The coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is associated with several fatal cases worldwide. The rapid spread of this pathogen and the increasing number of cases highlight the urgent development of vaccines. Among the technologies available for vaccine development, DNA vaccination is a promising alternative to conventional vaccines. Since its discovery in the 1990s, it has been of great interest because of its ability to elicit both humoral and cellular immune responses while showing relevant advantages regarding producibility, stability, and storage. This review aimed to summarize the current knowledge and advancements on DNA vaccines against COVID-19, particularly those in clinical trials.

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The novel betacoronavirus SARS-CoV-2 causes a form of severe pneumonia disease, termed COVID-19. To develop human neutralizing anti-SARS-CoV-2 antibodies, antibody gene libraries from convalescent COVID-19 patients were constructed and recombinant antibody fragments (scFv) against the receptor binding domain (RBD) of the spike protein were selected by phage display. The antibody STE90-C11 shows a sub nM IC50 in a plaque-based live SARS-CoV-2 neutralization assay. The in vivo efficacy of the antibody is demonstrated in the Syrian hamster and in the hACE2 mice model. The crystal structure of STE90-C11 Fab in complex with SARS-CoV-2-RBD is solved at 2.0 Å resolution showing that the antibody binds at the same region as ACE2 to RBD. The binding and inhibition of STE90-C11 is not blocked by many known emerging RBD mutations. STE90-C11 derived human IgG1 with FcγR silenced Fc (COR-101) is currently undergoing Phase Ib/II clinical trials for the treatment of moderate to severe COVID-19.

Clostridium perfringens is an anaerobic bacterium that produces several toxins. Of these, the alpha, beta, and epsilon toxins are responsible for causing the most severe C. perfringens-related diseases in farm animals. The best way to control these diseases is through vaccination. However, commercially available vaccines are based on inactivated toxins and have many production drawbacks, which can be overcome through the use of recombinant antigens. In this study, we produced recombinant alpha, beta, and epsilon toxins in Escherichia coli to formulate a trivalent vaccine. Its effectiveness was evaluated through a potency test in rabbits, in which the vaccine generated 9.6, 24.4, and 25.0 IU/mL of neutralizing antibodies against the respective toxins. Following this, cattle, sheep, and goats received the same formulation, generating, respectively, 5.19 ± 0.48, 4.34 ± 0.43, and 4.70 ± 0.58 IU/mL against alpha toxin, 13.71 ± 1.17 IU/mL (for all three species) against beta toxin, and 12.74 ± 1.70, 7.66 ± 1.69, and 8.91 ± 2.14 IU/mL against epsilon toxin. These levels were above the minimum recommended by international protocols. As such, our vaccine was effective in generating protective antibodies and, thus, may represent an interesting alternative for the prevention of C. perfringens-related intoxications in farm animals.