Presence of antibodies to human papillomavirus virus-like particles (VLPs) in 11-13-year-old schoolgirls.

To allow meaningful approaches to vaccine development, it is important to know the extent of exposure to human papillomavirus (HPV) within the general population, and particularly the age at which the at risk population is infected. The humoral response to human papillomavirus is directed largely to conformationally-dependent epitopes on the whole virion. Virus-like particles (VLPs) of HPV types 1, 2, and 16 were produced using a baculovirus expression system, and were used in the intact state as antigen in an indirect ELISA. Anonymised serum samples from a cohort of Edinburgh schoolgirls were tested for the presence of IgG antibodies directed against the VLPs. The reproducibility of the ELISA was assured by repeated testing of control samples, and by testing all samples in duplicate and, where possible, on several occasions. Of 1,192 tested with the HPV16 VLPs, 90 (7.6%) were classified as clearly positive, and a further 87 (7.3%) were positive but close to the cutoff calculated by comparison with a group of consistently negative sera. Antibodies to HPV2 were detected in 37.5% (407/1,139) and antibodies to HPV 1 in 51.9% (558/1,076) of the schoolgirls. Antibodies to both HPV1 and HPV2 were found frequently, being present in 29.7% (295/ 993) of samples tested; 40 samples had antibodies to all three types. The significance of these results is discussed.