Abstract
The first vaccines ever made were based on live-attenuated or inactivated pathogens, either whole cells or fragments. Although these vaccines required the co-administration of antigens with adjuvants to induce a strong humoral response, they could only elicit a poor CD8+ T-cell response. In contrast, next-generation nano/microparticle-based vaccines offer several advantages over traditional ones because they can induce a more potent CD8+ T-cell response and, at the same time, are ideal carriers for proteins, adjuvants, and nucleic acids. The fact that these nanocarriers can be loaded with molecules able to modulate the immune response by inducing different effector functions and regulatory activities makes them ideal tools for inverse vaccination, whose goal is to shut down the immune response in autoimmune diseases. Poly (lactic-co-glycolic acid) (PLGA) and liposomes are biocompatible materials approved by the Food and Drug Administration (FDA) for clinical use and are, therefore, suitable for nanoparticle-based vaccines. Recently, another candidate platform for innovative vaccines based on extracellular vesicles (EVs) has been shown to efficiently co-deliver antigens and adjuvants. This review will discuss the potential use of PLGA-NPs, liposomes, and EVs as carriers of peptides, adjuvants, mRNA, and DNA for the development of next-generation vaccines against endemic and emerging viruses in light of the recent COVID-19 pandemic.
Highlights
Vertebrates have developed defense mechanisms consisting of innate and adaptive immunity [1] that collaborate to build an effective immune response against microbial invaders
Next-generation nano/microparticle-based vaccines offer several advantages over traditional ones because they can induce a more potent CD8+ T-cell response and, at the same time, are ideal carriers for proteins, adjuvants, and nucleic acids. The fact that these nanocarriers can be loaded with molecules able to modulate the immune response by inducing different effector functions and regulatory activities makes them ideal tools for inverse vaccination, whose goal is to shut down the immune response in autoimmune diseases
Classical vaccines were invented by Louis Pasteur in the late 1800s, following from the initial observation made by Edward Jenner about one century earlier that cowpox infection induced an immune condition that protected from smallpox infection, devising a new procedure nowadays known as vaccination—a term derived from the Latin word for cow “vacca” [9]
Summary
Vertebrates have developed defense mechanisms consisting of innate and adaptive immunity [1] that collaborate to build an effective immune response against microbial invaders. Upon PAMP recognition, the host defense mechanism is activated, resulting in acute inflammation, crucial to recruiting immune cells to the site of infection [3], and activate adaptive immunity. Cellular immune responses mediated by CD4+ T helper (TH) cells and CD8+ cytotoxic T lymphocytes (CTLs) are crucial for host defense. CTLs recognize virus-infected cells and induce their apoptosis in order to clear the invading pathogens [6]. Besides eliciting an effector response that eradicates the infection, these processes contribute to the development of an immunological memory that can trigger an effective response when the same pathogen is encountered a second time [7].
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