Tissue transglutaminase expression in HIV-infected cells: an enzyme with an antiviral effect?

The cytopathic effect of HIV has been shown to be associated with the induction of apoptosis and the inhibition of proliferation of T cells. However, the cellular and molecular mechanisms at the basis of the dramatic immune cell loss caused by HIV in patients suffering from acquired immunodeficient syndrome (AIDS), are not yet fully established. We demonstrated that "tissue" transglutaminase (tTG) gene expression is induced in the immune system of seropositive individuals (peripheral blood mononuclear cells and lymph nodes). tTG is a multifunctional protein involved in a variety of fundamentally important cellular functions, in addition to cell death by apoptosis. The presence of high tTG levels in immune-competent cells of HIV+ persons might exert an important role in HIV-infection by influencing viral production. We propose that, in addition to its multiple functions, tTG might interfere with HIV replication by altering the viral mRNA trafficking between the nucleus and the cytoplasm. This effect might be due to its specific interaction with eIF5A, a cellular partner of HIV Rev protein, which is essential for HIV replication in immune-competent cells. Given the presence of high tTG levels in HIV+ individuals, it would be of interest to pursue the potential role of this multifunctional protein in the development of strategies aimed at the pharmacologic regulation of HIV production.