Differential gene expression in response to adjunctive recombinant human interleukin-2 immunotherapy in multidrug-resistant tuberculosis patients

Administration of low-dose recombinant human interleukin 2 (rhuIL-2) in combination with multidrug chemotherapy to patients with multidrug-resistant tuberculosis (MDR TB) induces measurable changes in in vitro immune response parameters which are associated with changes in the clinical and bacteriologic status of the patients. To determine the molecular basis of these changes, we have used semiquantitative reverse transcriptase-initiated PCR (RT-PCR) and differential display technology. During rhuIL-2 treatment of MDR TB patients, decreased levels of gamma interferon (IFN-γ) mRNA in peripheral blood mononuclear cells (PBMC) relative to baseline levels were observed. However, at the site of a delayed-type hypersensitivity (DTH) response to purified protein derivative of tuberculin (PPD), the expression of cellular IFN-γ and IL-2 mRNAs was increased during rhuIL-2 therapy. Levels of other cytokine mRNAs were not significantly affected by rhuIL-2 administration. Using differential-display RT-PCR, we identified several genes expressed at the DTH skin test site which were up- or down-regulated during rhuIL-2 treatment. Cytochrome oxidase type I mRNA was increased in response to rhuIL-2 therapy relative to baseline levels, as was heterogeneous nuclear ribonuclear protein G mRNA. CD63, clathrin heavy chain, and β- adaptin mRNAs, all of which encode proteins associated with the endocytic vacuolar pathway of cells, were also differentially regulated by rhuIL-2 administration. The differential effects of IL-2 were confirmed in vitro by using PBMC obtained from PPD-positive individuals stimulated with Mycobacterium tuberculosis and IL-2. The differential expression of genes may provide a surrogate marker for leukocyte activation at a mycobacterial antigen-specific response site and for the development of an enhanced antimicrobial response which may result in improved outcomes in MDR TB patients.