Biomedical Engineering Reference
In-Depth Information
conditions for gene-based vaccines thus far having entered clinical trials include malaria, hepatitis
B and AIDS.
14.6.2 Gene therapy: some additional considerations
In addition to some technical diffi culties outlined earlier, a number of non-technical issues must
be satisfactorily addressed before its practice becomes widespread. Chief amongst these issues are
the questions of public perception, ethics and costs.
Gene therapy is not, and will not be, an inexpensive therapeutic tool. The cost of such treat-
ments will likely be broadly similar to the cost of present-day biopharmaceuticals. However, if
proven successful in treating many currently incurable conditions, the cost:benefi t ratio will al-
most certainly greatly favour its medical use.
Public perception and ethical considerations are, in some ways, interlinked. The ability to so
readily modify our genetic complement holds great therapeutic promise. However, strict regulations
overseeing the use of this technology are required (and are currently being enforced). Without proper
controls, the danger exists that gene therapy could eventually be used to 'improve' human character-
istics. The technical know-how to underpin a new era of eugenics is now almost a reality. The most
important safeguard aimed at preventing eugenic-type developments is already in place. Currently,
gene therapy is restricted to somatic cells; the genetic manipulation of human germ cells is banned.
Any genetic alterations achieved thus will not be transmitted to future generations. Like many other
technologies, there is no 'going back' in relation to gene therapy. The challenge is to ensure that hu-
man genetic manipulation is used only for purposes that clearly represent the 'common good'.
14.7 Antisense technology
Various disease states are associated with the inappropriate production/overproduction of gene
products. Examples include:
•
the expression of oncogenes, leading to the transformed state;
•
the overexpression of cytokines during some disease states with associated worsening of dis-
ease symptoms;
•
The overproduction of angiotensinogen, - which ultimately results in hypertension.
An additional example includes the intracellular transcription and translation of virally encoded
genes during intracellular viral replication. In all such instances, the medical consequences of such
inappropriate gene (over)expression could be ameliorated/prevented if this expression could be down-
regulated. A nucleic-acid-based approach to achieve just this is termed 'antisense technology'.
The antisense approach is based upon the generation of short, single-stranded stretches of nucleic
acids (which can be DNA- or RNA-based) displaying a specifi c nucleotide sequence. These are
generally termed 'antisense oligonucleotides'. These oligonucleotides are capable of binding to
DNA (at specifi c gene sites) or, more commonly, to mRNA derived from specifi c genes. This
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