Targeted inhibition of immunodeficiency virus replication in lymphocytes through retroviral mediated gene transfer

Comparative analyses of intracellularly expressed antisense RNAs as inhibitors of human immunodeficiency virus type 1 replication

The antiviral activities of intracellularly expressed antisense RNAs complementary to the human immunodeficiency virus type 1 (HIV-1) pol, vif, and env genes and the 3' long terminal repeat (LTR) sequence were evaluated in this comparative study. Retroviral vectors expressing the antisense RNAs as part of the Moloney murine leukemia virus LTR promoter-directed retroviral transcript were constructed. The CD4+ T-cell line CEM-SS was transduced with retroviral constructs, and Northern blot analyses showed high steady-state antisense RNA expression levels. The most efficient inhibition of HIV-1 replication was observed with the env antisense RNA, followed by the pol complementary sequence, leading to 2- to 3-log10 reductions in p24 antigen production even at high inoculation doses (4 x 10(4) 50% tissue culture infective doses) of the HIV-1 strain HXB3. The strong antiviral effect correlated with a reduction of HIV-1 steady-state RNA levels, and with intracellular Tat protein production, suggesting that antisense transcripts act at an early step of HIV-1 replication. A lower steady-state antisense RNA level was detected in transduced primary CD4+ lymphocytes than in CEM-SS cells. Nevertheless, replication of the HIV-1 JR-CSF isolate was reduced with both the pol and env antisense RNA. Intracellularly expressed antisense sequences demonstrated more pronounced antiviral efficacy than the transdominant RevM10 protein, making these antisense RNAs a promising gene therapy strategy for HIV-1.

Characterization of antisense RNA-mediated inhibition of SIV replication

Antisense RNA-mediated inhibition of HIV showed mixed success in previous experiments. In order to elucidate the parameters influencing the efficacy of an antisense RNA approach, retroviral vectors encoding 4.5 kb, 3.5 kb, or 2.5 kb antisense RNA of the gag-pol region of SIV (simian immunodeficiency virus) were constructed and used to transduce a CD4-positive CEM174 cell line. The growth rate of transduced cells was measured, and results showed that antisense RNAs have no detrimental effect on cell growth. Similar levels of antisense RNA expression were observed in all transduced cells by Northern analysis. The transduced cells were challenged with uncloned SIVmac239 at a m.o.i. (multiplicity of infection) of 1.0, 0.1, or 0.01. At a m.o.i. of 1.0 or 0.1, no significant inhibition of viral replication was observed in any antisense construct transduced cells up to 9 days postinfection. At a lower m.o.i. (0.01), viral replication was effectively inhibited in 3.5 kb antisense transduced cells as compared to 4.5 kb and 2.5 kb antisense transduced cells at 15 days postinfection. These data suggest that the size of antisense RNA and the challenge dose play a significant role in achieving effective inhibition.

Liposomal delivery of oligodeoxynucleotides

We have previously demonstrated that liposome-incorporated methylphosphonate antisense oligodeoxynucleotides (oligos) specific for BCR-ABL can selectively inhibit the expression of p210Bcr-Abl protein and the proliferation of chronic myelogenous leukemia cells in vitro. Here, we show that liposome-entrapment of phosphodiester and phosphorothioate oligos specific for BCR-ABL can also selectively inhibit the proliferation of chronic myelogenous leukemia cells. We have studied the intracellular localization of liposomes by fluorescent microscopy and found that liposomes are readily taken up by leukemic cells and are localized in the cytoplasm, allowing increased access of oligos to target cells intracellularly. Liposomal oligos are not toxic to peripheral blood mononuclear cells nor to bone marrow progenitors isolated from normal hematological donors. These studies strongly suggest that liposomal delivery of oligos may indeed circumvent the major limitations that preclude the clinical development of antisense oligos.

Antiviral therapy for human immunodeficiency virus infections

Depending on the stage of their intervention with the viral replicative cycle, human immunodeficiency virus inhibitors could be divided into the following groups: (i) adsorption inhibitors (i.e., CD4 constructs, polysulfates, polysulfonates, polycarboxylates, and polyoxometalates), (ii) fusion inhibitors (i.e., plant lectins, succinylated or aconitylated albumins, and betulinic acid derivatives), (iii) uncoating inhibitors (i.e., bicyclams), (iv) reverse transcription inhibitors acting either competitively with the substrate binding site (i.e., dideoxynucleoside analogs and acyclic nucleoside phosphonates) or allosterically with a nonsubstrate binding site (i.e., non-nucleoside reverse transcriptase inhibitors), (v) integration inhibitors, (vi) DNA replication inhibitors, (vii) transcription inhibitors (i.e., antisense oligodeoxynucleotides and Tat antagonists), (viii) translation inhibitors (i.e., antisense oligodeoxynucleotides and ribozymes), (ix) maturation inhibitors (i.e., protease inhibitors, myristoylation inhibitors, and glycosylation inhibitors), and finally, (x) budding (assembly/release) inhibitors. Current knowledge, including the therapeutic potential, of these various inhibitors is discussed. In view of their potential clinical the utility, the problem of virus-drug resistance and possible strategies to circumvent this problem are also addressed.

Retroviral Producer Cells Cause Sarcoma in Severe Combined Immunodeficiency Mice

Direct in situ introduction of retroviral producer cells might provide a form of treatment for localized tumors. A possible undesirable consequence of this treatment could be uncontrolled proliferation of the injected producer cells. To test this possibility, severe combined immunodeficiencies (SCID) mice were reconstituted with human peripheral blood lymphocytes which were marked with a retroviral vector using a coculture method. Although specific measures were taken to remove the possible contaminating producer cells, a high percentage of mice developed fibrosarcoma 2-6 weeks after reconstitution. We hypothesized that tumors arose from a small number of contaminating producer cells in the inoculum. Tumor cells were consistently DNA tetraploid, a characteristic of the producer cell line. DNA extracted from tumor tissue was found to contain the gene (neomycin phosphotransferase) used to mark the producer cell line. Furthermore, SCID mice injected with 1 x 10(4) producer cells developed tumors with analogous characteristics. This report indicates that the retroviral producer cell line is tumorigenic in immune-deficient animals. Copyright 1995 S. Karger AG, Basel

Inhibition of human immunodeficiency virus expression by sense transcripts encoding the retroviral leader RNA

Towards gene therapy for the treatment of human immunodeficiency virus type 1 (HIV-1) infections, we tested the potency of several antiviral constructs in transient HIV-1 production assays. Whereas little effect was obtained with antisense- and TAR decoy-constructs, we measured efficient inhibition of HIV-1 mRNA translation and virion production in the presence of HIV-1 leader-containing transcripts. The infectivity of these virions was also reduced by this sense inhibitor RNA. These results suggest that leader-encoded functions, like the dimer-linkage structure, can be used to specifically inhibit HIV expression in trans.