Surface Display of Peptides Corresponding to the Heptad Repeat 2 Domain of the Feline Enteric Coronavirus Spike Protein on Bacillus subtilis Spores Elicits Protective Immune Responses Against Homologous Infection in a Feline Aminopeptidase-N-Transduced Mouse Model

Abstract

Although feline coronavirus (FCoV) infection is extremely common in cats, there are currently few effective treatments. A peptide derived from the heptad repeat 2 (HR2) domain of the coronavirus (CoV) spike protein has shown effective for inhibition of various human and animal CoVs in vitro, but further use of FCoV-HR2 in vivo has been limited by lack of practical delivery vectors and small animal infection model. To overcome these technical challenges, we first constructed a recombinant Bacillus subtilis (rBSCotB-HR2P) expressing spore coat protein B (CotB) fused to an HR2-derived peptide (HR2P) from a serotype II feline enteric CoV (FECV). Immunogenic capacity was evaluated in mice after intragastric or intranasal administration, showing that recombinant spores could trigger strong specific cellular and humoral immune responses. Furthermore, we developed a novel mouse model for FECV infection by transduction with its primary receptor (feline aminopeptidase N) using an E1/E3-deleted adenovirus type 5 vector. This model can be used to study the antiviral immune response and evaluate vaccines or drugs, and is an applicable choice to replace cats for the study of FECV. Oral administration of rBSCotB-HR2P in this mouse model effectively protected against FECV challenge and significantly reduced pathology in the digestive tract. Owing to its safety, low cost, and probiotic features, rBSCotB-HR2P is a promising oral vaccine candidate for use against FECV/FCoV infection in cats.

Feline Infectious Peritonitis mRNA Vaccine Elicits Both Humoral and Cellular Immune Responses in Mice

“…Another recent FCoV vaccine using the recombinant heptad repeat 2 domain displayed on Bacillus subtilis spores [56]. The biggest limitations of this vaccine include the use of peptides within the spike protein of serotype II of FCoV, which, again, is not the predominant circulating type, and the premise of this vaccine to induce sterilizing immunity, which would require vaccination prior to infection.…”

Immunoinformatics-aided rational design of a multi-epitope vaccine targeting feline infectious peritonitis virus

“…Other than the antiviral compounds, numerous efforts have been made to develop vaccines against FCOV ( 13 , 76 , 77 ). Oral administration of a recombinant vaccine based on the Bacillus subtilis surface display technique expressing FECV heptad repeat 2 domain peptide protected against FECV infection and ameliorated digestive tract pathology in mice models ( 13 ). A live attenuated FIP vaccine made using the deletion of ORF 3abc protected cats from lethal FIPV challenge ( 78 ).…”

“…Furthermore, the spike protein is also important for the induction of cell-mediated immunity and antibody response in FCoV-infected felids ( 10 ). Moreover, the spike protein of FCoV is a significant determinant of virulence, pathogenesis, and the switch from a virulent FECV to a virulent FIPV ( 13 ). Previous studies have utilized a heptad repeat 2 peptide (57 amino acids) from the FECV spike protein to develop a recombinant oral vaccine candidate ( 13 ).…”

“…Moreover, the spike protein of FCoV is a significant determinant of virulence, pathogenesis, and the switch from a virulent FECV to a virulent FIPV (13). Previous studies have utilized a heptad repeat 2 peptide (57 amino acids) from the FECV spike protein to develop a recombinant oral vaccine candidate (13).…”

Evaluation of the Immunity Responses in Mice to Recombinant Bacillus subtilis Displaying Newcastle Disease Virus HN Protein Truncations

“…Research efforts have yielded the development of protective antigens through the utilization of diverse coat proteins, such as cotB , cotC , cotG , etc., as anchoring agents. This approach facilitates the expression of antigenic proteins on the spore surface and culminates in the creation of recombinant probiotics that are rich in immunogenic properties [ 7 , 8 , 9 ]. Recombinant strains of B. subtilis are characterized by their ease of storage and transport, which simplifies the immunization process and reduces stress in animals.…”