Gene Therapy Approaches in HIV Treatment

Abstract

The search for a cure for human immunodeficiency virus (HIV) infection has been a persistent challenge in global health. While antiretroviral therapy (ART) has significantly improved the prognosis for individuals living with HIV, the need for lifelong treatment and the presence of viral reservoirs and drug resistance necessitate innovative approaches. Gene therapy has emerged as a promising avenue in HIV treatment, utilizing genetic modification to address the complexities of the virus. This chapter provides a comprehensive overview of gene therapy approaches in HIV treatment. It explores the fundamental principles and techniques of gene therapy and highlights the specific challenges posed by HIV. Various gene therapy strategies, including gene editing technologies and gene transfer methods, are discussed in detail, along with their potential advantages and limitations. Safety, efficacy, and ethical considerations in gene therapy for HIV are also examined. The chapter concludes with a glimpse into the future of gene therapy in HIV treatment, emphasizing the importance of interdisciplinary collaboration and continued research. This chapter aims to inspire further exploration and harnessing of gene therapy’s transformative potential in the quest for an HIV cure.

1. Introduction

Products for cell and gene therapy have been created and studied as possible therapies or cures for the HIV illness during the course of more than 20 years of study [1]. Here, we review recent developments and show how cell and gene therapies may be able to provide the coveted treatment.

HIV cell and gene therapy dates at least as far back as 1994, when a retroviral vector to rewire T cells such that they would express an MHC-unrestricted recognition protein [2]. The modified cells were designed to recognize and eliminate cells with infection that expressed cell surface envelope glycoprotein. The recognition molecule was a shortened variant of the CD4 glycoprotein receptor for (human immunodeficiency virus) HIV. This was an early version of what is now known as MHC-unrestricted and CAR-mediated recognition of cellular antigens. In the years that followed, T cells were modified to recognize infected cells via a variety of receptors, to fend against HIV attachment, and to prevent viral reproduction. Circulating lymphocytes or hematopoietic stem cell precursor cells (HSCPC) have undergone genetic changes, and cells were infused during clinical trials to see whether they might prevent the comeback of plasma viremia after treatment discontinuation [3]. Stable suppression of HIV in the absence of antiretroviral medication treatment has not been accomplished, with the exception of cells altered ex vivo to disrupt the CCR5 gene and infused into a trial participant heterozygous for the CCR5delta32 loss of function allele [4, 5, 6].

We provide this important evaluation of the most recent advances in gene and cell therapy for HIV to explain why so many approaches have failed to achieve the aim and if novel therapies have better chances. Studies on bulk CD4 T cell genetic manipulation, mostly employing CRISPR/Cas9 editing tools, and recent advancements in CAR methods, which are addressed elsewhere in this book, were purposefully left out [7, 8, 9].

Traditionally, there are two categories of gene therapy: those in which the effector molecule is a nucleic acid and those in which it is a protein. Based on how genetic treatment works, there is a second categorization. Thus, there are immunomodulatory proteins, suicide genes, ribozymes, decoy RNAs, DNA and RNA-based antisense compounds, and transdominant negative proteins.

1.1 Nucleic acid-based antivirals

1.1.1 Antisense

A definition of intracellular immunization as being more similar to traditional medications does not suit DNA oligonucleotides well. However, the idea of a particular treatment binding to a viral nucleic acid becomes highly alluring when you consider that a nucleotide sequence needs to be 17 bases to be unique within the human genome. Conventional DNA is fragile and challenging to work with. As a result, DNA oligonucleotides are often chemically altered bases with nuclease-resistant connections like phosphoroamidate or phosphorothioate. Tissue and cell penetration seems to be these compounds’ main concern. An oligonucleotide’s concentration is likely to decrease at least 10-fold from the extracellular to the intracellular compartment, and it loses even more concentration from the cytoplasm to the nucleus, where it has the greatest potential to have a therapeutic effect. Levin and Stein talk about these issues. Commercial businesses are still conducting clinical studies using GEM®91, a 25 nucleotide phosphorothioate oligodeoxynucleotide targeted at the gag start codon [10].

1.1.2 RNA based antivirals

1.1.2.1 Antisense RNA

This complementary RNA binds by Watson-Crick bands to the target RNA, generating a double-stranded structure that will be broken down by cellular enzymes. Naturally, areas of the HIV genome known to have significant cis-acting (non-coding) activities are the focus of antisense RNA strategies [11, 12]. As a result, popular targets include the TAR region/polyadenylation signal and the packaging signal. It has also been tried to use RNA directed against the coding sequences of several structural proteins and essential viral proteins including Tat and Rev. as depicted in Figure 1 [13].

Figure 1.

Antisense and ribozymes.

Inhibiting HIV replication utilizing a range of delivery methods, such as microinjection or cotransfection of the antiviral with a DNA encoding the viral genes, has been shown in the majority of these investigations. Resistance to an HIV challenge has also been tested using cells that persistently produce antiviral antisense. The findings show some inconsistencies. For instance, targeting the RNA sequence responsive to Tat (TAR) and inhibiting the Tat initiation codon are thought to have a comparable impact [14]. This is not the case, which stresses how difficult it is to forecast how these molecules will interact with biological systems and how some of these agents’ outcomes are not always reproducible.

1.1.2.2 Ribozyme antivirals

As with antisense, ribozymes bind to their target RNA by sequence complementarity, but they also include a unique sequence that functions like a typical enzyme and precisely cleaves the target RNA, making it inactive as depicted in Figure 1. These have mostly been reported to have comparable reported effectiveness and have been targeted against similar sections of the genome to those of antisense as well as the Rev. responsive element (RRE) [15]. As a catalytic agent, ribozymes are expected to have a stronger impact at lower concentrations since they may recycle and cleave subsequent target RNAs. This has not always been the case, and it is well known that ribozyme activity validated in vitro does not always correspond to effective function in cells. This is because some of the effect observed may be caused by an antisense effect of the complementary regions of the target and effector RNAs. The significance of the effector RNA’s co-localization with its target RNA inside the cell does seem to have been verified as a principle. This has been accomplished by comparing the effects of targeted and non-targeted ribozymes and demonstrating a substantial difference between them.

A Phase I clinical study is being conducted on a hairpin ribozyme that targets the U5 region of the long terminal repeat and has been examined in vitro and in a transgenic mouse model [16]. Additionally, some early findings indicate that an anti-Tat ribozyme-containing vector can increase the patient cells’ ability to survive an HIV challenge.

1.1.2.3 Decoys

A crucial functional portion of the native viral RNA may adopt a structure similar to an RNA that can be expressed in a cell as a decoy (see Figure 2). The viral or cellular protein that is expected to interact with the viral RNA but is sequestered away by high levels of decoy expression, inhibiting proper viral processing. The TAR and the RRE have been apparent targets as could be predicted, and this method has shown some promising in vitro findings. Also investigated were decoys with the exact same structure as the packing signal (Ψ). Inhibiting viral replication is not consistently shown to be beneficial across all trials, however [17].

Figure 2.

Decoy strategy.

1.1.3 Protein based therapies

1.1.3.1 Transdominant proteins

A transdominant protein is a comparable but altered variant of the wild type protein that disrupts a viral process. Examples of this include structural proteins that help assemble multimeric complexes yet hinder the binding of additional subunits by their inclusion (see Figure 3). Alternately, a protein with a binding and an activation domain in its natural form may have the latter altered such that it will still bind but prevents the target from binding the original protein, preventing the necessary process from occurring [18]. Transdominant inhibition is the term used to describe situations where a small number of units may counteract the effects of many wild type molecules. The Rev. M10 dominant mutant, which has been found to suppress laboratory and clinical viral isolates, is the one that has been examined the most in relation to HIV [19]. Since the M10 mutation affects Rev’s nuclear export signal, it is likely interfering with its capacity to transport RNA out of the nucleus. Phase II clinical trials for Rev. M10 have begun, and preliminary findings from experiments reveal that cells expressing Rev. M10 outlive those expressing an inactive M10 version in vivo. A very little improvement has been made in the cellular half-life, which has been increased to a maximum of 15 days. In a similar vein, Sam, a mutant variant of Rev’s cellular homolog, has been altered to join Rev. in an inactive complex. The possibility of interfering with vital physiological processes is one risk associated with the mutation of cellular proteins.

Figure 3.

Dominant negative inhibition.

1.1.3.2 Transcellular antibodies

When attaching to their molecular targets, antibodies are very selective, and the production of a shortened version of the antibody—which will stay within the cell—has been utilized to target viral proteins and stop viral export. Working with antibodies against the viral envelope and reverse transcriptase enzyme, an anti-Tat antibody has been investigated. Similarly, a possible strategy utilizing this mechanism is to downregulate cell surface receptors like CXCR4 to obstruct viral entrance [20]. Again, however, suppressing the expression of a receptor that is vital for cell survival or performs important signaling activities might be dangerous.

1.1.3.3 Death genes

Incorporating a promoter that will be activated by the viral transactivator Tat (also known as the viral LTR) and drive a gene, such as a toxin or the thymidine kinase gene, which is fatal to cells in the presence of the medication ganciclovir, is an appealing alternative [21]. Although in principle this makes sense, the viral long terminal repeat has a very low level of specificity and is susceptible to activation by a variety of different viral and cellular transactivators. This will probably result in the somewhat non-specific killing of antiviral-expressing cells up until fine specificity of expression is attained.

1.1.3.4 Interferons

Natural antiviral chemicals called interferons are created in response to viral infection and other stimuli. The prospect of inhibiting viral replication by integrating the interferon gene under the control of the HIV-1 promoter or by utilizing the same promoter to drive interferon triggered antiviral enzymes like PKR has been investigated in a number of research [22]. Continuous low dosage interferon expression has also been studied and is thought to have a role in the broad and potent inhibition of viral replication. It seemed to have no negative effects on the transplanted human immune system cells in a mouse model [23].

2. Gene editing tools for HIV treatment

2.1 Introduction to gene editing technologies

Researchers now have the capacity to quickly and affordably incorporate sequence-specific alterations into the genomes of a variety of cell types and species because to the development of highly adaptable genome-editing methods. Transcription activator-like effector nucleases (TALENs), zinc-finger nucleases (ZFNs), clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), and homing endonucleases or meganucleases round out the core technologies that are currently most frequently used to facilitate genome editing (Figure 4) [24, 25].

Figure 4.

Genome-editing technologies.

2.2 CRISPR-Cas9 and its applications in targeting the viral genome

CRISPR stands for clustered regularly interspaced short palindromic repeats, which were discovered to be separated by spacers—non-repeating DNA sequences—in Escherichia coli. The memory of the plasmid and phage genomes is provided by these spacers, known as CRISPR arrays, which were subsequently identified as acquired copies of previously encountered foreign DNA. The bacteria create RNA segments from the CRISPR arrays to target the pathogen specifically and launch an adaptive immune response when they come into contact with the foreign genetic material once again. Well-conserved CRISPR-associated (Cas) genes around CRISPR arrays have been classified into families and subtypes based on the closeness of their encoded proteins’ sequences. There are six different CRISPR/Cas system varieties, which have been split into two groups: in class two systems (types II, V, and VI), interference is carried out by a single effector protein as opposed to class 1 systems (types I, III, and IV), which use multi-Cas protein complexes [26, 27].

The Streptococcus pyogenes (Sp) Type II CRISPR/Cas9 system is the one that has been investigated and utilized the most. The CRISPR/Cas9 system’s overall biogenesis and operation are shown in Figure 5. The unique protospacer sequences found in the CRISPR array, which have similarity to foreign DNA, are translated to create lengthy precursor CRISPR RNA (pre-crRNA). The interference apparatus is subsequently directed by the pre-crRNA to cleave complementary sequences or protospacers, thus eradicating the foreign DNA. In order to bind crRNA in a sequence complementary way and draw in the RNAse III and CRISPR-associated nine (Cas9) enzymes, an invariant trans-activating CRISPR RNA (tracrRNA) is needed [28]. TracrRNA, RNAse III, and Cas9 combine to create a complex with every distinct crRNA. This system’s protospacer adjacent motifs (PAMs), which are situated just where the crRNA would bind, are essential and help to make CRISPR targeting specific. Invading foreign DNA is removed by genome editing processes involving non-homologous end joining (NHEJ) or homology-directed repair (HDR), which are stimulated by the helicase and nuclease activity of Cas protein motifs that are guided by crRNA [29].

Figure 5.

Outline of guiding RNA biosynthesis and CRISPR-Cas9 genome targeting. The essential elements of Streptococcus pyogenes site for CRISPR-Cas.

The Cas9 effector endonuclease has been repurposed by scientists as a pharmaceutical tool for accurate gene editing to remove or integrate specific genes in the human genome. The tracrRNA:crRNA complex has been amalgamated into a single guide RNA (sgRNA) to direct CRISPR-Cas9 toward the intended genomic targets [30]. The successful utilization of this system and its gene editing capabilities in eukaryotic cells has led to its widespread adoption in various research domains. CRISPR/Cas9 is now a commonly employed technique.

3. In vivo gene therapy strategies

Using in vivo gene transfer techniques, the gene therapy vector is either administered directly to the target organ or is delivered via the vascular system to the organ’s feeding channels. Compared to ex vivo methods, in vivo gene transfer offers the benefit of avoiding the time-consuming (and expensive) procedure of extracting cells from the patient, genetically altering the cells in vitro, and then returning the transformed cells to the patient. The induction of immunity by the gene transfer vector, delivery of the gene therapy vector to the targeted cells/organs, effective binding of the vector to the cell, translocation of the genetic material to the nucleus, and toxicity and immunity induced by virus expression are obstacles that need to be overcome for in vivo gene transfer strategies as depicted in Figure 6 [31].

Figure 6.

In vivo gene therapy.

3.1 Delivery methods for in vivo gene therapy

Different techniques are used by gene delivery systems to enable the absorption of the gene that has been chosen to target the cell. A thorough knowledge of the interaction process between the target cell and the delivery system is necessary for the effective design of a gene delivery system. The key to creating a more efficient gene delivery system is comprehending intercellular flow and targeting mechanisms. Cell targeting is the process of delivering a therapeutic substance to a particular cell organelle or compartment. In endocytosis gene therapy, especially in cellular absorption of non-viral gene delivery methods, it is the most often employed technique. Viral gene delivery systems are made up of viruses that have undergone engineering to become replication-deficient. These viruses are able to carry the genes to the cells for expression. For the delivery of viral genes, lentiviruses, retroviruses, and adenoviruses are used. The continual expression and expression of therapeutic genes are benefits of viral systems. The utilization of these systems is however constrained by certain drawbacks, including the creation of viruses, immunogenicity, toxicity, and lack of optimization in large-scale manufacturing [32, 33, 34].

As an alternative to systems based on viruses, non-viral gene delivery methods were created. These systems’ ability to develop transfection is one of their key benefits. Physical and chemical delivery methods for non-viral genes are separated into these two groups. The most popular physical techniques include microinjection, electroporation, gene guns, ultrasound-mediated techniques, and hydrodynamic systems. Physical techniques entail applying physical pressure to make the cell membrane more permeable so that the gene may enter the cell. Physical approaches’ main benefits are that they are dependable and simple to utilize. They can also injure tissue in particular situations, which is a drawback.

For gene transport into the cell, chemical approaches employ carriers made from synthetic or natural chemicals, such as synthetic and natural polymers, liposomes, dendrimers, synthetic proteins, and cationic lipids. The fact that these systems are non-immunogenic and often have minimal toxicity is one of their main benefits [35].

The difference between in vivo and ex vivo gene therapy as given in Table 1.

In vivo gene therapy	Ex vivo gene therapy
Another type of gene therapy is in vivo gene therapy, which is done directly when the defective cells are yet in the body.	Ex vivo gene therapy is a type of gene therapy in which gene modification is done outside the patient’s body.
It is less invasive	It is more invasive
Technically simple	Technically more complex
Vectors introduced directly in body	No vectors introduced directly in body
In this method safety check is not possible	In this method safety check is possible
Decreased control over target cells	Close control possible

Table 1.

Difference between in vivo and ex vivo gene therapy.

3.2 Viral vectors and their role in delivering therapeutic genes

According to whether their genomes integrate into the host cellular chromatin (oncoretroviruses and Lentivirus) or remain in the cell nucleus mostly as extra chromosomal episomes (Adeno-Associated Virus, Adenovirus, and herpes viruses), the five main classes of viral vectors may be divided into two categories. The effectiveness of transgenic expression, simplicity of manufacture, safety, toxicity, and stability all factor into the selection of viral vectors for clinical usage.

Additionally, RNA and DNA viruses with either single-stranded (ss) or double-stranded (ds) genomes serve as examples of the various vector types. Eight Infectious agents are categorized into risk groups for laboratory research (Risk Groups 1–4) in the World Health Organization (WHO) Laboratory Biosafety Manual and the National Institutes of Health (NIH) Recombinant DNA Guidelines. The risk group provides information on the biosafety degree of containment required to reduce risk while handling certain infectious pathogens.

3.2.1 Adenovirus vector

Adenoviruses are a group of non-enveloped DNA viruses with double-stranded genomes that range in size from 34 to 43 kb. These viruses use alternative splicing to encode genes in both sense and antisense directions. The AV genome has eight transcription units and two ITRs on either side of it. The first viral sections to be transcriptionally transcribed are known as the early regions (E1A, E1B, E2, E3, and E4), which also include the proteins that activate transcription of additional viral regions and modify the cellular environment to enhance viral production [36]. From an alternatively spliced transcript, the late sections (L1-L5) are translated. After infection, the AV genome persists in an additional chromosomal form. Humans have 51 different serotypes of AV; 45–80% of the population harbors neutralizing antibodies against Ad5, the most prevalent, due to natural infections, which typically date back to infancy [37]. They are capable of high titer production and high infection multiplicity gene delivery. These characteristics have made them one of the viral vectors most often utilized in in vivo research and clinical trials for gene therapy. Adenoviral vectors can, however, cause a large amount of inflammation, which severely restricts their practical application. Additionally, because adenoviral vectors cannot integrate into the host’s genome, the transgene’s expression is episomal and hence transitory. Due to this drawback, adenoviral vectors are more frequently utilized to create short-term gene expression than they are for illnesses that call for continuous gene expression. Adenoviral vectors, for instance, are used in cancer research to transmit a suicide gene that kills tumor cells [38].

3.2.2 Retrovirus vector

Retroviruses have a diploid ssRNA genome, an enveloped RNA structure, and at least 4 genes: gag, pro, pol, and env. The major structural polyprotein, which is encoded by the gag gene, is required for the formation of immature and non-infectious viral-like particles [39]. The viral protease, which is encoded by the pro gene, aids in the development of viral particles. Reverse transcriptase, RNase H, and integrase are made by the pol gene, whereas the env gene makes the viral surface glycoproteins and transmembrane proteins that facilitate binding to cellular receptors and membrane fusion. The capacity of RV and retroviral vectors to incorporate into host DNA is a common characteristic. In addition, complex RV like HIV-1 encode auxiliary proteins that improve replication and contagiousness. Reversible transcription of viral RNA results in integration of the transcript into a provirus. The host cell’s enzymes are extremely successfully used by the RV for both long-term production of viral proteins and replication. Like the majority of viruses, the RV requires a receptor to enter the host cell. Many oncogenic RVs are replication-defective variants that include oncogene sequence in place of a portion of their normal viral gene complement. Malignant illness and a number of other pathogenic states are also brought on by replication-competent retroviruses in a wide range of animals. The acquired immunodeficiency syndrome (AIDS) is caused by the retrovirus’s HIV-1 and HIV-2 [40].

Retroviruses display a number of properties/characteristics that influences their potential asvectors in gene therapy protocols. These may be summarized as follows:

• The biochemistry and molecular biology of retroviruses as a whole have been extensively investigated.

• The majority of retroviruses can only incorporate their proviral DNA into cells that are actively reproducing.

• The efficacy of gene transfer to the most vulnerable cell types is extremely high, frequently close to 100%.

• It is possible for integrated DNA to experience persistent, somewhat high-level expression.

• The chromosomes of the host are randomly incorporated with proviral DNA.

• Retroviruses are promiscuous in that they infect a wide range of cell types that are dividing.

• If the original recipient cell splits, full copies of the proviral DNA are passed on to daughter cells.

• It is possible to create reliable, high-level titer stocks of replication-incompetent retroviral particles.

• Retroviral vectors have previously been the subject of several animal species’ safety investigations.

The use of retroviruses as gene therapy vectors is nonetheless restricted by several of the other traits described. Their capacity to infect only dividing cells obviously limits their usage in the majority of cases.

Another drawback is that they are not selective about the kinds of proliferating cells that they infect. The entrance of each particular retrovirus is contingent upon the presence of an adequate viral receptor on the surface of a target cell, and they will not infect all types of proliferating cells. It is still challenging to forecast the full spectrum of cell types that any retrovirus is likely to infect during a gene therapy regimen since the identities of the majority of retroviral receptors are yet unknown. Physiological issues might arise if the foreign gene is integrated and expressed in cells other than the target cells as depicted in Figure 7.

Figure 7.

Ex vivo gene therapy.

In the context of gene therapy, clinical applications for monogenic disorders, cancer, and infectious illnesses, retroviral vectors have been widely utilized to transport therapeutic genes, ensuring a stable and effective expression of the transgene in patients [41].

3.3 Modification of hematopoietic stem cells for enhanced antiviral properties

The treatment of an increasing variety of human illnesses with hematopoietic stem cell gene therapy (HSC GT) is proving to be an effective and adaptable method. After receiving a conditioning therapy that encourages their engraftment in the bone marrow, hematopoietic stem/progenitor cells (HSPC) are removed from the body, genetically modified ex vivo, and then reinjected back into the same person. The engrafted HSPC guarantee a consistent flow of genetically modified offspring, maybe throughout the recipient’s whole life.

Then, mature cells from many lineages may treat diseases including cancer, infections, genetic immune weaknesses, and problems with blood and storage.

Treatment of numerous hematologic illnesses has shown effective when hematopoietic stem cells (HSCs) are genetically modified using lentiviral or anti-retroviral vectors (LVs). The degree of alteration of real repopulating HSCs continues to be a key determinant of therapy success. Gene delivery has been demonstrated to be improved by transduction-enhancing methods such as HSC-enhancing cytokine culture, high multiplicity of infection (MOI), repeated LV injection, alternative LV envelope pseudotyping, or the inclusion of transduction-enhancing small molecules [42].

Hematopoietic stem and progenitor cells (HSPCs) are resistant to infection by a variety of viruses and intracellular bacteria in addition to LV transduction. The significance of constitutive interferon-stimulated gene expression in pluripotent and multipotent cell types has recently come to light. The interferon-induced transmembrane (IFITM) family of proteins in particular, which are interferon-regulated innate effectors, offer an inherent defense against pathogens that depend on cellular endosomes for entrance and transport [43].

The IFITM proteins were initially discovered to be antiviral effectors against the vesicular stomatitis virus (VSV). They have the ability to limit the transduction of VSV-G protein pseudotyped (LV) LV and to control cellular growth, adhesion, and development. We recently shown that the mammalian target of rapamycin (mTOR) inhibitor rapamycin pharmacologically overcomes the IFITM limitation, which restricts the effectiveness of gene delivery using VSV-G pseudotyped LVs in HPSCs. Rapamycin, a substance that suppresses the immune system and has a variety of undesirable consequences, can cause cell growth to be delayed. Although they can have unfavorable cytotoxic effects, staurosporine and the IFITM3-modulating cyclosporines also exhibit LV transduction enhancer activity. The various restriction factors from HIV-1 trafficking that the VSV-G pseudotyped LVs experience as a result of their different subcellular trafficking approach might impact integration and change delay [44].

3.4 Genetic engineering of T cells for improved immune response

The gene transfer could be used to improve the effectiveness of T lymphocytes was apparent from the beginning of clinical studies in the field. T cells were the very first targets for genetic modification in human gene transfer experiments. An advantage of T cell-based immunotherapy compared to conventional chemotherapy, small molecules, and monoclonal antibodies is endurance because of continual generation of antigen-specific effector and memory T cells. In the presence of chronic infections or cancer, this hallmark allows both responses to pathogens and hiking for recurrence and minimal residual disease. However, persistence of genetically modified lymphocytes has been variable and often suboptimal in clinical trials. This variability may be a result of differences in the composition of infused cells, with some studies infusing a mixture of CD4+ and CD8+ cells, and other pure populations of CD8+ cytotoxic cells [45]. In addition, T cells may differ in their expansion potential, homing, and persistence, based on their differentiation status. When T lymphocytes encounter antigen, they undergo a developmental program from naïve (TNA), to central memory (TCM) and effector memory (TEM) cells. Gene-modified lymphocytes currently infused to patients are usually generated starting from unselected circulating T cells and will thus contain an unpredictable mixture of cellular subsets. Investigators are now trying to identify the optimal T cell target for gene transfer [46].

4. Safety and ethical considerations

The following elements should be considered in order to ensure the security of gene therapy for HIV: international cooperation between researchers from the public and private sectors, as well as participation from communities affected by the virus, social value, scientific validity, fair participant and study site selection, a favorable and acceptable risk-benefit balance, independent scientific and ethical review, informed and voluntary consent, and respect for enrolled patients. Participants should receive appropriate medical care and compensation if they suffer unpleasant study-related occurrences.

Genome editing technologies are regarded as the most challenging yet effective tools for gene therapy procedures [47]. Zinc finger nucleases (ZFN), transcription activator-like effector nucleases (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) are the most widely used methods for editing the genome. The biggest moral problem with gene therapy is called “off-target mutation,” which can lead to insertional mutagenesis and gene mutation. Because genome editing is a new and unpredictable technique and because the mechanisms regulating gene regulation and embryonic development are still poorly understood, bioethicists and scientists fear that the effects of germline therapy could be fatal [48]. Despite having demonstrated its value in therapeutic somatic applications, CRISPR/Cas has not yet advanced to the point where it may be utilized to alter the human genome for clinical reproductive purposes. As a result, the apparent long-term effects cannot be ignored. Genome editing on human embryos carries a very high risk of causing pathological diseases and disabilities, which may have long-term consequences for both the patient and their offspring. Off-target cleavage activity in DNA sequences has been demonstrated to occasionally occur in the past, despite stringent constraints on Cas9 targeting specificity [49].

Since the first gene therapy death in a clinical trial was announced in September 1999, the informed decision to participate in a clinical study has become more and more contentious. It is encouraged that patients in gene therapy clinical trials receive in-depth information about the potential dangers and benefits of the therapy in order to provide them the knowledge to make an informed decision about whether or not to participate without being forced [50]. The National Human Genome Research Institute (NHGRI) highlighted the requirement and significance of informed permission in CRISPR somatic genome editing after interviewing individuals with sickle cell disease for a study [51]. Though gene therapies may one day treat a wide range of terminal illnesses, the perceived benefits of the technology should not overshadow the difficulties patients may face in comprehending long-term hazards. While somatic gene therapy complies with the requirement for informed consent, the regulation of germline embryo editing raises more difficult issues, such as whether or not a future generation’s consent is required and, if so, who should provide that consent given that embryos are unable to give their consent for germline intervention [51]. Regarding the extent of parental authority over the embryo, there is ethical discussion about whether parents will be the only autonomous entity to make decisions for their unborn children or if this will be seen as displacing the interests of future generations who are unable to consent at the time of the decision [52].

5. Conclusions

Gene therapy approaches in HIV treatment hold immense promise in addressing the challenges associated with the management and potential cure of human immunodeficiency virus (HIV) infection. This chapter has provided a comprehensive overview of the principles, techniques, and potential applications of gene therapy in the context of HIV.

The exploration of various gene therapy strategies, including gene editing technologies such as CRISPR/Cas9 and gene transfer methods utilizing viral and non-viral vectors, has shed light on the potential advantages and limitations of each approach. These advancements have opened up new avenues for targeted intervention, modification of viral reservoirs, and enhancement of the immune response against HIV.

Critical considerations surrounding the safety, efficacy, and ethical implications of gene therapy have been addressed. It is crucial to conduct rigorous preclinical and clinical evaluations to ensure the safety of these approaches and to monitor long-term effects. Additionally, ethical discussions must accompany the development and implementation of gene therapies to ensure responsible and equitable use.

Looking ahead, the future of gene therapy in HIV treatment holds significant potential. Continued interdisciplinary collaboration between researchers, clinicians, and policymakers is essential to advance the field and translate scientific discoveries into practical applications. Ongoing research, clinical trials, and technological advancements will further refine gene therapy approaches and increase their efficacy and accessibility. While challenges remain, including the need for efficient delivery systems, cost-effectiveness, and scalability, the progress made in gene therapy for HIV treatment offers hope for a potential cure. By harnessing the transformative power of gene therapy and building upon the knowledge gained, researchers and practitioners can strive toward improved outcomes for individuals living with HIV.

Acknowledgments

The authors would like to express their sincere gratitude to the Management of RSM’s N. N. Sattha College of Pharmacy, Ahmednagar, for providing the necessary resources and support for the completion of this work. We would also like to acknowledge the valuable contributions of our colleagues who provided insightful discussions and suggestions throughout the research process.

Conflict of interest

The authors declare no conflict of interest.