Cross-typic specificity and immunotherapeutic potential of a human HPV16 E7-specific CTL line

Design of a Synthetic Long Peptide Vaccine Targeting HPV-16 and -18 Using Immunoinformatic Methods

Human papillomavirus types 16 and 18 cause the majority of cervical cancers worldwide. Despite the availability of three prophylactic vaccines based on virus-like particles (VLP) of the major capsid protein (L1), these vaccines are unable to clear an existing infection. Such infected persons experience an increased risk of neoplastic transformation. To overcome this problem, this study proposes an alternative synthetic long peptide (SLP)-based vaccine for persons already infected, including those with precancerous lesions. This new vaccine was designed to stimulate both CD8+ and CD4+ T cells, providing a robust and long-lasting immune response. The SLP construct includes both HLA class I- and class II-restricted epitopes, identified from IEDB or predicted using NetMHCPan and NetMHCIIPan. None of the SLPs were allergenic nor toxic, based on in silico studies. Population coverage studies provided 98.18% coverage for class I epitopes and 99.81% coverage for class II peptides in the IEDB world population's allele set. Three-dimensional structure ab initio prediction using Rosetta provided good quality models, which were assessed using PROCHECK and QMEAN4. Molecular docking with toll-like receptor 2 identified potential intrinsic TLR2 agonist activity, while molecular dynamics studies of SLPs in water suggested good stability, with favorable thermodynamic properties.

Synthetic Peptides with Inadvertent Chemical Modifications Can Activate Potentially Autoreactive T Cells

The human CD8+ T cell clone 6C5 has previously been shown to recognize the tert-butyl-modified Bax161-170 peptide LLSY(3-tBu)FGTPT presented by HLA-A*02:01. This nonnatural epitope was likely created as a by-product of fluorenylmethoxycarbonyl protecting group peptide synthesis and bound poorly to HLA-A*02:01. In this study, we used a systematic approach to identify and characterize natural ligands for the 6C5 TCR. Functional analyses revealed that 6C5 T cells only recognized the LLSYFGTPT peptide when tBu was added to the tyrosine residue and did not recognize the LLSYFGTPT peptide modified with larger (di-tBu) or smaller chemical groups (Me). Combinatorial peptide library screening further showed that 6C5 T cells recognized a series of self-derived peptides with dissimilar amino acid sequences to LLSY(3-tBu)FGTPT. Structural studies of LLSY(3-tBu)FGTPT and two other activating nonamers (IIGWMWIPV and LLGWVFAQV) in complex with HLA-A*02:01 demonstrated similar overall peptide conformations and highlighted the importance of the position (P) 4 residue for T cell recognition, particularly the capacity of the bulky amino acid tryptophan to substitute for the tBu-modified tyrosine residue in conjunction with other changes at P5 and P6. Collectively, these results indicated that chemical modifications directly altered the immunogenicity of a synthetic peptide via molecular mimicry, leading to the inadvertent activation of a T cell clone with unexpected and potentially autoreactive specificities.

Identification of the impact on T- and B- cell epitopes of human papillomavirus type-16 E6 and E7 variant in Southwest China

Cervical cancers almost are infected by human papillmavirus (HPV), encoding E6 and E7 oncoproteins which are regard as ideal targets on the mechanism of this disease and development of vaccines. HLA (human leukocyte antigen) participates in the local immune response to prevent tumor invasion and progression. But due to highly polymorphism of HLA, prediction shows its importance in this study. More effective immunoinformatics was used for predicting epitopes from HPV-16 E6 and E7, including T- and B-cell epitopes. Eight substitutions are detected. Specifically speaking, for HLA-I, HLA-A*33:03 (26), HLA-B*13:01 (14), HLA-C*03:02 (5) for E6 and HLA-A*02:01 (6), HLA-B*40:01 (5), HLA-C*03:04 (4) for E7 are most frequency. Epitope _41-48EVYDFAFR for HLA-A*33:03 (0.1) for E6 has best binding affinity, as well as HLA*02:01 and HLA-B*40:01 (0.2) for E7. The mutations of D25E and L83V of E6 and N29S of E7 produce new epitopes, and the percentile values change with them. For HLA-II, seventeen epitopes in the reference at percentile value from 0.22 to 4.76, while in variant from 0.22 to 4.96. For the B-cell epitopes, three most potent epitopes for E6 were listed, and N29S lead the growth of score from 0.81 to 0.83. In summary, E6_40-55REVYDFAFRDLCIVYR and E7_11-22YMLDLQPETTDL are the important regions, containing the majority of predicted epitopes. E6 72-83 for HLA-A*02:01 and E6 74-84 for HLA-B*15:02 maybe are the new direct for therapeutic vaccine aimed at L83V variants. HLA-DRB1*15:02 is better binder with T cell in our HLA class II. It is a systematic, detail recognition for T- and B-cell epitopes of HPV-16 E6 and E7 from Southwest China, which may be helpful to design vaccines specifically for women in Southwest China and testing methods specifically for this region. The results of our study may contribute to future researches on vaccines improvement, or screening methods for a particular population.

Cytolytic activity of the human papillomavirus type 16 E711-20 epitope-specific cytotoxic T lymphocyte is enhanced by heat shock protein 110 in HLA-A*0201 transgenic mice

Heat shock proteins (HSPs) have been successfully applied to a broad range of vaccines as biological adjuvants to enhance the immune response. The recently defined HSP110, in particular, exhibits strong protein binding affinity and is capable of enhancing the immunogenicity of protein antigens remarkably more than other HSP family members. In our previous study, we verified that murine HSP110 (mHSP110) significantly enhanced the immune response of a C57BL/6 mouse model to the H-2(d)-restricted human papillomavirus (HPV) E749-57 epitope (short peptide spanning the 49th to 57th amino acid residues in the E7 protein). To determine whether HSP110 similarly enhances the immunogenicity of human epitope peptides, we used the HLA-A2 transgenic mouse model to investigate the efficacy of the mHSP110 chaperone molecule as an immunoadjuvant of the human HLA-A2-restricted HPV16 E711-20 epitope vaccine. Results showed that mHSP110 efficiently formed a noncovalently bound complex with the E711-20 epitope. The mHSP110-E711-20 complex induced epitope-specific splenocyte proliferation and E711-20-specific gamma interferon (IFN-γ) secretion. Importantly, cytotoxic T lymphocytes primed by the mHSP110-E711-20 complex exerted strong cytolytic effects on target T2 cells pulsed with the E711-20 peptide or TC-1 cells transfected with the HLA-A2 gene. In addition, the mHSP110-E711-20 complex elicited stronger ex vivo and in vivo antitumor responses than either emulsified complete Freund's adjuvant or HSP70-chaperoned E711-20 peptide. These collective data suggest that HSP110 is a promising immunomodulator candidate for peptide-based human cancer vaccines, such as for the HLA-A2-restricted E711-20 epitope.

HPV-16 E6 and E7 protein T cell epitopes prediction analysis based on distributions of HLA-A loci across populations: an in silico approach

Human papillomavirus type 16 (HPV-16) is the most prevalent virus in human cervical cancers, as it is present in more than half of all cases. Many studies have found continued expression of E6 and E7 proteins in the majority of cervical cancer cases, but not in normal tissues. These results indicated that the E6 and E7 proteins could be ideal candidate therapeutic vaccines against HPV-16 infection and cervical cancer. Using the Immune Epitope Database Analysis Resource, cytotoxic T lymphocyte (CTL) epitopes of the HPV-16 E6 and E7 proteins were predicted according to worldwide frequency distributions of HLA-A alleles (HLA-A*01:01, -A*02:01, -A*02:06, -A*03:01, -A*11:01, -A*24:02, -A*26:01, -A*31:01 and -A*33:03). Our results predicted a total of 81 epitopes of HPV-16 E6 (n=59) and E7 (n=22). Epitope cluster analysis showed that among the 20 clusters of HPV-16 E6, cluster 3 contained the most epitopes (10 epitopes), which was represented by HLA-A*31:01 and -A*33:03. Of the 10 clusters of HPV-16 E7, cluster 3 contained the most epitopes (5 epitopes), which was represented by HLA-A*01:01 and -A*26:01. Our results indicated that the combination of epitopes FAFRDLCIVYR₅₂₋₆₂ of E6 (HLA-A*02:06, HLA-A*31:01, and HLA-A*33:03), PYAVCDKCLKF₆₆₋₇₆ of E6 (HLA-A*11:01 and HLA-A*24:02), HGDTPTLHEY₂₋₁₁ of E7 (HLA-A*01:01 and HLA-A*26:01), and YMLDLQPETT₁₁₋₂₀ of E7 (HLA-A*02:01) could vaccinate >50% of all individuals worldwide. Our results propose CTL epitopes or combinations of them predicted in current study for candidate therapeutic vaccines to effectively control HPV-16 infection and development of cervical cancer.

A novel tumor antigen derived from enhanced degradation of bax protein in human cancers

Cancer cells frequently exhibit defects in apoptosis, which contribute to increased survival and chemotherapeutic resistance. For example, genetic mutations or abnormal proteasomal degradation can reduce expression of Bax which limits apoptosis. In cancers where abnormal proteasomal degradation of Bax occurs, we hypothesized that Bax peptides that bind to human leukocyte antigen (HLA) class I molecules would be generated for presentation to CD8(+) T cells. To test this hypothesis, we generated T cells against pooled Bax peptides, using the blood of healthy human donors. Although T-cell responses were of low frequency (0.15%), a CD8(+) T-cell clone (KSIVB17) was isolated that optimally recognized Bax(136-144) peptide (IMGWTLDFL) presented by HLA-A*0201. KSIVB17 was able to recognize and kill a variety of HLA-matched cancer cells including primary tumor cells from chronic lymphocytic leukemia (CLL). No reactivity was seen against HLA-matched, nontransformed cells such as PHA blasts and skin fibroblasts. Furthermore, KSIVB17 reactivity corresponded with the proteasomal degradation patterns of Bax protein observed in cancer cells. Taken together, our findings suggest a new concept for tumor antigens based on regulatory proteins that are ubiquitously expressed in normal cells, but that have abnormally enhanced degradation in cancer cells. Bax degradation products offer candidate immune antigens in cancers such as CLL in which increased Bax degradation correlates with poor clinical prognosis.

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.

Ubiquitination in host immune response to human papillomavirus infection

Human papillomavirus (HPV) infection with low-risk or high-risk subtypes is very common. Infection with HPVs is often a major causative factor for the development of cutaneous benign lesions, cervical cancer, and a number of other tumors. The mechanisms of host immunity to prevent and control HPV infection still remain unclear. The importance of ubiquitination (or ubiquitylation) as an intracellular proteasomal-mediated protein degradation pathway, and as an important modulator for the regulation of many fundamental cellular processes has been valued over the last decade. Although the molecular and cellular mechanisms are not completely established, the critical role of ubiquitination in host immune response to HPV infection has become increasingly apparent. This review summarizes current knowledge on the possible role that ubiquitination plays in regulating the host immune response during HPV infection. Targeting the components of the ubiquitin system might offer potential therapeutic strategies for HPV-related diseases in the future.

HPV-16 E5 down-regulates expression of surface HLA class I and reduces recognition by CD8 T cells

HPV-16 is the major causes of cervical cancer. Persistence of infection is a necessary event for progression of the infection to cancer. Among other factors, virus persistence is due the viral proteins fighting the immune response. HPV-16 E5 down-regulates MHC/HLA class I, which is much reduced on the cell surface and accumulates in the Golgi apparatus in cells expressing E5. This effect is observed also in W12 cells, which mimic early cervical intraepithelial progression to cervical cancer. The functional effect of MHC I down-regulation on human CD8 T cells is not known, because of the need for HLA-matched, HPV-specific T cells that recognise E5 expressing-cells. Here we employ a heterologous cell/MHC I system which uses mouse cells expressing both E5 and HLA-A2, and A2-restricted CTLs; we show that the E5-induced reduction of HLA-A2 has a functional impact by reducing recognition of E5 expressing cells by HPV specific CD8+ T cells.

Immunogenicity and safety profiles of genetic vaccines against human Her-2/neu in cynomolgus monkeys

Her-2/neu is a well-characterized tumor-associated antigen, the overexpression of which in human carcinomas correlates with a poor prognosis. Here, we evaluated Her-2/neu-specific humoral and cellular immune responses in immunized monkeys after immunization with nonreplicating adenovirus (AdHM) expressing the extracellular and transmembrane domain of human Her-2/neu (HM) and/or naked DNA vaccine (pHM-hGM-CSF) expressing human granulocyte-macrophage colony-stimulating factor together with HM. Priming of monkeys with AdHM generated Her-2/neu-specific long-lasting antibody production. Furthermore, these Her-2/neu-specific antibodies produced by AdHM immunization, some of which shared epitope specificity with Herceptin, were able to induce antibody-dependent cellular cytotoxicity against Her-2-expressing target cells. Cellular immune responses were elicited in all monkeys immunized with Her-2/neu-expressing vaccine; interferon-gamma was secreted when these splenocytes were restimulated with Her-2/neu-expressing autologous cells, and immunization with AdHM induced Her-2/neu-specific lymphoproliferative responses. Further, immunization with pHM-hGM-CSF before AdHM immunization noticeably enhanced cytotoxic T-lymphocyte activity. In addition, we observed no abnormalities that would indicate that the genetic vaccines had toxic effects in the immunized monkeys. Thus, we can conclude that our genetic vaccines efficiently elicited Her-2/neu-specific humoral and cellular immune responses without causing severe adverse effects in nonhuman primates and that as such they warrant further clinical investigation.

'1-8 interferon inducible gene family': putative colon carcinoma-associated antigens

D^b−/−xβ2 microglobulin (β2m) null mice transgenic for a chimeric HLA-A2.1/D^b-β2m single chain (HHD mice) are an effective biological tool to evaluate the antitumour cytotoxic T-lymphocyte response of known major histocompatibility-restricted peptide tumour-associated antigens, and to screen for putative unknown novel peptides. We utilised HHD lymphocytes to identify immunodominant epitopes of colon carcinoma overexpressed genes. We screened with HHD-derived lymphocytes over 500 HLA-A2.1-restricted peptides derived from colon carcinoma overexpressed genes. This procedure culminated in the identification of seven immunogenic peptides, three of these were derived from the ‘human 1-8D gene from interferon inducible gene’ (1-8D). The 1-8D gene was shown to be overexpressed in fresh tumour samples. The three 1-8D peptides were both antigenic and immunogenic in the HHD mice. The peptides induce cytotoxic T lymphocytes that were able to kill a colon carcinoma cell line HCT/HHD, in vitro and retard its growth in vivo. One of the peptides shared by all the 1-8 gene family primed efficiently normal human cytotoxic T lymphocyte precursors. These results highlight the 1-8D gene and its homologues as putative immunodominant tumour-associated antigens of colon carcinoma.

Activated B cells mediate efficient expansion of rare antigen-specific T cells

Potent professional antigen-presenting cells (APC) are essential tools to activate and expand antigen-specific T cells in vitro for use in adoptive immunotherapy. CD40-activated B cells can be easily generated and propagated from human donors and have been successfully used to generate antigen-specific T-cell cultures. Here we show that CD40-activated B cells strongly and specifically expand rare populations of antigen-specific CD8 T cells, with frequencies of less than 1 in 20,000 CD8 T cells in peripheral blood. We focused on T cells recognizing an epitope from the human papillomavirus 16 (HPV-16) E7 protein. In 6 of 6 healthy donors, epitope-specific CD8+ T cells were found to be "rare" by this criterion, as shown by staining with human leukocyte antigen (HLA)/peptide multimers. Using peptide-loaded CD40-activated B cells, epitope-specific T cells could be selectively expanded in all donors up to 10(6) fold, and the resulting T-cell cultures contained up to 88% specific T cells. These results strongly encourage the use of CD40-stimulated B cells as APCs in immunotherapy.

Detection of human papillomavirus type 18 E6 and E7-specific CD4+ T-helper 1 immunity in relation to health versus disease

The most common high-risk human papillomavirus types, HPV16 and 18, differ markedly with respect to their interaction with the host. Clearance of HPV18 infections generally takes longer and HPV18-positive cancers have a poorer prognosis. We therefore evaluated Th1-type immunity against the E6 and E7 oncoproteins of HPV18 in healthy subjects and in patients with HPV18-positive genital cancer, and compared the results to our previously obtained data for HPV16. Approximately 20% of the healthy individuals displayed immunity against HPV18 E6. In contrast, none of the patients showed such responses, despite the presence of HPV18-positive lesions. Several of the patients did respond to HPV18 E7, whereas this immunity is rarely found in healthy subjects. This pattern of immune reactivity is essentially similar to that previously found for HPV16. It is unlikely that this similarity is the result of immunological cross-reactivity between the E6 and E7 antigens of HPV types 16 and 18. Our data confirm the relation between failure of E6-specific Th1 immunity and high-risk HPV-induced cervical neoplasia and argue that parameters other than these determine the differences in pathological impact between HPV types 16 and 18.