for their help with animal experiments. Footnotes 1 clinicaltrials.gov 2 www.biocloud.net 3 https://bugbase.cs.umn.edu/ Funding This study was supported by the key underprop project of Tianjin Municipal Science and Technology Bureau (20YFZCSN00340), the Tianjin Synthetic Biotechnology Innovation Capability Troxacitabine (SGX-145) Improvement Project in China (TSBICIP-KJGG-014), and the National Natural Science Foundation of China (31400064). Supplementary Material The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2022.792532/full#supplementary-material Click here for additional data file.(16K, XLSX). microbiota were detected from oral administration mice compared with those of the control group. Interestingly, the recombinant yeast was identified in female fetal of the high-dose group. These results revealed that this displaying yeast could fulfill the agent-driven immunoregulation and gut microbiome reconstitution. The findings will shed light on new dimensions against SARS-CoV-2 contamination with the synergistic oral agents as promising non-invasive immunization and restoring gut flora. ST1814G using the LiAc/ss carrier DNA/PEG method as described (Gietz and Woods, 2002). Transformants were selected on synthetic-defined (SD) medium minus Leu plates and incubated at 30C for 72 h. Six impartial clones of ST1814G-S (RBD-FP) were tested. Open in a separate window Physique 1 Construction of spike S [receptor-binding domain name (RBD)-fusion peptide (FP)] expression vectors. (A) Schematic diagram of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein expression construct. (B) Diagram of the chromosomal region, including the S (RBD-FP) transcriptional unit with promoter and terminator fused to the C-terminal of Aga2 for presentation on the yeast cell surface. The structure of RBD-FP subunit was predicted by SWISS-MODEL based on PDB 7cn8 as the template. The genotyping assay was performed by genomic DNA extraction (Looke et al., 2011) from recombinants and PCR using primer pair (S-F 331: AATATTACAAACTTGTGCCCT and S-R 524: AACAGTTGCTGGTGCATGTAG). Also, the phenotype assay was identified by Western blotting, flow cytometry, and immunofluorescence assay. Western Blotting To evaluate the expression of S (RBD-FP) proteins in the recombinant, yeast cells were cultured in yeast extract-peptone-dextrose (YPD) liquid medium at 30C for 48 h. The 2-ml culture was centrifuged at 5,000 for 1 min, then, the pellet in 100 l lysis buffer (50 mM TrisCHCl [pH 8.0], 2 mM EDTA, 1 mM phenylmethylsulfonyl fluoride) was resuspended, and glass beads were added to break cells five times using the disruptor genie (Scientific Industries, D48-1040). The resulting proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDSCPAGE) and electroblotted onto a polyvinylidene difluoride (PVDF) membrane. Then, proteins-enriched membranes were blocked with Tris-buffered saline [TBS with 0.1% Tween-20 (TBST)], added 5% (w/v) non-fat dry milk buffer for 1 h, and incubated with His-specific antibody (Cat. HT501, Transgene, Beijing, China) or spike protein S1-specific Troxacitabine (SGX-145) antibody (Cat. A20136, ABclonal, Wuhan, China) as the primary antibody (1:5,000 dilution) overnight at 4C, followed by incubation Troxacitabine (SGX-145) with Horseradish peroxidase (HRP)-conjugated secondary antibody (Goat anti-Rabbit, Cat. PI31460, Goat anti-Mouse, Cat PI31430, Invitrogen? from Thermo Fisher Scientific, Carlsbad, CA, United States) for 1 h at room temperature (RT). The PVDF membrane was LIMK2 antibody washed at least three times with TBST. Bound antibodies were detected using the Pierce ECL Western blotting substrate (Cat. 32109, Thermo Fisher Scientific, Carlsbad, CA, United States), and band densitometry was performed with Image Lab software (Bio-Rad, Hercules, CA, United States). Immunofluorescence Assay Yeast transformants were subjected to an indirect immunofluorescence assay with a polyclonal 6*His-Tag antibody (Cat. HT501, Transgene, Beijing, China) and a fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse immunoglobulin as the secondary antibody (Cat. ab6785, abcam, Cambridge, UK). Yeast culture was centrifuged, and the pellet was washed with PBS three times at RT and then incubated with primary antibody (anti-His, 1:5,000 dilution) at RT for 30 min. After the washing step with PBS, the secondary antibody FITC-conjugated anti-mouse IgG (1:500 dilution) was incubated for 30 min. The pellet was washed with PBS and visualized under a laser confocal microscope (UltraView Vox, PerkinElmer). ST1814G served as a negative control. Flow Cytometry The characterization of both the recombinant and the control cells of strains by flow cytometry has been compiled based on the set of His tag marker as described above. The experimental procedure was similar to the one described in immunofluorescence. Yeast cells were harvested after 48 h and washed three times with PBS..