HPV-DNA in sputum cannot be used to distinguish between an infection or a contamination

Introduction HPV-infection is one cause for developing HNSCC. Sputum is discussed to be a possible route of infection. The presented study aims to answer the question whether or not HPV-particles are exclusively found in the cellular compartment of the sputum or might also be found in the cell free supernatant.

Methods Prior to operation 2 sputum samples each were retrieved from HNSCC-patients (CA; n = 52), patients with tonsillar hyperplasia (H; n = 32) and chronic tonsillitis (CT; n = 107). DNA and RNA was isolated from the native sputum samples and after centrifugation (10 min; 600 g, 4°C) from the resulting cellular compartments and the cell free supernatants. HPV-detection was performed using a PCR-based assay.

Results 4/32 (12.5 %) H- and 11/107 (10,3 %) CT-samples are HPV-DNA-positive (total sputum and cellular fraction) but all are HPV-RNA-negative. Sputum samples of 20/52 (38.5 %) CA-patients are HPV-DNA-positive and all but 3 are also HPV-RNA-positive. Of these 3 HPV-RNA-negative samples the cellular fractions of 2 sputum samples were HPV-DNA-negative but the cell free supernatants of these samples were HPV-16-DNA positive.

Discussion Interestingly, in 2/191 (1 %) of the patients HPV-DNA could be detected in the cell free supernatant of the sputum, but not in the cellular compartment of the same sputum sample. This finding raises the question whether the detection of HPV in the total sputum (cellular fraction and cell free supernatant) is equivalent to an HPV-infection of the mucosal tissue. The here presented finding do indeed argue in favor of a contamination or colonization of the mucosal tissue rather than an infection.

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Publication History

Article published online:
10 June 2020