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.

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.

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.

Incorporation of a Novel CD4+ Helper Epitope Identified from Aquifex aeolicus Enhances Humoral Responses Induced by DNA and Protein Vaccinations.

CD4+ T cells play an important role in the maturation of the antibody responses. Conjugation of identified CD4+ T cell helper epitope to the target antigen has been developed as a strategy to enhance vaccine-induced humoral immunity. In this work, we reported the identification of a novel HLA-IAb helper epitope LS-3 from Aquifex aeolicus. In silico analysis predicted this epitope to have high binding affinity to common human HLA alleles and have complementary binding coverage to the established PADRE epitope. Introduction of HLA-IAb knockout mutations to the LS-3 epitope significantly attenuated humoral responses induced by a vaccine containing this epitope. Finally, engineered fusion of the epitope to a model antigen, influenza hemagglutinin, significantly improved both binding and hemagglutination inhibition antibody responses in mice receiving DNA or protein vaccines. In summary, LS-3 and additional identified CD4+ helper epitopes may be further explored to improve vaccine responses in translational studies.

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.

In vivo delivery of synthetic DNA-encoded antibodies induces broad HIV-1-neutralizing activity.

Interventions to prevent HIV-1 infection and alternative tools in HIV cure therapy remain pressing goals. Recently, numerous broadly neutralizing HIV-1 monoclonal antibodies (bNAbs) have been developed that possess the characteristics necessary for potential prophylactic or therapeutic approaches. However, formulation complexities, especially for multiantibody deliveries, long infusion times, and production issues could limit the use of these bNAbs when deployed, globally affecting their potential application. Here, we describe an approach utilizing synthetic DNA-encoded monoclonal antibodies (dmAbs) for direct in vivo production of prespecified neutralizing activity. We designed 16 different bNAbs as dmAb cassettes and studied their activity in small and large animals. Sera from animals administered dmAbs neutralized multiple HIV-1 isolates with activity similar to that of their parental recombinant mAbs. Delivery of multiple dmAbs to a single animal led to increased neutralization breadth. Two dmAbs, PGDM1400 and PGT121, were advanced into nonhuman primates for study. High peak-circulating levels (between 6 and 34 µg/ml) of these dmAbs were measured, and the sera of all animals displayed broad neutralizing activity. The dmAb approach provides an important local delivery platform for the in vivo generation of HIV-1 bNAbs and for other infectious disease antibodies.

In Vivo Assembly of Nanoparticles Achieved through Synergy of Structure-Based Protein Engineering and Synthetic DNA Generates Enhanced Adaptive Immunity.

Nanotechnologies are considered to be of growing importance to the vaccine field. Through decoration of immunogens on multivalent nanoparticles, designed nanovaccines can elicit improved humoral immunity. However, significant practical and monetary challenges in large-scale production of nanovaccines have impeded their widespread clinical translation. Here, an alternative approach is illustrated integrating computational protein modeling and adaptive electroporation-mediated synthetic DNA delivery, thus enabling direct in vivo production of nanovaccines. DNA-launched nanoparticles are demonstrated displaying an HIV immunogen spontaneously self-assembled in vivo. DNA-launched nanovaccines induce stronger humoral responses than their monomeric counterparts in both mice and guinea pigs, and uniquely elicit CD8+ effector T-cell immunity as compared to recombinant protein nanovaccines. Improvements in vaccine responses recapitulate when DNA-launched nanovaccines with alternative scaffolds and decorated antigen are designed and evaluated. Finally, evaluation of functional immune responses induced by DLnanovaccines demonstrates that, in comparison to control mice or mice immunized with DNA-encoded hemagglutinin monomer, mice immunized with a DNA-launched hemagglutinin nanoparticle vaccine fully survive a lethal influenza challenge, and have substantially lower viral load, weight loss, and influenza-induced lung pathology. Additional study of these next-generation in vivo-produced nanovaccines may offer advantages for immunization against multiple disease targets.

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.

DNA-encoded bispecific T cell engagers and antibodies present long-term antitumor activity.

Specific antibody therapy, including mAbs and bispecific T cell engagers (BiTEs), are important new tools for cancer immunotherapy. However, these approaches are slow to develop and may be limited in their production, thus restricting the patients who can access these treatments. BiTEs exhibit a particularly short half-life and difficult production. The development of an approach allowing simplified development, delivery, and in vivo production would be an important advance. Here we describe the development of a designed synthetic DNA plasmid, which we optimized to permit high expression of an anti-HER2 antibody (HER2dMAb) and delivered it into animals through adaptive electroporation. HER2dMAb was efficiently expressed in vitro and in vivo, reaching levels of 50 µg/ml in mouse sera. Mechanistically, HER2dMAb blocked HER2 signaling and induced antibody-dependent cytotoxicity. HER2dMAb delayed tumor progression for HER2-expressing ovarian and breast cancer models. We next used the HER2dMAb single-chain variable fragment portion to engineer a DNA-encoded BiTE (DBiTE). This HER2DBiTE was expressed in vivo for approximately 4 months after a single administration. The HER2DBiTE was highly cytolytic and delayed cancer progression in mice. These studies illustrate an approach to generate DBiTEs in vivo, which represent promising immunotherapies for HER2+ tumors, including ovarian and potentially other cancers.

Synthetic DNA delivery by electroporation promotes robust in vivo sulfation of broadly neutralizing anti-HIV immunoadhesin eCD4-Ig.

BACKGROUND: Despite vigorous and ongoing efforts, active immunizations have yet to induce broadly neutralizing antibodies (bNAbs) against HIV-1. An alternative approach is to achieve prophylaxis with long-term expression of potent biologic HIV-1 inhibitors with Adeno-associated Virus (AAV), which could however be limited by hosts' humoral and cellular responses. An approach that facilitates in vivo production of these complex molecules independent of viral-vectored delivery will be a major advantage. METHODS: We used synthetic DNA and electroporation (DNA/EP) to deliver an anti-HIV-1 immunoadhesin eCD4-Ig in vivo. In addition, we engineered a TPST2 enzyme variant (IgE-TPST2), characterized its intracellular trafficking patterns and determined its ability to post-translationally sulfate eCD4-Ig in vivo. FINDINGS: With a single round of DNA injection, a peak expression level of 80-100µg/mL was observed in mice 14 days post injection (d.p.i). The engineered IgE-TPST2 enzyme trafficked efficiently to the Trans-Golgi Network (TGN). Co-administrating low dose of plasmid IgE-TPST2 with plasmid eCD4-Ig enhanced the potency of eCD4-Ig by three-fold in the ex vivo neutralization assay against the global panel of HIV-1 pseudoviruses. INTERPRETATION: This work provides a proof-of-concept for delivering anti-HIV-1 immunoadhesins by advanced nucleic acid technology and modulating protein functions in vivo with targeted enzyme-mediated post-translational modifications. FUNDING: This work is supported by NIH IPCAVD Grant U19 Al109646-04, Martin Delaney Collaboration for HIV Cure Research and W.W. Smith Charitable Trust.