1. Human papillomavirus vaccine as a new way of preventing cervical cancer: a dream or the future? February, 2004.
This article gives the background on cervical cancer epidemiology and discusses its link to HPV infection. Then it discusses the current prospects for an HPV vaccine and its implications for the future. Cervical cancer is the major cause of death in women in the third world that are of a reproductive age bracket. In developing countries, national screening programs including pap smears have done wonders for decreasing the rates of cervical cancer. Researchers agree that HPV has a necessary role in the development of cervical cancer. The role of HPV in cervical cancer has been narrowed down to the E6 and E7 proteins, which inactivate certain tumor suppressors to promote un-regulated cell cycle progression. It would be correct to assume that if we could create an effective vaccine against HPV, it would reduce the rates of cervical cancer dramatically. Currently, the best HPV vaccine prospect involves virus-like particles, or empty virus capsids, that induce a high antibody response. The HPV 16 L1 virus-like particle vaccines have been shown to be well-tolerated and to generate a high level of antibodies against HPV. This is very promising because HPV 16 is associated with about 50% of cervical cancer and if this vaccine can reduce or totally prevent HPV-16 infection, then we will see a huge drop in the rates of cervical cancer. The most marvelous point to this article is that this vaccine is not a dream, but the clinical trials are happening right now, and they look promising.
Mandic, A. and T. Vujkov. "Human papillomavirus vaccine as a new way of preventing cervical cancer: a dream or the future?" Annals of Oncology, 15 (2), Feb 2004: 197-200.
2. Human papillomavirus type 16 E6 and E7 cause polyploidy in human keratinocytes and up-regulation of G2-M-phase proteins. February 2004.
It was previously known that E6 can induce abnormal centrosome duplication, leading to genomic instability and aneuploidy. This study shows that introducing E6 and E7 of HPV 16 into primary human keratinocytes leads to polyploidy in those cells. We know that E6 inhibits normal p53 tumor suppressor activity and that E7 inhibits retinoblastoma tumor suppressor gene pRB in the cells. In healthy quiescent cells, p53 and pRB function to inhibit uncontrolled cell growth and mitosis, and when their function is impaired, a variety consequences can lead to genetic instability and furthermore, to cancer. More specifically, it was seen that E6 and E7 lead to amplification of the number of centrosomes as well as Ōlagging chromosomesĶ during cell division. This is probably because E6 and E7 are interfering with checkpoints for G1-S and the G2-M phase transitions. The amplification of centrosomes leads to improper aggregation of chromosomes into daughter cells, resulting in chromosomal instability which is an essential step in a cell becoming cancerous. E6 and E7 have also been shown to deregulate cellular genes such as Plk1, Aurora-A, cdk1, and Nek2, which are known to control the G2-M-phase transition checkpoint.
Patel, D., et al. "Human papillomavirus type 16 E6 and E7 cause polyploidy in human keratinocytes and up-regulation of G2-M-phase proteins." Cancer Research, 64(4), Feb 15 2004: 1299-306.
3. Acquisition of high-level chromosomal instability is associated with integration of human papillomavirus type 16 in cervical keratinocytes. February 2004.
It is known that HPV 16 protein E7 can adversely affect the host cell by deregulating important inhibitors of cell growth. Most importantly, it binds to and inactivates cellular pRB tumor suppressor, which normally inhibits cell cycle progression. Although there is nearly a 100% correspondence between HPV infection and cervical cancer, HPV infection does not guarantee the development of cervical cancer. This article sheds light on a particular HPV 16 virus-host cell interaction that makes the transformation of a normal cell into a cancerous cell more likely. It is known that chromosomal instability occurs when E7 is over-expressed in host cells, but it is not clear what leads to the over-expression of E7. It was thought that it was due to either a deregulation of the virus genome promoter or loss of a viral E7 transcriptional repressor from integration into an unstable host cell genome. In this study, researchers cultured a line of cells from a low-grade squamous intraepithelial lesion that acquired HPV 16 by natural infection. Cells from the long term cultures showed that the HPV 16 DNA was in fact integrated into the host genome, whereas those in culture for a shorter time had much less integration frequency and just contained HPV 16 episomes. They showed that the integration of the HPV 16 genome is associated with a 3Õ deletion of the E2 transcriptional repressor for E7, which results an increase in E17 protein levels. They also showed that the high-level chromosomal instability occurs only after integration. Thus, they concluded that this integration step is a critical event for the progression to cervical cancer because it gives rise to chromosomal instabilities that are necessary for transformation to malignancy. The integration step is crucial because the E2 transcriptional regulator is lost and E7 is thus produced in excess.
Pett, MR., et al. "Acquisition of high-level chromosomal instability is associated with integration of human papillomavirus type 16 in cervical keratinocytes." Cancer Research, 64 (4), Feb 15 2004: 1359-68.
4. Vaccination with a DNA vaccine encoding herpes simplex virus type 1 VP22 linked to antigen generates long-term antigen-specific CD8-positive memory T cells and protective immunity.
Typically, vaccines using injection of naked viral genome have been limited in that they can give rise to only a limited number of antigen expressing cells because they lack the intrinsic ability to amplify and spread in vivo. This study uses a clever means to achieve a greater number of antigen-presenting cells by mixing viral genomic naked DNA components in order to create a more potent vaccination effect for HPV 16. Researchers linked the genes for HPV 16 E7 protein to the gene for herpes simplex virus type 1 VP22 protein. They knew that an HPV E7 antigen would be more readily spread between host cells if it were fused to a VP22 protein that is better at moving to other cells. In the study, mice were intradermally vaccinated with this naked fused DNA by a gene gun, and results showed that the HPV antigen liked to the HSV VP22 protein spread within the epithelium, leading to an enhanced CD8+ T cell immune response. They looked at the number of antigen-expressing dendritic cells in the draining lymph nodes of vaccinated mice to see whether the linkage strategy would influence the ability of antigen-expressing dendritic cells to activate antigen-specific CD8+ T cells in vivo. The mice vaccinated with the VP22 linked HPV E7 antigen had more E7 antigen-presenting dendritic cells than the mice vaccinated with the E7 protein alone. Another benefit to this strategy was that the linked gene vaccination improved the MHC 1 presentation of E7 antigen in the dendritic cells transfected with the vaccine and led to enhanced activation of the E-7 specific CD8+ T cells. They also observed an enhancement in the number of E7-specific CD8+ memory T cells produced and thus a greater long-term protective immunity against E-7 expressing tumors.
Kim, TW, et al. "Vaccination with a DNA vaccine encoding herpes simplex virus type 1 VP22 linked to antigen generates long-term antigen-specific CD8-positive memory T cells and protective immunity." Human Gene Therapy, 15(2), Feb 2004: 167-77.
5. Oral immunogenicity of human papillomavirus-like particles expressed in potato. August 2003.
Human papillomavirus has been shown to play a major role in progression to cervical cancer. Research has shown that HPV virus-like particles hold considerable promise for an HPV vaccine. In this case, the HPV L1 major capsid protein can self-assemble into a empty capsid-like structures that can induce immunogenicity similar to infectious virions. These HPV virus-like particles have shown considerable promise as a parenteral vaccine for the prevention of cervical cancer and precursor lesions. However, there is a foreseeable problem with parenteral vaccines because they are expensive to produce and deliver, making them difficult to use in the developing world where the prevalence of cervical HPV disease is high. An attractive alternative is an oral vaccine, which could be grown in transgenic plants in these developing countries. This lab attempted to develop a genetically-altered tobacco and potato plant that expressed the HPV 11 L1 major capsid protein. Results showed that the plants successfully produced the L1 protein and that removing the carboxyl-terminal nuclear localization sequence enhanced L1 expression. The L1 proteins expressed by the plant properly self-assemble into VLPÕs that elicited an immune response comparable to the natural HPV virion. The immune responses against the oral and parenteral vaccines were comparable. This response was enhanced with oral boosts of pure VLP from insect cells. This study showed that HPV L1 proteins can be expressed in genetically engineered plants and that these proteins elicit an immune response against the VLPÕs that could possibly provide protective humoral immunity to HPV.
Warzecha, H, et al. "Oral immunogenicity of human papillomavirus-like particles expressed in potato." Journal of Virology, 77(16), Aug 2003: 8702-11.
6. Antiretroviral therapy and the clinical evolution of human
papillomavirus-associated genital lesions in HIV-positive women. March 2004.
This study examined the effect of antiretroviral therapy on the natural history of HPV-associated genital lesions in 201 women who were infected with HIV. Using PCR on cells obtained through Pap smears, evidence of HPV infection was repeatedly found in 126 women and transiently found in 29. Genital lesions were observed in 137 women, regardless of the type of antiretroviral regimen the patient was receiving. Regression of low-grade lesions was more prevalent among patients receiving highly active ART than among those receiving another type of ART, but this difference was not observed for high-grade lesions, which regressed regardless of the type of regimen. HPV infection persisted in nearly 80% of the cases. Antiretroviral therapy does not seem to prevent the development of genital lesions, nor does it eliminate HPV infection. Pap smears and detection of PHV infection continue to be an important part of a womanÕs gynecological health care, even if she is on an antiretroviral regimen.
Del Mistro, A, et al. "Antiretroviral therapy and the clinical evolution of human papillomavirus-associated genital lesions in HIV-positive women." Clinical Infectious Disease, 38 (5), Mar 1 2004: 737-42.
7. Phase I/II trial of immunogenicity of a human papillomavirus (HPV) type 16 E7 protein-based vaccine in women with oncogenic HPV-positive cervical intraepithelial neoplasia. February 2004.
This study tested the immunogenicity of a fusion protein (PD-E7), which was made up of a mutated HPV-16 E7 protein linked to the first 108 amino acids of Haemophilus influenzae protein D, in patients with oncogenic HPV-positive cervical intraepithelial neoplasia (CIN). Vaccination, not placebo injection, elicited a systemic specific immune response in the majority of patients. The responses included increase IFN-gamma CD8(+) cell responses and long-term T-cell immunity toward the vaccine antigen and E7, as well as a weak H. influenzar protein D-directed CD4(+) response. All the vaccinated patients, but not those receiving the placebo, made significant E7- and PD-specific IgG. These promising results encourage further research into the PD-E7/AS02B vaccine.
Hallez, S, et al. "Phase I/II trial of immunogenicity of a human papillomavirus (HPV) type 16 E7 protein-based vaccine in women with oncogenic HPV-positive cervical intraepithelial neoplasia." Cancer Immunology and Immunotherapy, Feb 17 2004.
8. Comparison of HPV DNA vaccines employing intracellular targeting strategies. February 2004.
This study sought to compare the efficacy and potency of various DNA vaccines that used different intracellular targeting strategies to deliver HPV-16 E7 to subcellular compartments to stimulate antigen processing and presentation to T cells. The strategies that they examined include the following: use of the sorting signal of lysosome-associated membrane protein (LAMP-1), Mycobacterium tuberculosis heat-shock protein 70 (HSP70), calreticulin (CRT) and the translocation domain (dII) of Pseudomonas aeruginosa exotoxin A (ETA). All of these strategies elicited an enhancement in E7-specific CD8(+) T-cell responses and strong antitumor effects against an E7-expressing tumor. The strategy that was the most effective was the use of CRT in the pcDNA3-CRT/E7 vaccine. It generated the highest number of E7-specific CD8(+) T cells and potent long-term protection and treatment effect against E7-expressing tumors in mice. This vaccine also was capable of protecting against an E7-expressing tumor with downregulated MHC class I expression, which is common in HPV-associated cervical cancers. These data suggest that this vaccine may be viable for human trials for the control of HPV infections and HPV-associated lesions.
Kim, JW. "Comparison of HPV DNA vaccines employing intracellular targeting strategies." Gene Therapy, Feb 26 2004.
9. A phase II trial of interleukin-12 in patients with advanced cervical cancer: clinical and immunologic correlates; Eastern Cooperative Oncology Group study E1E96. March 2004.
This study looked at the ability of IL-12, a potent immunopotentiator of T-cell function, to improve the lymphoproliferative response in patients with metastatic, recurrent, or inoperable cervical cancer. The ability to mount a lymphoproliferative response to peptides derived from HPV oncoproteins E6 and E7 is associated with regression of dysplastic cervical lesions and loss of associated HPV infection. In this study, IL-12 treatment was associated with improved lymphoproliferative responses to HPV 16 E4, E6, and E7 peptides, but this improved response was not associated with enhanced objective response or survival. This is the first clinical trial to show induction of cell-mediated immune responses to specific antigens following treatment with IL-12 in women with cervical cancer.
Wadler, S. "A phase II trial of interleukin-12 in patients with advanced cervical cancer: clinical and immunologic correlates; Eastern Cooperative Oncology Group study E1E96." Gynecological Oncology, 92 (3), Mar 2004: 957-64.
10. Recombinant Kunjin virus replicon vaccines induce protective T-cell immunity against human papillomavirus 16 E7-expressing tumour. February 2004.
Because HPV-associated cervical cancer cells express the HPV protein E7, it can be used as a tumor-specific antigen against which vaccines can be directed. This study inserted an epitope of HPV E7 that is recognized by CTLs into a polyepitope encoded by a vector from the flavivirus Kunjin (KUN). This induced E7-specific T-cell responses and protected mice against a challenge with an E7-expressing tumor. Along with the E7 epitope, there were other epitopes in the polyepitope that induced T-cell responses. The KUN replicon vector system appears to be effective in inducing protective immunity towards a virally encoded human tumor-specific antigen and for inducing multi-epitopic CTL responses.
Herd, KA. "Recombinant Kunjin virus replicon vaccines induce protective T-cell immunity against human papillomavirus 16 E7-expressing tumour." Virology, 319 (2), Feb 20 2004: 237-48.