Histological and ultrastructural alterations in lung tissue of BALB/c mice infected with dengue virus serotype 2 (non-neuroadapted), by intraperitoneal and intravenous routes were analyzed. Lung tissues were processed following the standard techniques for photonic and electron transmission microscopies. Histopathological and ultrastructural studies showed interstitial pneumonia, characterized by the presence of mononuclear cells. In the mouse model, the dengue virus serotype 2 seems to led to a transient inflammatory process without extensive damage to the interalveolar septa, but caused focal alterations of the blood-exchange barrier. Endothelial cells of blood capillaries exhibited phyllopodia suggesting activation by presence of dengue virus. Morphometrical analysis of mast cells showed an expressive increase of the number of these cells in peribronchiolar spaces and adjacent areas to the interalveolar septa. Alveolar macrophages showed particles dengue virus-like inside rough endoplasmic reticulum and Golgi complex, suggesting viral replication. The tissue alterations observed in our experimental model were similar to the observed in human cases of dengue fever and dengue hemorrhagic fever. Our results show that BALB/c mice are permissive host for dengue virus serotype 2 replication and therefore provides an useful model to study of morphological aspects of dengue virus infection.

Dengue virus replication in mosquito cell cultures was observed by electron microscopy in one fatal and 40 classical isolates from a dengue type 2 outbreak in Rio de Janeiro and compared with the prototype New Guinea C strain. All the Brazilian isolates presented, beside the classical structured dengue virus particles, fuzzy coated virus-like particles, never observed in thereferencial New Guinea C virus strain. more numerous DEN-2 virus particles, fuzzy coated virus-like particles, defective virus particles and smooth membrane structures inside the rough endoplasmic reticulum characterized the unique fatal isolate examined.

Uma epidemia de dengue iniciou-se em março de 1986, no Rio de Janeiro, alcançando rapidamente outras partes do país. Febre dengue clássica foi observada, porém o vírus do dengue foi isolado de um caso fatal. As amostras de dengue 1 isoladas de pacientes e de fêmeas adultas de Aedes aegypti capturadas na área apresentaram efeito citopático na linhagem de células A. albopictus clone C6/36. A lesão celular foi estudada também em microscopia eletrônica, sendo descritos os dados observados. Um teste de captura para IgM (MAC-ELISA) foi utilizado durante a epidemia tanto para o diagnóstico como para avaliarr a circulação de vírus, com resultados claros e reprodutíveis; os anticorpos IgM apareceram precocemente após o início da doença clínica, permanecendo por cerca de 90 dias na maioria dos pacientes. A reação mostrou-se tipo específico em cerca de 50% dos pacientes, porém, um alto nível de respostas heterológas para dengue tipo 3 foi observado nos demais pacientes. Observou-se uma taxa total de isolamento de 46,8% (813 amostras de vírus de 1734 pacientes). Com a reação de IgM houve um momento de casos confirmados: 1479, em 2541 casos suspeitos (58,2%). A possível influência dos anticorpos dos pacientes sobre a taxa de isolamento de vírus é discutida, porém a questão não está esclarecida completamente. Os autores enfatizam a importância do diagnóstico laboratorial dos casos suspeitos de dengue em todas as regiões do país, onde os vetores são encontrados.

A dengue outbreak started in March, 1986 in Rio de Janeiro and spread very rapidly to other parts of the country. The great majority of cases presented classical dengue fever but there was one fatal case, confirmed by virus isolation. Dengue type 1 strains were isolated from patients and vectors (Aedes aegypti) in the area by cultivation in A. albopictus C6/36 cell line. The cytopathic effect (CPE) was studied by electron microscopy. An IgM capture test (MAC-ELISA) was applied with clear and reproducible results for diagnosis and evaluation of virus circulation; IgM antibodies appeared soon after start of clinical disease, and persisted for about 90 days in most patients. The test was type-specific in about 50% of the patients but high levels of heterologous response for type 3 were observed. An overall isolation rate of 46,8% (813 virus strains out of 1734 specimens) was recorded. The IgM test increased the number of confirmed cases to 58,2% (1479 out of 2451 suspected cases). The importance of laboratory diagnosis in all regions where the vectors are present is emphasized.