Genetically modified organisms (GMOs), e.g. viral vectors, could threaten
the environment if by their release they spread hazardous gene products.
Even in contained use, to prevent adverse consequences, viral vectors
carrying genes from mammals or humans should be especially scrutinized as to
whether gene products that they synthesize could be hazardous in their new
context. Examples of such potentially hazardous gene products (PHGPs) are:
protein toxins, products of dominant alleles that have a role in hereditary
diseases, gene products and sequences involved in genome rearrangements,
gene products involved in immunomodulation or with an endocrine function,
gene products involved in apoptosis, activated proto-oncogenes. For
contained use of a GMO that carries a construct encoding a PHGP, the
precautionary principle dictates that safety measures should be applied on a
“worst case” basis, until the risks of the specific case have been
assessed. The potential hazard of cloned genes can be estimated before
empirical data on the actual GMO become available. Preliminary data may be
used to focus hazard identification and risk assessment. Both predictive and
empirical data may also help to identify what further information is needed
to assess the risk of the GMO. A two-step approach, whereby a PHGP is
evaluated for its conceptual dangers, then checked by data bank searches, is
delineated here.