RESUMO
St. Louis encephalitis virus (SLEV) is a neglected mosquito-borne flavivirus that causes severe neurological disease in humans. SLEV replication in the central nervous system (CNS) induces the local production of interferons (IFNs), which are attributed to host protection. The antiviral response to SLEV infection in the CNS is not completely understood, which led us to characterize the roles of IFNs using mouse models of St. Louis encephalitis. We infected mice deficient in type I IFN receptor (ABR-/-) or deficient in Type II IFN (IFNγ-/-) and assessed the contribution of each pathway to disease development. We found that type I and II IFNs play different roles in SLEV infection. Deficiency in type I IFN signaling was associated to an early and increased mortality, uncontrolled SLEV replication and impaired ISG expression, leading to increased proinflammatory cytokine production and brain pathology. Conversely, IFNγ-/- mice were moderately resistant to SLEV infection. IFNγ deficiency caused no changes to viral load or SLEV-induced encephalitis and did not change the expression of ISGs in the brain. We found that type I IFN is essential for the control of SLEV replication whereas type II IFN was not associated with protection in this model.
Assuntos
Encéfalo/imunologia , Encéfalo/virologia , Vírus da Encefalite de St. Louis/imunologia , Encefalite de St. Louis/imunologia , Interferon Tipo I/imunologia , Interferon gama/imunologia , Animais , Encéfalo/patologia , Modelos Animais de Doenças , Interferon Tipo I/genética , Interferon gama/genética , Camundongos , Camundongos Endogâmicos C57BL , Carga Viral , Replicação Viral/imunologiaRESUMO
Saint Louis encephalitis virus (SLEV) and West Nile virus (WNV) are two of the major causes of arboviral encephalitis in the Americas. The co-circulation of related flaviviruses in the Americas and prior vaccination against flaviviruses pose problems to the diagnostic specificity of serological assays due to the development of cross-reactive antibodies. An accurate diagnosis method capable of differentiating these related viruses is needed. NS1 is a glycosylated, nonstructural protein, of about 46â¯kDa which has a highly conserved structure. Anti-NS1 antibodies can be detected within 4-8 days after the initial exposure and NS1 is the least cross-reactive of the flaviviral antigens. This study was aimed to generate SLEV and WNV NS1 recombinants proteins for the development of a flavivirus diagnostic test. Local Argentinian isolates were used as the source of NS1 gene cloning, expression, and purification. The protein was expressed in Escherichia coli as inclusion bodies and further purified by metal-chelating affinity chromatography (IMAC) under denaturing conditions. Human sera from SLEV and WNV positive cases showed reactivity to the recombinant NS1 proteins by western blot. The unfolded NS1 proteins were also used as immunogens. The polyclonal antibodies elicited in immunized mice recognized the two recombinant proteins with differential reactivity.
Assuntos
Anticorpos Antivirais/biossíntese , Antígenos Virais/imunologia , Vírus da Encefalite de St. Louis/imunologia , Encefalite de St. Louis/diagnóstico , Proteínas não Estruturais Virais/imunologia , Febre do Nilo Ocidental/diagnóstico , Vírus do Nilo Ocidental/imunologia , Animais , Especificidade de Anticorpos , Antígenos Virais/biossíntese , Antígenos Virais/genética , Argentina , Western Blotting , Cromatografia de Afinidade , Clonagem Molecular , Reações Cruzadas , Diagnóstico Diferencial , Vírus da Encefalite de St. Louis/química , Vírus da Encefalite de St. Louis/genética , Encefalite de St. Louis/imunologia , Encefalite de St. Louis/virologia , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Corpos de Inclusão/química , Camundongos , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Solubilidade , Proteínas não Estruturais Virais/biossíntese , Proteínas não Estruturais Virais/genética , Febre do Nilo Ocidental/imunologia , Febre do Nilo Ocidental/virologia , Vírus do Nilo Ocidental/química , Vírus do Nilo Ocidental/genéticaRESUMO
The aim of this study was to recognize the specific antiviral response patterns of IgG1, IgG2, IgG3 and IgG4 subclasses, elicited during St. Louis encephalitis virus (SLEV) infection in humans. Eighty-five samples of human sera from 44 patients with SLEV infection were obtained between days 1 and 365 or later, after onset of the disease. These samples were processed by immunofluorescence assay for detection of IgG1-, IgG2-, IgG3- and IgG4-specific antibodies. We demonstrate the presence of all isotypes of IgG for more than a year in patients infected with SLEV. However; isotype IgG1 was present at the highest titers, with a peak between days 8 and 30 after onset of the disease.
Assuntos
Anticorpos Antivirais/imunologia , Vírus da Encefalite de St. Louis/imunologia , Encefalite de St. Louis/imunologia , Imunoglobulina G/imunologia , Isotipos de Imunoglobulinas/imunologia , Anticorpos Antivirais/sangue , Formação de Anticorpos , Encefalite de St. Louis/virologia , Humanos , Imunoglobulina G/sangue , Isotipos de Imunoglobulinas/sangue , Fatores de TempoRESUMO
In 1998, a dengue outbreak (serotype 2) occurred in Salta province in Northern Argentina, following the first detection of dengue in the same area in 1997. We classified the serologic response of cases from 1998 as primary or secondary, since the risk of severe disease is greater for secondary cases. We studied 154 cases by plaque reduction neutralization and hemagglutination inhibition tests. Thirty-eight cases (25%) were classified as primary serologic responses and 84 cases (54%) as secondary responses. Thirty-two cases (21%) with borderline IgG titers could not be classified. Previous exposure to potentially cross-reacting flaviviruses (Saint Louis Encephalitis [SLE] and Yellow Fever [YF] viruses) was analyzed, as a possible cause of the secondary response pattern. Our results indicated that among cases classified as dengue secondary response, 83% could be attributed to previous SLE or YF exposure or serologic cross-reactivity. Vaccination against YF virus was at most a minor contributor to the secondary response pattern. The finding of a positive YF serologic result among persons not vaccinated may indicate silent circulation of YF in a region that can support both urban and jungle cycles. Other cases showing dengue secondary responses remained unexplained, suggesting the unrecognized occurrence of a previous infection with other dengue serotypes or of flaviviruses other than SLE or YF.
Assuntos
Anticorpos Antivirais/sangue , Vírus da Dengue/imunologia , Dengue/imunologia , Encefalite de St. Louis/imunologia , Febre Amarela/imunologia , Anticorpos Antivirais/imunologia , Argentina/epidemiologia , Dengue/epidemiologia , Dengue/virologia , Vírus da Dengue/isolamento & purificação , Surtos de Doenças , Encefalite de St. Louis/sangue , Ensaio de Imunoadsorção Enzimática , Humanos , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Febre Amarela/sangue , Vacina contra Febre AmarelaRESUMO
En 1998, ocurrió una epidemia de dengue (serotipo 2) en la provincia de Salta, Norte de Argentina, después de la primera detección de dengue en esa zona en 1997. En este trabajo se clasificaron las respuestas serológicas de los casos ocurridos en 1998 como primarios o secundarios, dado que riesgo de la enfermadad severa es mayor en los casos secundarios. Se estudiaron 154 casos por las pruebas de neutralización (NT) e inhibición de la hemoaglutinación. Se clasificaron 38 casos ( 25 porciento) como respuestas primarias y 84 casos (54 porciento) como respuestas secundarias. Los restantes 32 casos (21 porciento) con títulos de IgG en el límite no pudieron ser clasificados. Se analizó la exposición previa a otros flavivirus (Encefalitis de San Luis [SLE] y Fiebre Amarilla [YF]) que pueden cruzar serológicamente, como posible causa de los patrones secundarios. Nuestros resultados indican que el 83 porciento de los casos clasificados como respuesta a dengue secundaria, podrían atribuirse a exposiciones previas a los virus SLE o YF, o a reacciones serológicas cruzadas. La vacunación contra YF fue un factor menor contribuyente al patrón de respuesta secundaria encontrado. El hallazgo de serología positiva para YF en personas que no reconocen vacunación previa debe alertar acerca de la posible circulación silenciosa del virus de la YF, en una área que puede soportar tantos ciclos urbanos como selváticos. Otros casos que mostraron respuesta secundarias permanecen sin explicación, surgirindo la ocurrencia de infecciones previas por otros serotipos de dengue o por otro flavivirus distintos a SLE o YF.
Assuntos
Humanos , Anticorpos Antivirais/sangue , Vírus da Dengue/imunologia , Dengue/imunologia , Encefalite de St. Louis/imunologia , Febre Amarela/imunologia , Anticorpos Antivirais/imunologia , Argentina/epidemiologia , Dengue/epidemiologia , Dengue/virologia , Surtos de Doenças , Ensaio de Imunoadsorção Enzimática , Flavivirus/isolamento & purificação , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Vacina contra Febre Amarela , Febre Amarela/sangueRESUMO
En 1998, ocurrió una epidemia de dengue (serotipo 2) en la provincia de Salta, Norte de Argentina, después de la primera detección de dengue en esa zona en 1997. En este trabajo se clasificaron las respuestas serológicas de los casos ocurridos en 1998 como primarios o secundarios, dado que riesgo de la enfermadad severa es mayor en los casos secundarios. Se estudiaron 154 casos por las pruebas de neutralización (NT) e inhibición de la hemoaglutinación. Se clasificaron 38 casos ( 25 porciento) como respuestas primarias y 84 casos (54 porciento) como respuestas secundarias. Los restantes 32 casos (21 porciento) con títulos de IgG en el límite no pudieron ser clasificados. Se analizó la exposición previa a otros flavivirus (Encefalitis de San Luis [SLE] y Fiebre Amarilla [YF]) que pueden cruzar serológicamente, como posible causa de los patrones secundarios. Nuestros resultados indican que el 83 porciento de los casos clasificados como respuesta a dengue secundaria, podrían atribuirse a exposiciones previas a los virus SLE o YF, o a reacciones serológicas cruzadas. La vacunación contra YF fue un factor menor contribuyente al patrón de respuesta secundaria encontrado. El hallazgo de serología positiva para YF en personas que no reconocen vacunación previa debe alertar acerca de la posible circulación silenciosa del virus de la YF, en una área que puede soportar tantos ciclos urbanos como selváticos. Otros casos que mostraron respuesta secundarias permanecen sin explicación, surgirindo la ocurrencia de infecciones previas por otros serotipos de dengue o por otro flavivirus distintos a SLE o YF. (AU)
Assuntos
Humanos , Febre Amarela/imunologia , Encefalite de St. Louis/imunologia , Anticorpos Antivirais/sangue , Dengue/imunologia , Vírus da Dengue/imunologia , Vacina contra Febre Amarela , Flavivirus/isolamento & purificação , Anticorpos Antivirais/imunologia , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Febre Amarela/sangue , Argentina/epidemiologia , Surtos de Doenças , Ensaio de Imunoadsorção Enzimática , Dengue/epidemiologia , Dengue/virologiaRESUMO
Serological studies were carried out using the haemagglutination inhibition and neutralization tests so as to know the circulation dynamics of some arboviruses with the use of Western and Eastern equine encephalitis antigens and St Louis encephalitis antigens in human serum from sound and symptomatic individuals, as well as from sentinel birds, between 1987 and 1991, and during 1994. 1.7% of the asymptomatic subjects tested presented neutralizing antibodies to to Eastern equine and 4.8% to St Louis encephalitis. 16 patients with seroconversion by haemagglutination inhibition to St Louis virus were detected. Surveillance of sentinel birds showed that during 1988, 1989, and 1994. St. Louis circulated in the municipalities of Morón, Bolivia and Chambas; whereas in the latter the Eastern equine encephalitis circulated in 1988 and 1989. Antibodies to Western equine encephalitis were detected in sound individuals by haemagglutination inhibition due seemingly to heterologous antibodies, since there were no neutralizing antibodies against this virus.
Assuntos
Anticorpos Antivirais/sangue , Vírus da Encefalite Equina do Leste/imunologia , Vírus da Encefalite Equina do Oeste/imunologia , Encefalite de St. Louis/imunologia , Humanos , Vigilância de Evento SentinelaRESUMO
The authors studied for two years the role of the chicks of aquatic birds in the arboviral cycles in coastal lagoons in central Panama in order to determine the relation between Culex (Melanoconion) ocossa and Mansonia (Mansonia) dyari mosquitoes in the transmission and dissemination of the viruses of Saint Louis Encephalitis (SLE) and Venezuelan Equine Encephalitis (VEE). Mosquitoes were captured every fifteen days on two consecutive nights to isolate the virus, using light traps (CDC) and baited traps. The attempts to isolate the virus were made using Vero cell cultures and the determination of antibodies was performed. The results of the serologic tests seem to indicate that four bird species: the ex (?) heron (Bubulcus ibis), the American heron (Casmerodius albus), the spoon-billed duck (Cochlearius cochlearius) and the needle crow (Anhinga anhinga) could function as intermediate hosts in the transmission cycle of SLE. Two species, the ibis (Endocimus albus) and the spoon-billed duck (Cochlearius cochlearius) could also be intermediate hosts of VEE in the coastal lagoons of Panama. The presence of antibodies in chicks could indicate an infection acquired recently, after their birth, in this area. The VEE virus was recovered from blood filled mosquitoes which had fed on a spoon-billed duck probably infected and exposed in a Trinidad #10 trap. No SLE virus was isolated. Other unknown viruses were isolated from mosquitoes selected for these studies, such as C. ocossa and M. dyari. The results obtained with these studies indicate the need for more studies utilizing new field techniques in order to establish a link between SLE and VEE, the vector mosquitoes and the aquatic birds in the coastal lagoons of the area under investigation.
Assuntos
Aves/imunologia , Culicidae/microbiologia , Vetores de Doenças , Vírus da Encefalite de St. Louis/isolamento & purificação , Vírus da Encefalite Equina Venezuelana/isolamento & purificação , Encefalite de St. Louis/transmissão , Encefalomielite Equina Venezuelana/transmissão , Insetos Vetores/microbiologia , Animais , Anticorpos Antivirais/sangue , Vírus da Encefalite de St. Louis/imunologia , Vírus da Encefalite Equina Venezuelana/imunologia , Encefalite de St. Louis/imunologia , Encefalite de St. Louis/microbiologia , Encefalomielite Equina Venezuelana/imunologia , Encefalomielite Equina Venezuelana/microbiologia , Comportamento de Nidação , PanamáRESUMO
The authors studied for two years the role of the chicks of aquatic birds in the arboviral cycles in coastal lagoons in central Panama in order to determine the relation between Culex (Melanoconion) ocossa and Mansonia (Mansonia) dyari mosquitoes in the transmission and dissemination of the viruses of Saint Louis Encephalitis (SLE) and Venezuelan Equine Encephalitis (VEE). Mosquitoes were captured every fifteen days on two consecutive nights to isolate the virus, using light traps (CDC) and baited traps. The attempts to isolate the virus were made using Vero cell cultures and the determination of antibodies was performed. The results of the serologic tests seem to indicate that four bird species: the ex (?) heron (Bubulcus ibis), the American heron (Casmerodius albus), the spoon-billed duck (Cochlearius cochlearius) and the needle crow (Anhinga anhinga) could function as intermediate hosts in the transmission cycle of SLE. Two species, the ibis (Endocimus albus) and the spoon-billed duck (Cochlearius cochlearius) could also be intermediate hosts of VEE in the coastal lagoons of Panama. The presence of antibodies in chicks could indicate an infection acquired recently, after their birth, in this area. The VEE virus was recovered from blood filled mosquitoes which had fed on a spoon-billed duck probably infected and exposed in a Trinidad #10 trap. No SLE virus was isolated. Other unknown viruses were isolated from mosquitoes selected for these studies, such as C. ocossa and M. dyari. The results obtained with these studies indicate the need for more studies utilizing new field techniques in order to establish a link between SLE and VEE, the vector mosquitoes and the aquatic birds in the coastal lagoons of the area under investigation