Prime-boost protein subunit vaccines against SARS2 CoV-2 are highly immunogenic in mice and macaques
Cardiff University review vaccines
First Author: Hyon-Xhi Tan
Journal/preprint name: bioRxiv
Paper DOI: https://doi.org/10.1101/2020.09.01.278630
Tags: Vaccine
Summary
In this preprint, the authors present their data comparing the efficacy and immunogenicity of both homologous and heterologous prime-boost vaccination of mice and macaques with either a viral spike (S) or a RBD subunit vaccine. S vaccines elicited superior immunogenicity in mice and comparable responses to RBD vaccination in macaques. Study highlights the potential of using recombinant spike protein as a vaccine candidate and highlights key differences in vaccine responses between mice and macaques.
Research Highlights
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In mice, serum antibody titres, and GC B Cell and TFH cell responses are markedly improved with a single immunization of S rather than RBD
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Homologous (RBD-RBD or S-S) or heterologous (RBD-S or S-RBD) prime boost vaccination of mice, elicited poor immunogenic responses if S was not included in the vaccination strategy.
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Homologous (RBD-RBD or S-S) and heterologous (S-RBD) vaccination of macaques, elicited comparable immunogenic responses with all vaccine strategies utilized.
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A comparison of serum and neutralizing Ab titres revealed that responses to vaccination in mice far exceed those observed in convalescent Covid patients*see limitation below.
Impact for COVID-19 research:
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Provides evidence that the immunological response to vaccination can be improved by including the spike protein alongside the RBD.
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Demonstrates the differences in the immunological response between mouse and non-human primates to the same vaccine-strategy, with particular reference to the differing VH gene usage and how this impacts on the generation of B cell responses post vaccination.
Methodologies:
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Study Type: In vivo (mouse and NHP).
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Important cell lines/viral models used: Vaccine study
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Key Techniques: Flow cytometric analysis of S and RBD-specific B cells and TFH cells, BCR sequencing, ACE2-RBD inhibition ELISA.
Limitations:
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As with all macaques studies the numbers are small, however, it is difficult to draw firm conclusions with a N of 2. Furthermore, the presentation of data in Figure 3 is particularly difficult to interpret for some of the panels.
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There are differences between the vaccine approaches used in the mice and macaques and this is not discussed by the authors. A vaccination dose-response, at least in mice should have been considered.
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In the macaque model, the RBD-S prime-boost vaccine has not been studied and the authors provide no explanation as to why.
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The patients recruited for the convalescent and B Cell studies, are mainly mild infections, but do include some severe individuals, would have been useful to highlight the severe patients in Figure 4.