# CV1 Chimpanzee Adenovirus Efficiently Transduces Mesenchymal Stem and Leukemia Cells: Implications for Cellular Targeting and Vector Tropism

## TL;DR

The study finds that a chimpanzee adenovirus, CV1, efficiently delivers genes to leukemia and stem cells, offering a promising alternative to commonly used human adenovirus vectors.

## Contribution

CV1 is shown to transduce challenging cell types like leukemia and mesenchymal stem cells more effectively than human Ad5 vectors.

## Key findings

- CV1 ChAd demonstrated the highest transduction efficiency in leukemia and mesenchymal stem cells.
- CV1 induced an inflammatory response similar to human Ad5 but without increased toxicity.
- CV1 is a promising alternative vector for gene therapy targeting resistant cell types.

## Abstract

Human Ad5 (HuAd5) is the most commonly used vector for gene therapy. However, pre-existing immunity against HuAd5 in humans can limit its effectiveness. As an alternative vector, in our study, we evaluated twelve chimpanzee-derived adenovirus (ChAd) serotypes for their ability to transduce challenging cell types. In vitro, we assessed transduction efficiency using enhanced green fluorescent protein in human embryonic kidney cells, two leukemic cell lines, and human mesenchymal stem cells. Among the serotypes tested, CV1 demonstrated the highest transduction efficiency across leukemia and mesenchymal stem cells. In vivo, CV1 induced an inflammatory response comparable to HuAd5, with no evident increase in toxicity. These findings suggest that CV1 is a promising candidate for gene therapy, offering efficient transduction of cells resistant to HuAd5 and a safety profile suitable for further development.

Objectives: Adenoviruses (Ads) are among the most used vectors for gene therapy; human Ad serotype 5-derived (HuAd5) vectors are the most frequently used for gene transfer applications. However, Ad5 infection is endemic in humans, and 20% of the Western population has neutralizing antibodies (nAbs). Pre-existing immunity against HuAd5 represents a major issue for many gene therapy applications. In our study, we evaluated several Ad serotypes derived from chimpanzees (ChAds) in vitro and in vivo to assess their transduction efficiency in various cell types and tissues. We aimed at identifying Ad serotypes able either to transduce “challenging” cell types or to represent a possible alternative to Ad5-derived vectors with comparable infectivity and tropism. Methods: We evaluated the efficacy of transduction of twelve ChAds vectors expressing enhanced green fluorescent protein (EGFP) in human embryonic kidney cells, as well as human leukemic and human mesenchymal stem cells, using flow cytometry to determine the percentage of EGFP-expressing cells and their mean fluorescent intensity (MFI). We observed the highest transduction efficiency in the serotype CV1 ChAd; therefore, we proceeded to evaluate toxicity and biodistribution in vivo. Results: After in vitro evaluation of twelve ChAds serotypes, we observed that the CV1 serotype was the most efficient in transducing both leukemia cell lines (HL-60 and NB-4) and human mesenchymal stem cells. Furthermore, in vivo analysis of the CV1 serotype induced an inflammatory reaction similar to what was observed after HuAd5 administration. Conclusions: ChAds vectors represent an effective alternative for the transduction of cells resistant to HuAd5 infection, such as mesenchymal stem cells and leukemic cells. In addition, we observed that the CV1 ChAd serotype presented a transduction profile similar to HuAd5 in vitro and induced a similar inflammatory response in vivo; therefore, CV1 ChAd-derived vectors represent an interesting alternative for gene therapy applications.