Improved Durability to SARS-CoV-2 Vaccine Immunity following Coimmunization with Molecular Adjuvant Adenosine Deaminase-1.

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have demonstrated strong immunogenicity and protection against severe disease, concerns about the duration and breadth of these responses remain. In this study, we show that codelivery of plasmid-encoded adenosine deaminase-1 (pADA) with SARS-CoV-2 spike glycoprotein DNA enhances immune memory and durability in vivo. Coimmunized mice displayed increased spike-specific IgG of higher affinity and neutralizing capacity as compared with plasmid-encoded spike-only-immunized animals. Importantly, pADA significantly improved the longevity of these enhanced responses in vivo. This coincided with durable increases in frequencies of plasmablasts, receptor-binding domain-specific memory B cells, and SARS-CoV-2-specific T follicular helper cells. Increased spike-specific T cell polyfunctionality was also observed. Notably, animals coimmunized with pADA had significantly reduced viral loads compared with their nonadjuvanted counterparts in a SARS-CoV-2 infection model. These data suggest that pADA enhances immune memory and durability and supports further translational studies.

Strategic Variants of CSP Delivered as SynDNA Vaccines Demonstrate Heterogeneity of Immunogenicity and Protection from Plasmodium Infection in a Murine Model.

Malaria infects millions of people every year, and despite recent advances in controlling disease spread, such as vaccination, it remains a global health concern. The circumsporozoite protein (CSP) has long been acknowledged as a key target in antimalarial immunity. Leveraging the DNA vaccine platform against this formidable pathogen, the following five synthetic DNA vaccines encoding variations of CSP were designed and studied: 3D7, GPI1, ΔGPI, TM, and DD2. Among the single CSP antigen constructs, a range of immunogenicity was observed with ΔGPI generating the most robust immunity. In an intravenous (i.v.) sporozoite challenge, the best protection among vaccinated mice was achieved by ΔGPI, which performed almost as well as the monoclonal antibody 311 (MAb 311) antibody control. Further analyses revealed that ΔGPI develops high-molecular-weight multimers in addition to monomeric CSP. We then compared the immunity generated by ΔGPI versus synDNA mimics for the antimalaria vaccines RTS,S and R21. The anti-CSP antibody responses induced were similar among these three immunogens. T cell responses demonstrated that ΔGPI induced a more focused anti-CSP response. In an infectious mosquito challenge, all three of these constructs generated inhibition of liver-stage infection as well as immunity from blood-stage parasitemia. This study demonstrates that synDNA mimics of complex malaria immunogens can provide substantial protection as can a novel synDNA vaccine ΔGPI.

Gene-encoded nanoparticle vaccine platforms for in vivo assembly of multimeric antigen to promote adaptive immunity.

Nanoparticle vaccines are a diverse category of vaccines for the prophylaxis or treatment of various diseases. Several strategies have been employed for their optimization, especially to enhance vaccine immunogenicity and generate potent B-cell responses. Two major modalities utilized for particulate antigen vaccines include using nanoscale structures for antigen delivery and nanoparticles that are themselves vaccines due to antigen display or scaffolding-the latter of which we will define as "nanovaccines." Multimeric antigen display has a variety of immunological benefits compared to monomeric vaccines mediated through potentiating antigen-presenting cell presentation and enhancing antigen-specific B-cell responses through B-cell activation. The majority of nanovaccine assembly is done in vitro using cell lines. However, in vivo assembly of scaffolded vaccines potentiated using nucleic acids or viral vectors is a burgeoning modality of nanovaccine delivery. Several advantages to in vivo assembly exist, including lower costs of production, fewer production barriers, as well as more rapid development of novel vaccine candidates for emerging diseases such as SARS-CoV-2. This review will characterize the methods for de novo assembly of nanovaccines in the host using methods of gene delivery including nucleic acid and viral vectored vaccines. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Engineered antibody cytokine chimera synergizes with DNA-launched nanoparticle vaccines to potentiate melanoma suppression in vivo.

Cancer immunotherapy has demonstrated great promise with several checkpoint inhibitors being approved as the first-line therapy for some types of cancer, and new engineered cytokines such as Neo2/15 now being evaluated in many studies. In this work, we designed antibody-cytokine chimera (ACC) scaffolding cytokine mimetics on a full-length tumor-specific antibody. We characterized the pharmacokinetic (PK) and pharmacodynamic (PD) properties of first-generation ACC TA99-Neo2/15, which synergized with DLnano-vaccines to suppress in vivo melanoma proliferation and induced significant systemic cytokine activation. A novel second-generation ACC TA99-HL2-KOA1, with retained IL-2Rß/γ binding and attenuated but preserved IL-2Rα binding, induced lower systemic cytokine activation with non-inferior protection in murine tumor studies. Transcriptomic analyses demonstrated an upregulation of Type I interferon responsive genes, particularly ISG15, in dendritic cells, macrophages and monocytes following TA99-HL2-KOA1 treatment. Characterization of additional ACCs in combination with cancer vaccines will likely be an important area of research for treating melanoma and other types of cancer.

Adenosine deaminase augments SARS-CoV-2 specific cellular and humoral responses in aged mouse models of immunization and challenge.

Despite numerous clinically available vaccines and therapeutics, aged patients remain at increased risk for COVID-19 morbidity. Furthermore, various patient populations, including the aged can have suboptimal responses to SARS-CoV-2 vaccine antigens. Here, we characterized vaccine-induced responses to SARS-CoV-2 synthetic DNA vaccine antigens in aged mice. Aged mice exhibited altered cellular responses, including decreased IFNγ secretion and increased TNFα and IL-4 secretion suggestive of TH2-skewed responses. Aged mice exhibited decreased total binding and neutralizing antibodies in their serum but significantly increased TH2-type antigen-specific IgG1 antibody compared to their young counterparts. Strategies to enhance vaccine-induced immune responses are important, especially in aged patient populations. We observed that co-immunization with plasmid-encoded adenosine deaminase (pADA)enhanced immune responses in young animals. Ageing is associated with decreases in ADA function and expression. Here, we report that co-immunization with pADA enhanced IFNγ secretion while decreasing TNFα and IL-4 secretion. pADA expanded the breadth and affinity SARS-CoV-2 spike-specific antibodies while supporting TH1-type humoral responses in aged mice. scRNAseq analysis of aged lymph nodes revealed that pADA co-immunization supported a TH1 gene profile and decreased FoxP3 gene expression. Upon challenge, pADA co-immunization decreased viral loads in aged mice. These data support the use of mice as a model for age-associated decreased vaccine immunogenicity and infection-mediated morbidity and mortality in the context of SARS-CoV-2 vaccines and provide support for the use of adenosine deaminase as a molecular adjuvant in immune-challenged populations.

Engineered DNA-encoded monoclonal antibodies targeting Plasmodium falciparum circumsporozoite protein confer single dose protection in a murine malaria challenge model.

Novel approaches for malaria prophylaxis remain important. Synthetic DNA-encoded monoclonal antibodies (DMAbs) are a promising approach to generate rapid, direct in vivo host-generated mAbs with potential benefits in production simplicity and distribution coupled with genetic engineering. Here, we explore this approach in a malaria challenge model. We engineered germline-reverted DMAbs based on human mAb clones CIS43, 317, and L9 which target a junctional epitope, major repeat, and minor repeat of the Plasmodium falciparum circumsporozoite protein (CSP) respectively. DMAb variants were encoded into a plasmid vector backbone and their expression and binding profiles were characterized. We demonstrate long-term serological expression of DMAb constructs resulting in in vivo efficacy of CIS43 GL and 317 GL in a rigorous mosquito bite mouse challenge model. Additionally, we engineered an Fc modified variant of CIS43 and L9-based DMAbs to ablate binding to C1q to test the impact of complement-dependent Fc function on challenge outcomes. Complement knockout variant DMAbs demonstrated similar protection to that of WT Fc DMAbs supporting the notion that direct binding to the parasite is sufficient for the protection observed. Further investigation of DMAbs for malaria prophylaxis appears of importance.

In vivo DNA-launched bispecific T cell engager targeting IL-13Rα2 controls tumor growth in an animal model of glioblastoma multiforme.

Glioblastoma is an aggressive tumor with poor survival rates. Bispecific T cell engagers (BTEs) against different cancers are in various stages of clinical development. Toxicity resulting from cytokine release syndrome and the short half-life of BTEs, which necessitates continuous infusion, complicating delivery and increasing costs, are major challenges in the field. Here we describe the development of in vivo DNA-launched BTEs (dBTEs) with highly focused targeting of interleukin-13 receptor α2 (IL-13Rα2), a glioblastoma cell-surface target. We developed 4 BTEs targeting 2 epitopes of IL-13Rα2 and studied how heavy-light chain orientation affects BTE function. The dBTEs induced T cell activation, cytokine production, and tumor cytolysis in the presence of IL-13Rα2+ tumor cells, but we observed unique patterns of immune activation. We found a strong correlation between granzyme B secretion and dBTE-induced cytolysis of specific and nonspecific tumors. We down-selected dBTE PB01-forward based on lower cytokine induction profile and highest activation specificity. In vivo, dBTE PB01-forward demonstrated an improved half-life versus intravenous recombinant BTE delivery. In an orthotopic glioblastoma model, dBTE PB01-forward controlled tumor growth, improving animal survival, supporting the hypothesis that the blood-brain barrier does not affect the function of systemically delivered dBTE. Further study of PB01-forward for targeting glioblastoma and other IL-13Rα2+ cancers is warranted.

Mucosal chemokine adjuvant enhances synDNA vaccine-mediated responses to SARS-CoV-2 and provides heterologous protection in vivo.

The global coronavirus disease 2019 (COVID-19) pandemic has claimed more than 5 million lives. Emerging variants of concern (VOCs) continually challenge viral control. Directing vaccine-induced humoral and cell-mediated responses to mucosal surfaces may enhance vaccine efficacy. Here we investigate the immunogenicity and protective efficacy of optimized synthetic DNA plasmids encoding wild-type severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (pS) co-formulated with the plasmid-encoded mucosal chemokine cutaneous T cell-attracting chemokine (pCTACK; CCL27). pCTACK-co-immunized animals exhibit increased spike-specific antibodies at the mucosal surface and increased frequencies of interferon gamma (IFNγ)+ CD8+ T cells in the respiratory mucosa. pCTACK co-immunization confers 100% protection from heterologous Delta VOC challenge. This study shows that mucosal chemokine adjuvants can direct vaccine-induced responses to specific immunological sites and have significant effects on heterologous challenge. Further study of this unique chemokine-adjuvanted vaccine approach in the context of SARS-CoV-2 vaccines is likely important.

Induction of tier-2 neutralizing antibodies in mice with a DNA-encoded HIV envelope native like trimer.

HIV Envelope (Env) is the main vaccine target for induction of neutralizing antibodies. Stabilizing Env into native-like trimer (NLT) conformations is required for recombinant protein immunogens to induce autologous neutralizing antibodies(nAbs) against difficult to neutralize HIV strains (tier-2) in rabbits and non-human primates. Immunizations of mice with NLTs have generally failed to induce tier-2 nAbs. Here, we show that DNA-encoded NLTs fold properly in vivo and induce autologous tier-2 nAbs in mice. DNA-encoded NLTs also uniquely induce both CD4 + and CD8 + T-cell responses as compared to corresponding protein immunizations. Murine neutralizing antibodies are identified with an advanced sequencing technology. The structure of an Env-Ab (C05) complex, as determined by cryo-EM, identifies a previously undescribed neutralizing Env C3/V5 epitope. Beyond potential functional immunity gains, DNA vaccines permit in vivo folding of structured antigens and provide significant cost and speed advantages for enabling rapid evaluation of new HIV vaccines.

Nucleic acid delivery of immune-focused SARS-CoV-2 nanoparticles drives rapid and potent immunogenicity capable of single-dose protection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines may target epitopes that reduce durability or increase the potential for escape from vaccine-induced immunity. Using synthetic vaccinology, we have developed rationally immune-focused SARS-CoV-2 Spike-based vaccines. Glycans can be employed to alter antibody responses to infection and vaccines. Utilizing computational modeling and in vitro screening, we have incorporated glycans into the receptor-binding domain (RBD) and assessed antigenic profiles. We demonstrate that glycan-coated RBD immunogens elicit stronger neutralizing antibodies and have engineered seven multivalent configurations. Advanced DNA delivery of engineered nanoparticle vaccines rapidly elicits potent neutralizing antibodies in guinea pigs, hamsters, and multiple mouse models, including human ACE2 and human antibody repertoire transgenics. RBD nanoparticles induce high levels of cross-neutralizing antibodies against variants of concern with durable titers beyond 6 months. Single, low-dose immunization protects against a lethal SARS-CoV-2 challenge. Single-dose coronavirus vaccines via DNA-launched nanoparticles provide a platform for rapid clinical translation of potent and durable coronavirus vaccines.

DNA-delivered antibody cocktail exhibits improved pharmacokinetics and confers prophylactic protection against SARS-CoV-2.

Monoclonal antibody therapy has played an important role against SARS-CoV-2. Strategies to deliver functional, antibody-based therapeutics with improved in vivo durability are needed to supplement current efforts and reach underserved populations. Here, we compare recombinant mAbs COV2-2196 and COV2-2130, which compromise clinical cocktail Tixagevimab/Cilgavimab, with optimized nucleic acid-launched forms. Functional profiling of in vivo-expressed, DNA-encoded monoclonal antibodies (DMAbs) demonstrated similar specificity, broad antiviral potency and equivalent protective efficacy in multiple animal challenge models of SARS-CoV-2 prophylaxis compared to protein delivery. In PK studies, DNA-delivery drove significant serum antibody titers that were better maintained compared to protein administration. Furthermore, cryo-EM studies performed on serum-derived DMAbs provide the first high-resolution visualization of in vivo-launched antibodies, revealing new interactions that may promote cooperative binding to trimeric antigen and broad activity against VoC including Omicron lineages. These data support the further study of DMAb technology in the development and delivery of valuable biologics.

Uropathogenic Escherichia coli Infection Compromises the Blood-Testis Barrier by Disturbing mTORC1-mTORC2 Balance.

The structural and functional destruction of the blood-testis barrier (BTB) following uropathogenic E. coli (UPEC) infection may be a critical component of the pathologic progress of orchitis. Recent findings indicate that the mammalian target of the rapamycin (mTOR)-signaling pathway is implicated in the regulation of BTB assembly and restructuring. To explore the mechanisms underlying BTB damage induced by UPEC infection, we analyzed BTB integrity and the involvement of the mTOR-signaling pathway using in vivo and in vitro UPEC-infection models. We initially confirmed that soluble virulent factors secreted from UPEC trigger a stress response in Sertoli cells and disturb adjacent cell junctions via down-regulation of junctional proteins, including occludin, zonula occludens-1 (ZO-1), F-actin, connexin-43 (CX-43), ß-catenin, and N-cadherin. The BTB was ultimately disrupted in UPEC-infected rat testes, and blood samples from UPEC-induced orchitis in these animals were positive for anti-sperm antibodies. Furthermore, we herein also demonstrated that mTOR complex 1 (mTORC1) over-activation and mTORC2 suppression contributed to the disturbance in the balance between BTB "opening" and "closing." More importantly, rapamycin (a specific mTORC1 inhibitor) significantly restored the expression of cell-junction proteins and exerted a protective effect on the BTB during UPEC infection. We further confirmed that short-term treatment with rapamycin did not aggravate spermatogenic degeneration in infected rats. Collectively, this study showed an association between abnormal activation of the mTOR-signaling pathway and BTB impairment during UPEC-induced orchitis, which may provide new insights into a potential treatment strategy for testicular infection.

A novel mouse AAV6 hACE2 transduction model of wild-type SARS-CoV-2 infection studied using synDNA immunogens.

More than 100 million people have been infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Common laboratory mice are not susceptible to wild-type SARS-CoV-2 infection, challenging the development and testing of effective interventions. Here, we describe the development and testing of a mouse model for SARS-CoV-2 infection based on transduction of the respiratory tract of laboratory mice with an adeno-associated virus vector (AAV6) expressing human ACE-2 (AAV6.2FF-hACE2). We validated this model using a previously described synthetic DNA vaccine plasmid, INO-4800 (pS). Intranasal instillation of AAV6.2FF-hACE2 resulted in robust hACE2 expression in the respiratory tract. pS induced robust cellular and humoral responses. Vaccinated animals were challenged with 105 TCID50 SARS-CoV-2 (hCoV-19/Canada/ON-VIDO-01/2020) and euthanized four days post-challenge to assess viral load. One immunization resulted in 50% protection and two immunizations were completely protective. Overall, the AAV6.2FF-hACE2 mouse transduction model represents an easily accessible, genetically diverse mouse model for wild-type SARS-CoV-2 infection and preclinical evaluation of potential interventions.

Intradermal-delivered DNA vaccine induces durable immunity mediating a reduction in viral load in a rhesus macaque SARS-CoV-2 challenge model.

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, has had a dramatic global impact on public health and social and economic infrastructures. Here, we assess the immunogenicity and anamnestic protective efficacy in rhesus macaques of an intradermal (i.d.)-delivered SARS-CoV-2 spike DNA vaccine, INO-4800, currently being evaluated in clinical trials. Vaccination with INO-4800 induced T cell responses and induced spike antigen and RBD binding antibodies with ADCP and ADCD activity. Sera from the animals neutralized both the D614 and G614 SARS-CoV-2 pseudotype viruses. Several months after vaccination, animals were challenged with SARS-CoV-2 resulting in rapid recall of anti-SARS-CoV-2 spike protein T cell and neutralizing antibody responses. These responses were associated with lower viral loads in the lung. These studies support the immune impact of INO-4800 for inducing both humoral and cellular arms of the adaptive immune system, which are likely important for providing durable protection against COVID-19 disease.

Harnessing Recent Advances in Synthetic DNA and Electroporation Technologies for Rapid Vaccine Development Against COVID-19 and Other Emerging Infectious Diseases.

DNA vaccines are considered as a third-generation vaccination approach in which antigenic materials are encoded as DNA plasmids for direct in vivo production to elicit adaptive immunity. As compared to other platforms, DNA vaccination is considered to have a strong safety profile, as DNA plasmids neither replicate nor elicit vector-directed immune responses in hosts. While earlier work found the immune responses induced by DNA vaccines to be sub-optimal in larger mammals and humans, recent developments in key synthetic DNA and electroporation delivery technologies have now allowed DNA vaccines to elicit significantly more potent and consistent responses in several clinical studies. This paper will review findings from the recent clinical and preclinical studies on DNA vaccines targeting emerging infectious diseases (EID) including COVID-19 caused by the SARS-CoV-2 virus, and the technological advancements pivotal to the improved responses-including the use of the advanced delivery technology, DNA-encoded cytokine/mucosal adjuvants, and innovative concepts in immunogen design. With continuous advancement over the past three decades, the DNA approach is now poised to develop vaccines against COVID-19, as well as other EIDs.

A DNA-Launched Nanoparticle Vaccine Elicits CD8+ T-cell Immunity to Promote In Vivo Tumor Control.

Cytolytic T cells (CTL) play a pivotal role in surveillance against tumors. Induction of CTL responses by vaccination may be challenging, as it requires direct transduction of target cells or special adjuvants to promote cross-presentation. Here, we observed induction of robust CTL responses through electroporation-facilitated, DNA-launched nanoparticle vaccination (DLnano-vaccines). Electroporation was observed to mediate transient tissue apoptosis and macrophage infiltration, which were deemed essential to the induction of CTLs by DLnano-vaccines through a systemic macrophage depletion study. Bolus delivery of protein nano-vaccines followed by electroporation, however, failed to induce CTLs, suggesting direct in vivo production of nano-vaccines may be required. Following these observations, new DLnano-vaccines scaffolding immunodominant melanoma Gp100 and Trp2 epitopes were designed and shown to induce more potent and consistent epitope-specific CTL responses than the corresponding DNA monomeric vaccines or CpG-adjuvanted peptide vaccines. DNA, but not recombinant protein, nano-vaccinations induced CTL responses to these epitopes and suppressed melanoma tumor growth in mouse models in a CD8+ T-cell-dependent fashion. Further studies to explore the use of DLnano-vaccines against other cancer targets and the biology with which they induce CTLs are important.

Synthetic DNA Vaccines Adjuvanted with pIL-33 Drive Liver-Localized T Cells and Provide Protection from Plasmodium Challenge in a Mouse Model.

The need for a malaria vaccine is indisputable. A single vaccine for Plasmodium pre-erythrocytic stages targeting the major sporozoite antigen circumsporozoite protein (CSP) has had partial success. Additionally, CD8+ T cells targeting liver-stage (LS) antigens induced by live attenuated sporozoite vaccines were associated with protection in human challenge experiments. To further evaluate protection mediated by LS antigens, we focused on exported pre-erythrocytic proteins (exported protein 1 (EXP1), profilin (PFN), exported protein 2 (EXP2), inhibitor of cysteine proteases (ICP), transmembrane protein 21 (TMP21), and upregulated in infective sporozoites-3 (UIS3)) expressed in all Plasmodium species and designed optimized, synthetic DNA (synDNA) immunogens. SynDNA antigen cocktails were tested with and without the molecular adjuvant plasmid IL-33. Immunized animals developed robust T cell responses including induction of antigen-specific liver-localized CD8+ T cells, which were enhanced by the co-delivery of plasmid IL-33. In total, 100% of mice in adjuvanted groups and 71%-88% in non-adjuvanted groups were protected from blood-stage disease following Plasmodium yoelii sporozoite challenge. This study supports the potential of synDNA LS antigens as vaccine components for malaria parasite infection.

Immunogenicity of a DNA vaccine candidate for COVID-19.

The coronavirus family member, SARS-CoV-2 has been identified as the causal agent for the pandemic viral pneumonia disease, COVID-19. At this time, no vaccine is available to control further dissemination of the disease. We have previously engineered a synthetic DNA vaccine targeting the MERS coronavirus Spike (S) protein, the major surface antigen of coronaviruses, which is currently in clinical study. Here we build on this prior experience to generate a synthetic DNA-based vaccine candidate targeting SARS-CoV-2 S protein. The engineered construct, INO-4800, results in robust expression of the S protein in vitro. Following immunization of mice and guinea pigs with INO-4800 we measure antigen-specific T cell responses, functional antibodies which neutralize the SARS-CoV-2 infection and block Spike protein binding to the ACE2 receptor, and biodistribution of SARS-CoV-2 targeting antibodies to the lungs. This preliminary dataset identifies INO-4800 as a potential COVID-19 vaccine candidate, supporting further translational study.