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Rocio virus (ROCV) is a highly neuropathogenic mosquito-transmitted flavivirus responsible for an unprecedented outbreak of human encephalitis during 1975–1976 in Sao Paulo State, Brazil. Previous studies have shown an increased number of inflammatory macrophages in the central nervous system (CNS) of ROCV-infected mice, implying a role for macrophages in the pathogenesis of ROCV. Here, we show that ROCV infection results in increased expression of CCL2 in the blood and in infiltration of macrophages into the brain. Moreover, we show, using CCR2 knockout mice, that CCR2 expression is essential for macrophage infiltration in the brain during ROCV infection and that the lack of CCR2 results in increased disease severity and mortality. Thus, our findings show the protective role of CCR2-mediated infiltration of macrophages in the brain during ROCV infection., Rocio virus (ROCV) is a highly neuropathogenic mosquito-transmitted flavivirus responsible for an unprecedented outbreak of human encephalitis in Brazil. Here, we show that infiltrated macrophages in the brain may be protective in the pathogenesis of ROCV in a mouse model.

Dengue, a disease caused by any of the four serotypes of dengue viruses, is the most important arthropod-borne viral disease in the world in terms of both morbidity and mortality. The infection by these viruses induces a plethora of clinical manifestations ranging from asymptomatic infections to severe diseases with involvement of several organs. Severe forms of the disease are more frequent in secondary infections by distinct serotypes and, consequently, a dengue vaccine must be tetravalent. Although several approaches have been used on the vaccine development, no vaccine is available against these viruses, especially because of problems on the development of a tetravalent vaccine. Here, we describe briefly the vaccine candidates available and their ability to elicit a protective immune response. We also discuss the problems and possibilities of any of the vaccines in final development stage reaching the market for human use.

Dengue is the most important arbovirus disease throughout the world and it is responsible for more than 500,000 dengue hemorrhagic cases and 22,000 deaths every year. One vaccine was recently licensed for human use in Brazil, Mexico and Philippines and although at least seven candidates have been in clinical trials the results of the most developed CYD vaccine have demonstrated immunization problems, such as uneven protection and interference between serotypes. We constructed a vaccine candidate based on vesicular stomatitis virus (VSV) expression of pre-membrane (prM) and envelope (E) proteins of dengue-2 virus (DENV-2) and tested it in mice to evaluate immunogenicity and protection against DENV-2 infection. VSV has been successfully used as vaccine vectors for several viruses to induce strong humoral and cellular immune responses. The VSV-DENV-2 recombinant was constructed by inserting the DENV-2 structural proteins into a VSV plasmid DNA for recombinant VSV-DENV-2 recovery. Infectious recombinant VSV viruses were plaque purified and prM and E expression were confirmed by immunofluorescence and radiolabeling of proteins of infected cells. Forty Balb/C mice were inoculated through subcutaneous (s.c.) route with VSV-DENV-2 vaccine in a two doses schedule 15 d apart and 29 d after first inoculation, sera were collected and the mice were challenged with 50 lethal doses (LD50) of a neurovirulent DENV-2. The VSV-DENV-2 induced anti-DENV-2 antibodies and protected animals in the challenge experiment comparable to DENV-2 immunization control group. We conclude that VSV is a promising platform to test as a DENV vaccine and perhaps against others Flaviviridae.

Rocio virus (ROCV) was the causative agent of an unprecedented outbreak of encephalitis during the 1970s in the Vale do Ribeira, Sao Paulo State, in the Southeast region of Brazil. Surprisingly, no further cases of ROCV infection were identified after this outbreak; however, serological surveys have suggested the circulation of ROCV among humans and animals in different regions of Brazil. Cross-protective immunity among flaviviruses is well documented; consequently, immunity induced by infections with other flaviviruses endemic to Brazil could potentially be responsible for the lack of ROCV infections. Herein, we evaluated the cross-protection mediated by other flaviviruses against ROCV infection using an experimental C57BL/6 mouse model. Cross-protection against ROCV infection was observed when animals had prior exposure to Ilheus virus or Saint Louis encephalitis virus, suggesting that cross-reactive anti-flavivirus antibodies may limit ROCV disease outbreaks.

Aims: Chlorophyllin (CHLN), a synthetic derivative of chlorophyll, was assayed in the replication of poliovirus (PV-1) and bovine herpesvirus (BoHV-1) in HEp-2 cell cultures. Methods and Results: Virucidal activity of CHLN was evaluated and the time-of-addition assay was performed as follows: before the infection (−1 and −2 h), at the time of the infection (0 h) and after the infection (1 and 2 h). Plaque reduction assay (PRA) showed that CHLN inhibited BoHV-1 and PV-1 infection and the 50% inhibitory concentrations (IC50) against BoHV-1 and PV-1 infection were 8·6 and 19·8 μg ml−1, respectively. The time-of-addition study demonstrated that the CHLN was effective inhibiting viral replication in 51% and 66·5% for PV-1 and BoHV-1, respectively, at the highest concentration of 20·0 μg ml−1, when added during the infection. The directed effect of CHLN on viral strains demonstrated an inhibition of 62% and 66·4% for PV-1 and BoHV-1, respectively, by PRA. Conclusions: These results demonstrated that CHLN could be used as an antiviral suggesting directed activity on virus particles and on virus-receptor sites to BoHV. For poliovirus, CHLN also demonstrated virucide activity, moreover, showed to inhibit early steps of the replication cycle. Significance and Impact of the Study: CHLN demonstrated promising selectivity index for both virus strains; therefore, it can be used for the development of an antiviral agent.

An indirect solid-phase enzyme immunoassay (EIA) was developed for the detection of poliovirus antigen. Virus antigen was obtained in LLC-MK2 cell cultures and used to prepare antibodies in rabbit and guinea pig. Antibodies were evaluated by double immunodiffusion and neutralization test. Optimal concentrations of guinea pig and rabbit immunoglobulins were determined by checkerboard titration. Microtitre plates were coated with 15.0 µg/ml guinea pig anti-polio immunoglobulin and rabbit anti-polio immunoglobulin at the concentration of 7.94 µg/ml was used as detecting antibody. The standard curve with eight different antigen concentrations in eight replicates resulted in a coefficient of variation (CV) between 2.1% to 7.8%. The dose-response relationship was determined by simple linear regression with a coefficient of correlation (R²) equal to 96.4%. The assay detected a minimum of 2.3 µg/ml poliovirus antigen.O trabalho apresenta o desenvolvimento de um ensaio imunoenzimático indireto para a detecção de antígeno de poliovírus. O antígeno viral foi obtido em cultura de células LLC-MK2 e usado para imunização de coelho e cobaia. Os soros hiperimunes foram avaliados por imunodifusão dupla e teste de neutralização. Após padronização, o soro de captura, produzido em cobaia, foi usado na concentração protéica de 15.0 µg/ml para sensibilizar microplacas de poliestireno e o soro de coelho (detector) foi usado na concentração de 7.94 µg/ml. A curva padrão resultante da utilização de oito diferentes concentrações do antígeno padrão definiu um coeficiente de variação de 2.1% a 7.8%. A relação dose-resposta foi determinada por regressão linear simples com o estabelecimento do coeficiente de correlação (R²) igual a 96.4%. O ensaio possibilitou a detecção mínima de 2.3 µg/ml de antígeno de poliovírus.

Between May and August in 2003, a total of 251 fecal samples were collected from children and adults with diarrhea (5 inpatients and 246 outpatients) at a private hospital in the city of Ponta Grossa, the state of Paraná, Brazil. Group A rotavirus was detected in 71 of 251 (28.3%) specimens: 55 (77.5%) from children under 5 years of age and 16 (22.5%) from individuals aged 6-72 years. All 71 strains exhibited a "long" RNA pattern when analyzed by PAGE. Sixty-one positive samples that yielded enough RNA were submitted to PCR genotyping. The most frequent G/P genotype combination detected was G1P[8] (86.9%; 53/61) followed by G9P[8] (3.3%; 2/61) and G12P[9] (1.6%; 1/61). Rotaviruses with G2, G3, G4, P[4], or P[6] specificity were not detected. For three strains (4.9%) bearing G1 genotype, the VP4 specificity could no be determined, and two specimens (3.3%) remained G/P non-typeable. One rotavirus strain (HC91) bearing G12P[9] genotype with a "long" electropherotype was isolated from an 11-month-old boy with diarrhea for the first time in Brazil. The cell-culture grown HC91 strain was shown to belong to serotype G12 by neutralization.

Rotaviruses (RV) are the single most important cause of severe diarrheal illness in infants and young children in both developed and developing countries worldwide. They affect mainly children less than 24 months of age. Presently, we adapted human rotavirus strains from field materials in cell culture, as well as, studied their properties by the analyses of the cytopathic effect, immunofluorescence features, plaque properties and virus genome stability. The study was carried out with 53 rotavirus-positive fecal specimens, collected in the city of Ponta Grossa, Parana, before the introduction of vaccination program in Brazil. The samples were submitted to at least 3 blind passages in MA-104 cell culture before discarded as non-cultivable. The adaptation process was monitored by the development of the cytopathic effect, immunofluorescence assay , plaque assay and genome stability by reverse transcriptase-polymerase chain reactions amplification. Fourteen human rotavirus strains were adapted to grow in cell culture. The isolation was demonstrated by the development of typical cytopathic effect. Immunofluorescence assay revealed granular inclusions with specific fluorescence mainly at the perinuclear area of the infected cells. Plaque assay allowed the demonstration of plaques with varying diameter depending upon the strains. Reverse transcriptase-polymerase chain reactions resulted in amplification and genotyping, demonstrating the stability of the genome through cell culture adaptation. DOI: http://dx.doi.org/10.17525/vrr.v19i1.97

Rotaviruses are common pathogens and the causal agents of acute diarrhea among children and young animals. The involvement of rotavirus in human diarrheal disease among population of urban and rural areas of the city of Londrina, Parana was evaluated. Nine hundred and five fecal specimens from persons with diarrhea were studied, being 686 and 219 from urban and rural areas, respectively. Thirty-eight samples (4,2%) were positive for rotavirus by polyacrylamide gel electrophoresis of viral RNA and latex agglutination test of which 36 were from urban and two from rural areas. Out of the positive specimens, 17 strains were further characterized by RT-PCR typing assay, resulting in 16 strains of G1 genotype while one sample was found to be a mixture of G1 and G3 genotypes.Os rotavírus são patógenos comuns e causam diarréia aguda em crianças e animais jovens. Neste trabalho avaliamos a participação do vírus na diarréia de populações humanas das áreas urbana e rural da cidade de Londrina, Paraná. Foram analisadas 905 amostras fecais de indivíduos com diarréia aguda, sendo 686 e 219 amostras das zonas urbana e rural, respectivamente. Trinta e oito amostras (4,2%) foram consideradas positivas pelas técnicas de eletroforese em gel de poliacrilamida do RNA viral e aglutinação passiva de látex, das quais 36 da área urbana e dois da área rural. Das amostras positivas, 17 foram genotipadas por RT-PCR tendo sido caracterizadas 16 cepas G1 e uma considerada mistura dos genótipos G1 e G3.

Os rotavírus são os mais importantes agentes de gastroenterite em crianças e animais jovens. Neste trabalho, os aspectos da patogenia em cultura de células MA-104 infectadas com a cepa 1154 de rotavirus porcino foram determinados e comparados com a cepa padrão SA-11. Foi determinado que a cepa 1154 pertence ao genótipo G5P[6], não possui atividade hemaglutinante e é dependente de ácido siálico nos receptores celulares e da tripsina para formação do plaque. A cepa desenvolve efeito citopático (ECP) rápido, com grande capacidade de disseminação entre as células adjacentes, além de possuir mutantes com tamanho de plaque diferente. Em paralelo ao ECP foi observado o efeito de fragmentação nuclear de células infectadas, seguido da diminuição da atividade desidrogenásica mitocondrial. Sugere-se que estes efeitos ajam de modo cooperativo e acabem levando à morte celular com implicações diretas para patogenia da infecção pelos RV. Rotaviruses (RV) are the most important agents of acute diarrhea in children and young animals. Cytopathogenic aspects of a highly cytopathic porcine RV strain (1154) and that of the prototype simian (SA-11) RV were underlined and comparatively studied. The strain 1154 was genotyped as G5P[6], and was found not to present hemagglutination activity. It is dependent upon sialic acid in the cell receptor, as well as, trypsin for plaque formation. Overall, 1154 cytopathic effect (CPE) is similar to the other RV strains, nevertheless, with high capacity to spread to adjacent cells. Paralleled to the CPE, the nuclear fragmentation of infected cells was observed followed by the decrease of mitochondrial dehydrogenase activity. It is suggested that these features together lead to cell death and possibly have direct implications in the pathogenesis of RV infection.

Rotaviruses have been implicated as the major causal agents of acute diarrhoea in mammals and fowls. Experimental rotavirus infection have been associated to a series of sub-cellular pathologic alterations leading to cell lysis which may represent key functions in the pathogenesis of the diarrhoeic disease. The current work describes the cytopathic changes in cultured MA-104 cells infected by a simian (SA-11) and a porcine (1154) rotavirus strains. Trypan blue exclusion staining showed increased cell permeability after infection by both strains, as demonstrated by cell viability. This effect was confirmed by the leakage of infected cells evaluated by chromium release. Nuclear fragmentation was observed by acridine orange and Wright staining but specific DNA cleavage was not detected. Ultrastructural changes, such as chromatin condensation, cytoplasm vacuolisation, and loss of intercellular contact were shown in infected cells for both strains. In situ terminal deoxynucleotidyl transferase (Tunel) assay did not show positive result. In conclusion, we demonstrated that both strains of rotavirus induced necrosis as the major degenerative effect.

Acridine orange is a metachromatic intercalator used extensively in histochemistry to differentiate double- from single-stranded (ds, ss) nucleic acid by the emission of green and red fluorescence, respectively, under ultraviolet light. In the present study we standardised a protocol in order to use acridine orange to detect rotavirus ds RNA in polyacrylamide gels and compared it to silver and ethidium bromide staining. We demonstrated that the simplest and best condition was attained when gels containing rotavirus ds RNA bands, stained in green, were treated with 4.3 microM acridine orange after electrophoresis and destained with distilled water pH 6 at 37 degrees C. Under this protocol, rotavirus RNA concentration was calculated and the mean minimum amounts of nucleic acid detected by acridine orange, ethidium bromide, and silver staining were 26.0 +/- 4.29, 15.6 +/- 1.48 and 1.06 +/- 0.11 ng, respectively. The comparison of acridine orange sensitivity with ethidium bromide and silver staining, for 25 field strains of rotavirus and one cell-adapted strain (SA11), demonstrated concurrent results in 80% of the specimens. Red colour emission resulting from the interaction of acridine orange with ss nucleic acid was also shown by testing denatured 0.5 kb HindIII digest of lambda phage DNA. Furthermore, it was demonstrated that rotavirus ds RNA could be used for reverse transcription activity, followed by PCR amplification, after acridine orange staining. In conclusion, although acridine orange is less sensitive than ethidium bromide and silver staining, its practicality, low cost, metachromatic properties, and its non-interference on RT-PCR should be considered. It is suggested the use of acridine orange as an appropriate stain for various purposes in virology, as well as for the molecular biology of nucleic acid.