No description available.

A Dissertation submitted to the Faculty of Medicine, University of the witvmtersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science in Medicine. / The potential of Aedes aegypti to act as a vector of dengue (DEN) viruses was assessed in the tropical and subtropical regions of South Africa. The prevalence in bamboo pot ovitraps, utilization of artificial larval habitats and antihropophflism of Ae. aegypti was measured in fifteen populations from coastal Natal and five from the Transvaal. Pot indices generally ranged from 40-100 per cent (x±s;c= 60,3±9,8), with a mean abundance index of 0,43±0,15 (sx) mosquitoes/pot/day. Artificial container indices ranged from 11-83 per cent (X±si = 56,8±5,6). Biting rates ranged from 0,2-29,0 per manhour, in direct relationship to the level of urbanization. The feral Nduntupopulation was least anthropophilic, although pot and abundance indices were high. To investigate the presence of subspp. aegypti and formosus, the pale scales on tergite-1 were counted in ten or more siblings from each of 196 families, representing eighteen populations. At least 118 of these families were heterogeneous, each containing some siblings with no pale scales and others with pale scales on tergite-1, thus invalidating this character for distinguishing between the subspp. Isozyme electrophoresis 'did not provide diagnostic electromorphs for distingllishing between different populations. Allelomorph frequencies and the numberof pale scales on tergite-l and tergite-2 differed significantly in individual populations but not between anthropophilic and non-anthropophilic populations. As there was no correlation between tergal morphology, isozymes and anthropophilism, the populations could not be resolved into the two subspp. Based on the only morphological character that appears to be reliable, viz. the blackness of the background scales, all of the populations are probably Ae. aegypti formosus. The vector competence of five populations for DEN-1 and DEN-2 viruses was tested in the laboratory after allowing mosquitoes to feed on an infective blood-virus mixture. Viral antigen was detected by indirect fluorescent antibody test. Head-squash infection rates (HSIRs)ranged from 11-54 per cent for DEN-land from 19- 46 per cent for DEN...2. Transmission rates (TRs) were determined by in vitro capillary method and ranged from 67-100 per cent for DEN-1 and from 11-86 pier cent for DEN-2.Meanvector competence indices (calculated from HSIRsand TRS) ware 0,13-0,41 for DEN-l and 0,,18-0,34 for DEN-2.It is concluded that, should DEN be reintroduced to South Africa via the shipping or tourist industries, Ae. aegypti would be an efficient urban vector. The Durban population is of particular epidemiological importance because it was highly anthropophilic and was the most vectorially competent of the South African populations. / Andrew Chakane 2018

Thesis (Ph.D. (Microbiology))--Mahidol University, 1973.

Thesis (M.Sc. (Tropical Medicine))--Mahidol University, 2003.

Thesis (M.Sc. in Microbiology) -- Mahidol University, 1976.

Orientador: Jayme Augusto de Souza Neto / Resumo: Dengue é a arbovirose de maior crescimento nos últimos anos, repercutindo em impactos sociais e econômicos devido às altas taxas de morbidade e mortalidade desencadeadas pela infecção. O vírus dengue tem como principal vetor o mosquito Aedes aegypti. Por apresentar hábito hematofágico, antropofílico, de rápido desenvolvimento, é um excelente transmissor do vírus. Medidas de controle estão restritas à eliminação do mosquito vetor, uma vez que um tratamento específico ou uma vacina não estão disponíveis à população. E uma característica que determina a disseminação de doenças é a alta competência vetorial de seus mosquitos vetores, a qual tem sido associada à fatores genéticos do mosquito e ambientais. Sabe-se que a variabilidade genética dos mosquitos é um dos fatores que pode determinar o sucesso da relação mosquito-patógeno específico. Com isso, no presente trabalho foram estudadas as competências vetoriais de mosquitos Aedes aegypti da cidade de Botucatu infectados com DENV-2 e DENV-4 a fim de entender melhor a competência vetorial desses mosquitos. Além disso, foram feitas tentativas para selecionar linhagens resistentes e susceptíveis desses mosquitos infectados com ambos os sorotipos. Os mosquitos infectados com DENV-2 foram genotipados pela metodologia de SNP chip e posteriormente foram realizadas análises de estudo global do genoma (GWAS) afim de encontrar fatores genéticos relacionados com os diferentes fenótipos susceptív... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Dengue is the arboviruses with the greatest growth in recent years, with social and economic impacts due to the high morbidity and mortality rates triggered by the infection. Dengue has as main vector the mosquito Aedes aegypti. Because of the haematophagic habit, been antropophilic, fast development, Aedes aegypti mosquitoes are excellent transmitter of the dengue virus. Control measures are restricted to vector mosquito elimination since a specific treatment or vaccine is not available to the population. The characteristic that determinates the diseases dissemination is the high vector competence of the mosquitoes, which has been associated with mosquito genetic and environmental factors. It is known that the genetic variability of mosquitoes is one of the factors that can determine the success of the specific mosquito-pathogen relationship. In the present study, the vector competence of Aedes aegypti mosquitoes from Botucatu city infected with DENV-2 and DENV-4 were compared in order to understand the vector competence of these specific mosquitoes. In addition, we tried to do resistant and susceptible strains selections of these mosquitoes infected with both serotypes. And mosquitoes infected with DENV-2 were genotyped by the SNP chip methodology and later analyzes were carried out to study the genome (GWAS) in order to find genetic factors related to the different susceptible and resistant phenotypes of them. As results we observed different vector competence of the same ... (Complete abstract click electronic access below) / Doutor

Submitted by Letícia Tiemi Egami Oda (leticia.e.o@gmail.com) on 2018-11-19T14:17:39Z No. of bitstreams: 1 Tese DR LTEO-corrigida final.pdf: 2530249 bytes, checksum: 4783af91c3819b7b7b372559ab20f01a (MD5) / Approved for entry into archive by ROSANGELA APARECIDA LOBO null (rosangelalobo@btu.unesp.br) on 2018-11-21T10:42:03Z (GMT) No. of bitstreams: 1 oda_lte_dr_bot.pdf: 2530249 bytes, checksum: 4783af91c3819b7b7b372559ab20f01a (MD5) / Made available in DSpace on 2018-11-21T10:42:03Z (GMT). No. of bitstreams: 1 oda_lte_dr_bot.pdf: 2530249 bytes, checksum: 4783af91c3819b7b7b372559ab20f01a (MD5) Previous issue date: 2018-05-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Dengue é a arbovirose de maior crescimento nos últimos anos, repercutindo em impactos sociais e econômicos devido às altas taxas de morbidade e mortalidade desencadeadas pela infecção. O vírus dengue tem como principal vetor o mosquito Aedes aegypti. Por apresentar hábito hematofágico, antropofílico, de rápido desenvolvimento, é um excelente transmissor do vírus. Medidas de controle estão restritas à eliminação do mosquito vetor, uma vez que um tratamento específico ou uma vacina não estão disponíveis à população. E uma característica que determina a disseminação de doenças é a alta competência vetorial de seus mosquitos vetores, a qual tem sido associada à fatores genéticos do mosquito e ambientais. Sabe-se que a variabilidade genética dos mosquitos é um dos fatores que pode determinar o sucesso da relação mosquito-patógeno específico. Com isso, no presente trabalho foram estudadas as competências vetoriais de mosquitos Aedes aegypti da cidade de Botucatu infectados com DENV-2 e DENV-4 a fim de entender melhor a competência vetorial desses mosquitos. Além disso, foram feitas tentativas para selecionar linhagens resistentes e susceptíveis desses mosquitos infectados com ambos os sorotipos. Os mosquitos infectados com DENV-2 foram genotipados pela metodologia de SNP chip e posteriormente foram realizadas análises de estudo global do genoma (GWAS) afim de encontrar fatores genéticos relacionados com os diferentes fenótipos susceptível e resistente dos mosquitos. Como resultados observou-se diferentes competências vetoriais dos mesmos mosquitos infectados com diferentes sorotipos. Os mosquitos infectados com DENV-2 foram aproximadamente 70% susceptíveis, e mosquitos infectados com DENV-4 aproximadamente 70% foram resistentes, possuindo assim competências vetoriais opostas. Já no estudo da seleção dos fenótipos foi possível uma seleção de 80% até a geração F3 de mosquitos infectados com DENV-2, apesar do número baixo de indivíduos nas seleções. Os mosquitos infectados com DENV-4 não obtiveram uma taxa de seleção muito elevada, visto que as seleções foram feitas só até a geração F-2. Os resultados das análises de GWAS mostraram possíveis associações dos SNPs com os fenótipos estudados, apesar de não serem estatisticamente significantes para a correção de Bonferroni. Com isso, concluímos que a diferença vetorial é bastante dependente do sorotipo viral; para as análises de seleção e formação de linhagem é necessário um maior número de indivíduos nas primeiras infecções; e no estudo GWAS apesar da associação não ter sido significativa, devido ao baixo número de indivíduos, e dos parâmetros de correção estatística não serem ideais para indivíduos de uma única população, acredita-se que as associação encontradas de alguns SNPs com os fenótipos estudados sejam verdadeiras. / Dengue is the arboviruses with the greatest growth in recent years, with social and economic impacts due to the high morbidity and mortality rates triggered by the infection. Dengue has as main vector the mosquito Aedes aegypti. Because of the haematophagic habit, been antropophilic, fast development, Aedes aegypti mosquitoes are excellent transmitter of the dengue virus. Control measures are restricted to vector mosquito elimination since a specific treatment or vaccine is not available to the population. The characteristic that determinates the diseases dissemination is the high vector competence of the mosquitoes, which has been associated with mosquito genetic and environmental factors. It is known that the genetic variability of mosquitoes is one of the factors that can determine the success of the specific mosquito-pathogen relationship. In the present study, the vector competence of Aedes aegypti mosquitoes from Botucatu city infected with DENV-2 and DENV-4 were compared in order to understand the vector competence of these specific mosquitoes. In addition, we tried to do resistant and susceptible strains selections of these mosquitoes infected with both serotypes. And mosquitoes infected with DENV-2 were genotyped by the SNP chip methodology and later analyzes were carried out to study the genome (GWAS) in order to find genetic factors related to the different susceptible and resistant phenotypes of them. As results we observed different vector competence of the same mosquitoes infected with different serotypes. Mosquitoes infected with DENV-2 were approximately 70% susceptible, and mosquitoes infected with DENV-4 were approximately 70% resistant, thus the opposing vector competence. In the selection study it was possible to select 80% up to the F3 generation of mosquitoes infected with DENV-2, despite the low number of individuals in the selections. Mosquitoes infected with DENV-4 did not obtain a very high selection rate, since the selections were made only up to the F-2 generation. The results of the GWAS analysis showed possible associations of the SNPs with the studied phenotypes, although they were not statistically significant for the Bonferroni correction. With this, we conclude that the vector competence difference is quite dependent on the viral serotype; for the analysis of selection and formation of lineage is necessary a greater number of individuals in the first infections; and in the GWAS study, although the association was not significant because of the low number of individuals, and the statistical correction parameters are not ideal for individuals from the same population, it is believed that the association of some SNPs with the studied phenotypes is true.

Lic.-avh. (sammanfattning) Stockholm : Karolinska institutet, 2008.

Dengue é uma doença viral que atinge vários países, infectando milhares de pessoas anualmente. Sua transmissão ocorre pelo repasto sanguíneo feito pelas fêmeas dos mosquitos Aedes sp. infectadas e seus sintomas tem um amplo espectro de variação, que vão desde quadros assintomáticos até quadros graves com hipovolemia, podendo levar a óbito. A necessidade de adaptação do vírus a sistemas tão distintos (inseto e mamífero) restringe o espectro de variabilidade que o mesmo pode adquirir, permitindo que o vírus se adapte a ambos os hospedeiros com eficiência replicativa semelhante. Estudos com outros flavivírus já mostraram que a aquisição de variabilidade ocorre de maneiras distintas no hospedeiro mamífero e no inseto vetor, permitindo ao vírus máxima adaptação nas células infectadas. Levando em consideração estes estudos, este trabalho investigou a adaptação de duas cepas do vírus da dengue, a ACS-46, não neurovirulenta para camundongos adultos e a cepa JHA, neurovirulenta para camundongos adultos. O estudo foi feito utilizando cultura de células de mosquito (C6/36), cultura de células de mamífero (HepG2) e infecção em cérebro de camundongos neonatos. Utilizando sequenciamento de nova geração, foi possível verificar as mutações adquiridas ao longo de passagens em cada sistema de cultura. Foram realizadas 20 passagens seriadas em célula C6/36 e seis passagens alternadas entre C6/36 e HepG2. Os vírus obtidos na décima sexta e vigésima passagens do modelo seriado e na quarta e sexta passagens do modelo alternado foram completamente sequenciados utilizando a plataforma de sequenciamento em larga escala Ion Torrent. A análise das sequências revelou duas populações virais claramente distintas, já observadas a partir de décima sexta passagem, identificadas através da deleção de dois códons no sítio de glicosilação do domínio I da proteína de Envelope. Essa deleção induziu aumento na fusão do vírus à célula de mosquito, visto que a partir dessa passagem houve aumento no efeito citopático do vírus e na carga viral produzida durante infecções em células de mosquito. Contudo, essa mutação teve um perfil deletério em células humanas, fato deduzido pelo total desaparecimento da população com a deleção durante as passagens alternadas. Além desta deleção, foram detectadas sete mutações não sinônimas em região de proteínas não estruturais com porcentagens muito próximas, sugerindo que as mesmas fazem parte de uma mesma população. A cepa JHA teve seu caráter neurovirulento perdido após 29 passagens em C6/36, porém rapidamente recuperado após uma única passagem em cérebro de camundongo neonato. O sequenciamento dos vírus dessas passagens mostrou certa variabilidade em sítios distintos entre as variantes do vírus parental, vírus não neurovirulento e vírus neurovirulento passado em camundongo. Esse resultado indicou que aparentemente, não há sítios específicos determinantes de neurovirulência em DENV2, ao menos no nosso modelo, mas sim, um conjunto de mutações podem levar ao fenótipo neurovirulento, a depender das condições as quais o vírus é exposto. / Dengue is a viral disease that affects several countries, infecting thousands of people annually. It is transmitted by blood meal of the female Aedes sp mosquitoes infected. Symptoms have a wide range of variation, ranging from asymptomatic to severe symptoms, including hypovolemia and death. The need for adaptation in such distinct systems (insect and mammalian) restricts the variability that the viruses can acquire, allowing them to adapt to both hosts with similar replicative efficiency. Studies performed with other flaviviruses have shown that acquisition of variability occurs differently between the mammalian host and the insect vector, allowing the virus to adaptat in both systems. Therefore, this study investigated the adaptation of two strains of dengue virus, the ACS-46, not neurovirulent for adult mice and JHA strain, which is neurovirulent for adult mice. The study was done using mosquito cells culture (C6/36), mammalian cells (HepG2) and in vivo infection in newborn mouse brain. Using next-generation sequencing, we analyzed the mutations acquired over passages in each culture system. Twenty serial passages were conducted in C6/36 cells and six alternate passages between C6/36 and HepG2. Viruses obtained in the sixteenth and twenty passages from the serial experiment and the fourth and sixth passages from alternate model were completely sequenced using the next generation sequencing platform Ion Torrent. Sequence analysis revealed two clearly distinct viral populations observed from the sixteenth passage identified by deletion of two codons in the glycosylation site in the envelope protein domain I. This deletion led to increased fusion of the virus to mosquito cell, since the cytopathic effect increased from this passage to next as well as the viral load. However, this mutation had a deleterious profile in human cells since the mutated population was vanished during the alternate passages. It was also identified seven non-synonymous mutations in the region of nonstructural proteins with very similar percentages, suggesting that they belong to the same population. JHA strain lost the neurovirulent characteristic after 29 passages in C6/36, but quickly recovered it after a single passage in newborn mouse brain. The sequencing of the virus of these passages showed some variability in different sites among the parental virus, not neurovirulent viruses and neurovirulent virus after the single passage in mice. These data indicated that apparently there is no specific determinants of neurovirulence in DENV2, at least in our model, but rather a set of mutations can lead to neurovirulent phenotype, depending on the conditions in which the virus is exposed.

This literature review will discuss Zika virus and the salient research on antibody dependent enhancement and how this mechanism may lead to congenital defects. Specific objectives include: the mechanism of antibody dependent enhancement, Zika and dengue virus pathogenesis, placenta pathophysiology, and how changes in viral virulence may play a role the pathogenesis of neurologic congenital defects seen in infants infected with Zika virus in utero. While some cohort studies have examined the relationship between prior dengue immunity, Zika virus infection in pregnancy, and effects on neonatal outcomes further prospective studies using large cohorts and more detailed lab testing and imaging is essential to better understand this relationship. A proposed study enrolling a large cohort of women in the 6th- 8th week of pregnancy from Northeastern Brazil will seek to further describe what additional risk dengue immunity may pose in the context of Zika virus. This risk is essential to understand, as Zika and Dengue viruses co-circulate in many regions of the world. Furthermore, participants in the proposed study will undergo bi-weekly screening for Zika virus through laboratory and ultrasound testing until their delivery. Infants will then have full neurologic testing and MRI scanning for the following year after birth to characterize any congenital defects. Neonates born to mothers with prior dengue immunity who contract Zika virus during pregnancy will be compared to neonates not exposed to Zika virus in utero. This experiment will illuminate the associated risk and evidence of ADE occurring with prior dengue immunity and Zika virus infection during pregnancy. Results from this study will not only help define risks of congenital defects with Zika virus, it will inform vaccine research and elucidate challenges in the administration of the current tetravalent dengue vaccine.