In this vein, we present CTLAP, a fluorogenic probe that is rapidly activated by CTL and displays good selectivity over CTB and CTV, the closest competing analytes for CTL activity probes. CTLAP exhibits intrinsically low background fluorescence, which we attribute to the notably low quantum yield measured for the probe. CTLAP demonstrates markedly higher turn-on ratios (24-fold) and moderately improved enzyme selectivity (6- to 10-fold) when compared to Z-FR-AMC (10-fold turn-on ratio, 6- to 7-fold selectivity), a commercially available CTL-selective probe commonly used to detect CTL activity in mixed samples. Optimum selectivity for CTL is achieved within 10 min of incubation with the enzyme, suggesting that CTLAP is amenable for rapid detection of CTL, even in the presence of competing cathepsins.

The present disclosure describes methods and systems for use in the production of adeno-associated virus (AAV) particles, including recombinant adeno-associated virus (rAAV) particles. In certain embodiments, the production process and system use Baculoviral Expression Vectors (BEVs) in the production of AAV particles. In certain embodiments, the production process and system use Spodoptera frugiperda insect cells (such as Sf9 or Sf21) as viral production cells. In certain embodiments, the production process and system use BEVs which lacks a portion or an entirety of the v-cath gene or includes a mutationally inactivated version of the v-cath gene.