Detecting human papillomavirus in ocular surface diseases

Human papillomavirus (HPV) infection has been implicated as a possible inducing factor for benign and neoplastic ocular surface diseases such as pterygia and ocular-surface squamous neoplasia (OSSN). However, the wide range in HPV prevalence previously reported for both diseases adds controversy to, and highlights the limitations of, this field. The aim of this study was to determine the prevalence of HPV in pterygia and OSSN and to devise a standardized approach for detecting viral DNA in ocular tissue samples.

DNA was extracted from a variety of specimens (n = 160), including formalin-fixed paraffin-embedded tissue shavings, fresh tissue, and cultured cells. Nested PCR for HPV with consensus and subtype-specific primers was used to detect viral DNA. Confirmatory assays, including molecular sequencing, histology, and immunohistochemistry for HPV E6 protein and p16 were also performed.

HPV was not detected in pterygia or normal conjunctiva. However, 6.5% (3/46) of OSSN samples were HPV-positive by PCR, sequencing, and immunohistochemistry. Positive cases were all squamous cell carcinoma of the conjunctiva (SCCC), the most severe form of OSSN, representing 12.5% (3/24) of SCCCs in our cohort. HPV-16 was the genotype identified in each case and this correlated with the presence of koilocytes and intense immunoreactivity for p16. Our study found no association between pterygia and OSSN with other oncogenic viruses, such as EBV or CMV, as they were just as prevalent in normal conjunctiva.

The low prevalence of HPV-16 in ocular surface disease suggests infection is not a cause but a cofactor in disease development.