Prevalence of antibodies against a cyclic peptide mimicking the FG loop of the human papillomavirus type 16 capsid among Tunisian women

Abstract

Background In the past decade, the cervical cancer rank went down from the second to the fourth most common cancer in women worldwide but remains ranked second in developing countries. High-risk types of human papillomavirus, mainly type 16, are the sexually transmitted agents etiologically linked to cervical cancer. The present study aimed to investigate the usefulness of a cyclic synthetic peptide designed from the major L1 capsid protein of the HPV16 for detecting anti-HPV16 antibodies. Methods We designed and synthetized a peptide that corresponds to the full sequence of the surface-exposed FG loop. We tested against HPV16 L1 monoclonal antibodies the antigenicity of the linear and the cyclic peptides. Detection of anti-peptide antibodies was assessed by ELISA in sera and cervical secretions of 179 Tunisian women. For HPV DNA detection and genotyping, polymerase chain reaction and direct sequencing methods were applied. Results Both the linear and the cyclic peptides were recognized by the same neutralizing monoclonal antibodies but the cyclic peptide was more reactive with human sera. In contrast to HPV16 DNA prevalence, the prevalence of the anti-peptide antibodies in sera was higher in women with low-grade squamous intraepithelial lesions (LGSIL) than in women with high-grade squamous intraepithelial lesions (HGSIL) (44% and 15%, respectively). Compared to women from the general population, systemic IgG prevalence was significantly higher among sex workers (25%; P=0.002) and women with LGSIL (44%; P=0.001). In addition, systemic IgA and cervical IgG prevalence was higher, only among sex workers (p=0.002 and P=0.001 respectively). We did not observe anti-peptide IgG antibodies in women with a current HPV16 infection.Conclusion Anti-peptide IgG in sera or in cervical secretions could be markers of an effective natural immunization against the HPV16. This may open novel perspective for monitoring vaccinated women and for the design of synthetic peptide-based vaccine.