310. Analysis of AAV5 Biodistribution and Viral Shedding in the Presence or Absence of Neutralizing Antibodies

Abstract

Neutralizing antibodies (NAbs) are the main obstacle that must be overcome to achieve a successful delivery of a viral vector to the target organ. NAbs acquisition can be induced naturally after infection with wild type AAV or after the first administration of AAV vector in the course of gene therapy treatment. Therefore, the objective of this project was to evaluate the efficacy and presence of the vector in the organism, as well as the response and vector elimination in the presence and absence of NAbs. We analyzed the presence of the reporter transgene (hFIX), humoral and cellular immune responses against the vector, viral shedding and biodistribution. The administration of AAV2/5 was successful in absence of NAbs. In contrast, vector administration in presence of specific NAbs was unsuccessful, probably due to the vector being completely depleted by anti-AAV2/5 NAbs. Our data demonstrate that while in the absence of antibodies the vector can be detected in serum and in other body fluids for 70 days after vector administration, the presence of antibodies immediately clears the vector from the organism. 24 hours after the AAV-hFIX administration 1X1008 gc/mL are detected in the serum in the absence of NAbs but in the presence of NAbs the concentration is reduced 1000-fold. In both groups the presence of NAbs increased upon infection without a cellular immune response against the vector. Finally, the biodistribution studies showed remarkable differences between the two groups: in the absence of NAbs vector genomes are detected mainly in liver, heart, spleen and inguinal LN, while in the presence of NAbs vector genomes are almost undetectable in all tissues analyzed.