Dear Lucia,

I don't think anybody has taken the effort of figuring out exactly what causes this. It is a very well known phenomenon. I have heard many people refer to it as autofluorescence. It usually shows up in all frequency bands, i.e. you see it with all filters.

The less damage you do to the tissue, smallest gauge needle, slowest possible injection speed etc., the less background you will get. Mostly people just ignore the tissue around the injection site.

I hope this helps

Nils

I guess people have already verified this, but you could try to inject empty vectors and vectors with some other construct. If you think that the immunogenicity is driven by the construct, you should have your answer like this. I'm quite convinced that the inflammation is driven mainly by the AAVs and by the injection itself, as mentioned above. Maybe, you could try to use backtracing viruses and inject a target area, if you are really interested in the area that you have previously injected.

Hope it helps, good luck!

Thanks. We routinely do control injections, with GFP or luciferase as the transgenes, and we don't get the same reaction. I was just wondering whether there is a way of actually defining what is going on.

That's interesting. You have already done more than most people to figure out what is going on. So you can already state that it is your transgene that is the cause. My hypothesis would be that the transgene is causing more cell stress and death. you could stain for GFAP, apoptosis markers or do silver staining. The latter stains for dying/dead cells that did not die through apoptosis.

good luck

Nils

PS if you ever figure out what is going on I would greatly appreciate an update.