A competitive serological assay shows naturally acquired immunity to human papillomavirus infections in the Guanacaste Natural History Study.

Background: A competitive Luminex Immunoassay (cLIA) has been developed to measure neutralizing antibodies against human papillomavirus (HPV) types 6, 11, 16 and 18.
Methods: In a cohort of 974 women from the Guanacaste Natural History Study, we studied the relationship of baseline cLIA and virus-like particle (VLP) enzyme-linked immunosorbent assay (ELISA) (HPV16 and HPV18 only) seropositivity to measures of HPV exposure, HPV DNA positivity, number of sexual partners, cytology findings, and age. We then studied immunity against subsequent infection with HPV6, 11, 16, 18 and related types over a 7-year period.
Results: cLIA seroprevalence varied with previous exposure; the prevalence of cLIA results positive for HPV16 and HPV18 was lower than the prevalence of positive VLP ELISA responses. cLIA and VLP ELISA positivity predicted protection from subsequent infections with concordant types. The combined odds ratio for HPV16 and HPV18 cLIA positivity was 0.41 (95% confidence interval [CI], 0.21-0.80), and the combined odds ratio for the HPV16 and HPV18 VLP ELISA positivity was 0.65 (95% CI, 0.46-0.93). Of individual types, statistical significance was only reached for HPV16 cLIA positivity (odds ratio, 0.44; 95% CI, 0.15-0.94).
Conclusions: Both assays showed an association between positive results and significant protection from subsequent infections for HPV16 and HPV18 combined. cLIA seroprevalence was lower than VLP ELISA, suggesting that the assay detects a subset of antibodies following natural infection that are specifically linked to immunity against subsequent HPV infection.