Immunohistochemical Analyses of Monkeypox Skin Lesions with MPXV A29 and A35 Antibodies: A Novel Insight for Clinical-Histopathological Forms.

The aim of this study was to describe the clinical, histopathological, and immunohistochemical characteristics of MPX and offer meaningful insights into the clinicopathology of MPX. We recruited eight men who had sex with men diagnosed with MPX based on positive results from MPX Virus (MPXV)-specific polymerase chain reaction. Skin biopsies were obtained from four selected lesions, including typical and atypical lesions. Histopathological examinations of atypical solitary ulceration revealed infiltrating inflammatory cells predominantly composed of plasma cells and lymphocytes, forming a "sleeve" around the superficial vessels of the dermis. These features might be misinterpreted as indicative of cutaneous syphilis infection. Meanwhile, typical pustular lesions displayed central necrotic epidermis accompanied by perivascular inflammatory infiltrate dominated by neutrophils, as well as ballooning and reticular degeneration of keratinocytes. Additionally, multinucleated keratinocytes and eosinophilic cytoplasmic inclusions known as Guarnieri's bodies were also observed. Importantly, this study represented the pioneering report on immunohistochemical detection of MPXV A29 and A35 proteins in skin lesions, distinguishing it from previous studies that focused on detecting vaccinia virus protein. The anti-MPXV A29 antibody exhibited robust cytoplasmic staining specifically within affected keratinocytes in both adjacent epidermis and hair follicles, thereby it could contribute to the diagnosis of MPX, especially for cases with atypical skin lesions.