Lentiviral transduction of human T-lymphocytes with a RANTES intrakine inhibits human immunodeficiency virus type 1 infection

Increased Efficiency for Biallelic Mutations of the CCR5 Gene by CRISPR-Cas9 Using Multiple Guide RNAs As a Novel Therapeutic Option for Human Immunodeficiency Virus

CCR5 is a coreceptor of human immunodeficiency virus type 1 (HIV-1). Transplantation of hematopoietic stem cells homozygous for a 32-bp deletion in CCR5 resulted in a loss of detectable HIV-1 in two patients, suggesting that genetic strategies to knockout CCR5 expression would be a promising gene therapy approach for HIV-1-infected patients. In this study, we targeted CCR5 by CRISPR-Cas9 with a single-guide (sgRNA) and observed 35% indel frequency. When we expressed hCas9 and two gRNAs, the Surveyor assay showed that Cas9-mediated cleavage was increased by 10% with two sgRNAs. Genotype analysis on individual clones showed 11 of 13 carried biallelic mutations, where 4 clones had frameshift (FS) mutations. Taken together, these results indicate that the efficiency of biallelic FS mutations and the knockout of the CCR5 necessary to prevent viral replication were significantly increased with two sgRNAs. These studies demonstrate the knockout of CCR5 and the potential for translational development.

Lentiviral delivery of combinatorial CAR/CRISPRi circuit into human primary T cells is enhanced by TBK1/IKKɛ complex inhibitor BX795

Background

Adoptive transfer of engineered immune cells is a promising strategy for cancer treatment. However, low transduction efficiency particularly when large payload lentiviral vectors are used on primary T cells is a limitation for the development of cell therapy platforms that include multiple constructs bearing long DNA sequences. RB-340-1 is a new CAR T cell that combines two strategies in one product through a CRISPR interference (CRISPRi) circuit. Because multiple regulatory components are included in the circuit, RB-340-1 production needs delivery of two lentiviral vectors into human primary T cells, both containing long DNA sequences. To improve lentiviral transduction efficiency, we looked for inhibitors of receptors involved in antiviral response. BX795 is a pharmacological inhibitor of the TBK1/IKKɛ complex, which has been reported to augment lentiviral transduction of human NK cells and some cell lines, but it has not been tested with human primary T cells. The purpose of this study was to test if BX795 treatment promotes large payload RB-340-1 lentiviral transduction of human primary T cells.

Methods

To make the detection of gene delivery more convenient, we constructed another set of RB-340-1 constructs containing fluorescent labels named RB-340-1F. We incorporated BX795 treatment into the human primary T cell transduction procedure that was optimized for RB-340-1F. We tested BX795 with T cells collected from multiple donors, and detected the effect of BX795 on T cell transduction, phenotype, cell growth and cell function.

Results

We found that BX795 promotes RB-340-1F lentiviral transduction of human primary T cells, without dramatic change in cell growth and T cell functions. Meanwhile, BX795 treatment increased CD8+ T cell ratios in transduced T cells.

Conclusions

These results indicate that BX795 treatment is effective, and might be a safe approach to promote RB-340-1F lentiviral transduction of human primary T cells. This approach might also be helpful for other T cell therapy products that need delivery of complicated platform via large payload lentiviral vectors.

Genetic Strategies for HIV Treatment and Prevention

Conventional HIV gene therapy approaches are based on engineering HIV target cells that are non-permissive to viral replication. However, expansion of gene-modified HIV target cells has been limited in patients. Alternative genetic strategies focus on generating gene-modified producer cells that secrete antiviral proteins (AVPs). The secreted AVPs interfere with HIV entry, and, therefore, they extend the protection against infection to unmodified HIV target cells. Since any cell type can potentially secrete AVPs, hematopoietic and non-hematopoietic cell lineages can function as producer cells. Secretion of AVPs from non-hematopoietic cells opens the possibility of using a genetic approach for HIV prevention. Another strategy aims at modifying cytotoxic T cells to selectively target and eliminate infected cells. This review provides an overview of the different genetic approaches for HIV treatment and prevention.

HIV Entry and Its Inhibition by Bifunctional Antiviral Proteins

HIV entry is a highly specific and time-sensitive process that can be divided into receptor binding, coreceptor binding, and membrane fusion. Bifunctional antiviral proteins (bAVPs) exploit the multi-step nature of the HIV entry process by binding to two different extracellular targets. They are generated by expressing a fusion protein containing two entry inhibitors with a flexible linker. The resulting fusion proteins exhibit exceptional neutralization potency and broad cross-clade inhibition. In this review, we summarize the HIV entry process and provide an overview of the design, antiviral potency, and methods of delivery of bAVPs. Additionally, we discuss the advantages and limitations of bAVPs for HIV prevention and treatment.

Huwe1 is a novel mediator of protection of neural progenitor L2.3 cells against oxygen‑glucose deprivation injury

Hypoxic‑ischemic encephalopathy is one of the most notable causes of brain injury in newborns. Cerebral ischemia and reperfusion lead to neuronal damage and neurological disability. In vitro and in vivo analyses have indicated that E3 ubiquitin protein ligase (Huwe1) is important for the process of neurogenesis during brain development; however, the exact biological function and the underlying mechanism of Huwe1 remain controversial. In the present study, neural progenitor cells, L2.3, of which we previously generated from rat E14.5 cortex, were used to investigate the role of Huwe1 and its effects on the downstream N‑Myc‑Delta‑like 3‑Notch1 signaling pathway during oxygen‑glucose deprivation (OGD). To evaluate the role of Huwe1 in L2.3 cells, transduction, cell viability, lactate dehydrogenase, 5‑bromo‑2'deoxyurine incorporation, western blotting and immunocytochemical assays were performed. The results of the present study indicated that Huwe1 rescued L2.3 cells from OGD‑induced insults by inhibiting proliferation and inducing neuronal differentiation. In addition, Huwe1 was suggested to mediate the survival of L2.3 cells by inhibiting the activation of the N‑Myc‑Notch1 signaling pathway. Of note, the effects of Huwe1 on Notch1 signaling were completely abolished by knockdown of N‑Myc, indicating that Huwe1 may require N‑Myc to suppress the activation of the Notch1 signaling in L2.3 cells. The determination of the neuroprotective function of the Huwe1‑N‑Myc‑Notch1 axis may provide insight into novel potential therapeutic targets for the treatment of ischemic stroke.

CCR5 Revisited: How Mechanisms of HIV Entry Govern AIDS Pathogenesis

The chemokine receptor CCR5 has been the focus of intensive studies since its role as a coreceptor for HIV entry was discovered in 1996. These studies lead to the development of small molecular drugs targeting CCR5, with maraviroc becoming in 2007 the first clinically approved chemokine receptor inhibitor. More recently, the apparent HIV cure in a patient transplanted with hematopoietic stem cells devoid of functional CCR5 rekindled the interest for inactivating CCR5 through gene therapy and pharmacological approaches. Fundamental research on CCR5 has also been boosted by key advances in the field of G-protein coupled receptor research, with the realization that CCR5 adopts a variety of conformations, and that only a subset of these conformations may be targeted by chemokine ligands. In addition, recent genetic and pathogenesis studies have emphasized the central role of CCR5 expression levels in determining the risk of HIV and SIV acquisition and disease progression. In this article, we propose to review the key properties of CCR5 that account for its central role in HIV pathogenesis, with a focus on mechanisms that regulate CCR5 expression, conformation, and interaction with HIV envelope glycoproteins.

Genetic Modulation Therapy Through Stem Cell Transplantation for Human Immunodeficiency Virus 1 Infection

Highly active anti-retroviral treatment has changed the dimensions of the outcomes for patients suffering from human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). However, HIV infection is still an ailment which is spreading throughout the world extensively. Given the confinements of the present restorative methodologies and the non-availability of any strategic vaccination against HIV, there is a squeezing need to build a therapeutic treatment.

Viral tropism for HIV includes CD4+ cells, macrophages, and microglial cells, and it is through binding with co-receptors C-C chemokine receptor type 5 (CCR5) and C-X-C chemokine receptor type 4 (CXCR4). While these cell types are present in all individuals, there are rare cases that stayed uninfected even after getting exposed to an overwhelming load of HIV. Research revealed a homozygous 32-base pair deletion (Δ32/Δ32) in CCR5. After careful consideration, a hypothesis was proposed a few years back that a cure for HIV disease is possible, through hematopoietic stem cells transplantation from a donor homozygous for the CCR5-Δ32 deletion.

Hematopoietic stem cell (HSC) based quality treatment may serve as a promising tool as these perpetual, self-renewing progenitor cells could be modified to oppose HIV infection. If done properly, the changed HSCs would offer the permanent creation of genetically modified cells that are resistant to HIV infection and/or have improved hostility to viral action which will eventually clear the contaminated cells.

The purpose of this review is to concentrate on two facets of HSC genetic treatment for potentially life-threatening HIV infection: building HIV-resistant cells and designing cells that can target HIV disease. These two strategic approaches can be the frontline of a quality treatment plan against HIV infection and, as an individual treatment or a combination thereof, has been proposed to possibly destroy HIV altogether.

Epigenetic Regulation of Antibody Responses by the Histone H2A Deubiquitinase MYSM1

B cell-mediated antibody response plays critical roles in protective immunity, as well as in the pathogenesis of allergic and autoimmune diseases. Epigenetic histone and DNA modifications regulate gene transcription and immunity; however, so far, little is known about the role of epigenetic regulation in antibody responses. In this study, we found that mice deficient in the histone H2A deubiquitinase MYSM1, despite their severe defect in B cell development, exhibit an enhanced antibody response against both T cell-dependent and independent antigens. We revealed that MYSM1 intrinsically represses plasma cell differentiation and antibody production. Mechanistic studies demonstrated that MYSM1 is a transcriptional activator of Pax5, the repressors of plasma cell differentiation, by facilitating key transcriptional factor recruitment and coordinating histone modifications at the Pax5 loci. Hence, this study uncovers a critical role for MYSM1 in epigenetically repressing plasma cell differentiation and antibody production, in addition to its opposing, active role in B cell development. Importantly, this study further provides a new target and strategy to modulate antibody production and responses with profound therapeutic implications.

CCR5 Targeted Cell Therapy for HIV and Prevention of Viral Escape

Allogeneic transplantation with CCR5-delta 32 (CCR5-d32) homozygous stem cells in an HIV infected individual in 2008, led to a sustained virus control and probably eradication of HIV. Since then there has been a high degree of interest to translate this approach to a wider population. There are two cellular ways to do this. The first one is to use a CCR5 negative cell source e.g., hematopoietic stem cells (HSC) to copy the initial finding. However, a recent case of a second allogeneic transplantation with CCR5-d32 homozygous stem cells suffered from viral escape of CXCR4 quasi-species. The second way is to knock down CCR5 expression by gene therapy. Currently, there are five promising techniques, three of which are presently being tested clinically. These techniques include zinc finger nucleases (ZFN), clustered regularly interspaced palindromic repeats/CRISPR-associated protein 9 nuclease (CRISPR/Cas9), transcription activator-like effectors nuclease (TALEN), short hairpin RNA (shRNA), and a ribozyme. While there are multiple gene therapy strategies being tested, in this review we reflect on our current knowledge of inhibition of CCR5 specifically and whether this approach allows for consequent viral escape.

Bone Marrow Gene Therapy for HIV/AIDS

Bone marrow gene therapy remains an attractive option for treating chronic immunological diseases, including acquired immunodeficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV). This technology combines the differentiation and expansion capacity of hematopoietic stem cells (HSCs) with long-term expression of therapeutic transgenes using integrating vectors. In this review we summarize the potential of bone marrow gene therapy for the treatment of HIV/AIDS. A broad range of antiviral strategies are discussed, with a particular focus on RNA-based therapies. The idea is to develop a durable gene therapy that lasts the life span of the infected individual, thus contrasting with daily drug regimens to suppress the virus. Different approaches have been proposed to target either the virus or cellular genes encoding co-factors that support virus replication. Some of these therapies have been tested in clinical trials, providing proof of principle that gene therapy is a safe option for treating HIV/AIDS. In this review several topics are discussed, ranging from the selection of the antiviral molecule and the viral target to the optimal vector system for gene delivery and the setup of appropriate preclinical test systems. The molecular mechanisms used to formulate a cure for HIV infection are described, including the latest antiviral strategies and their therapeutic applications. Finally, a potent combination of anti-HIV genes based on our own research program is described.

Cell-based gene therapy against HIV

The ability to integrate inside the host genome lays a strong foundation for HIV to play hide and seek with the host's immune surveillance mechanisms. Present anti-viral therapies, although successful in suppressing the virus to a certain level, fail to wipe it out completely. However, recent approaches in modifying stem cells and enabling them to give rise to potent/resistant T-cells against HIV holds immense hope for eradication of the virus from the host. In this review, we will briefly discuss previous landmark studies on engineering stem cells or T-cells that have been explored for therapeutic efficacy against HIV. We will also analyze potential benefits and pitfalls of some studies done recently and will share our opinion on emerging trends.

Phenotypic Knockout of CXCR4 Expression by a Novel Intrakine Mutant hSDF-1α/54/KDEL Inhibits Breast Cancer Metastasis

Many malignant tumors express high levels of the chemokine receptor CXCR4, and the interaction between CXCR4 and its ligand, SDF-1, promotes migration, invasion, and metastasis of breast cancer cells. Therefore, blocking the interaction between CXCR4 and SDF-1 could alter the tumor's metastatic phenotype and control the development and progression of cancers. We used a cellular phenotypic knockout strategy and developed a novel recombinant gene, AdSDF-1α/54/KDEL, which contains an adenovirus vector, a mutant form of SDF-1 that lacks a C-terminal α-helix, and a KDEL tetrapeptide sequence that promotes retention at the endoplasmic reticulum (ER). We hypothesized that SDF-1α/54/KDEL could efficiently block metastasis of breast cancer cells with less inflammatory side effects than SDF-1α/KDEL. Using the MCF-7 cell line, which expresses a stable, high level of CXCR4, we found that SDF-1α/54/KDEL efficiently becomes localized at the ER of tumor cells, where it specifically binds to newly synthesized CXCR4 and prevents it from reaching the cell surface. Chemotaxis and invasion assays revealed that the cells treated with SDF-1α/54/KDEL failed to migrate toward SDF-1. We also found that SDF-1α/54/KDEL impaired lung metastasis of metastatic breast cancer by decreasing CXCR4 on the cell surface. The novel recombinant gene, SDF-1α/54/KDEL, played an instrumental role in blocking SDF-1/CXCR4-mediated cell migration, and we found that this gene-based strategy for targeting the SDF-1/CXCR4 axis offers a very effective alternative method for preventing metastasis of breast cancer and other cancers expressing high levels of CXCR4.

Engineering T Cells to Functionally Cure HIV-1 Infection

Despite the ability of antiretroviral therapy to minimize human immunodeficiency virus type 1 (HIV-1) replication and increase the duration and quality of patients' lives, the health consequences and financial burden associated with the lifelong treatment regimen render a permanent cure highly attractive. Although T cells play an important role in controlling virus replication, they are themselves targets of HIV-mediated destruction. Direct genetic manipulation of T cells for adoptive cellular therapies could facilitate a functional cure by generating HIV-1-resistant cells, redirecting HIV-1-specific immune responses, or a combination of the two strategies. In contrast to a vaccine approach, which relies on the production and priming of HIV-1-specific lymphocytes within a patient's own body, adoptive T-cell therapy provides an opportunity to customize the therapeutic T cells prior to administration. However, at present, it is unclear how to best engineer T cells so that sustained control over HIV-1 replication can be achieved in the absence of antiretrovirals. This review focuses on T-cell gene-engineering and gene-editing strategies that have been performed in efforts to inhibit HIV-1 replication and highlights the requirements for a successful gene therapy-mediated functional cure.

Potential mechanisms for cell-based gene therapy to treat HIV/AIDS

INTRODUCTION

An estimated 35 million people are infected with HIV worldwide. Anti-retroviral therapy (ART) has reduced the morbidity and mortality of HIV-infected patients but efficacy requires strict adherence and the treatment is not curative. Most importantly, the emergence of drug-resistant virus strains and drug toxicity can restrict the long-term therapeutic efficacy in some patients. Therefore, novel treatment strategies that permanently control or eliminate the virus and restore the damaged immune system are required. Gene therapy against HIV infection has been the topic of intense investigations for the last two decades because it can theoretically provide such a durable anti-HIV control.

AREAS COVERED

In this review we discuss two major gene therapy strategies to combat HIV. One approach aims to kill HIV-infected cells and the other is based on the protection of cells from HIV infection. We discuss the underlying molecular mechanisms for candidate approaches to permanently block HIV infection, including the latest strategies and future therapeutic applications.

EXPERT OPINION

Hematopoietic stem cell-based gene therapy for HIV/AIDS may eventually become an alternative for standard ART and should ideally provide a functional cure in which the virus is durably controlled without medication. Recent results from preclinical research and early-stage clinical trials support the feasibility and safety of this novel strategy.

Enhanced antitumor immunity is elicited by adenovirus-mediated gene transfer of CCL21 and IL-15 in murine colon carcinomas

The chemokine CCL21 is a potent chemoattractant for T cells and dendritic cells. IL-15 elicits powerful antitumor immune responses through the stimulation of natural killer cells. We constructed a CCL21/IL-15-expressing adenovirus (Ad-CCL21-IL-15) and evaluated its antitumor effects in vitro and in vivo. We found that the intratumoral injection of Ad-CCL21-IL-15 into murine colon carcinomas significantly inhibited tumor growth. Splenocytes from mice treated with Ad-CCL21-IL-15 developed tumor-specific cytotoxic T cells and were protected from subsequent challenges with tumor cells. This study indicates that providing cancer therapy by combining CCL21 and IL-15 can induce antitumor immune responses and is an effective strategy for cancer immunotherapy.

Stem-cell-based gene therapy for HIV infection

Despite the enormous success of combined anti-retroviral therapy, HIV infection is still a lifelong disease and continues to spread rapidly worldwide. There is a pressing need to develop a treatment that will cure HIV infection. Recent progress in stem cell manipulation and advancements in humanized mouse models have allowed rapid developments of gene therapy for HIV treatment. In this review, we will discuss two aspects of HIV gene therapy using human hematopoietic stem cells. The first is to generate immune systems resistant to HIV infection while the second strategy involves enhancing anti-HIV immunity to eliminate HIV infected cells.

Novel cell and gene therapies for HIV

Highly active antiretroviral therapy dramatically improves survival in HIV-infected patients. However, persistence of HIV in reservoirs has necessitated lifelong treatment that can be complicated by cumulative toxicities, incomplete immune restoration, and the emergence of drug-resistant escape mutants. Cell and gene therapies offer the promise of preventing progressive HIV infection by interfering with HIV replication in the absence of chronic antiviral therapy. Individuals homozygous for a deletion in the CCR5 gene (CCR5Δ32) are largely resistant to infection from R5-topic HIV-1 strains, which are most commonly transmitted. A recent report that an HIV-infected patient with relapsed acute myelogenous leukemia was effectively cured from HIV infection after transplantation of hematopoietic stem/progenitor cells (HSC) from a CCR5Δ32 homozygous donor has generated renewed interest in developing treatment strategies that target viral reservoirs and generate HIV resistance in a patient's own cells. Although the development of cell-based and gene transfer therapies has been slow, progress in a number of areas is evident. Advances in the fields of gene-targeting strategies, T-cell-based approaches, and HSCs have been encouraging, and a series of ongoing and planned trials to establish proof of concept for strategies that could lead to successful cell and gene therapies for HIV are under way. The eventual goal of these studies is to eliminate latent viral reservoirs and the need for lifelong antiretroviral therapy.

Specific transgene expression in HIV-infected cells using protease-cleavable transcription regulator

Gene therapy is a promising strategy for the treatment of HIV infection, but cell specificity remains an issue. Recently we have developed a new concept for a drug or gene delivery system responding to cellular signals (D-RECS) to achieve cell-specific transgene expression using a non-viral polymer-based vehicle. According to this concept, intracellular signaling enzymes, which are activated specifically in target cells, are used to trigger transgene expression. We previously applied this concept to HIV-1 protease and showed that the recombinant protease could act as a suitable signal. Here we further developed this system to achieve highly specific transgene expression in HIV-infected cells. We prepared a polymeric gene regulator grafted with a cationic peptide containing the HIV-Tat peptide via a specific substrate for HIV-1 protease. The regulator formed a stable polyplex with the transgene, suppressing its transcription. HIV-1 protease cleaved the peptide and released the transgene, which was consequently expressed specifically in activated HIV-infected cells, but remained unreleased and inactive in uninfected cells. The validity of this approach was further confirmed by applying it to the CVB1 2A protease of coxsackievirus (Picornaviridae family). This strategy should be widely applicable for specific expression of a variety of therapeutic genes in virus-infected cells.

Sustained Analgesic Peptide Secretion and Cell Labeling Using a Novel Genetic Modification

Cell-based therapy for neuropathic pain could provide analgesics to local pain modulatory regions in a sustained, renewable fashion. In order to provide enhanced analgesic efficacy, transplantable cells may be engineered to produce complementary or increased levels of analgesic peptides. In addition, genetic labeling of modified cells is desirable for identification and tracking, but it should be retained intracellularly as desired analgesic peptides are secreted. Usually constructs encode proteins destined for either extra- or intracellular compartments, as these pathways do not cross. However, interactions between intracellular destinations provide a window of opportunity to overcome this limitation. In this report, we have explored this approach using a potential supplementary analgesic peptide, [Ser1]-histogranin (SHG), the stable synthetic derivative of a naturally occurring peptide with N-methyl D-aspartate (NMDA) antagonistic properties. A synthetic SHG gene was combined with (i) nerve growth factor-β (NGF-β) amino-terminal signal peptide to enable secretion, and (ii) a fluorescent cellular label (mRFP) with intervening cathepsin L cleavage site, and subcloned into a lentiviral vector. In addition, an endoplasmic retention signal, KDEL, was added to enable retrieval of mRFP. Using immunocytochemistry and confocal microscopic profile analysis, cells transduced by such lentiviruses were shown to synthesize a single SHG-mRFP polypeptide that was processed, targeted to expected subcellular destinations in several cell types. Dot blot and Western analysis revealed stable transduction and long-term secretion of SHG from PC12 cells in vitro. Transplantation of such cells provided modest analgesia in a rodent pain model consistent with low levels of SHG peptide in the cerebrospinal fluid (CSF). These results suggest that it is possible to deliver proteins with different final destinations from a single construct, such as pharmacologically active peptide for secretion and intracellular label for identifying transplantable cells.

Genetic therapies against HIV

Highly active antiretroviral therapy prolongs the life of HIV-infected individuals, but it requires lifelong treatment and results in cumulative toxicities and viral-escape mutants. Gene therapy offers the promise of preventing progressive HIV infection by sustained interference with viral replication in the absence of chronic chemotherapy. Gene-targeting strategies are being developed with RNA-based agents, such as ribozymes, antisense, RNA aptamers and small interfering RNA, and protein-based agents, such as the mutant HIV Rev protein M10, fusion inhibitors and zinc-finger nucleases. Recent advances in T-cell-based strategies include gene-modified HIV-resistant T cells, lentiviral gene delivery, CD8(+) T cells, T bodies and engineered T-cell receptors. HIV-resistant hematopoietic stem cells have the potential to protect all cell types susceptible to HIV infection. The emergence of viral resistance can be addressed by therapies that use combinations of genetic agents and that inhibit both viral and host targets. Many of these strategies are being tested in ongoing and planned clinical trials.

Silencing of HIV-1 gene expression by two types of siRNA expression systems

The RNA interference (RNAi) phenomenon is a recently discovered process in which the introduction of a double-stranded RNA (dsRNA) into cells causes the specific degradation of mRNA containing the same sequence. We designed mammalian expression vectors that direct the synthesis of small interfering RNA (siRNA)-like transcripts and examined them for their siRNA-mediated gene interference targeting the env gene (NL4-3:7490-7508, E7490). We constructed siRNA expression vectors for two different strands (sense and antisense; tandem promoter) and for siRNA expressed from the short hairpin RNA (shRNA). The inhibition efficacy on HIV-1 replication differed between these two vectors. Notably, the shRNA vector pU6-env-shRNA inhibited p24 production more effectively than the tandem promoter expression vector pU6-env-siRNA. Furthermore, we examined the ability of lentiviral vectors expressing shRNA to suppress HIV-1 expression in HIV-1-infected SupT1 cells. The env-shRNA (E 7490) almost completely suppressed HIV-1 expression in infected cells for up to 15 days.

Can gene delivery close the door to HIV-1 entry after escape?

BACKGROUND

Research efforts to prevent viral entry by developing small molecule inhibitors against HIV-1 chemokine coreceptors have yielded promising clinical results. However, resistance to some chemokine receptor inhibitors has been recently documented, and therefore, alternative methods of HIV-1 coreceptor disruption are needed.

CONCLUSION

We will describe current HIV-1 vector-delivered genetic disruption mechanisms that target HIV-1 chemokine coreceptors, such as RNA interference, ribozymes, zinc fingers, intrakines, and intrabodies, and frame the use of these gene delivery chemokine receptor disruption mechanisms in the context of current small molecule blocker/antagonists of CCR5 and CXCR4. In addition, we will discuss the importance of evaluating HIV-1 vector-delivered viral entry prevention mechanisms in the rhesus macaque SIV non-human primate model in regard to pathogenesis and therapeutic efficacy.

Current status of gene therapy strategies to treat HIV/AIDS

Progress in developing effective gene transfer approaches to treat HIV-1 infection has been steady. Many different transgenes have been reported to inhibit HIV-1 in vitro. However, effective translation of such results to clinical practice, or even to animal models of AIDS, has been challenging. Among the reasons for this failure are uncertainty as to the most effective cell population(s) to target, the diffuseness of these target cells in the body, and ineffective or insufficiently durable gene delivery. Better understanding of the HIV-1 replicative cycle, host factors involved in HIV-1 infection, vector biology and application, transgene technology, animal models, and clinical study design have all contributed vastly to planning current and future strategies for application of gene therapeutic approaches to the treatment of AIDS. This review focuses on the newest developments in these areas and provides a strong basis for renewed optimism that gene therapy will have an important role to play in treating people infected with HIV-1.

Antitumor immune response by CX3CL1 fractalkine gene transfer depends on both NK and T?cells

The CX3C chemokine fractalkine (CX3CL1) exists as both a membrane-bound form promoting firm cell-cell adhesion and a soluble form chemoattracting leukocytes expressing its receptor CX3CR1. When adenoviral vector expressing mouse fractalkine (AdFKN) was transduced to the tumor cells, fractalkine was expressed as both membrane-bound form on the tumor cells and soluble form in the supernatant in vitro. Intratumoral injection of AdFKN (1 x 10(9)PFU/tumor) into C26 and B16F10 tumors resulted in marked reduction of tumor growth compared to control (C26: 86.5%, p<0.001; B16F10: 85.5%, p<0.001). Histological examination of tumor tissues revealed abundant infiltration of NK cells, dendritic cells, and CD8(+) T lymphocytes 3 and/or 6 days after treatment with AdFKN. Splenocytes from mice treated by AdFKN developed tumor-specific cytotoxic T cells, and thereby protected from rechallenging with parental tumor cells. Antitumor effects by AdFKN were completely abrogated in both NK cell-depleted mice and CD8(-/-) mice, and partially blocked in CD4(-/-) mice. These data indicated that fractalkine mediates antitumor effects by both NK cell-dependent and T cell-dependent mechanisms. This study suggests that fractalkine can be a suitable candidate for immunogene therapy of cancer because fractalkine induces both innate and adaptive immunity.

CXCR4 knockdown by small interfering RNA abrogates breast tumor growth in vivo

Breast cancer cells express the chemokine receptor CXCR4 and frequently metastasize to organs with an abundant source of the CXCR4 ligand, stromal cell-derived factor 1 (SDF-1). The chemokine receptor CXCR4 plays an active role in the metastasis of breast cancer. Here, we show that a small interfering RNA (siRNA) against CXCR4 effectively downregulates CXCR4 expression in human MDA-MB-231 breast cancer cells, leading to significant decrease in breast cancer cell invasion and adhesion. It was further found that tumor cells lacking CXCR4 expression proliferated at a much slower rate than control cells in vitro. Surprisingly, tumor cells lacking CXCR4 expression failed to grow in SCID mice in repeated experiments, providing the first direct evidence for an essential role of CXCR4 in breast cancer growth in vivo. This finding suggests an expanded role for the CXCR4 molecule in tumor cell growth in vivo, in addition to its role in breast cancer metastasis. This study implies the CXCR4 molecule as a potential target to control breast tumor growth as well as metastasis.

Gene transfer into human T lymphocytes and natural killer cells by Ad5/F35 chimeric adenoviral vectors

OBJECTIVE

Genetic modification of effector lymphocytes, such as T cells and natural killer (NK) cells, is essential for many approaches to gene-based immunotherapy of cancer. However, transduction of lymphocytes has proven difficult by currently available gene transfer methods. Previous studies have shown that chimeric fiber-modified Ad5/F35 adenoviral vectors are able to efficiently transduce hematopoietic cells including immature progenitors. In this study, we examined the gene transfer into T lymphocytes and NK cells using Ad5/F35 compared with conventional Ad5 adenovectors.

METHODS

Primary T and NK cells were isolated from healthy donors' peripheral blood leukocytes by immunomagnetic selection. Cell lines and primary lymphocytes were transduced with replication-defective Ad5/F35 and Ad5, both containing a GFP reporter gene under the control of a CMV promoter. Transduction efficiencies were monitored by flow cytometry. The function of transduced lymphocytes was assessed by analysis of proliferative responses to mitogenic agents and in mixed leukocyte reactions.

RESULTS

Transgene expression was detected in up to 45% of primary CD3+ T lymphocytes and in up to 60% of primary NK cells using Ad5/F35. In contrast, conventional Ad5 transduced less than 8% and 5% of primary T cells and NK cells, respectively. Transduction efficiencies were similar in CD4+ and CD8+ T lymphocytes, and transgene expression could be detected for up to seven days. Activation of T cells significantly enhanced the efficiency of Ad5/F35-mediated gene transfer. Adenoviral transduction of lymphocytes did not result in any impairment of proliferative functions.

CONCLUSION

The results of this study demonstrate that both T lymphocytes and NK cells can be transduced by chimeric Ad5/F35 adenoviral vectors.

Genetic therapy for HIV/AIDS

Despite the tremendous success of highly active antiretroviral treatment (HAART) introduced nearly 8 years ago for the treatment of human immunodeficiency virus (HIV), innovative therapies, including gene transfer approaches, are still required for nearly half of the general patient population. A number of potential gene therapeutic targets for HIV have been identified and include both viral and cellular genes essential for viral replication. The diverse methods used to inhibit viral replication comprise RNA-based strategies such as ribozymes, RNA decoys, antisense messenger RNAs and small interfering RNA (siRNA) molecules. Other potential anti-HIV genes include dominant negative viral proteins, intracellular antibodies, intrakines and suicide genes, all of which have had a modicum of success in vitro. Cellular targets include CD4+ T cells, macrophages and their progenitors. The greatest gene transfer efficiency has been achieved using retroviral or, more recently, lentiviral vectors. A limited number of Phase I clinical trials suggest that the general method is safe. It is proposed that a national network for HIV gene therapy (similar to the AIDS Clinical Trial Groups) may be the best way to determine which approaches should proceed clinically.

Inhibiting HIV-1 infection in human T cells by lentiviral-mediated delivery of small interfering RNA against CCR5

Double-stranded RNAs approximately 21 nucleotides long [small interfering RNA (siRNA)] are recognized as powerful reagents to reduce the expression of specific genes. To use them as reagents to protect cells against viral infection, effective methods for introducing siRNAs into primary cells are required. Here, we describe success in constructing a lentivirus-based vector to introduce siRNAs against the HIV-1 coreceptor, CCR5, into human peripheral blood T lymphocytes. With high-titer vector stocks, >40% of the peripheral blood T lymphocytes could be transduced, and the expression of a potent CCR5-siRNA resulted in up to 10-fold inhibition of CCR5 expression on the cell surface over a period of 2 weeks in the absence of selection. In contrast, the expression of another major HIV-1 coreceptor, CXCR4, was not affected. Importantly, blocking CCR5 expression by siRNAs provided a substantial protection for the lymphocyte populations from CCR5-tropic HIV-1 virus infection, dropping infected cells by 3- to 7-fold; only a minimal effect on infection by a CXCR4-tropic virus was observed. Thus, our studies demonstrate the feasibility and potential of lentiviral vector-mediated delivery of siRNAs as a general means of intracellular immunization for the treatment of HIV-1 and other viral diseases.