Assessing the Efficacy of Human Papillomavirus Disinfection and the Risk of Transmission from Clinical Lesions

Abstract

<h3>Background</h3> HPV genomes can be detected on medical devices following hospital disinfectant procedures. Recent reports concluded that oncogenic HPVs derived from laboratory tissue-based models are not susceptible to commonly used high-level disinfectants, intensifying concerns that medical instruments may provide transmission of nosocomial HPVs infections. Therefore, we determined the infectious load of HPVs from clinical lesions and investigated the effectiveness of disinfectants on HPV virions derived from laboratory model systems. <h3>Methods</h3> Infectious HPV virions were isolated from cell culture, organotypic epithelial tissue cultures, and mouse xenografts. Clinical samples from recurrent respiratory papillomas (RRPs) and anogenital warts were obtained under IRB approval. The infectivity of HPV virion stocks was measured by the detection of spliced viral E1^E4 mRNAs in infected keratinocytes. Infections were validated by time-dependent detection of E1^E4 mRNAs, resistance to ribonuclease treatment and susceptibility to antibody-mediated neutralization. Our infectivity assay demonstrated a dynamic range of >3-5 log10. Suspension-based disinfection assays employed diluted ortho-phthalaldehyde (OPA) and 0.825% hypochlorite. <h3>Results</h3> In contrast to prior reports, we found that validated HPV virions obtained from a variety of sources were susceptible to a 2.5 to 4 log10 reduction in infectious titer when exposed as directed to OPA or hypochlorite. Some HPV virion stocks failed to meet the infectivity criteria of time-dependent detection of E1^E4 mRNAs, resistance to ribonuclease and susceptibility to antibody-mediated neutralization. Such unvalidated virus stocks are likely to produce spurious results and lead to confounding conclusions. Assessment of HPV infectious titers from clinical lesions suggests that compared to common warts, clinical RRP and anogenital warts have lower levels of virions present at apical surfaces. <h3>Conclusions</h3> We conclude that laboratory sourced HPVs are susceptible to disinfection by OPA and hypochlorite. As the levels of infectious virions recovered from HPV-induced lesions fall below those used in our assays, proper cleaning and disinfection processing is likely to be effective