Characterization of human papillomavirus type 11-specific immune responses in a preclinical model

Immunologic responses to a novel DNA vaccine targeting human papillomavirus-11 E6E7

OBJECTIVES/HYPOTHESIS

Recurrent respiratory papillomatosis (RRP) is a benign disease caused by human papillomavirus (HPV) types 6 and 11. Although a prophylactic vaccine against RRP is available, a therapeutic vaccine is needed to treat those already infected. The objective of our study was to design and test a DNA vaccine targeting HPV11 proteins.

STUDY DESIGN

Preclinical scientific investigation.

METHODS

A DNA vaccine encoding the HPV11 E6 and E7 genes linked to calreticulin (CRT) was generated. Immunologic response to the HPV11 CRT/E6E7 vaccine was measured by vaccinating C57BL/6 mice via electroporation and measuring CD8 + T cell responses from harvested splenocytes. A tumor cell line containing HPV11-E6E7 was created, and the ability of novel DNA vaccine to control tumor growth was measured in vivo.

RESULTS

Our vaccine generated a significant and specific CD8 + T-cell response against the HPV11-E6aa41-70 peptide. The CD8 + T-cell responses did not recognize E7 epitopes, indicating E6 immunodominance. CD8 + responses were augmented in the CRT-linked vaccine compared to a control non-CRT vaccine. The HPV11 CRT/E6E7 vaccine was used to treat mice inoculated with a HPV11 E6E7 expressing tumor cell line after temporary CD3 depletion to facilitate tumor growth. Vaccinated mice had a significantly lower tumor growth rate (P = .029) and smaller tumor volumes compared to control mice, indicating an augmented immunologic response in vaccinated mice.

CONCLUSIONS

A DNA vaccine targeting HPV11 E6E7 generates a specific HPV11 CD-8 + T-cell response capable of reducing the growth of HPV11-expressing tumors. DNA vaccines are a promising immunologic strategy for treating RRP.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:2713-2720, 2017.

Office-based Management of Recurrent Respiratory Papilloma

This review will highlight the indications and benefits of office-based therapy for recurrent respiratory papillomatosis (RRP) and discuss the utilization of photo-dynamic lasers and adjuvant medical therapy in office-based settings. Office-based management of RRP allows for more timely interventions, is preferred by the majority of patients, and negates the risk of general anesthesia. Current literature argues for the utilization of KTP laser over CO₂ laser for office-based treatment of RRP. Medical therapies for RRP are limited, but agents such as bevacizumab are promising and have been shown to reduce disease burden. Medical therapies that can induce disease remission are still needed. Office-based procedures save time and healthcare expenses compared to like procedures in the operating room. However, the increased frequency for office-based procedures predicts similar overall healthcare costs for office-based and OR laser excision of RRP. Office-based management of RRP is a feasible and well-tolerated strategy in appropriately selected patients with adequate local anesthesia.

Identification of the murine H-2D(b) and human HLA-A*0201 MHC class I-restricted HPV6 E7-specific cytotoxic T lymphocyte epitopes

Recurrent respiratory papillomatosis is caused by human papillomavirus (HPV) infection, most commonly types 6 (HPV-6) and 11 (HPV-11). Due to failed host immune responses, HPV is unable to be cleared from the host, resulting in recurrent growth of HPV-related lesions that can obstruct the lumen of the airway within the upper aerodigestive tract. In our murine model, the HPV-6b and HPV-11 E7 antigens are not innately immunogenic. In order to enhance the host immune responses against the HPV E7 antigen, we linked calreticulin (CRT) to HPV-6b E7 and found that vaccinating C57BL/6 mice with the HPV-6b CRT/E7 DNA vaccine is able to induce a CD8+ T cell response that recognizes an H-2D(b)-restricted E7aa21-29 epitope. Additionally, vaccination of HLA-A*0201 transgenic mice with HPV-6b CRT/E7 DNA generated a CD8+ T cell response against the E7aa82-90 epitope that was not observed in the wild-type C57BL/6 mice, indicating this T cell response is restricted to HLA-A*0201. In vivo cytotoxic T cell killing assays demonstrated that the vaccine-induced CD8+ T cells are able to efficiently kill target cells. Interestingly, the H-2D(b)-restricted E7aa21-29 sequence and the HLA-A*0201-restricted E7aa82-90 sequence are conserved between HPV-6b and HPV-11 and may represent shared immunogenic epitopes. The identification of the HPV-6b/HPV-11 CD8+ T cell epitopes facilitates the evaluation of various immunomodulatory strategies in preclinical models. More importantly, the identified HLA-A*0201-restricted T cell epitope may serve as a peptide vaccination strategy, as well as facilitate the monitoring of vaccine-induced HPV-specific immunologic responses in future human clinical trials.

Immunity in head and neck cancer

Head and neck cancers are a diverse group of malignancies that includes an increasing number of virally mediated cancers in addition to tumors caused by tobacco and alcohol use. In both cases, tumor development is intimately related to the host immune system, and the status of an endogenous antitumor response is likely prognostic. Virally mediated cancers provide unique targets for preventive vaccines that generate immune responses directed against virus-associated antigens. Once head and neck tumors develop, they are commonly treated with surgery, radiotherapy, and/or chemotherapy. These treatments are associated with significant toxicities, and despite this, subgroups of patients respond poorly and are likely to relapse and die of their disease. Tumor immunotherapy may allow for improvements in both treatment-associated toxicity and outcome. In addition to providing specific targets for therapeutic vaccines and adoptive therapy, virally associated cancers may also be particularly dependent on immune checkpoints; therefore, immune checkpoint inhibitors are being actively tested for these diseases. Cancers that are not virally mediated may also respond to immunotherapies, and biomarkers that could predict response to immunotherapy irrespective of viral status are being evaluated. Multiple ongoing studies are testing benefits of immunotherapy in the management of metastatic squamous cell carcinoma of the head and neck. Early promising results pave the way for future studies that will expand testing to nonmetastatic diseases and other types of head and neck cancers. Prospects of combining various immunotherapies and more established treatments such as chemotherapy and radiotherapy are very intriguing and may provide synergistic benefits.

Clinical efficiency of quadrivalent HPV (types 6/11/16/18) vaccine in patients with recurrent respiratory papillomatosis

The aim of the study was to assess the clinical efficiency of quadrivalent HPV (types 6/11/16/18) vaccine in patients with recurrent respiratory papillomatosis (RRP). This was a prospective study of patients with RRP treated from January 2009 to July 2012 at the Ear, Nose and Throat Department of the Emergency County Hospital of Cluj-Napoca, Romania. Demographic characteristics, onset of RRP, HPV typing, use and number of cidofovir injections, number of surgeries for RRP per year, and use of human papillomavirus vaccine (types 6, 11, 16, 18) (recombinant, adsorbed)/Silgard® were considered from all the patients included in the study. Charts were reviewed for follow-up after diagnosis, after cidofovir, and after Silgard; all the statistical tests were applied at a significance level of 5%. The recurrences were observed within 27.53 ± 11.24 days after intralesional cidofovir injection. Thirteen patients with recurrence after cidofovir agreed and received Silgard® vaccine. 85% [54.44–99.41] of patients had no recurrences during 1-year follow-up. The recurrence of papillomas was observed in two patients (15%, 95% CI [0.59–45.56]), one with adult-onset RRP and one with juvenile-onset RRP. Both recurrences appeared after the first Silgard dose; one month after the third vaccine dose each patient underwent a new surgery for remaining papillomas with no recurrences at 1-year follow-up visit. Silgard® vaccination had a good effect and proved to be efficient in the treatment of our patients with RRR without appearance of recurrence in 85% of the patients during 1-year follow-up.

Induction of robust cellular immunity against HPV6 and HPV11 in mice by DNA vaccine encoding for E6/E7 antigen

Due to the strong relationship between the Human Papillomavirus (HPV) "high-risk" subtypes and cervical cancers, most HPV-related studies have been focusing on the "high-risk" HPV subtypes 16 and 18. However, it has been suggested that the "low-risk" subtypes of HPV, HPV6 and HPV11, are the major cause of recurrent respiratory papillomatosis and genital warts. In addition, HPV 6 and 11 are also associated with otolaryngologic malignancies, carcinoma of the lung, tonsil, larynx and low-grade cervical lesions. Therefore, development of HPV therapeutic vaccines targeting on subtypes 6 and 11 E6 or E7 are in great need. In this report, we describe two novel engineered DNA vaccines that encode HPV 6 and 11 consensus E6/E7 fusion proteins (p6E6E7 and p11E6E7) by utilizing a multi-phase strategy. Briefly, after generating consensus sequences, several modifications were performed to increase the expression of both constructs, including codon/RNA optimization, addition of a Kozak sequence and a highly efficient leader sequence. An endoproteolytic cleavage site was also introduced between E6 and E7 protein for proper protein folding and for better CTL processing. The expressions of both constructs were confirmed by western blot analysis and immunofluorescence assay. Vaccination with these DNA vaccines could elicit robust cellular immune responses. The epitope mapping assay was performed to further characterize the cellular immune responses induced by p6E6E7 and p11E6E7. The HPV 6 and 11 E6 or E7-specific immunodominant and subdominant epitopes were verified, respectively. The intracellular cytokine staining revealed that the magnitude of IFN-γ and TNF-α secretion in antigen-specific CD8(+) cells was significantly enhanced, indicating that the immune responses elicited by p6E6E7 and p11E6E7 was heavily skewed toward driving CD8(+) T cells. Such DNA immunogens are interesting candidates for further studies on HPV 6 and 11-associated diseases.

Expression Cloning of Recombinant Escherichia coli lacZ Genes Encoding Cytoplasmic and Nuclear β-galactosidase Variants

OBJECTIVES

Nonviral vector can be an attractive alternative to gene delivery in experimental study. In spite of some advantages in comparison with the viral vectors, there are still some limitations for efficiency of gene delivery in nonviral vectors. To determine the effective expression, the recombinant Escherichia coli lacZ genes were cloned into the different variants of pcDNA3.1 and then the mammalian cells were transfected.

METHODS AND MATERIALS

The coding sequences of cytoplasmic and nuclear variants of lacZ gene were inserted downstream of the human cytomegalovirus immediate-early gene promoter of plasmid pcDNA3.1/myc-His C. The new cytoplasmic and nuclear constricts of E. coli β-galactosidase-coding sequences were introduced into HeLa cells with the aid of linear polyethylenimine and at 2 days post-transfection the cells were stained using 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal).

RESULTS

Restriction enzyme analyses revealed the proper insertion of E. coli β-galactosidase-coding sequences into the multiple cloning site of pcDNA3.1/myc-His C. The functionality of the resulting constructs designated pcDNA3.1-cyt.lacZ and pcDNA3.1-nls.lacZ(+) was confirmed by X-gal staining of HeLa cells transfected with these recombinant plasmids. While pcDNA3.1-cyt.lacZ directed the synthesis of cytoplasmically located β-galactosidase molecules, the β-galactosidase protein encoded by pcDNA3.1-nls.lacZ(+) was predominantly detected in the cell nucleus.

CONCLUSION

The expression of cytoplasmic and nuclear variant of LacZ gene confirmed the ability of pcDNA3.1 as versatility nonviral vector for the experimental gene delivery study in mammalian cells.