Low Seroprevalence of Neutralizing Antibodies Targeting Two Clade F AAV in Humans.

Abstract

To assess the therapeutic utility of AAVHSC15 and AAVHSC17, two recently described Clade F adeno-associated viruses, the seroprevalence of neutralizing antibodies to these AAVs was assessed in a representative human population and compared to that of AAV9. Neutralizing antibody levels were measured in 100 unique human sera of different races (34:33:33, Black:Caucasian:Hispanic) and sex (49% Female, 51% Male) collected within the United States. Fifty-six sera were tested in HuH7 cells and 44 sera were tested in 2V6.11 cells with vectors packaged with either a CMV-promoter upstream of LacZ or a CBA-promoter upstream of Firefly Luciferase, respectively. For AAVHSC15, AAVHSC17, and AAV9, 24/100 (24%), 21/100 (21%), and 17/100 (17%), respectively, of all sera tested were seropositive for neutralizing antibodies using 50% inhibition of cellular transduction at a 1/16 dilution of serum as cut-off for seropositivity. Only six percent of positive sera had titers of 1/150 to 1/340 indicating that the majority of positive sera were of low titer. Significant cross-reactivity of neutralizing antibodies across all three AAV serotypes was observed. These data show that approximately 80% of humans evaluated were seronegative for pre-existing neutralizing antibodies to the AAV serotypes tested, suggesting that the vast majority of human subjects would be amenable to therapeutic intervention with Clade F AAVs.