Sandra Iurescia

DNA Vaccines: Developing New Strategies against Cancer

Due to their rapid and widespread development, DNA vaccines have entered into a variety of human clinical trials for vaccines against various diseases including cancer. Evidence that DNA vaccines are well tolerated and have an excellent safety profile proved to be of advantage as many clinical trials combines the first phase with the second, saving both time and money. It is clear from the results obtained in clinical trials that such DNA vaccines require much improvement in antigen expression and delivery methods to make them sufficiently effective in the clinic. Similarly, it is clear that additional strategies are required to activate effective immunity against poorly immunogenic tumor antigens. Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspects that can be easily handled in the DNA vaccine technology. Several approaches have been investigated including DNA vaccine engineering, co-delivery of immunomodulatory molecules, safe routes of administration, prime-boost regimen and strategies to break the immunosuppressive networks mechanisms adopted by malignant cells to prevent immune cell function. Combined or single strategies to enhance the efficacy and immunogenicity of DNA vaccines are applied in completed and ongoing clinical trials, where the safety and tolerability of the DNA platform are substantiated. In this review on DNA vaccines, salient aspects on this topic going from basic research to the clinic are evaluated. Some representative DNA cancer vaccine studies are also discussed.

Epitope-driven DNA vaccine design employing immunoinformatics against B-cell lymphoma: A biotech's challenge

DNA vaccination has been widely explored to develop new, alternative and efficient vaccines for cancer immunotherapy. DNA vaccines offer several benefits such as specific targeting, use of multiple genes to enhance immunity and reduced risk compared to conventional vaccines. Rapid developments in molecular biology and immunoinformatics enable rational design approaches. These technologies allow construction of DNA vaccines encoding selected tumor antigens together with molecules to direct and amplify the desired effector pathways, as well as highly targeted vaccines aimed at specific epitopes. Reliable predictions of immunogenic T cell epitope peptides are crucial for rational vaccine design and represent a key problem in immunoinformatics. Computational approaches have been developed to facilitate the process of epitope detection and show potential applications to the immunotherapeutic treatment of cancer. In this review a number of different epitope prediction methods are briefly illustrated and effective use of these resources to support experimental studies is described. Epitope-driven vaccine design employs these bioinformatics algorithms to identify potential targets of vaccines against cancer. In this paper the selection of T cell epitopes to develop epitope-based vaccines, the need for CD4(+) T cell help for improved vaccines and the assessment of vaccine performance against tumor are reviewed. We focused on two applications, namely prediction of novel T cell epitopes and epitope enhancement by sequence modification, and combined rationale design with bioinformatics for creation of new synthetic mini-genes. This review describes the development of epitope-based DNA vaccines and their antitumor effects in preclinical research against B-cell lymphoma, corroborating the usefulness of this platform as a potential tool for cancer therapy. Achievements in the field of DNA vaccines allow to overcome hurdles to clinical translation. In a scenario where the vaccine industry is rapidly changing from a mostly empirical approach to a rational design approach, these new technologies promise to discover and develop high-value vaccines, creating a new opportunity for future markets.

Anti-tumor immunity induced by CDR3-based DNA vaccination in a murine B-cell lymphoma model

The idiotypic structure present on B-cell neoplasms is a tumor-specific antigen and an attractive target for immunotherapy. Here, the tumor protective effects recruited by CDR3-based DNA vaccines in the poorly immunogenic, highly aggressive 38C13 murine B-cell lymphoma model were evaluated. The regions belonging to the idiotypic V(H) and V(L) CDR3 sequences were chosen for the design of two synthetic mini-genes and arranged in high-level expression plasmids. Syngeneic C3H/HeN mice were immunized by intramuscular electroporation with pV(H)CDR3-IL-2 and pV(L)CDR3-IL-2 naked DNAs. This approach provided protection in about 60% of animals challenged with a 2-fold lethal dose of tumor cells, as opposed to non-survivors in control groups. Furthermore, a long-term survival was induced in these mice since they were still alive and tumor-free 4 months following tumor challenge. Analysis of the humoral immunity revealed the presence of antibodies reactive with the peptides encompassing the CDR3 sequences in the sera of vaccinated mice. Moreover, immune sera specifically reacted with the parental 38C13 tumor cells in flow cytometry assays, indicating that such immunization elicited anti-idiotypic antibodies. These findings provide a basis for exploring the use of CDR3-based DNA vaccines against B-cell lymphoma.

Immune response at birth, long-term immune memory and 2 years follow-up after in-utero anti-HBV DNA immunization

Infections occurring at the end of pregnancy, during birth or by breastfeeding are responsible for the high toll of death among first-week infants. In-utero DNA immunization has demonstrated the effectiveness in inducing specific immunity in newborns. A major contribution to infant immunization would be achieved if a vaccine proved able to be protective as early as at the birth, preventing the typical ‘first-week infections’. To establish its potential for use in humans, in-utero DNA vaccination efficiency has to be evaluated for short- and long-term safety, protection at delivery, efficacy of boosts in adults and effective window/s for modulation of immune response during pregnancy, in an animal model suitable with human development. Here we show that a single intramuscular in-utero anti-HBV DNA immunization at two-thirds of pig gestation produces, at birth, antibody titers considered protective in humans. The boost of antibody titers in every animal following recall at 4 and 10 months demonstrates the establishment of immune memory. The safety of in-utero fetus manipulation is guaranteed by short-term (no fetus loss, lack of local alterations, at-term spontaneous delivery, breastfeeding) and long-term (2 years) monitoring. Treatment of fetuses closer to delivery results in immune ignorance without induction of tolerance. This result highlights the repercussion of selecting the appropriate time point when this approach is used to deliver therapeutic genes. All these findings illustrate the relevance of naked DNA-based vaccination technology in therapeutic efforts aimed to prevent the high toll of death among first-week infants.

Role of the 5-HTTLPR and SNP Promoter Polymorphisms on Serotonin Transporter Gene Expression: a Closer Look at Genetic Architecture and In Vitro Functional Studies of Common and Uncommon Allelic Variants.

The serotonin (5-hydroxytriptamine (5-HT)) transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) is a variable number tandem repeats (VNTR) located in the promoter region of the human 5-HTT-encoding gene SLC6A4. This length polymorphism gives rise to different promoter variants, variously influencing SLC6A4 expression. Over the years, an extensive literature has investigated the relationships between these promoter variants and SLC6A4 gene expression, since these variants have been variously associated to complex neuropsychiatric conditions and traits. In this review, we detail the genetic architecture of the 5-HTTLPR allelic variants reported so far, with a closer look at the two single nucleotide polymorphisms (SNPs) rs25531 and rs25532 that lies in the VNTR and thus increase genetic variability of the SLC6A4 promoter. We summarize the hypothesized molecular mechanisms underlying this variation. We also provide an update on common and uncommon 5-HTTLPR allelic variants reviewing the available data on functional in vitro analysis of their regulatory effect on SLC6A4 gene transcription. Controversial findings are highlighted and critically discussed. A deeper knowledge of the “5-HTTLPR universe” will be useful to better understand the molecular basis of serotonin homeostasis and the pathological basis underlying serotonin-related neuropsychiatric conditions and traits.

Genetic Immunization with CDR3-Based Fusion Vaccine Confers Protection and Long-Term Tumor-Free Survival in a Mouse Model of Lymphoma

Therapeutic vaccination against idiotype is a promising strategy for immunotherapy of B-cell malignancies. We have previously shown that CDR3-based DNA immunization can induce immune response against lymphoma and explored this strategy to provide protection in a murine B-cell lymphoma model. Here we performed vaccination employing as immunogen a naked DNA fusion product. The DNA vaccine was generated following fusion of a sequence derived from tetanus toxin fragment C to the VHCDR3109−116 epitope. Induction of tumor-specific immunity as well as ability to inhibit growth of the aggressive 38C13 lymphoma and to prolong survival of vaccinated mice has been tested. We determined that DNA fusion vaccine induced immune response, elicited a strong protective antitumor immunity, and ensured almost complete long-term tumor-free survival of vaccinated mice. Our results show that CDR3-based DNA fusion vaccines hold promise for vaccination against lymphoma.

The Pathological Cross Talk Between Apolipoprotein E and Amyloid-β Peptide in Alzheimer's Disease: Emerging Gene-Based Therapeutic Approaches

Apolipoprotein E (ApoE) plays a key role in lipid transport in the plasma and in the central nervous system through its interaction with members of the low-density lipoprotein receptor family. The three common isoforms of ApoE (ApoE2, ApoE3, and ApoE4) differ in their ability to perform neuronal maintenance and repair functions and differentially affect the risk of developing neurodegenerative disorders. The ApoE4 isoform is a strong genetic risk factor for Alzheimers disease. Up-to-date knowledge about the structural and biophysical features of ApoE4 shed light on the molecular basis underlying the isoform-specific pathogenic role of ApoE4 and its contribution to AD pathology through several different mechanisms. ApoE4 impacts on amyloid-beta (Abeta) production, Abeta clearance, Abeta fibrillation, and tangle formation as well as on mitochondrial functions leading to neuronal toxicity and synaptic damage. This review summarizes the pathological cross talk between ApoE and Abeta peptide in Alzheimers disease. Lastly, we examine emerging gene-based therapeutic approaches encompassing the use of ApoE and their potential opportunities to preventing or treating Alzheimers disease.

In Vivo DNA Electrotransfer for Immunotherapy of Cancer and Neurodegenerative Diseases

Electroporation is the process commonly referred to the transient increase in the permeability of cell membranes on submission to electric field pulses. Electroporation has become an increasingly extensive method to enhance in vivo DNA delivery for both gene therapy applications as well as for delivery of DNA vaccines, mostly against cancer. In vivo gene electrotransfer is of special interest since it is the most efficient non-viral strategy for gene delivery and it is worthy of low manufacturing costs, ease of realization and favorable safety profile. No adverse findings observed in toxicology and biodistribution/integration studies have been warranted for the evaluation of this approach in humans. Therefore, gene delivery followed by electroporation is currently being investigated in several clinical trials. The positive outcomes of early studies suggest that the efficacy of gene delivery and immunogenicity has greatly improved by electroporation. This review briefly summarizes salient features and recent findings that have contributed to the rapid progress of electroimmunotherapy as well as an overview of advanced clinical studies in oncology. Translation of in vivo DNA electrovaccination for neurodegenerative diseases as well as future expectations are also discussed.

Looking Beyond the 5-HTTLPR Polymorphism: Genetic and Epigenetic Layers of Regulation Affecting the Serotonin Transporter Gene Expression

Serotonin (5-HT) is a neurotransmitter that regulates fundamental aspects of brain development, physiology and behaviour. The serotonin transporter (5-HTT) is deputized to the reuptake of 5-HT from the intersynaptic space in the presynaptic neurons. 5-HTT governs duration and magnitude of 5-HT biological actions, acting as a master regulator of the fine-tuning of 5-HT signalling. Genetic variation at SLC6A4 gene locus, encoding 5-HTT, contributes to alteration in 5-HT reuptake. The 5-HTTLPR/rs25531/rs25532 polymorphisms located in the promoter region of SLC6A4 gene have been associated with stress-related psychopathology and functional brain phenotypes. Besides, further DNA variations in functional regulative elements located at 5′ and 3′ termini of the SLC6A4 gene influence transcriptional and post-transcriptional steps. Recently, epigenetic processes including SLC6A4 promoter methylation and transcript silencing by microRNA were shown to be involved in the aetiology of affective disorders. Furthermore, gene-environment interactions such as early life stress often encompass epigenetic changes, which can stably mark the genome in response to environmental stimuli potentially altering gene expression across lifespan. Therefore, it seems well established that functional variations in the SLC6A4 gene expression can no longer be ascribed to the modulating 5-HTTLPR promoter polymorphism but need to be integrated with the contribution arising from other interactive elements and epigenetic mechanisms. In this review, we discuss genetic and epigenetic layers of regulation affecting SLC6A4 gene expression. An overview of human and cellular studies investigating the impact of these regulatory processes on SLC6A4 gene expression is provided.

Strategies for Improving DNA Vaccine Performance

The goal of active vaccination is to induce all the immune effector pathways and to establish immunological memory allowing prolonged surveillance against pathogens or cancer cells. DNA vaccination platform is an intriguing strategy owing to its ability to mobilize both branches of the immune system (i.e., innate immunity as well as adaptive immunity). Since plasmids offer several advantages for biotechnological applications due to their modular structure and easy manipulation, a wide range of strategies can be applied to improve DNA vaccine performance. This chapter discusses this topic in detail taking into account antigen/epitope selection and optimization, inclusion of intracellular targeting sequences and genetic adjuvants, and provision of T cell help.