I don't know a lot about microbiology and virology, and I'm pulling my hair out on a problem about rAAV production and quality assessment.
So, here's my problem : i've been reading several articles, they all assess the quality of their rAAV preparation by various methods (but most commonly, dot blot, real time qPCR, infectious center assay or fluorescence cell assay). And they give ratio that I'm not sure how to interpret (I should mention that one important information that i need to find, is the proportion of full particles vs empty capsids in the preparation - it's been a huge problem in rAAV-based therapy since empty capsids account for up to 90% of the prep and are highly immunogenic. Several scalable methods are currently developed to remove empty capsids and i want to compare them).
So, according to you, what is the difference between :
- P/I ratio (particle to infectivity ratio) : is it the ratio of particles (whether they are full or empty) over infectious virus ? Does it mean that a full particle, with packaged genome, is not necessarily infectious ?
- physical particle titer/infectious titer ratio : isn't the infectious titer the same as the infectivity ? does "physical particle titer" stand for "full particle" ?
Hope some of you can help me see this more clearly