Alpha 1-antitrypsin (alpha 1AT)
deficiency disease is one of the more common hereditary disorders that affects the liver and lung. The
liver disease of alpha 1AT deficiency is generally thought to be caused by the accumulation of an abnormal alpha 1AT
protein in hepatocytes, whereas the
lung disease is thought to be due to a relative lack of the normal
protein in the circulation. Therefore, one possible approach to prevent and treat alpha 1AT disease is to both inhibit the expression of the mutated alpha 1AT gene, and to provide a means of synthesizing the normal
protein. To do this, we designed specific hammerhead
ribozymes that were capable of cleaving the alpha 1AT
mRNA at specific sites, and constructed a modified alpha 1AT
cDNA not susceptible to
ribozyme cleavage.
Ribozymes were effective in inhibiting alpha 1AT expression in a human
hepatoma cell line using a newly developed simian virus (SV40) vector system. In addition, the
hepatoma cell line was stably transduced with a modified alpha 1AT
cDNA that was capable of producing wildtype alpha 1AT
protein, but was not cleaved by the
ribozyme that decreased endogenous alpha 1AT expression. These results suggest that
ribozymes can be employed for the specific inhibition for an abnormal alpha 1AT gene product, the first step in designing a gene
therapy for the disease. The findings also suggest that the novel SV40-derived vector may represent a fundamental improvement in the gene therapeutic armarmentarium.