Immune response enhancement with GLS-5310 DNA primary vaccine against SARS-CoV-2 followed by administration of an mRNA vaccine heterologous boost.

• Heterologous mRNA boost following GLS-5310 DNA vaccination was well tolerated. • Neutralizing antibody responses were enhanced 110 fold to GMT of 1244.8. • Binding antibody responses were enhanced 1,187-fold to GMT of 405,920. • Boosted antibody responses similar to other vaccine combinations. • Boosted T cell responses were many-fold higher than other vaccine combinations. Heterologous boost regimens are being increasingly considered against SARS-CoV-2. We report results for the 32 of 45 participants in the Phase 1 CoV2-001 clinical trial (Kim et al., Int J Iinfect Dis 2023, 128:112–120) who elected to receive an EUA-approved SARS-CoV-2 mRNA vaccine 6 to 8 months following a two-dose primary vaccination with the GLS-5310 bi-cistronic DNA vaccine given intradermally and followed by application of suction using the GeneDerm device. Receipt of EUA-approved mRNA vaccines after GLS-5310 vaccination was well-tolerated, with no reported adverse events. Immune responses were enhanced such that binding antibody titers, neutralizing antibody titers, and T-cell responses increased 1,187-fold, 110-fold, and 2.9-fold, respectively. This paper is the first description of the immune responses following heterologous vaccination with a DNA primary series and mRNA boost. [ABSTRACT FROM AUTHOR]