Latent Human Papillomavirus infection is comparable in the larynx and trachea

Recurrent respiratory papillomas are benign airway tumors caused by Human Papillomaviruses (HPVs) types 6 and 11. The disease is characterized by multiple recurrences of papillomas following surgical removal, caused by activation of latent HPV DNA. Most patients have laryngeal disease, while only a small subset has tracheal involvement. We have asked whether the lower frequency of tracheal papillomas was due to reduced prevalence of latent/subclinical tracheal HPV infection or reduced likelihood of activation to clinically apparent disease. A total of 121 biopsies of clinically normal laryngeal and tracheal tissues from 61 patients with laryngeal papillomas were analyzed for HPV DNA by polymerase chain reaction, confirmed by Southern blot hybridization. Patients were followed for 3-18 years (mean = 5.5 +/- 4.4), with only one developing subsequent tracheal disease. There was no significant difference in prevalence of latent HPV DNA between larynx and trachea, analyzing either those patients with a single biopsy or those with more than one biopsy of larynx, trachea, or both. There was also no significant difference between tracheal latency with HPV 6 and HPV 11. We conclude that HPV infects tracheal mucosa and is maintained as a latent infection in the trachea as efficiently as in the larynx. Therefore, we propose that the low frequency of tracheal disease reflects a lower frequency of HPV activation, and postulate that cellular factors that differ between the stratified squamous epithelium of the larynx and the ciliated pseudo-stratified columnar epithelium of the trachea contribute to this difference.