biostudies-literatureLi CNIDDK NIH HHSNIAID NIH HHSNCI NIH HHSNIAMS NIH HHS1390-401https://www.ebi.ac.uk/biostudies/studies/S-EPMC3582142biostudies-literatureUnknown123(3)Adeno-associated virus (AAV) vectors are attractive for gene delivery-based therapeutics, but data from recent clinical trials have indicated that AAV capsids induce a cytotoxic T lymphocyte (CTL) response that eliminates transduced cells. In this study, we used traditional pharmacological agents and AAV mutants to elucidate the pathway of capsid cross-presentation in AAV-permissive cells. Endosomal acidification inhibitors blocked AAV2 antigen presentation by over 90%, while proteasome inhibitors completely abrogated antigen presentation. Using mutant viruses that are defective for nuclear entry, we observed a 90% decrease in capsid antigen presentation. Different antigen presentation efficiencies were achieved by selectively mutating virion nuclear localization signals. Low antigen presentation was demonstrated with basic region 1 (BR1) mutants, despite relatively high transduction efficiency, whereas there was no difference in antigen presentation between BR2 and BR3 mutants defective for transduction, as compared with wild-type AAV2. These results suggest that effective AAV2 capsid antigen presentation is dependent on AAV virion escape from the endosome/lysosome for antigen degradation by proteasomes, but is independent of nuclear uncoating. These results should facilitate the design of effective strategies to evade capsid-specific CTL-mediated elimination of AAV-transduced target cells in future clinical trials.The Journal of clinical investigationAdeno-associated virus capsid antigen presentation is dependent on endosomal escape.PMC3582142P30 CA016086R01 AI0807261R01AI080726U54 AR056953R01 AI072176R01 DK0840335R01DK0840335R01AI0721765U54AR056953Li CHe YSamulski RJKafri THirsch MWeinberg MSNicolson SZhang PfalseAdeno-associated virus capsid antigen presentation is dependent on endosomal escape.Adeno-associated virus (AAV) vectors are attractive for gene delivery-based therapeutics, but data from recent clinical trials have indicated that AAV capsids induce a cytotoxic T lymphocyte (CTL) response that eliminates transduced cells. In this study, we used traditional pharmacological agents and AAV mutants to elucidate the pathway of capsid cross-presentation in AAV-permissive cells. Endosomal acidification inhibitors blocked AAV2 antigen presentation by over 90%, while proteasome inhibitors completely abrogated antigen presentation. Using mutant viruses that are defective for nuclear entry, we observed a 90% decrease in capsid antigen presentation. Different antigen presentation efficiencies were achieved by selectively mutating virion nuclear localization signals. Low antigen presentation was demonstrated with basic region 1 (BR1) mutants, despite relatively high transduction efficiency, whereas there was no difference in antigen presentation between BR2 and BR3 mutants defective for transduction, as compared with wild-type AAV2. These results suggest that effective AAV2 capsid antigen presentation is dependent on AAV virion escape from the endosome/lysosome for antigen degradation by proteasomes, but is independent of nuclear uncoating. These results should facilitate the design of effective strategies to evade capsid-specific CTL-mediated elimination of AAV-transduced target cells in future clinical trials.2013-01-01T00:00:00Z2013 Mar2025-04-25T22:00:31.989Z2019-03-27T01:05:16ZS-EPMC35821422345477210.1172/jci6661110.1172/JCI66611