云南HPV-16型E6、E7基因的突变分析

人乳头瘤病毒(Human papillomavirus,HPV)16型(HPV-16)是引起宫颈癌的一种主要高危型病毒,其2个致癌基因E6和E7的核酸序列变异可能会影响其对宿主细胞的致癌性,已有研究表明其序列突变呈现地域差异性。因此,研究不同地域HPV-16这2个基因的变化情况是宫颈癌流行病学调研的主要内容,也可为研究E6和E7的致癌性积累数据。研究以NCBI登录号为NC_001526.2的HPV-16型病毒的序列为参照,采用Neighbor-joining方法对云南地区74例HPV-16样本的E6、E7的DNA序列构建进化树,结果显示:只有亚洲和欧洲变异亚型,而没有发现非洲1、非洲2、亚-美洲和北美洲这4种变异亚型。DNA序列分析显示:E6的碱基突变以T178G(D25E,59.46%)和T350G(L83V,8.11%)为主,E7的碱基突变主要以A647G(N29S,59.46%)和T846C(同义突变,60.81%)为主。发现E6的新突变有A95G(同义突变,1.35%)和A135G(K11R,1.35%);E7的新突变有C625T(L22F,1.35%)、C627T(同义突变,12.16%)、G689A(G43E,1.35%)、T748G(S63A,1.35%)。此外还发现有一个共突变现象:T178G(D25E,59.46%)-A647G(N29S,59.46%)-T843C(同义突变,21.62%)-T846C(同义突变,60.81%)。     

人乳头瘤病毒16型E6和E7基因及其突变体转化活性的研究

为筛选出可用于研制HPV治疗性疫苗的HPV16型E6和E7基因突变体,故将HPV16型原型株(德国株)E6和E7基因及其各种突变体分别转染Balb/c3T3细胞,观察转染后的细胞在软琼脂培养中的集落形成能力和在裸鼠体内的成瘤能力.结果表明,单独转染和共转染HPV16野生型E6和E7基因的Balb/c3T3细胞系,在软琼脂中呈集落样生长,并在裸鼠体内成瘤;而转染E6基因突变体mE6(50G)、E7基因的两种突变体mE7-1(24G26G)和mE7-3(24G26G67R)以及共转染mE6和mE7-1的Balb/c3T3细胞,在软琼脂培养中极少形成集落,也不能在裸鼠体内成瘤.提示经结构改造后的HPV16 E6和E7基因已失去了对Balb/c3T3细胞的转化活性,而保留了免疫原性,可用于HPV16相关肿瘤治疗性疫苗的构建.     

腺伴随病毒载体介导HPV16 E6E7基因转化人胎食管上皮细胞

为了证实人乳头瘤病毒16型（HPV16）感染与食管鳞状细胞癌发生的关系,构建了包含HPV16E6E7基因的重组腺伴随病毒载体并包装重组病毒,重组病毒感染人胎食管粘膜组织,注射SCID小鼠皮下,在TPA协同下12周左右诱发肿瘤。PCR及打点杂交检测到瘤组织中HPV16E6E7基因的存在,HE染色表明为恶性鳞状上皮癌,培养形态及透射电镜观察证实了瘤组织的上皮来源。以上结果对于阐明食管癌发生的病毒病因、食管癌发生的分子机制以及为食管癌防治提供了理论和实践依据。     

ErbB-2 Receptor Cooperates with E6/E7 Oncoproteins of HPV Type 16 in Breast Tumorigenesis

The ErbB-2 receptor is overexpressed in roughly 30% of human breast cancers. Moreover, approximately 50% of breast cancers are positive for high-risk human papillomaviruses (HPVs), specifically types 16 and 18. Recently, we reported that ErbB-2 cooperates with E6/E7 oncoproteins of HPV type 16 to induce neoplastic transformation of human normal oral epithelial cells. We also demonstrated that E6/E7 of HPV type 16 converts non-invasive breast cancer cells to an invasive form. In order to investigate the effect of ErbB-2/E6/E7 cooperation in breast carcinogenesis, we generated double transgenic mice carrying ErbB-2 and E6/E7 of HPV type 16 under mouse mammary tumor virus (MMTV) and human keratin 14 promoters, respectively. Within six months, these double transgenic mice developed large and extensive invasive breast cancer in comparison to ErbB-2 or E6/E7 singly transgenic mice. Histological analysis of ErbB-2/E6/E7 transgenic mice tumors showed the presence of invasive breast carcinomas. However, the breast tissues from ErbB-2 and E6/E7 transgenic mice showed only in-situ cancer and normal mammary phenotype, respectively. In parallel, we examined the cooperation effect of ErbB-2 and E6/E7 in the human breast cancer cell line, BT20; in comparison to ErbB-2 and E6/E7 alone as well as wild type cells, we found that ErbB 2/E6/E7 together stimulate colony formation and cell migration in the BT20 cell line. Furthermore, we found that β-catenin is constitutively phosphorylated by c-Src and consequently trans-located to the nucleus in ErbB-2/E6/E7-breast cancer cells. These findings provide evidence that the ErbB-2 receptor cooperates with high-risk HPVs in breast tumorigenesis via β-catenin activation.     

Induction of focal epithelial hyperplasia in tongue of young bk6-E6/E7 HPV16 transgenic mice

Squamous cell carcinoma (SCC) of the oral cavity is one of the most common neoplasms in the world. During the past 2 decades, the role of high-risk human papilloma virus (HR-HPV) has been studied and the data supporting HPV as a one of the causative agents in the development and progression of a sub-set of head and neck squamous cell carcinomas (HNSCC) has accumulated. In order to investigate the role of HR-HPV oncogene expression in early epithelial alterations in vivo, we produced transgenic mice expressing HPV16 early region genes from the promoter of the bovine keratin 6 gene (Tg[bK6-E6/E7]). In this article, we demonstrate that E6/E7 transgene was abundantly expressed and cellular proliferation was increased in the middle tongue epithelia of transgenic mice, and that in the same region young (27 weeks old) Tg[bK6-E6/E7] mice spontaneously developed histological alterations, mainly focal epithelial hyperplasia (FEH).     

中国湖北地区HPV16型E6和E7基因变异和进化发生学研究

研究中国湖北地区宫颈癌患者的人乳头瘤病毒16型E6和E7的变异以及HPV16变异体的分布。从宫颈癌患者手术切除标本提取组织DNA,用HPV16 E6和E7特异性引物进行PCR扩增,对扩增的部分E6和E7产物片段进行测序分析。在80例宫颈癌组织DNA中有41例发生E6基因178位核苷酸的突变,突变频率58.75%,相应核苷酸改变为Asp-Glu,E7 647在31例测序样品中有22例发生核苷酸序列A到G改变,使29位氨基酸由Asn变为Ser,突变频率70.97%,结果显示在E6和E7基因的178位和647位核苷酸存在高频率的碱基变异。对E6和E7基因的进化树分析表明,中国湖北地区流行的HPV16病毒株主要为亚洲型变异体(As),其次为欧洲型(E),没有发现非洲-1型(Af-1),非洲-2型(Af-2)和亚洲美洲型(AA)HPV16变异体,中国湖北地区流行的As变异体是否有更高的致宫颈癌的风险还有待于进一步对不同阶段CIN和正常宫颈上皮样品的E6和E7基因进行序列分析和对变异体蛋白进行功能研究。     

Sequential Cisplatin Therapy and Vaccination with HPV16 E6E7L2 Fusion Protein in Saponin Adjuvant GPI-0100 for the Treatment of a Model HPV16+ Cancer

Clinical studies suggest that responses to HPV16 E6E7L2 fusion protein (TA-CIN) vaccination alone are modest, and GPI-0100 is a well-tolerated, potent adjuvant. Here we sought to optimize both the immunogenicity of TA-CIN via formulation with GPI-0100 and treatment of HPV16+ cancer by vaccination after cisplatin chemotherapy. HPV16 neutralizing serum antibody titers, CD4+ T cell proliferative and E6/E7-specific CD8+ T cell responses were significantly enhanced when mice were vaccinated subcutaneously (s.c.) or intramuscularly (i.m.) with TA-CIN formulated with GPI-0100. Vaccination was tested for therapy of mice bearing syngeneic HPV16 E6/E7+ tumors (TC-1) either in the lung or subcutaneously. Mice treated with TA-CIN/GPI-0100 vaccination exhibited robust E7-specific CD8+ T cell responses, which were associated with reduced tumor burden in the lung, whereas mice receiving either component alone were similar to controls. Since vaccination alone was not sufficient for cure, mice bearing s.c. TC-1 tumor were first treated with two doses of cisplatin and then vaccinated. Vaccination with TA-CIN/GPI-0100 i.m. substantially retarded tumor growth and extended survival after cisplatin therapy. Injection of TA-CIN alone, but not GPI-0100, into the tumor (i.t.) was similarly efficacious after cisplatin therapy, but the mice eventually succumbed. However, tumor regression and extended remission was observed in 80% of the mice treated with cisplatin and then intra-tumoral TA-CIN/GPI-0100 vaccination. These mice also exhibited robust E7-specific CD8+ T cell and HPV16 neutralizing antibody responses. Thus formulation of TA-CIN with GPI-0100 and intra-tumoral delivery after cisplatin treatment elicits potent therapeutic responses in a murine model of HPV16+ cancer.     

Induction of senescence-like state and suppression of telomerase activity through inhibition of HPV E6/E7 gene expression in cells immortalized by HPV16 DNA

The E6 and E7 oncoproteins of human papillomavirus (HPV) play a major role in the development of cervical carcinoma. In this study, a recombinant adenovirus that expresses the bovine papillomavirus (BPV) E2, which has been shown to inhibit HPV early gene expression, was delivered to two HPV-immortalized cell lines as well as CaSki, a cervical carcinoma cell line. We tested whether the carcinoma and the immortal cells were equally affected by the expression of BPV E2. In all cell lines, BPV E2-mediated inhibition of HPV E6/E7 expression caused a dramatic suppression of cell growth, being preceded by the activation of the p53-Rb growth-inhibitory pathway, and a decrease in hTERT mRNA expression and telomerase activity. This suggests that the HPV E6 and E7 proteins are required not only for induction of the proliferative phenotype and telomerase activity, but also for their maintenance. In both the carcinoma and the immortal lines, the number of cells with enlarged cytoplasm and senescence-associated beta-galactosidase activity, which are markers for cellular senescence, was significantly increased. These results suggest that a senescence program exists in cells immortalized by HPV DNA as well as in cervical carcinoma cells.     

Increased migration of Langerhans cells in response to HPV16 E6 and E7 oncogene silencing: role of CCL20

Human papillomavirus (HPV) infection, particularly type 16, is causally associated with cancer of the uterine cervix. The persistence or progression of cervical lesions suggests that viral antigens are not adequately presented to the immune system. This hypothesis is reinforced by the observation that most squamous intraepithelial lesions (SILs) show quantitative and functional alterations of Langerhans cells (LC). The infiltration of immature LC in the squamous epithelium is mainly controlled by Macrophage Inflammatory Protein 3α/CCL20. After having shown that CCL20 production is altered in HPV-transformed keratinocytes (KC), the possible role of HPV16 E6 and E7 viral oncoproteins in the reduced CCL20 levels observed in SILs was investigated by silencing HPV16 E6 and E7 oncogenes by RNA interference (siRNA). This treatment not only increased CCL20 secretion but also resulted in the modulation of NF-κB p50, p52 and p65 precursor localization. Moreover, silencing of E6 and E7 oncogenes in HPV16-transformed KC induced a significantly higher migratory capacity of LC in a Boyden chamber assay and in an in vitro formed (pre)neoplastic epithelium reminiscent of high-grade SILs. Anti-CCL20 neutralizing antibody experiments showed that the increased migration of LC is due to the re-expression of CCL20 in E6 and E7 siRNA transfected KC. These data suggest that HPV16 E6/E7-induced down-regulation of CCL20 observed during the cervical carcinogenesis may contribute to a diminished capacity of the immune system to control HPV infection. P. Hubert and J. H. Caberg contributed equally to this work.     

Compromised Spindle Assembly Checkpoint due to Altered Expression of Ubch10 and Cdc20 in Human Papillomavirus Type 16 E6- and E7-Expressing Keratinocytes

Cells expressing human papillomavirus type 16 (HPV-16) E6 and E7 proteins exhibit deregulation of G₂/M genes, allowing bypass of DNA damage arrest signals. Normally, cells with DNA damage that override the G₂ damage checkpoint would precociously enter mitosis and ultimately face mitotic catastrophe and apoptotic cell death. However, E6/E7-expressing cells (E6/E7 cells) have the ability to enter and exit mitosis in the presence of DNA damage and continue with the next round of the cell cycle. Little is known about the mechanism that allows these cells to gain entry into and exit from mitosis. Here, we show that in the presence of DNA damage, E6/E7 cells have elevated levels of cyclin B, which would allow entry into mitosis. Also, as required for exit from mitosis, cyclin B is degraded in these cells, permitting initiation of the next round of DNA synthesis and cell cycle progression. Proteasomal degradation of cyclin B by anaphase-promoting complex/cyclosome (APC/C) is, in part, due to elevated levels of the E2-conjugating enzyme, Ubch10, and the substrate recognition protein, Cdc20, of APC/C. Also, in E6/E7 cells with DNA damage, while Cdc20 is complexed with BubR1, indicating an active checkpoint, it is also present in complexes free of BubR1, presumably allowing APC/C activity and slippage through the checkpoint.Failure to activate cell cycle checkpoints in the presence of any DNA damage leads to genomic instability, polyploidy, and subsequently, aneuploidy, which is a hallmark of many cancers (26). Human papillomaviruses (HPVs) which cause various epithelial cancers, produce two proteins, E6 and E7, whose expression allows bypass or overriding of normal DNA damage and spindle checkpoint signals, primarily through inactivation of p53 and retinoblastoma family members, respectively (11, 16, 17). Our laboratory and others have previously shown that bypass of these arrest signals due to the presence of the viral genes gives rise to a significant population of cells that are polyploid (13, 16, 24, 32). Polyploid and aneuploid cells predominantly arise due to defects in the spindle assembly checkpoint (SAC) during mitosis. While we have some understanding of the mechanisms that lead to bypass of DNA damage arrest signals at the G₂/M stage of the cell cycle, it is not clear how the E6/E7-expressing cells with DNA damage and abnormal chromosomes are allowed to (i) to enter into mitosis and (ii) exit out of mitosis to initiate the next round of replication. Progression through mitosis is regulated by the ubiquitin-dependent degradation machinery, consisting of the anaphase-promoting complex/cyclosome (APC/C), a multisubunit ubiquitin ligase. The activity of APC/C is dependent on the substrate-specifying proteins Cdc20 in metaphase and Cdh1 in telophase (25, 37). In normal cells, spindle checkpoint proteins Mad2 and BubR1 serve to inhibit APC/C until all the chromosomes are aligned correctly on the mitotic spindle by binding Cdc20 and preventing it from activating APC/C (5, 21, 31). In the event of DNA damage and/or unattached kinetochores, the SAC will arrest cells before exit from mitosis by inhibiting activation of APC/C. As a consequence of APC/C inhibition, cyclin B is not degraded, thus preventing cells from mitotic exit (6). Work by Chen''s group (11) has shown that E6- and E7-expressing cells (also referred to here as E6/E7 cells) adapt to an active SAC and are capable of mitotic slippage. So, what is the mechanism that underlies mitotic slippage in E6/E7 cells and allows them to enter the next round of cell cycle? Recent work by van Ree et al. (34) has shown that overexpression of E2 ubiquitin-conjugating enzyme Ubch10 leads to uncontrolled APC/C activity and degradation of cyclin B even in the presence of an active mitotic checkpoint, leading to mitotic slippage. In this report, we show that primary human foreskin keratinocytes (HFKs) expressing E6/E7 have high levels of cyclin B, which allows entry into mitosis in the presence of DNA damage. We show that these cells successfully exit mitosis by, in part, indirect activation of APC/C through upregulation of the E2-conjugating protein, Ubch10, and the substrate-specific component of APC/C, Cdc20, leading to the required degradation of cyclin B. In addition, Cdc20 is detected in different complexes; one includes the protein BubR1, indicating an active checkpoint, while other complexes are free of BubR1 and are thus free to activate APC/C. Upregulation of cyclin B and Ubch10 as well as Cdc20 is primarily through E6 and its ability to target p53 degradation, although inhibition of the pRb family members by E7 may also play a part.     

RNA interference against HPV16 E7 oncogene leads to viral E6 and E7 suppression in cervical cancer cells and apoptosis via upregulation of Rb and p53

The simultaneous expression of human papillomavirus type 16 (HPV16) E6 and E7 oncogenes is pivotal for malignant transformation and maintenance of malignant phenotypes. Silencing these oncogenes is considered to be applicable in molecular therapies of human cervical cancer. However, it remains to be determined whether HPV16 E6 and E7 could be both silenced to obtain most efficient antitumor activity by using RNA interference (RNAi) technology. Herein, we designed a small interfering RNA (siRNA) targeting HPV16-E7 region to degrade either E6, or truncated E6 (E6*) and E7 mRNAs and to simultaneously knockdown both E6 and E7 expression. Firstly, the sequence targeting HPV16-E7 region was inserted into the shRNA packing vector pSIREN-DNR, yielding pSIREN-16E7 to stably express corresponding shRNA. HPV16-transformed SiHa and CaSki cells were used as a model system; RT-PCR, Western Blotting, MTT assay, TUNEL staining, Annexin V apoptosis assay and flow cytometry were applied to examine the effects of pSIREN-16E7. Our results indicated that HPV16-E7 specific shRNA (16E7-shRNA) induced selective degradation of E6 and E7 mRNAs and proteins. E6 silencing induced accumulation of cellular p53 and p21. In contrast, E7 silencing induced hypophosphorylation of retinoblastoma (Rb) protein. The loss of E6 and E7 reduced cell growth and ultimately resulted in massive apoptotic cell death selectively in HPV-positive cancer cells, compared with the HPV-negative ones. We demonstrated that 16E7-shRNA can induce simultaneous E6 and E7 suppression and lead to striking apoptosis in HPV16-related cancer cells by activating cellular p53, p21 and Rb. Therefore, RNAi using E7 shRNA may have the gene-specific therapy potential for HPV16-related cancers.     

Escherichia coli O157:H7 Strains That Persist in Feedlot Cattle Are Genetically Related and Demonstrate an Enhanced Ability To Adhere to Intestinal Epithelial Cells

A longitudinal study was conducted to investigate the nature of Escherichia coli O157:H7 colonization of feedlot cattle over the final 100 to 110 days of finishing. Rectal fecal grab samples were collected from an initial sample population of 788 steers every 20 to 22 days and microbiologically analyzed to detect E. coli O157:H7. The identities of presumptive colonies were confirmed using a multiplex PCR assay that screened for gene fragments unique to E. coli O157:H7 (rfbE and fliC_h7) and other key virulence genes (eae, stx₁, and stx₂). Animals were classified as having persistent shedding (PS), transient shedding (TS), or nonshedding (NS) status if they consecutively shed the same E. coli O157:H7 genotype (based on the multiplex PCR profile), exhibited variable E. coli O157 shedding, or never shed morphologically typical E. coli O157, respectively. Overall, 1.0% and 1.4% of steers were classified as PS and NS animals, respectively. Characterization of 132 E. coli O157:H7 isolates from PS and TS animals by pulsed-field gel electrophoresis (PFGE) typing yielded 32 unique PFGE types. One predominant PFGE type accounted for 53% of all isolates characterized and persisted in cattle throughout the study. Isolates belonging to this predominant and persistent PFGE type demonstrated an enhanced (P < 0.0001) ability to adhere to Caco-2 human intestinal epithelial cells compared to isolates belonging to less common PFGE types but exhibited equal virulence expression. Interestingly, the attachment efficacy decreased as the genetic divergence from the predominant and persistent subtype increased. Our data support the hypothesis that certain E. coli O157:H7 strains persist in feedlot cattle, which may be partially explained by an enhanced ability to colonize the intestinal epithelium.Escherichia coli serotype O157:H7 was first linked to human illness in the early 1980s, when it was determined to cause severe abdominal pain with initially watery diarrhea that progressed to grossly bloody diarrhea accompanied by little or no fever (42). Initially, E. coli O157:H7 can cause nonbloody diarrhea through attachment to, and subsequent destruction of, intestinal microvilli (24). In addition to microvillus damage, serious health complications can arise due to the ability of E. coli O157:H7 to produce Shiga toxins (Stx1 and Stx2). Shiga toxins are very potent cytotoxins that are absorbed into the intestinal microvasculature and initiate apoptosis of vascular epithelium, resulting in hemorrhagic colitis (41). Persistent uptake of these toxins may lead to more severe manifestations of disease, such as hemolytic-uremic syndrome, which may ultimately result in kidney failure (24). Most recent estimates have identified E. coli O157:H7 as the cause of at least 70,000 cases of food-borne illness annually in the United States, and in 4% of cases life-threatening hemolytic-uremic syndrome develops (37). Epidemiological studies have implicated the consumption of meat, dairy products, produce, and water contaminated by animal feces, as well as person-to-person contact and direct contact with farm animals or their environment, as routes of E. coli O157:H7 transmission leading to human illness (36).It is generally accepted that cattle and other animals are the major reservoir of E. coli O157:H7, but it is still not clear if animals are colonized for prolonged periods with E. coli O157:H7 or if they transiently shed this organism following repeated exposure to it through ingestion of contaminated feedstuffs or water or through exposure to other contaminated environmental sources. Based on results of numerous epidemiological studies (4, 6, 21, 30, 32), the prevalence of E. coli O157:H7 in feedlot cattle is highly variable and can range from less than 1% to 80%. Several other studies (7, 8, 23) have found evidence of persistent E. coli O157:H7 colonization in individual cattle, supporting the hypothesis that at least some animals are susceptible to persistent E. coli O157:H7 colonization. Multiple experimental inoculation studies (15, 23, 39, 46) showed that E. coli O157:H7 persists in the bovine gastrointestinal (GI) tract for at least 14 days up to 140 days postinfection. Studies have implicated the lower GI tract and specifically the recto-anal junction (RAJ) as the major location of E. coli O157:H7 colonization and proliferation (9, 12, 23, 39); however, this organism also can be found throughout the bovine GI tract (7, 8, 31, 40, 54).It stands to reason that if the E. coli O157:H7 prevalence in cattle presented for harvest were reduced, there would be a decrease in the probability of beef product contamination, if good manufacturing procedures were used. Although there is consensus concerning the importance of preharvest pathogen mitigation and its role in minimizing entry of E. coli O157:H7 into harvest facilities, there is disagreement about the significance of “supershedders” (animals that excrete large quantities of a pathogen for various amounts of time) for E. coli O157:H7 transmission dynamics at the preharvest level (12, 34, 35, 39). Utilizing statistical modeling, researchers have estimated that, on average, the prevalence of “supershedders” in a population is 4% and that these animals excrete 50 times more E. coli O157:H7 than other animals colonized by this organism (34). Additionally, the same researchers suggested that approximately 80% of E. coli O157:H7 transmission is generated by a few “supershedders” (35).Research by our group discovered a unique association between E. coli O157:H7 prevalence in pen floor fecal pats and carcass contamination by this pathogen (57). When the prevalence in fecal pats from a pen floor exceeded 20%, carcasses of animals from the pen had E. coli O157:H7 prevalence values of 14.3, 2.9, and 0.7% before evisceration, after evisceration, and after final intervention, respectively. However, when the prevalence in pen floor fecal pats was less than 20%, the preeviscerated carcass prevalence value was 6.3%, and there was no detectable E. coli O157:H7 contamination of carcass samples after evisceration and after final intervention (57). Thus, we hypothesize that animals which persistently excrete normal levels of E. coli O157:H7 over prolonged periods (persistent shedders [PS]) rather than animals that periodically shed abnormally high levels (supershedders) are the most significant source of E. coli O157:H7 contamination in the food continuum. Although previous studies suggested that cattle may be persistently colonized by E. coli O157:H7 and shed this organism in their feces for prolonged periods, molecular subtyping data are required to further investigate whether cattle are persistently colonized by the same strain (i.e., molecular subtype) or if they are repeatedly exposed to different strains through contaminated feedstuffs, water, or other environmental sources. Thus, the objectives of this study were to determine if naturally colonized feedlot cattle persistently shed E. coli O157:H7, using combined cultural microbiological analyses, molecular subtyping approaches, and in vitro virulence phenotype assays to probe the factors (agent, host, environment, or a combination of these factors) that contribute to the complex ecology of E. coli O157:H7 persistence at the preharvest level.     

Tobacco Smoke Activates Human Papillomavirus 16 p97 Promoter and Cooperates with High-Risk E6/E7 for Oxidative DNA Damage in Lung Cells

We have previously shown a functional interaction between human papillomavirus type 16 (HPV-16) E6 and E7 oncoproteins and cigarette smoke condensate (CSC) in lung cells suggesting cooperation during carcinogenesis. The molecular mechanisms of such interaction, however, remain to be elucidated. Here we first present evidence showing that cigarette smoke condensate (CSC) has the ability to activate the HPV-16 p97 promoter by acting on the long control region (LCR) in lung epithelial cells. Interestingly, we observed that CSC-induced p97 promoter activation occurs in a dose-dependent manner in both tumor A-549 (lung adenocarcinoma), H-2170 (bronchial carcinoma), SiHa or Hela (cervical carcinoma) cells but not in non-tumor BEAS-2B (bronchial) or NL-20 (alveolar) lung cells unless they ectopically expressed the HPV-16 E6 and E7 oncogenes. In addition, we also observed a significant increase of primary DNA damage in tumor and non-tumor CSC-treated lung cells expressing HPV-16 E6 and E7 oncogenes suggesting a cooperative effect in this process, even though the contribution of E7 was significantly higher. Taken together, our results strongly suggest that tobacco smoke is able to induce the activation of the HPV-16 p97 promoter in cooperation with HPV-16 E6 and E7 oncogenes that, in turn, sensitize lung cells to tobacco smoke-induced DNA damage.     

The Bovine Lactophorin C-Terminal Fragment and PAS6/7 Were Both Potent in the Inhibition of Human Rotavirus Replication in Cultured Epithelial Cells and the Prevention of Experimental Gastroenteritis

Rotaviruses are the leading cause of severe dehydrating diarrhea in children worldwide. We have found that high-M_r glycoprotein fraction (F1) from cow’s milk whey has potent inhibitory activity against human rotavirus (HRV) in cell culture. The present study was undertaken to identify and characterize the components responsible for this inhibitory activity. F1 was initially heated at 95 °C for 30 min, rendering milk antibodies inert, subjected to ammonium sulfate fractionation, and then resolved by two-dimensional polyacrylamide gel electrophoresis. After electroelution, we found that a heat-stable milk protein lactophorin C-terminal fragment (LP16) and bovine milk fat globule membrane protein PAS6/7 strongly inhibited the replication of HRV MO strains in MA104 cells. Furthermore, we found that prophylactic oral administration of F1 once before inoculation of the HRV MO strain obviously prevented the development of diarrhea in vivo. These non-immunoglobulin components are a promising candidate for a prophylactic food additive against HRV infection.     

Human Papillomavirus Type 16 (HPV-16) Virus-Like Particle L1-Specific CD8+ Cytotoxic T Lymphocytes (CTLs) Are Equally Effective as E7-Specific CD8+ CTLs in Killing Autologous HPV-16-Positive Tumor Cells in Cervical Cancer Patients: Implications for L1 Dendritic Cell-Based Therapeutic Vaccines

Papillomavirus-like particles (VLPs) based on L1 capsid protein represent a promising prophylactic vaccine against human papillomavirus (HPV) infections. However, cell-mediated immune responses against this antigen are believed to be of limited therapeutic value in established HPV-infected cervical lesions and, for this reason, have not been intensively investigated in cervical cancer patients. In this study we analyzed and quantified by real-time PCR (RT-PCR) the RNA expression levels of E6, E7, and L1 genes in flash-frozen HPV-16 cervical carcinomas. In addition, the kinetics of expression of E6, E7, and L1 in HPV-16-infected primary cell lines established as long-term cultures in vitro was also evaluated at RNA and protein levels. Finally, in order to evaluate the therapeutic potential of L1-specific CD4⁺ and CD8⁺ T lymphocytes responses in cervical cancer patients, L1 VLP-loaded dendritic cells (DCs) were used to stimulate peripheral blood lymphocytes from cervical cancer patients and such responses were compared to those elicited by the E7 oncoprotein. We show that 22 of 22 (100%) flash-frozen cervical biopsy samples collected from HPV-16-positive cervical cancer patients harbor L1, in addition to E6 and E7 RNA, as detected by RT-PCR. E7 RNA copy number (mean, 176.2) was significantly higher in HPV-16-positive cervical cancers compared to the E6 RNA copy number (mean, 47.3) and the L1 copy number (mean, 58.3) (P < 0.0001 and P < 0.001, respectively). However, no significant differences in expression levels between E6 and L1 were found. Kinetic studies of E6, E7, and L1 RNA and protein expression levels in primary tumors showed a sharp reduction in L1 expression after multiple in vitro passages compared to E6 and E7. Autologous DCs pulsed with HPV-16 VLPs or recombinant full-length E7 elicited strong type 1 L1- and E7-specific responses in CD4⁺ and CD8⁺ T cells from cervical cancer patients. Importantly, L1 VLP-specific CD8⁺ T lymphocytes expressed strong cytolytic activity against autologous tumor cells and were as effective as E7-specific cytotoxic T lymphocytes in lysing naturally HPV-16-infected autologous tumor cells. Taken together, these data demonstrate a consistent expression of L1 in primary cervical tumors and the possibility of inducing effective L1/tumor-specific CD4⁺ and CD8⁺ T-lymphocyte responses in patients harboring HPV-infected cervical cancer. These results may have important implications for the treatment of patients harboring established HPV-infected lesions with L1 VLPs or combined E7/L1 DC-based vaccinations.Human papillomavirus (HPV) infection represents the most important risk factor for the development of cervical cancer. Although more than 100 distinct HPV genotypes have been described, and at least 20 are associated with cervical cancer, HPV type 16 (HPV-16) is by far the most frequently detected in cervical neoplasia regardless of the geographical origin of the patients (4). In the last few years significant advances have been made in the development of candidate prophylactic vaccine against cervical cancer and HPV-related infections. In several large prospective randomized studies, virus-like particles consisting of the HPV-16 and HPV-18 major capsid protein L1 (L1-VLPs) have shown promise in protecting young healthy females against persistent infection with HPV-16 and HPV-18 and their associated cervical intraepithelial neoplasia (reviewed in reference 12). These data strongly suggest that the implementation of large-scale L1-VLP-based prophylactic vaccinations have the potential to dramatically reduce worldwide cervical cancer rates in the years to come.Unfortunately, because HPV infection is endemic in humans and there is a long latency from HPV infection to the development of invasive cervical cancer in women, even if prophylactic L1-based vaccinations are implemented on a worldwide scale today it would take decades to perceive any significant benefit. Consistent with this view, an estimated 5 million cervical cancer deaths will occur in the next 20 years due to existing HPV infections (4, 12). Thus, the current development of therapeutic vaccines for protection against persistent HPV infections, cervical cancer, and its precursor lesions remains an area of great interest.Although the interactions between the host immune system and HPV-infected cells are still not completely understood, several lines of evidence suggest that protection against HPV-related infections by L1-VLP-based vaccines is likely conferred by the generation of high levels of neutralizing antibodies (12, 38). Nevertheless, a potential crucial role of L1-specific T-cell responses and the involvement of T cells in mediating the production of neutralizing antibodies and antiviral effect in infected hosts has been previously hypothesized (8, 24). This point may be particularly noteworthy in patients harboring HPV-infected cervical lesions because several studies have demonstrated the critical importance of both cytotoxic (CD8⁺) and helper (CD4⁺) T cells in achieving clinical responses (1, 5, 16-18, 20, 23). However, limited information is currently available to evaluate whether cell-mediated immune responses to L1-VLP may have any significant therapeutic effect in cervical cancer patients harboring HPV-16 positive tumors. Furthermore, to our knowledge, no direct comparison of the therapeutic efficacy of L1 and E7-specific immune responses against naturally HPV-16-infected cervical cancer have been yet reported in human patients.In the present study we have analyzed and quantified by highly sensitive real-time PCR (RT-PCR) the RNA levels of E6, E7, and L1 in flash-frozen biopsy specimens obtained from HPV-16-infected cervical carcinomas and in short- and long-term primary cultures of HPV-16-positive cervical tumors. In addition, we have studied the kinetics of expression of these genes and proteins during the establishment of HPV-16-positive primary tumors in vitro. Finally, using completely autologous systems of naturally infected HPV-16-positive human tumors, we have carefully studied the phenotype and function of L1-specific CD4⁺ and CD8⁺ T-lymphocyte responses generated by VLP-loaded dendritic cells (DCs) and compared their therapeutic potential to those elicited by DC loaded with the E7 oncoprotein.