Co-vaccination with adeno-associated virus vectors encoding human papillomavirus 16 L1 proteins and adenovirus encoding murine GM-CSF can elicit strong and prolonged neutralizing antibody

Genetic adjuvants: A paradigm shift in vaccine development and immune modulation

The COVID-19 pandemic underscored the urgency of developing effective vaccines to combat infectious diseases, especially in vulnerable populations such as the elderly and immunocompromised. While recombinant protein vaccines offer safety, their poor immunogenicity highlights the need for advanced vaccination platforms. New genetic/nucleic acid vaccine formulations like plasmid DNA and mRNA showed efficiency and safety in preclinical and clinical studies; however, they demand innovative adjuvants because their mechanism of action differs from traditional protein vaccines. Genetic adjuvants-encoded by nucleic acids within DNA, RNA, or viral vectors-emerge as a promising solution by targeting and modulating specific immune pathways, including antigen presentation, T cell activation, and memory formation. These innovative adjuvants enhance vaccine efficacy by fine-tuning innate and adaptive immune responses, overcoming immune senescence, and addressing the challenges of CD8+ T cell activation in immunocompromised populations. This review explores the potential of genetically encoded adjuvants, including cytokines, chemokines, and other immune modulators. By comparing these adjuvants to traditional formulations, we highlight their capacity to address the limitations of modern vaccines while discussing their integration with emerging technologies like RNA-based vaccines. As genetic adjuvants advance toward clinical application, understanding their mechanisms and optimizing their delivery is pivotal to unlocking next-generation immunization strategies.

Design of multi-epitope chimeric phage nanocarrier vaccines for porcine deltacoronavirus

Porcine delta coronavirus (PDCoV) poses a significant threat to the swine industry. Thus, the development of innovative vaccine candidates is critical for PDCoV prevention. This study details the creation of a PDCoV nanoparticle vaccine utilizing bacteriophage (phage) T4 as a delivery platform. B cell and T cell epitopes of the PDCoV spike (S) protein were identified through bioinformatics and assembled into a tandem construct (termed Pep) using a linker. In silico molecular docking revealed stable interactions between Pep and TLR3. Immune stimulation predictions indicated that Pep could trigger a robust immune response. The prokaryotic Pep protein was conjugated with T4 phage to generate the recombinant T4-Pep phage. Experimental data demonstrated that a single T4 phage displayed at least 830 copies of Pep. In a mouse immunoprotection assay, T4-Pep induced significantly higher levels of specific IgG antibodies and superior neutralizing antibody titers against PDCoV compared to the Pep naked peptide antigen. Moreover, T4 phage exhibited potent immunostimulatory effects, with immunized mice showing protection against PDCoV infection. Histological analysis revealed enhanced intestinal mucosal integrity post-immunization. These findings suggest that bacteriophages are promising vectors for the efficient delivery of viral epitopes, offering a potential platform for developing vaccines against porcine enteric coronaviruses.

Adeno-associated viral vectors deliver gene vaccines

Adeno-associated viruses (AAVs) are leading platforms for in vivo delivery of gene therapies, with six licensed AAV-based therapeutics attributed to their non-pathogenic nature, low immunogenicity, and high efficiency. In the realm of gene-based vaccines, one of the most vital therapeutic areas, AAVs are also emerging as promising delivery tools. We scrutinized AAVs, focusing on their virological properties, as well as bioengineering and chemical modifications to demonstrate their significant potential in gene vaccine delivery, and detailing the preparation of AAV particles. Additionally, we summarized the use of AAV vectors in vaccines for both infectious and non-infectious diseases, such as influenza, COVID-19, Alzheimer's disease, and cancer. Furthermore, this review, along with the latest clinical trial updates, provides a comprehensive overview of studies on the potential of using AAV vectors for gene vaccine delivery. It aims to deepen our understanding of the challenges and limitations in nucleic acid delivery and pave the way for future clinical success.

The use of viral vectors in vaccine development

Vaccines represent the single most cost-efficient and equitable way to combat and eradicate infectious diseases. While traditional licensed vaccines consist of either inactivated/attenuated versions of the entire pathogen or subunits of it, most novel experimental vaccines against emerging infectious diseases employ nucleic acids to produce the antigen of interest directly in vivo. These include DNA plasmid vaccines, mRNA vaccines, and recombinant viral vectors. The advantages of using nucleic acid vaccines include their ability to induce durable immune responses, high vaccine stability, and ease of large-scale manufacturing. In this review, we present an overview of pre-clinical and clinical data on recombinant viral vector vaccines and discuss the advantages and limitations of the different viral vector platforms.

Sargramostim and immune checkpoint inhibitors: combinatorial therapeutic studies in metastatic melanoma

The use of immune checkpoint inhibitors in patients with metastatic melanoma generates clinical benefit, including improved survival. Yet disease resistance and immune-related adverse events persist as unmet needs. Sargramostim, a yeast-derived recombinant human GM-CSF, has shown clinical activity against diverse solid tumors, including metastatic melanoma. Here we review the use of sargramostim for treatment of advanced melanoma. Potential sargramostim applications in melanoma draw on the unique ability of GM-CSF to link innate and adaptive immune responses. We review preclinical and translational data describing the mechanism of action of sargramostim and synergy with immune checkpoint inhibitors to enhance efficacy and reduce treatment-related toxicity.

Local Sustained GM-CSF Delivery by Genetically Engineered Encapsulated Cells Enhanced Both Cellular and Humoral SARS-CoV-2 Spike-Specific Immune Response in an Experimental Murine Spike DNA Vaccination Model

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide pandemic with recurrences. Therefore, finding a vaccine for this virus became a priority for the scientific community. The SARS-CoV-2 spike protein has been described as the keystone for viral entry into cells and effective immune protection against SARS-CoV-2 is elicited by this protein. Consequently, many commercialized vaccines focus on the spike protein and require the use of an optimal adjuvant during vaccination. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has demonstrated a powerful enhancement of acquired immunity against many pathogens when delivered in a sustained and local manner. In this context, we developed an encapsulated cell-based technology consisting of a biocompatible, semipermeable capsule for secretion of GM-CSF. In this study, we investigated whether murine GM-CSF (muGM-CSF) represents a suitable adjuvant for SARS-CoV-2 immunization, and which delivery strategy for muGM-CSF could be most beneficial. To test this, different groups of mice were immunized with intra-dermal (i.d.) electroporated spike DNA in the absence or presence of recombinant or secreted muGM-CSF. Results demonstrated that adjuvanting a spike DNA vaccine with secreted muGM-CSF resulted in enhancement of specific cellular and humoral immune responses against SARS-CoV-2. Our data also highlighted the importance of delivery strategies to the induction of cellular and humoral-mediated responses.

Brucella abortus RB51 lipopolysaccharide influence as an adjuvant on the therapeutic efficacy of HPV16 L1 and HPV16 E7 DNA vaccines

OBJECTIVES

Human papillomavirus (HPV) is a primary contributing agent of cervical cancer. Eradication of HPV-related infections requires therapeutic strategies. We used Brucella abortus RB51 rough lipopolysaccharide (R-LPS) as an adjuvant along with two HPV16 therapeutic DNA vaccines, pcDNA3-E7 and pcDNA3-L1, for improving DNA vaccine efficacy.

MATERIALS AND METHODS

For evaluation of the B. abortus LPS adjuvant efficacy in combination with DNA vaccines to induce cellular immune responses, C57BL/6 mice were immunized with the DNA vaccines, with or without R-LPS adjuvant. IFN-γ and IL-4 cytokines assay was carried out for assessment of cellular and humoral immune responses.

RESULTS

Findings indicated that vaccination with pcDNA3-E7 or pcDNA3-L1 alone could induce strong cellular immune responses, but stronger antigen-specific T-cell immune responses were shown by co-administration of HPV16 E7 and HPV16 L1 DNA vaccines along with R-LPS adjuvant.

CONCLUSION

Overall, B. abortus R-LPS through enhancement of T-cell immune responses can be considered an efficient vaccine adjuvant in future studies and trials.

Adeno-associated viral vector-mediated immune responses: Understanding barriers to gene delivery

Adeno-associated viral (AAV) vectors have emerged as the leading gene delivery platform for gene therapy and vaccination. Three AAV-based gene therapy drugs, Glybera, LUXTURNA, and ZOLGENSMA were approved between 2012 and 2019 by the European Medicines Agency and the United States Food and Drug Administration as treatments for genetic diseases hereditary lipoprotein lipase deficiency (LPLD), inherited retinal disease (IRD), and spinal muscular atrophy (SMA), respectively. Despite these therapeutic successes, clinical trials have demonstrated that host anti-viral immune responses can prevent the long-term gene expression of AAV vector-encoded genes. Therefore, it is critical that we understand the complex relationship between AAV vectors and the host immune response. This knowledge could allow for the rational design of optimized gene transfer vectors capable of either subverting host immune responses in the context of gene therapy applications, or stimulating desirable immune responses that generate protective immunity in vaccine applications to AAV vector-encoded antigens. This review provides an overview of our current understanding of the AAV-induced immune response and discusses potential strategies by which these responses can be manipulated to improve AAV vector-mediated gene transfer.

The Journey of in vivo Virus Engineered Dendritic Cells From Bench to Bedside: A Bumpy Road

Dendritic cells (DCs) are recognized as highly potent antigen-presenting cells that are able to stimulate cytotoxic T lymphocyte (CTL) responses with antitumor activity. Consequently, DCs have been explored as cellular vaccines in cancer immunotherapy. To that end, DCs are modified with tumor antigens to enable presentation of antigen-derived peptides to CTLs. In this review we discuss the use of viral vectors for in situ modification of DCs, focusing on their clinical applications as anticancer vaccines. Among the viral vectors discussed are those derived from viruses belonging to the families of the Poxviridae, Adenoviridae, Retroviridae, Togaviridae, Paramyxoviridae, and Rhabdoviridae. We will further shed light on how the combination of viral vector-based vaccination with T-cell supporting strategies will bring this strategy to the next level.

Adeno-associated virus (AAV) vectors in cancer gene therapy

Gene delivery vectors based on adeno-associated virus (AAV) have been utilized in a large number of gene therapy clinical trials, which have demonstrated their strong safety profile and increasingly their therapeutic efficacy for treating monogenic diseases. For cancer applications, AAV vectors have been harnessed for delivery of an extensive repertoire of transgenes to preclinical models and, more recently, clinical trials involving certain cancers. This review describes the applications of AAV vectors to cancer models and presents developments in vector engineering and payload design aimed at tailoring AAV vectors for transduction and treatment of cancer cells. We also discuss the current status of AAV clinical development in oncology and future directions for AAV in this field.

AAV Vectors Vaccines Against Infectious Diseases

Since their discovery as a tool for gene transfer, vectors derived from the adeno-associated virus (AAV) have been used for gene therapy applications and attracted scientist to this field for their exceptional properties of efficiency of in vivo gene transfer and the level and duration of transgene expression. For many years, AAVs have been considered as low immunogenic vectors due to their ability to induce long-term expression of non-self-proteins in contrast to what has been observed with other viral vectors, such as adenovirus, for which strong immune responses against the same transgene products were documented. The perceived low immunogenicity likely explains why the use of AAV vectors for vaccination was not seriously considered before the early 2000s. Indeed, while analyses conducted using a variety of transgenes and animal species slowly changed the vision of immunological properties of AAVs, an increasing number of studies were also performed in the field of vaccination. Even if the comparison with other modes of vaccination was not systemically performed, the analyses conducted so far in the field of active immunotherapy strongly suggest that AAVs possess some interesting features to be used as tools to produce an efficient and sustained antibody response. In addition, recent studies also highlighted the potential of AAVs for passive immunotherapy. This review summarizes the main studies conducted to evaluate the potential of AAV vectors for vaccination against infectious agents and discusses their advantages and drawbacks. Altogether, the variety of studies conducted in this field contributes to the understanding of the immunological properties of this versatile virus and to the definition of its possible future applications.

Protection against henipavirus infection by use of recombinant adeno-associated virus-vector vaccines

Nipah virus (NiV) and Hendra virus (HeV) are closely related, recently emerged paramyxoviruses that are capable of causing considerable morbidity and mortality in several mammalian species, including humans. Henipavirus-specific vaccines are still commercially unavailable, and development of novel antiviral strategies to prevent lethal infections due to henipaviruses is highly desirable. Here we describe the development of adeno-associated virus (AAV) vaccines expressing the NiV G protein. Characterization of these vaccines in mice demonstrated that a single intramuscular AAV injection was sufficient to induce a potent and long-lasting antibody response. Translational studies in hamsters further demonstrated that all vaccinated animals were protected against lethal challenge with NiV. In addition, this vaccine induced a cross-protective immune response that was able to protect 50% of the animals against a challenge by HeV. This study presents a new efficient vaccination strategy against henipaviruses and opens novel perspectives on the use of AAV vectors as vaccines against emergent diseases.

New approaches to prophylactic human papillomavirus vaccines for cervical cancer prevention

The currently licensed human papillomavirus (HPV) vaccines are safe and highly effective at preventing HPV infection for a select number of papillomavirus types, thus decreasing the incidence of precursors to cervical cancer. It is expected that vaccination will also ultimately reduce the incidence of this cancer. The licensed HPV vaccines are, however, type restricted and expensive, and also require refrigeration, multiple doses and intramuscular injection. Second-generation vaccines are currently being developed to address these shortcomings. New expression systems, viral and bacterial vectors for HPV L1 capsid protein delivery, and use of the HPV L2 capsid protein will hopefully aid in decreasing cost and increasing ease of use and breadth of protection. These second-generation vaccines could also allow affordable immunization of women in developing countries, where the incidence of cervical cancer is high.

A new genetic vaccine platform based on an adeno-associated virus isolated from a rhesus macaque

We created a hybrid adeno-associated virus (AAV) from two related rhesus macaque isolates, called AAVrh32.33, and evaluated it as a vaccine carrier for human immunodeficiency virus type 1 (HIV-1) and type A influenza virus antigens. The goal was to overcome the limitations of vaccines based on other AAVs, which generate dysfunctional T-cell responses and are inhibited by antibodies found in human sera. Injection of a Gag-expressing AAVrh32.33 vector into mice resulted in a high-quality CD8(+) T-cell response. The resulting Gag-specific T cells express multiple cytokines at high levels, including interleukin-2, with many having memory phenotypes; a subsequent boost with an adenovirus vector yielded a brisk expansion of Gag-specific T cells. A priming dose of AAVrh32.33 led to high levels of Gag antibodies, which exceed levels found after injection of adenovirus vectors. Importantly, passive transfer of pooled human immunoglobulin into mice does not interfere with the efficacy of AAVrh32.33 expressing nucleoproteins from influenza virus, as measured by protection to a lethal dose of influenza virus, which is consistent with the very low seroprevalence to this virus in humans. Studies of macaques with vectors expressing gp140 from HIV-1 (i.e., with AAVrh32.33 as the prime and simian adenovirus type 24 as the boost) demonstrated results similar to those for mice with high-level and high-quality CD8(+) T-cell responses to gp140 and high-titered neutralizing antibodies to homologous HIV-1. The biology of this novel AAV hybrid suggests that it should be a preferred genetic vaccine carrier, capable of generating robust T- and B-cell responses.

HPV Vaccines: today and in the Future

Human papillomavirus (HPV) is responsible for 99.7% of cervical cancer cases and an estimated 5% of all cancers worldwide. The largest burden from HPV-associated cervical cancers is in developing nations where effective cervical cancer screening programs are nonexistent. Even in developed nations, diagnosis and treatment of cervical precancers continue to be large economic burdens. Prophylactic vaccination against HPV is an ideal method for the prevention of cervical cancer and other HPV associated diseases. Safe and effective virus-like-particle-derived prophylactic vaccines are available to most nations. The high cost of the current vaccines makes it out of reach for most developing nations. Because millions of women are already infected with HPV and have serious disease, therapeutic HPV vaccines are being developed to treat these women. This article presents the natural history, oncogenesis, and host immune interactions of HPV and associated diseases. The article also discusses the safety and efficacy of commercially available prophylactic vaccines against HPV, as well as novel prophylactic and therapeutic vaccine delivery strategies in early clinical development.

Prophylactic DNA immunization against multiple papillomavirus types

At least 15 different papillomavirus types are causatively associated with the development of tumors in humans. Since the middle of 2006 a protective, virus-like particle based vaccine against the tumor-related HPV types 16 and 18 is commercially available. We investigated the possibility of applying DNA vaccination to obtain protective antibody responses against multiple papillomavirus types. Our data indicate that low amounts of DNA were sufficient to induce neutralizing antibodies in mice although a DNA dose-dependency in respect to the L1-specific antibody titers was observed. Furthermore, we found that immune responses against different PV types could be induced by simultaneous DNA vaccination with a mixture of expression vectors encoding L1 proteins of different papillomavirus types. However, we observed that there was a strong interference when plasmids encoding different L1 genes were used together. HPV 16 responses were repressed by co-administration of HPV 11 and/or BPV 1 L1 expression constructs. Likewise, BPV 1 responses were repressed by co-administration of HPV 16 or HPV 11 L1 plasmids. This interference could be overcome by administration of the different constructs into different sites of the animals or by sequential immunization. Thus, our results suggest that the mode of repression was due to interference with L1 particle assembly and was not a consequence of immunodominance of certain L1 proteins.

Induction of robust immune responses against human immunodeficiency virus is supported by the inherent tropism of adeno-associated virus type 5 for dendritic cells

The ability of adeno-associated virus serotype 1 to 8 (AAV1 to AAV8) vectors expressing the human immunodeficiency virus type 1 (HIV-1) Env gp160 (AAV-HIV) to induce an immune response was evaluated in BALB/c mice. The AAV5 vector showed a higher tropism for both mouse and human dendritic cells (DCs) than did the AAV2 vector, whereas other AAV serotype vectors transduced DCs only poorly. AAV1, AAV5, AAV7, and AAV8 were more highly expressed in muscle cells than AAV2. An immunogenicity study of AAV serotypes indicates that AAV1, AAV5, AAV7, and AAV8 vectors expressing the Env gp160 gene induced higher HIV-specific humoral and cell-mediated immune responses than the AAV2 vector did, with the AAV5 vector producing the best responses. Furthermore, mice injected with DCs that had been transduced ex vivo with an AAV5 vector expressing the gp160 gene elicited higher HIV-specific cell-mediated immune responses than did DCs transduced with AAV1 and AAV2 vectors. We also found that AAV vectors produced by HEK293 cells and insect cells elicit similar levels of antigen-specific immune responses. These results demonstrate that the immunogenicity of AAV vectors depends on their tropism for both antigen-presenting cells (such as DCs) and non-antigen-presenting cells (such as muscular cells) and that AAV5 is a better vector than other AAV serotypes. These results may aid in the development of AAV-based vaccine and gene therapy.

Chapter 17: Second generation HPV vaccines to prevent cervical cancer

Prophylactic human papillomavirus (HPV) vaccines based on intramuscular injection of non-infectious L1 virus-like particles (VLPs) are undergoing intense clinical evaluation. As documented in preceding chapters of this monograph, clinical trials of these vaccines have demonstrated their safety and high efficacy at preventing type-specific persistent cervical HPV infection and the development of type-specific cervical intraepithelial neoplasia (CIN) cervical neoplasia. There is widespread optimism that VLP vaccines will become commercially available within the next few years. The prospects for development of alternative HPV vaccines must be considered in light of the likelihood that a safe and effective prophylactic HPV vaccine will soon be available. Three questions need to be addressed: (1) Is there sufficient need for a second generation vaccine? (2) Are there sufficiently attractive candidates for clinical trials? (3) Is there a realistic development/commercialization path?

Vaccine strategies for human papillomavirus-associated cancers

PURPOSE OF REVIEW

To review novel immunologic strategies for the prevention and treatment of human papillomavirus infection and associated diseases. Both animal model systems and human protocols are discussed.

RECENT FINDINGS

Many vaccine platforms for both prevention of human papillomavirus infection and treatment of associated disease have been developed. Virus-like particle constructs containing human papillomavirus capsid proteins have been shown to protect against human papillomavirus infection. Novel peptide or protein constructs containing modified E6 or E7 proteins, novel adjuvants, fusion proteins such as immunoglobulin-G-heavy chain E7, or heat shock proteins have been made as therapeutic modalities. In addition, many new recombinant vaccine vectors such as vaccinia, Listeria species, adenovirus, Semliki Forest vectors, and others have been developed as carriers of immunotherapeutic agents. Recently, chimeric virus-like particle vaccines have been developed to treat existing human papillomavirus-induced neoplasms.

SUMMARY

Immunotherapy protocols using a variety of recombinant vectors and modified human papillomavirus proteins induce in-vitro T cell responses and may lead to tumor regression. Vaccine-induced in-vitro immune reactivity and clinical vaccine effects are often not well associated. Further analysis of ongoing human immunotherapy trials is awaited.

Intranasal vaccination with recombinant adeno-associated virus type 5 against human papillomavirus type 16 L1

Adeno-associated viruses (AAV) have been developed and evaluated as recombinant vectors for gene therapy in many preclinical studies, as well as in clinical trials. However, only a few approaches have used recombinant AAV (rAAV) to deliver vaccine antigens. We generated an rAAV encoding the major capsid protein L1 (L1h) from the human papillomavirus type 16 (HPV16), aiming to develop a prophylactic vaccine against HPV16 infections, which are the major cause of cervical cancer in women worldwide. A single dose of rAAV5 L1h administered intranasally was sufficient to induce high titers of L1-specific serum antibodies, as well as mucosal antibodies in vaginal washes. Seroconversion was maintained for at least 1 year. In addition, a cellular immune response was still detectable 60 weeks after immunization. Furthermore, lyophilized rAAV5 L1h successfully evoked a systemic and mucosal immune response in mice. These data clearly show the efficacy of a single-dose intranasal immunization against HPV16 based on the recombinant rAAV5L1h vector without the need of an adjuvant.

SLPI and elafin: one glove, many fingers

Elafin and SLPI (secretory leucocyte protease inhibitor) have multiple important roles both in normal homoeostasis and at sites of inflammation. These include antiprotease and antimicrobial activity as well as modulation of the response to LPS (lipopolysaccharide) stimulation. Elafin and SLPI are members of larger families of proteins secreted predominantly at mucosal sites, and have been shown to be modulated in multiple pathological conditions. We believe that elafin and SLPI are important molecules in the controlled functioning of the innate immune system, and may have further importance in the integration of this system with the adaptive immune response. Recent interest has focused on the influence of inflamed tissues on the recruitment and phenotypic modulation of cells of the adaptive immune system and, indeed, the local production of elafin and SLPI indicate that they are ideally placed in this regard. Functionally related proteins, such as the defensins and cathelicidins, have been shown to have direct effects upon dendritic cells with potential alteration of their phenotype towards type I or II immune responses. This review addresses the multiple functions of elafin and SLPI in the inflammatory response and discusses further their roles in the development of the adaptive immune response.