Wild dengue virus types 1, 2 and 3 viremia in rhesus monkeys

Among the flaviviruses, dengue, with its four serotypes, has spread throughout the tropics. The most advanced vaccines developed so far include live attenuated viruses, which have been tested in humans but none has been licensed. Preclinical testing of dengue vaccine candidates is performed initially in mice and in nonhuman primates. In the latter the main criteria used to assay protection are neutralizing antibodies elicited by the vaccine candidate and the magnitude and duration of peripheral viremia upon challenge of previously immunized animals. Towards the identification of wild-type viruses that could be used in challenge experiments a total of 31 rhesus monkeys were inoculated subcutaneously of wild dengue types 1, 2, and 3 viruses. The viremia caused by the different viruses was variable but it was possible to identify dengue viruses useful as challenge strains.

Genetic characterization of dengue virus type 3 isolates in the State of Rio de Janeiro, 2001

The genetic characterization of dengue virus type 3 (DEN-3) strains isolated from autochthonous cases in the State of Rio de Janeiro, Brazil, in 2001 is presented. Restriction site-specific (RSS)-PCR performed on 22 strains classified the Brazilian DEN-3 viruses as subtype C, a subtype that contains viruses from Sri Lanka, India, Africa and recent isolates from Central America. Nucleic acid sequencing (positions 278 to 2550) of one DEN-3 strain confirmed the origin of these strains, since genotype III - classified by sequencing - and RSS-PCR subtype C are correlated. This genetic subtype has been associated with hemorrhagic dengue epidemics and the information provided here could be useful to implement appropriate prevention and control measures

Dengue virus infection of the central nervous system (CNS): a case report from Brazil.

Dengue infection that is accompanied by unusual complications has been described in Brazil. We report on the presence of dengue virus in the central nervous system (CNS) of a patient who died in 1998 in Rio Grande do Norte, northeast Brazil. DEN-2 viruses were isolated from the brain liver, and lymphnode tissue of a 67-year-old man whose signs and symptoms were those of dengue infection and a secondary immune response. A postmortem revealed nose bleeds a liver that was brownish with yellow areas, and pulmonary and cerebrae congestion. Immunoperoxidase staining showed a dengue antigen-specific positive reaction in the gray matter cells of the cerebrall cortex; a granular citoplasmatic reaction was seen in the neurons. Dengue infection should always be considered as a cause encephalitis in tropical countries, especially in those where the disease is endemic.

Retrospective study on dengue in Fortaleza, State of Ceará, Brazil

A retrospective serologic study was carried out in Fortaleza, State of Ceará, Brazil, in order to detect the dengue virus activity before recognizing the epidemic of 1994. Mac-Elisa was performed by using a mixture of specific DEN-1 and DEN-2 antigens on serum samples from the Emilio Ribas Laboratory collection. Samples were obtained from 1,224 patients with exanthematic febrile disease and negative serological results for rubella. All specimens were taken during November 1993 to May 1994. The results confirmed dengue infections in Fortaleza by November 1993, approximately six months before the beginning of the epidemic, proving how misleading diagnosis of dengue infection are still troublesome, in spite of the strong dengue activity in Ceará. The authors stress the urgent necessity to implement the active surveillance system in order to prevent another extensive fever epidemics in the state. Epidemiological background of the dengue activity in the State of Ceará is also described.

Human antibodies to dengue and yellow fever do not react in diagnostic assays for hepatitis C virus

Hepatitis C virus (HCV) is a recently described causative agent of the great majority of post-transfusion non A-non B hepatitis and is classified within the Flaviviridae family. Due to a high prevalence of anti-HCV and other flaviviruses circulating in Brazil, such as dengue and yellow fever, we investigated the possibility of serological cross-reactivity between these viruses. Different panels of human sera positive for dengue type 1 (9 cases) and type 2 (7 cases) from 6 patients naturally infected with yellow fever and from 94 adults vaccinated against the 17D strain of yellow fever were tested against HCV antigens used in diagnostic assays. Two enzyme immunoassay systems were tested: one, an in-house test using recombinant antigens from core, NS3 and NS5 regions of the HCV genome (Research Foundation for Microbial Disease of Osaka University, Japan); and another, using synthetic peptides representing immunodominant epitopes of structural core and non-structural NS4 and NS5 HCV regions (INNOTEST HCV Ab, Innogenetics, Belgium). A line immunoassay (INNO-LIA HCV Ab, Innogenetics, Belgium) was used as a confirmatory test. In this, HCV antigens are coated as discrete lines on a nylon strip with plastic backing. Besides 4 control lines on each strip, a total of 6 HCV lines are present: line A consists of several NS4 epitopes, line B consists of several NS5 epitopes and lines C-F contain several core epitopes. This test not only confirms but differentiates antibodies to hepatitis C virus. No positive results were detected with these tests, indicating that hepatitis C infection can be evaluated by current assays in regions where flaviviruses are endemic