Abstract
Purpose :
The presence or generation of neutralizing antibodies (NAbs) against the capsid proteins of gene transfer vectors can limit vector transduction levels and therefore diminish the therapeutic response. We evaluated NAb titers against tyrosine-mutant AAV2 in serum and anterior chamber fluid (ACF) samples of treated Leber’s hereditary optic neuropathy (LHON) patients
Methods :
Self-complementary AAV2 (Y444, 500, 730F)-P1ND4v2 was injected intravitreally into the eyes of 14 LHON G11778A participants. The eye with worse acuity was treated. 8 eyes received low dose vector, LDV (5x109 vg) and 6 medium dose, MDV (2.46x1010 vg). NAbs were assessed in serum and ACF samples. The NAb titer was reported as the highest serum or ACF dilution that inhibited scAAV2-smCBA-mCherry transduction by 〉50%, compared with no serum control. NAb levels were categorized as low (≤80), moderate (≤5120) or high (〉20,480).
Results :
Strong inhibition to mCherry expression in the presence of high NAb levels against AAV2 (〉20,480) were found in serum samples of 4/14 (28.5%) LHON subjects at baseline (bsl), 1d, 7d, 3m, 6m and (or) 1yr postinjection (pi). 7/14 (50%) patients showed absent or low NAbs at bsl and 6 (86%) remained antibody -ve at pi visits. One of the patients with NAb=5 at bsl (recieved LDV), showed a transient rise of NAb to 20 at 7dpi that reduced to bsl levels at 3m and 1ypi. One other patient with NAb=5 at bsl, received MDV and pi (1d and 7d) showed a transient rise of titer =20 at 3mpi. Two other subjects (14%) had moderate NAb levels (〉5120 and 〉320) at bsl, 1d, 7d,3mpi. However, 2/14 (14%) patients developed anterior uveitis that resolved without any treatment. In one of these patients, who received a MDV levels of NAb in the serum rose from 80 at bsl to 20,480 at d7 and remained unchanged at 3m and 1ypi (〉20,480). In the other patient who developed uveitis levels of NAb were high at bsl (20,480) and remained at these levels. Fortunately, anterior uveitis with our gene therapy was asymptomatic, transient and required no treatment. It is unclear whether it was related to NAb. NAb titers in the bsl ACF samples were low or absent in all participants.
Conclusions :
Despite the presence of high NAbs to AAV2 in bsl serum samples of some LHON pateints, the NAb levels detected from ACF were lower. This suggests high serum NAb levels may not be a barrier to successful ocular gene therapy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.