Herneisen, A., Bhabha, G., Ekiert, D.C., Hanna-Rose, W., Troemel, E.R.
Adenosine deaminase and deoxyadenosine regulate intracellular immune response in C. elegans.
ISCIENCE (2025), DOI: https://doi.org/10.1016/j.isci.2025.111950.