Antibodies against the human papillomavirus type 16 early proteins in human sera: correlation of anti-E7 reactivity with cervical cancer

HPV types 16/18 L1 E6 and E7 proteins seropositivity and cervical cancer risk in HIV-positive and HIV-negative black South African women

Background

In populations with high rates of human immunodeficiency virus (HIV)-coinfection, the nature of the relationship between human papillomavirus (HPV)-16 and -18 (L1, E6 and E7) antibodies and cervical cancer is still uncertain. We measured the association between seropositivity to HPV (L1, E6 and E7) proteins and cervical cancer among black South African women with and without HIV co-infection.

Methods

We used questionnaire data and serum collected from consecutively recruited patients with a newly diagnosed cancer from the Johannesburg Cancer Study from 1346 cervical cancer cases and 2532 controls (diagnosed with other non-infection related cancers). Seropositivity to HPV proteins was measured using a multiplex serological assay based on recombinant glutathione S-transferase (GST) fusion proteins. We measured associations between their presence and cervical cancer using unconditional logistic regression models and evaluated the sensitivity and specificity of these HPV biomarkers.

Results

Among controls, HIV-negative women from rural areas compared to urban had significantly higher HPV seroprevalence, HPV16 E7 (8.6% vs 3.7%) and HPV18 E7 (7.9% vs 2.0%). HPV16 E6 and E7 antibodies were positively associated with cervical cancer in HIV-positive (Adjusted Odds Ratio (AOR) = 33; 95% CI 10–107) and HIV-negative women (AOR = 97; 95% CI 46–203). In HIV-positive women, HPV E6/E7 antibodies had low sensitivity (43.0%) and high specificity (90.6%) for cervical cancer detection. In HIV-negative women, HPV E6/E7 antibodies sensitivity was 70.6% and specificity was 89.7%.

Conclusions

Our data show that HPV (L1, especially E6 and E7) antibody positivity is associated with cervical cancer in both HIV-positive and HIV-negative women. Nonetheless, being HIV-positive plays an important role in the development of cervical cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-022-00418-2.

Protection against human papillomavirus type 16-induced tumors in C57BL/6 mice by mucosal vaccination with Lactococcus lactis NZ9000 expressing E6 oncoprotein

Recombinant strains of Lactococcus lactis NZ9000 that express native and codon-optimized E6 protein (fused to the SPusp45 secretion signal) were successfully constructed by using the nisin-controlled gene expression (NICE) system. Expression of the recombinant strains was evaluated by Western blot analysis. Female mice of strain C57BL/6 were immunized orally with recombinant lactococci expressing inducible E6 oncoprotein and the antigen-specific antibody production (IgA and IgG) and cytokines were measured by ELISA and ELISPOT assay, respectively. Our outcomes indicate that the HPV-16 E6 specific IL-2- and IFN-γ-secreting lymphocytes in the antigen-stimulated intestinal mucosal lymphocytes, splenocytes and vaginal lymphocytes were significantly higher than the control groups. We showed that L. lactis having codon-optimized E6 oncogene had better inhibitory effect on tumor growth, better treatment effects on progression of tumor size, and better survival rate in comparison with L. lactis having native E6 oncogene, (P < 0.0001). In conclusion, the rE6 protein displayed by L. lactis can induce humoral and cellular immunity. Taken together, these preclinical results represent a promising step towards the development of recombinant L. lactis as a live oral vector vaccine to treat the HPV-16 associated with cervical cancer.

Role of Immune Response in the Prognosis of Carcinoma of the Uterine Cervix: Can in Vitro Analysis Provide a better Framework for more Effective Management?

Cancer of the uterine cervix is the single largest female malignancy in India and also remains a major problem facing oncologists in other parts of the world. While advances in radiation therapy and surgical techniques have made the treatment of cervical carcinoma impressive, limitations to successful management still remain. In fact, the 5-year survival rate, stage for stage, has not improved in the United States or world wide in the past 40 years. With an estimated half a million women developing this disease annually, this lack of improved survival poses an international unresolved health problem. Immune response has been shown to be a major factor involved In the course of the disease for this cancer. Immunologic monitoring was also shown to be of effective value in assessing the prognosis for cervical carcinoma. We studied the various immunologic abnormalities in cervical cancer, the effects of radiation therapy on immune function, prospects of an immunologic staging system, the relationship between human papillomavirus infection and the Immune response, and the possibility of using in vitro Immunologic assessment to provide a better framework for more effective management of cancer of the uterine cervix.

Validation of Serological Antibody Profiles Against Human Papillomavirus Type 16 Antigens as Markers for Early Detection of Cervical Cancer

Cervical cancer (CC) is the second most frequent neoplasia among women worldwide. Cancer prevention programs around the world have used the Papanicolaou (Pap) smear as the primary diagnostic test to reduce the burden of CC. Nevertheless, such programs have not been effective in developing countries, thus leading to research on alternative tests for CC screening. During the virus life cycle and in the process toward malignancy, different human papillomavirus (HPV) proteins are expressed, and they induce a host humoral immune response that can be used as a potential marker for different stages of the disease. We present a new Slot blot assay to detect serum antibodies against HPV16 E4, E7, and VLPs-L1 antigens. The system was validated with sera from a female population (n = 485) aged 18 to 64 years referred to the dysplasia clinic at the General Hospital in Cuautla, Morelos, Mexico. To evaluate the clinical performance of the serological markers, the sensitivity, specificity, positive, and negative predictive values and receiver-operating characteristic curves (for antibodies alone or in combination) were calculated in groups of lesions of increasing severity. The results showed high prevalence of anti-E4 (73%) and anti-E7 (80%) antibodies in the CC group. Seropositivity to 1, 2, or 3 antigens showed associations of increasing magnitude with CC (odds ratio [OR] = 12.6, 19.9, and 58.5, respectively). The highest association with CC was observed when the analysis was restricted to only anti-E4+E7 antibodies (OR = 187.7). The best clinical performance to discriminate CC from cervical intraepithelial neoplasia 2 to 3 was the one for the combination of anti-E4 and/or anti-E7 antibodies, which displayed high sensitivity (93.3%) and moderate specificity (64.1%), followed by anti-E4 and anti-E7 antibodies (73.3% and 80%; 89.6% and 66%, respectively). In addition, the sensitivity of anti-E4 and/or anti-E7 antibodies is high at any time of sexual activity (TSA), which suggests they can be biomarkers for the early detection of CC. The sensitivity of anti-E4 antibodies was low (<10%) when the TSA was <10 years, and it increased up to 100% in relation to the TSA, suggesting that anti-E4 antibodies can be useful as HPV exposure markers at early stages of the disease.

Humoral Immune Response Against Human Papillomavirus as Source of Biomarkers for the Prediction and Detection of Cervical Cancer

Cervical cancer (CC) is one of the main causes of death among women of reproductive age. Although there are different tests, the disease tends to be diagnosed at late stages. In recent years, the use of complementary tests or sequential diagnostic tests has been implemented. Nevertheless, the results are variable and not conclusive; therefore, more studies for improving the usefulness of these tests in diagnostics are necessary. The human papillomavirus (HPV) infection has been associated with both benign and malignant proliferation of skin and mucosal tissues. Furthermore, some HPV types have been classified as high risk due to their potential to cause cancer, and HPV16 is most frequently associated with this disease. Although between 70% and 80% of precancerous lesions are eliminated by the host's immune system, there is no available test to distinguish between regressive lesions from those that could progress to CC. An HPV infection generates a humoral immune response against L1 and L2 capsid proteins, which can be protective and a response against early proteins. The latter is not a protective response, but these antibodies can be used as markers to determine the stage of the infection and/or the stage of the cervical lesion. Up to now, the humoral immune response resulting from the HPV infection has been used to study the biology of the virus and the efficacy of the HPV vaccines. Although there are no conclusive results regarding the use of these antibodies for diagnosis, we hereby review the actual panorama of the antibody response against the HPV proteins during the development of the disease as well as their possible use as biomarkers for the progression of cervical lesions and of CC.

HPV vaccines: Translating immunogenicity into efficacy

Currently available human papillomavirus (HPV) vaccines are very successful at preventing persistent HPV infection and premalignant cervical lesions. In part due to the unique aspects of HPV immunogenicity and high levels of efficacy no immune correlate has been identified for HPV vaccination. Serum neutralizing antibodies are used to measure vaccine response, but their role as a correlate has not been verified, and this theory fails to explain the prevention of HPV related non-mucosal lesions. Identifying a true correlate would aid in future work in this area but will be difficult in the setting of a highly efficacious vaccine.

A lectin-based diagnostic system using circulating antibodies to detect cervical intraepithelial neoplasia and cervical cancer

In the present study, we developed serological strategies using immunoglobulin fractions obtained by protein A chromatography to screen for cervical cancer and cervical intraepithelial neoplasia I (CIN I). The reactivities of the immunoglobulins purified from sera of women with normal cytology, CIN I and cervical cancer were compared in enzyme-linked immunosorbent assays (ELISA) and enzyme-linked lectin assays (ELLAs). To capture the immunoglobulins, ELISAs and ELLAs were performed in protein A immobilized microplates. The reactivity of immunoglobulin in ELISA was in the increasing order normal cytology, CIN I and cervical cancer, while that in ELLAs for detecting fucosylation was in the decreasing order normal cytology, CIN I and cervical cancer. It was confirmed that women with CIN I were distinguishable from women with normal cytology or women with cervical cancer in the ELISA or the ELLA for detecting fucosylation with considerable sensitivity and specificity. Women with cervical cancer were also distinguishable from women with normal cytology with high sensitivity (ELISA: 97%, ELLA: 87%) and specificity (ELISA: 69%, ELLA: 72%). Moreover, the logistic regression model of the ELISA and the ELLA discriminated cervical cancer from normal cytology with 93% sensitivity and 93% specificity. These results indicate that the ELISAs and the ELLAs have great potential as strategies for primary screening of cervical cancer and CIN. It is expected that the ELISA and the ELLA can provide new insights to understand systemic changes of serum immunoglobulins during cervical cancer progression.

Antibodies against high-risk human papillomavirus proteins as markers for invasive cervical cancer

Different human papillomavirus (HPV) genes are expressed during the various phases of the HPV life cycle and may elicit immune responses in the process towards malignancy. To evaluate their association with cervical cancer, antibodies against proteins from HPV16 (L1, E1, E2, E4, E6 and E7) and HPV18/31/33/35/45/52/58 (L1, E6 and E7) were measured in serum of 307 invasive cervical cancer cases and 327 controls from Algeria and India. Antibody response was evaluated using a glutathione S-transferase-based multiplex serology assay and HPV DNA detected from exfoliated cervical cells using a GP5+/6+-mediated PCR assay. Among HPV16 DNA-positive cases, seroprevalence of HPV16 antibodies ranged from 16% for HPV16 E1 to 50% for HPV16 E6 and all were significantly higher than controls. Seroprevalence of E6, E7 and L1 antibodies for HPV18 and for at least one of HPV31/33/35/45/52/58 were also higher in cases positive for DNA of the corresponding type (50% and 30% for E6 of HPV18 and HPV31/33/35/45/52/58 combined, respectively). E6 and E7 antibodies were rarely found in controls, but cross-reactivity was evident among cancer cases positive for DNA of closely phylogenetically-related HPV types. E6 or E7 antibodies against any of the eight HPV types were detected in 66.1% of all cervical cancer cases, as compared to 10.1% of controls. E6, and to a lesser extent E7, antibodies appear to be specific markers of HPV-related malignancy. However, even among cases positive for the same type of HPV DNA, approximately one-third of cervical cancer cases show no detectable immune response to either E6 or E7.

Therapeutic Vaccine Strategies against Human Papillomavirus

High-risk types of human papillomavirus (HPV) cause over 500,000 cervical, anogenital and oropharyngeal cancer cases per year. The transforming potential of HPVs is mediated by viral oncoproteins. These are essential for the induction and maintenance of the malignant phenotype. Thus, HPV-mediated malignancies pose the unique opportunity in cancer vaccination to target immunologically foreign epitopes. Therapeutic HPV vaccination is therefore an ideal scenario for proof-of-concept studies of cancer immunotherapy. This is reflected by the fact that a multitude of approaches has been utilized in therapeutic HPV vaccination design: protein and peptide vaccination, DNA vaccination, nanoparticle- and cell-based vaccines, and live viral and bacterial vectors. This review provides a comprehensive overview of completed and ongoing clinical trials in therapeutic HPV vaccination (summarized in tables), and also highlights selected promising preclinical studies. Special emphasis is given to adjuvant science and the potential impact of novel developments in vaccinology research, such as combination therapies to overcome tumor immune suppression, the use of novel materials and mouse models, as well as systems vaccinology and immunogenetics approaches.

Recombinant Leishmania tarentolae encoding the HPV type 16 E7 gene in tumor mice model

Background: Cervical cancer, the third most prevalent cause of cancer in women worldwide, is associated with HPVs. The critical role of E7 protein in HPV-related malignancies has designated it as a strong contender for generating vaccines against HPV. Materials & methods: In this study, we developed a novel live vaccine using recombinant Leishmania tarentolae expressing E7-green fluorescent protein (GFP) fusion protein for the protection of mice against HPV-associated tumors. In order to transfect L. tarentolae with E7-GFP fusion construct, pLEXSY-neo2 system was applied. Followed by PCR, fluorescence imaging and fluorescence-activated cell sorting analysis, integration of E7-GFP gene into parasites genome was confirmed. A comparative study of six groups of C57BL/6 mice was performed to analyze antigen-specific humoral and cellular immune responses against E7 encoding live and DNA vaccines. Furthermore, the anti-tumor protective effect of L. tarentolae-E7-GFP was compared to other vaccination strategies, namely pcDNA-E7 as the DNA vaccine and pcDNA-E7/L. tarentolae-E7-GFP as the prime-boost regimen. Results: We found that E7-GFP expressing recombinant L. tarentolae induces significant levels of IgG2a and IFN-γ, while there is no significant IL-5 production compared with that of other strategies and control groups before and after challenge with TC-1 tumor cells. It is noteworthy that the designed live vaccine showed the best protection and minimum tumor size among all groups against TC-1-induced tumors. Conclusion: Overall, the results obtained revealed that the E7-GFP recombinant L. tarentolae could be a potential live vaccine for induction of immune responses in vivo.

Biology of human papillomavirus infection and immune therapy for HPV-related head and neck cancers

This article outlines the biology of human papillomavirus (HPV) infection of human mucosa and the cellular pathways that are altered through viral infection. The article provides a conceptual framework with which to understand the 2 major immunologic strategies to address HPV-related diseases: (1) prevention of primary HPV infection through the use of prophylactic vaccines and (2) treatment of established infection and diseases through therapeutic vaccines. Nonimmunologic therapy that targets cellular dysregulation induced by HPV infection is also discussed. The challenges in actualizing these conceptually attractive therapies on both a societal and biological level are examined.

Age-specific human papillomavirus antibody and deoxyribonucleic acid prevalence: a global review

PURPOSE

Global data on human papillomavirus (HPV) serological and deoxyribonucleic acid (DNA) prevalence are essential to optimize HPV prophylactic vaccination strategies.

METHODS

We conducted a global review of age-specific HPV antibody and studies with both antibody and DNA prevalence for HPV-16, -18, -6, and -11.

RESULTS

One hundred seventeen studies were included; participants' ages ranged from several hours to >90 years. HPV-16 seroprevalence was generally higher in Africa, Central and South America, and North America, more prevalent among women than among men, and peaked around ages 25-40 years. HPV-18 seroprevalence was generally lower than HPV-16 with a later age peak. Data were limited for HPV-6 and -11, both of which peaked at ages similar to HPV-18. Among 9-26-year-old females, HPV-16 seroprevalence ranged from 0%-31% in North America, 21%-30% in Africa, 0%-23% in Asia/Australia, 0%-33% in Europe, and 13%-43% in Central and South America. HPV-16/-18 DNA prevalence peaked 10-15 years before corresponding HPV-16/-18 antibody prevalence.

CONCLUSIONS

Females within the HPV vaccine-eligible age-group (9-26 years) had a range of dual HPV-16 DNA and serology negativity from 81%-87%, whereas 90%-98% were HPV-16 DNA negative. Serology and DNA data are lacking worldwide for females younger than age 15 years, the prime target group for vaccination.

Paradigm shifting vaccines: prophylactic vaccines against latent varicella-zoster virus infection and against HPV-associated cancer

We compare the design, mechanism of action, and clinical efficacy of two recently licensed paradigm shifting vaccines. Zostavax is the first vaccine licensed to prevent disease in patients already infected with a pathogen, and is contrasted with Gardasil and Cervarix, the first vaccines designed and licensed specifically to prevent cancers.

New Approaches to Immunotherapy for HPV Associated Cancers

Cervical cancer is the second most common cancer of women worldwide and is the first cancer shown to be entirely induced by a virus, the human papillomavirus (HPV, major oncogenic genotypes HPV-16 and -18). Two recently developed prophylactic cervical cancer vaccines, using virus-like particles (VLP) technology, have the potential to prevent a large proportion of cervical cancer associated with HPV infection and to ensure long-term protection. However, prophylactic HPV vaccines do not have therapeutic effects against pre-existing HPV infections and do not prevent their progression to HPV-associated malignancy. In animal models, therapeutic vaccines for persisting HPV infection can eliminate transplantable tumors expressing HPV antigens, but are of limited efficacy in inducing rejection of skin grafts expressing the same antigens. In humans, clinical trials have reported successful immunotherapy of HPV lesions, providing hope and further interest. This review discusses possible new approaches to immunotherapy for HPV associated cancer, based on recent advances in our knowledge of the immunobiology of HPV infection, of epithelial immunology and of immunoregulation, with a brief overview on previous and current HPV vaccine clinical trials.

Human papillomavirus 16 E5 modulates the expression of host microRNAs

Human papillomavirus (HPV) infection is a prerequisite of developing cervical cancer, approximately half of which are associated with HPV type 16. HPV 16 encodes three oncogenes, E5, E6, and E7, of which E5 is the least studied so far. Its roles in regulating replication and pathogenesis of HPV are not fully understood. Here we utilize high-throughput screening to coordinately investigate the effect of E5 on the expression of host protein-coding and microRNA genes. MicroRNAs form a class of 22nt long noncoding RNAs with regulatory activity. Among the altered cellular microRNAs we focus on the alteration in the expression of miR-146a, miR-203 and miR-324-5p and their target genes in a time interval of 96 hours of E5 induction. Our results indicate that HPV infection and subsequent transformation take place through complex regulatory patterns of gene expression in the host cells, part of which are regulated by the E5 protein.

Prevention and treatment of papillomavirus-related cancers through immunization

Cervical and other anogenital cancers are initiated by infection with one of a small group of human papillomaviruses (HPV). Virus-like particle-based vaccines have recently been developed to prevent infection with two cancer-associated HPV genotypes (HPV16, HPV18) and have been ∼95% effective at preventing HPV-associated disease caused by these genotypes in virus-naive subjects. Although immunization induces virus-neutralizing antibody sufficient to prevent infection, persistence of antibody as measured by current assays does not appear necessary to maintain protection over time. Investigators have not identified a reliable surrogate immunological marker of protection against disease following immunization. The prophylactic vaccines are not therapeutic for existing infection. Trials of HPV-specific immunotherapy have shown some efficacy for existing disease, although animal modeling suggests that a combination of immunization and local enhancement of innate immunity may be necessary for optimal therapeutic outcome. HPV prophylactic vaccines are the first vaccines designed to prevent a human cancer and are the practical outcome of a global collaborative effort between basic and applied scientists, clinicians, and industry.

A novel HPV 16 L1-based chimeric virus-like particle containing E6 and E7 seroreactive epitopes permits highly specific detection of antibodies in patients with CIN 1 and HPV-16 infection

Background

The presence of IgG antibodies to HPV-16 L1-virus like particles (VLPs) in serum has been reported as a result of persistent exposure to the virus and as a marker of disease progression. However, detection of VLP-specific antibodies in sera does not always indicate a malignant lesion as positive results may also be due to a nonmalignant viral infection. Furthermore, malignant lesions are associated with an increased antibody titer for E6 and E7 proteins. The aim of this study was to develop an ELISA using a novel chimeric virus-like particle (cVLP) encoding an L1 protein fused with a string of HPV-16 E6 and E7 seroreactive epitopes to its C-terminus to be used for detection of HPV-16 specific antibodies in patients with cervical intraepithelial lesion grade 1 (CIN 1).

Results

The sera of 30 patients with CIN 1 who also tested positive for HPV-16 DNA and of 30 age-matched normal donors negative for HPV infection were tested for the presence of IgG antibodies specific for either VLP-L1 (HPV-16 L1), gVLP (derived from Gardasil), or cVLP by ELISA. The cVLP-reactive sera yielded two distinct groups of results: (H) reactivity levels that presented very strong cVLP-specific titers, and (L) reactivity levels with significantly lower titers similar to those obtained with VLP-L1 and gVLP antigens. Additionally, the sera that presented the higher cVLP titers closely matched those that had significantly stronger reactivity to E6 and E7 epitopes. Interestingly, the samples with the highest titers corresponded to patients with the higher numbers of sexual partners and pregnancies. On the other hand only 4 out of the 12 sera that harbored antibodies with VLP neutralizing ability corresponded to the group with high cVLP antibody titers.

Conclusion

We report for the first time that chimeric particles containing HPV-16 L1 protein fused with E6 and E7 seroreactive epitopes enable much better detection of IgG antibodies in the sera of CIN 1 patients positive for HPV-16 infection than those obtained with VLPs containing only the HPV-16 L1 protein. We also found that the sera with higher cVLP antibody titers corresponded to patients with more sexual partners and pregnancies, and not always with to those with a high neutralizing activity. This novel assay could help in the development of a tool to evaluate cervical cancer risk.

Computer-aided analysis of structural properties and epitopes of Iranian HPV-16 E7 oncoprotein

Infection by human papillomavirus type 16 (HPV-16) is the cause of 50% or more of cervical cancers in women. The E7 oncoprotein of HPV-16 has long been known as a potent immortalizing and transforming agent. We used different servers like PseAAC, MHC_binding, MHC_II_binding and Expasy for the present computational prediction. The results for T cell epitopes showed that B1501, A0203, A0201, A0202, A6801 and DRB0405 alleles had lower IC50 than other alleles. We also predicted several peptides with the best binding affinities for alleles of the most frequent MHC class I and II alleles of the various ethnic groups living in the different region of Iran. Two peptides (26-35) and (44-52) were predicted as B-cell epitopes. According to this analysis 1 N-glycosylation site, 2 PKC sites, 4 CK2 sites and 3 disulfide sites were predicted. Our computational study predicted that B cell epitope 1 was Casein kinase II phosphorylated (site No. 31) and glycosylated (site No. 29). Putative MHC-I epitopes 3 and 5 and MHC-II epitopes 19, 21 and 26 were predicted to be casein kinase II phosphorylated. MHC-II epitopes 19 and 21 was predicted to be glycosylated. T cell epitopes 1, 13, 16 and 24 were demonstrated to be kinase C phosphorylated. The result of this analysis for Iranian HPV-16 E7 also indicated that 21.43%, 18.37% and 60.20% of the protein were in the α-helix, extended strand and random coil respectively.

SA-4-1BBL as the immunomodulatory component of a HPV-16 E7 protein based vaccine shows robust therapeutic efficacy in a mouse cervical cancer model

Cervical cancer is the leading cause of cancer-related deaths among women worldwide. Current prophylactic vaccines based on HPV (Human papillomavirus) late gene protein L1 are ineffective in therapeutic settings. Therefore, there is an acute need for the development of therapeutic vaccines for HPV associated cancers. The HPV E7 oncoprotein is expressed in cervical cancer and has been associated with the cellular transformation and maintenance of the transformed phenotype. As such, E7 protein represents an ideal target for the development of therapeutic subunit vaccines against cervical cancer. However, the low antigenicity of this protein may require potent adjuvants for therapeutic efficacy. We recently generated a novel chimeric form of the 4-1BBL costimulatory molecule engineered with core streptavidin (SA-4-1BBL) and demonstrated its safe and pleiotropic effects on various cells of the immune system. We herein tested the utility of SA-4-1BBL as the immunomodulatory component of HPV-16 E7 recombinant protein based therapeutic vaccine in the E7 expressing TC-1 tumor as a model of cervical cancer in mice. A single subcutaneous vaccination was effective in eradicating established tumors in approximately 70% of mice. The therapeutic efficacy of the vaccine was associated with robust primary and memory CD4(+) and CD8(+) T cell responses, Th1 cytokine response, infiltration of CD4(+) and CD8(+) T cells into the tumor, and enhanced NK cell killing. Importantly, NK cells played an important role in vaccine mediated therapy since their physical depletion compromised vaccine efficacy. Collectively, these data demonstrate the utility of SA-4-1BBL as a new class of multifunctional immunomodulator for the development of therapeutic vaccines against cancer and chronic infections.

Development of therapeutic HPV vaccines

At least 15% of human malignant diseases are attributable to the consequences of persistent viral or bacterial infection. Chronic infection with oncogenic human papillomavirus (HPV) types is a necessary, but insufficient, cause in the development of more cancers than any other virus. Currently available prophylactic vaccines have no therapeutic effect for established infection or for disease. Early disease is characterised by tissue sequestration. However, because a proportion of intraepithelial HPV-associated disease undergoes immune-mediated regression, the development of immunotherapeutic strategies is an opportunity to determine proof-of-principle for therapeutic vaccines. In this Review, we discuss recent progress in this field and priorities for future clinical investigations.

Interaction of human papillomaviruses with the host immune system: a well evolved relationship

Human papillomavirus (HPV) infections are generally long lasting, and a host immune response to infection is hard to detect. Nevertheless immunocompromised subjects control HPV infection less well than those with intact immunity. Immune responses are best documented for the papillomavirus groups that cause evident human disease, particularly those responsible for anogenital cancers and genital warts. Humoral immunity to the viral capsid has been shown sufficient for protection against infection, while innate and adaptive cell mediated immunity appears important for eventual elimination of HPV infection. However, molecular and cellular mechanisms responsible for protection from and clearance of HPV infection are not completely established.

Clinical and epidemiological correlates of antibody response to human papillomaviruses (HPVs) as measured by a novel ELISA based on denatured recombinant HPV16 late (L) and early (E) antigens

BACKGROUND

At present, seroreactivity is not a valuable parameter for diagnosis of Human Papillomavirus (HPV) infection but, it is potentially valuable as marker of viral exposure in elucidating the natural history of this infection. More data are needed to asses the clinical relevance of serological response to HPV.

OBJECTIVES

The objective was to assess the clinical and epidemiological correlates of HPV-seroreactivity in a cohort of HIV-negative and HIV-positive women.

METHODS

Seroreactivity of 96 women, evaluated in an ELISA test based on denatured HPV16 late (L) and early (E) antigens, was correlated with their clinical and epidemiological data previously collected for a multi-centre Italian study, HPV-PathogenISS study.

RESULTS

No significant correlation was found between HPV DNA detection and seroreactivity. Women, current smokers showed significantly less seroreactivity to L antigens as compared with the non-smokers. HIV-positive women showed significantly less (66.7%) antibody response as compared with HIV-negative women (89.3%), with particularly impaired response to L antigens. Women, HIV-positive and current smokers, showed by far the lowest seroprevalence (33.3%) as compared to 75.9% among all other women (OR = 0.158; 95%CI 0.036-0.695, p = 0.014; Fisher's exact test). Importantly, this association did not loose its significance when controlled for confounding from age (continuous variable) in multivariate analysis or using Mantel-Haenszel test for age-groups.

CONCLUSION

It is tempting to speculate that HIV-positive current smokers comprise a special high-risk group, with highly impaired immunological response that could prevent eradication of persistent HPV infections and thus contribute to development of CIN3/CC.

A novel algorithm for reliable detection of human papillomavirus in paraffin embedded head and neck cancer specimen

Human papillomavirus type 16 (HPV16) plays a role in the development of a subgroup of head and neck squamous cell carcinomas (HNSCC). However, uncertainty exists about the true impact of HPV in this tumor type as conflicting reports have been published with prevalence rates from 0 to 100%. We aimed to find a detection algorithm of a biologically and thus clinically meaningful infection, applicable for high-throughput screening of frozen and formalin-fixed paraffin embedded (FFPE) specimens. By considering detection of HPV E6 oncogene expression in frozen biopsies as gold standard for a meaningful HPV infection, the value of several assays was evaluated on FFPE tumor specimens and sera of 48 HNSCC patients. The following assays were evaluated on FFPE tissue samples: HPV DNA general primer (GP)5+/6+ PCR, viral load analysis, HPV16 DNA FISH detection, HPV16 E6 mRNA RT-PCR, p16 immunostaining, and on corresponding serum samples detection of antibodies against the HPV16 proteins L1, E6 and E7. Comparing single assays on FFPE tissue samples detection of E6 expression by RT-PCR was superior, but application remains at present limited to HPV16 detection. Most suitable algorithm with 100% sensitivity and specificity appeared p16 immunostaining followed by GP5+/6+ PCR on the p16-positive cases. We show that clinically meaningful viral HPV infections can be more reliably measured in FFPE HNSCC samples in a standard and high throughput manner, paving the way for prognostic and experimental vaccination studies, regarding not only HNSCC, but possibly also cancer types with HPV involvement in subgroups such as penile and anal cancer.

Human papillomavirus therapeutic vaccines in head and neck tumors

Head and neck cancer represents one of the most challenging diseases as the mortality remains high despite advances in early diagnosis and treatment. Human papillomavirus has been implicated in a third of head and neck squamous cell carcinomas and human papillomavirus type 16 is strongly associated with carcinomas arising from the oropharynx, the tonsil being the preferred infected site. Novel therapeutic approaches including immunotherapy are currently under investigation. Immune vaccines developed against human papillomavirus in the genital area are already available and could simultaneously protect other anatomical localizations; however, prophylactic vaccines are expected to be effective in reducing the incidence of tumors after many years and, therefore, there is an urgent need to improve therapeutic interventions, such as immunotherapy. To date, human papillomavirus therapeutic vaccines are either at the preclinical level or at early phase human trials for genital pathologies. Nevertheless, accumulating evidence from animal and clinical studies suggests that the enhancement of specific and innate immune responses is effective in clearance of the human papillomavirus infection, promoting a cautious optimism regarding the achievement of an efficacious immunotherapy. This article reviews what has been achieved and what remains to be done in the field for the development of future viral vaccines in head and neck tumors.

Human papillomavirus seropositivity and risks of head and neck cancer

We examined antibody response to VLP HPV-16, HPV-16 E6 and E7 antibodies as potential seromarkers of HPV-related head and neck cancer (HNC). The study included 204 HNC cases and 326 controls evaluated for HPV presence in sera using ELISAs for anti-HPV VLP antibodies and HPV-16 E6 and/or E7 antibodies, and in tumor tissue using PCR and DNA sequencing. Anti-HPV-16 VLP was detected in 33.8% of cases and 22.4% of controls, anti-E6 in 20.6% of cases and 0.9% of controls and anti-E7 in 18.6% of cases and 0.6% of controls. HPV-16 DNA was detected in 26.1% of tumors. The adjusted risk of HNC was elevated among those seropositive for HPV-16 VLP (odds ratio (OR) = 1.7, 1.1-2.5), E6 (OR = 32.8, 9.7-110.8) or E7 (OR = 37.5, 8.7-161.2). Compared to HPV DNA-negative/seronegative cases, tumor HPV-16 cases had increased risk of detection with anti-VLP antibodies (OR = 6.8, 3.1-14.9). The odds were more pronounced among cases seropositive for E6 (OR = 69.0, 19.3-247) or E7 (OR = 50.1, 14.7-171). Antibodies against E6 or E7 were associated with risk of cancer in the oral cavity (OR = 5.1, 1.2-22.4) and oropharynx (OR = 72.8, 16.0-330), and with disease characteristics: stage, grade and nodal status. Anti-E6 and/or E7 antibodies were found in 74% of tumor HPV-16 positive cases but in only 5% of tumor HPV-negative cases (K =0.7, 0.6-0.8) suggesting good correlation between the serologic marker and HPV tumor status. Antibodies to HPV-16 E6 and/or E7 represent a more specific biomarker than anti-HPV-16 VLP of an HPV-related HNC. Because of the survival advantage of HPV-related HNC, HPV-16 E6/E7 detection may be useful in therapy targeted for HPV-related tumors.

Frequency of antibodies against E4 and E7 from human papillomavirus type 16 in Mexican soldiers

The high prevalence of HPV in men's genitalia and the low frequency of virus-associated lesions gave rise to questions on the influence of infection-site on the HPV antibody profile. In a cross-sectional study, HPV infection in penis and urethra, and serum antibodies against HPV-16 E4 and E7 proteins were evaluated in 288 Mexican soldiers. The results showed that HPV prevalence was 31% (51% in penis, 11% in urethra and 38% in both sites), while 47% were multiple infections. Overall, seroprevalence was 13% for anti-E4 antibodies and 6% for anti-E7. However, the highest prevalence of anti-E4 antibodies was observed in men with HPV infection in urethra (30%), while for E7 antibodies, the highest prevalence (10%) was found in men who tested positive for HPV in penis. The prevalence of IgG and IgA anti-E4 was related to HPV-16 urethral infection, while detection of HPV-16 in penis was related to IgG anti-E7 prevalence. In conclusion, the high-risk sexual behavior observed in this population might be responsible for high HPV prevalence and multiple infections. However, the seroprevalence of E4 and E7 was similar to that observed in healthy Mexican women. These results suggest that the humoral immune response against HPV infection in men differs, depending on the site of infection.

Vaccines against human papillomavirus and cervical cancer: promises and challenges

Cervical cancer and precancerous lesions of the genital tract are major threats to the health of women worldwide. The introduction of screening tests to detect cervical cancer precursor lesions has reduced cervical cancer rates in the developed world, but not in developing countries. Human papillomavirus (HPV) is the primary etiologic agent of cervical cancer and dysplasia. Thus, cervical cancer and other HPV-associated malignancies might be prevented or treated by HPV vaccines. Two vaccine strategies have been developed. First, prevention of HPV infection through induction of capsid-specific neutralizing antibodies has been studied in clinical trials. However, because the capsid proteins are not expressed at detectable levels by infected basal keratinocytes or in HPV-transformed cells, a second approach of developing therapeutic vaccines by targeting nonstructural early viral antigens has also been developed. Because two HPV oncogenic proteins, E6 and E7, are critical to the induction and maintenance of cellular transformation and are coexpressed in the majority of HPV-containing carcinomas, most therapeutic vaccines target one or both of these gene products. A variety of approaches is being tested in therapeutic vaccine clinical trials, whereby E6 and/or E7 are administered in live vectors, as peptides or protein, in nucleic acid form, or in cell-based vaccines. The paradigm of preventing HPV infection through vaccination has been tested, and two vaccines are currently in phase III clinical trials. However, current therapeutic vaccine trials are less mature with respect to disease clearance. A number of approaches have shown significant therapeutic benefit in preclinical papillomavirus models and await testing in patient populations to determine the most effective curative strategy.

Inverse correlation of cellular immune responses specific to synthetic peptides from the E6 and E7 oncoproteins of HPV-16 with recurrence of cervical intraepithelial neoplasia in a cross-sectional study

BACKGROUND

Epidemiological studies have clearly established that human papillomavirus (HPV) infection is the major risk factor for cervical cancer. Most cervical cancers and pre-cancers are HPV-positive. Not all pre-cancers progress to cancer; a significant number regress. The immunological basis for either spontaneous or treatment-mediated recovery from HPV-associated CIN is not clear. Currently, prophylactic vaccines are successfully inducing antibody responses in HPV negative patients. Therapeutic vaccines for HPV-positive patients with disease are needed. There is a need to understand the immunologic basis for the Cell-Mediated Immune (CMI) response and for histological regression to help the formulation of therapeutic vaccines.

MATERIAL AND METHODS

Four groups of women were identified for this cross-sectional study of CMI. Group 1 consisted of six women without cytological or histological diagnosis of CIN and with an HPV negative test (CIN((-))/HPV((-))). Group 2 included 31 women with a new histological diagnosis of CIN and HPV positive test (CIN((+))/HPV((+))). Groups 3 and 4 were selected from women who had undergone ablative or excisional treatment for CIN at the colposcopy clinic at least 6 months before the study. The women in groups 3 and 4 were (CIN((+))/HPV((+))) before CIN treatment. Group 3 consisted of 22 women without evidence of recurrence of CIN (Recur((-))), and group 4 included 10 with histological diagnosis of recurrent CIN (Recur((+))). In particular, we investigated CMI responses to synthetic peptides from the E6 and E7 oncoproteins of HPV-16.

RESULTS

Compared to patients with disease recurrence (Recur((+)), n = 10), the majority of individuals who remained recurrence-free post-treatment (Recur((-)), n = 22) exhibited significant proliferative responses to synthetic peptides from the E6 (P = 0.001) and the E7 (P = <0.001). In particular, significant responses were observed with the E6 peptide Q15L (aa 43-57, P = 0.006) and the E7 peptide Q19D (aa 44-62, P = 0.002) in Recur((-)) patients but not Recur((+)) individuals. Additionally, PBMC from women in the Recur((-)) group, but not the Recur((+)) group, produced predominantly TH1 cytokines upon stimulation with the peptides Q15L or Q19D.

CONCLUSIONS

These results indicate an association between significant cellular immune responses specific to synthetic peptides from the E6 and E7 oncoproteins of HPV-16 and recurrence-free survival in HPV patients treated for CIN. We predict that these peptides may be useful as indicators of protective immunity for recovery from CIN and also for potential inclusion in designing immunotherapeutic and immunoprophylactic reagents for HPV-associated CIN.

High-risk mucosal human papillomavirus infections during infancy & childhood

Human papillomaviruses (HPVs) are small DNA tumour viruses associated with a variety of proliferative diseases. More than 100 types have been identified and can broadly be grouped into cutaneous and mucosal types according to their site of infection, and can be further subdivided into low-risk (LR) and high-risk (HR) types depending upon their association with malignancy. The main route of transmission of HR mucosal HPVs is through sexual contact, although the acquisition of virus cannot be entirely explained by this mode alone. Evidence also exists for horizontal transmission by other routes and vertical transmission. HR HPVs, particularly HPV-16, have been detected in oral swabs from newborns, infants and children. Such alternative modes of transmission and acquisition may have an important impact in several areas, including vaccination strategies, epidemiological studies, and the clinical management of children with HPV-associated diseases. This article reviews the literature describing the detection of HPV infections during infancy and childhood and provides evidence for a role of vertical transmission in the spread of HPV infection.

Strategies for the prevention of cervical cancer by human papillomavirus vaccination

As cervical cancer is causally associated with 14 high-risk types of human papillomavirus (HPV), a successful HPV vaccine will have a major impact on this disease. Although some persistent HPV infections progress to cervical cancer, host immunity is generally able to clear most HPV infections. Both cell-mediated and antibody responses have been implicated in influencing the susceptibility, persistence or clearance of genital HPV infection. There have been two clinical trials that show that vaccines based on virus-like particles (VLPs) made from the major capsid protein, L1, are able to type specifically protect against cervical intra-epithelial neoplasia and infection. However, there is no evidence that even a mixed VLP vaccine will protect against types not included in the vaccine, and a major challenge that remains is how to engineer protection across a broader spectrum of viruses. Strategies for production of HPV vaccines using different vaccine vectors and different production systems are also reviewed.

Immune control of human papillomavirus (HPV) associated anogenital disease and potential for vaccination

This review discusses: (1) immune mechanisms relevant to the natural control of a human papillomavirus (HPV) infection; (2) viral strategies to evade or subvert immune attack; (3) the significance of immune escape as a feature of the evolution of invasive cancer; (4) vaccine strategies for prevention and/or therapy. HPV infection and associated malignancy can induce humoral and cellular immunity to capsid and oncogene viral proteins, but it is not always clear whether such responses are a consequence of the disease rather than the resolving factor(s). Prophylactic strategies are utilising virus-like particles (VLP) composed of the L1 viral capsid protein to induce neutralising antibodies, while therapeutic approaches are aimed at generating specific T cells targeted at the viral E6 and/or E7 oncogenes. Thus far, HPV VLP vaccines have proved clinically efficacious in the early clinical trials to prevent infection. Different types of therapeutic vaccines including peptide, protein, DNA or viral vector encoded have proved safe and immunogenic in patients, although there is often no correlation with clinical outcome. Understanding the equilibrium between viral and immunological factors will be important in providing the appropriate tools to evoke effective prophylactic and therapeutic immunity. It seems likely that combined prophylactic and therapeutic vaccine approaches could offer the best prospect for any significant reduction in death from cervical cancer worldwide.

Impaired antigen presentation and effectiveness of combined active/passive immunotherapy for epithelial tumors

BACKGROUND

Although immunization with tumor antigens can eliminate many transplantable tumors in animal models, immune effector mechanisms associated with successful immunotherapy of epithelial cancers remain undefined.

METHODS

Skin from transgenic mice expressing the cervical cancer-associated tumor antigen human papillomavirus type 16 (HPV16) E6 or E7 proteins from a keratin 14 promoter was grafted onto syngeneic, non-transgenic mice. Skin graft rejection was measured after active immunization with HPV16 E7 and adoptive transfer of antigen-specific T cells. Cytokine secretion of lymphocytes from mice receiving skin grafts and immunotherapy was detected by enzyme-linked immunosorbent assay, and HPV16 E7-specific memory CD8+ T cells were detected by flow cytometry and ELISPOT.

RESULTS

Skin grafts containing HPV16 E6-or E7-expressing keratinocytes were not rejected spontaneously or following immunization with E7 protein and adjuvant. Adoptive transfer of E7-specific T-cell receptor transgenic CD8+ T cells combined with immunization resulted in induction of antigen-specific interferon gamma-secreting CD8+ T cells and rejection of HPV16 E7-expressing grafts. Specific memory CD8+ T cells were generated by immunotherapy. However, a further HPV16 E7 graft was rejected from animals with memory T cells only after a second E7 immunization.

CONCLUSIONS

Antigen-specific CD8+ T cells can destroy epithelium expressing HPV16 E7 tumor antigen, but presentation of E7 antigen from skin is insufficient to reactivate memory CD8+ T cells induced by immunotherapy. Thus, effective cancer immunotherapy in humans may need to invoke sufficient effector as well as memory T cells.

The role of human papillomavirus in oral carcinogenesis

Human papillomavirus (HPV) infection with high-risk types 16 and 18 has widely been reported as one of the prominent mechanisms behind the development of cervical squamous cell carcinoma. Links between HPV and oral cavity cancer have been suggested as well, based on epidemiologic and molecular means, though the association is less well-established. It is likely that HPV plays a role in oral cavity carcinogenesis, though only in a small subset of cases. The difficulty in providing true causal evidence of HPV's role in oral cancer lies in our lack of understanding of the significance of mechanisms by which HPV leads to oral carcinogenesis, as well as limitations in the molecular analysis of HPV. Further studies are necessary for the contribution of HPV in oral cavity malignancy to be better demonstrated.

Prevention of cervical cancer through papillomavirus vaccination

A subset of human papillomaviruses (HPVs) promote anogenital malignancy, including cervical cancer, and prevention and treatment strategies that reflect the causal role of HPV are being developed. Vaccines based on HPV virus-like particles induce genotype-specific virus-neutralizing antibody and prevent infection with HPV. Persistent papillomavirus infection is required for the development of papillomavirus-associated cancer and, therefore, therapeutic vaccines are being developed to eliminate established papillomavirus infection. Such vaccines test principles for the growing field of tumour-antigen-specific immunotherapy. This article reviews progress in the field and draws conclusions for the development of future prophylactic and therapeutic viral vaccines.

Mutations in TAP genes are common in cervical carcinomas

OBJECTIVE

To determine whether squamous cervical cancers exhibit mutations or deletions in MHC class I genes or transport-associated protein (TAP) genes.

METHODS

Polymerase chain reaction based protocols were used to examine HLA class I and TAP genes in a panel of cervical tumours, using DNA from corresponding blood samples as controls. SSP-PCR protocols were similarly used for examination of all TAP alleles in tumour and blood samples.

RESULTS

In a series of cervical carcinomas, 7 of 27 (26%) exhibited mutations in HLA-A genes, while 12 of 23 (52%) exhibited mutations in TAP genes. HLA gene mutations were detected in 2 of 14 CIN2-3 lesions, and TAP gene mutations in none of 14, a frequency significantly less than observed in the cervical carcinoma samples (P<0.01). The TAP 2A/2B heterozygous genotype was observed with increased frequency in patients with cervical cancer compared to population controls (P<0.02).

CONCLUSION

These data suggest that TAP genes may be relevant to evolution of cervical cancer from precursor lesions.

Evaluation of antibody response to human papillomavirus early proteins in women in whom cervical cancer developed 1 to 20 years later

OBJECTIVE

Infection with oncogenic human papillomaviruses (HPVs) is the most important cause of cervical cancer worldwide. After infection there is a long latency period of at least 10 to 15 years during which cervical cancer develops in a small proportion of originally infected women. Up to 50% of these women have at diagnosis antibodies to the HPV oncoproteins E6 and E7, which are rarely found among healthy women. Our purpose was to evaluate whether antibodies to HPV16 and HPV18 E6 and E7 proteins are useful for early diagnosis of cervical cancer by measuring the antibody response in women in whom cervical cancer later developed.

STUDY DESIGN

A joint serum bank of 550,000 Swedish, Norwegian, and Finnish women was followed up for 0.5 to 20 years, after which 178 invasive cervical carcinoma (ICC) cases, 150 of whom had squamous cell carcinoma (SCC), and 527 controls were identified. Antibodies to HPV16 and HPV18 E6 and E7 proteins were determined by tag enzyme-linked immunoassays.

RESULTS

HPV16/18 E6 and E7 antibodies were detected infrequently (7.0%) in women in whom SCC later developed and yielded a moderately increased estimate of associated relative risk (odds ratio 2.7, 95% CI 1.1-6.4). Sensitivity of the combined antibody tests for the detection of occult SCC varied between 6% and 14% but was not related to time lag between serum sampling and cancer diagnosis.

CONCLUSION

HPV16/18 E6 and E7 antibody responses are not sensitive markers of occult cervical cancer.

Sexual and non-sexual transmission of human papillomavirus

Benign tumors and lesions of the anogenital tract are caused by human papillomaviruses (HPVs). They are also major risk factors for cervical cancer. Introduction of the polymerase chain reaction (PCR) revealed that HPV infections are much more common among young asymptomatic women than it had been previously suspected. The side-specificity of genital HPVs led to the assumption that HPVs were primarily transmitted by sexual contact. However, since HPVs have been detected in virgins, infants/children and juvenile laryngeal papillomatosis was shown to be caused by these viruses, it became acknowledged that HPVs may be transmitted by other--non-sexual--routes as well. The evidence for sexual and different non-sexual routes of transmission of HPVs will be reviewed here.

Human papillomavirus infections in children: the potential role of maternal transmission

To date, more than 100 types of human papillomavirus (HPV) have been identified. In the past 20 years, there has been an increasing interest in HPVs because of their potential role in the pathogenesis of malignant tumors. HPV infections are known to affect predominantly adult, sexually active age groups, whereas skin warts, at various anatomic sites, are usually associated with younger individuals. The modes of viral transmission in children remain controversial, including perinatal transmission, auto- and hetero-inoculation, sexual abuse, and, possibly, indirect transmission via fomites. Recent studies on perinatal infection with HPV have been inconclusive. It is still unclear how frequently perinatal infection progresses to clinical lesions, whether genital, laryngeal, or oral. Conflicting reports have been published on the prevalence of HPV infections in children. The current consensus is, however, that newborn babies can be exposed to cervical HPV infection of the mother. The detection rate of HPV DNA in oral swabs of newborn babies varies from 4% to 87%. The concordance of HPV types detected in newborn babies and their mothers is in the range of 57% to 69%, indicating that the infants might acquire the HPV infection post-natally from a variety of sources. HPV antibodies have been detected in 10% to 57% of the children, and there is usually no correlation between seropositivity and the detection of HPV DNA in either the oral or the genital mucosa. There is also evidence that transmission in utero or post-natal acquisition is possible. The mode of in utero transmission remains unknown, but theoretically the virus could be acquired hematogenously, by semen at fertilization, or as an ascending infection in the mother. The understanding of viral transmission routes is important, particularly because several vaccination programs are being planned worldwide. The serologic response to HPV detected in different populations of young women or women at risk of cervical cancer might be due to genital infections, but the possibility that HPV infection has been acquired earlier in life through the oral mucosa or respiratory tract cannot be ruled out.

Identification of peptide sequences specific for serum antibodies from human papillomavirus-infected patients using phage display libraries

Three random phage display peptide libraries were screened with sera from human papillomavirus (HPV)-infected patients to characterize the specificities of antibodies present in patients' sera and to identify molecules that correspond to or mimic natural epitopes; 141 phage clones were randomly selected in three rounds of bioselection and their binding properties were analyzed in ELISA using sera from 36 patients with confirmed HPV 16 infection and 24 healthy control female blood donors. Sixteen of 36 (44%) patients' sera reacted with at least 1 phage clone, and only 2 of 24 female donors' sera showed positive reaction with 1 of the selected clones. We conclude that the combination of various disease-specific epitopes generated by screening of phage display peptide libraries may potentially lead to a multicomponent diagnostic assay for the early detection of HPV infection and precancerous cervical lesions, making possible the prevention of one of the most common cancers in women.

Tolerance or immunity to a tumor antigen expressed in somatic cells can be determined by systemic proinflammatory signals at the time of first antigen exposure

Mice transgenic for the E7 tumor Ag of human papillomavirus type 16, driven from a keratin 14 promoter, express E7 in keratinocytes but not dendritic cells. Grafted E7-transgenic skin is not rejected by E7-immunized mice that reject E7-transduced transplantable tumors. Rejection of recently transplanted E7-transgenic skin grafts, but not of control nontransgenic grafts or of established E7-transgenic grafts, is induced by systemic administration of live or killed Listeria monocytogenes or of endotoxin. Graft recipients that reject an E7 graft reject a subsequent E7 graft more rapidly and without further L. monocytogenes exposure, whereas recipients of an E7 graft given without L. monocytogenes do not reject a second graft, even if given with L. monocytogenes. Thus, cross-presentation of E7 from keratinocytes to the adaptive immune system occurs with or without a proinflammatory stimulus, but proinflammatory stimuli at the time of first cross-presentation of Ag can determine the nature of the immune response to the Ag. Furthermore, immune effector mechanisms responsible for rejection of epithelium expressing a tumor Ag in keratinocytes are different from those that reject an E7-expressing transplantable tumor. These observations have implications for immunotherapy for epithelial cancers.

Antibodies against human papillomavirus (HPV) type 16 and 18 E2, E6 and E7 proteins in sera: correlation with presence of papillomavirus DNA

Human papillomavirus (HPV) infection is associated with cervical cancer. The E2 and E1 papillomavirus proteins are expressed at the early stage of infection and regulate DNA replication. The E2 protein activates and represses transcription from different HPVs promoters. At some stage when viral DNA gets integrated into the cellular genome, the E2 gene is disrupted or inactivated. This event leads to a derepression of the E6 and E7 viral oncogenes. These viral proteins are required normally for the maintenance of the malignant phenotype. Therefore, the E2, E6, and E7 proteins are present in all patients infected by papillomavirus. In this study, the association of antibody levels against E2, E6, and E7 proteins of HPV types 16, 18, and 6 was determined in relation to the presence of HPV DNA at the initial stages of HPV infection. Serum samples from 172 women with HPV infection, determined by Papanicolau (Pap) smears and colposcopy, were tested. Elevated antibody titers against E2 protein from the HPV 6 and HPV 16 were detected in 46.42 and 66.96% of the patients, respectively. Antibodies against the E7 and E6 proteins of HPV 16 were found in 51.78 and 36.60% of the patients, respectively. Antibodies against the E6 and E7 proteins of HPV 18 were 35 and 45%, respectively. A statistical difference was found for antibody titers against the E2, E6, and E7 proteins between patients with papillomavirus DNA and controls cases who had no cytological abnormalities and no HPV DNA. Sera titers were 1/500 for patients HPV positive and 1/50 for control individuals. Antibodies titers against E6 and E7 proteins were also examined in patients at 6 and 24 months after cryosurgery. In these patients, a slight decrease in the antibody level against the E2, E6, and E7 proteins was found. No correlation was found between age and number of sexual partners, with serum positivity to the E2, E6, and E7 papillomavirus proteins. These data suggest that antibodies against the E2, E6, and E7 proteins are good candidates for use as markers for monitoring cervical HPV infections.