Development of a COVID-19 vaccine using inactivated E. coli

Inactivated whole-cell vaccines, also known as ‘killed vaccines,’ are among the most traditional type of vaccine in use, having been developed against a wide range of pathogens, including cholera and E. coli.

In a new study, released as an introduction to the bioRxiv* server, a team of full-cell inactive researchers E.coli with a reduced genome and used this to express specific coronavirus fusion peptides, showing a strong anamnestic response.

Vaccine design

Gram-negative bacteria have transport proteins, autotransporters, that allow the proteins expressed on the surface of cells to be exchanged, and modern genetic engineering allows proteins of interest to be expressed on the surface in this way. Up to 200,000 foreign proteins can be exhibited on the surface of a single bacterium, and this technology has previously been used to elicit an immune response. in vivo by displaying selected pathogenic antigens. However, the range of antigens that can be expressed by this method is limited by size, to less than about 50 kDa, and bacteria do not excrete proteins by mammalian glycolysation, and so may not produce the appropriate antibodies.

No vaccines using this technology have yet been approved, largely due to the low level of immunity exhibited due to inappropriate glycolysation. In this paper, the group hypothesized that the removal of superficial proteins from the bacteria, in addition to the expressed antigen, could provide a stronger immune response. The total SARS-CoV-2 spike protein used in the vaccines used is a large 180 kDa protein, so it could not be used with this method. Several families of viruses, including coronaviruses and SARS-CoV-2, carry HIV-1 fusion peptide, which is involved in cell membrane translocation. Because this region is highly conserved, it could be a good vaccine candidate, and the additional authors point out that the use of the whole spike protein is included. with an increased risk of rare inflammatory syndromes.

Testing the vaccine

The group used a whole cell that was killed E. coli reduced in genome to exhibit fewer native surface cell proteins. A plasmid was injected into the bacteria to express the HIV-1 specific fusion peptide SARS-CoV-2, which was then confirmed by antibody binding assays. Other vaccines have also been prepared for swine epilepsy virus (PEDV), expressing the peptide fusion relative for this virus.

Pigs were vaccinated with one of the prepared and controlled vaccines, administered with an increase in day 21, then challenged with oral PEDV infection with the individual virus at day 35. Blood was collected weekly , and circulating protein antibodies against fusion measured, not significantly higher after vaccination but before the challenge. However, after the viral challenge, the values ​​against FP were significantly higher among the vaccines, suggesting that the vaccines had responded to the pigs. Serum interferon-ìrean levels were also higher among the vaccine, and fewer of these pigs showed external signs of PEDV-related symptoms.

As expected, the PEDV vaccine was more effective against PEDV vaccine than the SARS-CoV-2 vaccine. However, the appearance of the fusion proteins derived from each virus was so great that a statistically significant response was found. In fact, the 13 layers of amino acid surround the 6 basic residues of each identical layer.

The group argues that these vaccines may be easier to produce and transport than the mRNA vaccines currently in use, especially since a strong cold chain is required in the case of finally, which requires a constant temperature of -20 ° C or colder. They do, however, acknowledge that the ability of a immune response in hosts toward the genome is reduced. E. coli risk is low but possible, and requires further investigation.

* Important message

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical / behavioral practice, or treated as fixed information.