Abstract
We have developed a COVID-19 vaccine, hAd5 S-Fusion + N-ETSD, that expresses SARS-CoV-2 spike (S) and nucleocapsid (N) proteins with modifications to increase immune responses delivered using a human adenovirus serotype 5 (hAd5) platform. Here, we demonstrate subcutaneous (SC) prime and SC boost vaccination of CD-1 mice with this dual-antigen vaccine elicits T-helper cell 1 (Th1) biased T-cell and humoral responses to both S and N that are greater than those seen with hAd5 S wild type delivering only unmodified S. We then compared SC to intranasal (IN) prime vaccination with SC or IN boosts and show that an IN prime with an IN boost is as effective at generating Th1 biased humoral responses as the other combinations tested, but an SC prime with an IN or SC boost elicits greater T cell responses. Finally, we used a combined SC plus IN (SC + IN) prime with or without a boost and found the SC + IN prime alone to be as effective in generating humoral and T-cell responses as the SC + IN prime with a boost. The finding that SC + IN prime-only delivery has the potential to provide broad immunity—including mucosal immunity—against SARS-CoV-2 supports further testing of this vaccine and delivery approach in animal models of viral challenge.
Highlights
We have developed a COVID-19 vaccine, hAd5 S-Fusion + N-Enhanced T-cell Stimulation Domain (ETSD), that expresses SARS-CoV-2 spike (S) and nucleocapsid (N) proteins with modifications to increase immune responses delivered using a human adenovirus serotype 5 platform
Before initiation of in vivo studies in mice, our goal of enhancing cell-surface display of S was confirmed by transduction of HEK-293T cells with hAd5 S-wild type (S-WT), S-WT + N-ETSD, S-Fusion alone, and S-Fusion + N-ETSD followed by flow cytometric analysis of anti-S receptor binding domain (RBD) antibody binding
The highest cell-surface expression of RBD was detected after transduction with dual antigen hAd5 S-Fusion + N-ETSD (Fig. 1d)
Summary
We have developed a COVID-19 vaccine, hAd5 S-Fusion + N-ETSD, that expresses SARS-CoV-2 spike (S) and nucleocapsid (N) proteins with modifications to increase immune responses delivered using a human adenovirus serotype 5 (hAd5) platform. The vaccine comprises the SARS-CoV-2 spike (S) protein modified for enhanced cell surface expression (S-Fusion) to increase humoral responses and the nucleocapsid (N) protein with an Enhanced T-cell Stimulation Domain (N-ETSD) to target N to the endosomal/lysosomal cellular compartment[1] to enhance MHC class I and II presentation. The platform shows potential to be suitable for homologous prime-boost immunization and/or immunotherapy regimens[8,9,10,11,12] This generation Ad vector has demonstrated safety in over 125 patients with solid tumors.
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