Avaliação de danos causados pelo Barley yellow dwarf virus: PAV em cultivares de trigo no Brasil

Com o objetivo de avaliar os danos causados pelo Barley yellow dwarf virus - PAV (BYDV-PAV), em cinco cultivares de trigo (BRS 177, BRS 179, BRS 194, BRS Camboatá e BRS Angico), foi conduzido um experimento no telado da Embrapa-Trigo (Passo Fundo RS) no ano de 2005. Os danos induzidos pelo BYDV-PAV foram determinados por meio de análise de características agronômicas (estatura das plantas e massa de matéria seca) e do rendimento (número de afilhos, espigas e grãos por planta; massa de mil grãos). Os dados foram submetidos à análise de variância e as médias ao teste de Tukey a 5%. Danos significativos em função da infecção viral foram observados em todas as variáveis avaliadas. A característica agronômica mais afetada foi a massa de matéria seca, que variou de 26,1% (BRS 177) a 51,4% (BRS 179). Para estatura de plantas foram observadas reduções de 12,5% (BRS 177) a 15,5% (BRS Camboatá). O rendimento total de grãos foi o mais afetado pela infecção viral, sendo que, danos significativos foram observados em todas as cultivares, cuja redução variou de 34,2% (BRS Camboatá) a 60,8% (BRS 179). No número médio de afilhos por planta, apenas as cultivares BRS Angico e BRS 179 apresentaram reduções de 20% e 26,6%, respectivamente. A redução do número médio de grãos variou de 26,1% (BRS Camboatá) a 54,3% (BRS 179). Também ocorreu diminuição no peso de mil grãos com redução que variou de 16,9% (BRS Camboatá) a 38,4% (BRS 194).

Circulation of antibodies against yellow fever virus in a simian population in the area of Porto Primavera Hydroelectric Plant, São Paulo, Brazil

Yellow fever (YF) is an acute viral infectious disease transmitted by mosquitoes which occurs in two distinct epidemiological cycles: sylvatic and urban. In the sylvatic cycle, the virus is maintained by monkey's infection and transovarian transmission in vectors. Surveillance of non-human primates is required for the detection of viral circulation during epizootics, and for the identification of unaffected or transition areas. An ELISA (enzyme-linked immunosorbent assay) was standardized for estimation of the prevalence of IgG antibodies against yellow fever virus in monkey sera (Alouatta caraya) from the reservoir area of Porto Primavera Hydroelectric Plant, in the state of São Paulo, Brazil. A total of 570 monkey sera samples were tested and none was reactive to antibodies against yellow fever virus. The results corroborate the epidemiology of yellow fever in the area. Even though it is considered a transition area, there were no reports to date of epizootics or yellow fever outbreaks in humans. Also, entomological investigations did not detect the presence of vectors of this arbovirus infection. ELISA proved to be fast, sensitive, an adequate assay, and an instrument for active search in the epidemiological surveillance of yellow fever allowing the implementation of prevention actions, even before the occurrence of epizootics.

Isolation of yellow fever virus (YFV) from naturally infectied Haemagogus (Conopostegus) leucocelaenus (diptera, cukicudae) in São Paulo State, Brazil, 2009

After detecting the death of Howlers monkeys (genus Alouatta) and isolation of yellow fever virus (YFV) in Buri county, São Paulo, Brazil, an entomological research study in the field was started. A YFV strain was isolated from newborn Swiss mice and cultured cells of Aedes albopictus - C6/36, from a pool of six Haemagogus (Conopostegus) leucocelaenus (Hg. leucocelaenus) mosquitoes (Dyar & Shannon) collected at the study site. Virus RNA fragment was amplified by RT-PCR and sequenced. The MCC Tree generated showed that the isolated strain is related to the South American I genotype, in a monophyletic clade containing isolates from recent 2008-2010 epidemics and epizootics in Brazil. Statistical analysis commonly used were calculated to characterize the sample in relation to diversity and dominance and indicated a pattern of dominance of one or a few species. Hg. leucocelaenus was found infected in Rio Grande do Sul State as well. In São Paulo State, this is the first detection of YFV in Hg. leucocelaenus.

Yellow fever virus isolated from a fatal post vaccination event: an experimental comparative study with the 17DD vaccine strain in the Syrian hamster (Mesocricetus auratus)

In order to investigate the pathogenicity of the virus strain GOI 4191 that was isolated from a fatal adverse event after yellow fever virus (YFV) vaccination, an experimental assay using hamsters (Mesocricetus auratus) as animal model and YFV 17DD vaccine strain as virus reference was accomplished. The two virus strains were inoculated by intracerebral, intrahepatic and subcutaneous routes. The levels of viremia, antibody response, and aminotransferases were determined in sera; while virus, antigen and histopathological changes were determined in the viscera. No viremia was detected for either strain following infection; the immune response was demonstrated to be more effective to strain GOI 4191; and no significant aminotransferase levels alterations were detected. Strain GOI 4191 was recovered only from the brain of animals inoculated by the IC route. Viral antigens were detected in liver and brain by immunohistochemical assay. Histothological changes in the viscera were characterized by inflammatory infiltrate, hepatocellular necrosis, and viral encephalitis. Histological alterations and detection of viral antigen were observed in the liver of animals inoculated by the intrahepatic route. These findings were similar for both strains used in the experiment; however, significant differences were observed from those results previously reported for wild type YFV strains.

First report of yellow fever virus in non-human primates in the State of Parana, Brazil

Sylvatic yellow fever is a zoonosis associated mainly with wild animals, especially those in the genus Alouatta, that act as the source of infection. Once infected, these animals pass the disease on to humans by way of an infected mosquito belonging to the genera Aedes, Haemagogus, or Sabethes. The present study is the first report of a case of yellow fever in non-human primates (NHP) in the State of Paraná, Brazil. After the case was diagnosed, several prophylactic measures were adopted to prevent outbreaks of the disease in humans.

Frequency of histopathological changes in Howler monkeys ( Alouatta sp.) naturally infected with yellow fever virus in Brazil

Abstract: INTRODUCTION: Due to the importance that Howler monkeys have on the yellow fever (YF) epidemiological sylvatic cycle in Brazil, more accurate morphological diagnostic criteria needs to be established, especially considering the differences that may exist between the genera of Brazilian non-human primates (NHPs) involved in yellow fever virus (YFV) epizootics. METHODS: Records of YF epizootics in NHPs in Brazil between 2007 and 2009 were obtained from the Brazilian Ministry of Health database to select YF positive (n=98) Howler monkeys (Alouatta sp.) for this study. The changes described in the histopathological reports were categorized by organ and their frequencies calculated. RESULTS: The most frequent lesions observed in the animals with YF were hepatocyte apoptosis (Councilman body formation), midzonal hepatocyte necrosis, steatosis, liver hemorrhage, inflammatory mononuclear cell infiltration of the liver, renal acute tubular necrosis and interstitial nephritis. Midzonal hepatocyte necrosis, steatosis and hemorrhage presented positive correlations with apoptosis of hepatocytes, suggesting strong YFV pathogenic effect association; they were also the main histopathological changes in the Alouatta sp. A pronounced negative correlation between apoptosis of hepatocytes and hepatic mononuclear cell infiltration pointed to significant histopathological differences between YFV infection in Howler monkeys and humans. CONCLUSIONS: The results warn that NHPs may exhibit different response patterns following YFV infection and require a more careful diagnosis. Presumptive diagnosis based on primate histopathological lesions may contribute to public health service control.

Molecular analysis of yellow fever virus 17DD vaccine strain

The Oswaldo Cruz Foundation produces most of the yellow fever (YF) vaccine prepared world wide. As part of a broader approach to determine the genetic variability in YF l7D seeds and vaccines and its relevance to viral attenuation the 17DD virus was purifed directly from chick embryo homogenates which is the source of virus used for vaccination of millions of people in Brazil and other countries for half a century. Neutralization and hemagglutination tests showed that the purified virus is similar to the original stock. Furthermore, radioimmune precipitation of 35S-methionine-labeled viral proteins using mouse hyperimmune ascitic fluid revealed identical patterns for the purified 17DD virus and the YF l7D-204 strain except for the 17DD E protein which migrated slower on SDS-PAGE. This difference is likely to be due to N-linked glycosylation. Finally, comparison by northern blot nybridization of virion RNAs of purified 17DD with two other strains of YF virus only fenome-sized molecules for all three viruses. These observations suggest that vaccine phenotype is primarily associated with the accumulation of mutations.

The early use of yellow fever virus strain 17D for vaccine production in Brazil - a review

The use of yellow fever (YF) virus 17D strain for vaccine production adapted in Brazil since its introduction in 1937 was reviewed. This was possible due to the availability of official records of vaccine production. The retrieved data highlight the simultaneous use of several serially passaged 17D substrain viruses for both inocula and vaccine preparation that allowed uninterrupted production. Substitution of these substrain viruses became possible with the experience gained during quality control and human vaccination. Post-vaccinal complications in humans and the failure of some viruses in quality control tests (neurovirulence for monkeys) indicated that variables needed to be reduced during vaccine production, leading to the development of the seed lot system. The 17DD substrain, still used today, was the most frequently used substrain and the most reliable in terms of safety and efficacy. For this reason, it is possible to derive an infectious cDNA clone of this substrain combined with production in cell culture that could be used to direct the expression of heterologous antigens and lead to the development of new live vaccines.

Oral Susceptibility to Yellow Fever Virus of Aedes aegypti from Brazil

The oral susceptibility to yellow fever virus was evaluated in 23 Aedes aegypti samples from Brazil. Six Ae. aegypti samples from Africa, America and Asia were also tested for comparison. Mosquito samples from Asia showed the highest infection rates. Infection rates for the Brazilian Ae. aegypti reached 48.6%, but were under 13% in 60% of sample tested. We concluded that although the low infection rates estimated for some Brazilian mosquito samples may not favor the establishment of urban cycle of yellow fever in some parts of the country, the founding of Ae. aegypti of noteworthy susceptibility to the virus in cities located in endemic and transition areas of sylvatic yellow fever, do pose a threat of the re-emergence of the urban transmission of the disease in Brazil.

A comparative study of the effect of multiple immersions on Aedini (Diptera: Culicidae) mosquito eggs with emphasis on sylvan vectors of yellow fever virus

The effect of multiple immersions on Haemagogus janthinomys , Haemagogus leucocelaenus , Aedes albopictus and Ochlerotatus terrens eggs was studied. Eggs were collected in April, June, October and December of 2011 in Minas Gerais, Brazil. Most of the Aedes and Ochlerotatus eggs hatched upon the first immersion, while Haemagogus eggs showed a varied instalment hatching response. The number of immersions required for hatching increased for eggs collected closer to the dry winter season.

Characterization of Tomato yellow spot virus, a novel tomato-infecting begomovirus in Brazil

The objective of this work was the biological and molecular characterization of a begomovirus detected in São Joaquim de Bicas, Minas Gerais, Brazil, named TGV-[Bi2], by determining its host range, complete nucleotide sequence and phylogenetic relationships with other begomoviruses. Biological characterization consisted of a host range study using either sap inoculation or particle bombardment as inoculation methods. The yellow spot virus can infect plants in Solanaceae and Amaranthaceae, including economically importat crops as sweet pepper, and weeds as Datura stramonium and Nicotiana silvestris. For the molecular characterization, the full-length genome (DNA-A and DNA-B) was amplified, cloned and completely sequenced. Sequence comparisons and phylogenetic analyses indicated that TGV-[Bi2] constitutes a novel begomovirus species named Tomato yellow spot virus (ToYSV), closely related to Sida mottle virus (SiMoV).

Watermelon transformation with Zucchini yellow mosaic virus coat protein gene and comparison with parental cultivar

The objective of this work was to transfer Zucchini yellow mosaic virus coat protein (ZYMV-CP) and neomycin phosphotransferase II (NPT II) genes to the watermelon 'Crimson Sweet'(CS) genome, and to compare the transgenic progenies T1 and T2 with the nontransformed parental cultivar for morphological, pomological, growth and yield characteristics. The ZYMV-CP gene was transferred by Agrobacterium tumefaciens. The presence of the gene in transgenic T0, T1 and T2 plants was determined by polymerase chain reaction, and the results were confirmed by Southern blot. Two experiments were performed, one in the winter-spring and the other in the summer-autumn. In both experiments, the hypocotyl length of transgenic seedlings was significantly higher than that of nontransgenic parental ones. In the second experiment, the differences between transgenic and nontransgenic individuals were significant concerning fruit rind thickness, flesh firmness, fruit peduncle length, size of pistil scar, and a* values for fruit stripe or flesh color. Transferring ZYMV-CP gene to CS genome affected only a few characteristics from the 80 evaluated ones. The changes in rind thickness, flesh firmness and flesh color a* values are favorable, while the increase in the size of pistil scar is undesirable. The transgenic watermelon line having ZYMV-CP gene and the parental cultivar CS are very similar.

Distinct features of Pepper yellow mosaic virus isolates from tomato and sweetpepper

Determination of virus diversity in the field is vital to support a sustainable breeding program for virus resistance of horticultural crops. The present study aimed to characterize four field potyvirus isolates found naturally infecting sweet pepper (Capsicum annuum) (Sa66 and Sa115) and tomato (Lycopersicon esculentum) (IAC3 and Sa21) plants. Their biological characteristics revealed differences among the isolates in their ability to infect distinct Capsicum spp. and tomato genotypes, and in the severity of symptoms caused by these isolates compared to the infection caused by an isolate of Pepper yellow mosaic virus (PepYMV). Absence of cross-reaction was found among the studied isolates with antiserum against Potato virus Y (PVY). However, all isolates reacted, at different intensities, with antiserum against PepYMV. All isolates showed high identity percentage (97 to 99%) of the amino acid sequence of the coat protein with PepYMV (accession AF348610) and low (69 to 80%) with other potyvirus species. The comparison of the 3' untranslated region also confirmed this finding with 97 to 98% identity with PepYMV, and of 47 to 71% with other potyviruses. The results showed that PepYMV isolates were easily differentiated from PVY by serology and that the host response of each isolate could be variable. In addition, the nucleotide sequence of the coat protein and 3' untranslated region was highly conserved among the isolates.

Sugarcane yellow leaf virus infection leads to alterations in photosynthetic efficiency and carbohydrate accumulation in sugarcane leaves

Infection by Sugarcane yellow leaf virus (ScYLV) causes severe leaf symptoms in sugarcane (Saccharum spp.) hybrids, which indicate alterations in its photosynthetic apparatus. To gain an overview of the physiological status of infected plants, we evaluated chlorophyll a fluorescence and gas exchange assays, correlating the results with leaf metabolic surveys, i.e., photosynthetic pigments and carbohydrate contents. When compared to healthy plants, infected plants showed a reduction in potential quantum efficiency for photochemistry of photosystem (PSII) and alterations in the filling up of the plastoquinone (PQ) pool. They also showed reduction in the CO2 net exchange rates, probably as a consequence of impaired quantum yield. In addition, reductions were found in the contents of photosynthetic leaf pigments and in the ratio chlorophyll a/chlorophyll b (chla/chlb). Carbohydrate content in the leaves was increased as a secondary effect of the ScYLV infection. This article discusses the relation of virus replication and host defense responses with general alterations in the photosynthetic apparatus and in the metabolism of infected plants.