Non-replicative antibiotic resistance-free DNA vaccine encoding S and N proteins induces full protection in mice against SARS-CoV-2

DNA Vaccines: Their Formulations, Engineering and Delivery

The concept of DNA vaccination was introduced in the early 1990s. Since then, advancements in the augmentation of the immunogenicity of DNA vaccines have brought this technology to the market, especially in veterinary medicine, to prevent many diseases. Along with the successful COVID mRNA vaccines, the first DNA vaccine for human use, the Indian ZyCovD vaccine against SARS-CoV-2, was approved in 2021. In the current review, we first give an overview of the DNA vaccine focusing on the science, including adjuvants and delivery methods. We then cover some of the emerging science in the field of DNA vaccines, notably efforts to optimize delivery systems, better engineer delivery apparatuses, identify optimal delivery sites, personalize cancer immunotherapy through DNA vaccination, enhance adjuvant science through gene adjuvants, enhance off-target and heritable immunity through epigenetic modification, and predict epitopes with bioinformatic approaches. We also discuss the major limitations of DNA vaccines and we aim to address many theoretical concerns.

Intranasal inoculation of female BALB/c mice with replication-deficient human adenovirus type 5 expressing SARS-CoV-2 nucleocapsid protein aggravates lung pathology upon re-encountering the antigen

Preclinical studies indicate that SARS-CoV-2 nucleocapsid (N)-based vaccines, along with other viral protein(s), confer protection in various animal models against infection by SARS-CoV-2 ancestral virus and variants of concern. However, the optimal vaccination procedure and the role of N-specific host adaptive immune responses remain elusive. Here, we report that intranasal inoculation with replication-deficient human adenovirus type 5 expressing SARS-CoV-2 N protein (Ad5-N) conferred no protection in the lung of female BALB/c mice upon re-encountering the antigen, either by 10-fold Ad5-N re-exposure or sublethal infection of mouse-adapted SARS-CoV-2. By contrast, this procedure led to aggravated lung pathology with more necroptotic CD3+ T cells and Ly6G+ granulocytes, which was associated with the accumulation of IFN-γ-expressing antigen-experienced CD4+ and CD8+ T cells. These findings pre-caution the clinical application of this vaccination procedure. Furthermore, our data suggest that excessive host adaptive immune responses against N protein contributes to COVID-19 pathogenesis.

A non-replicative antibiotic resistance-free DNA vaccine delivered by the intranasal route protects against canine leishmaniasis

Leishmania infantum is the etiological agent of zoonotic visceral leishmaniasis (ZVL). The disease is endemic in Central and South America, Central and South East Asia, and the Mediterranean basin. Dogs are the main reservoir, with an estimated prevalence of approximately 2.5 million dogs in Southern Europe. Current treatments cause side effects, disease recurrence, and drug resistance. Therefore, the development of vaccines against canine leishmaniasis is necessary. We have generated a DNA vaccine based on the non-replicative antibiotic resistance marker-free plasmid vector pPAL that contains the encoding gene for the L. infantum activated protein kinase C receptor analog (LACK). Homologous pPAL-LACK prime-boost intranasal administration confers efficacious protection in Beagle dogs with a reduction of clinical signs and a statistically significant reduction of the parasite burden in the bone marrow of more than 90% of dogs after experimental infection with highly infective promastigotes. This DNA vaccine elicits a robust cellular immune response skewed towards the Th1 profile.

An Overview of the Use of Nanoparticles in Vaccine Development

Vaccines represent one of the most significant advancements in public health since they prevented morbidity and mortality in millions of people every year. Conventionally, vaccine technology focused on either live attenuated or inactivated vaccines. However, the application of nanotechnology to vaccine development revolutionized the field. Nanoparticles emerged in both academia and the pharmaceutical industry as promising vectors to develop future vaccines. Regardless of the striking development of nanoparticles vaccines research and the variety of conceptually and structurally different formulations proposed, only a few of them advanced to clinical investigation and usage in the clinic so far. This review covered some of the most important developments of nanotechnology applied to vaccine technologies in the last few years, focusing on the successful race for the preparation of lipid nanoparticles employed in the successful anti-SARS-CoV-2 vaccines.