Detection of serologic neutralizing antibodies against HPV-11 in patients with condyloma acuminata and cervical dysplasia using an in Vitro assay

This study was designed to investigate if neutralizing antibodies against HPV-11 are detectable in the serum of patients with condyloma acuminata (CA) or cervical intraepithelial neoplasia (CIN) using an in vitro infectivity assay for HPV-11. Purified HPV-11 virions were extracted from xenografted condyloma tissues implanted into athymic mice and used to infect cultured neonatal human foreskin keratinocytes (HFK) and an immortalized adult skin cell line (HaCaT). The presence of HPV-11-specific E1 E4 mRNA as detected by reverse transcriptase-polymerase chain reaction was indicative of early infection. Sera previously characterized for reactivity to HPV-11 and HPV-11 VLP (virus-like particles) by ELISA were tested for the ability to prevent HPV-11 in vitro infectivity. Neutralizing antibodies against HPV-11 were demonstrated when monoclonal antibodies or patient serum preincubated with HPV-11 virions prevented the infection of either of the two cell cultures, as shown by the absence of the E1 E4 mRNA transcript. Eleven (of 20) patients with CA were strongly ELISA reactive against HPV-11 virus-like particles. Five of these 11 patients also had detectable levels of neutralizing antibodies in their serum. It was also demonstrated that the neutralizing properties of the serum were titratable by endpoint dilution. None of 15 patients with CIN had detectable neutralizing antibodies against HPV-11. Neutralizing antibodies against HPV-11 can be detected in some patients with CA and the neutralizing effects of the patient sera can be titrated by endpoint dilution. The in vitro assay for the detection of neutralizing antibodies against HPV-11 may have utility for investigating the natural history of HPV infection and resolution, as well as assessing the efficacy of any putative HPV vaccine.