hOKSiM adenovirus

The hOKSiM adenovirus is a replication-deficient human adenovirus type 5 (Ad5; dE1/E3) vector, genetically engineered to express four classic human reprogramming factors—Oct4 (POU5F1), Klf4, Sox2, and c-Myc—under the control of a cytomegalovirus (CMV) promoter. These four open reading frames are arranged in a single transcript and separated by 2A self-cleaving peptides and internal ribosome entry sites (IRES), ensuring efficient expression of each protein from a single promoter while minimizing the need for multiple independent viral vectors. By deleting the E1 gene to render the vector replication-incompetent and deleting the E3 gene to increase payload capacity, this vector can accommodate the polycistronic expression cassette and provides robust and transient expression without genomic integration, a hallmark feature of the adenovirus system. This design leverages Ad5''s broad tropism and high transduction efficiency in various human somatic cell types, as well as its ability to express in both dividing and non-dividing cells, enabling coordinated and temporally controlled delivery of the OKSM factors.

In practice, the hOKSiM adenovirus is used to induce pluripotency in human somatic cells, generating induced pluripotent stem cell (iPSC) lines free of genomic integration traces for research applications. Because Ad5 does not integrate into the host genome, iPSCs generated using this method are attractive for studies where genomic integrity is crucial, such as modeling monogenic diseases, complex traits, and age-related diseases in a patient-specific context. The coordinated expression of Oct4, Klf4, Sox2, and c-Myc from a single expression cassette supports the synchronous delivery of the reprogramming network, which facilitates comparisons between different cell types and improves experimental reproducibility compared to multi-vector systems. Beyond de novo iPSC generation, hOKSiM can also be used for transient, temporally controlled perturbation of cell identity, including exploratory work in partial reprogramming, cell regeneration biology, and lineage plasticity studies where persistent genomic integration is undesirable.