Amphiphilic block copolymer delivery of a DNA vaccine against Zika virus

RNA Vaccines: Yeast as a Novel Antigen Vehicle

In the last decades, technological advances for RNA manipulation enabled and expanded its application in vaccine development. This approach comprises synthetic single-stranded mRNA molecules that direct the translation of the antigen responsible for activating the desired immune response. The success of RNA vaccines depends on the delivery vehicle. Among the systems, yeasts emerge as a new approach, already employed to deliver protein antigens, with efficacy demonstrated through preclinical and clinical trials. β-glucans and mannans in their walls are responsible for the adjuvant property of this system. Yeast β-glucan capsules, microparticles, and nanoparticles can modulate immune responses and have a high capacity to carry nucleic acids, with bioavailability upon oral immunization and targeting to receptors present in antigen-presenting cells (APCs). In addition, yeasts are suitable vehicles for the protection and specific delivery of therapeutic vaccines based on RNAi. Compared to protein antigens, the use of yeast for DNA or RNA vaccine delivery is less established and has fewer studies, most of them in the preclinical phase. Here, we present an overview of the attributes of yeast or its derivatives for the delivery of RNA-based vaccines, discussing the current challenges and prospects of this promising strategy.

704/DNA vaccines leverage cytoplasmic DNA stimulation to promote anti-HIV neutralizing antibody production in mice and strong immune response against alpha-fetoprotein in non-human primates

Genetic immunization is an attractive approach for prophylactic and therapeutic vaccination using synthetic vectors to deliver antigen-encoding nucleic acids. Recently, DNA delivered by a physical means or RNA by liposomes consisting of four different lipids demonstrated good protection in human phase III clinical trials and received Drugs Controller General of India and US FDA approval to protect against COVID-19, respectively. However, the development of a system allowing for efficient and simple delivery of nucleic acids while improving immune response priming has the potential to unleash the full therapeutic potential of genetic immunization. DNA-based gene therapies and vaccines have the potential for rapid development, as exemplified by the recent approval of Collategene, a gene therapy to treat human critical limb ischemia, and ZyCoV, a DNA vaccine delivered by spring-powered jet injector to protect against SARS-CoV2 infection. Recently, we reported amphiphilic block copolymer 704 as a promising synthetic vector for DNA vaccination in various models of human diseases. This vector allows dose sparing of antigen-encoding plasmid DNA. Here, we report the capacity of 704-mediated HIV and anti-hepatocellular carcinoma DNA vaccines to induce the production of specific antibodies against gp120 HIV envelope proteins in mice and against alpha-fetoprotein antigen in non-human primates, respectively. An investigation of the underlying mechanisms showed that 704-mediated vaccination did trigger a strong immune response by (1) allowing a direct DNA delivery into the cytosol, (2) promoting an intracytoplasmic DNA sensing leading to both interferon and NF-κB cascade stimulation, and (3) inducing antigen expression by muscle cells and presentation by antigen-presenting cells, leading to the induction of a robust adaptive response. Overall, our findings suggest that the 704-mediated DNA vaccination platform is an attractive method to develop both prophylactic and therapeutic vaccines.

A method for mapping the linear epitopes targeted by the natural antibody response to Zika virus infection using a VLP platform technology

Zika virus (ZIKV), a mosquito-borne pathogen, is associated with neurological complications in adults and congenital abnormalities in newborns. There are no vaccines or treatments for ZIKV infection. Understanding the specificity of natural antibody responses to ZIKV could help inform vaccine efforts. Here, we used a technology called Deep Sequence-Coupled Biopanning to map the targets of the human antibody responses to ZIKV infection. A bacteriophage virus-like particle (VLP) library displaying overlapping linear peptides derived from the ZIKV polyprotein was generated. The library was panned using IgG from 23 ZIKV-infected patients from Panama and deep sequencing identified common targets of anti-ZIKV antibodies within the ZIKV envelope glycoprotein. These included epitopes within the fusion loop within domain II and four epitopes within domain III. Additionally, we showed that VLPs displaying selected epitopes elicited antibodies that bound to native ZIKV envelope protein but failed to prevent infection in a mouse challenge model.

ZIKV: Epidemiology, infection mechanism and current therapeutics

The Zika virus (ZIKV) is a vector-borne flavivirus that has been detected in 87 countries worldwide. Outbreaks of ZIKV infection have been reported from various places around the world and the disease has been declared a public health emergency of international concern. ZIKV has two modes of transmission: vector and non-vector. The ability of ZIKV to vertically transmit in its competent vectors, such as Aedes aegypti and Aedes albopictus, helps it to cope with adverse conditions, and this could be the reason for the major outbreaks that occur from time to time. ZIKV outbreaks are a global threat and, therefore, there is a need for safe and effective drugs and vaccines to fight the virus. In more than 80% of cases, ZIKV infection is asymptomatic and leads to complications, such as microcephaly in newborns and Guillain–Barré syndrome (GBS) in adults. Drugs such as sofosbuvir, chloroquine, and suramin have been found to be effective against ZIKV infections, but further evaluation of their safety in pregnant women is needed. Although temoporfin can be given to pregnant women, it needs to be tested further for side effects. Many vaccine types based on protein, vector, DNA, and mRNA have been formulated. Some vaccines, such as mRNA-1325 and VRC-ZKADNA090-00-VP, have reached Phase II clinical trials. Some new techniques should be used for formulating and testing the efficacy of vaccines. Although there have been no recent outbreaks of ZIKV infection, several studies have shown continuous circulation of ZIKV in mosquito vectors, and there is a risk of re-emergence of ZIKV in the near future. Therefore, vaccines and drugs for ZIKV should be tested further, and safe and effective therapeutic techniques should be licensed for use during outbreaks.

Enhancing the Effect of Nucleic Acid Vaccines in the Treatment of HPV-Related Cancers: An Overview of Delivery Systems

Prophylactic vaccines against human papillomavirus (HPV) have proven efficacy in those who have not been infected by the virus. However, they do not benefit patients with established tumors. Therefore, the development of therapeutic options for HPV-related malignancies is critical. Third-generation vaccines based on nucleic acids are fast and simple approaches to eliciting adaptive immune responses. However, techniques to boost immunogenicity, reduce degradation, and facilitate their capture by immune cells are frequently required. One option to overcome this constraint is to employ delivery systems that allow selective antigen absorption and help modulate the immune response. This review aimed to discuss the influence of these different systems on the response generated by nucleic acid vaccines. The results indicate that delivery systems based on lipids, polymers, and microorganisms such as yeasts can be used to ensure the stability and transport of nucleic acid vaccines to their respective protein synthesis compartments. Thus, in view of the limitations of nucleic acid-based vaccines, it is important to consider the type of delivery system to be used-due to its impact on the immune response and desired final effect.

Current Progress in the Development of Zika Virus Vaccines

Zika virus (ZIKV) is an arbovirus first discovered in the Americas. ZIKV infection is insidious based on its mild clinical symptoms observed after infection. In Brazil, after 2015, ZIKV infection broke out on a large scale, and many infected pregnant women gave birth to babies with microcephaly. The teratogenic effects of the virus on the fetus and its effects on nerves and the immune system have attracted great attention. Currently, no specific prophylactics or therapeutics are clinically available to treat ZIKV infection. Development of a safe and effective vaccine is essential to prevent the rise of any potential pandemic. In this review, we summarize the latest research on Zika vaccine development based on different strategies, including DNA vaccines, subunit vaccines, live-attenuated vaccines, virus-vector-based vaccines, inactivated vaccines, virus-like particles (VLPs), mRNA-based vaccines, and others. We anticipate that this review will facilitate further progress toward the development of effective and safe vaccines against ZIKV infection.

Optimization of Zika DNA vaccine by delivery systems

In our previous study, we designed and evaluated the efficacy of six DNA vaccine candidates based on the E protein of Zika virus (ZIKV). To optimize the DNA vaccine, we inoculated C57BL/6 and IFNAR1^- mice with the vaccine candidate expressing tandem repeated ZIKV envelope domain III (ED III × 3) doses; 50 μg by intramuscular (IM), jet injection (JET), or electroporation (EP) routes. Results showed that vaccination by all routes induced humoral and cellular immunity. Among them, EP induced robust ZIKV E specific-total IgG and neutralizing antibodies, as well as T cell responses. Additionally, EP showed superior protective efficacy against the ZIKV Brazil strain compared to the IM and JET routes. Finally, in the dose optimization test of EP route, cellular immunity of 50 μg was induced a significant level than other dose groups. These results showed that the EP delivery system enhanced the potential immunogenicity and protective efficacy of DNA vaccines.

Advances in vaccine delivery systems against viral infectious diseases

Although vaccines are available for many infectious diseases, there are still unresolved infectious diseases that threaten global public health. In particular, the rapid spread of unpredictable, highly contagious viruses has recorded numerous infection cases and deaths, and has changed our lives socially or economically through social distancing and wearing masks. The pandemics of unpredictable, highly contagious viruses increase the ever-high social need for rapid vaccine development. Nanotechnologies may hold promise and expedite the development of vaccines against newly emerging infectious viruses. As potential nanoplatforms for delivering antigens to immune cells, delivery systems based on lipids, polymers, proteins, and inorganic nanomaterials have been studied. These nanoplatforms have been tested as a means to deliver vaccines not as a whole, but in the form of protein subunits or as DNA or mRNA sequences encoding the antigen proteins of viruses. This review covers the current status of nanomaterial-based delivery systems for viral antigens, with highlights on nanovaccines against recently emerging infectious viruses, such as severe acute respiratory syndrome coronavirus-2, Middle East respiratory syndrome coronavirus, and Zika virus.

Gene delivery for immunoengineering

A growing number of gene delivery strategies are being employed for immunoengineering in applications ranging from infectious disease prevention to cancer therapy. Viral vectors tend to have high gene transfer capability but may be hampered by complications related to their intrinsic immunogenicity. Non-viral methods of gene delivery, including polymeric, lipid-based, and inorganic nanoparticles as well as physical delivery techniques, have also been widely investigated. By using either ex vivo engineering of immune cells that are subsequently adoptively transferred or in vivo transfection of cells for in situ genetic programming, researchers have developed different approaches to precisely modulate immune responses. In addition to expressing a gene of interest through intracellular delivery of plasmid DNA and mRNA, researchers are also delivering oligonucleotides to knock down gene expression and immunostimulatory nucleic acids to tune immune activity. Many of these biotechnologies are now in clinical trials and have high potential to impact medicine.

Recent Advances in the Development of Virus-Like Particle-Based Flavivirus Vaccines

Flaviviruses include several medically important viruses, such as Zika virus (ZIKV), Dengue virus (DENV), West Nile virus (WNV) and Japanese encephalitis virus (JEV). They have expanded in geographic distribution and refocused international attention in recent years. Vaccination is one of the most effective public health strategies for combating flavivirus infections. In this review, we summarized virus-like particle (VLP)-based vaccines against the above four mentioned flaviviruses. Potential strategies to improve the efficacy of VLP-based flavivirus vaccines were also illustrated. The applications of flavivirus VLPs as tools for viral detection and antiviral drug screening were finally proposed.

Enhanced effect of modified Zika virus E antigen on the immunogenicity of DNA vaccine

It has been reported worldwide that the Zika virus (ZIKV) could be transmitted through placentas and sexual contact. ZIKV can also cause Guillain-Barre syndrome, microcephaly and neurological abnormalities. However, there are no approved vaccines available. We constructed six DNA vaccine candidates and tested the immunogenicity. Tandem repeated envelope domain Ⅲ (ED Ⅲ × 3) induced highly total IgG and neutralization antibody, as well as CD8⁺ T cell responses. Also, stem region-removed envelope (E ΔSTEM) elicited a robust production of IFN-γ in mice. To examine in vivo protection, we used mice treated with an IFNAR1 blocking antibody before and after the challenge. Vaccination with the two candidates led to a decline in the level of viral RNAs in organs. Moreover, the sera from the vaccinated mice did not enhance the infection of Dengue virus in K562 cells. These findings suggest the potential for the development of a novel ZIKV DNA vaccine.

Investigation of the immunogenicity of Zika glycan loop

Background

Zika virus (ZIKV) is a major human pathogen and member of the Flavivirus genus. Previous studies have identified neutralizing antibodies from Zika patients that bind to quaternary epitopes across neighboring envelope (E) proteins, called E dimer epitopes (EDE). An asparagine-linked glycan on the “glycan loop” (GL) of the ZIKV envelope protein protects the functionally important “fusion loop” on the opposite E subunit in the dimer, and EDE antibodies have been shown to bind to both of these loops. Human EDE antibodies have been divided into two subclasses based on how they bind to the glycan loop region: EDE1 antibodies do not require glycosylation for binding, while EDE2 antibodies strongly rely on the glycan for binding.

Methods

ZIKV GL was expressed on tobacco mosaic virus nanoparticles. Mice were immunized with GL or full-length monomeric E and the immune response was analyzed by testing the ability of sera and monoclonal antibodies to bind to GL and to neutralize ZIKV in in vitro cellular assay.

Results

We report here the existence of ZIKV moderately neutralizing antibodies that bind to E monomers through epitopes that include the glycan loop. We show that sera from human Zika patients contain antibodies capable of binding to the unglycosylated glycan loop in the absence of the rest of the envelope protein. Furthermore, mice were inoculated with recombinant E monomers and produced neutralizing antibodies that either recognize unglycosylated glycan loop or require glycan for their binding to monomeric E. We demonstrate that both types of antibodies neutralize ZIKV to some extent in a cellular virus neutralization assay.

Conclusions

Analogous to the existing EDE antibody nomenclature, we propose a new classification for antibodies that bind to E monomer epitopes (EME): EME1 and EME2 for those that do not require and those that do require glycan for binding to E, respectively.

Zika virus: A possible emerging threat for Bangladesh!

Zika virus, a member of Flaviviridae is the etiology of Zika or Zika fever or Zika virus (ZIKV) disease characterized by mild symptoms similar to very mild form of Dengue or Chikungunya. The virus transmits through Aedes mosquitoes, particularly by Aedes aegypti. The most dangerous effect of ZIKV infection is the ability of the virus to cause microcephaly and congenital malformation to the newborn baby if the mother is infected. The neurological disorders including Guillain-Barré syndrome might be associated with adults and children due to ZIKV infections. Zika has emerged as a serious global public health problem as it has been found in 87 countries, particularly in Africa, America, and Asia and has no vaccine and treatment so far. Bangladesh is at a high risk of ZIKV infection and we consider ZIKV as a possible emerging threat for Bangladesh. This short review summarizes the insights of ZIKV infection, present status of the disease in Bangladesh and its neighboring countries, and recommendations for necessary preparations and strategies to be taken for effective controlling of the ZIKV infection in Bangladesh before getting any havoc.

Tetrafunctional Block Copolymers Promote Lung Gene Transfer in Newborn Piglets

Tetrafunctional block copolymers are molecules capable of complexing DNA. Although ineffective in vitro, studies in mice have shown that the tetrafunctional block copolymer 704 is a more efficient lung gene transfer agent than the cationic liposome GL67A, previously used in a phase II clinical trial in cystic fibrosis patients. In the present study, we compared the gene transfer capacity of the 704-DNA formulation and a cationic liposome-DNA formulation equivalent to GL67A in a larger-animal model, the newborn piglet. Our results indicate an efficacy of the 704-DNA formulation well above one order of magnitude higher than that of the cationic liposome-DNA formulation, with no elevated levels of interleukin-6 (IL-6), taken as a marker of inflammation. Transgene expression was heterogeneous within lung lobes, with expression levels that were below the detection threshold in some samples, while high in other samples. This heterogeneity is likely to be due to the bolus injection procedure as well as to the small volume of injection. The present study highlights the potential of tetrafunctional block copolymers as non-viral vectors for lung gene therapy.