Potentiating the Cross-Reactive IFN-γ T Cell and Polyfunctional T Cell Responses by Heterologous GX-19N DNA Booster in Mice Primed with Either a COVID-19 mRNA Vaccine or Inactivated Vaccine.

Waning vaccine-induced immunity, coupled with the emergence of SARS-CoV-2 variants, has inspired the widespread implementation of COVID-19 booster vaccinations. Here, we evaluated the potential of the GX-19N DNA vaccine as a heterologous booster to enhance the protective immune response to SARS-CoV-2 in mice primed with either an inactivated virus particle (VP) or an mRNA vaccine. We found that in the VP-primed condition, GX-19N enhanced the response of both vaccine-specific antibodies and cross-reactive T Cells to the SARS-CoV-2 variant of concern (VOC), compared to the homologous VP vaccine prime-boost. Under the mRNA-primed condition, GX-19N induced higher vaccine-induced T Cell responses but lower antibody responses than the homologous mRNA vaccine prime-boost. Furthermore, the heterologous GX-19N boost induced higher S-specific polyfunctional CD4+ and CD8+ T cell responses than the homologous VP or mRNA prime-boost vaccinations. Our results provide new insights into booster vaccination strategies for the management of novel COVID-19 variants.

Safety and immunogenicity of two recombinant DNA COVID-19 vaccines containing the coding regions of the spike or spike and nucleocapsid proteins: an interim analysis of two open-label, non-randomised, phase 1 trials in healthy adults.

BACKGROUND: We assessed the safety and immunogenicity of two recombinant DNA vaccines for COVID-19: GX-19 containing plasmid DNA encoding the SARS-CoV-2 spike protein, and GX-19N containing plasmid DNA encoding the SARS-CoV-2 receptor-binding domain (RBD) foldon, nucleocapsid protein, and plasmid DNA encoding the spike protein. METHODS: Two open-label non-randomised phase 1 trials, one of GX-19 and the other of GX-19N were done at two hospitals in South Korea. We enrolled healthy adults aged 19-49 years for the GX-19 trial and healthy adults aged 19-54 years for the GX-19N trial. Participants who tested positive by serological testing for SARS-CoV-2 were excluded. At 4-week intervals, the GX-19 trial participants received two vaccine doses (either 1·5 mg or 3·0 mg), and the GX-19N trial participants received two 3·0 mg doses. The vaccines were delivered intramuscularly using an electroporator. The participants were followed up for 52 weeks after first vaccination. Data collected up to day 57 after first vaccination were analysed in this interim analysis. The primary outcome was safety within 28 days after each vaccination measured in the intention-to-treat population. The secondary outcome was vaccine immunogenicity using blood samples collected on day 43 or 57 after first vaccination measured in the intention-to-treat population. The GX-19 (NCT044445389) and GX-19N (NCT04715997) trials are registered with ClinicalTrials.gov. FINDINGS: Between June 17 and July 30, 2020, we screened 97 individuals, of whom 40 (41%) participants were enrolled in the GX-19 trial (20 [50%] in the 1·5 mg group and 20 [50%] in the 3·0 mg group). Between Dec 28 and 31, 2020, we screened 23 participants, of whom 21 (91%) participants were enrolled on the GX-19N trial. 32 (52%) of 61 participants reported 80 treatment-emergent adverse events after vaccination. All solicited adverse events were mild except one (2%) case of moderate fatigue in the 1·5 mg GX-19 group; no serious vaccine-related adverse events were detected. Binding antibody responses increased after second dose of vaccination in all groups (p=0·0002 in the 1·5 mg GX-19 group; p<0·0001 in the 3·0 mg GX-19; and p=0·0004 for the spike protein and p=0·0001 for the RBD in the 3·0 mg GX-19N group). INTERPRETATION: GX-19 and GX-19N are safe and well tolerated. GX-19N induces humoral and broad SARS-CoV-2-specific T-cell responses. GX-19N shows lower neutralising antibody responses and needs improvement to enhance immunogenicity. FUNDING: The Korea Drug Development Fund, funded by the Ministry of Science and ICT, Ministry of Trade, Industry, and Energy, and Ministry of Health and Welfare.

Soluble Spike DNA Vaccine Provides Long-Term Protective Immunity against SARS-CoV-2 in Mice and Nonhuman Primates.

The unprecedented and rapid spread of SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) has motivated the need for a rapidly producible and scalable vaccine. Here, we developed a synthetic soluble SARS-CoV-2 spike (S) DNA-based vaccine candidate, GX-19. In mice, immunization with GX-19 elicited not only S-specific systemic and pulmonary antibody responses but also Th1-biased T cell responses in a dose-dependent manner. GX-19-vaccinated nonhuman primates seroconverted rapidly and exhibited a detectable neutralizing antibody response as well as multifunctional CD4+ and CD8+ T cell responses. Notably, when the immunized nonhuman primates were challenged at 10 weeks after the last vaccination with GX-19, they had reduced viral loads in contrast to non-vaccinated primates as a control. These findings indicate that GX-19 vaccination provides a durable protective immune response and also support further development of GX-19 as a vaccine candidate for SARS-CoV-2.

Pembrolizumab plus GX-188E therapeutic DNA vaccine in patients with HPV-16-positive or HPV-18-positive advanced cervical cancer: interim results of a single-arm, phase 2 trial.

BACKGROUND: Survival outcomes for patients with recurrent or advanced cervical cancer are poor. Pembrolizumab has been approved for the treatment of recurrent or metastatic cervical cancer, with an overall response rate of 14·3%. GX-188E vaccination has been shown to induce human papillomavirus (HPV) E6-specific and E7-specific T-cell responses and cervical lesion regression in patients with cervical precancer. We aimed to investigate whether a combination of GX-188E therapeutic DNA vaccine plus pembrolizumab showed antitumour activity against recurrent or advanced cervical cancer. METHODS: In this open-label, single-arm, phase 2 trial, patients with recurrent or advanced, inoperable cervical cancer, who were aged 18 years or older with Eastern Cooperative Oncology Group performance status of 0 or 1 and histologically confirmed recurrent or advanced HPV-positive (HPV-16 or HPV-18) cervical cancer, and who had progressed after available standard-of-care therapy were recruited from seven hospitals in South Korea. Patients received intramuscular 2 mg GX-188E at weeks 1, 2, 4, 7, 13, and 19, with one optional dose at week 46 that was at the investigator's discretion, and intravenous pembrolizumab 200 mg every 3 weeks for up to 2 years or until disease progression. The primary endpoint was the overall response rate within 24 weeks assessed by the investigator using Response Evaluation Criteria in Solid Tumors version 1.1 in patients who received at least 45 days of treatment 45 days of treatment with at least one post-baseline tumour assessment, and this is the report of a planned interim analysis. This trial is registered with ClinicalTrials.gov, NCT03444376. FINDINGS: Between June 19, 2018, and March 20, 2020, 36 patients were enrolled and received at least one dose of the study treatment. 26 patients were evaluable for interim activity assessment, with at least one post-baseline tumour assessment at week 10. At the data cutoff date on March 30, 2020, median follow-up duration was 6·2 months (IQR 3·5-8·1). At 24 weeks, 11 (42%; 95% CI 23-63) of 26 patients achieved an overall response; four (15%) had a complete response and seven (27%) had a partial response. 16 (44%) of 36 patients had treatment-related adverse events of any grade and four (11%) had grade 3-4 treatment-related adverse events. Grade 3 increased aspartate aminotransferase, syncope, pericardial effusion, and hyperkalaemia, and grade 4 increased alanine aminotransferase were reported in one patient each. No treatment-related deaths were reported. INTERPRETATION: Treatment with GX-188E therapeutic vaccine plus pembrolizumab for patients with recurrent or advanced cervical cancer was safe and treatment-related adverse events were manageable. This combination therapy showed preliminary antitumour activity in this interim analysis, which could represent a new potential treatment option for this patient population. This trial is ongoing. FUNDING: National OncoVenture.

A Phase II, Prospective, Randomized, Multicenter, Open-Label Study of GX-188E, an HPV DNA Vaccine, in Patients with Cervical Intraepithelial Neoplasia 3.

PURPOSE: To determine the efficacy of the therapeutic DNA vaccine GX-188E for inducing regression of cervical intraepithelial neoplasia (CIN) 3. PATIENTS AND METHODS: We conducted a prospective, randomized, multicenter, open-label, phase II clinical trial of GX-188E in CIN3 patients positive for human papillomavirus (HPV) type 16/18. The primary endpoint was to determine the histopathologic regression to ≤CIN1 at visit seven (V7; 20 weeks after the first GX-188E injection), and an extension study was pursued until visit 8 (V8; 36 weeks after the first GX-188E injection). HPV-sequencing analysis and an ex vivo IFNγ ELISpot assay were performed using the collected cervical biopsy and blood samples from patients. RESULTS: In total, 72 patients were enrolled and underwent randomization. Of them, 64 patients were included in per-protocol analysis (V7) and 52 in extension analysis (V8). Our data showed 52% (33/64) of patients at V7 and 67% (35/52) of patients at V8 presented histopathologic regression after receiving the GX-188E injection. We found that 73% (V7) and 77% (V8) of the patients with histologic regression showed HPV clearance. HPV clearance and histopathologic regression were significantly associated at V7 and at V8. Compared with the measurements at V1 (baseline), the patients at V8 with HPV clearance showed significantly higher fold changes in their IFNγ ELISpot responses compared with those without HPV clearance. The HPV sequence analysis revealed that the HPV type 16 E6/E7 variants D25E, V83L, and N29S were inversely associated with histopathologic regression at V8. CONCLUSIONS: GX-188E is an effective therapeutic vaccine against a cohort containing only CIN3 patients.

Intravaginal Administration of Fc-Fused IL7 Suppresses the Cervicovaginal Tumor by Recruiting HPV DNA Vaccine-Induced CD8 T Cells.

PURPOSE: The induction of tissue-localized virus-specific CD8 T-cell response is essential for the development of an effective therapeutic vaccine against genital diseases, such as cervical cancer and genital herpes. Here, we aimed to elucidate the immunologic role of IL7 in the induction of mucosal cellular immunity. EXPERIMENTAL DESIGN: IL7 was engineered through Fc fusion to enhance mucosal delivery across the genital epithelial barrier. The immunomodulatory role of IL7 was evaluated by monitoring the kinetics of various immune cells and measuring the expression of chemokines and cytokines after intravaginal administration of Fc-fused IL7 (IL7-Fc). The antitumor effects of intramuscular human papillomavirus (HPV) DNA vaccine or topical IL7-Fc alone or in a combinational regimen on mice survival were compared using a orthotopic cervical cancer model. RESULTS: Intravaginal treatment of IL7-Fc, but not native IL7, induces upregulation of chemokines (CXCL10, CCL3, CCL4, and CCL5), cytokines (IFNγ, TNFα, IL6, and IL1ß), and an adhesion molecule (VCAM-1) in the genital tract, leading to the recruitment of several leukocytes, including CD4, CD8, γδ T cells, and dendritic cells. Importantly, in this murine cervical cancer model, topical administration of IL7-Fc after intramuscular HPV DNA vaccination increases the number of HPV-specific CD8 T cells in the genital mucosa, but not in the spleen, leading to stronger antitumor activity than the HPV DNA vaccine alone. CONCLUSIONS: Our findings provide an important insight into the immunomodulatory role of IL7-Fc via topical application and the design of therapeutic vaccine regimen that induces effective genital-mucosal CD8 T-cell responses. Clin Cancer Res; 22(23); 5898-908. ©2016 AACR.

Safety and immunogenicity of therapeutic DNA vaccine with antiviral drug in chronic HBV patients and its immunogenicity in mice.

BACKGROUND & AIMS: Here, we evaluated the safety and immunogenicity of hepatitis B virus (HBV) DNA vaccine, HB-110, in mice and Korean patients with chronic hepatitis B (CHB) undergoing adefovir dipivoxil (ADV) treatment. METHODS: For animal study, mice (BALB/c or HBV transgenic) were immunized with mHB-110, and T-cell and antibody responses were evaluated. For clinical study, 27 patients randomly received either ADV alone or ADV in combination with HB-110. Liver function tests, serum HBV DNA levels and the presence of HBeAg/anti-HBe were analysed. T-cell responses were estimated by ELISPOT and FACS analysis. RESULTS: mHB-110 induced higher T-cell and antibody responses than mHB-100 in mice. No adverse effects were observed by HB-110 cotreated with ADV. HBV-specific T-cell responses were induced in a portion of patients in medium to high dose of HB-110. Interestingly, HB-110 exhibited positive effects on ALT normalization and maintenance of HBeAg seroconversion. One patient, who received high dose of HB-110 exhibited HBeAg seroconversion during vaccination, which correlated with vaccine-induced T-cell responses without ALT elevation. CONCLUSIONS: HB-110 was safe and tolerable in CHB patients. In contrast to results in animal models, HB-110 in Korean patients exhibited weaker capability of inducing HBV-specific T-cell responses and HBeAg seroconversion than HB-100 in Caucasian patients. As Asian patients, who are generally infected via vertical transmission, appeared to have higher level of immune tolerance than Caucasian, novel approaches for breaking immune tolerance rather than enhancing immunogenicity may be more urgently demanded to develop effective therapeutic HBV DNA vaccines.

Clearance of persistent HPV infection and cervical lesion by therapeutic DNA vaccine in CIN3 patients.

Here, we demonstrate that electroporation-enhanced immunization with a rationally designed HPV DNA vaccine (GX-188E), preferentially targeting HPV antigens to dendritic cells, elicits a significant E6/E7-specific IFN-γ-producing T-cell response in all nine cervical intraepithelial neoplasia 3 (CIN3) patients. Importantly, eight out of nine patients exhibit an enhanced polyfunctional HPV-specific CD8 T-cell response as shown by an increase in cytolytic activity, proliferative capacity and secretion of effector molecules. Notably, seven out of nine patients display complete regression of their lesions and viral clearance within 36 weeks of follow up. GX-188E administration does not elicit serious vaccine-associated adverse events at all administered doses. These findings indicate that the magnitude of systemic polyfunctional CD8 T-cell response is the main contributing factor for histological, cytological and virological responses, providing valuable insights into the design of therapeutic vaccines for effectively treating persistent infections and cancers in humans.

HIV-1 protease has a genetic T-cell adjuvant effect which is negatively regulated by proteolytic activity.

HIV protease (PR) mediates the processing of human immunodeficiency virus (HIV) polyproteins and is necessary for the viral production. Recently, HIV PR was shown to possess both cytotoxic and chaperone like activity. We demonstrate here that HIV PR can serve as a genetic adjuvant that enhances the HIV Env and human papillomavirus (HPV) DNA vaccine-induced T-cell response in a dose-dependent manner, only when codelivered with DNA vaccine. Interestingly, the T-cell adjuvant effects of HIV PR were increased by introducing several mutations that inhibited its proteolytic activity, indicating that the adjuvant properties were inversely correlated with its proteolytic activity. Conversely, the introduction of a mutation in the flap region of HIV PR limiting the access to the core domain of HIV PR inhibited the T-cell adjuvant effect, suggesting that the HIV PR chaperone like activity may play a role in mediating T-cell adjuvant properties. A similar adjuvant effect was also observed in adenovirus vaccine, indicating vaccine type independency. These findings suggest that HIV PR can modulate T-cell responses elicited by a gene-based vaccine positively by inherent chaperone like activity and negatively by its proteolytic activity.

Susceptibility to Simian immunodeficiency virus ex vivo predicts outcome of a prime-boost vaccine after SIVmac239 challenge.

BACKGROUND: Efficacy assessment of AIDS vaccines relies both on preclinically challenging immunized monkeys with simian immunodeficiency virus (SIV) or monitoring infection rates in large human trials. Although conventional parameters of vaccine-induced immune responses do not completely predict outcome, existing methods for testing cellular immunity are sophisticated and difficult to establish in resource-limited settings. METHODS: We have used virus replication kinetics (VVR) on ConA-stimulated peripheral blood mononuclear cells from rhesus monkeys immunized with DNA replication-defective adenovirus vector expressing various SIV genes, as an ex vivo model, to mimic the effects of different immune effector functions on viral infection. RESULTS: VVR was attenuated by the immunization and correlated 2 weeks after first boost, with the number of interferon gamma-secreting cells and T-cell noncytotoxic antiviral responses. Importantly, VVR on the day of challenge but not interferon gamma responses correlated with viremia and with memory CD4+ T-cell measurements after SIVmac239 challenge. Similarly, T-cell noncytotoxic antiviral responses on the day of challenge correlated directly with memory CD4 T cell and inversely with plasma viremia after challenge. CONCLUSIONS: VVR thus served as a better predictor of protective capacity of the vaccine regimen in these monkeys. We suggest that VVR be considered in the evaluation of candidate AIDS vaccines in humans.

Mucosal prior to systemic application of recombinant adenovirus boosting is more immunogenic than systemic application twice but confers similar protection against SIV-challenge in DNA vaccine-primed macaques.

We investigated the immunogenicity and efficacy of a bimodal prime/boost vaccine regimen given by various routes in the Simian immunodeficiency virus (SIV) rhesus monkey model for AIDS. Twelve animals were immunized with SIV DNA-vectors followed by the application of a recombinant adenovirus (rAd5) expressing the same genes either intramuscularly (i.m.) or by oropharyngeal spray. The second rAd5-application was given i.m. All vaccinees plus six controls were challenged orally with SIVmac239 12 weeks post-final immunization. Both immunization strategies induced strong SIV Gag-specific IFN-gamma and T-cell proliferation responses and mediated a conservation of CD4(+) memory T-cells and a reduction of viral load during peak viremia following infection. Interestingly, the mucosal group was superior to the systemic group regarding breadth and strength of SIV-specific T-cell responses and exhibited lower vector specific immune responses. Therefore, our data warrant the inclusion of mucosal vector application in a vaccination regimen which makes it less invasive and easier to apply.

Enhancement of DNA Vaccine-induced Immune Responses by Influenza Virus NP Gene.

DNA immunization induces B and T cell responses to various pathogens and tumors. However, these responses are known to be relatively weak and often transient. Thus, novel strategies are necessary for enhancing immune responses induced by DNA immunization. Here, we demonstrated that co-immunization of influenza virus nucleoprotein (NP) gene significantly enhances humoral and cell-mediated responses to codelivered antigens in mice. We also found that NP DNA coimmunization augments in vivo proliferation of adoptively transferred antigen-specific CD4 and CD8 T cells, which enhanced protective immunity against tumor challenge. Our results suggest that NP DNA can serve as a novel genetic adjuvant in cocktail DNA vaccination.

Better protective effects in rhesus macaques by combining systemic and mucosal application of a dual component vector vaccine after rectal SHIV89.6P challenge compared to systemic vaccination alone.

In this study we investigated the efficacy of a multigenic DNA prime/modified vaccinia Ankara (MVA)boost vaccine approach, followed by mucosal challenge with highly pathogenic simian-human immunodeficiency virus (SHIV) 89.6P, using different routes for vaccine delivery. After three times of DNA priming (SIVmac239, GagPol, and SHIV 89.6P Env) one vaccine group of monkeys was immunized with MVA systemically via intramuscular (IM) and intradermal (ID) application, and in another vaccine group the MVA booster immunization comprised the IM, ID, and atraumatic oral route. Although all vaccinees became infected after intra-rectal challenge with SHIV 89.6P, substantial protection as indicated by lower peak and set point viral loads and unambiguous preservation of CD4 T cells could be achieved. As we could only transiently detect low levels of neutralizing antibodies in some vaccinees, these antibodies did not seem to add to the protection in the vaccinees. Our results indicate that both preventive multigenic DNA prime/MVA booster immunization strategies promote the control of virus replication and protect from disease progression. We also demonstrated that combining mucosal and systemic vaccination mediated better protective effects compared to systemic vaccination alone.

Immunogenicity of a DNA prime and recombinant adenovirus boost regime significantly varies between rhesus macaques of Chinese and Indian origins.

BACKGROUND: Due to an ever increasing shortage of rhesus macaques of Indian origin (InR) that have been generally used for preclinical AIDS vaccine trials in non-human primates, demand is rising for Chinese rhesus macaques (ChR). However, the immunogenicity of an AIDS vaccine candidate has not been compared in parallel in both rhesus macaque subspecies. METHODS: ChR and InR were immunized with SIV/HIV DNA and adenovirus vaccine and their immune responses to SIV and HIV evaluated. RESULTS: SIV Gag- and Env-specific T-cell responses and SIV-specific lymphoproliferative responses measured in ChR were significantly weaker than those in InR (P < 0.05). By contrast, antibody responses to SIV Env, Tat, and Nef in ChR were stronger than those in InR (P < 0.05). CONCLUSIONS: Immunogenicity of an AIDS vaccine can vary significantly depending on the geographic origin implying genetic differences of macaques. This must be considered when describing and interpreting results of such vaccine studies.

A single vaccination with attenuated SIVmac 239 via the tonsillar route confers partial protection against challenge with SIVmac 251 at a distant mucosal site, the rectum.

Elucidating the mechanisms that protect monkeys previously immunized with attenuated SIV (SIVDeltanef) against challenge infection with pathogenic virus may reveal new strategies for the development of an effective HIV vaccine. Here we show that a single atraumatic application of SIVDeltanef to the tonsils of four rhesus macaques conferred protection against SIVmac251 applied intrarectally 26 weeks later. While this protection was not complete, i.e., challenge virus could be isolated from all immunized animals, it was reflected by significantly lower viral loads in the blood (weeks 2-16 after challenge, p < 0.01) and considerably lower loads in lymphoid organs, and more stable peripheral CD4 counts in a proportion of the immunized animals as compared to four non-immunized, SIVmac251-infected control monkeys. SIV-specific humoral as well as systemic and mucosal T cell responses were detected in the immunized animals, but there was no correlation between their magnitude of expression and the level of protection. Analyses of leukocyte subsets in these animals at necropsy (24 weeks after challenge) did not reveal a significantly enhanced proportion of gamma/delta T cells in the tissues of protected monkeys. Therefore, tonsillar application of attenuated SIV induces protection in some animals against a superinfection with wild-type SIV distant at a distant mucosal site.

CpG oligonucleotides induce strong humoral but only weak CD4+ T cell responses to protein antigens in rhesus macaques in vivo.

Oligonucleotides containing CpG motifs (CpG ODN) are strong adjuvants for humoral immune responses but data on cellular immune responses in primates are scarce. Rhesus macaque blood contained similar numbers of plasmacytoid dendritic cells and B cells, the key sensors of CpG ODN, as human blood, and these cells were activated by CpG-A and CpG-B in vitro. In vivo, both ODNs induced equal plasma levels of interferon-inducible protein 10 and similarly enhanced antibody responses following i.m. injections of the ODNs, protein antigen, and aluminium hydroxide into rhesus macaques, whereas antigen-specific CD4(+) T cell responses were only slightly increased by CpG ODN.

In vivo kinetics and biodistribution of a HIV-1 DNA vaccine after administration in mice.

In this study we have investigated the pharmacokinetics and tissue distribution of GX-12, a multiple plasmid DNA vaccine for the treatment of HIV-1 infection. Plasmid DNA was rapidly degraded in blood with a half-life of 1.34 min and was no longer detectable at 90 min after intravenous injection in mice. After intramuscular injection, plasmid DNA concentration in the injection site rapidly declined to less than 1% of the initial concentration by 90 min post-injection. However, sub-picogram levels (per mg tissue) were occasionally detected for several days after injection. The relative proportions of the individual plasmids of GX-12 remained relatively constant at the injection site until 90 min post-injection. The concentration of plasmid DNA in tissues other than the injection site peaked at 90 min post-injection and decreased to undetectable levels at 8 h post-injection. The rapid in vivo degradation of GX-12 and absence of persistence in non-target tissues suggest that the risk of potential gene-related toxicities by GX-12 administration, such as expression in non-target tissues, insertional mutagenesis and germline transmission, is minimal.