Identification of Brazilian flaviviruses by a simplified reverse transcription-polymerase chain reaction method using Flavivirus universal primers.

We report a simplified reverse transcription-polymerase chain reaction (RT-PCR) method for identification of Brazilian flaviviruses based on the patterns of electrophoretic separation of the amplicons. The RT-PCR was done on the culture fluids of Aedes albopictus C6/36 cells infected with Brazilian flaviviruses, without previous extraction of viral RNA, using Flavivirus universal primers that anneal to highly conserved sequences within the nonstructural protein 5 and 3'- non translated region of the virus genome. Genomes of 13 Brazilian Flavivirus isolates were amplified. It was not possible to amplify the genome of Bussuquara virus. Analysis of the RT-PCR products gave reproducible results and three distinct amplicon patterns were observed. Cacipacoré (800-850 basepairs [bp]) and yellow fever viruses (600 bp) yielded a single amplicon; dengue virus types 1 and 2 (650 and 550 bp), dengue virus type 4 (550 and 450 bp), Iguape (650-600 bp and 750-700 bp), St. Louis encephalitis (700 and 650-600 bp), and Rocio viruses (600 and 500-550 bp) yielded two amplicons; and Ilheus virus yielded five amplicons, two larger than 1,000 bp, one 650-700 bp, one 550-600 bp, and one 450-500 bp. The analysis of amplicon DNA sequences of six viruses showed homology with the 3'- nontranslated region of Flavivirus genome. The use of the Flavivirus universal primers in this simple RT-PCR technique is suitable as a screening test for the genus Flavivirus, with the exception of Bussuquara virus, in Brazilian isolates in tissue culture fluid.

Human disease caused by an arbovirus closely related to Ilheus virus: report of five cases.

We report five cases of human disease caused by arbovirus in 5 patients from the State of São Paulo, Brazil, residing in the municipalities of Osasco, Atibaia, Guarujá, and the capital São Paulo, respectively. One of the patients resides in São Luis, capital of the State of Maranhão. The sites of infection probably were the states of Paraná and Goiás, both in cave regions, the State of Amazonas, and Rondônia in two cases. Laboratory tests for malaria were negative and 1 patient showed a positive serum reaction for leptospirosis. Serum samples from the acute and convalescent phases were tested by hemagglutination inhibition, complement fixation, and neutralization in mice. Acute phase samples were inoculated into suckling mice by the intracerebral route. A close antigenic relationship was observed between the five agents isolated and the flavivirus Ilheus. Serologic tests demonstrated the absence of antibodies in all samples from the 5 patients during convalescence and even for more than 1 year after infection in 1 of them.

New arenavirus isolated in Brazil.

A new arenavirus, called Sabiá, was isolated in Brazil from a fatal case of haemorrhagic fever initially thought to be yellow fever. Antigenic and molecular characterisation indicated that Sabiá virus is a new member of the Tacaribe complex. A laboratory technician working with the agent was also infected and developed a prolonged, non-fatal influenza-like illness. Sabiá virus is yet another arenavirus causing human disease in South America.

Iguape: a newly recognized flavivirus from São Paulo State, Brazil.

A new virus, SP An 71686, was isolated from sentinel mice exposed in a forest area in Iguape county, São Paulo state, Brazil, in 1979. The results suggest [hemagglutination inhibition (HI), complement fixation, neutralization, and ELISA] that SP An 71686 virus is a new arbovirus and that it demonstrates some cross-reactivity with other members of the family Flaviviridae, but can be differentiated from them. Although there is an intensive circulation of several arboviruses in the area, the only diagnosed cases of human disease were caused by Rocio virus during and after the epidemic of encephalitis that occurred in 1975-1977, one case of febrile illness by Caraparu virus in 1983, and by subtype IF of Venezuelan equine encephalitis virus in soldiers during jungle survival training in 1990. Wild animals had a prevalence of SP An 71686 HI monotype antibodies: 46% of birds captured in 1990, 40% in 1991 and 19.5% in 1992. These results suggested that wild birds may play a role in the virus transmission cycle. Mammals (rodents and marsupials) must also be considered potential hosts. However, the virus reservoir-vector relationships need further studies which would help to clarify the ecology of this virus.

Human fatal yellow fever. Immunohistochemical detection of viral antigens in the liver, kidney and heart.

An immunohistochemical method to detect yellow fever antigen was developed using immune sera from rabbits and hamsters and hyperimmune ascitic fluid from mice. A search for the antigen was carried out in liver, kidney and heart in three fatal cases of yellow fever. In the liver it was present in the cytoplasm of hepatocytes, Councilman bodies and Kupffer cells. Yellow fever antigen was also detected in renal tubular epithelium and in groups of myocardial fibers. These findings suggest that viral replication occurs at sites other than the liver. Since yellow fever shares many features with other haemorrhagic fevers the use of immunohistochemistry can impart a significant improvement in the accuracy of its histopathological diagnosis.