Killed whole-genome reduced-bacteria surface-expressed coronavirus fusion peptide vaccines protect against disease in a porcine model

Abstract

As the coronavirus disease 2019 (COVID-19) pandemic rages on, it is important to explore new evolution-resistant vaccine antigens and new vaccine platforms that can produce readily scalable, inexpensive vaccines with easier storage and transport. We report here a synthetic biology-based vaccine platform that employs an expression vector with an inducible gram-negative autotransporter to express vaccine antigens on the surface of genome-reduced bacteria to enhance interaction of vaccine antigen with the immune system. As a proof-of-principle, we utilized genome-reduced Escherichia coli to express SARS-CoV-2 and porcine epidemic diarrhea virus (PEDV) fusion peptide (FP) on the cell surface, and evaluated their use as killed whole-cell vaccines. The FP sequence is highly conserved across coronaviruses; the six FP core amino acid residues, along with the four adjacent residues upstream and the three residues downstream from the core, are identical between SARS-CoV-2 and PEDV. We tested the efficacy of PEDV FP and SARS-CoV-2 FP vaccines in a PEDV challenge pig model. We demonstrated that both vaccines induced potent anamnestic responses upon virus challenge, potentiated interferon-γ responses, reduced viral RNA loads in jejunum tissue, and provided significant protection against clinical disease. However, neither vaccines elicited sterilizing immunity. Since SARS-CoV-2 FP and PEDV FP vaccines provided similar clinical protection, the coronavirus FP could be a target for a broadly protective vaccine using any platform. Importantly, the genome-reduced bacterial surface-expressed vaccine platform, when using a vaccine-appropriate bacterial vector, has potential utility as an inexpensive, readily manufactured, and rapid vaccine platform for other pathogens.

Functional Analysis of Human and Feline Coronavirus Cross-Reactive Antibodies Directed Against the SARS-CoV-2 Fusion Peptide

“…Sera from mice immunized with peptide PSKRSFIEDLLF or peptide IEDLLFNKVTLA were unable to neutralize SARS-CoV-2 ( 60 ). Also, immunization of pigs with a 24-mer peptide spanning the S2′ cleavage site of a porcine alphacoronavirus (porcine epidemic diarrhea virus, PEDV) or with the homologous peptide from SARS-CoV-2, did not elicit PEDV-neutralizing antibodies before PEDV challenge ( 61 ). Finally, sera from rabbits immunized with a long peptide encompassing the fusion peptide (S7,972–8,013) showed moderate neutralization activity against SARS-CoV-2 pseudotypes in Calu-3 cells ( 62 ).…”

Minicells from Highly Genome Reduced Escherichia coli: Cytoplasmic and Surface Expression of Recombinant Proteins and Incorporation in the Minicells

“…We then cured the strain of kanamycin resistance by recombination with a derivative of pCP20 , and verified the removal of the kanamycin resistance gene phenotypically, confirmed removal with sequencing, and reconfirmed the minicell production phenotype as described below. To examine expression in the minicells made from the genome reduced bacteria, we used a plasmid, pMP2463 that expresses GFP, and we commissioned the synthesis of a plasmid, pRAIDA2 (Figure ), that includes an AIDA-I-based autotransporter expression cassette. , In its parental form, pRAIDA2 has an influenza HA immunotag in the autotransporter expression cassette.…”

“…coli in the TMUG collection (ME5125) , with a GFP expressing plasmid, pMP2463 . We also transformed the undeleted ME 5000 and 29.7% deleted ME 5125 stains with minC minD mutations with pRAIDA2, the plasmid that expresses an HA immunotag via an AIDA-I autotransporter surface expression cassette under the control of a rhamnose-inducible promoter …”

Human vaccines & immunotherapeutics: news

“…This vaccine, which is easily produced and could solve many logistical hurdles, was protective in a porcine model. 3…”