Low autocrine interferon beta production as a gene therapy approach for AIDS: Infusion of interferon beta-engineered lymphocytes in macaques chronically infected with SIVmac251.

BACKGROUND: The aim of this study was to evaluate gene therapy for AIDS based on the transduction of circulating lymphocytes with a retroviral vector giving low levels of constitutive macaque interferon beta production in macaques chronically infected with a pathogenic isolate of SIVmac251. RESULTS: Two groups of three animals infected for more than one year with a pathogenic primary isolate of SIVmac251 were included in this study. The macaques received three infusions of their own lymphocytes transduced ex vivo with the construct encoding macaque IFN-beta (MaIFN-beta or with a vector carrying a version of the MaIFN-beta gene with a deletion preventing translation of the mRNA. Cellular or plasma viremia increased transiently following injection in most cases, regardless of the retroviral construct used. Transduced cells were detected only transiently after each infusion, among the peripheral blood mononuclear cells of all the animals, with copy numbers of 10 to 1000 per 106 peripheral mononuclear cells. CONCLUSION: Long-term follow-up indicated that the transitory presence of such a small number of cells producing such small amounts of MaIFN-beta did not prevent animals from the progressive decrease in CD4+ cell count typical of infection with simian immunodeficiency virus. These results reveal potential pitfalls for future developments of gene therapy strategies of HIV infection.

Cellular and gene therapy for major histocompatibility complex class II deficiency.

Major histocompatibility complex (MHC) class II deficiency is a primary immunodeficiency. Lentiviral vectors are used for gene therapy in a mouse model of this disease. In addition, by a direct genetic correction approach, a diagnostic test to determine which of the four MHC II genes is defective in new MHC II-deficiency patients has been optimized.

Direct genetic correction as a new method for diagnosis and molecular characterization of MHC class II deficiency.

Major histocompatibility complex class II (MHCII) deficiency is a primary immunodeficiency resulting from defects in one of four different MHCII-specific transcription factors-CIITA, RFX5, RFXAP, and RFXANK. Despite this genetic heterogeneity, the phenotypical manifestations are homogeneous. It is frequently difficult to establish a definitive diagnosis of the disease on the basis of clinical and immunological criteria. Moreover, the phenotypical homogeneity precludes unambiguous identification of the regulatory gene that is affected. Identification of the four genes mutated in the disease has now allowed us to develop a rapid and straightforward diagnostic test for new MHCII-deficiency patients. This test is based on direct correction of the genetic defect by transduction of cells from patients with lentiviral vectors encoding CIITA, RFXANK, RFX5, or RFXAP. We have validated this approach by defining the molecular defects in two new patients. The RFXANK vector restored MHCII expression in a T cell line from one patient. The RFXAP vector corrected primary cells (PBL) from a second patient. Molecular analysis confirmed the presence of homozygous mutations in the RFXANK and RFXAP genes, respectively. Direct genetic correction represents a valuable tool for the diagnosis and classification of new MHCII-deficiency patients.

Simian immunodeficiency virus resistance of macaques infused with interferon beta-engineered lymphocytes.

To test the in vivo anti-simian immunodeficiency virus (SIV) efficacy of interferon (IFN)-beta-engineered lymphocytes, peripheral blood lymphocytes harvested from two uninfected macaques were transduced with a retroviral vector carrying a constitutively expressed IFN-beta gene and reinfused, resulting in approximately 1 IFN-beta-transduced cell out of 1000 circulating cells. The gene-modified cells were well tolerated and could be detected for at least 74 days without causing any apparent side effects. These two animals together with three untreated control macaques were then infected with SIVmac251. The two IFN-beta-infused macaques are in good health, 478 days after infection, with a reduced plasma virus load and sustained numbers of CD4(+) and CD8(+) cells. Throughout the study, the proportion of IFN-beta-transduced cells has been maintained. Of the three control macaques, two were characterized by a high plasma virus load and a decrease in CD4(+) cells. One was moribund and was sacrificed 350 days after infection and the other now has fewer than 100 circulating CD4(+) cells/ml. Unexpectedly, the third control macaque, which, like the two IFN-beta-infused animals, had a low plasma virus load and a maintenance of CD4(+) and CD8(+) cell number, was characterized by a permanent level of serum IFN-beta, of unknown origin, already present before SIV infection. Although no definite conclusion can be made in view of the limited number of animals, these data indicate that further exploration is warranted of an IFN-beta-based anti-human immunodeficiency virus gene therapy.