Hi, I am doing CAR-NK research and I have a huge problem with that.

I switching the ecto domain of my CAR (anti FITC ScFv to anti HER2 ScFv).

I analyzed the sequence of CAR and prepare the DNA with high purity and concentration.

Also lentiviral particles seems produced well but there is no positive % observed when I titer my virus. (There is Myc tag between ScFv and trans-membrane domain and I use anti-Myc antibody for titration)

I think the lentivirus production was fine since the amount of virus pellet was similar to the pellet of previous viruses with anti FITC ScFv.

So what I want to ask is, does the ecto-domain of CAR, like ScFv, has effects on CAR display?

Or do I have to change the antigen for a titration? Like using HER2 with fluorescence conjugated?

I look forward to your kind answers.

Thank you.