HPV-E7-Specific immune responses in HPV-Infected patiente with precancerous and cancerous cervix

Abstract

Cervical cancer is the second leading cause of cancer deaths in women worldwide. More than 450,000 cases are diagnosed each year. The National Cancer Institute of Thailand reported that the incidence of cervical cancer was the most common among cancers in women. Human papillomavirus (HPV) infection was detected in 99.7% of cancerous cervix. Of the 15 high-risk HPV types isolated from cervical carcinomas, HPV-16 is the most frequently detected, occurring in over 50% of cervical cancers. An etiological and development of cervical cancer were associated with the persistent of high-risk HPV infection and intratypic variation. The variations of HPV genome may effect to virus virulence or divert the biological and biochemical properties. Immune responses to HPV play an important role in protection and controlling HPV infection. However, little is known about HPV-E7-specific CD8+ T cell responses in HPV-infected Thai women. We are interested in exploring the role of HPV-E7-specific immune responses in patients with cervical intraepithelial neoplasia (CIN) and cervical cancer (CaCx). In this study, twenty known HPV-16 DNA samples were identified for E7 variation. Twenty two patients were enrolled from women attending the Gynaecology Clinic at King Chulalongkorn Memorial Hospital, Bangkok, Thailand from August 2003 to June 2004. Eleven patients with CIN and 11 patients with CaCx diagnosed and confirmed by coloposcopically and histopathology were studied HPV-E7-specific CD8+ T cell responses. Five cord blood samples were used as control group in this study. We have designed overlapping peptides that based on HPV-16 E7 Thai variant. The HPV-specific T cell responses were detected by IFN-γ ELISpot assay upon stimulation with E7 overlapping peptides. HPV typing in CIN and CaCx patients were performed on fresh and paraffin-embedded tissues section by L1-PCR-RFLP. Forty seven out of 75 (62,67%) patients were HPV-L1 positive. The prevalence of HPV infections in CIN group was 41.03% and CaCx group was 86.11%. HPV typing was performed by RFLP. HPV-16 was predominant in CIN group (43.75%), whereas HPV-18 was predominant in CaCx group (35.48%). We sequenced HPV-16E7 gene from 20 cases of HPV-16 infected patients and compared them with nucleotide (nt) sequence of HPV-16 reference strain. Most samples had conserved E7 gene. Only 4 out of 20 (20%) samples contained variations. Among these variations, only one non-synonymous was identified at nt 647 (A to G) resulting in a change of HPV-16-E7 amino acid at positive 29 from asparagine to serine (N29S). In HPV immune responses study, we have used overlapping peptides spanning HPV-E7 protein to perform the HPV-E7-specific CD8+T cell responses by ELISpot assays. Unexpectedly, no ex vivo HPV-E7-specific CD8+T cell responses were detected in PBMC of CIN and CaCx patients. We augmented the frequency of the T cell response by “cultured ELISpot assay”. HPV-E7-specific CD8+T cell responses were detected in 27.27% of patients with CIN while only 10% of CaCx patients had the T cell responses. Almost peptides mediated detectable HVP-specific responses in CIN patients, whereas there was one peptide, STHV peptide, was recognized by CaCx patients. The magnitude of responses to E7 peptide in CIN group (1,040-1,640 SFU/106 cells) were greater than that of CaCx groups (188 SFU/106 cells). Our study demonstrated the difference of the HPV-specific T cell responses in CIN and CaCx patients. They did not only target different peptide epitopes, they also had different magnitude of responses. The information obtained from this study will lay the foundation for HHPV vaccine development.