The two-stage interaction of Ebola virus VP40 with nucleoprotein results in a switch from viral RNA synthesis to virion assembly/budding

Ebola virus (EBOV) is an enveloped negative-sense RNA virus and a member of the filovirus family. Nucleoprotein (NP) expression alone leads to the formation of inclusion bodies (IBs), which are critical for viral RNA synthesis. The matrix protein, VP40, not only plays a critical role in virus assembly/budding, but also can regulate transcription and replication of the viral genome. However, the molecular mechanism by which VP40 regulates viral RNA synthesis and virion assembly/budding is unknown. Here, we show that within IBs the N-terminus of NP recruits VP40 and is required for VLP-containing NP release. Furthermore, we find four point mutations (L692A, P697A, P698A and W699A) within the C-terminal hydrophobic core of NP result in a stronger VP40-NP interaction within IBs, sequestering VP40 within IBs, reducing VP40-VLP egress, abolishing the incorporation of NC-like structures into VP40-VLP, and inhibiting viral RNA synthesis, suggesting that the interaction of N-terminus of NP with VP40 induces a conformational change in the C-terminus of NP. Consequently, the C-terminal hydrophobic core of NP is exposed and binds VP40, thereby inhibiting RNA synthesis and initiating virion assembly/budding.

Ebola virus – from neglected threat to global emergency state / Vírus ébola – de ameaça negligenciada ao estado de emergência global

SUMMARY Objective: This review aims to update knowledge about Ebola virus disease (EVD) and recent advances in its diagnosis, treatment and prevention. Method: A literature review was performed using the following databases: ISI Web of Knowledge, PubMed, IRIS, Scopus and the websites of the CDC and the WHO. Additionally, we have included articles and reports referenced in the basic literature search, and news that were considered relevant. Results: The Ebola virus, endemic in some parts of Africa, is responsible for a severe form of hemorrhagic fever in humans; bats are probably its natural reservoir. It is an extremely virulent virus and easily transmitted by bodily fluids. EVD's complex pathophysiology, characterized by immunosuppression as well as stimulation of an intense inflammatory response, results in a syndrome similar to septic shock. The diagnosis is difficult due to the initial symptoms that mimic other diseases. Despite the high mortality rates that can amount to 90%, a prophylaxis (chemical or vaccine) or effective treatment does not exist. Two vaccines and experimental therapies are being developed for the prevention and treatment of EVD. Conclusion: Although the virus is known for about 40 years, the lack of knowledge obtained and the disinterest of government authorities in the countries involved justify the state of emergency currently exists regarding this infectious agent. Only the coordination of multiple entities and the effective commitment of the international community will facilitate the control and effective prevention of EVD.

RESUMO Objetivo: esta revisão tem como objetivo atualizar os conhecimentos sobre a doença do vírus ébola (DVE) e sobre os recentes avanços nos métodos de diagnóstico, tratamento e prevenção. Método: foi realizada uma revisão de literatura, utilizando as seguintes bases de dados: ISI Web of Knowledge, PubMed, IRIS, Scopus e os sites do Centers for Disease Control and Prevention (CDC) e da Organização Mundial da Saúde (OMS). Adicionalmente, foram incluídos artigos e relatórios referenciados na pesquisa bibliográfica de base e notícias consideradas relevantes. Resultados: o vírus ébola, endêmico de algumas regiões da África, é responsável por uma forma grave de febre hemorrágica no homem, e os morcegos são provavelmente o seu reservatório natural. É um vírus extremamente virulento e de fácil transmissão pelos fluidos corporais. A complexa fisiopatologia da doença, caracterizada pela imunossupressão e pelo estímulo a uma intensa resposta inflamatória, resulta em uma síndrome semelhante ao choque séptico. O seu diagnóstico é difícil, por causa da sintomatologia inicial, que mimetiza outras doenças. Apesar das altas taxas de mortalidade, que podem alcançar os 90%, não existe profilaxia (química ou vacinal) ou tratamento eficaz. Encontram-se em desenvolvimento duas vacinas e terapias experimentais para a prevenção e o tratamento da DVE. Conclusão: apesar de ser um vírus conhecido há cerca de 40 anos, o escasso conhecimento obtido e o desinteresse das entidades governamentais de países envolvidos justificam o estado de emergência que se vive atualmente em relação a esse agente infeccioso. A coordenação por múltiplas entidades e o empenho efetivo da comunidade internacional facilitarão o seu controle e a prevenção eficaz.