Human papillomavirus vaccines in plants

Human papillomaviruses are the etiological agents of cervical cancer, one of the two most prevalent cancers in women in developing countries. Currently available prophylactic vaccines are based on the L1 major capsid protein, which forms virus-like particles when expressed in yeast and insect cell lines. Despite their recognized efficacy, there are significant shortcomings: the vaccines are expensive, include only two oncogenic virus types, are delivered via intramuscular injection and require a cold chain. Plant expression systems may provide ways of overcoming some of these problems, in particular the expense. In this article, we report recent promising advances in the production of prophylactic and therapeutic vaccines against human papillomavirus by expression of the relevant antigens in plants, and discuss future prospects for the use of such vaccines. © 2010 Expert Reviews Ltd.

Plant-produced cottontail rabbit papillomavirus L1 protein protects against tumor challenge : A proof-of-concept study

The native cottontail rabbit papillomavirus (CRPV) L1 capsid protein gene was expressed transgenically via Agrobacterium tumefaciens transformation and transiently via a tobacco mosaic virus (TMV) vector in Nicotiana spp. L1 protein was detected in concentrated plant extracts at concentrations up to 1.0 mg/kg in transgenic plants and up to 0.4 mg/kg in TMV-infected plants. The protein did not detectably assemble into viruslike particles; however, immunoelectron microscopy showed presumptive pentamer aggregates, and extracted protein reacted with conformation-specific and neutralizing monoclonal antibodies. Rabbits were injected with concentrated protein extract with Freund's incomplete adjuvant. All sera reacted with baculovirus-produced CRPV L1; however, they did not detectably neutralize infectivity in an in vitro assay. Vaccinated rabbits were, however, protected against wart development on subsequent challenge with live virus. This is the first evidence that a plant-derived papillomavirus vaccine is protective in an animal model and is a proof of concept for human papillomavirus vaccines produced in plants. Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Strategies for the prevention of cervical cancer by human papillomavirus vaccination

As cervical cancer is causally associated with 14 high-risk types of human papillomavirus (HPV), a successful HPV vaccine will have a major impact on this disease. Although some persistent HPV infections progress to cervical cancer, host immunity is generally able to clear most HPV infections. Both cell-mediated and antibody responses have been implicated in influencing the susceptibility, persistence or clearance of genital HPV infection. There have been two clinical trials that show that vaccines based on virus-like particles (VLPs) made from the major capsid protein, L1, are able to type specifically protect against cervical intra-epithelial neoplasia and infection. However, there is no evidence that even a mixed VLP vaccine will protect against types not included in the vaccine, and a major challenge that remains is how to engineer protection across a broader spectrum of viruses. Strategies for production of HPV vaccines using different vaccine vectors and different production systems are also reviewed. © 2005 Elsevier Ltd. All rights reserved.

Knowledge and attitudes of Spanish adolescent girls towards human papillomavirus infection: where to intervene to improve vaccination coverage

Background: HPV vaccine coverage is far from ideal in Valencia, Spain, and this could be partially related to the low knowledge about the disease and the vaccine, therefore we assessed these, as well as the attitude towards vaccination in adolescent girls, and tried to identify independently associated factors that could potentially be modified by an intervention in order to increase vaccine coverage. Methods: A cross sectional study was conducted in a random selection of schools of the Spanish region of Valencia. We asked mothers of 1278 girls, who should have been vaccinated in the 2011 campaign, for informed consent. Those that accepted their daughters’ participation, a questionnaire regarding the Knowledge of HPV infection and vaccine was passed to the girls in the school. Results: 833 mothers (65.1%) accepted participation. All their daughters’ responded the questionnaire. Of those, 89.9% had heard about HPV and they associated it to cervical cancer. Only 14% related it to other problems like genital warts. The knowledge score of the girls who had heard about HPV was 6.1/10. Knowledge was unrelated to the number of contacts with the health system (Pediatrician or nurse), and positively correlated with the discussions with classmates about the vaccine. Adolescents Spanish in origin or with an older sister vaccinated, had higher punctuation. 67% of the girls thought that the vaccine prevented cancer, and 22.6% felt that although prevented cancer the vaccine had important safety problems. 6.4% of the girls rejected the vaccine for safety problems or for not considering themselves at risk of infection. 71.5% of the girls had received at least one vaccine dose. Vaccinated girls scored higher knowledge (p = 0.05). Conclusion: Knowledge about HPV infection and vaccine was fair in adolescents of Valencia, and is independent to the number of contacts with the health system, it is however correlated to the conversations about the vaccine with their peers and the vaccination status. An action to improve HPV knowledge through health providers might increase vaccine coverage in the adolescents.

Vacunas profilácticas frente al VPH

Actualmente sólo existen dos vacunas disponibles para la prevención primaria frente al virus del papiloma humano, Gardasil® y Cervarix®. Ambas vacunas ofrecen una alta protección contra los genotipos 16 y 18 del papillomavirus, que son los responsables de más del 70% de los cánceres de cérvix, segunda causa de mortalidad por cáncer a nivel mundial en mujeres. Además, Gardasil®, ofrece una protección del 99% para las mujeres y del 89,4% para los hombre, frente a los genotipos 6 y 11 del virus, responsables del 90% de las verrugas genitales. Uno de los principales obstáculos para su uso generalizado es su elevado coste, por ello, los ensayos clínicos se dirigen a conseguir una inmunogenicidad eficaz con el menor número de dosis. Cervarix® se comercializa en Europa con una pauta de dos dosis en niñas de 9 a 14 años, con una inmunogenicidad de 48 meses. Gardasil® ha sido autorizada para su comercialización para una pauta de dos dosis en niñas/os de 9 a 13 años, con una imunogenicidad de 36 meses. Ambas vacunas han despertado una gran controversia en los últimos tiempos, por este motivo se están realizando continuos estudios de control que, hasta la fecha, avalan su seguridad. La falta de información sobre las vacunas, los escasos programas de sensibilización y las dudas sobre su seguridad han dificultado su aceptación. El papel de la enfermera es clave en este aspecto para fomentar la vacunación, a través de actividades dirigidas hacía la promoción y prevención frente al virus del papiloma humano.

Impact of coverage-dependent marginal costs on optimal HPV vaccination strategies.

The effectiveness of vaccinating males against the human papillomavirus (HPV) remains a controversial subject. Many existing studies conclude that increasing female coverage is more effective than diverting resources into male vaccination. Recently, several empirical studies on HPV immunization have been published, providing evidence of the fact that marginal vaccination costs increase with coverage. In this study, we use a stochastic agent-based modeling framework to revisit the male vaccination debate in light of these new findings. Within this framework, we assess the impact of coverage-dependent marginal costs of vaccine distribution on optimal immunization strategies against HPV. Focusing on the two scenarios of ongoing and new vaccination programs, we analyze different resource allocation policies and their effects on overall disease burden. Our results suggest that if the costs associated with vaccinating males are relatively close to those associated with vaccinating females, then coverage-dependent, increasing marginal costs may favor vaccination strategies that entail immunization of both genders. In particular, this study emphasizes the necessity for further empirical research on the nature of coverage-dependent vaccination costs.

Conhecimento sobre HPV (Papilomavírus Humano) e a percepção das adolescentes sobre sua imunização

Pós-graduação em Enfermagem (mestrado profissional) - FMB

Características de los vídeos en español publicados en Youtube sobre la vacuna contra el virus del papiloma humano

Fundamentos: Internet constituye un recurso de búsqueda de información relacionada con la salud. El objetivo de este trabajo fue conocer las características de los vídeos en idioma español de YouTube relacionados con la vacuna contra el virus del papiloma humano (VPH). Métodos: Se realizó un estudio observacional a partir de una búsqueda en YouTube el 26 de julio de 2013, con las palabras claves: “vacuna virus papiloma humano”, “vacuna VPH”, “vacuna Gardasil”, “vacuna Cervarix”. Se establecieron categorías por tipo, fuente de publicación y predisposición favorable o no hacia la vacuna. Se registró el número de visitas, tiempo de duración de los videos y origen de los 20 vídeos más visitados. Resultados. Se encontraron 1.080 videos registrados, 170 fueron seleccionados y clasificados como: noticias locales (n=39; 37 favorables, 2 desfavorables; 2:06:29; 42972 visitas), noticias nacionales (n=32; 30/2; 1:49:27; 50138 visitas), creados por subscritores de YouTube (n=21; 13/8; 2:50:35; 144655 visitas), entrevistas (n=21; 20/1; 1:44:39; 10991 visitas), anuncios (n=21; 19/2; 0:27:05; 28435 visitas), conferencias (n=17; 15/2; 3:25:39; 27206 visitas), documentales (n=16; 12/4; 2:11:31; 30629 visitas), y noticias internacionales (n=3; 3/0; 0:11:33; 1667 visitas). De los 20 videos más reproducidos predominan los favorables a la vacunación (n=12; 0:43:43; 161.789 visitas) frente a los desfavorables (n=8; 2:44:14; 86.583 visitas). Conclusiones. Predominan los videos que tiene una opinión favorable hacia la vacuna contra el VPH, aunque los videos de contenido negativo son los más extensos y reproducidos.

Aceptabilidad de la vacuna contra el virus del papiloma humano en madres de la provincia de Valencia (España)

Introducción: La Comunidad Valenciana inició en octubre del 2008 el programa de vacunación contra el virus del papiloma humano (VPH) en niñas de 14 años. El objetivo de este estudio es evaluar los conocimientos sobre la infección por VPH y su vacuna en madres de adolescentes e identificar los factores asociados a la predisposición de vacunar a sus hijas. Material y métodos: Estudio observacional transversal mediante cuestionario dirigido a madres de alumnas nacidas en 1995 matriculadas en centros de secundaria de la provincia de Valencia durante 2010-2011. Muestra aleatoria estratificada por conglomerados (n = 1.279). Análisis estadístico: porcentajes, intervalos de confianza, OR, contrastes chi al cuadrado y regresión logística multivariante. Resultados: Ochocientos treinta y tres cuestionarios completados (65,1%). El 76,6% de las madres habían vacunado a sus hijas contra el VPH. El 93,8% conocía la vacuna, sobre todo a través de la televisión (71,5%). El 78,5% recibió consejo favorable de un profesional sanitario, lo que mejoró la vacunación de sus hijas (OR: 2,4). Los conocimientos globales sobre la infección por VPH y la vacuna fueron bajos. La confianza de las madres en las vacunas como método preventivo mejora la vacunación contra VPH (OR: 3,8). El miedo a los efectos adversos (45,6%) fue el primer motivo de rechazo. Conclusiones: No parece que los medios de comunicación influyan en la decisión de vacunar. Sería conveniente minimizar la percepción de riesgo ante esta vacuna. El consejo del profesional sanitario actúa a favor de la vacunación si este interviene activamente en sentido positivo. Existe una brecha entre nivel de conocimientos y toma de decisión para vacunar.

Recombinant Kunjin virus replicon vaccines induce protective T-cell immunity against human papillomavirus 16 E7-expressing tumour

The persistence of the E7 oncoprotein in transformed cells in human papillomavirus (HPV)-associated cervical cancer provides a tumour-specific antigen to which immunotherapeutic strategies may be directed. Self-replicating RNA (replicon) vaccine vectors derived from the flavivirus Kunjin (KUN) have recently been reported to induce T-cell immunity. Here, we report that inclusion of a CTL epitope of HPV16 E7 protein into a polyepitope encoded by a KUN vector induced E7-directed T-cell responses and protected mice against challenge with an E7-expressing epithelial tumour. We found replicon RNA packaged into virus-like particles to be more effective than naked replicon RNA or plasmid DNA constructed to allow replicon RNA transcription in vivo. Protective immunity was induced although the E7 CTL epitope was subdominant in the context of other CTL epitopes in the polyepitope. The results demonstrate the efficacy of the KUN replicon vector system for inducing protective immunity directed towards a virally encoded human tumour-specific antigen, and for inducing multi-epitopic CTL responses. (C) 2004 Elsevier Inc. All rights reserved.

Optimization of human papillomavirus type 16 (HPV-16) L1 expression in plants: Comparison of the suitability of different HPV-16 L1 gene variants and different cell-compartment localization

Virus-like particle-based vaccines for high-risk human papillomaviruses (HPVs) appear to have great promise; however, cell culture-derived vaccines will probably be very expensive. The optimization of expression of different codon-optimized versions of the HPV-16 L1 capsid protein gene in plants has been explored by means of transient expression from a novel suite of Agrobacterium tumefaciens binary expression vectors, which allow targeting of recombinant protein to the cytoplasm, endoplasmic reticulum (ER) or chloroplasts. A gene resynthesized to reflect human codon usage expresses better than the native gene, which expresses better than a plant-optimized gene. Moreover, chloroplast localization allows significantly higher levels of accumulation of L1 protein than does cytoplasmic localization, whilst ER retention was least successful. High levels of L1 (>17% total soluble protein) could be produced via transient expression: the protein assembled into higher-order structures visible by electron microscopy, and a concentrated extract was highly immunogenic in mice after subcutaneous injection and elicited high-titre neutralizing antibodies. Transgenic tobacco plants expressing a human codon-optimized gene linked to a chloroplast-targeting signal expressed L1 at levels up to 11% of the total soluble protein. These are the highest levels of HPV L1 expression reported for plants: these results, and the excellent immunogenicity of the product, significantly improve the prospects of making a conventional HPV vaccine by this means. © 2007 SGM.

A deletion and point mutation study of the human papillomavirus type 16 major capsid gene

Recombinant human papillomavirus (HPV) virus-like particles (VLPs) made from the major capsid protein L1 are promising vaccine candidates for use as vaccines against genital and other HPV infections, and particularly against HPV-16. However, HPV-16 genotype variants have different binding affinities for neutralising mouse Mabs raised against HPV-16 L1 VLPs. This paper analyses, using a panel of well-characterised Mabs, the effects on the antigenicity of various C- and N-terminal deletants of HPV-16 L1 made in insect cells via recombinant baculovirus, of an A → T mutation at residue 266 (A266T), and of a C → G mutation at conserved position 428 (C428G). The effects of these changes on assembly of the variant L1s were studied by electron microscopy. Binding of Mab H16:E70 to A266T was reduced by almost half in comparison to wild type L1. Retention of the C-terminal region 428-483 was critical for the binding of conformation-specific Mabs (H16:V5, H16:E70, H16:U4 and H16:9A) whereas deletion of the nuclear localisation signal (NLS) or the C428G mutation or an N-terminal deletion (residues 2-9) did not affect the antigenicity. The N-terminal deletion resulted in a mixed population of 30 and 55 nm VLPs, which differs from the same construct expressed in Escherichia coli, whereas pentamer aggregates resulted from deletion of the 428-465 region or the C428G mutation. The results have implications both for considering use of single-genotype HPV vaccines, and for design of novel second-generation vaccines. © 2006 Elsevier B.V. All rights reserved.