Optimization of Zika DNA vaccine by delivery systems

Bovine serum albumin nanoparticles containing Poly (I:C) can enhance the neutralizing antibody response induced by envelope protein of Orthoflavivirus zikaense

Since the Orthoflavivirus zikaense (ZIKV) has been considered a risk for Zika congenital syndrome development, developing a safe and effective vaccine has become a high priority. Numerous research groups have developed strategies to prevent ZIKV infection and have identified the domain III of the ZIKV envelope protein (zEDIII) as a promising target. Subunit antigens are often poorly immunogenic, necessitating the use of adjuvants and/or delivery systems to induce optimal immune responses. The subject of nanotechnology has substantial expansion in recent years in terms of research and applications. Nanoparticles could be used as drug delivery systems and to increase the immunogenicity and stability of a given antigen. This work aims to characterize and validate the potential of a vaccine formulation composed of domain zEDIII and bovine serum albumin nanoparticles containing polyinosinic-polycytidylic acid (NPPI). NPPI were uptake in vitro by immature bone marrow dendritic cells and histological analysis of the skin of mice treated with NPPI showed an increase in cellularity. Immunization assay showed that mice immunized with zEDIII in the presence of NPPI produced neutralizing antibodies. Through the passive transfer of sera from immunized mice to ZIKV-infected neonatal mice, it was demonstrated that these antibodies provide protection, mitigating weight loss, clinical or neurological signs induced by infection, and significantly increased survival rates. Protection was further substantiated by the reduction in the number of viable infectious ZIKV, as well as a decrease in inflammatory cytokines and tissue alterations in the brains of infected mice. Taken together, data presented in this study shows that NPPI + zEDIII is a promising vaccine candidate for ZIKV.

DNA Vaccines: History, Molecular Mechanisms and Future Perspectives

The history of DNA vaccine began as early as the 1960s with the discovery that naked DNA can transfect mammalian cells in vivo. In 1992, the evidence that such transfection could lead to the generation of antigen-specific antibody responses was obtained and supported the development of this technology as a novel vaccine platform. The technology then attracted immense interest and high hopes in vaccinology, as evidence of high immunogenicity and protection against virulent challenges accumulated from several animal models for several diseases. In particular, the capacity to induce T-cell responses was unprecedented in non-live vaccines. However, the technology suffered its major knock when the success in animals failed to translate to humans, where DNA vaccine candidates were shown to be safe but remained poorly immunogenic, or not associated with clinical benefit. Thanks to a thorough exploration of the molecular mechanisms of action of these vaccines, an impressive range of approaches have been and are currently being explored to overcome this major challenge. Despite limited success so far in humans as compared with later genetic vaccine technologies such as viral vectors and mRNA, DNA vaccines are not yet optimised for human use and may still realise their potential.

Potential of an anti-bevacizumab idiotype scFv DNA-based immunization to elicit VEGF-binding antibody response

Anti-idiotype antibodies have been considered for vaccination approaches against different diseases, including cancers. Based on that, we previously described an anti-bevacizumab idiotype monoclonal antibody, 10.D7, that revealed detectable antitumor effects on a vascular endothelial growth factor (VEGF)-dependent tumor model. Herein, we evaluated the possible applicability of a single-chain variable fragment (scFv) for the 10.D7 antibody in a gene immunization strategy. After checking that mammalian cells transfected to express the 10.D7 scFv are recognized by bevacizumab, it was explored the ability of our scFv construction, in a gene-based scheme, to elicit an immune response containing VEGF-binding antibodies. The results provide evidence that the designed 10.D7 scFv construct maintains the anti-bevacizumab idiotype features and has potential to activate an immune response recognizing VEGF.

Mechanisms of ag85a/b DNA vaccine conferred immunotherapy and recovery from Mycobacterium tuberculosis-induced injury

Our previous research developed a novel tuberculosis (TB) DNA vaccine ag85a/b that showed a significant therapeutic effect on the mouse tuberculosis model by intramuscular injection (IM) and electroporation (EP). However, the action mechanisms between these two vaccine immunization methods remain unclear. In a previous study, 96 Mycobacterium tuberculosis (MTB) H37 Rv-infected BALB/c mice were treated with phosphate-buffered saline, 10, 50, 100, and 200 μg ag85a/b DNA vaccine delivered by IM and EP three times at 2-week intervals, respectively. In this study, peripheral blood mononuclear cells (PBMCs) from three mice in each group were isolated to extract total RNA. The gene expression profiles were analyzed using gene microarray technology to obtain differentially expressed (DE) genes. Finally, DE genes were validated by real-time reverse transcription-quantitive polymerase chain reaction and the GEO database. After MTB infection, most of the upregulated DE genes were related to the digestion and absorption of nutrients or neuroendocrine (such as Iapp, Scg2, Chga, Amy2a5), and most of the downregulated DE genes were related to cellular structural and functional proteins, especially the structure and function proteins of the alveolar epithelial cell (such as Sftpc, Sftpd, Pdpn). Most of the abnormally upregulated or downregulated DE genes in the TB model group were recovered in the 100 and 200 μg ag85a/b DNA IM groups and four DNA EP groups. The pancreatic secretion pathway downregulated and the Rap1 signal pathway upregulated had particularly significant changes during the immunotherapy of the ag85a/b DNA vaccine on the mouse TB model. The action targets and mechanisms of IM and EP are highly consistent. Tuberculosis infection causes rapid catabolism and slow anabolism in mice. For the first time, we found that the effective dose of the ag85a/b DNA vaccine immunized whether by IM or EP could significantly up-regulate immune-related pathways and recover the metabolic disorder and the injury caused by MTB.

Current Advances in Zika Vaccine Development

Zika virus (ZIKV), an emerging arthropod-borne flavivirus, was first isolated in Uganda in 1947 from monkeys and first detected in humans in Nigeria in 1952; it has been associated with a dramatic burden worldwide. Since then, interventions to reduce the burden of ZIKV infection have been mainly restricted to mosquito control, which in the end proved to be insufficient by itself. Hence, the situation prompted scientists to increase research on antivirals and vaccines against the virus. These efforts are still ongoing as the pathogenesis and immune evasion mechanisms of ZIKV have not yet been fully elucidated. Understanding the viral disease mechanism will provide a better landscape to develop prophylactic and therapeutic strategies against ZIKV. Currently, no specific vaccines or drugs have been approved for ZIKV. However, some are undergoing clinical trials. Notably, different platforms have been evaluated for the design of vaccines, including DNA, mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, peptide and protein-based vaccines, passive immunizations by using monoclonal antibodies (MAbs), and vaccines that target vector-derived antigens. These vaccines have been shown to induce specific humoral and cellular immune responses and reduce viremia and viral RNA titers, both in vitro and in vivo. This review provides a comprehensive summary of current advancements in the development of vaccines against Zika virus.