Immune responses to adenovirus and adeno-associated virus in humans

Development of an Enzyme-Linked Immunosorbent Spot Assay for the Assessment of Adeno-Associated Virus Peptides to Examine Immune Safety

Adeno-associated virus (AAV)-based gene therapies have shown promise as novel treatments for rare genetic disorders such as hemophilia A and spinal muscular atrophy. However, cellular immune responses mediated by cytotoxic (CD8+) and helper (CD4+) T cells may target vector-transduced cells as well as healthy immune cells, impacting safety and efficacy. In this study, we describe the optimization and reproducibility of interferon-γ (IFNγ)-based and interleukin-2 (IL-2)-based enzyme-linked immunosorbent spot (ELISpot) assays for measuring T cell responses against AAV peptide antigens. For method optimization, peripheral blood mononuclear cells (PBMCs) were isolated from healthy human donors and stimulated with commercially available major histocompatibility complex (MHC) class I or II-specific peptides as positive controls. Peptide pools were designed from published AAV8 and AAV9 capsid protein sequences and then used to assess the presence of AAV-specific T cell responses. Our results demonstrate a measurable increase in IFNγ and IL-2-producing cells after AAV peptide presentation. Furthermore, there was an observed difference in the magnitude and specificity of response to peptide pools based on AAV serotype and donor. Finally, using individual peptides, we identified a region of the AAV9 capsid protein that can elicit an immunogenic response. This work shows the applicability of ELISpot in assessing anti-AAV immune responses and provides insight into how novel recombinant AAV vectors could be designed to reduce immunogenic potential.

Stem cell therapeutics and gene therapy for neurologic disorders

Rapid advances in biological knowledge and technological innovation have greatly advanced the fields of stem cell and gene therapies to combat a broad spectrum of neurologic disorders. Researchers are currently exploring a variety of stem cell types (e.g., embryonic, progenitor, induced pluripotent) and various transplantation strategies, each with its own advantages and drawbacks. Similarly, various gene modification techniques (zinc finger, TALENs, CRISPR-Cas9) are employed with various delivery vectors to modify underlying genetic contributors to neurologic disorders. While these two individual fields continue to blaze new trails, it is the combination of these technologies which enables genetically engineered stem cells and vastly increases investigational and therapeutic opportunities. The capability to culture and expand stem cells outside the body, along with their potential to correct genetic abnormalities in patient-derived cells or enhance cells with extra gene products, unleashes the full biological potential for innovative, multifaceted approaches to treat complex neurological disorders. In this review, we provide an overview of stem cell and gene therapies in the context of neurologic disorders, highlighting recent advances and current shortcomings, and discuss prospects for future therapies in clinical settings.

Prevalence Study of Cellular Capsid-Specific Immune Responses to AAV2, 4, 5, 8, 9, and rh10 in Healthy Donors

Recombinant adeno-associated virus (rAAV) vectors appear, more than ever, to be efficient viral vectors for in vivo gene transfer as illustrated by the approvals of 7 drugs across Europe and the United States. Nevertheless, preexisting immunity to AAV capsid in humans remains one of the major limits for a successful clinical translation. Whereas a preexisting humoral response to AAV capsid is well documented, the prevalence of preexisting capsid-specific T cell responses still needs to be studied and characterized. In this study, we investigated the prevalence of AAV-specific circulating T cells toward AAV2, 4, 5, 8, 9, and rh10 in a large cohort of healthy donors using the standard IFNγ ELISpot assay. We observed the highest prevalence of preexisting cellular immunity to AAV9 serotype followed by AAV8, AAV4, AAV2, AAVrh10, and AAV5 independently of the donors' serological status. An in-depth analysis of T cell responses toward the 2 most prevalent serotypes 8 and 9 shows that IFNγ secretion is mainly mediated by CD8 T cells for both serotypes. A polyfunctional analysis reveals different cytokine profiles between AAV8 and AAV9. Surprisingly, no IL-2 secretion was mediated by anti-AAV9 immune cells suggesting that these cells may rather be exhausted or terminally differentiated than cytotoxic T cells. Altogether, these results suggest that preexisting immunity to AAV may vary depending on the serotype and support the necessity of using multiparametric monitoring methods to better characterize anticapsid cellular immunity and foresee its impact in rAAV-mediated clinical trials.

Preferential Expansion of HPV16 E1-Specific T Cells from Healthy Donors' PBMCs after Ex Vivo Immunization with an E1E2E6E7 Fusion Antigen

Persistent human papillomavirus (HPV) infection is responsible for practically all cervical and a high proportion of anogenital and oropharyngeal cancers. Therapeutic HPV vaccines in clinical development show great promise in improving outcomes for patients who mount an anti-HPV T-cell response; however, far from all patients elicit a sufficient immunological response. This demonstrates a translational gap between animal models and human patients. Here, we investigated the potential of a new assay consisting of co-culturing vaccine-transduced dendritic cells (DCs) with syngeneic, healthy, human peripheral blood mononuclear cells (PBMCs) to mimic a human in vivo immunization. This new promising human ex vivo PBMC assay was evaluated using an innovative therapeutic adenovirus (Adv)-based HPV vaccine encoding the E1, E2, E6, and E7 HPV16 genes. This new method allowed us to show that vaccine-transduced DCs yielded functional effector T cells and unveiled information on immunohierarchy, showing E1-specific T-cell immunodominance over time. We suggest that this assay can be a valuable translational tool to complement the known animal models, not only for HPV therapeutic vaccines, and supports the use of E1 as an immunotherapeutic target. Nevertheless, the findings reported here need to be validated in a larger number of donors and preferably in patient samples.

Pathogenicity and virulence of human adenovirus F41: Possible links to severe hepatitis in children

Over 100 human adenoviruses (HAdVs) have been isolated and allocated to seven species, A-G. Species F comprises two members-HAdV-F40 and HAdV-F41. As their primary site of infection is the gastrointestinal tract they have been termed, with species A, enteric adenoviruses. HAdV-F40 and HAdV-F41 are a common cause of gastroenteritis and diarrhoea in children. Partly because of difficulties in propagating the viruses in the laboratory, due to their restrictions on growth in many cell lines, our knowledge of the properties of individual viral proteins is limited. However, the structure of HAdV-F41 has recently been determined by cryo-electron microscopy. The overall structure is similar to those of HAdV-C5 and HAdV-D26 although with some differences. The sequence and arrangement of the hexon hypervariable region 1 (HVR1) and the arrangement of the C-terminal region of protein IX differ. Variations in the penton base and hexon HVR1 may play a role in facilitating infection of intestinal cells by HAdV-F41. A unique feature of HAdV-F40 and F41, among human adenoviruses, is the presence and expression of two fibre genes, giving long and short fibre proteins. This may also contribute to the tropism of these viruses. HAdV-F41 has been linked to a recent outbreak of severe acute hepatitis "of unknown origin" in young children. Further investigation has shown a very high prevalence of adeno-associated virus-2 in the liver and/or plasma of some cohorts of patients. These observations have proved controversial as HAdV-F41 had not been reported to infect the liver and AAV-2 has generally been considered harmless.

Pre-clinical delivery of gene therapy products to the cerebrospinal fluid: challenges and considerations for clinical translation

While the majority of gene therapy studies in neurological indications have focused on direct gene transfer to the central nervous system (CNS), there is growing interest in the delivery of therapeutics using the cerebrospinal fluid (CSF) as a conduit. Historically, direct CNS routes-of-administration (RoAs) have relied on tissue dynamics, displacement of interstitial fluid, and regional specificity to achieve focal delivery into regions of interest, such as the brain. While intraparenchymal delivery minimizes peripheral organ exposure, one perceived drawback is the relative invasiveness of this approach to drug delivery. In this mini review, we examine the CSF as an alternative RoA to target CNS tissue and discuss considerations associated with the safety of performing such procedures, biodistribution of therapeutics following single administration, and translation of findings given differences between small and large animals. These factors will help delineate key considerations for translating data obtained from animal studies into clinical settings that may be useful in the treatment of neurological conditions.

Target-seq: single workflow for detection of genome integration site, DNA translocation and off-target events

Designed donor DNA delivery through viral or nonviral systems to target loci in the host genome is a critical step for gene therapy. Adeno-associated virus and lentivirus are leading vehicles for in vivo and ex vivo delivery of therapeutic genes due to their high delivery and editing efficiency. Nonviral editing tools, such as CRISPR/Cas9, are getting more attention for gene modification. However, there are safety concerns; for example, tumorigenesis due to off-target effects and DNA rearrangement. Analysis tools to detect and characterize on-target and off-target genome modification post editing in the host genome are pivotal for evaluating the success and safety of gene therapy. We developed Target-seq combined with different analysis tools to detect the genome integration site, DNA translocation and off-target events.

Immunogenicity of Recombinant Adeno-Associated Virus (AAV) Vectors for Gene Transfer

Recombinant adeno-associated viruses (AAVs) have emerged as promising gene delivery vehicles resulting in three US Food and Drug Administration (FDA) and one European Medicines Agency (EMA)-approved AAV-based gene therapies. Despite being a leading platform for therapeutic gene transfer in several clinical trials, host immune responses against the AAV vector and transgene have hampered their widespread application. Multiple factors, including vector design, dose, and route of administration, contribute to the overall immunogenicity of AAVs. The immune responses against the AAV capsid and transgene involve an initial innate sensing. The innate immune response subsequently triggers an adaptive immune response to elicit a robust and specific response against the AAV vector. AAV gene therapy clinical trials and preclinical studies provide important information about the immune-mediated toxicities associated with AAV, yet studies suggest preclinical models fail to precisely predict the outcome of gene delivery in humans. This review discusses the contribution of the innate and adaptive immune response against AAVs, highlighting the challenges and potential strategies to mitigate these responses, thereby enhancing the therapeutic potential of AAV gene therapy.

An Endogenous Retrovirus Vaccine Encoding an Envelope with a Mutated Immunosuppressive Domain in Combination with Anti-PD1 Treatment Eradicates Established Tumours in Mice

Endogenous retroviruses (ERVs) account for 8% of our genome, and, although they are usually silent in healthy tissues, they become reactivated and expressed in pathological conditions such as cancer. Several studies support a functional role of ERVs in tumour development and progression, specifically through their envelope (Env) protein, which contains a region described as an immunosuppressive domain (ISD). We have previously shown that targeting of the murine ERV (MelARV) Env using virus-like vaccine (VLV) technology, consisting of an adenoviral vector encoding virus-like particles (VLPs), induces protection against small tumours in mice. Here, we investigate the potency and efficacy of a novel MelARV VLV with a mutated ISD (ISDmut) that can modify the properties of the adenoviral vaccine-encoded Env protein. We show that the modification of the vaccine's ISD significantly enhanced T-cell immunogenicity in both prime and prime-boost vaccination regimens. The modified VLV in combination with an α-PD1 checkpoint inhibitor (CPI) exhibited excellent curative efficacy against large established colorectal CT26 tumours in mice. Furthermore, only ISDmut-vaccinated mice that survived CT26 challenge were additionally protected against rechallenge with a triple-negative breast cancer cell line (4T1), showing that our modified VLV provides cross-protection against different tumour types expressing ERV-derived antigens. We envision that translating these findings and technology into human ERVs (HERVs) could provide new treatment opportunities for cancer patients with unmet medical needs.

Prevalence of Neutralizing Antibodies against Adeno-Associated Virus Serotypes 1, 2, and 9 in Non-Injected Latin American Patients with Heart Failure—ANVIAS Study

Neutralizing antibody (NAb) activity against the viral capsid of adeno-associated viral (AAV) vectors decreases transduction efficiency, thus limiting transgene expression. Several reports have mentioned a variation in NAb prevalence according to age, AAV serotype, and, most importantly, geographic location. There are currently no reports specifically describing the anti-AAV NAb prevalence in Latin America. Here, we describe the prevalence of NAb against different serotypes of AAV vectors (AAV1, AAV2, and AAV9) in Colombian patients with heart failure (HF) (referred to as cases) and healthy individuals (referred to as controls). The levels of NAb were evaluated in serum samples of 60 subjects from each group using an in vitro inhibitory assay. The neutralizing titer was reported as the first dilution inhibiting ≥50% of the transgene signal, and the samples with neutralizing titers at ≥1:50 dilution were considered positive. The prevalence of NAb in the case and control groups were similar (AAV2: 43% and 45%, respectively; AAV1 33.3% in each group; AAV9: 20% and 23.2%, respectively). The presence of NAb for two or more of the serotypes analyzed was observed in 25% of the studied samples, with the largest amount in the positive samples for AAV1 (55–75%) and AAV9 (93%), suggesting serial exposures, cross-reactivity, or coinfection. Moreover, patients in the HF group exhibited more common combined seropositivity for NAb against AAV1 d AAV9 than those in the control group (91.6% vs. 35.7%, respectively; p = 0.003). Finally, exposure to toxins was significantly associated with the presence of NAb in all regression models. These results constitute the first report of the prevalence of NAb against AAV in Latin America, being the first step to implementing therapeutic strategies based on AAV vectors in this population in our region.

Preclinical development of a vaccine-based immunotherapy regimen (VBIR) that induces potent and durable T cell responses to tumor-associated self-antigens

The development of therapeutic cancer vaccines remains an active area, although previous approaches have yielded disappointing results. We have built on lessons from previous cancer vaccine approaches and immune checkpoint inhibitor research to develop VBIR, a vaccine-based immunotherapy regimen. Assessment of various technologies led to selection of a heterologous vaccine using chimpanzee adenovirus (AdC68) for priming followed by boosts with electroporation of DNA plasmid to deliver T cell antigens to the immune system. We found that priming with AdC68 rapidly activates and expands antigen-specific T cells and does not encounter pre-existing immunity as occurs with the use of a human adenovirus vaccine. The AdC68 vector does, however, induce new anti-virus immune responses, limiting its use for boosting. To circumvent this, boosting with DNA encoding the same antigens can be done repetitively to augment and maintain vaccine responses. Using mouse and monkey models, we found that the activation of both CD4 and CD8 T cells was amplified by combination with anti-CTLA-4 and anti-PD-1 antibodies. These antibodies were administered subcutaneously to target their distribution to vaccination sites and to reduce systemic exposure which may improve their safety. VBIR can break tolerance and activate T cells recognizing tumor-associated self-antigens. This activation lasts more than a year after completing treatment in monkeys, and inhibits tumor growth to a greater degree than is observed using the individual components in mouse cancer models. These results have encouraged the testing of this combination regimen in cancer patients with the aim of increasing responses beyond current therapies.

Current strategies employed in the manipulation of gene expression for clinical purposes

Abnormal gene expression level or expression of genes containing deleterious mutations are two of the main determinants which lead to genetic disease. To obtain a therapeutic effect and thus to cure genetic diseases, it is crucial to regulate the host's gene expression and restore it to physiological conditions. With this purpose, several molecular tools have been developed and are currently tested in clinical trials. Genome editing nucleases are a class of molecular tools routinely used in laboratories to rewire host's gene expression. Genome editing nucleases include different categories of enzymes: meganucleses (MNs), zinc finger nucleases (ZFNs), clustered regularly interspaced short palindromic repeats (CRISPR)- CRISPR associated protein (Cas) and transcription activator-like effector nuclease (TALENs). Transposable elements are also a category of molecular tools which includes different members, for example Sleeping Beauty (SB), PiggyBac (PB), Tol2 and TcBuster. Transposons have been used for genetic studies and can serve as gene delivery tools. Molecular tools to rewire host's gene expression also include episomes, which are divided into different categories depending on their molecular structure. Finally, RNA interference is commonly used to regulate gene expression through the administration of small interfering RNA (siRNA), short hairpin RNA (shRNA) and bi-functional shRNA molecules. In this review, we will describe the different molecular tools that can be used to regulate gene expression and discuss their potential for clinical applications. These molecular tools are delivered into the host's cells in the form of DNA, RNA or protein using vectors that can be grouped into physical or biochemical categories. In this review we will also illustrate the different types of payloads that can be used, and we will discuss recent developments in viral and non-viral vector technology.

Routes of administration for adeno-associated viruses carrying gene therapies for brain diseases

Gene therapy is a powerful tool to treat various central nervous system (CNS) diseases ranging from monogenetic diseases to neurodegenerative disorders. Adeno-associated viruses (AAVs) have been widely used as the delivery vehicles for CNS gene therapies due to their safety, CNS tropism, and long-term therapeutic effect. However, several factors, including their ability to cross the blood-brain barrier, the efficiency of transduction, their immunotoxicity, loading capacity, the choice of serotype, and peripheral off-target effects should be carefully considered when designing an optimal AAV delivery strategy for a specific disease. In addition, distinct routes of administration may affect the efficiency and safety of AAV-delivered gene therapies. In this review, we summarize different administration routes of gene therapies delivered by AAVs to the brain in mice and rats. Updated knowledge regarding AAV-delivered gene therapies may facilitate the selection from various administration routes for specific disease models in future research.

Progress in Respiratory Gene Therapy

The prospect of gene therapy for inherited and acquired respiratory disease has energized the research community since the 1980s, with cystic fibrosis, as a monogenic disorder, driving early efforts to develop effective strategies. The fact that there are still no approved gene therapy products for the lung, despite many early phase clinical trials, illustrates the scale of the challenge: In the 1990s, first-generation non-viral and viral vector systems demonstrated proof-of-concept but low efficacy. Since then, there has been steady progress toward improved vectors with the capacity to overcome at least some of the formidable barriers presented by the lung. In addition, the inclusion of features such as codon optimization and promoters providing long-term expression have improved the expression characteristics of therapeutic transgenes. Early approaches were based on gene addition, where a new DNA copy of a gene is introduced to complement a genetic mutation: however, the advent of RNA-based products that can directly express a therapeutic protein or manipulate gene expression, together with the expanding range of tools for gene editing, has stimulated the development of alternative approaches. This review discusses the range of vector systems being evaluated for lung delivery; the variety of cargoes they deliver, including DNA, antisense oligonucleotides, messenger RNA (mRNA), small interfering RNA (siRNA), and peptide nucleic acids; and exemplifies progress in selected respiratory disease indications.

Prevalence of Anti-AAV9 Antibodies in Adult Patients with Spinal Muscular Atrophy

5q-associated spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder that leads to progressive muscle atrophy and weakness. The disease is caused by a homozygous deletion or mutation in the survival of motor neuron 1 gene (SMN1), resulting in insufficient levels of SMN protein. Onasemnogene abeparvovec-xioi (OA) is a non-replicating vector based on adeno-associated virus serotype 9 (AAV9) that contains the full-length human SMN1 gene. Recently, OA was approved for the treatment of SMA by the U.S. Food and Drug Administration and the European Medicines Agency. Since the presence of neutralizing antibodies caused by previous natural exposure to wild-type AAVs may impair the efficiency of AAV-mediated gene transfer, and thus reduce the therapeutic benefit of the gene therapy, an AAV9-binding antibody titer of >1:50 was defined as a surrogate exclusion criterion in pivotal OA clinical trials. However, these studies were exclusively conducted in infants and children. Since data on anti-AAV9 antibody titers in adults are generally sparse and not available for adult patients with SMA, we determined the prevalence of anti-AAV9 antibodies in sera of adult individuals with SMA to evaluate the feasibility of AAV9-mediated gene therapy in this cohort. In our study population of 69 adult patients with SMA type 2 and type 3 from four German academic sites, only three patients (4.3%) had an elevated anti-AAV9 antibody titer of >1:50. The prevalence of anti-AAV9 antibodies did not increase with age. The low and age-independent prevalence of anti-AAV9 antibodies in our cohort provides evidence that gene therapy with intravenous administered recombinant AAV9 vectors (rAAV9) might be feasible in adult patients with SMA, regardless of the patients' sex, SMA type, walking ability, or ventilatory status. This could also apply to the treatment of other inherited neurological diseases with rAAV9.

Development of a low-seroprevalence, αvβ6 integrin-selective virotherapy based on human adenovirus type 10

Oncolytic virotherapies (OV) hold immense clinical potential. OV based on human adenoviruses (HAdV) derived from HAdV with naturally low rates of pre-existing immunity will be beneficial for future clinical translation. We generated a low-seroprevalence HAdV-D10 serotype vector incorporating an αvβ6 integrin-selective peptide, A20, to target αvβ6-positive tumor cell types. HAdV-D10 has limited natural tropism. Structural and biological studies of HAdV-D10 knob protein highlighted low-affinity engagement with native adenoviral receptors CAR and sialic acid. HAdV-D10 fails to engage blood coagulation factor X, potentially eliminating "off-target" hepatic sequestration in vivo. We engineered an A20 peptide that selectively binds αvβ6 integrin into the DG loop of HAdV-D10 fiber knob. Assays in αvβ6+ cancer cell lines demonstrated significantly increased transduction mediated by αvβ6-targeted variants compared with controls, confirmed microscopically. HAdV-D10.A20 resisted neutralization by neutralizing HAdV-C5 sera. Systemic delivery of HAdV-D10.A20 resulted in significantly increased GFP expression in BT20 tumors. Replication-competent HAdV-D10.A20 demonstrated αvβ6 integrin-selective cell killing in vitro and in vivo. HAdV-D10 possesses characteristics of a promising virotherapy, combining low seroprevalence, weak receptor interactions, and reduced off-target uptake. Incorporation of an αvβ6 integrin-selective peptide resulted in HAdV-D10.A20, with significant potential for clinical translation.

Immunogenicity of Novel AAV Capsids for Retinal Gene Therapy

Objectives: AAV vectors are widely used in gene therapy, but the prevalence of neutralizing antibodies raised against AAV serotypes in the course of a natural infection, as well as innate and adaptive immune responses induced upon vector administration, is still considered an important limitation. In ocular gene therapy, vectors applied subretinally bear the risk of retinal detachment or vascular leakage. Therefore, new AAV vectors that are suitable for intravitreal administration for photoreceptor transduction were developed. Methods: Here, we compared human immune responses from donors with suspected previous AAV2 infections to the new vectors AAV2.GL and AAV2.NN—two capsid peptide display variants with an enhanced tropism for photoreceptors—with the parental serotype AAV2 (AAV2 WT). We investigated total and neutralizing antibodies, adaptive and innate cellular immunogenicity determined by immunofluorescence staining and flow cytometry, and cytokine secretion analyzed with multiplex beads. Results: While we did not observe obvious differences in overall antibody binding, variants—particularly AAV2.GL—were less sensitive to neutralizing antibodies than the AAV2 WT. The novel variants did not differ from AAV2 WT in cellular immune responses and cytokine production in vitro. Conclusion: Due to their enhanced retinal tropism, which allows for dose reduction, the new vector variants are likely to be less immunogenic for gene therapy than the parental AAV2 vector.

Age-stratified adeno-associated virus serotype 3 neutralizing and total antibody prevalence in hemophilia A patients from India

Gene therapy using adeno-associated virus (AAV) vector offers a new treatment option for individuals with monogenetic disorders. The major bottleneck is the presence of pre-existing anti-AAV antibodies, which impacts its use. Even very low titers of neutralizing antibodies (NAb) to capsids from natural AAV infections have been reported to inhibit the transduction of intravenously administered AAV in animal models and are associated with limited efficacy in human trials. Assessing the level of pre-existing NAb is important for determining the primary eligibility of patients for AAV vector-based gene therapy clinical trials. Techniques used to screen AAV-antibodies include AAV capsid ELISA and transduction inhibition assay (TIA) for detecting total capsid-binding (TAb) and Nab, respectively. In this study, we screened 521 individuals with hemophilia A from India for TAb and NAb using ELISA and TIA, respectively. The prevalence of TAb and NAb in hemophilia A patients from India were 96 % and 77.5%, respectively. There was a significant increase in anti-AAV3 NAb prevalence with age in the hemophilia A patient group from India. There was a trend in anti-AAV3 TAb positivity between the pediatric age group (94.4%) and the adult age group (97.4%). This article is protected by copyright. All rights reserved.

The effect of rapamycin and ibrutinib on antibody responses to adeno-associated virus vector-mediated gene transfer

Adeno-associated virus (AAV) vector-mediated gene transfer is lessening the impact of monogenetic disorders. Human AAV gene therapy recipients commonly mount immune responses to AAV or the encoded therapeutic protein, which requires transient immunosuppression. Most efforts to date have focused on blunting AAV capsid-specific T cell responses, which have been implicated in elimination of AAV transduced cells. Here we explore the use of immunosuppressants, rapamycin given alone or in combination with ibrutinib to inhibit AAV vector- or transgene product-specific antibody responses. Our results show that rapamycin or ibrutinib given alone reduce primary antibody responses against AAV capsid but the combination of rapamycin and ibrutinib is more effective, blunts recall responses, and reduces numbers of circulating antibody-secreting plasma cells. The drugs fail to lower B cell memory formation or to reduce the inhibitory effects of pre-existing AAV capsid-specific antibodies on transduction efficiency.

Middle East Respiratory Syndrome coronavirus vaccine development: updating clinical studies using platform technologies

Middle East Respiratory Syndrome coronavirus (MERS-CoV), a contagious zoonotic virus, causes severe respiratory infection with a case fatality rate of approximately 35% in humans. Intermittent sporadic cases in communities and healthcare facility outbreaks have continued to occur since its first identification in 2012. The World Health Organization has declared MERS-CoV a priority pathogen for worldwide research and vaccine development due to its epidemic potential and the insufficient countermeasures available. The Coalition for Epidemic Preparedness Innovations is supporting vaccine development against emerging diseases, including MERS-CoV, based on platform technologies using DNA, mRNA, viral vector, and protein subunit vaccines. In this paper, we review the usefulness and structure of a spike glycoprotein as a MERS-CoV vaccine candidate molecule, and provide an update on the status of MERS-CoV vaccine development. Vaccine candidates based on both DNA and viral vectors coding MERS-CoV spike gene have completed early phase clinical trials. A harmonized approach is required to assess the immunogenicity of various candidate vaccine platforms. Platform technologies accelerated COVID-19 vaccine development and can also be applied to developing vaccines against other emerging viral diseases.

Convection-Enhanced Delivery in Children: Techniques and Applications

Since its first description in 1994, convection-enhanced delivery (CED) has become a reliable method of administering drugs directly into the brain parenchyma. More predictable and effective than simple diffusion, CED bypasses the challenging boundary of the blood brain barrier, which has frustrated many attempts at delivering large molecules or polymers into the brain parenchyma. Although most of the clinical work with CED has been carried out on adults with incurable neoplasms, principally glioblastoma multiforme, an increasing number of studies have recognized its potential for paediatric applications, which now include treatment of currently incurable brain tumours such as diffuse intrinsic pontine glioma (DIPG), as well as metabolic and neurotransmitter diseases. The roadmap for the development of hardware and use of pharmacological agents in CED has been well-established, and some neurosurgical centres throughout the world have successfully undertaken clinical trials, admittedly mostly early phase, on the basis of in vitro, small animal and large animal pre-clinical foundations. However, the clinical efficacy of CED, although theoretically logical, has yet to be unequivocally demonstrated in a clinical trial; this applies particularly to neuro-oncology.This review aims to provide a broad description of the current knowledge of CED as applied to children. It reviews published studies of paediatric CED in the context of its wider history and developments and underlines the challenges related to the development of hardware, the selection of pharmacological agents, and gene therapy. It also reviews the difficulties related to the development of clinical trials involving CED and looks towards its potential disease-modifying opportunities in the future.

Prevalence of pre-existing neutralizing antibodies against AAV serotypes 1, 2, 5, 6, 8, and 9 in sera of different pig strains

Pre-existing neutralizing antibodies (NAb) to adeno-associated virus (AAV) may diminish the efficacy of AAV-based therapies depending on the titer. To support gene therapy studies in pigs, the seroprevalence of NAb to AAV 1, 2, 5, 6, 8, and 9 serotypes were assessed in the sera of 3 different strains of pigs consisting of 60 Norsvin Topigs-20 strain, 22 Gottingen minipigs, and 40 Yucatan minipigs. Cell-based NAb assays were developed for various AAV serotypes. The sera were tested for NAb in a Lec-2 cell line for AAV9 vector and in a COS-7 cell line for the other AAV serotypes. In the 60 Topigs-20 strain aged 2 to 4 years old, 100% were positive for AAV2 NAb, 45 % positive for AAV6 NAb, and ~20% positive for each of AAV1, 5, 8, and 9 NAb. These data showed that approximately 80% of Norsvin Topigs-20 pigs evaluated were seronegative for pre-existing NAb to the AAV1, 5, 8, and 9 serotypes, respectively. In 22 Gottingen minipigs at 5-6 months of age, serum AAV-serotype specific NAb co-existed with that of various other AAV serotypes at 32 to 46 % between two serotypes. These results suggested that coexisting NAb resulted either from multiple AAV serotype co-infection or from one (or more) serotypes that can cross-react with other AAV serotypes in some minipigs. Among the 40 Yucatan minipigs, 20 of the minipigs were less than 3 months old and were all negative for NAb against AAV5, 8 and 9, and only one of these 20 pigs was positive to AAV1 and 6. We further determined the titers in those positive pigs and found most Gottingen minipigs had low titer at 1:20, whereas some of Topigs-20 pigs had titers between 1:80 to 1: 320, and some of Yucatan pigs had titers between 1: 160 to 1: 640. These results suggested that the majority of the pigs in the three strains would be amenable to gene therapy study using AAV1, AAV5, AAV8, and AAV9 and that prescreening on circulating AAV antibodies could be helpful before inclusion of pigs into studies.

Seroprevalence and molecular characterization of human respiratory syncytial virus and human adenovirus among children in Ado-Ekiti, Nigeria

In children, the respiratory syncytial virus and adenovirus majorly cause acute respiratory infections. The study evaluated the seroprevalence and conducted the molecular characterization of human respiratory syncytial virus (HRSV) and human adenovirus (HAdV) among children. Venous blood, nasopharyngeal, and oropharyngeal swabs were collected from children presenting with acute respiratory infections in a tertiary health facility in Ado-Ekiti, Nigeria. A serological investigation was carried out on the sera samples for the detection of anti-HRSV immunoglobulin M (IgM), anti-HRSV IgG, anti-HAdV IgM, and anti-HAdV IgG using ELISA (enzyme-linked immunosorbent assay) kits. The amplification and sequencing of HRSV and HAdV were carried out using specific primer pairs that targeted the glycoprotein (G) gene of HRSV and the hexon gene of HAdV, respectively. The seroprevalence of HRSV IgG and IgM was 73% and 7.5%, respectively, while the seroprevalence of HAdV IgG and IgM was 98.5% and 8.5%, respectively. The age of enrolled children, presence of fever, and cough were associated (p < 0.05) with the infection. HRSV subtype B (HRSV-B) (13.3%), and species of HAdV (Mastadenovirus B and C) (11.7%) were detected among the studied population. There was no viral coinfection with both HRSV and HAdV. In infancy and early childhood, HRSV-B, HAdV species B and C are common etiologic agents of respiratory infections as reported in this study. Further studies on molecular characterization of respiratory tract viruses including circulating respiratory syncytial virus and adenovirus are hereby advocated.

Adeno-Associated Viruses (AAV) and Host Immunity - A Race Between the Hare and the Hedgehog

Adeno-associated viruses (AAV) have emerged as the lead vector in clinical trials and form the basis for several approved gene therapies for human diseases, mainly owing to their ability to sustain robust and long-term in vivo transgene expression, their amenability to genetic engineering of cargo and capsid, as well as their moderate toxicity and immunogenicity. Still, recent reports of fatalities in a clinical trial for a neuromuscular disease, although linked to an exceptionally high vector dose, have raised new caution about the safety of recombinant AAVs. Moreover, concerns linger about the presence of pre-existing anti-AAV antibodies in the human population, which precludes a significant percentage of patients from receiving, and benefitting from, AAV gene therapies. These concerns are exacerbated by observations of cellular immune responses and other adverse events, including detrimental off-target transgene expression in dorsal root ganglia. Here, we provide an update on our knowledge of the immunological and molecular race between AAV (the “hedgehog”) and its human host (the “hare”), together with a compendium of state-of-the-art technologies which provide an advantage to AAV and which, thus, promise safer and more broadly applicable AAV gene therapies in the future.

Structurally Mapping Antigenic Epitopes of Adeno-Associated Virus 9: Development of Antibody Escape Variants

Adeno-associated viruses (AAV) serve as vectors for therapeutic gene delivery. AAV9 vectors have been FDA approved, as Zolgensma®, for the treatment of spinal muscular atrophy and is being evaluated in clinical trials for the treatment of neurotropic and musculotropic diseases. A major hurdle for AAV-mediated gene delivery is the presence of pre-existing neutralizing antibodies in 40 to 80% of the general population. These pre-existing antibodies can reduce therapeutic efficacy through viral neutralization, and the size of the patient cohort eligible for treatment. In this study, cryo-electron microscopy and image reconstruction was used to define the epitopes of five anti-AAV9 monoclonal antibodies (MAbs); ADK9, HL2368, HL2370, HL2372, and HL2374, on the capsid surface. Three of these, ADK9, HL2370, and HL2374, bound on or near the icosahedral 3-fold axes, HL2368 to the 2/5-fold wall, and HL2372 to the region surrounding the 5-fold axes. Pseudo-atomic modeling enabled the mapping and identification of antibody contact amino acids on the capsid, including S454 and P659. These epitopes overlap with previously defined parvovirus antigenic sites. Capsid amino acids critical for the interactions were confirmed by mutagenesis followed by biochemical assays testing recombinant AAV9 (rAAV9) variants capable of escaping recognition and neutralization by the parental MAbs. These variants retained parental tropism and had similar or improved transduction efficiency compared to AAV9. These engineered rAAV9 variants could expand the patient cohort eligible for AAV9-mediated gene delivery by avoiding pre-existing circulating neutralizing antibodies. IMPORTANCE The use of recombinant AAVs (rAAVs) as delivery vectors for therapeutic genes is becoming increasingly popular, especially following the FDA approval of Luxturna® and Zolgensma®, based on serotypes AAV2 and AAV9, respectively. However, high titer anti-AAV neutralizing antibodies in the general population, exempts patients from treatment. The goal of this study is to circumvent this issue by creating AAV variant vectors not recognized by pre-existing neutralizing antibodies. The mapping of the antigenic epitopes of five different monoclonal antibodies (MAbs) on AAV9, to recapitulate a polyclonal response, enabled the rational design of escape variants with minimal disruption to cell tropism and gene expression. This study, which included four newly developed and now commercially available MAbs, provides a platform for the engineering of rAAV9 vectors that can be used to deliver genes to patients with pre-exiting AAV antibodies.

Nucleic acid delivery for therapeutic applications

Recent medical advances have exploited the ability to address a given disease at the underlying level of transcription and translation. These treatment paradigms utilize nucleic acids - including short interfering RNA (siRNA), microRNA (miRNA), antisense oligonucleotides (ASO), and messenger RNA (mRNA) - to achieve a desired outcome ranging from gene knockdown to induced expression of a selected target protein. Towards this end, numerous strategies for encapsulation or stabilization of various nucleic acid structures have been developed in order to achieve intracellular delivery. In this review, we discuss several therapeutic applications of nucleic acids directed towards specific diseases and tissues of interest, in particular highlighting recent technologies which have reached late-stage clinical trials and received FDA approval.

Adenoviral vector-based platforms for developing effective vaccines to combat respiratory viral infections

Since the development of the first vaccine against smallpox over two centuries ago, vaccination strategies have been at the forefront of significantly impacting the incidences of infectious diseases globally. However, the increase in the human population, deforestation and climate change, and the rise in worldwide travel have favored the emergence of new viruses with the potential to cause pandemics. The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is a cruel reminder of the impact of novel pathogens and the suboptimal capabilities of conventional vaccines. Therefore, there is an urgent need to develop new vaccine strategies that allow the production of billions of doses in a short duration and are broadly protective against emerging and re-emerging infectious diseases. Extensive knowledge of the molecular biology and immunology of adenoviruses (Ad) has favored Ad vectors as platforms for vaccine design. The Ad-based vaccine platform represents an attractive strategy as it induces robust humoral and cell-mediated immune responses and can meet the global demand in a pandemic situation. This review describes the status of Ad vector-based vaccines in preclinical and clinical studies for current and emerging respiratory viruses, particularly coronaviruses, influenza viruses and respiratory syncytial viruses.

Review: Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). Vaccine development approaches consist of viral vector vaccines, DNA vaccine, RNA vaccine, live attenuated virus, and recombinant proteins, which elicit a specific immune response. The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines. This is due to the fact that nano-based vaccines are stable, able to target, form images, and offer an opportunity to enhance the immune responses. The diameters of ultrafine nanoparticles are in the range of 1-100 nm. The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features. To be successful, nanomaterials must be uptaken into the cell, especially into the target and able to modulate cellular functions at the subcellular levels. The advantages of nano-based vaccines are the ability to protect a cargo such as RNA, DNA, protein, or synthesis substance and have enhanced stability in a broad range of pH, ambient temperatures, and humidity for long-term storage. Moreover, nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells. In this review, we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens. The discussion about their safe, effective, and affordable vaccines to immunize against COVID-19 will be highlighted.

Machine learning applications for therapeutic tasks with genomics data

Thanks to the increasing availability of genomics and other biomedical data, many machine learning algorithms have been proposed for a wide range of therapeutic discovery and development tasks. In this survey, we review the literature on machine learning applications for genomics through the lens of therapeutic development. We investigate the interplay among genomics, compounds, proteins, electronic health records, cellular images, and clinical texts. We identify 22 machine learning in genomics applications that span the whole therapeutics pipeline, from discovering novel targets, personalizing medicine, developing gene-editing tools, all the way to facilitating clinical trials and post-market studies. We also pinpoint seven key challenges in this field with potentials for expansion and impact. This survey examines recent research at the intersection of machine learning, genomics, and therapeutic development.

Evaluation of the Humoral Response to Adeno-Associated Virus-Based Gene Therapy Modalities Using Total Antibody Assays

The number of viral vector-based gene therapies (GTx) continues to grow with two products (Zolgensma® and Luxturna®) approved in the USA as of March 2021. To date, the most commonly used vectors are adeno-associated virus-based (AAV). The pre-existing humoral immunity against AAV (anti-AAV antibodies) has been well described and is expected as a consequence of prior AAV exposure. Anti-AAV antibodies may present an immune barrier to successful AAV transduction and hence negatively impact clinical efficacy and may also result in adverse events (AEs) due to the formation of large immune complexes. Patients may be screened for the presence of anti-AAV antibodies, including neutralizing (NAb) and total binding antibodies (TAb) prior to treatment with the GTx. Recommendations for the development and validation of anti-AAV NAb detection methods have been presented elsewhere. This manuscript covers considerations related to anti-AAV TAb-detecting protocols, including the advantages of the use of TAb methods, selection of assay controls and reagents, and parameters critical to monitoring assay performance. This manuscript was authored by a group of scientists involved in GTx development representing eleven organizations. It is our intent to provide recommendations and guidance to industry sponsors, academic laboratories, and regulatory agencies working on AAV-based GTx viral vector modalities with the goal of achieving a more consistent approach to anti-AAV TAb assessment.

Inhalation monoclonal antibody therapy: a new way to treat and manage respiratory infections

The route of administration of a therapeutic agent has a substantial impact on its success. Therapeutic antibodies are usually administered systemically, either directly by intravenous route, or indirectly by intramuscular or subcutaneous injection. However, treatment of diseases contained within a specific tissue necessitates a better alternate route of administration for targeting localised infections. Inhalation is a promising non-invasive strategy for antibody delivery to treat respiratory maladies because it provides higher concentrations of antibody in the respiratory airways overcoming the constraints of entry through systemic circulation and uncertainity in the amount reaching the target tissue. The nasal drug delivery route is one of the extensively researched modes of administration, and nasal sprays for molecular drugs are deemed successful and are presently commercially marketed. This review highlights the current state and future prospects of inhaled therapies, with an emphasis on the use of monoclonal antibodies for the treatment of respiratory infections, as well as an overview of their importance, practical challenges, and clinical trial outcomes.Key points• Immunologic strategies for preventing mucosal transmission of respiratory pathogens.• Mucosal-mediated immunoprophylaxis could play a major role in COVID-19 prevention.• Applications of monoclonal antibodies in passive immunisation.

Emerging Gene and Small Molecule Therapies for the Neurodevelopmental Disorder Angelman Syndrome

Angelman syndrome (AS) is a rare (~1:15,000) neurodevelopmental disorder characterized by severe developmental delay and intellectual disability, impaired communication skills, and a high prevalence of seizures, sleep disturbances, ataxia, motor deficits, and microcephaly. AS is caused by loss-of-function of the maternally inherited UBE3A gene. UBE3A is located on chromosome 15q11-13 and is biallelically expressed throughout the body but only maternally expressed in the brain due to an RNA antisense transcript that silences the paternal copy. There is currently no cure for AS, but advancements in small molecule drugs and gene therapies offer a promising approach for the treatment of the disorder. Here, we review AS and how loss-of-function of the maternal UBE3A contributes to the disorder. We also discuss the strengths and limitations of current animal models of AS. Furthermore, we examine potential small molecule drug and gene therapies for the treatment of AS and associated challenges faced by the therapeutic design. Finally, gene therapy offers the opportunity for precision medicine in AS and advancements in the treatment of this disorder can serve as a foundation for other single-gene neurodevelopmental disorders.

Expert recommendations and clinical considerations in the use of onasemnogene abeparvovec gene therapy for spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive, neurodegenerative disease caused by biallelic mutations in the survival motor neuron 1 (SMN1) gene. SMA is characterized by motor neuron degeneration, resulting in progressive muscle atrophy and weakness. Before the emergence of disease-modifying therapies, children with the most severe form of SMA would never achieve the ability to sit independently. Only 8% survived beyond 20 months of age without permanent ventilator support. One such therapy, onasemnogene abeparvovec, an adeno-associated virus-based gene replacement therapy, delivers functional human SMN through a one-time intravenous infusion. In addition to substantially improving survival, onasemnogene abeparvovec was found to increase motor milestone attainment and reduce the need for respiratory or nutritional support in many patients. This expert opinion provides recommendations and practical considerations on the patient-centered decisions to use onasemnogene abeparvovec. Recommendations include the need for patient-centered multidisciplinary care and patient selection to identify those with underlying medical conditions or active infections to reduce risks. We also describe the importance of retesting patients with elevated anti-adeno-associated virus serotype 9 antibodies. Recommendations for prednisolone tapering and monitoring for potential adverse events, including hepatotoxicity and thrombotic microangiopathy, are described. The need for caregiver education on managing day-to-day care at time of treatment and patient- and family-centered discussions on realistic expectations are also recommended. We detail the importance of following standard-of-care guidance and long-term monitoring of all children with SMA who have received one or more disease-modifying therapy using registries. We also highlight the need for presymptomatic or early symptomatic treatment of this disorder.

Therapeutic liver repopulation by transient acetaminophen selection of gene-modified hepatocytes

Gene therapy by integrating vectors is promising for monogenic liver diseases, especially in children where episomal vectors remain transient. However, reaching the therapeutic threshold with genome-integrating vectors is challenging. Therefore, we developed a method to expand hepatocytes bearing therapeutic transgenes. The common fever medicine acetaminophen becomes hepatotoxic via cytochrome p450 metabolism. Lentiviral vectors with transgenes linked in cis to a Cypor shRNA were administered to neonatal mice. Hepatocytes lacking the essential cofactor of Cyp enzymes, NADPH-cytochrome p450 reductase (Cypor), were selected in vivo by acetaminophen administration, replacing up to 50% of the hepatic mass. Acetaminophen treatment of the mice resulted in over 30-fold expansion of transgene-bearing hepatocytes and achieved therapeutic thresholds in hemophilia B and phenylketonuria. We conclude that therapeutically modified hepatocytes can be selected safely and efficiently in preclinical models with a transient regimen of moderately hepatotoxic acetaminophen.

Prevalence of Adeno-Associated Virus 3 Capsid Binding and Neutralizing Antibodies in Healthy and Hemophilia B Individuals from India

Adeno-associated virus (AAV) vector-based gene therapy offers a new treatment option for individuals with hemophilia. Pre-existing anti-AAV antibodies significantly impact the use of AAV vectors. Even relatively low titers of AAV neutralizing antibodies (NAb) from natural AAV infections against the capsid have been shown to inhibit the transduction of intravenously administered AAV in animal models and were associated with limited efficacy in human trials. This is important for determining the primary eligibility of patients for AAV vector-based gene therapy clinical trials. Current techniques to screen AAV antibodies include AAV capsid enzyme-linked immunosorbent assay (ELISA) for total antibodies and a transduction inhibition assay (TIA) for NAb. This study developed and screened total capsid binding anti-AAV3 antibodies by using ELISA and determined NAb levels by TIA using mCherry flow cytometry in healthy individuals with hemophilia B in India. One hundred and forty-three apparently healthy controls and 92 individuals with hemophilia B were screened. The prevalence of total and NAb in healthy controls was 79.7% and 65%, respectively; the prevalence of total and NAb in patients with hemophilia B for AAV3 was 92.4% and 91.3%, respectively.

Evolutionary Timeline of Genetic Delivery and Gene Therapy

There are more than 3,500 genes that are being linked to hereditary diseases or correlated with an elevated risk of certain illnesses. As an alternative to conventional treatments with small molecule drugs, gene therapy has arisen as an effective treatment with the potential to not just alleviate disease conditions but also cure them completely. In order for these treatment regimens to work, genes or editing tools intended to correct diseased genetic material must be efficiently delivered to target sites. There have been many techniques developed to achieve such a goal. In this article, we systematically review a variety of gene delivery and therapy methods that include physical methods, chemical and biochemical methods, viral methods, and genome editing. We discuss their historical discovery, mechanisms, advantages, limitations, safety, and perspectives.

T Cell-Mediated Immune Responses to AAV and AAV Vectors

Adeno-associated virus (AAV)-mediated gene transfer has benefited patients with inherited diseases, such as hemophilia B, by achieving long-term expression of the therapeutic transgene. Nevertheless, challenges remain due to rejection of AAV-transduced cells, which in some, but not all, patients can be prevented by immunosuppression. It is assumed that CD8+ T cells induced by natural infections with AAVs are recalled by the AAV vector's capsid and upon activation eliminate cells expressing the degraded capsid antigens. Alternatively, it is feasible that AAV vectors, especially if given at high doses, induce de novo capsid- or transgene product-specific T cell responses. This chapter discusses CD8+ T cell responses to AAV infections and AAV gene transfer and avenues to prevent their activation or block their effector functions.

Pharmacotherapeutics of SARS-CoV-2 Infections

The COVID-19 pandemic has affected more than 38 million people world-wide by person to person transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therapeutic and preventative strategies for SARS-CoV-2 remains a significant challenge. Within the past several months, effective treatment options have emerged and now include repurposed antivirals, corticosteroids and virus-specific antibodies. The latter has included convalescence plasma and monoclonal antibodies. Complete viral eradication will be achieved through an effective, safe and preventative vaccine. To now provide a comprehensive summary for each of the pharmacotherapeutics and preventative strategies being offered or soon to be developed for SARS-CoV-2.

Delivery of transcription factors as modulators of cell differentiation

Fundamental studies performed during the last decades have shown that cell fate is much more plastic than previously considered, and technologies for its manipulation are a keystone for many new tissue regeneration therapies. Transcription factors (TFs) are DNA-binding proteins that control gene expression, and they have critical roles in the control of cell fate and other cellular behavior. TF-based therapies have much medical potential, but their use as drugs depends on the development of suitable delivery technologies that can help them reach their action site inside of the cells. TFs can be used either as proteins or encoded in polynucleotides. When used in protein form, many TFs require to be associated to a cell-penetrating peptide or another transduction domain. As polynucleotides, they can be delivered either by viral carriers or by non-viral systems such as polyplexes and lipoplexes. TF-based therapies have extensively shown their potential to solve many tissue-engineering problems, including bone, cartilage and cardiac regeneration. Yet, their use has expanded beyond regenerative medicine to other prominent disease areas such as cancer therapy and immunomodulation. This review summarizes some of the delivery options for effective TF-based therapies and their current main applications.

Lipocalin 13 enhances insulin secretion but is dispensable for systemic metabolic control

Thorough preclinical evaluation reveals a negligible role of lipocalin 13 in systemic glucose and lipid metabolism.

Members of the lipocalin protein family serve as biomarkers for kidney disease and acute phase inflammatory reactions, and are under preclinical development for the diagnosis and therapy of allergies. However, none of the lipocalin family members has made the step into clinical development, mostly due to their complex biological activity and the lack of in-depth mechanistic knowledge. Here, we show that the hepatokine lipocalin 13 (LCN13) triggers glucose-dependent insulin secretion and cell proliferation of primary mouse islets. However, inhibition of endogenous LCN13 expression in lean mice did not alter glucose and lipid homeostasis. Enhanced hepatic secretion of LCN13 in either diet-induced or genetic obesity led to no discernible impact on systemic glucose and lipid metabolism, neither in preventive nor therapeutic setting. Of note, loss or forced LCN13 hepatic secretion did not trigger any compensatory regulation of related lipocalin family members. Together, these data are in stark contrast to the suggested gluco-regulatory and therapeutic role of LCN13 in obesity, and imply complex regulatory steps in LCN13 biology at the organismic level mitigating its principal insulinotropic effects.

Mutant myogenin promoter-controlled oncolytic adenovirus selectively kills PAX3-FOXO1-positive rhabdomyosarcoma cells

The PAX3-FOXO1 fusion gene functions as a transactivator and increases expression of many cancer-related genes. These lead to metastases and other unfavorable outcomes for alveolar rhabdomyosarcoma (ARMS) patients. In order to target ARMS with the PAX3-FOXO1 transactivator, we developed an Oncolytic Adenovirus (OAd) regulated by the myogenin (pMYOG) promoter with a mutation in the Myocyte Enhancer Factor-2 binding site (mMEF2) in this study. The expression of MYOG in the two RMS cell lines (Rh30; PAX3-FOXO1-positive, RD; PAX3-FOXO1-negative) is about 1,000 times higher than normal skeletal muscle cell (SkMC). Ad5/3-pMYOG(S)-mMEF2 (short-length pMYOG-controlled OAd with mMEF2) showed strong replication and cytocidal effect in Rh30, but to a much lesser extent in RD. Ad5/3-pMYOG(S) (pMYOG-controlled OAd with native pMYOG) showed similar effects in RD and Rh30. Neither virus killed SkMC, indicating that Ad5/3-pMYOG(S)-mMEF2 selectively replicates and kills cells with PAX3-FOXO1. Additionally, Ad5/3-pMYOG(S)-mMEF2 showed replication and spread in vitro as well as tumor growth suppression and intratumoral viral spread in vivo, selectively in Rh30 not in RD. Our findings revealed that Ad5/3-pMYOG(S)-mMEF2 shows a promise as a safe and potent therapy to improve treatment in PAX3-FOXO1-positive ARMSs.

A COVID-19 Vaccine: Big Strides Come with Big Challenges

As of 8 January 2021, there were 86,749,940 confirmed coronavirus disease 2019 (COVID-19) cases and 1,890,342 COVID-19-related deaths worldwide, as reported by the World Health Organization (WHO). In order to address the COVID-19 pandemic by limiting transmission, an intense global effort is underway to develop a vaccine against SARS-CoV-2. The development of a safe and effective vaccine usually requires several years of pre-clinical and clinical stages of evaluation and requires strict regulatory approvals before it can be manufactured in bulk and distributed. Since the global impact of COVID-19 is unprecedented in the modern era, the development and testing of a new vaccine are being expedited. Given the high-level of attrition during vaccine development, simultaneous testing of multiple candidates increases the probability of finding one that is effective. Over 200 vaccines are currently in development, with over 60 candidate vaccines being tested in clinical trials. These make use of various platforms and are at different stages of development. This review discusses the different phases of vaccine development and the various platforms in use for candidate COVID-19 vaccines, including their progress to date. The potential challenges once a vaccine becomes available are also addressed.

COVID-19: Coronavirus Vaccine Development Updates

Coronavirus Disease 2019 (COVID-19) is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), a newly emerged coronavirus, and has been pandemic since March 2020 and led to many fatalities. Vaccines represent the most efficient means to control and stop the pandemic of COVID-19. However, currently there is no effective COVID-19 vaccine approved to use worldwide except for two human adenovirus vector vaccines, three inactivated vaccines, and one peptide vaccine for early or limited use in China and Russia. Safe and effective vaccines against COVID-19 are in urgent need. Researchers around the world are developing 213 COVID-19 candidate vaccines, among which 44 are in human trials. In this review, we summarize and analyze vaccine progress against SARS-CoV, Middle-East respiratory syndrome Coronavirus (MERS-CoV), and SARS-CoV-2, including inactivated vaccines, live attenuated vaccines, subunit vaccines, virus like particles, nucleic acid vaccines, and viral vector vaccines. As SARS-CoV-2, SARS-CoV, and MERS-CoV share the common genus, Betacoronavirus, this review of the major research progress will provide a reference and new insights into the COVID-19 vaccine design and development.

Gene Replacement Therapy: A Primer for the Health-system Pharmacist

PURPOSE

Comprehensive review of gene replacement therapy with guidance and expert opinion on handling and administration for pharmacists.

SUMMARY

There are currently ∼2600 gene therapy clinical trials worldwide and 4 Food and Drug Administration (FDA)-approved gene therapy products available in the United States. Gene therapy and its handling are different from other drugs; however, there is a lack of guidance from the National Institutes of Health (NIH), FDA, Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), and professional associations regarding their pharmaceutical application. Although the NIH stratifies the backbone biologicals of viral vectors in gene therapies into risk groups, incomplete information regarding minimization of exposure and reduction of risk exists. In the absence of defined guidance, individual institutions develop their own policies and procedures, which often differ and are often outdated. This review provides expert opinion on the role of pharmacists in institutional preparedness, as well as gene therapy handling and administration. A suggested infrastructural model for gene replacement therapy handling is described, including requisite equipment acquisition and standard operating procedure development. Personnel, patient, and caregiver education and training are discussed.

CONCLUSION

Pharmacists have a key role in the proper handling and general management of gene replacement therapies, identifying risk level, establishing infrastructure, and developing adequate policies and protocols, particularly in the absence of consensus guidelines for the handling and transport of gene replacement therapies.

Nanocarrier Mediated siRNA Delivery Targeting Stem Cell Differentiation

Stem cell-based regenerative medicine holds exceptional therapeutic potential and hence the development of efficient techniques to enhance control over the rate of differentiation has been the focus of active research. One of the strategies to achieve this involves delivering siRNA into stem cells and exploiting the RNA interference (RNAi) mechanism. Transport of siRNA across the cell membrane is a challenge due to its anionic property, especially in primary human cells and stem cells. Moreover, naked siRNA incites immune responses, may cause off-target effects, exhibits low stability and is easily degraded by endonucleases in the bloodstream. Although siRNA delivery using viral vectors and electroporation has been used in stem cells, these methods demonstrate low transfection efficiency, cytotoxicity, immunogenicity, events of integration and may involve laborious customization. With the advent of nanotechnology, nanocarriers which act as novel gene delivery vehicles designed to overcome the problems associated with safety and practicality are being developed. The various nanomaterials that are currently being explored and discussed in this review include liposomes, carbon nanotubes, quantum dots, protein and peptide nanocarriers, magnetic nanoparticles, polymeric nanoparticles, etc. These nanodelivery agents exhibit advantages such as low immunogenic response, biocompatibility, design flexibility allowing for surface modification and functionalization, and control over the surface topography for achieving the desired rate of siRNA delivery and improved gene knockdown efficiency. This review also includes discussion on siRNA co-delivery with imaging agents, plasmid DNA, drugs etc. to achieve combined diagnostic and enhanced therapeutic functionality, both for in vitro and in vivo applications.

Separating Empty and Full Recombinant Adeno-Associated Virus Particles Using Isocratic Anion Exchange Chromatography

The development of recombinant adeno-associated virus (rAAV) gene therapies is becoming an increasing priority in the biotherapeutic landscape. One of the challenges associated with the production of rAAV is the formation of empty AAV particles that do not contain a therapeutic gene. The concerns about the impact of empty particles on clinical safety and rAAV-mediated gene expression have necessitated the development of purification processes to remove these species. The development of a robust and scalable purification process to separate empty and full AAV particles at large scale remains a challenge. In this study, a novel anion exchange chromatography process based on isocratic wash and elution steps to enrich full rAAV2 particles is presented. An operating design space is identified to ensure the robustness of the process. The isocratic chromatography provides several advantages over the traditional shallow linear gradient elution, including lower buffer consumption, smaller intermediate pool volumes, and more robust manufacturing.

New Directions in Pulmonary Gene Therapy

The lung has long been a target for gene therapy, yet efficient delivery and phenotypic disease correction has remained challenging. Although there have been significant advancements in gene therapies of other organs, including the development of several ex vivo therapies, in vivo therapeutics of the lung have been slower to transition to the clinic. Within the past few years, the field has witnessed an explosion in the development of new gene addition and gene editing strategies for the treatment of monogenic disorders. In this review, we will summarize current developments in gene therapy for cystic fibrosis, alpha-1 antitrypsin deficiency, and surfactant protein deficiencies. We will explore the different gene addition and gene editing strategies under investigation and review the challenges of delivery to the lung.

Isolating Human Monoclonal Antibodies Against Adeno-Associated Virus From Donors With Pre-existing Immunity

With the advent of single B-cell cloning technology, we can isolate antibodies against virtually any antigen to study the interaction of a given pathogen with the immune system and develop novel therapeutic strategies. Antibodies directed against the capsid of adeno-associated viruses (AAV) are a significant obstacle to effectively leveraging AAV as a gene-delivery vector in seropositive individuals. In order to design next-generation vectors that can evade neutralization by these antibodies, studies have mapped the epitopes of mouse monoclonal antibodies generated by immunization with AAV. Although these studies provide critical information regarding capsid immunogenicity, they cannot address (1) differences in the antibody repertoire generated in humans following AAV natural infection; or (2) how reactions can vary when generated in response to vector administration. Here, we isolated and evaluated a panel of novel, fully human anti-AAV antibodies by cloning single memory B cells from a seropositive normal donor. We have validated the utility of this approach to study AAV immunology. Our goal is to leverage this knowledge to design novel AAV variants that can effectively transduce target tissues in individuals with AAV-neutralizing antibodies.

The Effects of Pre-Existing Antibodies on Live-Attenuated Viral Vaccines

Live-attenuated vaccines (LAVs) have achieved remarkable successes in controlling virus spread, as well as for other applications such as cancer immunotherapy. However, with rapid increases in international travel, globalization, geographic spread of viral vectors, and widespread use of vaccines, there is an increasing need to consider how pre-exposure to viruses which share similar antigenic regions can impact vaccine efficacy. Pre-existing antibodies, derived from either from maternal–fetal transmission, or by previous infection or vaccination, have been demonstrated to interfere with vaccine immunogenicity of measles, adenovirus, and influenza LAVs. Immune interference of LAVs can be caused by the formation of virus–antibody complexes that neutralize virus infection in antigen-presenting cells, or by the cross-linking of the B-cell receptor with the inhibitory receptor, FcγRIIB. On the other hand, pre-existing antibodies can augment flaviviral LAV efficacy such as that of dengue and yellow fever virus, especially when pre-existing antibodies are present at sub-neutralizing levels. The increased vaccine immunogenicity can be facilitated by antibody-dependent enhancement of virus infection, enhancing virus uptake in antigen-presenting cells, and robust induction of innate immune responses that promote vaccine immunogenicity. This review examines the literature on this topic and examines the circumstances where pre-existing antibodies can inhibit or enhance LAV efficacy. A better knowledge of the underlying mechanisms involved could allow us to better manage immunization in seropositive individuals and even identify possibilities that could allow us to exploit pre-existing antibodies to boost vaccine-induced responses for improved vaccine efficacy.