HPV type 16 protein E7 HLA-A2 binding peptides are immunogenic but not processed and presented

Human papillomaviruses (HPV) have been implicated in the etiology of cervical malignancies and a high percentage of cervical carcinoma cells express HPV-16 E6 and E7 oncoproteins. These proteins are attractive targets for cytolytic T lymphocyte (CTL) mediated immunotherapy. We screened peptides derived from the HPV-16 E7 protein for binding to HLA-A2 and tested their potential to induce specific CTL responses in chimeric HLA-A2/H2-Kb transgenic mice. From eight potential binding peptides four displayed binding and were tested for immunogenicity. CTL activity was tested using target cells pulsed with peptide or expressing E7 protein. While there was no CTL induction observed with the peptides 7-15, 66-74 and 82-90, CTL from mice immunized with 86-93 lysed targets presenting the peptide in the context of the HLA-A2/H2-Kb molecule or wild-type HLA-A2. In contrast, 86-93 induced CTL showed no cytolytic activity against cells expressing the protein E7 and vaccination with the E7 protein did not lead to cytotoxicity against targets pulsed with the 86-93 peptide. Therefore the peptide 86-93, which binds to HLA-A2, is able to induce CTL responses in context of HLA-A2, but the peptide appears not to be processed or presented by HPV type 16 infected cells.     

十肽表位HPV-16E711-20氨基酸置换修饰的研究

目的 采用氨基酸置换对人乳头状瘤病毒16型口抗原的人白细胞抗原A2分子限制性细胞毒性T细胞表位HPV-16E7 11-20进行修饰和鉴定。方法 运用量化模体方案对置换后的多肽与人白细胞抗原A2分子的结合系数进行比较，以分子模拟方法确定合成序列，采用标准Fmoc方案进行合成与纯化多肽以及标准^51 Cr释放试验检测特异性细胞毒性T细胞诱导活性。结果 修饰多肽符合人白细胞抗原A2分子限制性细胞毒性T细胞的表位要求，十肽YLLDLQPEVT具有特异性细胞毒性T细胞诱导活性。结论 修饰表位YLLDLQPEVT具有更好的结合力和较强的抗原性，可以代替原有序列E7 11-20（YMLDLQPEIT）作为人乳头状瘤病毒感染治疗性肽疫苗分子设计的新表位。     

Identification of two homologous antigenic peptides derived from L1 HPV-16 and 18 proteins specific for the HLA-B*3901 allele

Summary.  In this work we present evidence that the homologous peptides IHSMNSTIL and IHSMNSSIL derived from L1 HPV-16 and 18 proteins respectively, and with high specificity for the allele HLA-B^*3901, according with an algorithm prediction program, induced T cell stimulation in patients with advanced cervical cancer positive for HPV-16 or 18 infection and for the HLA-B^*3901 allele. Interestingly, T lymphocytes derived from a patient with HPV-18 infection and stimulated with the peptide IHSMNSTIL were capable to kill a cervical cancer cell line named Rova, derived from the tumor of the same patient. In addition, the cytotoxic activity was strongly increased when this cell line was previously treated with hrIFN-γ. These results suggest that the CTL immune response to L1 HPV-16 and 18 protein derived epitopes is maintained in patients with advanced cervical cancer within specific alleles, and opens the possibility that homologous epitopes may be used in the generation of prophylactic vaccines for cervical tumors bearing different HPV-types. Received March 4, 2002; accepted May 20, 2002     

Combined structural and immunological refinement of HIV-1 HLA-B8-restricted cytotoxic T lymphocyte epitopes

This study demonstrates that use of structural information improves the definition and optimization of cytotoxic T lymphocyte (CTL) epitopes. Epitope optimization usually requires numerous truncated peptides or a reverse immunogenetic approach, where the peptide binding motif is used to predict epitopes. These binding motifs do not reliably predict all peptides which are CTL epitopes. Comparison of 24 peptides eluted from HLA-B8 with 10 HLA-B8-restricted defined CTL epitopes demonstrated that known epitopes varied considerably at anchor positions. We used structural information based on determination of the crystal structure of the HLA-B8-GGKKKYKL complex to reassess previously described CTL epitopes, to predict new epitopes, and to predict the consequences of naturally occurring variation within epitopes. These predictions were confirmed by cytotoxicity and binding assays. Use of combined structural and immunological data more accurately defines the true peptide-binding motif of a restriction element than eluted peptide data allows.     

Relationship between peptide binding and T cell epitope selection: a study with subtypes of HLA-B27

The effect of HLA-B27 polymorphism on antigen presentation was analysed by comparing the binding of three Epstein-Barr virus-derived peptide epitopes to HLA-B27 subtypes with their immunogenicity and antigenicity in the context of these subtypes. The effect of altering the major anchor residue Arg2 on binding or on recognition by peptide-specific cytotoxic T lymphocytes (CTL) was also examined. The three peptides bound significantly to all the B*2701-B*2706 subtypes. This did not correlate with the peptides being immunogenic or recognized by specific CTL in the context of only particular subtypes. In addition, of the three viral epitopes tested, those that were immunogenic in B*2702- or B*2705-restricted responses bound to these subtypes less efficiently than one peptide that was immunogenic only in the B*2704 context. Thus, among several potentially immunogenic peptides from the same virus, the antiviral response is not necessarily directed against the one that binds best to the restricting subtype. These results indicate that HLA- B27 polymorphism influences antigen presentation in ways other than simply peptide affinity. Synthetic analogues lacking the canonical Arg2 motif of HLA-B27-bound peptides, even when binding much worse to the restricting subtype, were recognized equally by CTL specific for the parental peptide. This indicates that Arg2 is not required to maintain the structure of the epitope. The implications of these results for pathogenetic models of HLA-B27-associated disease are discussed.      

Comparison of peptide enzyme-linked immunosorbent assay and radioimmunoprecipitation assay with in vitro-translated proteins for detection of serum antibodies to human papillomavirus type 16 E6 and E7 proteins.

Antibodies to human papilloma virus (HPV) type 16 (HPV-16) E6 and E7 proteins in serum are markers for HPV-associated invasive cervical carcinoma. We compared two assays, a radioimmunoprecipitation assay with in vitro-translated HPV-16 E6 and E7 proteins and an enzyme-linked immunosorbent assay (ELISA) with E6 and E7 synthetic peptides, for their abilities to discriminate serologically between patients with invasive cervical cancer and controls. Among the patients, antibody prevalences were higher by the E6 radioimmunoprecipitation assay (55.7%) than by the E6 peptide ELISA (15.5%), but among the controls, they were lower by the radioimmunoprecipitation assay (1.7%) than by the E6 peptide ELISA (5%). For E7, antibody prevalences among the patients were comparable by the radioimmunoprecipitation assay (43%) and the peptide ELISA (41%), but among the controls they were higher by the E7 peptide ELISA (17.4%) than by the radioimmunoprecipitation assay (4.1%). There was good agreement between the E7 radioimmunoprecipitation assay and the E7 peptide ELISA among patients but not among controls. In tests with representative sera, heat denaturation of the translated proteins resulted in a complete loss of reactivity to the E6 protein and a marked decrease in reactivity to the E7 protein. Our study showed that the radioimmunoprecipitation assay discriminates better than the peptide ELISA between patients with invasive cervical cancer and controls and that this is related to the ability of the radioimmunoprecipitation assay to detect conformational epitopes.     

Human papillomavirus type 18 E6 and E7 antibodies in human sera: increased anti-E7 prevalence in cervical cancer patients.

Antibody-reactive regions on the human papillomavirus type 18 (HPV-18) E6 and E7 proteins were identified with rabbit polyclonal anti-fusion protein sera by screening of an fd phage expression library containing subgenomic HPV-18 DNA fragments and by testing of overlapping decapeptides representing the E6 and E7 open reading frames. Peptides comprising the delineated regions (designated E6/1 to E6/4 and E7/1) were synthesized and used in an enzyme-linked immunosorbent assay (ELISA) to detect anti-HPV-18 antibodies in human sera. A total of 232 human serum samples (identical numbers of cervical cancer patients and age-matched controls) collected in Tanzania were tested. Similar prevalences (between 0.8 and 4.3%) of antibodies recognizing the different E6 peptides were found in the sera from tumor patients and controls. With a synthetic 28-mer peptide (designated pepE701) comprising the E7/1 region, a significant difference was found: 10 of 116 tumor serum samples but 0 of 116 control serum samples showed a specific reaction (P less than 0.001). This observation confirms earlier results with HPV-16 E7 fusion proteins (I. Jochmus-Kudielka, A. Schneider, R. Braun, R. Kimmig, U. Koldovsky, K. E. Schneweis, K. Seedorf, and L. Gissmann, J. Natl. Cancer Inst. 81:1698-1704, 1989). A lower prevalence of anti-HPV-18 E7 antibodies was observed when 188 human serum samples collected in Germany from tumor patients and controls were tested (3 of 94 positive in the cancer group; 0 of 94 positive in the control group). The type specificity of anti-HPV-18 E7 antibodies was demonstrated when the HPV type found by Southern hybridization in the cervical cancer biopsies was compared with seroreactivity: 4 of 8 serum samples obtained from HPV-18 DNA-positive but 0 of 16 serum samples from HPV-18 DNA-negative tumor patients reacted in the HPV-18 E7 ELISA. In addition, HPV-18-positive sera failed to react in a peptide ELISA with the homologous HPV-16 E7 region (M. Müller, H. Gausepohl, G. de Martinoff, R. Frank, R. Brasseur, and L. Gissmann, J. Gen. Virol. 71:2709-2717, 1990) and vice versa.     

Antibodies to HPV-16 E6 and E7 proteins as markers for HPV-16-associated invasive cervical cancer.

Transforming proteins E6 and E7 of human papillomaviruses (HPVs) are consistently expressed in HPV-associated cervical cancers. In ELISA with four HPV-16 E6-E7 peptides, patients with HPV-16-associated invasive cervical cancer (group 1) had a greater seroreactivity than all other groups, which included patients with HPV-16-associated cervical intraepithelial neoplasia, invasive cervical cancer patients without HPVs, and unaffected controls. A larger proportion of group 1 sera, as compared to sera of all other groups, was reactive with at least one peptide (49% vs 17-27%), and with two or more peptides (22% vs 0-6%). A clear difference between group 1 and all other groups was also found for high ELISA absorbance values to at least one peptide (22% vs 0-8%). This high seroreactivity of group 1 sera was confirmed by a radioimmunoprecipitation assay with in vitro transcribed and translated HPV-16 E7 protein. Sera from 50% of group 1 but only 3% of controls were reactive in this test. Antibodies to HPV-16 E6 and E7 proteins appear to be virus-specific and disease state-specific markers of HPV-associated cervical cancer.     

Identification of multiple HIV-1 CTL epitopes presented by HLA-B*5101 molecules.

We attempted to identify and characterize HIV-1 CTL epitopes presented by HLA-B51 which is associated with a slow progression to AIDS. HLA-B*5101 stabilization assay showed that 33 out of 172 HIV-1 peptides carrying HLA-B*5101 anchor residues bound to HLA-B*5101. Seven peptides were suggested as HIV-1 CTL epitopes presented by HLA-B*5101 because the specific CTL was induced for these peptides in PBMC from three HIV-1 seropositive individuals carrying HLA-B51 by stimulation with HLA-B*5101 binding peptides. Analysis of these epitopes using the specific CTL clones confirmed that six of seven HIV-1 peptides are epitopes presented by HLA-B*5101. Three epitopes presented by HLA-B*5101 are highly conserved among the clade B strain, suggesting that the specific CTL for these epitopes might play an important role in recognition of HIV-1 infected cells. These epitopes will be useful to analyze CTL responses in HIV-1 infected individuals.     

Predominance of serum antibodies to synthetic peptide stemming from HPV 18 open reading frame E2 in cervical adenocarcinoma.

AIMS: To determine if there are type specific differences in serum antibody responses to synthetic peptides derived from human papillomavirus (HPV) open reading frame (ORF) E2 in patients with cervical carcinoma. METHODS: Diagnostic phase sera from 88 age-matched women with cervical adenocarcinoma (AC), cervical squamous cell carcinoma (SC), ovarian cancer (OC) or no gynaecological malignancy were available. Serum IgG and IgA antibodies to synthetic peptides corresponding to a residue of HPV 6, 11, 16, and 18 ORF E2 18 amino acids long and a control peptide from mumps virus were determined by ELISA. RESULTS: Both IgA and IgG antibody positivity to the HPV 18 peptide were associated with increased risk (9.0-fold, confidence limits 1.5-199) for AC. IgA positivity to HPV 11, 16, and 18 peptides was associated with an increased risk for SC. However, the association of IgG antibodies to HPV 16 peptide with SC was not significant. IgA or IgG antibodies to HPV 6 or mumps virus peptides were not associated with increased risk for AC, SC, or OC. CONCLUSIONS: These results suggest a specific role for HPV 18 in AC. Differences in antibody responses to HPV peptide in AC and SC suggest immunopathogenetic differences between the two types of cervical carcinoma.     

Different methods of identifying new antigenic epitopes of human papillomavirus type 16 E6 and E7 proteins

Human papillomavirus (HPV) infection is the most common cause of sexually transmitted viral infection and is the main cause of cervical cancer. Identification of HPV T-cell epitopes would be instrumental not only in our understanding of the protective immune response but also in the development of vaccines and immunotherapies. In contrast to viruses which cause systemic infection, identification of HPV epitopes is technically challenging because HPV causes a localized mucosal infection and the frequency of pathogen-specific T lymphocytes in peripheral blood is expected to be low. Here we describe three new antigenic epitopes (E7 7-15 [TLHEYMLDL], E6 52-61 [FAFRDLCIVY], and E7 79-87 [LEDLLMGTL]) of HPV 16 E6 and E7 proteins which have oncogenic activities. E7 7-15 was identified among peptides previously shown to bind to human leukocyte antigen (HLA)-A2.1 molecule, but it was found likely to be restricted by the HLA-B48 molecule. E6 52-61 (likely to be restricted by HLA-B57) and E7 79-87 (likely to be restricted by HLA-B60) were detected, based on the magnitude of the T-cell immune responses, in another individual. In particular, T-cell clones specific for the E6 52-61 epitope were isolated effectively by magnetically selecting them based on gamma interferon secretion. This is an efficient method of identifying new epitopes of antigens for which the number of specific T lymphocytes in the circulation is expected to be small, and it should be widely applicable in identifying new T-cell epitopes.     

Different Methods of Identifying New Antigenic Epitopes of Human Papillomavirus Type 16 E6 and E7 Proteins

Human papillomavirus (HPV) infection is the most common cause of sexually transmitted viral infection and is the main cause of cervical cancer. Identification of HPV T-cell epitopes would be instrumental not only in our understanding of the protective immune response but also in the development of vaccines and immunotherapies. In contrast to viruses which cause systemic infection, identification of HPV epitopes is technically challenging because HPV causes a localized mucosal infection and the frequency of pathogen-specific T lymphocytes in peripheral blood is expected to be low. Here we describe three new antigenic epitopes (E7 7-15 [TLHEYMLDL], E6 52-61 [FAFRDLCIVY], and E7 79-87 [LEDLLMGTL]) of HPV 16 E6 and E7 proteins which have oncogenic activities. E7 7-15 was identified among peptides previously shown to bind to human leukocyte antigen (HLA)-A2.1 molecule, but it was found likely to be restricted by the HLA-B48 molecule. E6 52-61 (likely to be restricted by HLA-B57) and E7 79-87 (likely to be restricted by HLA-B60) were detected, based on the magnitude of the T-cell immune responses, in another individual. In particular, T-cell clones specific for the E6 52-61 epitope were isolated effectively by magnetically selecting them based on gamma interferon secretion. This is an efficient method of identifying new epitopes of antigens for which the number of specific T lymphocytes in the circulation is expected to be small, and it should be widely applicable in identifying new T-cell epitopes.     

Identification of peptides presented by HLA class I molecules on cervical cancer cells with HPV-18 infection.

In this work we eluted peptides from purified class I MHC molecules, isolated from a novel human cervical carcinoma cell line (INBL), generated in our laboratory and positive for HPV-18 infection. A fraction of these peptides was capable of stimulating T lymphocytes obtained from a donor matched for HLA-Cw4 and who was also HPV-18+. Direct N-terminal Edman degradation of these peptides, revealed the sequence (XQFPIFLQF) that matched 85% with the sequence NVFPIFLQM localized in between the 54 and 62 residues of the HPV-18 L1 protein. After stimulation with the synthetic peptide NVFPIFLQM, T lymphocytes from the donor were capable to lyse INBL cells. Our results provide evidence of the existence of naturally occurring viral epitopes presented on cervical cancer cells by the HLA-Cw4 allele, that could be useful for immunotherapy on this type of patient.     

Novel oligomannose liposome-DNA complex DNA vaccination efficiently evokes anti-HPV E6 and E7 CTL responses

The aim of this study was to establish an efficient human papilloma virus (HPV) type 16-targeting cancer immunotherapy. Persistent high-risk HPV infection causes cervical intra-epithelial neoplasia (CIN) and subsequent cervical carcinoma. HPV type16 (HPV16) is one of the common carcinogenic types and is found in about 50% of invasive cervical carcinomas. HPV16-derived viral proteins E6 and E7 are expressed in cancerous cells through the progression of the disease and have a role in carcinogenesis but are not expressed in normal cells. Thus, these proteins are regarded as ideal antigens for cervical carcinoma immunotherapy. In this study, we generated a novel HPV 16 E6 and E7 gene plasmid containing oligomannose liposomes (OML-HPV). We compared the cytotoxic T lymphocyte (CTL) induction efficiency of OML-HPV and that of standard liposome-HPV16 E6 and E7 DNA complex. HPV16 E6-specific CTLs could be generated from HPV 16-positive cervical carcinoma patient's peripheral blood mononuclear cells (PBMCs) by stimulating OML-HPV, but could not by stimulating standard liposome-HPV 16 E6, E7 DNA complex. Furthermore, we screened HLA-A24-restricted HPV16 E6- and E7-derived peptides, and found that one E6-derived peptide (E6 66-74) showed the highest immunogenicity with ELISPOT assay from 100% of HPV16-positive patients (4 out of 4). On the other hand, other E6- or E7-derived peptides, including E6 49-57, E6 82-90, E6 87-95, E6 98-106 and E7 83-93, showed less frequent reactivity. These results indicate that OML-HPV is a more effective approach than DNA vaccination using standard liposomes, and that a novel HLA-A24-restricted peptide, E6 66-74, might be a suitable target of cervical cancer immunotherapy.     

CD4+ T cell immunity against the human papillomavirus-18 E6 transforming protein in healthy donors: identification of promiscuous naturally processed epitopes

Infection by 'high-risk' human papillomaviruses (HPV) is associated with the development of neoplastic lesions. HPV-18 is responsible for a very aggressive form of cancer and poor survival. As for other HPV types, immune surveillance has probably a role in the control of the infection. However, very little is known on HPV-18 immunogenicity. CD4(+) T cells from 16 healthy donors were tested ex vivo for reactivity to synthetic peptides corresponding to 3 sequences on the HPV-18 E6 transforming protein predicted by bioinformatics as promiscuous HLA-DR ligands, and to the recombinant E6 protein. We found 3 donors with CD4(+) T cells that specifically proliferated in the presence of HPV-18 E6 antigens and produced IFN-gamma in the presence of the E6 protein. We then propagated CD4(+) T cell lines and clones from the responsive subjects to better characterize the recognized sequences. We show that E6(52-66) and E6(97-111) are indeed promiscuous and, most importantly, they contain naturally processed epitopes. Collectively, our data indicate that healthy donors may develop spontaneous CD4 immunity against HPV-18 E6 epitopes, thus strongly suggesting the potential for this protein to elicit in the host a natural productive immune response.     

T-Cell Response to Human Papillomavirus Type 58 L1, E6, and E7 Peptides in Women with Cleared Infection,Cervical Intraepithelial Neoplasia,or Invasive Cancer

Human papillomavirus type 58 (HPV-58) exists in a relatively high prevalence in certain parts of the world, including East Asia. This study examined the T-cell response to HPV-58 L1, E6, and E7 peptides among women with cleared infection, cervical intraepithelial neoplasia grade 2 (CIN2) or CIN3, or invasive cervical cancer (ICC). Peptides found to be reactive in the in vitro peptide binding assay or mouse-stimulating study were tested with a gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) assay to detect peptide-specific responses from the peripheral blood mononuclear cells (PBMC) collected from 91 HPV-58-infected women (32 with cleared infection, 16 CIN2, 15 CIN3, and 28 ICC). Four HLA-A11-restricted HPV-58 L1 peptides, located at amino acid positions 296 to 304, 327 to 335, 101 to 109, and 469 to 477, showed positive IFN-γ ELISPOT results and were mainly from women with cleared infection. Two HLA-A11-restricted E6 peptides (amino acid positions 64 to 72 and 94 to 102) and three HLA-A11-restricted E7 peptides (amino acid positions 78 to 86, 74 to 82, and 88 to 96) showed a positive response. A response to E6 and E7 peptides was mainly observed from subjects with CIN2 or above. One HLA-A2-restricted E6 peptide, located at amino acid position 99 to 107, elicited a positive response in two CIN2 subjects. One HLA-A24-restricted L1 peptide, located at amino acid position 468 to 476, also elicited a positive response in two CIN2 subjects. In summary, this study has identified a few immunogenic epitopes for HPV-58 E6 and E7 proteins. It is worthwhile to further investigate whether responses to these epitopes have a role in clearing an established cervical lesion.Infection with high-risk human papillomaviruses (HPV) is a necessary cause for cervical cancer (14, 21, 33). Of the more than 40 HPV types that can infect the female genital tract, at least 15 have been shown to be associated with an increased risk for cancer development (21), and HPV type 16 (HPV-16) and HPV-18 account for more than 70% of cervical cancers detected worldwide (6, 10, 28). Currently, two vaccines have been approved for clinical use to prevent HPV infection and its potential consequences of developing cervical intraepithelial neoplasia (CIN) and invasive cervical cancer (ICC) (27). Both vaccines are prophylactic and contain HPV-16 and HPV-18 L1 protein-based virus-like particles. To date, the development of therapeutic vaccines has been restricted to early-phase clinical trials, and none has been approved for clinical use. HPV-specific cytotoxic cellular immunity against the E6 and E7 proteins that are consistently expressed in cervical neoplasia is important in clearing the established lesions. The results of initial studies using in vitro and in vivo models demonstrated that viral peptides were able to stimulate murine cytotoxic T-lymphocytes, and these peptides were also able to stimulate human cytotoxic T-lymphocytes against HPV-positive cervical cell lines (1, 13, 25). These findings have led to the search for peptides that can elicit or augment an HPV-specific cytotoxic cellular response from patients who have developed preinvasive or invasive cervical neoplasia (4, 29, 35). While HPV-16 and HPV-18 are the most prevalent HPV types found in cervical cancers detected worldwide, HPV-58 has been found at a relatively higher frequency in East Asia (5, 7). Currently, data on T-cell response to HPV-58 peptides are not available; therefore, the aim of this study was to characterize the T-cell response against peptides derived from the L1, E6, and E7 proteins of HPV-58 among women with cleared infection or cervical neoplasia.     

Structure of HLA-B27-specific T cell epitopes. Antigen presentation in B2703 is limited mostly to a subset of the antigenic determinants on B2705

The structure of HLA-B27-specific epitopes recognized by anti-B*2705 and anti-B*2703 cytotoxic T lymphocytes (CTL) from three unrelated donors was examined with site-specific mutants at various side-chain pockets in the antigen-binding site. The effect of any given mutation on allorecognition correlated strongly with its predictable effect on peptide binding. Acidic charges in the C/F pocket of HLA-B27, which binds C-terminal peptide residues, strongly modulated allorecognition. Anti-B*2705 CTL from different donors were differently affected by some mutations, indicating individual differences in the structure of epitopes recognized by alloreactive CTL from each donor. Most anti-B*2703 CTL recognized a subset of epitopes that were also present on B*2705, but differed from the bulk of allospecific epitopes on this subtype in their smaller dependence on pocket A structure, where the difference between these subtypes is located, and in their greater dependence on Glu45, in the B pocket. The structure of the very few epitopes on B*2703 not shared by B*2705 was quite different from that of the much more predominant cross-reactive epitopes. The results strongly suggest that B*2703 is antigenically defective as compared with B*2705 and that this is due to the fact that the repertoire of peptides presented by B*2703 consists mainly of a subset of the B*2705-bound peptides which do not critically require the canonic binding of the peptidic N-terminus to a B*2705-like A pocket, because they are sufficiently stabilized by other contacts through the peptide binding site.     

The prevalence of HPV-18 and variants of E6 gene isolated from cervical cancer patients in Taiwan.

BACKGROUND: Cervical cancer is the second most common cancer in women worldwide. It has been considered that human papillomavirus (HPV) is associated with cervical cancer. Currently, more than 80 different serotypes of HPV have been characterized and they are divided into low- and high-risk groups. The most common types that lead to cervical cancer are HPV-16 and -18. The viral oncogenes E6 and E7 are associated with the development of cervical cancer. In previous study, the variants of HPV-16 E6 gene have been reported. It suggests that variants may influence the morbidity of carcinogenesis, but the variant study on HPV-18 remains unknown. OBJECTIVES: To identify the variants of integrated HPV-18 E6 gene in the prevalent infection of HPV-18 of cervical cancer patients. STUDY DESIGN: 25 cervical cancer patients were clinically identified and the biopsies were obtained. The infectious HPV types were identified by PCR and Southern blotting analysis. The DNA fragments of the integrated HPV-18 E6 were amplified by PCR and cloned. The nucleotide sequences were obtained by sequencing. RESULTS: The prevalence of HPV infection in our 25 cases was HPV-18 (100%) and 7 out of these 25 cases (28%) were co-infected with HPV-16. The most dominant mutation among 25 tested patients was a silence mutation C183G of the E6 coding region. CONCLUSIONS: The prevalent HPV infectious serotype is HPV-18, which differs from the worldwide prevalent type. The identified HPV-18 E6 variants had a unique silence mutation located on C183G in E6 coding region.     

HPV16E7抗原HLA-A2限制性CTL表位预测及其合成

目的：预测、合成、纯化及鉴定人乳头瘤病毒E7抗原的HLA－A2限制性细胞毒性T淋巴细胞表位，为表位抗原特异性鉴定和临床研究提供靶肽。方法：采用超模体、多项式和量化模体方案相结合的方法，对靶抗原HPV16E7的HLA－A2限制性细胞毒性T淋巴细胞（Cytotoxic T lymphocyte,CTL)表位进行预测，并运用固相合成法合成多肽，经RP－HPLC纯化及纯度分析，用质谱进行定性鉴定。结果：分别预测出了16个、10个和3个九肽表位，确定其中5个九肽为候选合成表位，各合成肽的纯度都在95％以上。经质谱分析，各肽的分子量测定值与理论值相符。结论：超模体、多项式和量化模体方案联合应用可提高预测效率，避免了在研究E7抗原表位时盲目合成多肽；所合成的多肽为高纯度靶肽，可用于后续实验研究。     

Identification of H-2Kb Binding and Immunogenic Peptides from Human Papilloma Virus Tumour Antigens E6 and E7

Peptides can be used to induce MHC class I restricted cytotoxic T cells (CTL) tbrough in vivo immunization. This approach may enable the development of peptide vaccination schemes for immunization against viral infection in humans. Human papillomavirus (HPV) is one of a few viruses associated with human cancer and the development of an anti-cancer vaccine seems possible. As a model approach, we searched the E6 and E7 proteins of the human papillomavirus type 16 for possible murine MHC class I restricted peptide epitopes. We utilized the mouse H2-K^b peptide binding motif which consists of phenylalanine or tyrosine at position five and leucine at the carboxy-terminus with the modification that leucine could be replaced by other aliphatic but non-aromatic amino acids. Four peptide sequences from E6 and two from E7 were selected. These peptides were tested for their ability to bind and stabilize K^b and for their immunogenicity in vivo . It was shown tbat one peptide from E6, E6.1 (50–57), bound K^b, but was not able to prime mice in vivo . In contrast, the two selected E7 peptides E7.1 (21–28) and E7.2 (48–55) bound K^b and were immunogenic in vivo . The peptide induced CTL lysed syngeneic EL-4 cells transfected with the open reading frame of E7 but not vector only transfectants. This implies tbat both peptides were naturally processed and presented by K^b on the surface of target cells. MHC class I peptide binding motifs therefore appear to be an effective and useful tool to predict peptide epitopes of proteins associated with cancer.