Cell Immunity: SARS-CoV-2 vaccines status

Cell Immunity: SARS-CoV-2 vaccines status

Now the new coronary pneumonia has developed into a global pandemic infectious disease. In most age groups, the severity of the disease is higher than the seasonal flu or the 2009 H1N1 pandemic, so vaccines and treatments are urgently needed to deal with this new virus.

Recently, Cell Immunity published a review article entitled "SARS-CoV-2 vaccines: status report", which summarizes the research status of the SARS-CoV-2 vaccine.

Currently developing SARS-CoV-2 vaccine

It may take years to develop a vaccine for human use, especially if the new technology currently in use has not yet undergone extensive safety testing or mass production. There is currently no coronavirus vaccine on the market and no large-scale vaccine production capacity (Table 1). The first vaccine development process can be lengthy and time-consuming (Figure 1).

Overview of Potential SARS-CoV-2 Vaccine Platforms. Figure 1: Overview of Potential SARS-CoV-2 Vaccine Platforms.

Moderna and the Vaccine Research Center at the National Institutes of Health jointly developed an mRNA vaccine. The mRNA is encapsulated in lipid nanoparticles and injected into the body to express the target antigen in the body. This is currently the furthest along, and a phase I clinical trial recently started (ClinicalTrials .gov: NCT04283461). Curevac is developing a similar vaccine, but it is still in the preclinical phase.

Other preclinical treatments include (Figure 1, Table 1):

  • Recombinant-protein-based vaccines (focused on the S protein, e.g. ExpresS2ion, iBio, Novavax, Baylor College of Medicine, Queensland University, Sichuan Clover Biopharmaceuticals, etc.);
  • Viral vector vaccines (focused on the S protein, e.g. Vaxart, Geovax, Oxford University, Cansino Biologics, etc.);
  • DNA vaccines (focused on the S protein, Inovio, Applied DNA Sciences, etc.);
  • Live attenuated vaccines (Codagenix with the Serum Institute of India, etc.);
  • Inactivated virus vaccines.

All these platforms have their pros and cons (Table 1), and it is impossible to predict which strategy will be faster and which strategy will be more successful.

Table 1: Overview of Vaccine Production Platforms and Technologies for SARS-CoV-2

Platform Target Advantages Disadvantages
RNA vaccinesS proteinNo infectious virus needs to be handled; vaccines are typically immunogenic, rapid production possible.Safety issues with reactogenicity have been reported.
DNA vaccinesS proteinNo infectious virus needs to be handled, easy scale up, low production costs, high heat stability, tested in humans for SARS-CoV-1, rapid production possible.Vaccine needs specific delivery devices to reach good immunogenicity.
Recombinant protein vaccinesS proteinNo infectious virus needs to be handled; adjuvants can be used to increase immunogenicity.Global production capacity might be limited. Antigen and/or epitope integrity needs to be confirmed. Yields need to be high enough.
Viral vector-based vaccinesS proteinNo infectious virus needs to be handled, excellent preclinical and clinical data for many emerging viruses, including MERS-CoV.Vector immunity might negatively affect vaccine effectiveness (depending on the vector chosen).
Live attenuated vaccinesWhole virionStraightforward process used for several licensed human vaccines; existing infrastructure can be used.Creating infectious clones for attenuated coronavirus vaccine seeds takes time because of large genome size. Safety testing will need to be extensive.
Inactivated vaccinesWhole virionStraightforward process used for several licensed human vaccines, existing infrastructure can be used, has been tested in humans for SARS-CoV-1, adjuvants can be used to increase immunogenicity.Large amounts of infectious virus need to be handled (could be mitigated by using an attenuated seed virus). Antigen and/or epitope integrity needs to be confirmed.

Johnson & Johnson (J&J) and Sanofi recently joined in the development of the SARS-CoV-2 vaccine. However, J&J is using an experimental adenoviral vector platform and has not yet obtained a vaccine license. The production process of Sanofi vaccine is like that of the approved FluBlok recombinant influenza virus vaccine. It will take at least a few months or even a few years to be put into use in the population.

For SARS-CoV-2, the vaccine may come too late to catch up with the first wave of the epidemic. However, the vaccine is still useful if a second large-scale outbreak occurs later, or if SARS-CoV-2 continues to spread as a seasonal virus after a pandemic. In addition, the lessons learned from the response to this epidemic will enable us to prepare better in the future.

Ref:

  1. Fatima Amanat, Florian Krammer. SARS-CoV-2 Vaccines: Status Report. Immunity. 2020.;52:583-589.
* Only for research. Not suitable for any diagnostic or therapeutic use.