Characterization of the Spatiotemporal Localization of a Pan-Mucorales–Specific Antigen During Germination and Immunohistochemistry

Abstract

Abstract Background Mucormycosis is an aggressive invasive fungal infection caused by molds in the order Mucorales. Early diagnosis is key to improving patient prognosis, yet it relies on insensitive culture or nonspecific histopathology. A pan-Mucorales–specific monoclonal antibody (mAb), TG11, was recently developed. Here, we investigate the spatiotemporal localization of the antigen and specificity of the mAb for immunohistochemistry. Methods We used immunofluorescence microscopy to assess antigen localization in 11 Mucorales species of clinical importance and live imaging of Rhizopus arrhizus germination. Immunogold transmission electron microscopy revealed the subcellular location of mAb TG11 binding. Finally, we performed immunohistochemistry of R arrhizus in an ex vivo murine lung infection model alongside lung infection by Aspergillus fumigatus. Results Immunofluorescence revealed TG11 antigen production at the emerging hyphal tip and along the length of growing hyphae in all Mucorales except Saksenaea. Time-lapse imaging revealed early antigen exposure during spore germination and along the growing hypha. Immunogold transmission electron microscopy confirmed mAb TG11 binding to the hyphal cell wall only. The TG11 mAb stained Mucorales but not Aspergillus hyphae in infected murine lung tissue. Conclusions TG11 detects early hyphal growth and has valuable potential for diagnosing mucormycosis by enhancing discriminatory detection of Mucorales in tissue.