Casos de dengue, zika e chikungunya até 15 de abril 2016 2017

Por que os casos de zika e dengue estão despencando no Brasil

“Vemos epidemias de dengue há cerca de 30 anos e ficamos refratários a ouvir falar sobre a doença. Com o zika, realmente saímos da zona de conforto, ficou clara a importância do controle doméstico do mosquito, e acredito que houve uma reação mais forte do poder público e da esfera privada” Denise Valle Instituto Oswaldo Cruz, em entrevista ao Nexo

Em julho de 2016, um estudo publicado na revista “Science” previu que a epidemia de zika na América Latina acabaria até o final de 2017. Isso não ocorreria devido a medidas de combate ao Aedes aegypti ou à descoberta de uma vacina, mas a um fenômeno cíclico bastante conhecido pela medicina: a “imunidade de rebanho”. Ele diz respeito à maneira como, quando indivíduos são infectados por um vírus e sobrevivem, seu corpo mantém defesas naturais contra ele. Conforme um grande número de pessoas de uma população é infectado e sobrevive, sobra uma proporção menor da população vulnerável a ele. Dessa forma, o processo de propagação da doença como um todo é prejudicado: apesar de continuar a haver pessoas vulneráveis, há uma chance maior de que um mosquito infectado pique alguém imune, o que diminui a velocidade de propagação de um vírus. Quem se torna imune serve de proteção para o resto das pessoas.

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UFG descobre novos compostos que podem ajudar a tratar pessoas com zika

A Universidade Federal de Goiás (UFG) descobriu novos compostos que podem ajudar no tratamento de pessoas com o vírus da zika. Ao todo, nove substâncias foram selecionadas para testes em células infectadas, que serão feitos em uma universidade dos Estados Unidos. O objetivo é desenvolver medicamentos para combater a doença.

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UFG descobre novos possíveis compostos contra o vírus Zika

Em maio de 2016, a Universidade Federal de Goiás (UFG), em parceria com a World Community Grid (WCG), da International Business Machines (IBM), iniciou o projeto OpenZika, que visa identificar substâncias com potencial para tratar pessoas infectadas pelo vírus Zika. De uma lista inicial de aproximadamente 7.600 compostos, dentre eles fármacos já aprovados para uso em humanos, cinco foram selecionados e estão em fases de testes in vitro na University of California San Diego  (UCSD). Agora, o grupo acaba de descobrir mais nove substâncias potenciais que serão testadas.

A descoberta surgiu em uma segunda leva de pesquisas com 260 compostos adicionais que foram testados por meio de uma triagem virtual, maior e mais diversa, contra as estruturas cristalinas da proteína helicase NS3 do vírus Zika, ligadas ao ácido ribonucleico (RNA). Os compostos também serão encaminhados para a universidade californiana ainda neste mês de março, na busca do desenvolvimento de um medicamento antiviral.

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Crystal structure of Zika virus NS5 RNA-dependent RNA polymerase

The current Zika virus (ZIKV) outbreak became a global health threat of complex epidemiology and devastating neurological impacts, therefore requiring urgent efforts towards the development of novel efficacious and safe antiviral drugs. Due to its central role in RNA viral replication, the non-structural protein 5 (NS5) RNA-dependent RNA-polymerase (RdRp) is a prime target for drug discovery. Here we describe the crystal structure of the recombinant ZIKV NS5 RdRp domain at 1.9 Å resolution as a platform for structure-based drug design strategy. The overall structure is similar to other flaviviral homologues. However, the priming loop target site, which is suitable for non-nucleoside polymerase inhibitor design, shows significant differences in comparison with the dengue virus structures, including a tighter pocket and a modified local charge distribution.

Figure 1

New high resolution structures of ZIKV NS5 RNA polymerase are available in Protein Data Bank (PDB ID:5TIT and 5U04).

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Molecular dynamics simulations of Zika virus NS3 helicase: Insights into RNA binding site activity

America is still suffering with the outbreak of Zika virus (ZIKV) infection. Congenital ZIKV syndrome has already caused a public health emergency of international concern. However, there are still no vaccines to prevent or drugs to treat the infection caused by ZIKV. The ZIKV NS3 helicase (NS3h) protein is a promising target for drug discovery due to its essential role in viral genome replication. NS3h unwinds the viral RNA to enable the replication of the viral genome by the NS5 protein. NS3h contains two important binding sites: the NTPase binding site and the RNA binding site. Here, we used molecular dynamics (MD) simulations to study the molecular behavior of ZIKV NS3h in the presence and absence of ssRNA and the potential implications for NS3h activity and inhibition. Although there is conformational variability and poor electron densities of the RNA binding loop in various apo flaviviruses NS3h crystallographic structures, the MD trajectories of NS3h-ssRNA demonstrated that the RNA binding loop becomes more stable when NS3h is occupied by RNA. Our results suggest that the presence of RNA generates important interactions with the RNA binding loop, and these interactions stabilize the loop sufficiently that it remains in a closed conformation. This closed conformation likely keeps the ssRNA bound to the protein for a sufficient duration to enable the unwinding/replication activities of NS3h to occur. In addition, conformational changes of this RNA binding loop can change the nature and location of the optimal ligand binding site, according to AutoLigand calculations. These are important findings to help guide the design and discovery of new inhibitors of NS3h as promising compounds to treat the ZIKV infection.

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The spectrum of neuropathological changes associated with congenital Zika virus infection

A major concern associated with ZIKV infection is the increased incidence of microcephaly with frequent calcifications in infants born from infected mothers. To date, postmortem analysis of the central nervous system (CNS) in congenital infection is limited to individual reports or small series. We report a comprehensive neuropathological study in ten newborn babies infected with ZIKV during pregnancy, including the spinal cords and dorsal root ganglia (DRG), and also muscle, pituitaries, eye, systemic organs, and placentas. Using in situ hybridization (ISH) and electron microscopy, we investigated the role of direct viral infection in the pathogenesis of the lesions. Nine women had Zika symptoms between the 4th and 18th and one in the 28th gestational week. Two babies were born at 32, one at 34 and 36 weeks each and six at term. The cephalic perimeter was reduced in four, and normal or enlarged in six patients, although the brain weights were lower than expected. All had arthrogryposis, except the patient infected at 28 weeks gestation. We defined three patterns of CNS lesions, with different patterns of destructive, calcification, hypoplasia, and migration disturbances. Ventriculomegaly was severe in the first pattern due to midbrain damage with aqueduct stenosis/distortion. The second pattern had small brains and mild/moderate (ex-vacuo) ventriculomegaly. The third pattern, a well-formed brain with mild calcification, coincided with late infection. The absence of descending fibres resulted in hypoplastic basis pontis, pyramids, and cortico-spinal tracts. Spinal motor cell loss explained the intrauterine akinesia, arthrogryposis, and neurogenic muscle atrophy. DRG, dorsal nerve roots, and columns were normal. Lympho-histiocytic inflammation was mild. ISH showed meningeal, germinal matrix, and neocortical infection, consistent with neural progenitors death leading to proliferation and migration disorders. A secondary ischemic process may explain the destructive lesions. In conclusion, we characterized the destructive and malformative consequences of ZIKV in the nervous system, as reflected in the topography and severity of lesions, anatomic localization of the virus, and timing of infection during gestation. Our findings indicate a developmental vulnerability of the immature CNS, and shed light on possible mechanisms of brain injury of this newly recognized public health threat.

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Zika Virus Infection and Solid Organ Transplantation: A New Challenge

Public health concerns exist surrounding the epidemic of the Zika virus (ZIKV) and the rapid growth of transplantation in developing countries, including endemic zones of active arbovirus transmission, as well as travel to such regions by potential organ donors and recipients. Few data exist regarding the clinical characteristics of ZIKV infection in immunocompromised hosts. Laboratory screening protocols for transplantation to differentiate ZIKV infections from other endemic viral diseases and for the detection of possible donor-derived infection have not been stated. The diagnosis of ZIKV infection remains a challenge, fueled by the lack of standardized commercially available diagnostic tests and validated reference diagnostic laboratories, as well as the limited duration of ZIKV viremia. In this small series, ZIKV infection in renal and liver recipients presented without rash, conjunctivitis, or neurological symptoms, and with abnormal graft function, thrombocytopenia, and bacterial superinfection. We report the first case series of ZIKV infection in solid organ recipients, with a description of clinical and laboratory features and therapeutic management.

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Zika virus causes testicular atrophy

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that has recently been found to cause fetal infection and neonatal abnormalities, including microcephaly and neurological dysfunction. ZIKV persists in the semen months after the acute viremic phase in humans. To further understand the consequences of ZIKV persistence in males, we infected Ifnar1−/− mice via subcutaneous injection of a pathogenic but nonlethal ZIKV strain. ZIKV replication persists within the testes even after clearance from the blood, with interstitial, testosterone-producing Leydig cells supporting virus replication. We found high levels of viral RNA and antigen within the epididymal lumen, where sperm is stored, and within surrounding epithelial cells. Unexpectedly, at 21 days post-infection, the testes of the ZIKV-infected mice were significantly smaller compared to those of mock-infected mice, indicating progressive testicular atrophy. ZIKV infection caused a reduction in serum testosterone, suggesting that male fertility can be affected. Our findings have important implications for nonvector-borne vertical transmission, as well as long-term potential reproductive deficiencies, in ZIKV-infected males.

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