Abstract
Recurrent respiratory papillomatosis (RRP) has a wide range of severity. We investigate the relationship between human papillomavirus (HPV) particle production and severity of RRP. From September 2005 to June 2021, 68 RRP samples (from 29 patients) were included. HPV type was determined. HPV viral load, physical status, and demographic and clinical characteristics were assessed. Immunohistochemistry (IHC) was performed for p16, Ki-67, L1, and E4. We used NanoSuit-CLEM (correlative light and electron microscopy) and transmission electron microscopy (TEM) to examine the samples. The total number of surgeries in HPV-positive and HPV-negative cases were 3.78 (n = 55/68, range: 1-16) and 1.30 (n = 13/68, range: 1-3), respectively (p = 0.02). IHC showed that L1 and E4 were correlated and expressed on the tumour surface. NanoSuit-CLEM and TEM revealed HPV particles in L1-positive nuclei. L1 IHC-positive cases had a shorter surgical interval (p < 0.01) and more frequent surgeries (p = 0.04). P16 IHC, viral load, and physical status were not associated with disease severity. This study visualised HPV particle production in RRP for the first time. Persistent HPV particle infection was associated with severity. We suggest L1 IHC for evaluating RRP severity in addition to the Derkay score.