51 Essays on Infinite Lifespans   João Pedro de Magalhães ingless when compared to the three billion base pairs of the human genome. Maybe it is possible to use a combination of viruses but there are other problems. Viral vectors can stably integrate the desired gene into the target cell’s genome but the gene’s integration may occur at oncogenes (cancer-inducing genes), causing cancer. An immune response against viruses or transgenes may also occur and could be fatal as in the famous case of Jesse Gelsinger. [14] Virus-based gene therapy does not appear adequate to cure aging for not only is its safety dubious but the amount of genetic information viruses can carry is insufficient. In addition to viruses, it has also been proposed that cer- tain bacteria can act as vectors in gene therapy – the major advantage being that bacteria can transport larger amounts of information and still be able to change the genome. [15] As with viral-induced gene therapy, the immune response is a major problem. Some promising results have emerged from cancer treatments [16] but it is dubious bacterial-based vec- tors can become a solution to aging within a near future due to safety concerns. If gene therapy can be used to express certain genes, RNA interference or RNAi can be used to inactivate them. Tiny double-stranded molecules of RNA can be designed to block a given target gene. [17] For example, it has been proposed that blocking the action of the gene responsible for Huntington’s disease may prevent the onset of this disease. RNAi can be seen as another type of information vector used to transmit information to the body. Of course there are limitations, but if specific genes have to be turned off at specific times to cure aging, RNAi appears a viable solution. For instance, onco- genes appear to be activated during aging. For these, RNAi and ‘classical’ single-molecule-based pharmaceutical interven- tions [18] appear a viable solution.