The detection of a virus replication product, dsRNA, was also evident on IHC. expressing coronavirus (SARS, MERS) spike as a biosecure alternative to assays involving live computer virus was undertaken. Optimized protocols were successfully applied to experimental animal-derived tissues. The diverse techniques for computer virus detection and control material generation demonstrated in this study can be applied to investigations HSF1A of coronavirus pathogenesis and therapeutic research in animal models. classified under the order and family not applicable, double stranded RNA, feline infectious peritonitis computer virus. Open in a separate windows Physique 1 Immunohistochemical labelling of FFPE SARS-CoV and SARS-CoV-2 infected cells and uninfected cells. Immunodetection performed using SARS-CoV spike rabbit monoclonal antibody (aCc), SARS-CoV nucleoprotein rabbit polyclonal antibody (dCf) and double-stranded RNA (dsRNA) rabbit monoclonal antibody (gCi). Scale bars, 20?m. Alongside developing the IHC technique to detect SARS-CoV specific antigens, the IHC detection of dsRNAa viral replicative intermediate was evaluated. Among the three antibodies evaluated, both the J2 recombinant clone raised in mouse and rabbit was able to detect dsRNA in HSF1A infected cell pellets with cytoplasmic chromogen deposits (Fig.?1g,h; Supp. Physique?1c, d). However, the amount of immunolabelling was not abundant in comparison to SARS specific antigen detection method. The other clone, 9D5, did not generate chromogen deposits with IHC. The cell pellets were also evaluated for non-specific HSF1A binding using an alphacoronavirus antibody against Feline infectious peritonitis computer virus (FIPV). No chromogen was detected in uninfected and SARS-CoV infected cells using the FIPV antibody (not shown). Detection of RNA encoding SARS-CoV and SARS-CoV-2 spike protein One RNAScope? probe was evaluated for the ability to detect SARS coronavirus RNA in FFPE cell pellets. The V-nCoV2019-5 probe did not produce labelling to SARS-CoV (Fig.?2a) but successfully labelled HSF1A SARS-CoV-2 infected cell pellets (Fig.?2b). Labelling was not observed on uninfected cell pellets (Fig.?2c). Open in a separate window Physique 2 In situ hybridisation (ISH) of FFPE cells infected with SARS-CoV and SARS-CoV-2 using RNAScope?. ISH performed using RNA probes designed specific to SARS-CoV-2 spike RNA. SARS-CoV (a) and SARS-CoV-2 infected HGFR cells (b), uninfected cells (c). Scale bars, 20?m. Detection of SARS-CoV and SARS-CoV-2 pseudotype computer virus in producer cells To determine if FFPE in vitro generated pseudotype computer virus expressing recombinant spike protein would be suitable for IHC detection, IHC using the spike mAb identified above was performed on producer cells consisting of lentiviral pseudotype computer virus expressing either SARS-CoV, SARS-CoV-2 or MERS spike protein. In this assay, the spike mAb was able to detect both SARS-CoV and SARS-CoV-2, displaying specific cytoplasmic and membranous chromogen deposits (Fig.?3a,b). Immunolabelling was not detectable for MERS spike expressing cells (Fig.?3c) or untransfected cells (Fig.?3d). Open in a separate window Physique 3 Immunohistochemistry labelling of FFPE cells expressing SARS-CoV, SARS-CoV-2 and MERS spike proteins. Immunodetection performed using SARS-CoV spike rabbit monoclonal antibody on producer cells for SARS-CoV (a), SARS-CoV-2 (b) and MERS-CoV pseudotype computer virus (c) and non-transfected cells?(d). Scale bars, 20?m. Application of IHC and ISH on animal tissues IHC and ISH methods developed and optimised on FFPE cell pellets were tested on nasal turbinates of experimentally derived SARS-CoV-2 infected ferret. Using the spike antibody, immunolabelling was observed specifically labelling the luminal cells in the olfactory epithelial mucosa (Fig.?4a). Nucleoprotein labelling (Fig.?4b) was more ubiquitous in the cytoplasm compared to spike labelling. dsRNA immunolabelling was limited to cytoplasm of the perinuclear region (Fig.?4c), which corresponds to coronavirus replication site19. As for ISH against spike gene, chromogen was deposited diffusely within the cytoplasm of the infected epithelial cells (Fig.?4d). Serial sections immunolabelled with nucleoprotein, spike or dsRNA antibody (Fig.?4a,c), or spike ISH showed consistent labelling in infected cell population, confirming the specificity of the detection of SARS-CoV-2 in animal tissues. Open in a separate window Physique 4 Immunohistochemistry and in situ hybridisation detection of SARS-CoV-2 and RNA on infected ferret tissues. Detection of spike protein (a), nucleoprotein (b) and dsRNA antigens (c) and spike RNA (d) labelling. Tissue shrinkage artefact with ISH pre-treatment (d). Scale bars, 20?m. Discussion In this report, we described optimized methods for antigen and RNA detection for SARS-CoV and SARS-CoV-2?present in FFPE specimens. Using antibodies raised against SARS-CoV spike and nucleoprotein, we were able to detect the antigens of both SARS-CoV and SARS-CoV-2 present in infected cells and processed for histology. In addition, RNAScope? probe designed specifically for SARS-CoV-2 labelled specifically to cognate computer virus strain. The detection of a computer virus replication product, dsRNA, was also evident on IHC. Furthermore, we utilised FFPE pseudotype computer virus producer cells.