Molecular analysis of resistance to interferon in patients with laryngeal papillomatosis.

Although interferon (IFN)-alpha has been used successfully as an adjuvant therapy in laryngeal papillomatosis, some patients are resistant to this treatment. In order to know which patients will benefit from the therapy, we have tried to find a relationship between the IFN response and the viral and host parameters in the lesion. Detection of viral type and copy numbers by polymerase chain reaction (PCR) showed that all patients infected with human papillomavirus (HPV)-11 were sensitive to the treatment, in contrast to those infected with HPV-6. These differences could be explained in part by the inability of HPV-11 E7 to inhibit the induction of an IFN-responsive element, whereas HPV-6 E7 almost completely inhibited the activity of this promoter in transient transfection experiments. Local immune status in the lesion showed that all HPV-11-infected patients had detectable levels of interleukin (IL)-15 and IFN-gamma mRNA, in contrast to HPV-6-infected patients, in whom mRNA for these cytokines was almost absent. Viral copy numbers and levels of IL-4 mRNA could not be correlated with IFN response. Only one patient resistant to recombinant IFN-alpha2b and negative for HPV DNA presented high titers of neutralizing anti-IFN-alpha2b antibodies. This patient became sensitive when natural IFN-alpha was administered. These results suggest that response to IFN may be a complex phenomenon resulting from the interaction between viral and host elements.