Non-invasive in vivo imaging of transgene expression is
currently providing very important means to optimize gene
therapy regimes. Results in non-human primates are
considered the most predictive models for the outcome in
patients. In this study, we have documented that tumour and
primary cell lines from human and non-human primates are
comparably gene-transduced in vitro by serotype 5 adenovirus
expressing HSV1-thymidine kinase. Transgene expression
can be quantified in human and monkey cultured cells
by positron emission tomography (PET) imaging when
transduced cells are incubated with a fluoride-18 labelled
penciclovir analogue. In our hands, PET images of cell
cultures estimate the number of transduced cells rather than
intensity of transgene expression once a threshold of TK per
cell is reached. Interestingly, in vivo systemic administration
of a clinical grade recombinant adenovirus expressing TK
into macaques gives rise to an intense retention of the
radiotracer in the liver parenchyma, providing an experimental
system to visualize transgene expression that ought
to be similar in human and macaques. Such imaging
methodology might contribute to improve strategies based
on adenoviral vectors
