Human papillomavirus (HPV) 16 E6 oncoprotein targets the Toll-like receptor pathway.

Cervical cancer is one of the leading causes of death in women worldwide and is etiologically linked to human papillomavirus (HPV) infection. Viral early proteins E6 and E7 manipulate cellular functions to promote the virus life cycle and are essential to the cellular transformation process. The innate immune system plays a pivotal role in the natural history of HPV infection. Among the various proteins that mediate the innate immune response, Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) and initiate the immune response. The objective of this study was to identify HPV E6 protein interaction partners in the TLR signalling pathway that may play a role in the immune response against HPV. Six TLR pathway proteins were shown to interact with HPV16 E6: myeloid differentiation primary response protein (MyD88), TIR domain-containing adapter molecule 1 (TRIF), interleukin-1 receptor-associated kinase-like (IRAK) 2, TNF receptor-associated factor (TRAF) 6, I-κB kinase beta (IKKß) and I-κB kinase epsilon (IKKε). The interaction site of IKKε with E6 is located in the region containing the enzyme catalytic site, suggesting an influence of E6 on the activation of IKKε target proteins. HPV16 E6 potentiated the activation of NF-κB by various TLR pathway members. These results suggest that HPV16 has the ability to interfere with components of the immune response, contributing to HPV carcinogenesis.

Vias de transdução de sinal e polimorfismo de Toll-like Receptors na carcinogenese por HPV / Toll-like Receptors signaling pathway and polymorphism on the HPV carcinogenesis

Seres humanos dependem incessantemente de um sistema de reconhecimento efetivo contra infecções para sobreviver. Dentre as diversas proteínas que compõem a resposta imune inata estão os receptores do tipo Toll (TLR Toll-like Receptors), que possuem a função de reconhecer padrões moleculares associados a patógenos e dar início a uma resposta imune adequada. O carcinoma do colo uterino é uma das principais causas de morte de mulheres por câncer mundialmente, sendo o terceiro tipo de câncer mais comum entre mulheres. Este tipo de neoplasia é vinculada etiologicamente à infecção pelo Papilomavírus humano (HPV). Dentre as principais proteínas virais, E6 e E7 são responsáveis pela manipulação dos processos celulares para promover ciclo viral, sendo essenciais no processo de transformação celular. Nesse contexto, o objetivo deste trabalho foi investigar a importância da via de sinalização de TLRs sobre a infecção por HPV. O polimorfismo rs5743836, na região promotora de TLR9, capaz de alterar a expressão deste receptor, foi estudado quanto à influência sobre a história natural da infecção por HPV em uma coorte de mulheres brasileiras; nenhuma associação relevante foi encontrada, indicando que este polimorfismo não interfere significativamente na resposta à infecção e risco de desenvolvimento de lesões no colo do útero causadas por HPV. Proteínas componentes da via de TLRs demonstraram serem alvos de interação com E6 de HPV16; dentre elas, o notável adaptador MyD88 e IKKε, enzima ativadora de importantes transfatores do sistema imune. Estas interações foram aqui estudadas. A interação de E6 com MyD88 resultou em estabilização da proteína viral, o que parece não depender do sítio LxxLL presente em MyD88, como ocorre com outros parceiros moleculares de E6. O sítio de interação de E6 com IKKε coincide com a região onde se localiza o sítio catalítico desta enzima, sugerindo a ação de E6 na ativação de proteínas alvo de IKKε. Esta interação foi observada em queratinócitos, células alvo das infecções por HPV. A produção de citocinas foi afetada por E6 de HPV16, resultando num aumento da quantidade de IL-8 e IL-6; a indução desta citocina poderia ser explicada pela ativação de IKKε. Estes resultados apontam para a capacidade do HPV16 de interferir com o sistema imune, contribuindo para o processo de carcinogênese

Humans constantly rely on an effective recognition system against infections in order to survive. Among various proteins that compose the innate immune response, Toll-like Receptors (TLRs) have the role to recognize pathogen associated molecular patterns and initiate a proper immune response. The cervical cancer is one of the main causes of women death worldwide, being the third most common cancer type among women. This type of neoplasia is etiologically associated with the Human papillomavirus (HPV) infection. E6 and E7, two main viral proteins, are responsible for manipulating the cellular processes to promote the virus' life-cycle, being essential to the cellular transformation process. In the context, the objective of this work was to investigate the relevance of the TLR signaling pathway on the HPV infection. The rs5743836 polymorphism, in the TLR9 promoter region, capable of altering this receptor's expression, was studied regarding its influence on the natural history of HPV infection in a Brazilian women cohort; no relevant association was found, indicating that this polymorphism does not interfere significantly in the infection response and risk of developing cervix lesions caused by HPV. Component proteins of TLR pathway were shown to be interaction targets of HPV16 E6; among them, the notable adaptor MyD88 and IKKε, enzyme that activates important immune system transfactors. These interactions were studied in this work. The interaction of E6 with MyD88 resulted in the stabilization of the viral protein, which seems independent of the LxxLL site present on MyD88, as in other E6 molecular partners. The interaction site on IKK with E6 matches with the region containing the enzyme's catalytic site, suggesting an influence of E6 in the activation of IKKε target proteins. This interaction was observed in keratinocytes, natural targets of HPV infections. The cytokines production was altered by HPV16 E6, resulting in an increase of IL-8 and IL-6 concentration; the induction of the latter could be explained by the activation of IKKε. These results point to the ability of HPV16 of interfering with the immune system, contributing to the carcinogenesis process

Polymorphism in the promoter region of the Toll-like receptor 9 gene and cervical human papillomavirus infection.

Polymorphism in the Toll-like receptor (TLR) 9 gene has been shown to have a significant role in some diseases; however, little is known about its possible role in the natural history of human papillomavirus (HPV) infections. We investigated the association between a single-nucleotide polymorphism (SNP) (rs5743836) in the promoter region of TLR9 (T1237C) and type-specific HPV infections. Specimens were derived from a cohort of 2462 women enrolled in the Ludwig-McGill Cohort Study. We randomly selected 500 women who had a cervical HPV infection detected at least once during the study as cases. We defined two control groups: (i) a random sample of 300 women who always tested HPV negative, and (ii) a sample of 234 women who were always HPV negative but had a minimum of ten visits during the study. TLR9 genotyping was performed using bidirectional PCR amplification of specific alleles. Irrespective of group, the WT homozygous TLR9 genotype (TT) was the most common form, followed by the heterozygous (TC) and the mutant homozygous (CC) forms. There were no consistent associations between polymorphism and infection risk, either overall or by type or species. Likewise, there were no consistently significant associations between polymorphism and HPV clearance or persistence. We concluded that this polymorphism in the promoter region of TLR9 gene does not seem to have a mediating role in the natural history of the HPV infection.