Practice question

Recombinant AAV produced by triple transfection HEK293 cells with plasmids encoding rep/cap removed from vector, adenoviral helper functions E2A E4 VA RNA, and vector genome flanked by ITRs yields particles depleted viral coding sequences that normally generate PAMPs triggering innate and adaptive immunity. Capsid proteins VP1 VP2 VP3 ratio 1:1:10 from serotypes AAV2 AAV5 AAV9 exhibit low TLR2 mediated NF-kB activation and minimal TLR9 stimulation due to CpG depletion via codon optimization resulting reduced type I interferons, TNF-alpha, IL-12. Consequently transduced hepatocytes, muscle fibers, dorsal root ganglia display prolonged persistence without CTL elimination although capsid-specific CD8 cells can occur at high doses. Humoral neutralizing antibodies predominantly preexisting limits redosing but allows primary treatment. Episomal concatemers persist as circular monomers multimers associated with histones providing transcriptionally active chromatin for years minimal genotoxicity due low random integration <0.1 percent. Favorable immunological profile underpins licensure hemophilia factor IX Padua and SMA SMN1 replacement using AAV where repeat dosing limited mainly by humoral immunity rather than cellular toxicity.