Neutralizing antibodies directed against adeno-associated virus (AAV) are commonly found in humans. In seropositive subjects, vector administration is not feasible as antibodies neutralize AAV vectors even at low titers. Consequently, a relatively large proportion of humans is excluded from enrollment in clinical trials and, similarly, vector redosing is not feasible because of development of high-titer antibodies following AAV vector administration. Plasmapheresis has been proposed as strategy to remove anti-AAV antibodies from the bloodstream. Although safe and relatively effective, the technology has some limitations mainly related to the nonspecific removal of all circulating IgG.
Here, a team of French researchers from Genethon, the Institute of Myology, Atlantic Gene Therapy and CEA developed an AAV-specific plasmapheresis column which was shown to efficiently and selectively deplete anti-AAV antibodies without depleting the total immunoglobulin pool from plasma. They showed the nearly complete removal of anti-AAV antibodies from high titer purified human IgG pools and plasma samples, decreasing titers to levels that allow AAV vector administration in mice.
These results provide proof-of-concept of a method for the AAV-specific depletion of neutralizing antibodies in the setting of in vivo gene transfer.
