Safety and Immunogenicity of an Anti-Zika Virus DNA Vaccine.

BACKGROUND: Although Zika virus (ZIKV) infection is typically self-limiting, other associated complications such as congenital birth defects and the Guillain-Barré syndrome are well described. There are no approved vaccines against ZIKV infection. METHODS: In this phase 1, open-label clinical trial, we evaluated the safety and immunogenicity of a synthetic, consensus DNA vaccine (GLS-5700) encoding the ZIKV premembrane and envelope proteins in two groups of 20 participants each. The participants received either 1 mg or 2 mg of vaccine intradermally, with each injection followed by electroporation (the use of a pulsed electric field to introduce the DNA sequence into cells) at baseline, 4 weeks, and 12 weeks. RESULTS: The median age of the participants was 38 years, and 60% were women; 78% were White and 22% Black; in addition, 30% were Hispanic. At the interim analysis at 14 weeks (i.e., after the third dose of vaccine), no serious adverse events were reported. Local reactions at the vaccination site (e.g., injection-site pain, redness, swelling, and itching) occurred in approximately 50% of the participants. After the third dose of vaccine, binding antibodies (as measured on enzyme-linked immunosorbent assay) were detected in all the participants, with geometric mean titers of 1642 and 2871 in recipients of 1 mg and 2 mg of vaccine, respectively. Neutralizing antibodies developed in 62% of the samples on Vero-cell assay. On neuronal-cell assay, there was 90% inhibition of ZIKV infection in 70% of the serum samples and 50% inhibition in 95% of the samples. The intraperitoneal injection of postvaccination serum protected 103 of 112 IFNAR knockout mice (bred with deletion of genes encoding interferon-α and interferon-ß receptors) (92%) that were challenged with a lethal dose of ZIKV-PR209 strain; none of the mice receiving baseline serum survived the challenge. Survival was independent of the neutralization titer. CONCLUSIONS: In this phase 1, open-label clinical trial, a DNA vaccine elicited anti-ZIKV immune responses. Further studies are needed to better evaluate the safety and efficacy of the vaccine. (Funded by GeneOne Life Science and others; ZIKA-001 ClinicalTrials.gov number, NCT02809443.).

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.

Irreversible Inactivation of SARS-CoV-2 by Lectin Engagement with Two Glycan Clusters on the Spike Protein.

Host cell infection by SARS-CoV-2, similar to that by HIV-1, is driven by a conformationally metastable and highly glycosylated surface entry protein complex, and infection by these viruses has been shown to be inhibited by the mannose-specific lectins cyanovirin-N (CV-N) and griffithsin (GRFT). We discovered in this study that CV-N not only inhibits SARS-CoV-2 infection but also leads to irreversibly inactivated pseudovirus particles. The irreversibility effect was revealed by the observation that pseudoviruses first treated with CV-N and then washed to remove all soluble lectin did not recover infectivity. The infection inhibition of SARS-CoV-2 pseudovirus mutants with single-site glycan mutations in spike suggested that two glycan clusters in S1 are important for both CV-N and GRFT inhibition: one cluster associated with the RBD (receptor binding domain) and the second with the S1/S2 cleavage site. We observed lectin antiviral effects with several SARS-CoV-2 pseudovirus variants, including the recently emerged omicron, as well as a fully infectious coronavirus, therein reflecting the breadth of lectin antiviral function and the potential for pan-coronavirus inactivation. Mechanistically, observations made in this work indicate that multivalent lectin interaction with S1 glycans is likely a driver of the lectin infection inhibition and irreversible inactivation effect and suggest the possibility that lectin inactivation is caused by an irreversible conformational effect on spike. Overall, lectins' irreversible inactivation of SARS-CoV-2, taken with their breadth of function, reflects the therapeutic potential of multivalent lectins targeting the vulnerable metastable spike before host cell encounter.

Siglec-9 defines and restrains a natural killer subpopulation highly cytotoxic to HIV-infected cells.

Siglec-9 is an MHC-independent inhibitory receptor expressed on a subset of natural killer (NK) cells. Siglec-9 restrains NK cytotoxicity by binding to sialoglycans (sialic acid-containing glycans) on target cells. Despite the importance of Siglec-9 interactions in tumor immune evasion, their role as an immune evasion mechanism during HIV infection has not been investigated. Using in vivo phenotypic analyses, we found that Siglec-9+ CD56dim NK cells, during HIV infection, exhibit an activated phenotype with higher expression of activating receptors and markers (NKp30, CD38, CD16, DNAM-1, perforin) and lower expression of the inhibitory receptor NKG2A, compared to Siglec-9- CD56dim NK cells. We also found that levels of Siglec-9+ CD56dim NK cells inversely correlate with viral load during viremic infection and CD4+ T cell-associated HIV DNA during suppressed infection. Using in vitro cytotoxicity assays, we confirmed that Siglec-9+ NK cells exhibit higher cytotoxicity towards HIV-infected cells compared to Siglec-9- NK cells. These data are consistent with the notion that Siglec-9+ NK cells are highly cytotoxic against HIV-infected cells. However, blocking Siglec-9 enhanced NK cells' ability to lyse HIV-infected cells, consistent with the known inhibitory function of the Siglec-9 molecule. Together, these data support a model in which the Siglec-9+ CD56dim NK subpopulation is highly cytotoxic against HIV-infected cells even whilst being restrained by the inhibitory effects of Siglec-9. To harness the cytotoxic capacity of the Siglec-9+ NK subpopulation, which is dampened by Siglec-9, we developed a proof-of-concept approach to selectively disrupt Siglec/sialoglycan interactions between NK and HIV-infected cells. We achieved this goal by conjugating Sialidase to several HIV broadly neutralizing antibodies. These conjugates selectively desialylated HIV-infected cells and enhanced NK cells' capacity to kill them. In summary, we identified a novel, glycan-based interaction that may contribute to HIV-infected cells' ability to evade NK immunosurveillance and developed an approach to break this interaction.

Debulking SARS-CoV-2 in saliva using angiotensin converting enzyme 2 in chewing gum to decrease oral virus transmission and infection.

To advance a novel concept of debulking virus in the oral cavity, the primary site of viral replication, virus-trapping proteins CTB-ACE2 were expressed in chloroplasts and clinical-grade plant material was developed to meet FDA requirements. Chewing gum (2 g) containing plant cells expressed CTB-ACE2 up to 17.2 mg ACE2/g dry weight (11.7% leaf protein), have physical characteristics and taste/flavor like conventional gums, and no protein was lost during gum compression. CTB-ACE2 gum efficiently (>95%) inhibited entry of lentivirus spike or VSV-spike pseudovirus into Vero/CHO cells when quantified by luciferase or red fluorescence. Incubation of CTB-ACE2 microparticles reduced SARS-CoV-2 virus count in COVID-19 swab/saliva samples by >95% when evaluated by microbubbles (femtomolar concentration) or qPCR, demonstrating both virus trapping and blocking of cellular entry. COVID-19 saliva samples showed low or undetectable ACE2 activity when compared with healthy individuals (2,582 versus 50,126 ΔRFU; 27 versus 225 enzyme units), confirming greater susceptibility of infected patients for viral entry. CTB-ACE2 activity was completely inhibited by pre-incubation with SARS-CoV-2 receptor-binding domain, offering an explanation for reduced saliva ACE2 activity among COVID-19 patients. Chewing gum with virus-trapping proteins offers a general affordable strategy to protect patients from most oral virus re-infections through debulking or minimizing transmission to others.

SARS-CoV-2 DNA Vaccine INO-4800 Induces Durable Immune Responses Capable of Being Boosted in a Phase 1 Open-Label Trial.

BACKGROUND: Additional severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines that are safe and effective as primary vaccines and boosters remain urgently needed to combat the coronavirus disease 2019 (COVID-19) pandemic. We describe safety and durability of immune responses following 2 primary doses and a homologous booster dose of an investigational DNA vaccine (INO-4800) targeting full-length spike antigen. METHODS: Three dosage strengths of INO-4800 (0.5 mg, 1.0 mg, and 2.0 mg) were evaluated in 120 age-stratified healthy adults. Intradermal injection of INO-4800 followed by electroporation at 0 and 4 weeks preceded an optional booster 6-10.5 months after the second dose. RESULTS: INO-4800 appeared well tolerated with no treatment-related serious adverse events. Most adverse events were mild and did not increase in frequency with age and subsequent dosing. A durable antibody response was observed 6 months following the second dose; a homologous booster dose significantly increased immune responses. Cytokine-producing T cells and activated CD8+ T cells with lytic potential were significantly increased in the 2.0-mg dose group. CONCLUSIONS: INO-4800 was well tolerated in a 2-dose primary series and homologous booster in all adults, including elderly participants. These results support further development of INO-4800 for use as primary vaccine and booster. CLINICAL TRIALS REGISTRATION: NCT04336410.

Establishment of a Pig Influenza Challenge Model for Evaluation of Monoclonal Antibody Delivery Platforms.

mAbs are a possible adjunct to vaccination and drugs in treatment of influenza virus infection. However, questions remain whether small animal models accurately predict efficacy in humans. We have established the pig, a large natural host animal for influenza, with many physiological similarities to humans, as a robust model for testing mAbs. We show that a strongly neutralizing mAb (2-12C) against the hemagglutinin head administered prophylactically at 15 mg/kg reduced viral load and lung pathology after pandemic H1N1 influenza challenge. A lower dose of 1 mg/kg of 2-12C or a DNA plasmid-encoded version of 2-12C reduced pathology and viral load in the lungs but not viral shedding in nasal swabs. We propose that the pig influenza model will be useful for testing candidate mAbs and emerging delivery platforms prior to human trials.

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.

CD8+ T Cells Impact Rising PSA in Biochemically Relapsed Cancer Patients Using Immunotherapy Targeting Tumor-Associated Antigens.

The management of men with prostate cancer (PCa) with biochemical recurrence following local definitive therapy remains controversial. Early use of androgen deprivation therapy (ADT) leads to significant side effects. Developing an alternative, clinically effective, and well-tolerated therapy remains an unmet clinical need. INO-5150 is a synthetic DNA therapy that includes plasmids encoding for prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA), and INO-9012 is a synthetic DNA plasmid encoding for interleukin-12 (IL-12). This phase 1/2, open-label, multi-center study enrolled men with PCa with rising PSA after surgery and/or radiation therapy. Patients were enrolled into one of four treatment arms: arm A, 2 mg of INO-5150; arm B, 8.5 mg of INO-5150; arm C, 2 mg of INO-5150 + 1 mg of INO-9012; and arm D, 8.5 mg of INO-5150 + 1 mg of INO-9012. Patients received study drug with electroporation on day 0 and on weeks 3, 12, and 24, and they were followed for up to 72 weeks. Sixty-two patients were enrolled. Treatment was well tolerated. 81% (50/62) of patients completed all visits. 85% (53/62) remained progression-free at 72 weeks. PSA doubling time (PSADT) was increased when assessed in patients with day 0 PSADT ≤12 months. Immunogenicity was observed in 76% (47/62) of patients by multiple assessments. Analysis indicated that CD38 and perforin co-positive CD8 T cell frequency correlated with attenuated PSA rise (p = 0.05, n = 50).

IFNL3-adjuvanted HCV DNA vaccine reduces regulatory T cell frequency and increases virus-specific T cell responses.

BACKGROUND & AIMS: Although direct-acting antiviral (DAA) treatment results in a sustained virologic response (SVR) in most patients with chronic HCV infection, they are at risk of re-infection. Moreover, the immune system is not completely normalized even after SVR (e.g. increased regulatory T [Treg] cell frequency). We developed a DNA vaccine, GLS-6150, to prevent re-infection of patients with DAA-induced SVR and evaluated its safety and immunogenicity in individuals with chronic HCV infection. METHODS: GLS-6150 consists of plasmids encoding HCV non-structural proteins (NS3-NS5A) and adjuvant IFNL3. The vaccine was administered 4 times at 4-weekly intervals to 3 groups (1, 3, or 6 mg/vaccination; n = 6 per group), followed by a 6 mg boost at 24 weeks (n = 14). Peripheral blood T cell responses were evaluated by interferon (IFN)-γ enzyme-linked immunospot assays, intracellular cytokine staining, and major histocompatibility complex class-I (MHC-I) dextramer staining. Treg cell frequency was assessed by flow cytometry. RESULTS: Severe adverse events or vaccine discontinuation were not reported. The IFN-γ spot-forming cells specific to NS3-NS5A were increased by GLS-6150. Both CD4+ and CD8+ T cells produced multiple cytokines. However, the frequency and phenotype of HCV-specific MHC-I dextramer+CD8+ T cells were not changed. Interestingly, the frequency of Treg cells, particularly activated Treg cells, was decreased by GLS-6150, as expected from previous reports that IFNL3 adjuvants decrease Treg cell frequency. Ex vivo IFN-λ3 treatment reduced Treg frequency in pre-vaccination peripheral blood mononuclear cells. Finally, Treg cell frequency inversely correlated with HCV-specific, IFN-γ-producing T cell responses in the study participants. CONCLUSIONS: We demonstrate that GLS-6150 decreases Treg cell frequency and enhances HCV-specific T cell responses without significant side effects. A phase I clinical trial of GLS-6150 is currently underway in patients with DAA-induced SVR. CLINICAL TRIAL NUMBER: NCT02027116. LAY SUMMARY: Although direct-acting antivirals (DAAs) are successfully used for the treatment of chronic hepatitis C virus (HCV) infection, a prophylactic HCV vaccine needs to be developed, especially for patients who achieve a sustained virologic response. In the current study, we show that a DNA vaccine (GLS-6150) was safe and increased HCV-specific T cell responses. A clinical trial is underway to test this vaccine in patients with a sustained virologic response following DAA therapy.

SARS-CoV-2 Assays To Detect Functional Antibody Responses That Block ACE2 Recognition in Vaccinated Animals and Infected Patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic of COVID-19, resulting in cases of mild to severe respiratory distress and significant mortality. The global outbreak of this novel coronavirus has now infected >20 million people worldwide, with >5 million cases in the United States (11 August 2020). The development of diagnostic and research tools to determine infection and vaccine efficacy is critically needed. We have developed multiple serologic assays using newly designed SARS-CoV-2 reagents for detecting the presence of receptor-binding antibodies in sera. The first assay is surface plasmon resonance (SPR) based and can quantitate both antibody binding to the SARS-CoV-2 spike protein and blocking to the Angiotensin-converting enzyme 2 (ACE2) receptor in a single experiment. The second assay is enzyme-linked immunosorbent assay (ELISA) based and can measure competition and blocking of the ACE2 receptor to the SARS-CoV-2 spike protein with antispike antibodies. The assay is highly versatile, and we demonstrate the broad utility of the assay by measuring antibody functionality of sera from small animals and nonhuman primates immunized with an experimental SARS-CoV-2 vaccine. In addition, we employ the assay to measure receptor blocking of sera from SARS-CoV-2-infected patients. The assay is shown to correlate with pseudovirus neutralization titers. This type of rapid, surrogate neutralization diagnostic can be employed widely to help study SARS-CoV-2 infection and assess the efficacy of vaccines.

Development of Novel DNA-Encoded PCSK9 Monoclonal Antibodies as Lipid-Lowering Therapeutics.

Elevated low-density lipoprotein cholesterol (LDL-C) is one of the major contributors to cardiovascular heart disease (CHD), the leading cause of death worldwide. Due to severe side effects of statins, alternative treatment strategies are required for statin-intolerant patients. Monoclonal antibodies (mAbs) targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) have shown great efficacy in LDL-C reduction. Limitations for this approach include the need for multiple injections as well as increased costs associated with patient management. Here, we engineered a DNA-encoded mAb (DMAb) targeting PCSK9 (daPCSK9), as an alternative approach to protein-based lipid-lowering therapeutics, and we characterized its expression and activity. A single intramuscular administration of mouse daPCSK9 generated expression in vivo for over 42 days that corresponded with a substantial decrease of 28.6% in non-high-density lipoprotein cholesterol (non-HDL-C) and 10.3% in total cholesterol by day 7 in wild-type mice. Repeated administrations of the DMAb plasmid led to increasing expression, with DMAb levels of 7.5 µg/mL at day 62. daPCSK9 therapeutics may provide a novel, simple, less frequent, cost-effective approach to reducing LDL-C, either as a stand-alone therapy or in combination with other LDL-lowering therapeutics for synergistic effect.

Engineered DNA Vaccination against Follicle-Stimulating Hormone Receptor Delays Ovarian Cancer Progression in Animal Models.

Ovarian cancer presents in 80% of patients as a metastatic disease, which confers it with dismal prognosis despite surgery and chemotherapy. However, it is an immunogenic disease, and the presence of intratumoral T cells is a major prognostic factor for survival. We used a synthetic consensus (SynCon) approach to generate a novel DNA vaccine that breaks immune tolerance to follicle-stimulating hormone receptor (FSHR), present in 50% of ovarian cancers but confined to the ovary in healthy tissues. SynCon FSHR DNA vaccine generated robust CD8+ and CD4+ cellular immune responses and FSHR-redirected antibodies. The SynCon FSHR DNA vaccine delayed the progression of a highly aggressive ovarian cancer model with peritoneal carcinomatosis in immunocompetent mice, and it increased the infiltration of anti-tumor CD8+ T cells in the tumor microenvironment. Anti-tumor activity of this FSHR vaccine was confirmed in a syngeneic murine FSHR-expressing prostate cancer model. Furthermore, adoptive transfer of vaccine-primed CD8+ T cells after ex vivo expansion delayed ovarian cancer progression. In conclusion, the SynCon FSHR vaccine was able to break immune tolerance and elicit an effective anti-tumor response associated with an increase in tumor-infiltrating T cells. FSHR DNA vaccination could help current ovarian cancer therapy after first-line treatment of FSHR+ tumors to prevent tumor recurrence.

In Vivo Delivery of a DNA-Encoded Monoclonal Antibody Protects Non-human Primates against Zika Virus.

Zika virus (ZIKV) infection is endemic to several world regions, and many others are at high risk for seasonal outbreaks. Synthetic DNA-encoded monoclonal antibody (DMAb) is an approach that enables in vivo delivery of highly potent mAbs to control infections. We engineered DMAb-ZK190, encoding the mAb ZK190 neutralizing antibody, which targets the ZIKV E protein DIII domain. In vivo-delivered DMAb-ZK190 achieved expression levels persisting >10 weeks in mice and >3 weeks in non-human primate (NHPs), which is protective against ZIKV infectious challenge. This study is the first demonstration of infectious disease control in NHPs following in vivo delivery of a nucleic acid-encoded antibody, supporting the importance of this new platform.

Anti-OspA DNA-Encoded Monoclonal Antibody Prevents Transmission of Spirochetes in Tick Challenge Providing Sterilizing Immunity in Mice.

We recently developed anti-OspA human immunoglobulin G1 monoclonal antibodies (HuMAbs) that are effective in preventing Borrelia transmission from ticks in a murine model. Here, we investigated a novel approach of DNA-mediated gene transfer of HuMAbs that provide protection against Lyme disease. Plasmid DNA-encoded anti-OspA HuMAbs inoculated in mice achieved a serum antibody concentration of >6 µg/mL. Among mice injected with DNA-encoded monoclonal antibodies, 75%-77% were protected against an acute challenge by Borrelia-infected ticks. Our results represent the first demonstration of employing DNA transfer as a delivery system for antibodies that block transmission of Borrelia in animal models.

Intradermal SynCon® Ebola GP DNA Vaccine Is Temperature Stable and Safely Demonstrates Cellular and Humoral Immunogenicity Advantages in Healthy Volunteers.

BACKGROUND: Nonlive vaccine approaches that are simple to deliver and stable at room temperature or 2-8°C could be advantageous in controlling future Ebola virus (EBOV) outbreaks. Using an immunopotent DNA vaccine that generates protection from lethal EBOV challenge in small animals and nonhuman primates, we performed a clinical study to evaluate both intramuscular (IM) and novel intradermal (ID) DNA delivery. METHODS: Two DNA vaccine candidates (INO-4201 and INO-4202) targeting the EBOV glycoprotein (GP) were evaluated for safety, tolerability, and immunogenicity in a phase 1 clinical trial. The candidates were evaluated alone, together, or in combination with plasmid-encoded human cytokine interleukin-12 followed by in vivo electroporation using either the CELLECTRA® IM or ID delivery devices. RESULTS: The safety profile of all 5 regimens was shown to be benign, with the ID route being better tolerated. Antibodies to EBOV GP were generated by all 5 regimens with the fastest and steepest rise observed in the ID group. Cellular immune responses were generated with every regimen. CONCLUSIONS: ID delivery of INO-4201 was well tolerated and resulted in 100% seroreactivity after 2 doses and elicited interferon-γ T-cell responses in over 70% of subjects, providing a new approach for EBOV prevention in diverse populations. Clinical Trials Registration. NCT02464670.

Zika-Induced Male Infertility in Mice Is Potentially Reversible and Preventable by Deoxyribonucleic Acid Immunization.

Background: Zika virus (ZIKV) infection has been associated with prolonged viral excretion in human semen and causes testicular atrophy and infertility in 10-week-old immunodeficient mice. Methods: Male IFNAR-/- mice, knockout for type I interferon receptor, were immunized with GLS-5700, a deoxyribonucleic acid-based vaccine, before a subcutaneous ZIKV challenge with 6 × 105 plaque-forming units at 13 weeks of age. On day 28 postinfection, testes and epididymides were collected in some mice for histological and functional analyses, whereas others were mated with naive female wild-type C57BL/6J. Results: Although all mice challenged with ZIKV developed viremia, most of them were asymptomatic, showed no weight loss, and survived infection. On day 28 postinfection, none of the unvaccinated, infected mice (9 of 9) exhibited abnormal spermatozoa counts or motility. However, 33% (3 of 9) and 36% (4 of 11) of mated males from this group were infertile, from 2 independent studies. Contrarily, males from the noninfected and the vaccinated, infected groups were all fertile. On days 75 and 207 postinfection, partial recovery of fertility was observed in 66% (2 of 3) of the previously infertile males. Conclusions: This study reports the effects of ZIKV infection on male fertility in a sublethal, immunodeficient mouse model and the efficacy of GLS-5700 vaccination in preventing male infertility.

Protective Efficacy and Long-Term Immunogenicity in Cynomolgus Macaques by Ebola Virus Glycoprotein Synthetic DNA Vaccines.

Background: There remains an important need for prophylactic anti-Ebola virus vaccine candidates that elicit long-lasting immune responses and can be delivered to vulnerable populations that are unable to receive live-attenuated or viral vector vaccines. Methods: We designed novel synthetic anti-Ebola virus glycoprotein (EBOV-GP) DNA vaccines as a strategy to expand protective breadth against diverse EBOV strains and evaluated the impact of vaccine dosing and route of administration on protection against lethal EBOV-Makona challenge in cynomolgus macaques. Long-term immunogenicity was monitored in nonhuman primates for >1 year, followed by a 12-month boost. Results: Multiple-injection regimens of the EBOV-GP DNA vaccine, delivered by intramuscular administration followed by electroporation, were 100% protective against lethal EBOV-Makona challenge. Impressively, 2 injections of a simple, more tolerable, and dose-sparing intradermal administration followed by electroporation generated strong immunogenicity and was 100% protective against lethal challenge. In parallel, we observed that EBOV-GP DNA vaccination induced long-term immune responses in macaques that were detectable for at least 1 year after final vaccination and generated a strong recall response after the final boost. Conclusions: These data support that this simple intradermal-administered, serology-independent approach is likely important for additional study towards the goal of induction of anti-EBOV immunity in multiple at-risk populations.

Intradermal Synthetic DNA Vaccination Generates Leishmania-Specific T Cells in the Skin and Protection against Leishmania major.

Vaccination remains one of the greatest medical breakthroughs in human history and has resulted in the near eradication of many formerly lethal diseases in many countries, including the complete eradication of smallpox. However, there remain a number of diseases for which there are no or only partially effective vaccines. There are numerous hurdles in vaccine development, of which knowing the appropriate immune response to target is one of them. Recently, tissue-resident T cells have been shown to mediate high levels of protection for several infections, although the best way to induce these cells is still unclear. Here we compare the ability to generate skin-resident T cells in sites distant from the immunization site following intramuscular and intradermal injection using optimized synthetic DNA vaccines. We found that mice immunized intradermally with a synthetic consensus DNA HIV envelope vaccine by electroporation (EP) are better able to maintain durable antigen-specific cellular responses in the skin than mice immunized by the intramuscular route. We extended these studies by delivering a synthetic DNA vaccine encoding Leishmania glycosomal phosphoenolpyruvate carboxykinase (PEPCK) by EP and again found that the intradermal route was superior to the intramuscular route for generating skin-resident PEPCK-specific T cells. We observed that when challenged with Leishmania major parasites, mice immunized intradermally exhibited significant protection, while mice immunized intramuscularly did not. The protection seen in intradermally vaccinated mice supports the viability of this platform not only to generate skin-resident T cells but also to promote durable protective immune responses at relevant tissue sites.