HPV-16 targeted DNA vaccine expression: The role of purification.

DNA vaccines have come to light in the last decades as an alternative method to prevent many infectious diseases, but they can also be used for the treatment of specific diseases, such as cervical cancer caused by Human Papillomavirus (HPV). This virus produces E6 and E7 oncoproteins, which alter the cell cycle regulation and can interfere with the DNA repairing system. These features can ultimately lead to the progression of cervical cancer, after cell infection by HPV. Thus, the development of a DNA vaccine targeting both proteins arises as an interesting option in the treatment of this pathology. Nonetheless, before evaluating its therapeutic potential, the purity levels of a biopharmaceutical must meet the regulatory agency specifications. Previously, our research group successfully purified the supercoiled isoform of the recombinant HPV-16 E6/E7 DNA vaccine with virtual 100% purity by affinity chromatography. The present work was designed to evaluate the effect that pDNA sample purity levels may exert in the expression of a target protein. Thus, in vitro studies were performed to assess the vaccine ability to produce the target proteins and to compare the expression efficiency between the pDNA sample obtained by affinity chromatography, which only presents the sc isoform and fulfils the regulatory agency recommendations, and the same DNA vaccine retrieved by a commercial purification kit, which contains different pDNA isoforms. Our achievements suggest that the E6/E7 DNA vaccine purified by affinity chromatography promotes higher E6 and E7 mRNA and protein expression levels than the DNA vaccine purified with the commercial kit. Overall, these results underline the importance that a purification strategy may present in the therapeutic outcome of recombinant DNA vaccines, envisaging their further application as biopharmaceuticals. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:546-551, 2018.

A longitudinal study of human papillomavirus 16 L1, e6, and e7 seropositivity and oral human papillomavirus 16 infection.

BACKGROUND: Individuals with human papillomavirus (HPV) infections can develop IgG antibodies to HPV proteins including the L1 capsid and E6 and E7 oncoproteins. Evidence on whether L1 antibodies reduce the risk of cervical HPV infection is mixed, but this has not been explored for oral HPV infections. Antibodies to HPV16's E6 oncoprotein have been detected in some oropharyngeal cancer cases years before cancer diagnosis, but it is unknown if these antibodies are associated with oral HPV16 DNA. METHODS: Enzyme-linked immunosorbent assays tested for serum antibodies to HPV16's L1 capsid in 463 HIV-infected and 293 HIV-uninfected adults, and for antibodies to recombinantly expressed E6 and E7 oncoproteins to HPV16 in 195 HIV-infected and 69 HIV-uninfected cancer-free participants at baseline. Oral rinse samples were collected semiannually for up to 3 years and tested for HPV DNA using PGMY 09/11 primers. Adjusted Poisson, logistic, and Wei-Lin-Weissfeld regression models were used. RESULTS: Human papillomavirus 16 L1 seroreactivity did not reduce the subsequent risk of incident oral HPV16 infection in unadjusted (hazard ratio, 1.4; 95% confidence interval, 0.59-3.3) or adjusted (adjusted hazard ratio = 1.1; 95% confidence interval, 0.41-3.0) analysis. Antibodies to HPV16 E6 and E7 oncoproteins were detected in 7.6% and 3.4% of participants, respectively, but they were not associated with baseline oral HPV16 DNA prevalence or oral HPV16 persistence (each P > 0.40). CONCLUSIONS: Naturally acquired HPV16 L1 antibodies did not reduce the risk of subsequent oral HPV16 infection. Human papillomavirus 16 E6 and E7 seropositivity was not a marker for oral HPV16 infection in this population without HPV-related cancer.

Targeting of the HPV-16 E7 protein by RNA aptamers.

The expression of high-risk human papillomavirus E6 and E7 proteins in most cervical tumors raised a considerable interest in the diagnostic and therapeutic applications of functional oligonucleotides (i.e., DNAzymes, ribozymes, and aptamers) directed against HPV targets. Aptamers are short single-stranded oligonucleotides that specifically recognize a wide variety of molecular targets, including HPV proteins. Here, we describe a protocol for the successful isolation of RNA aptamers directed at the recombinant HPV-16 E7 protein through the application of the SELEX method. Once the nucleic acid sequence of a functional aptamer is determined, large amounts of the oligonucleotide can be produced and modified at low cost and high efficiency. The remarkable affinity and specificity of aptamers for their targets make these molecules the next-generation tool for diagnostics and therapeutics of cervical cancer.

HPV DNA, E6/E7 mRNA, and p16INK4a detection in head and neck cancers: a systematic review and meta-analysis.

BACKGROUND: We aimed to provide updated information about the global estimates of attributable fraction and type distribution of human papillomavirus (HPV) in head and neck squamous cell carcinomas by doing a systematic review and meta-analysis. METHODS: We did a literature search on PubMed to identify studies that used PCR for detection of HPV DNA in head and neck squamous cell carcinomas with information about HPV genotype distribution. We included studies that tested 20 or more biopsies per cancer site and were published between July 15, 1990, and Feb 29, 2012. We collected information about sex, risk factors, HPV detection methods, and biomarkers of potentially HPV-induced carcinogenesis (E6/E7 mRNA and p16(INK4a)). If it was not possible to abstract the required information directly from the paper, we contacted the authors. We did a meta-analysis to produce pooled prevalence estimates including a meta-regression to explore sources of heterogeneity. FINDINGS: 148 studies were included, contributing data for 12 163 cases of head and neck squamous cell carcinoma from 44 countries. HPV DNA was detected in 3837 cases. HPV16 accounted for 82·2% (95% CI 77·7-86·4) of all HPV DNA positive cases. By cancer site, pooled HPV DNA prevalence estimates were 45·8% (95% CI 38·9-52·9) for oropharynx, 22·1% (16·4-28·3) for larynx (including hypopharynx), and 24·2% (18·7-30·2) for oral cavity. The percent positivity of p16(INK4a) positive cases in HPV-positive oropharyngeal cancer cases was 86·7% (95% CI 79·2-92·9) and of E6/E7 mRNA positive cases was 86·9% (73·2-96·8). The estimate of HPV attributable fraction in oropharyngeal cancer defined by expression of positive cases of E6/E7 mRNA was 39·8% and of p16(INK4a) was 39·7%. Of subsites, tonsils (53·9%, 95% CI 46·4-61·3) had the highest HPV DNA prevalence. HPV DNA prevalence varied significantly by anatomical site, geographic region, but not by sex or tobacco or alcohol consumption. INTERPRETATION: The contribution of HPV prevalence in head and neck squamous cell carcinoma and in particular that of HPV16 in the oropharynx shows the potential benefit of prophylactic vaccines. FUNDING: European Commission.

Human papillomavirus infection in a male population attending a sexually transmitted infection service.

OBJECTIVE: Human Papillomavirus (HPV) infection in men may produce cancer and other major disorders. Men play an important role in the transmission of the virus and act as a reservoir. The aim of this study was to determine the HPV-genotypes and their prevalence in a group of men attending a Sexually Transmitted Infection service. PATIENTS AND SAMPLES: Between July 2002 and June 2011, 1392 balanopreputial, 435 urethral, 123 anal, and 67 condyloma lesions from 1551 men with a mean age of 35.8±11.3 years old (range: 17-87) were collected for HPV-DNA testing. METHODS: A fragment of the L1-gene and a fragment of the E6/E7-genes were amplified by PCR. Positive samples were typed by hybridization. RESULTS: The HPV genome was detected in 36.9% (486/1318) balanopreputial and in 24.9% (101/405) urethral (p<0.0001) swabs from 38.1% (538) of 1469 men. Co-infections were present in 5.4% (80/1469) of cases. HPV was found in 43.9% (373/850) of men younger than 35 vs. 31.7% (187/589) of men aged >35. HPV was found in 59.4% (104) of 165 men with lesions (macroscopic or positive peniscopy), and in 22.8% (61/267) without clinical alterations. HPV was also detected in 71.4% (40/56) men with condylomata and in 58.7% (64/109) of men with positive peniscopy. CONCLUSIONS: HPV prevalence in men was high and decreased with age. HPV was found more frequently in balanopreputial than in urethral swabs. There was a low rate of co-infections. Low-risk HPV vaccine genotypes were the most recurrent especially in younger. Although HPV has been associated with clinical alterations, it was also found in men without any clinical presentation. Inclusion of men in the national HPV vaccination program may reduce their burden of HPV-related disease and reduce transmission of the virus to non-vaccinated women.

[Prokaryotic expression and identification of HPV16 E7 protein].

HPV16 E7 fusion protein was expressed in E. coli BL21, and its applied value for HPV was evaluated. HPV16 E7 gene was amplified by PCR, and cloned into prokaryotic expression vector pGEX6p-1. The recombinant plasmid was transformed into E. coli BL21, and HPV16 E7 fusion was expressed through IPTG induction. The expressed product was analyzed by SDS-PAGE and Western blot, subsequently purified according to Glutathione Sepharose 4B purification procedure. An indirect ELISA with the purified fusion protein as the coating antigen was then established to detect E7 serum antibodies from mice immunized with recombinant Listeria monocytogenes delivering HPV16 E7. The results demonstrated that the soluble fusion protein was highly expressed at 25 degrees C after induction with 0.5 mM IPTG. Furthermore, the result of Western blot analysis showed that the fusion protein had good specific reaction with an anti-E7 monoclonal antibody. Indirect ELISA result confirmed that the fusion protein could detect the serum antibodies against E7 with a titer of 1:200. The expressed GST-E7 fusion protein was immunocompetent, which was useful in the research of E7 biological function and therapeutic vaccine.

Enrichment and detection of peptides from biological systems using designed periodic mesoporous organosilica microspheres.

Periodic mesoporous organosilica microspheres (PMOMs) are designed with integrated structural features, including a cubic mesostructure, hydrophobic wall composition, a uniform pore size of ≈3 nm, and a spherical morphology in micrometers, all advantageous for size-selective and highly efficient enrichment of peptides from mixtures. Consequently, PMOMs can be used to capture peptides in a range of complex biological systems.

Extraction, purification and characterization of the plant-produced HPV16 subunit vaccine candidate E7 GGG.

Several studies indicated that biopharmaceuticals based on the recombinant protein E7 of human papillomavirus (HPV) can serve as therapeutic vaccines preventing the development of cancer in women infected with high-risk types of HPV such as HPV16. Here, we report effective extraction and purification of a plant-produced E7GGG-lichenase fusion protein, an HPV16 subunit vaccine candidate, from Nicotiana benthamiana plants, to a high yield. The target contains the modified HPV16 E7 protein internally fused to the surface loop of a truncated, hexa-His- and KDEL-tagged variant of bacterial lichenase, and has been previously shown to possess anti-cancer activity in an animal model. We purified the protein using a combination of immobilized metal-ion affinity chromatography and gel filtration. The achieved purity of the final product was 99% as confirmed by Coomassie or SYPRO Ruby staining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by analytical size exclusion chromatography coupled with multi-angle laser light scattering. The overall yield was 50% corresponding to 0.1g of protein per 1 kg plant biomass. Only slight changes in these parameters were observed during the process scale-up from 50 g to 1 kg of processed leaf biomass.

Diagnostic and prognostic validity of the human papillomavirus E6/E7 mRNA test in cervical cytological samples of HC2-positive patients.

The study aimed to assess the clinical utility in identifying CIN2 or worse (CIN2+), of the Pretect HPV-Proofer test for E6/E7 mRNA detection in Hybrid Capture 2 (HC2)-positive patients, who underwent colposcopy. In particular, the study analyzed the mRNA test performance as the third test in a subgroup of HC2+ patients with less severe than high-grade squamous intraepithelial lesions (HSIL-). We analyzed 464 cervico-vaginal samples by liquid-based cytology (LBC) and PreTect HPV-Proofer. Moreover 231 patients also had a biopsy at baseline and 75, with HSIL-, were followed up within 2 years by LBC, colposcopy, and histology when indicated. The highest sensitivity for CIN2+ belonged to the mRNA compared to LBC, at the HSIL+ threshold (72% vs. 58%), whereas the LBC showed the highest specificity and positive predictive value (PPV) (99 and 93% vs. 73 and 39%, respectively). Focusing on the 408 HSIL- patients, the mRNA positivity was significantly more associated with CIN2+ than CIN2- lesions (p < 0.0001). Moreover, among the 75 HSIL- followed up patients, the mRNA displayed high longitudinal Specificity (89%), even if the sensitivity and the PPV were low (50 and 20%, respectively). The present data suggest that the mRNA test may have a diagnostic and a potentially prognostic role in HC2+/HSIL- patients.

Solution structure of the partially folded high-risk human papilloma virus 45 oncoprotein E7.

The oncoprotein E7 of human papilloma viruses (HPV) is involved in the pathogenesis and maintenance of human cervical cancers. The most prevalent HPV types found in cervix carcinomas are HPV16, 18 and 45. The structure of the E7 dimer from HPV45 (PDB 2F8B) was determined by nuclear magnetic resonance spectroscopy. Each monomer comprises an unfolded N-terminus and a well-structured C-terminal domain with a beta1beta2alpha1beta3alpha2 topology representing a unique zinc-binding fold found only for E7. Dimerization occurs through the alpha1/alpha1' helices and intermolecular beta-sheet formation but excludes the zinc-binding sites. E7 is reported to interact with a number of cellular proteins (e.g. pRb, p21(CIP1)). Binding of a peptide derived from the C-terminus of p21(CIP1) to the C-terminal domain of E7 was characterized by monitoring chemical shift perturbations of the amide groups of E7. This provides direct evidence that a shallow groove situated between alpha1 and beta1 of the E7 C-terminal domain is interacting with the C-terminus of p21(CIP1). Intriguingly, this binding site overlaps with the low-affinity binding site on E7 for the C-domain of pRb.