PTM of AAV capsids

Figure 5

The titers of pre-existing antibodies are not affected by deamidation. Anti-AAV9 antibodies were detected in 16 human serum samples. WT or deamidated AAV9 capsids were coated passively onto a plate, serum samples were then added after blocking, and pre-existing antibodies were detected using a colorimetric reaction involving anti-human FC-HRP antibodies and TMB substrate. A titer was calculated by subtracting the signal from the sham ELISA and then interpolating the point where there is no longer change in OD signal in the reciprocal dilutions. (A) Anti-AAV titer against WT or deamidated (mutated) capsids in 16 healthy individuals. (B) Data were divided into 3 groups based on titer against WT capsids, then were compared to titer against mutated capsids. WT<De indicates that the titer against deamidated (mutated) capsids is more than 20% higher than the titer against WT capsids. WT<De indicates that the titer against deamidated (mutated) capsids is more than 20% lower than titer against WT capsids.

The use of adeno-associated virus (AAV) as delivery vectors for cancer, genetic disorders, in vivo gene editing and infectious diseases treatment. However, concerns over the immunogenicity of the AAV capsid in humans were raised in clinical trials limiting the therapeutic success of some FDA regulated products.

AAV vectors have been shown to engage both the innate and adaptive arms of the immune system with direct and indirect impact on the safety and efficacy of the gene therapy

This paper by Bing et al. shows that naturally occurring in vivo deamidation of AAV9 capsid residues results in inhibition of T cell cellular responses and discusses experimental approaches to limit the risk of reporting false negative data.