Figure 1

Targeted mutation of S/T/K residues on AAV capsid. Following cellular internalization of AAV by receptor-mediated endocytosis, it travels through the cytosol, undergoes acidification in the endosomes before getting released. Post endosomal escape, AAV undergoes nuclear trafficking, where uncoating of the viral capsid takes place resulting in release of its genome and induction of gene expression (a) S/T/K residues are potential sites for phosphorylation and subsequent poly-ubiquitination which serves as a cue for proteasomal degradation of capsid proteins. This prevents trafficking of the vectors into the nucleus to express its transgene leading to low gene expression. Also, the proteasomally degraded capsid fragments can be presented by the MHC-Class I molecules on the cell surface for CD8 + T-cell recognition. This leads to immune response thus destroying the transduced cells and further reducing persistent transgene expression. (b) Point mutations, S/T to A and K to R, prevents/reduces phosphorylation sites on the capsid. This leads to reduced ubiquitination and proteosomal degradation allowing more number of intact vectors to enter nucleus and express the transgene. Preventing/lowering the overall capsid degradation also reduces antigen presentation to T cells resulting in lower host immune response against the vectors. ub- ubiquitination, p- phophorylation.