Exosome-Mediated mRNA Delivery For SARS-CoV-2 Vaccination

Abstract

Background: In less than a year from its zoonotic entry into the human population, SARS-CoV-2 has infected more than 45 million people, caused 1.2 million deaths, and induced widespread societal disruption. Leading SARS-CoV-2 vaccine candidates immunize with the viral spike protein delivered on viral vectors, encoded by injected mRNAs, or as purified protein. Here we describe a different approach to SARS-CoV-2 vaccine development that uses exosomes to deliver mRNAs that encode antigens from multiple SARS-CoV-2 structural proteins. Approach: Exosomes were purified and loaded with mRNAs designed to express (i) an artificial fusion protein, LSNME, that contains portions of the viral spike, nucleocapsid, membrane, and envelope proteins, and (ii) a functional form of spike. The resulting combinatorial vaccine, LSNME/SW1, was injected into thirteen weeks-old, male C57BL/6J mice, followed by interrogation of humoral and cellular immune responses to the SARS-CoV-2 nucleocapsid and spike proteins, as well as hematological and histological analysis to interrogate animals for possible adverse effects. Results: Immunized mice developed CD4+, and CD8+ T-cell reactivities that respond to both the SARS-CoV-2 nucelocapsid protein and the SARS-CoV-2 spike protein. These responses were apparent nearly two months after the conclusion of vaccination, as expected for a durable response to vaccination. In addition, the spike-reactive CD4+ T-cells response was associated with elevated expression of interferon gamma, indicative of a Th1 response, and a lesser induction of interleukin 4, a Th2-associated cytokine. Vaccinated mice showed no sign of altered growth, injection-site hypersensitivity, change in white blood cell profiles, or alterations in organ morphology. Consistent with these results, we also detected moderate but sustained anti-nucleocapsid and anti-spike antibodies in the plasma of vaccinated animals. Conclusion: Taken together, these results validate the use of exosomes for delivering functional mRNAs into target cells in vitro and in vivo, and more specifically, establish that the LSNME/SW1 vaccine induced broad immunity to multiple SARS-CoV-2 proteins.

Promising Extracellular Vesicle-Based Vaccines against Viruses, Including SARS-CoV-2

“…The second type is an mRNA vaccine formulated by EVs loaded with five different mRNAs coding for modified SARS-CoV-2 Spike, Nucleocapsid, Membrane, and Envelope proteins (LSNME) and for the full-length Spike of Wuhan-1 isolate (S W1 ). In November 2020, Capricor and Johns Hopkins University researchers published, as a pre-print version, encouraging results of pre-clinical trials for their multivalent EV-based mRNA vaccine [ 60 ]. They have combined the EV-based mRNA delivery and viral antigen expression compatible for antigen presentation by MHC Class I and II molecules.…”

Ancient Evolutionary Origin and Properties of Universally Produced Natural Exosomes Contribute to Their Therapeutic Superiority Compared to Artificial Nanoparticles

“…One can generate exosomes that are mini-APCs (antigen-presenting cells) to act as strong vaccines that are useful against cancers [ 262 , 263 , 264 ] and infections [ 265 , 266 ]—particularly against SARS coronavirus [ 267 ] and now COVID-19 mediating SARS-2 [ 268 ]. Such mini-APCs can be derived from dendritic cells exposed to whole antigens or dendritic cell-derived exosomes pulsed with specific Ag peptides to enable the development of immunogenic specific peptide/MHC surface complexes.…”

“…In COVID-19, therapy with MSCs and convalescent plasma must consider exosome involvement, with the suggestion that exosomes in convalescent plasma antagonize the weak immune antibodies [ 27 ]. Capricor Therapeutics, together with Johns Hopkins University, have announced positive preclinical data for a multivalent exosome-mRNA nanoparticle vaccine [ 268 ].…”

The Role of Exosomes in the Treatment, Prevention, Diagnosis, and Pathogenesis of COVID-19

“…78 Moreover, a more recent study showed that exosomes derived from a human cell line (293-F cells) can be loaded with mRNAs encoding the viral spike, nucleocapsid, membrane, and envelope proteins, and when injected in in vitro and in vivo models, conferred immunity against the multiple SARS-CoV-2 proteins. 79 Currently, there are five COVID-19 exosome-based vaccines developed by four biotechnology and pharmaceutical companies that are undergoing further study (►Table 2). [79][80][81][82][83] The pandemic has opened up avenues for these new types of vaccines which could be a promising strategy for the prevention against COVID-19, as well as for other infectious diseases in the future.…”

“…79 Currently, there are five COVID-19 exosome-based vaccines developed by four biotechnology and pharmaceutical companies that are undergoing further study (►Table 2). [79][80][81][82][83] The pandemic has opened up avenues for these new types of vaccines which could be a promising strategy for the prevention against COVID-19, as well as for other infectious diseases in the future.…”