Inhibition of human immunodeficiency virus replication in a human T cell line by antisense RNA expressed in the cell

Behind the scenes of HIV-1 replication: Alternative splicing as the dependency factor on the quiet

Alternative splicing plays a key role in the HIV-1 life cycle and is essential to maintain an equilibrium of mRNAs that encode viral proteins and polyprotein-isoforms. In particular, since all early HIV-1 proteins are expressed from spliced intronless and late enzymatic and structural proteins from intron containing, i.e. splicing repressed viral mRNAs, cellular splicing factors and splicing regulatory proteins are crucial for the replication capacity. In this review, we will describe the complex network of cis-acting splicing regulatory elements (SREs), which are mainly localized in the neighbourhoods of all HIV-1 splice sites and warrant the proper ratio of individual transcript isoforms. Since SREs represent binding sites for trans-acting cellular splicing factors interacting with the cellular spliceosomal apparatus we will review the current knowledge of interactions between viral RNA and cellular proteins as well as their impact on viral replication. Finally, we will discuss potential therapeutic approaches targeting HIV-1 alternative splicing.

Inhibition of human immunodeficiency virus type 1 by packageable, multigenic antisense RNA

Viral-based vectors can provide an efficient delivery mechanism for stable expression of antisense RNA. To enhance and propagate the antiviral effect of antisense RNA, two novel human immunodeficiency virus type 1 (HIV-1)-based vector DNAs, designated as pMAG7 and pMAG19, were constructed which contained HIV-1 cis-acting packaging elements and produced multigenic HIV-1 antisense RNA that could target the entire pol, env, vif, vpu, vpr, rev, and tat and portions of gag and nef. The two DNAs were identical except that pMAG19 had additional gag coding sequences. Cotransfection of pMAG DNA and infectious, cloned HIV-1 DNA in 293 cells inhibited virus production (81%-98% reduction in reverse transcriptase activity) of various T cell-tropic and macrophage-tropic clade B isolates, such as NL4-3, YU-2, and JR-CSF. In addition, virion-associated pMAG antisense RNA was detected in residual virus particles produced by pNL4-3 in the presence of pMAG7 DNA, and the antisense sequences were stably transferred by infection of 174 x CEM cells. The results suggest that pMAG DNA may confer broad protection against HIV-1 by reducing initial virus burden due to antisense RNA and subsequent virus spread by propagation of antisense sequences along with wild-type virus.

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.

A new antisense tRNA construct for the genetic treatment of human immunodeficiency virus type 1 infection

Different strategies proposed in the literature to attempt gene therapy of AIDS are based mainly on the intracellular production of RNA and protein therapeutics. This report describes the construction and the anti-human immunodeficiency virus type 1 (HIV-1) activity of a new type of antisense tRNA directed against a nucleotide region in the first coding exon of HIV-1 tat (nucleotides 5924 to 5943; Los Alamos data bank) which is conserved among many HIV-1 clones. The anti-tat antisense sequence was inserted into a tRNA(Pro) backbone by replacement of the anticodon loop, without altering the tRNA canonic tetraloop structure. The antisense tRNA was able to interact effectively with its target in vitro. Jurkat cells that constitutively expressed the anti-tat tRNA following retroviral vector transduction exhibited significant resistance to HIV-1 de novo infection. Resistance seemed to correlate with the level of antisense expression. This is the first time that such a tRNA antisense strategy has been shown to be effective as a genetic treatment of HIV-1 infection in tissue culture. The construct design proposed in this report has some intrinsic advantages: the transcript is driven by a polymerase III promoter, the short length of the RNA minimizes effects of intramolecular base pairing that may impair target recognition, and the antisense RNA has the stability and intracellular fate of a native tRNA molecule.

Further evaluation of soluble CD4 as an anti-HIV type 1 gene therapy: demonstration of protection of primary human peripheral blood lymphocytes from infection by HIV type 1

We previously reported on the construction of retroviral vectors that produce a secreted form of the HIV-1 receptor, T cell antigen CD4 (Morgan et al., AIDS Res Hum Retroviruses 1990;6:183-191). In this article we test the ability of these sCD4-expressing retroviral vectors to protect human T-cell lines or primary T cells from HIV-1 infection. To demonstrate that protection from HIV-1 infection is mediated by the soluble nature of this protein, two coculture protection experiments were conducted. In these experiments, sCD4-expressing retroviral vectors were used to engineer mouse NIH 3T3 cells. In one coculture experiment the human SupT1 cell line was added directly to the culture of sCD4-producing NIH 3T3 cells, and in another experiment the two cell types were separated physically by a semipermeable membrane. In both coculture configurations, the T cell line was protected from HIV-1 challenge as measured by syncytium formation and indirect immunofluorescent assays. In addition, the SupT1 line was directly engineered with sCD4-expressing retroviral vectors and shown to be protected from HIV-1 challenge. As a prelude to further preclinical studies, we tested the ability of retroviral vectors to transduce primary human peripheral blood lymphocytes (PBLs). Conditions used to stimulate T cell growth resulted in significant shifts in the CD4/CD8 cell in favor of CD8 cells. Retroviral-mediated gene transfer under these conditions resulted in low levels of gene transfer (< 5%).(ABSTRACT TRUNCATED AT 250 WORDS)

The mycoplasma-related inhibitor of HIV-1 reverse transcriptase has a DNase activity and is present in the particle-free supernatants of contaminated cultures

Drastic inhibition of the human immunodeficiency virus (HIV) reverse transcriptase (RT) by mycoplasma has been noted in many laboratories causing confusion in data interpretation. The mycoplasma-related inhibitor of HIV-1 RT was identified as a soluble protein in the particle-free supernatant of a contaminated culture. Gel filtration studies revealed the molecular mass of this protein to be about 70 kDa. This RT-inhibitor contained a DNase with strong activity on both linear and circular DNAs. Addition of this inhibitor after completion of reverse transcription still reduced the final outcome of the RT assay significantly, implying that the inhibitory mechanism occurred mainly by its DNase activity. Treatment of the culture with an antimycoplasma drug cured the mycoplasma contamination, removed the RT-inhibitor and abolished the DNase activity.

Antisense treatment of viral infection

In this chapter I have attempted to outline the rationale that underlies the antisense approach to treatment of virus infection, to catalog the effector molecules that are currently available, and to estimate the relative worth of each. In so doing I have tried to describe the criteria that might be employed in their design and the factors that may determine their efficacy in tissue culture and, perhaps, in vivo. Finally, I have described the few examples presently available that indicate that antisense approaches may one day be therapeutically useful in treatment of disease of viral or nonviral origin.

Generation and characterization of a human immunodeficiency virus type 1 (HIV-1) mutant resistant to an HIV-1 protease inhibitor

A synthetic peptide, RPI 312, that specifically inhibits the protease of the human immunodeficiency virus type 1 (HIV-1) showed a potent inhibition on virus production, maturation, and infectivity. Treatment with this agent prevented the cleavage of Gag protein at the site between p17 and p24 in HIV-1 chronically infected MOLT-4 cells as well as in the released virus. Passage of HIV-1 in the presence of gradually increasing concentrations of this protease inhibitor resulted in emergence of a variant that could evade the drug effects. In the resistant variant the maturation of Gag proteins appeared normal, but its infectivity was reduced compared with that of the parent virus. The nucleotides coding the amino acids at and around the cleavage site between Gag proteins p17 and p24 were not changed. One point mutation (A-->G) at site 2082 of the pol gene that resulted in one amino acid change at site 84 of the protease from isoleucine to valine (I-84-->V) could be detected in the resistant variant. An HIV-1 infectious DNA clone with the I-84-->V mutation also showed reduced sensitivity to this protease inhibitor. The findings that the resistant variant had lower infectivity and was still affected by higher doses of the drug support the speculation that resistance to protease inhibitors may not be as problematic as other drug resistance.

In vitro modification of human immunodeficiency virus type 1 (HIV-1) infectivity by the U937 cells

The effect of host cell factors on infectivity of human immunodeficiency virus type 1 (HIV-1) was studied by infecting a monoblastoid cell line (U937) or a T-cell line (MOLT-4) with a highly infective single clone of HIV-1 and comparing the infectivity of the produced viruses to different cell lines. Chronically infected U937 cells consistently produced viruses with minimal infectivity. This phenotypic change was host-dependent as the back-passage of the U937-produced low infective viruses into MOLT-4 cells resulted in regaining their original high infectivity. Southern and Northern blot analyses of the HIV-1 grown in U937 cells did not reveal any genomic difference between it and the virus grown it MOLT-4 cells. The radioimmunoprecipitation analysis of viral proteins showed that the HIV-1-infected U937 cells had a different pattern of envelope glycoproteins and core proteins, which well correlated with the low infectivity of the produced viruses. This experimental system using MOLT-4 and U937 cell lines would be useful to further explore host cell factor(s) which play an important role in the regulation of HIV-1 infectivity.