Genetically modified hematopoietic stem cell transplantation for HIV-1-infected patients: can we achieve a cure?

Nanoparticle-based strategies to target HIV-infected cells

Antiretroviral drugs employed for the treatment of human immunodeficiency virus (HIV) infections have remained largely ineffective due to their poor bioavailability, numerous adverse effects, modest uptake in infected cells, undesirable drug-drug interactions, the necessity for long-term drug therapy, and lack of access to tissues and reservoirs. Nanotechnology-based interventions could serve to overcome several of these disadvantages and thereby improve the therapeutic efficacy of antiretrovirals while reducing the morbidity and mortality due to the disease. However, attempts to use nanocarriers for the delivery of anti-retroviral drugs have started gaining momentum only in the past decade. This review explores in-depth the various nanocarriers that have been employed for the treatment of HIV infections highlighting their merits and possible demerits.

CCR5: Established paradigms and new frontiers for a 'celebrity' chemokine receptor

Because of the level of attention it received due to its role as the principal HIV coreceptor, CCR5 has been described as a 'celebrity' chemokine receptor. Here we describe the development of CCR5 inhibitory strategies that have been developed for HIV therapy and which are now additionally being considered for use in HIV prevention and cure. The wealth of CCR5-related tools that have been developed during the intensive investigation of CCR5 as an HIV drug target can now be turned towards the study of CCR5 as a model chemokine receptor. We also summarize what is currently known about the cell biology and pharmacology of CCR5, providing an update on new areas of investigation that have emerged in recent research. Finally, we discuss the potential of CCR5 as a drug target for diseases other than HIV, discussing the evidence linking CCR5 and its natural chemokine ligands with inflammatory diseases, particularly neuroinflammation, and certain cancers. These pathologies may provide new uses for the strategies for CCR5 blockade originally developed to combat HIV/AIDS.

RNA Interference Therapies for an HIV-1 Functional Cure

HIV-1 drug therapies can prevent disease progression but cannot eliminate HIV-1 viruses from an infected individual. While there is hope that elimination of HIV-1 can be achieved, several approaches to reach a functional cure (control of HIV-1 replication in the absence of drug therapy) are also under investigation. One of these approaches is the transplant of HIV-1 resistant cells expressing anti-HIV-1 RNAs, proteins or peptides. Small RNAs that use RNA interference pathways to target HIV-1 replication have emerged as competitive candidates for cell transplant therapy and have been included in all gene combinations that have so far entered clinical trials. Here, we review RNA interference pathways in mammalian cells and the design of therapeutic small RNAs that use these pathways to target pathogenic RNA sequences. Studies that have been performed to identify anti-HIV-1 RNA interference therapeutics are also reviewed and perspectives on their use in combination gene therapy to functionally cure HIV-1 infection are provided.

On the way to find a cure: Purging latent HIV-1 reservoirs

Introduction of cART in 1996 has drastically increased the life expectancy of people living with HIV-1. However, this treatment has not allowed cure as cessation of cART is associated with a rapid viral rebound. The main barrier to the eradication of the virus is related to the persistence of latent HIV reservoirs. Evidence is now accumulating that purging the HIV-1 reservoir might lead to a cure or a remission. The most studied strategy is the so called "shock and kill" therapy. This strategy is based on reactivation of dormant viruses from the latently-infected reservoirs (the shock) followed by the eradication of the reservoirs (the kill). This review focuses mainly on the recent advances made in the "shock and kill" therapy. We believe that a cure or a remission will come from combinatorial approaches i.e. combination of drugs to reactivate the dormant virus from all the reservoirs including the one located in sanctuaries, and combination of strategies boosting the immune system. Alternative strategies based on cell and gene therapy or based in inducing deep latency, which are evoked in this review reinforce the idea that at least a remission is attainable.

Conditional Cytotoxic Anti-HIV Gene Therapy for Selectable Cell Modification

Gene therapy remains one of the potential strategies to achieve a cure for HIV infection. One of the major limitations of anti-HIV gene therapy concerns recovering an adequate number of modified cells to generate an HIV-proof immune system. Our study addresses this issue by developing a methodology that can mark conditional vector-transformed cells for selection and subsequently target HIV-infected cells for elimination by treatment with ganciclovir (GCV). We used the herpes simplex virus thymidine kinase (TK) mutant SR39, which is highly potent at killing cells at low GCV concentrations. This gene was cloned into a conditional HIV vector, pNL-GFPRRESA, which expresses the gene of interest as well as green fluorescent protein (GFP) in the presence of HIV Tat protein. We show here that TK-SR39 was more potent that wild-type TK (TK-WT) at eliminating infected cells at lower concentrations of GCV. As the vector expresses GFP in the presence of Tat, transient expression of Tat either by Tat RNA transfection or transduction by a nonintegrating lentiviral (NIL) vector marked the cells with GFP for selection. In cells selected by this strategy, TK-SR39 was more potent at limiting virus replication than TK-WT. Finally, in Jurkat cells modified and selected by this approach, infection with CXCR4-tropic Lai virus could be suppressed by treatment with GCV. GCV treatment limited the number of HIV-infected cells, virus production, as well as virus-induced cytopathic effects in this model. We provide proof of principle that TK-SR39 in a conditional HIV vector can provide a safe and effective anti-HIV strategy.

Towards a scalable HIV cure research agenda: the role of co-infections

The development of a cure is among the foremost contemporary priorities in the field of HIV research. The science that underpins a potential HIV cure should be generalisable to the many millions of persons globally who enter antiretroviral treatment programs with advanced immunosuppression and/or an opportunistic infection. We provide five key suggestions for incorporation into the HIV cure research agenda to maximise the generalisability and applicability of an HIV cure once developed.

Combinatorial hematopoietic stem cell transplantation and vaccination reduces viral pathogenesis following SHIV89.6P-challenge

Development of curative approaches for HIV-1 infected patients requires novel approaches aimed at eliminating viral reservoirs and replacing potential target cells with infection-resistant immune cell populations. We have previously shown that autologous transplantation of genetically modified hematopoietic stem cells (HSCs) with lentiviral vectors encoding the mC46-fusion inhibitor results in a significant reduction in viral pathogenesis following challenge with the highly pathogenic dual tropic, SHIV89.6P strain. In this study, we used a combinatorial approach in which following engraftment of genetically modified HSCs, pigtailed macaques were vaccinated with a previously developed vaccinia-based vaccine expressing SIV-Gag, Pol. Using this dual therapy approach, lower viremia was detected in both the acute and chronic phase of disease with levels reaching near the lower limits of detection. In comparison with macaques receiving HSCT only, the combination approach resulted in a further log decrease in plasma viremia. Similar to our previous studies, positive selection of all CD4(+) T-cell subsets was observed; however, higher gene-modified CD4(+) T-cell levels were observed during the chronic phase when vaccination was included suggesting that combining vaccination with HSCT may lower the necessary threshold for achieving viremic control.

Lentivirus-mediated Gene Transfer in Hematopoietic Stem Cells Is Impaired in SHIV-infected, ART-treated Nonhuman Primates

Recent studies have demonstrated that genetically modified hematopoietic stem cells (HSCs) can reduce HIV viremia. We have developed an HIV/AIDS-patient model in Simian/human immunodeficiency virus (SHIV)-infected pigtailed macaques that are stably suppressed on antiretroviral therapy (ART: raltegravir, emtricitabine and tenofovir). Following SHIV infection and ART, animals undergo autologous HSC transplantation (HSCT) with lentivirally transduced cluster of differentiation (CD)34(+) cells expressing the mC46 anti-HIV fusion protein. We show that SHIV(+), ART-treated animals had very low gene marking levels after HSCT. Pretransduction CD34(+) cells contained detectable levels of all three ART drugs, likely contributing to the low gene transfer efficiency. Following HSCT recovery and the cessation of ART, plasma viremia rebounded, indicating that myeloablative total body irradiation cannot completely eliminate viral reservoirs after autologous HSCT. The kinetics of recovery following autologous HSCT in SHIV(+), ART-treated macaques paralleled those observed following transplantation of control animals. However, T-cell subset analyses demonstrated a high percentage of C-C chemokine receptor 5 (CCR5)-expressing CD4(+) T-cells after HSCT. These data suggest that an extended ART interruption time may be required for more efficient lentiviral transduction. To avoid complications associated with ART interruption in the context of high percentages of CD4(+)CCR5(+)T-cells after HSCT, the use of vector systems not impaired by the presence of residual ART may also be beneficial.

Autologous Hematopoietic Stem Cells transplantation and genetic modification of CCR5 m303/m303 mutant patient for HIV/AIDS

HIV and AIDS is one of the biggest challenges all over the world. There are an approximately 34 million people living with the virus, and a large number of them become infected each year. Although there are some antiviral drugs for HIV viral load reduction, they are not sufficient. There is no cure for AIDS. Nowadays natural resistance or immunity has absorbed attentions. Because in some HIV positive patients progression trend is slow or even they indicate resistance to AIDS. One of the most interesting approaches in this category is CCR5 gene. CCR5 is a main cc-chemokine co-receptor that facilitates HIV-1 entry to macrophage and CD4(+) T cells. To now, many polymorphisms have been known by CCR5 gene that produces a truncated protein with no function. So, HIV-1 could not entry to immune-cells and the body resistant to HIV/AIDS. Δ32/Δ32 and m303/m303 homozygotes are example of mutations that could create this resistance mechanism. There is a new treatment, such as Hematopoietic Stem Cell transplantation (HSCT) in Berlin and Boston patients for Δ32/Δ32 mutation. It could eliminate co-receptor antagonist and highly-active-anti retroviral therapy (HAART) drugs problems such as toxicity, low safety and side-effects. Now there, the aim of this hypothesis will be evaluation of a new mutation CCR5 m303/m303 as autologous HSCT. This novel hypothesis indicates that autologous HSCT for m303/m303 could be effective treatment for anyone HIV/AIDS affected patient worldwide.

Progress toward curing HIV infections with hematopoietic stem cell transplantation

Combination antiretroviral therapy can suppress human immunodeficiency virus (HIV) infection but cannot completely eradicate the virus. A major obstacle in the quest for a cure is the difficulty in targeting and measuring latently infected cells. To date, a single person seems to have been cured of HIV. Hematopoietic stem cell transplantation (HSCT) preceded this cancer patient's long-term sustained HIV remission, but researchers have been unable to replicate this cure, and the mechanisms that led to HIV remission remain to be established. In February 2014, the National Institute of Allergy and Infectious Diseases sponsored a workshop that provided a venue for in-depth discussion of whether HSCT could be exploited to cure HIV in cancer patients requiring such procedures. Participants also discussed how HSCT might be applied to a broader community of HIV-infected persons in whom the risks of HSCT currently outweigh the likelihood and benefits of HIV cure.

RNA-directed gene editing specifically eradicates latent and prevents new HIV-1 infection

AIDS remains incurable due to the permanent integration of HIV-1 into the host genome, imparting risk of viral reactivation even after antiretroviral therapy. New strategies are needed to ablate the viral genome from latently infected cells, because current methods are too inefficient and prone to adverse off-target effects. To eliminate the integrated HIV-1 genome, we used the Cas9/guide RNA (gRNA) system, in single and multiplex configurations. We identified highly specific targets within the HIV-1 LTR U3 region that were efficiently edited by Cas9/gRNA, inactivating viral gene expression and replication in latently infected microglial, promonocytic, and T cells. Cas9/gRNAs caused neither genotoxicity nor off-target editing to the host cells, and completely excised a 9,709-bp fragment of integrated proviral DNA that spanned from its 5' to 3' LTRs. Furthermore, the presence of multiplex gRNAs within Cas9-expressing cells prevented HIV-1 infection. Our results suggest that Cas9/gRNA can be engineered to provide a specific, efficacious prophylactic and therapeutic approach against AIDS.

Optimized lentiviral vectors for HIV gene therapy: multiplexed expression of small RNAs and inclusion of MGMT(P140K) drug resistance gene

Gene therapy with hematopoietic stem and progenitor cells is a promising approach to engineering immunity to human immunodeficiency virus (HIV) that may lead to a functional cure for acquired immunodeficiency syndrome (AIDS). In support of this approach, we created lentiviral vectors with an engineered polycistronic platform derived from the endogenous MCM7 gene to express a diverse set of small antiviral RNAs and a drug resistance MGMT(P140K) marker. Multiple strategies for simultaneous expression of up to five RNA transgenes were tested. The placement and orientation of each transgene and its promoter were important determinants for optimal gene expression. Antiviral RNA expression from the MCM7 platform with a U1 promoter was sufficient to provide protection from R5-tropic HIV in macrophages and resulted in reduced hematopoietic toxicity compared with constructs expressing RNA from independent RNA polymerase III promoters. The addition of an HIV entry inhibitor and nucleolar TAR RNA decoy did not enhance antiviral potency over constructs that targeted only viral RNA transcripts. We also demonstrated selective enrichment of gene-modified cells in vivo using a humanized mouse model. The use of these less toxic, potent anti-HIV vectors expressing a drug selection marker is likely to enhance the in vivo efficacy of our stem cell gene therapy approach in treating HIV/AIDS.

"Much ado to achieve nothing: prospects for curing HIV infection"

Currently there is significant scientific effort being directed at developing ways to create either a sterilizing cure, or functional cure for HIV infection. Multiple approaches are being evaluated under the broad headings of gene therapy, immune based interventions, and treatments which depend upon HIV reactivation from latency to cause the death of cells which harbor the virus. Molecular and Cellular Therapies (MCT) welcomes all manuscripts devoted to increasing our understanding of determinants of affecting a cure for HIV and mechanistic studies determine the cellular and viral interventions necessary for achieving HIV cure.

"Much ado to achieve nothing: prospects for curing HIV infection"

Currently there is significant scientific effort being directed at developing ways to create either a sterilizing cure, or functional cure for HIV infection. Multiple approaches are being evaluated under the broad headings of gene therapy, immune based interventions, and treatments which depend upon HIV reactivation from latency to cause the death of cells which harbor the virus. Molecular and Cellular Therapies (MCT) welcomes all manuscripts devoted to increasing our understanding of determinants of affecting a cure for HIV and mechanistic studies determine the cellular and viral interventions necessary for achieving HIV cure.