Abstract
Effective vaccine development for global outbreaks, such as the coronavirus disease 2019 (COVID-19), has been successful in the short run. However, the currently available vaccines have been associated with a higher frequency of adverse effects compared with other general vaccines. In this study, the possibility of an oral bacteria-based vaccine that can be safely used as a platform for large-scale, long-term immunization was evaluated. A well-known Salmonella strain that was previously considered as a vaccine delivery candidate was used. Recombinant Salmonella cells expressing engineered viral proteins related with COVID-19 pathogenesis were engineered, and the formulation of the oral vaccine candidate strain was evaluated by in vitro and in vivo experiments. First, engineered S proteins were synthesized and cloned into expression vectors, which were than transformed into Salmonella cells. In addition, when orally administrated to mice, the vaccine promoted antigen-specific antibody production and cellular immunity was induced with no significant toxicity effects. These results suggest that Salmonella strains may represent a valuable platform for the development of an oral vaccine for COVID-19 as an alternative to tackle the outbreak of various mutated coronavirus strains and new infectious diseases in the future.
Highlights
The global outbreak of the coronavirus disease 2019 (COVID-19) has increased the need for rapid vaccine development [1,2,3,4]
Since the COVID-19 outbreak, which is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), several vaccines have been developed through various platforms, including live-attenuated and inactivated vaccines, protein subunit and vector-based vaccines, and nucleic acid and nano-material-based vaccines [5,6]
Despite the significant efforts made, researchers are still trying to find effective vaccine candidates to block the expansion of the coronavirus, suggesting that the currently available vaccines are not the best
Summary
The global outbreak of the coronavirus disease 2019 (COVID-19) has increased the need for rapid vaccine development [1,2,3,4]. There are public concerns about the incidence of anaphylaxis, thrombosis with thrombocytopenia syndrome (TTS), Guillain–Barré syndrome, myocarditis, and pericarditis associated with these RNA- and virus-based vaccines [10], which are mainly due to the excessive activity of the immune system in response to the injection of excessive amounts of inflammatory substances directly into the body. Despite these negative aspects of the currently available COVID-19 vaccines, they are indispensable for managing and controlling the ongoing global pandemic. Bacterial-based orally administered vaccines have attracted attention as a safer vaccine technology compared with vascular or intramuscular injection approaches, and are a rapid vaccine development platform for new infectious diseases such as COVID-19
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