Studies of naturally occurring polymorphisms of the CCR5 gene have shown that deletion of the functional receptor or reduced expression of the gene can have beneficial effects in preventing HIV-1 infection or delaying disease. Because these polymorphisms are found in otherwise healthy people, strategies that aim to prevent or limit expression of CCR5 should be beneficial in the treatment of HIV-1 disease. To test this approach we have developed a CCR5-specific single-chain antibody that was expressed intracellularly and retained in the endoplasmic reticulum. This CCR5-intrabody efficiently blocked surface expression of human and rhesus CCR5 and thus prevented cellular interactions with CCR5-dependent HIV-1 and simian immunodeficiency virus envelope glycoprotein. Intrabody-expressing cells were shown to be highly refractory to challenge with R5 HIV-1 viruses or infected cells. These results suggest that gene therapy approaches that deliver this intracellular antibody could be of benefit to infected individuals. Because the antibody reacts with a conserved primate epitope on CCR5 this strategy can be tested in nonhuman lentivirus models of HIV-1 disease.

CCR5 is the chemokine co-receptor for R5-tropic human immunodeficiency virus type 1 (HIV-1) isolates most often associated with primary infection. We have developed an HIV-1 self-inactivating vector, CAD-R5, containing a CCR5 single-chain antibody (intrabody) gene, which when expressed in T-cell lines and primary CD4 + T cells disrupts CCR5 cell surface expression and provides protection from R5-tropic isolate exposure. Furthermore, CAD-R5 intrabody expression in primary CD4 + T cells supports significant growth and enrichment over time during HIV-1-pulsed dendritic cell-T-cell interactions. These results indicate that CCR5 intrabody-expressing CD4 + T cells are refractory against this highly efficient primary route of infection. CD34 + cells transduced with the CAD-R5 vector gave rise to CD4 + and CD8 + thymocytes in non-obese diabetic (NOD)/ severely combined-immunodeficient (SCID)-human thymus/ liver (hu thy/liv) mice, suggesting that CCR5 intrabody expression can be maintained throughout differentiation without obvious cellular effects. CD4 + T cells isolated from NOD/SCID-hu thy/liv mice were resistant to R5-tropic HIV-1 challenge demonstrating the maintenance of protection. Our findings demonstrate delivery of anti-HIV-1 activity through CCR5 intrabodies in primary CD4 + T cells and CD34 + cell-derived T-cell progeny. Thus, gene delivery strategies that provide a selective survival and growth advantage for T effector cells may provide a therapeutic benefit for HIV-1-infected individuals who have failed conventional therapies.

TL-3 is a protease inhibitor developed using the feline immunodeficiency virus protease as a model. It has been shown to efficiently inhibit replication of human, simian, and feline immunodeficiency viruses and therefore has broad-based activity. We now demonstrate that TL-3 efficiently inhibits the replication of 6 of 12 isolates with confirmed resistance mutations to known protease inhibitors. To dissect the spectrum of molecular changes in protease and viral properties associated with resistance to TL-3, a panel of chronological in vitro escape variants was generated. We have virologically and biochemically characterized mutants with one (V82A), three (M46I/F53L/V82A), or six (L24I/M46I/F53L/L63P/V77I/V82A) changes in the protease and structurally modeled the protease mutant containing six changes. Virus containing six changes was found to be 17-fold more resistant to TL-3 in cell culture than was wild-type virus but maintained similar in vitro replication kinetics compared to the wild-type virus. Analyses of enzyme activity of protease variants with one, three, and six changes indicated that these enzymes, compared to wild-type protease, retained 40, 47, and 61% activity, respectively. These results suggest that deficient protease enzymatic activity is sufficient for function, and the observed protease restoration might imply a selective advantage, at least in vitro, for increased protease activity.

During B cell differentiation rearrangement of immunoglobulin (Ig) genes is partially regulated by the Ig proteins. Rearrangement of heavy (H) chain genes is inhibited, whilst that of light (L) chain genes is induced by the membrane form of the mu H chain. In order to analyse additional structural requirements of mu induced L chain gene rearrangement we transfected wild‐type mu and mutant mu constructs lacking functional exons encoding the first or second constant domains into Abelson murine leukemia virus (AMuLV) transformed pre‐B cells. All mu chains are expressed on the surface of the pre‐B cell and all associate with omega and iota, two proteins forming a surrogate light chain, necessary for mu membrane expression. Nevertheless, only wild‐type mu and not the mutant mu proteins promote L gene rearrangement. A heterodimer of proteins with Mr of 33 kd and 36 kd was found associated with wild‐type but not with the mutant mu proteins. Continuous presence of mu is required for L chain gene recombination since loss of mu stopped and readdition of mu started L gene rearrangement. We propose that the protein complex composed of mu and the 33 kd/36 kd protein heterodimer is responsible for the activation of the L chain gene locus and its rearrangement.

Over the last two decades, the focus of public sector budgeting and management in most OECD Member countries has changed from inputs towards outputs. While important elements of an input-based management approach remain, many managers are now more often judged by how their programmes perform rather than by how well they adhere to administrative controls and procedures, or how successful they are in obtaining resources for their programme. The jury is still out as to the details of actual gains and losses connected to this change, but generally it is the view of central budgeting and management institutions that this change in focus has enhanced the quality of management and increased programme effectiveness and efficiency.

In vivo tests were performed to assess the influence of the protease inhibitor TL-3 on feline immunodeficiency virus (FIV)-induced central nervous system (CNS) deficits. Twenty cats were divided into four groups of five animals each. Group 1 received no treatment, group 2 received TL-3 only, group 3 received FIV strain PPR (FIV-PPR) only, and group 4 received FIV-PPR and TL-3. Animals were monitored for immunological and virological status, along with measurements of brain stem auditory evoked potential (BAEP) changes. Groups 1 and 2 remained FIV negative, and groups 3 and 4 became virus positive and seroconverted by 3 to 5 weeks postinoculation. No adverse effects were noted with TL-3 only. The average peak viral load for the virus-only group 3 animals was 1.32 ؋ 10 6 RNA copies/ml, compared to 6.9 ؋ 10 4 copies/ml for TL-3-treated group 4 cats. Group 3 (virus-only) cats exhibited marked progressive delays in BAEPs starting at 2 weeks post virus exposure, which is typical of infection with FIV-PPR. In contrast, TL-3-treated cats of group 4 exhibited BAEPs similar to those of control and drug-only cats. At 97 days postinfection, treatments were switched; i.e., group 4 animals were taken off TL-3 and group 3 animals were treated with TL-3. BAEPs in group 3 animals returned to control levels, while BAEPs in group 4 animals remained at control levels. After 70 days on TL-3, group 3 was removed from the drug treatment regimen. Delays in BAEPs immediately increased to levels observed prior to TL-3 treatment. The findings show that early TL-3 treatment can effectively eliminate FIV-induced changes in the CNS. Furthermore, TL-3 can counteract FIV effects on the CNS of infected cats, although continued treatment is required to maintain unimpaired CNS function.

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