Abstract
Purpose :
Neutralizing antibodies (NAb) against AAV, could interfere with the recombinant AAV vector-mediated gene transfer, thus decreasing the efficiency of the vector administered. We evaluated NAb titers against tyrosine-mutant AAV2 in LHON patients before and after gene therapy injections.
Methods :
Self-complementary AAV2 (Y444, 500, 730F)-P1ND4v2 was intravitreally injected into the eyes of 9 LHON G11778A participants. The eye with worse acuity was treated. Six of them received low dose vector (5x109vg) and three medium dose (2.46x1010vg). NAbs were assessed in serum and anterior chamber fluid (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 :
Serum Results. Strong inhibition to mCherry expression due to high NAbs against AAV2 (>20,480) were found in serum samples of 4/9 (44%) LHON subjects at baseline, 1d, 7d, 3m, 6m and (or) 1yr postinjection (pi). 3 patients showed absent or low NAbs at baseline (33.3%). One of these patients with NAb=5 at baseline and received a low dose vector showed a transient rise of NAb to 20 at 7dpi, however NAbs decreased to baseline at 3 mpi. Another patient with NAb=80 at baseline, who received a medium dose showed a moderate increase at 1dpi to 320 and a further rise to higher levels at 7dpi (>20,480). At 2mpi this patient developed uveitis in the injected eye that subsided at 3m, however the serum NAb titer remained unaltered. In the third patient, the NAb titer was low to absent (=5) at baseline and did not change postinjection. One of the 4 patients who had high NAbs and received low dose vector also showed uveitis 2mpi. Two other subjects (22.2%) had moderate NAb levels (>5120 and >320) at baseline, 1d, 7d and 3mpi. ACF Results. NAbs in all the baseline ACF samples were absent or mild.
Conclusions :
Despite the presence of high NAbs to AAV2 in baseline serum samples of LHON participants, the NAb levels detected from ACF were lower, suggestive of high serum NAb levels may not be a barrier to successful ocular gene therapy. Transient uveitis developed in the treated eyes of two patients, might be due to immunopathogenic response to the P1ND4v2 AAV2.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.